WO2017046423A1

WO2017046423A1 - A 3d display and method of operation thereof

Info

Publication number: WO2017046423A1
Application number: PCT/EP2016/072208
Authority: WO
Inventors: Olivier Charlier
Original assignee: Barco N.V.
Priority date: 2015-09-18
Filing date: 2016-09-19
Publication date: 2017-03-23

Abstract

Systems and devices are described for moving pictures with some 3D effect, a method and an arrangement for producing moving pictures with some level of three dimensional effect when viewed by at least some viewers. An advantage of some embodiments of the present invention is that such images can be seen in 3D without wearing glasses, or any other device. Embodiments of the present invention solve the problem caused by generating 3D images with the viewer wearing glasses. Embodiments of the present invention can provide 3D images without discontinuities.

Description

A 3D DISPLAY AND METHOD OF OPERATION THEREOF

The present invention relates to a 3D display arrangement and a method of operation thereof, an optical device and a method of operating thereof, as well as software for carrying out such methods. The present invention also relates to moving pictures adapted for 3D image production. The images may be viewed in a cinema or at home for example.

Methods of Producing 3-D Illusion in Moving Pictures Motion pictures have traditionally been images in 2-dimensions. However, several methods have been developed for providing the illusion of depth in motion pictures. These include the Anaglyph, IMAX (Polaroid), autostereoscopy and Pulfrich 3- dimensional illusions.

Solutions have been implemented to allow the anaglyphic methods to be implemented with a single projector.

These methods all require filters placed between the eyes of the viewer and the screen on which the Moving Pictures are displayed. These filters are usually mounted on glasses that the viewer wears while watching the moving pictures. Examples of such glasses are given in US 8941919 B2 "Continuous adjustable 3D filter spectacles for optimized 3Deeps stereoscopic viewing, control method and means therefor, and system and method of generating and displaying a modified video", US 20100066813 "STEREO PROJECTION WITH INTERFERENCE FILTERS", US 8947512 B 1 "User wearable viewing devices".

In single projector settings; the use of filters leads to a reduced brightness perceived by the viewers. Autostereoscopy refers to the representation of stereoscopic images without the use of glasses, also referred to as glassless or glass free 3D, for rendering the three-dimensional effect, using a combination of both stereo parallax and movement parallax. To implement it on a flat panel display, parallax barriers or lenticular lenses are used in combination with the flat panel. However, it leads to a reduced image resolution and only works for certain positions of the user with respect to the display. A different image is seen through each eye, therefore rendering the three dimensional illusion. Autosteroscopy is mainly used for scientific and medical 3D visualisation, and computer games or advertising. However, auto stereo scopy has no application in cinema due to the required positions by the viewer.

An immersive theater is described in US 5,963,247 "Visual display systems and a system for producing recordings for visualization thereon and methods therefor". A central screen is flanked by a first screen on its left and a second screen on its right thereby immersing the viewers in the theatrical experience as illustrated in Figures 15a and 24.

In such an immersive theater, the glasses used for 3D performances can obstruct at least part of the lateral field of view or create a discontinuity that can reduce the comfort of the experience of the viewers. Viewers on opposite sides of the projection room also see the lateral screens from largely different angles. If two viewers seated at opposite sides of the projection room look at the same 3D images projected on a lateral screen, at least one of them will see a wrong perspective thereby ruining the immersive experience that the immersive theater is supposed to enable. Some viewers have a poor 3D sight and/or get headaches while watching 3D movies for more than a few minutes at a time. Those viewers do not enjoy motion pictures in stereoscopic projection. Going to the movie often being a social activity, viewers averse to 3D movies can be a disincentive for an entire group to see movies in 3D thereby affecting the return on investment expected from the 3D movie producers.

The Pulfrich effect is generally induced by placing a dark filter over one eye. The phenomenon is named after the German physicist Carl Pulfrich, who first described it in 1922. The effect has been exploited as the basis for some television, film, and game 3D presentations.

If a camera starts at position X and moves right to position Y, and a viewer watches this segment with a dark lens over the left eye, then when the right eye sees the image recorded when the camera is at Y, the effect of the lower light intensity entering the left eye means that the left eye will react a few milliseconds behind the right eye. This means that the image seen by the left eye will be of an image recorded at X, thus creating the necessary parallax to generate right and left eye views and 3D perception, much the same as when still pictures are generated by shifting a single camera. One advantage of this system is that people not wearing the glasses will see a perfectly normal picture.

Barco Escape™ makes use of three large screens at the front and to the left and right in a cinema. Such screens produce not a narrow beam of light and it can be expected that a distributed light is generated that can be seen by the eye closest to the screen not only in peripheral vision but perhaps also in the central visual area. Also the image projected is a video image and not a static light. One can expect that some light can even enter the eye furthest away from the side screen.

It has not been mentioned that the Pulfrich effect will take place when three such screens are used. It has been reported that one can use a low intensity light source, such as a flashlight, to add light to one eye rather than filtering one eye to induce the Pulfricht effect. Using a flash light puts a narrow beam of light into one eye.

The use of filters is therefore not required. The art remains nevertheless silent on how the flashlight should be positioned in order (a) not to obstruct the field of view and (b) to illuminate a single eye of each viewer. Also, such a flashlight tends to dazzle the viewer.

The art also remain silent on (c) how to make it possible for viewers in the same projection room, at the same time and watching to the same screen to choose whether or not they want to experience the motion picture in 2D or 3D version of a film without impact on e.g. the brightness of images being projected with (d) a minimum of modification to the existing projection hardware. In addition, in a Barco Escape set-up, the art remain silent on how to avoid perspective mismatch, in particular for stereoscopic images projected on the lateral screens for which there are not only sweet spots where the 3D effect will be most convincing but also spots where the 3D effect will be incorrect and will ruin the cinematic experience. What is needed is a solution that solves all of the issues listed above. There is room for improvement in the art. Summary of the invention.

An object of embodiments of the present invention is to provide systems and devices for moving pictures with some 3D effect, and an arrangement for producing moving pictures with some level of three dimensional effects when viewed by at least some viewers. An advantage of some embodiments of the present invention is that such images can be seen in 3D without wearing filter or shutter glasses.

Embodiments of the present invention solve the problem caused by generating 3D images with the viewer wearing glasses, and therefore embodiments of the present invention can provide 3D images without discontinuities in the field of view of the viewer. This is achieved with a display system according to embodiments of the present invention comprising at least a first display for displaying images like e.g. a motion picture in front of a viewer, a first means to illuminate the left eye of the viewer and a second means to illuminate the right eye of a viewer wherein the first and second means are controlled by a control unit for inducing inter-eye luminance disparity coupled to the lateral movement of an object on the first display without the use of light absorbing filter in front of either eye of the viewer coupled to the lateral movement of an object on a projection surface.

Inter-eye illumination disparity is induced according to embodiments of the present invention by e.g. activating a light source on the left or on the right of the head of a viewer. The illumination disparity is coupled to the movement of the image of an object on screen, moving with a lateral velocity component (i.e. from left to right or from right to left for a viewer under normal circumstances) so as so as to create 3D images according to the Pulfrich effect. It is an advantage of the invention that no filter has to be positioned in front of the viewer to create a 3D effect. In known 3D projection systems, viewers have to wear glasses which create a boundary between the screen and the viewer (not unlike a mask creates a boundary between a diver and the surrounding underwater environment in which the diver is) and can ruin the immersive experience.

In accordance with embodiments of the present invention, the amount of light reaching an eye of the viewer is at least twice the amount of light reaching the other eye of the viewer to induce inter-eye luminance disparity sufficient to let the viewer perceive 3D effects.

More pronounced 3D effects can be achieved when the amount of light reaching an eye of the viewer is 5 times or more the amount of light reaching the other eye of the viewer.

While discarding filters, the present invention does not exclude the possibility of using dedicated head gear. It is another advantage of embodiments of the present invention that 3D sweet spots and wrong perspective are avoided or mitigated.

Indeed, in the stereoscopic projection system known in the art, the images projected on screen must be watched from a frontal position (i.e. the images are not meant to be seen at an angle). If the images are seen at an angle, the perspective will be wrong, thereby ruining the cinematic experience of the viewer.

With embodiments of the present invention, if a viewer looks at screen at an angle, the lateral velocity of any image moving on screen will be reduced. The amplitude of the Pulfrich effect being proportional to the lateral velocity of the images being projected, the amplitude of the 3D effect will be reduced when a viewer looks at a screen at an angle. Wrong perspectives are thus mitigated if not entirely eliminated.

In another aspect of the invention, a control unit is provided for activating the light source. It is preferred if the activating is done with a ramp up of the signal so that the change is not sudden in preparation of a 3D scene.

Embodiments of the present invention does not exclude the possibility that some viewers are unable to see the 3D effect. Such viewers, who are not sensitive to three dimensional effects, will experience the motion picture as usual. This is a significant improvement over conventional stereoscopic three dimensional moving pictures which are viewed with glasses which stereoscopic three dimensional movies superpose two images, and which therefore cannot be viewed without wearing the correct glasses. When viewed without filter glasses, the images appear blurred which does not allow viewing the film in optimal conditions without wearing filter glasses.

In a preferred embodiment, the first and second means for activating a light source on the right or on the left of the head of a viewer are controlled by a control unit which receives command signals correlated to the displayed images of the at least one motion picture according to the horizontal moving direction of the at least one object.

This provides the advantage that the illumination of the eyes is automatically controlled and can react fast to any movement occurring in the motion picture.

Preferably, said command signals are not detectable by the viewer, i.e. are invisible to the viewer. Such command signals can be transmitted by at least one of infrared light, or radio frequency wavelengths of light, ultrasound, etc. (including Bluetooth, wifi, ... 3G, 4G, ...)

Such signals provide wireless solutions although the present invention includes in embodiments wired solutions as well, or a combination of both. For example, in another preferred embodiment, said command signals are transmitted with at least one of ultrasonic sound, or infrasonic sound. The signals can be therefore provided to the first and second means for activating a light source through the soundtrack of the motion picture, without disturbing the viewer as these are not audible.

The light source is positioned in a monocular field of view of each of, respectively, the left and right eye. When the light source is positioned in a monocular field of view, it provides the advantage that the first means for increasing the illumination does not disturb the left eye and the second means for increasing the illumination does not disturb the right eye.

In another embodiment, at least one light source is an incandescent source, or a solid state light source.

In another preferred embodiment, the at least one light source is one or more LEDs.

In another embodiment, said light source, e.g. comprising at least one LED, emits at least one of white, red, green, blue light or any combination thereof. An advantage is that light sources, e.g. LEDs of different colors can be light up according to the content and color content of the displayed motion picture thereby making them less conspicuous. Preferably, the at least one light source is positioned in a proximity of respectively the left and right eye.

Advantageously, the at least one light source is positioned adjacent to the lateral cantus, at the level of or below the lateral hooding area of the eye, or at the level of or below the lower eyelid or close to the medial canthus.

In a preferred embodiment, at least one of the display surfaces is a front projection screen. An advantage is that any traditional cinema can be used to provide such an arrangement of display screens.

Preferably, the display surfaces for displaying moving pictures comprise at least one of an LCD, an LED, a projection screen, an LED wall, a CRT or a plasma fixed format display.

Advantageously, the arrangement is installed within a cinema, a theatre, an opera, a conference room, a concert hall, in a room or an outdoor cinema at night.

A second object of embodiments of the present invention is to provide a device for assisting the visualization of some three dimensional effects in moving pictures without disturbing the field of view and without dazzling the viewer.

Embodiments of the present invention also provide a device for viewing three- dimensional effects in at least one motion picture displayed on at least one display surface, the device comprising first means for increasing the amount of light entering the right eye of a viewer compared to the amount of light entering the left eye dependent upon a horizontal movement of an object on the at least one display surface, second means for increasing for increasing the amount of light entering the left eye of a viewer compared to the amount of light entering the right eye (optionally, without reducing the illumination entering the right eye) dependent upon horizontal movement of an object on the display , (optionally when at least one object in images displayed on the third display surface is moving generally in a horizontal direction from left to right from the viewer' s point of view, or vice versa), and a control unit for for controlling the amount of light emitted by the first and means so as to create 3D images according to the Pulfrich effect by inducing inter-eye luminance disparity. It is preferred if the switching is done with a ramp up of the signal so that the change is not sudden in preparation of a 3D scene. Which of the first and second means for increasing the amount of light entering the eye of the viewer are employed depends on whether the object with the horizontal movement is to be pushed back and should appear further away from the viewer or whether the object should appear closer to the viewer.

The first and second means for increasing the amount of light entering the left eye and the right eye of the viewer comprise at least one light source.

An advantage associated with the device according to these embodiments of the present invention is that the user may move his head without influencing the three dimensional effects created.

In a preferred embodiment, the command signals are invisible light signals such as infrared signals, and the control unit comprises therefore an infrared detector.

In another embodiment, the command signals are signals at radio frequency wavelengths such as provided by Wifi, Bluetooth, 3G, 4G, etc.

In another embodiment, the command signals are sonic signals that cannot be detected by humans such as ultrasonic or infrasonic sound and can be emitted in parallel to the audio soundtrack of the moving pictures. However, the viewer doesn't hear the command signals. In this embodiment, the control unit comprises an ultrasound or infrasound detector accordingly.

In a preferred embodiment, the first and second means for increasing the amount of light entering the right eye and the left eye of the viewer are to be positioned in a monocular field of view of the left and/or right eye such that the means for increasing the illumination of the left eye do not disturb the right eye and inversely.

It is an advantage of this further aspect of the invention that the device does not interfere with the field of view of the binocular vision, which increases strongly the comfort and the image quality provided by the device.

In a another aspect of the invention, an apparatus to induce the Pulfrich effect comprises at least one source of light with a light exit and a support structure to maintain the source of light in a position relative to the head of a viewer; wherein the light exit of the source of light is positioned close to one eye of the viewer so as to illuminate said one eye. In an aspect of the present invention, the control unit is configured to be attached by fixing means or is mounted to said support structure.

It is an advantage of this aspect of the invention that the Pulfrich effect can be induced at will regardless of the position of the head of the viewer.

In a further aspect of the invention, the light exit is positioned adjacent to the lateral cantus of the at least one eye and at the level of or below the lateral hooding area of that eye.

It is an advantage of this aspect of the invention that it will disturb the viewer as little as possible while allowing an adequate illumination of the eye on the same side of the head as the light exit. It is a further advantage of this aspect of the invention that when the light exiting the light exit has a color similar to a color of the visual environment of the viewer, the disturbance to the viewer will be even more reduced.

Alternatively, the light exit is positioned at the level of or below the lower eyelid.

Alternatively, the light exit is positioned close to the medial canthus.

In all such cases, it is an advantage if the position of the light exit is such that it is blocked by the root and dorsum of the nose and does not reach the other eye. In another aspect of the invention, the support structure also maintains a louver close to the root and/or dorsum of the nose to shield each eye of the viewer from stray light. The louver shields thus the left eye from light coming from the right of the viewer and the louver shields the right eye from light coming from the left side of the viewer.

It is an advantage of this aspect of the invention that by reducing the amount of stray light reaching the other eye, the Pulfrich effect will be more pronounced.

In another aspect of the invention, the support structure may take the form of a tiara, hard headband, cloth headband, plastic headband, wherein the headband goes over or behind the head, headphones, earphones, glasses, goggles, security glasses, hat, helmet, head accessory, or any type of hair accessory.

In a further aspect of the invention, the apparatus comprises a receiver to receive command signals and control electronics to activate the source of light and illuminate the corresponding eye of the viewer at a well determined moment e.g. in order the induce the Pulfrich effect at one or more time during a motion picture.

In a further aspect, a mobile phone is used to receive the command signals and control the activation of the at least one source of light.

In a further aspect of the invention, the apparatus has a source of light with a light exit for each eye of the viewer.

In a further aspect of the invention, the apparatus is used in conjunction with a Barco Escape™ projection system comprising a first and second lateral screens and a third main screen .

When used with a Barco Escape™ projection system, the light source collects light emitted by one of the lateral screens. The light can be collected by a light funnel, whether hollow or full. The advantage of that aspect of the invention is that the apparatus does not have to be powered. Furthermore, no electronics is required to activate the light source at the opportune moment when the viewer looks at a motion picture. A reflecting surface fastened to the support structure of the apparatus can be positioned adjacent to the root and dorsum of the nose to reflect light into the eye. The reflecting surface can be used alone or in conjunction with a light funnel. The reflecting surface can be an integral part of a louver on the dorsum of the nose of the viewer.

Alternatively, the apparatus is powered and command signals are transmitted by light projected on the lateral screens. (For instance: right left light imbalance + photosensor).

The light projected can be infra-red light projected by one of the projectors or by a dedicated infra-red projector. In a further aspect of the invention, the apparatus is used in conjunction with an emissive display. The present invention also includes a sensor to evaluate dark adaptation / light adaptation locally.

In accordance with another aspect, when used with a Barco Escape projection system, a light source on a head mounted device collects light emitted by one of the lateral screens. The light can be collected by a light funnel, whether hollow or full. The advantage of that aspect of the invention is that the apparatus does not have to be powered. Furthermore, no electronics is required to activate the light source at the opportune moment when the viewer looks at a motion picture. A reflecting surface fastened to the support structure of the apparatus can be positioned adjacent to the root and dorsum of the nose to reflect light into the eye. The reflecting surface can be used alone or in conjunction with a light funnel. The reflecting surface can be an integral part of a louver on the dorsum of the nose of the viewer. Alternatively, the head mounted device is powered and command signals are transmitted by light projected on the lateral screens. (For instance: right left light imbalance + photosensor). The light projected can be infra-red light projected by one of the projectors or by a dedicated infra-red projector. In a further aspect of the invention, the device is used in conjunction with an emissive display.

In a further aspect of the present invention, the color of the at least one light source is selected to match a color of the images projected on the first and/or second lateral screens. In a further aspect of the present invention, the control unit further comprises means to control the intensity of the illumination provided by the means for increasing the light entering an eye as a function of the ambient light provided by the sensor.

It is another object of the present invention to provide an arrangement of a display surface having a first part and a second part, said first part being configured to be in the binocular field of view of a viewer and at least a portion of said second part being configured to be in the monocular field of view of the second eye of the viewer, said second eye being the left or the right eye, said first eye being the right or left eye, the arrangement comprising means for displaying a first sequence of images in the first part of the display surface, said first sequence of images showing at least one picture element of the first sequence of images at some time in movement wherein the movement has at least a non-zero horizontal component, comprised in the visual plane and parallel to the pupil line of the viewer,

means for displaying a second sequence of images in at least the portion of the second part of the display surface simultaneously with the first sequence,

wherein the arrangement is further adapted to display the first and second sequence of images such that the intensity of at least a portion of at least some images of the first or second sequence emitted from the first or second part respectively is such that a ratio of illumination leaving the display surface for entering the second eye of the viewer compared to the first eye is at least of two.

Advantages of embodiments of the present invention are to solve the problem of generating three dimensional images without complex glasses which include filters. Thus, it is the content of the displayed images which matters to generate the three dimensional effect and no special hardware is required. Also, only one image is displayed, unlike 3D as known in the art which requires the superposition of 2 images, one for the left eye and one for the right eye. Further advantages of the present invention are that the impression of 3D can be generated in a natural way to the viewer, by adapting the content of the images to generate a ratio of illumination between the first and second part of the display surface.

In a preferred embodiment according to the present invention, a louver configured to be positioned on the dorsum of a viewer's nose is provided so as to increase the monocular field of view of each eye of the viewer. This can be provided in a simple and economic way.

A louver positioned on a viewer's nose increases the 3D effects generated by the Pulfrich effect as it increases the monocular field of view.

Preferably, the ratio of illumination between the second and first eye is preferably at least 5, more preferably at least 9 or at least 10. Increasing the ratio of illumination increases even more the impression of 3D generated by the Pulfrich effect.

Advantageously, the arrangement does not comprise viewer glasses, i.e. glasses with polarization filters or with color filters. In a preferred embodiment, the means for adjusting the brightness of at least a portion of each image of the second sequence comprises a controller configured to read calibration data. Adjusting brightness is easy to control.

In a preferred embodiment according to the present invention, the calibration data is provided by test-subjects or a photo sensor device configured to measure inter-eye luminance disparity, said photo sensor device comprising at least two photodiodes separated by a distance which is substantially the average human inter eye distance. The ability to measure intereye disparity by means of a simple device allows any display system to be calibrated easily and economically.

Additional advantages of the present invention are further provided by the photo sensor device provided in the display zone which is configured to measure the illumination ratio between a left and right photodiode so as to calibrate the system and adapt the first and/or second sequence of images so as to achieve the desired Pulfrich effect. Test subjects in the display zone may also advantageously provide a quantitative parameter to further calibrate the intensity of the images of the first and/or second sequence to generate an optimal 3D illusion with the Pulfrich effect.

In an advantageous embodiment of the present invention, the calibration data comprises at least one of a look-up table storing a parameter related to the brightness setting of a projector and the inter eye luminance disparity, meta-data stored within the image data.

Advantageously, the storing of the calibration data in the form of a look up table allows to adapt the settings of the projector or the display as a function of various conditions, such as the inter eye luminance disparity, and thus the ratio of illumination 11/12.

Preferably, the calibration data depends on at least one of a parameter characterizing a sequence of images, a qualitative parameter determined by a test-subject identifying a brightness level, a quantitative parameter computed with a photo sensor device, the surroundings of the arrangement such as the theater, the test subject, the brightness of the first sequence of images and/or the brightness of the second sequence of images, the horizontal speed of the moving object, the distance between the first part of the display surface and a viewer, the distance between the second part of the display surface and a viewer.

Advantageously, said quantitative parameter comprises at least one of the lowest of the two output signals of a photo- sensor device, the maximum value measured by the least illuminated photodiode for the first sequence of images (227), an average or median value of the signal measured by the least illuminated photodiode for the first sequence of images (227), a weighted luminance measured as the product of the maximum luminance achieved on the first part of the display surface when a white field is projected and the average pixel value for that image sequence, a weighted luminance of a sequence of images for a given display system acquired by computing the average pixel value or capturing the readings of a photo-sensor device. In embodiments of the present invention, the adaptation of the intensity of at least a portion of at least some images of the first or second sequence emitted from the first or second part respectively such that a ratio of illumination leaving the display surface for entering the second eye of the viewer compared to the first eye is at least of two is performed during the acquisition of the first and second sequence of images, during film editing, color grading, film production or in real time while displaying the first and second sequence of images.

Advantages of embodiments of the present invention are that intereye illumination disparity can be provided at various stages, such as during shooting of the images, during film editing, or even while displaying. Thus, existing films or films with no intent of 3D can be easily adapted to be displayed with the illusion of 3D thanks to the Pulfrich effect, as long as there is a moving object in a scene, with the movement having one component parallel to the pupil plane. No special camera is required to acquire images for generating the Pulfrich effect.

In another embodiment of the present invention, the adaptation of the intensity of at least a portion of at least some images of the first or second sequence of images in real time is performed by controlling at least one of the brightness setting of the projector, the intensity of at least a portion of the image data of the first and/or second sequence of images, the image data such as the pixel values and/or the color point and/or any other image characteristics which affect inter eye illumination disparity, the image content of the second sequence of images such that most or all bright pixels which are in the monocular field of view of the first eye of the viewer are dimmed.

In a preferred embodiment of the present invention, the inter eye illumination disparity is monitored in real time with at least one of a photo-sensor device such that the displaying of the first and second sequence of images such that the intensity of at least a portion of at least some images of the first or second sequence emitted from the first or second part respectively is such that a ratio of illumination leaving the display surface for entering the second eye of the viewer compared to the first eye is at least of two.

Advantageously, a visual cue and/or audio cue configured to draw the attention of a viewer during the first sequence of images. It has been found that continuous 3D images can be tiring and that occasional 3D sequences for dramatic effect are preferred. Advantages of a visual or audio cue are to direct the attention of the viewer in the right direction so as to make him see the images with an optimized Pulfrich effect.

Preferably, the audio cue is generated by a directional sound system.

Additional advantages are that a directional sound system enhances the 3D effect, the experience of the viewer. In another embodiment, the display surfaces further comprise a third part, said third part being configured to be in the monocular field of view of the first eye of the viewer.

Advantageously, the louver is incorporated in opera binoculars, in a mask, in glasses.

In embodiments of the present invention, the display surface is at least one of an LCD, an LED, a projection screen, a back projection screen, an LED wall, a CRT or a plasma fixed format display.

The present invention also pertains to a method for displaying on a display surface having a first part and a second part, wherein said first part is configured to be in the binocular field of view of a viewer and at least a portion of said second part is configured to be in the monocular field of view the second eye of the viewer, said second eye being the left or the right eye, said first eye being the right or left eye, the method comprising the steps of displaying a first sequence of images in the first part of the display surface, said first sequence of images showing at least one picture element of the first sequence of images at some time in movement wherein the movement has at least a nonzero horizontal component comprised in the visual plane and parallel to the pupil line of the viewer,

displaying a second sequence of images in at least the portion of the second part of the display surface simultaneously with the first sequence,

adapting to display the first and second sequence of images such that the intensity of at least a portion of at least some images of the first or second sequence emitted from the first or second part respectively is such that a ratio of illumination leaving the display surface for entering the second eye of the viewer compared to respectively the first eye is at least of two.

Advantageously, the step of adapting to display the first and second sequence of images is performed during the acquisition of the first and second sequence of images, during film editing, color grading, film production or in real time while displaying the first and second sequence of images Embodiments of the present invention also pertain to a photo- sensor device configured to measure a ratio of illumination, said photo sensor device comprising at least two photodiodes separated by a distance which is substantially the average human inter eye distance.

Advantageously, the photo- sensor is configured to be worn by a viewer. Preferably, the photo- sensor is configured to be placed in a display zone of a display system

In a preferred embodiment, the photo- sensor device is further configured to communicate with a controller for controlling in real time a first and second sequence of images emitted by a first and second part of a display surface. Advantageously, the photo- sensor comprises means to communicate with a controller for adapting the displaying of the first and second sequence of images such that the intensity of at least a portion of at least some images of the first or second sequence emitted from the first or second part respectively is such that a ratio of illumination leaving the display surface for entering the second eye of the viewer compared to the first eye is at least of two.

The present invention also pertains to a method for calibrating an arrangement as described above with a photo- sensor device described above and comprising means for measuring a ratio of illumination between a left and right eye with a left and right photodiode, the method comprising the steps of measuring with a photosensor device a ratio of illumination between a left and right photodiode,

adapting the displaying of a first and second sequence of images such that the intensity of at least a portion of at least some images of the first or second sequence emitted from the first or second part respectively is such that a ratio of illumination leaving the display surface for entering the second eye of the viewer compared to the first eye is at least of two according to the measurements of the device.

In a preferred embodiment the method further comprises the step of storing in a look-up- table measurements obtained with a photo- sensor device for various locations in a display zone.

Brief description of the figures. Figure 1 shows the binocular and monocular field of view for an average human being.

Figure 2 is a perspective view of an arrangement of a display for use with embodiments of the present invention, indicating the relative positions of a viewer; the light sources use to induce inter-eye luminance disparity and the display.

Figure 3 is a top view of an arrangement of a display for use with embodiments of the present invention, indicating the relative positions of a viewer; the light sources use to induce inter-eye luminance disparity and the display.

Figure 4a and 4b illustrate a principle of the invention in a first example.

Figure 5a and 5b illustrate a principle of the invention in a second example. Figure 6a and 6b illustrate a principle of the invention in a third example.

Figure 7a and 7b illustrate a principle of the invention in a fourth example.

Figure 8a, 8b and 8c illustrate the concept of velocity for an image moving across a display.

Figure 9a and 9b illustrate the geometric construction to evaluate the perceived position of an object when the Pulfrich effect is induced.

Figure 10 shows the preferred positions for light sources according to embodiments of the present invention.

Figure 11 is a headset for viewing three dimensional effects according to an embodiment of the present invention Figure 12 shows a perspective view of a headset according to embodiments of the present invention worn by a viewer.

Figure 13 illustrates one snapshot of a video sequence used to evaluate devices for viewing three dimensional effects according to embodiments of the present invention.

Figure 14 shows the geometrical construction illustrating what happens when the velocity of objects moving on the screen exceeds a critical limit.

Figure 15a, b, c and d show how the proposed embodiments of the present invention addresses the problems of 3D in an Escape™ display system.

Figure 16 is a device for viewing three dimensional effects according to an embodiment of the present invention. Figure 17 is an arrangement of a main projection screen and a lateral projection screen for use with embodiments of the present invention, wherein the main projection screen is in a binocular field of view of a viewer, and the lateral projection screen is in a monocular field of view.

Figure 18 is schematic top view of an arrangement of two screens for use with embodiments of the present invention, indicating the orientation and the distances of the screens and a main viewer.

Figure 19 is a main screen displaying a motion picture of a merry go round

Figure 20 shows a device for measuring inter-eye illumination disparity with two photodiodes according to an embodiment of the present invention.

Figure 20b is a side view of the device shown in Figure 20, further comprising a louver.

Figure 21 shows a schematic representation of an operational amplifier for use in the device according to embodiments of the present invention.

Figure 22a is a schematic top view representation of an arrangement of a front screen and lateral screen, wherein the front screen is in a binocular field of view of a viewer and displays a first sequence of images, and the lateral projection screen is in a monocular field of view of the viewer and displays a second sequence of images.

Figure 22b is a schematic representation of two projector projecting images on two walls meeting at a corner of a room, the projector projecting respectively a first and a second sequence of images simultaneously.

Figure 22c is a perspective view of Figure 22b.

Figure 22d is a representation of a curved display surface used and three projectors projecting images on the curved display surface in rear projection.

Figure 22e shows three front projection screens, comprising a left, central and right screen positioned next to each other as in an Escape display system, a viewer facing the central screen, and a schematic representation of the binocular field of view of the viewer and the left and right monocular field of view, with and without a louver.

Figure 22f shows three front projection screens, comprising a left, central and right screen positioned next to each other as in an Escape display system, a viewer facing the left screen, and a schematic representation of the right monocular field of view, with and without a louver.

Figure 22g shows three front projection screens, comprising a left, central and right screen positioned next to each other as in an Escape display system, a viewer facing the right screen, and a schematic representation of the left monocular field of view, with and without a louver. Figure 22h shows a single planar projection screen used to induce Pulfrich effect, a viewer and a schematic representation of the left monocular field of view of the viewer.

Figure 23 shows a louver according to an embodiment of the present invention worn by a viewer. Figure 24 is a schematic representation of a front projection display comprising three front projection screens and three projectors for use with embodiments of the present invention.

Figure 25 is a schematic representation of the display system of Figure 18 and 19 wherein measurements of the ratio 11/12 at the locations of the crosses performed with a device for measuring inter eye luminance disparity are provided.

Figure 26 is a schematic representation of a display system wherein the lateral screen is a front projection screen and measurements of the ratio 11/12 measured with the device for measuring inter eye luminance disparity is indicated next to the positions marked by a cross "x". Figure 27 represents a black image displayed over the entire display area of a screen, shown in landscape mode.

Figure 28 represents a white image, the negative of Figure 27, displayed over the entire display area of a screen, shown in landscape mode.

Figure 29 is an image which is half black and half white, to be displayed over the entire display area of a screen, shown in landscape mode.

Figure 30 is the negative image of figure 29.

Figure 31 is an image of alternating narrow black and white stripes, to be displayed over the entire display area of a screen, shown in landscape mode.

Figure 32 is the negative image of figure 31. Figure 33 is an image of alternating wide black and white stripes, to be displayed over the entire display area of a screen, shown in landscape mode.

Figure 34 is the negative image of figure 33.

Figure 35 is a checkerboard pattern image wherein the pads are black and white, to be displayed over the entire display area of a screen, shown in landscape mode. Figure 36 is the negative of the checkerboard pattern image of figure 35.

Figure 37 illustrates the velocity vector V of picture element Px in a display surface represented in a Cartesian coordinate system having as horizontal coordinate axis the pupil line of the viewer and as vertical coordinate axis the vertical visual axis

perpendicular to the pupil line.

Figure 38 is a schematic representation of a viewer V, the Cartesian coordinate system represented by axis VH, VRT attached to the viewer, the pupil line PL, the visual axis right (VAR), the visual axis left (VAL) and the visual plane (VP) of the viewer.

Figure 39 is a side view of the schematic representation of the viewer V shown in Figure 38, and the vertical axis VRT, and the visual axis VAR, VAL and the visual plane.

Definitions

Barco Escape™ is an arrangement of three display surfaces one immediately in front of a viewer and one on each side. Projectors are provided for projecting motion pictures onto the three display surfaces. The display surfaces may also be emitting screens such as LED walls.

Binocular field of view. The region of space seen by both eyes of a viewer at the same time. On figure 1, the binocular field of view covers the region I in front of the viewer.

Component (of a vector): "component" will have the same meaning as in mathematics and physics. In particular, we will consider the components of a vector along the horizontal and vertical. In specific cases, we will consider the components of a vector along the bottom edge and the lateral edge of a screen. More generally will also consider the components of a vector in a reference system attached to the head of a viewer: a first component along the visual horizontal or pupil line and a second component along an axes perpendicular to the pupil line and the viewing plane. An example is given on figure 8c where the velocity V with which an object or picture elementis moving across a display surface. The velocity V has a component Vx along an horizontal axis (parallel to the top and bottom edges of the rectangular display surface) and a component Vy along a vertical axis (parallel to the lateral edges of the rectangular display surface). Another example is shown on figure 37. A picture element Px moves across a display surface DS with a velocity V. The viewer's head is slightly tilted: the pupil line PL is not parallel with the top or bottom edges of the rectangular display surface (in most applications like cinema, home cinema etc... the display surface is rectangular with the right and left edges parallel to the local vertical and the top and bottom edges parallel to the local horizontal). The pupil line PL and visual vertical VRT form a local system of reference attached to the face of the viewer. The component V_PL of the velocity V along the pupil line PL is obtained as usual in an orthogonal system of reference.

Display: Throughout the description, the following terms relate to display surfaces: display, front projector display, display surface, display screen, lateral display, display surface, front projection screen. However, lateral refers to screens positioned laterally with respect to a viewer and front or main refers to a screen positioned in front of a viewer when the viewer is seating in a regular theatre: .

A "display screen" can be a projection screen, an LCD screen, a LED display, a plasma screen, or any other fixed format display. Horizontal: In a typical display setting like e.g. a theatre or a home cinema, the left - right median of the display is in the horizontal plane, i.e. perpendicular to the local acceleration of gravity or the UP - DOWN direction indicated on Figure 2 and 3. In those cases, when the viewer is facing a screen, the horizontal direction is parallel to the top and bottom side of that screen. More generally, the horizontal direction for a viewer V is parallel to the pupil line. This can for instance be the case in a flight simulator, 4D cinema and amusement parks wherein the seats in which the viewers are positioned can be tilted. In those cases, it is the (component of the) movement of an object on screen along the visual horizontal or pupil line of the viewer that is of relevance to the Pulfrich effect. This is illustrated by figure 38 in which the horizontal for viewer V is determined by the pupil line PL (also known as the visual horizontal VH).

Monocular field of view: a region of space seen by one eye of a viewer and not the other eye of said viewer. In figure 1, the monocular field of view II is a region of space seen by the right eye only. In figure 1, the monocular field of view III is a region of space seen by the left eye only. This definition of the monocular field of view does not necessarily correspond to the generally adopted definition.

Motion picture. A sequence of filmed images viewed in rapid succession so that the illusion of continuity and motion is created.

Projection Screen: A projection screen is a surface and a support structure used for displaying a projected image for the view of an audience. Projection screens may be pieces of fabric typically coated to behave as closely as possible as a Lambertian emitter, as in a movie theater; the can be painted on the wall; they can be permanently installed and they can be portable with tripod or floor rising modes as in a conference room or other non-dedicated viewing space. Uniformly white or grey screens are used almost exclusively as to avoid any discoloration to the image, Screens can be further designed for front or back projection In a front projection system, the image source (e.g. a projector) is situated on the same side of the screen as the audience. In this description, a projection screen will be any surface (planar or otherwise) on which images can be projected. Pupil Line: Line drawn through the pupils of both eyes. See line PL on figure 38.

Pulfrich Effect: The Pulfrich effect is a psychophysical perception wherein lateral motion (i.e. from the right to the left or from the left to the right of an object in the field of view is interpreted by the visual cortex as having a depth component, due to a relative difference in signal timings between the two eyes. Vertical: a direction perpendicular to the horizontal. In a typical display setting, the vertical is parallel to the local acceleration of the gravity vector or in other words the direction of a plumb line. More generally, vertical means "visual vertical i.e. a line that is perpendicular to the viewing plane VP and the pupil line PL. See line VRT on figure 38 and 39. Visual axis: the straight line extending from the object seen, through the center of the pupil, to the ma cula lutea of the retina. Synonym: line of vision. See VAR (Visual Axis Right) and VAL (Visual Axis Left) on figure 38. Viewing Plane: a plane passing through the point of sight; specifically : the plane in which the visual axis of the two eyes lie in binocular vision. See VP on figure 38 and 39.

Picture element: is part of an image or object displayed on or emitted from a display surface. Inter eye distance (IED) or Interpupillary distance is the distance between the center of the pupils of the two eyes. The average inter eye distance is 64.7 mm for male and 62.3 mm for female. It is usually in the range of 5 to 8 cm.

Intereve luminance disparity or intereve illumination disparity corresponds to the difference between the illumination entering one eye with respect to the illumination entering the other eye.

The ratio of illumination between the luminance entering one eye with respect to the other eye, 11/12 is also a measure of intereve luminance disparity.

Detailed description of embodiments.

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

Furthermore, the terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

Moreover, the terms top, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions unless it is specifically stated as such. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.

It is to be noticed that the term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

An aspect of the current invention is to provide a device for viewing three-dimensional effects in at least one motion picture displayed on at least one display surface, according to the Pulfrich effect.

Such a device comprises means to cause inter-eye luminance disparity at the basis of the Pulfrich effect. The device comprises at least one means for increasing the amount of light entering an eye of a viewer compared to the amount of light entering the other eye. The means to cause inter-eye luminance disparity are preferably positioned in the monocular field of view of the viewer. The binocular and monocular field of view of an average human being are represented on Figure 1 : the binocular field of view I spans an angle of approximately 100 degrees of angle in front of the viewer. The right monocular field of view II of the viewer spans an angle of approximately 60 degrees of angle on the right side of the viewer and the left monocular field of view III of the viewer spans an angle of approximately 60 degrees of angle on the left side of the viewer. At least one object in images displayed on the display surface is moving in a horizontal direction. Using the terminology used in kinematics (the branch of classical mechanics which describes the motion of, bodies (objects), and systems of bodies) , this means that at least one object has a velocity with a component in the horizontal direction. The principles of the invention will now be explained in more detail based on Figures 2 and 3. We assume that the only source of light in the setting of Figures 2 and 3 are the display 1 and the light sources 3 and 4. For the sake of clarity, we assume that the viewer is facing towards the display 1, that the head of the viewer is straight-up and that the line joining the left eye and the right eye is parallel to LEFT - RIGHT median of the display 1. In a typical display setting like e.g. a theatre or a home cinema, the left - right median of the display is in the horizontal plane, i.e. perpendicular to the local acceleration of gravity or the UP - DOWN direction indicated on Figure 2 and 3.

A viewer 2 with a left eye and a right eye looks to a display 1. The display shown on Figure 2 is for instance an LCD display or a plasma display but the invention also applies to LED displays, fixed format displays, rear and front projection systems etc...

The viewer 2 can see with both eyes. The viewer 2 has the ad-hoc optical correction in the form of contact lenses or prescription glasses if needed. In each case, both lens of the glasses or both contact lenses have the same transmittance or substantially the same transmittance (i.e. their transmittance vary by no more than 5% or preferably no more than 10% or preferably no more than 25%).

The viewer 2 is immobile with respect to display 1.

In the example illustrated in Figure 2, means for increasing the illumination on the right eye of the viewer and on the left eye of the viewer are provided by light sources 3 and 4 respectively. The light sources are positioned in a monocular field of view of each of, respectively, the left and right eye. For instance, light source 3 is in the monocular field of view of the right eye and light source 4 is in the monocular field of view of the left eye.

The Pulfrich effect can be induced by activating the light sources 3 and 4 differentially. This means that inter-eye luminance disparity is induced by having one of the light sources emitting more light than the other.

Examples of situation where inter-eye disparity is induced are:

Light source 3 turned ON, light source 4 turned OFF

Light source 3 turned OFF, light source 4 turned ON

The amount of light reaching an eye of the viewer is at least twice the amount of light reaching the other eye of the viewer so as to induce inter-eye luminance disparity sufficient to let the viewer perceive 3D effects

More pronounced 3D effects can be achieved when the amount of light reaching an eye of the viewer is 5 times or more the amount of light reaching the other eye of the viewer. Viewing in 3D means that the viewer 3 will perceive (at least) part of the images displayed on display 1 as if they were in FRONT of display 1 and/or (at least) part of the images displayed on display 1 as if they were at the back of / behind display 1.

For instance, if light source 4 is turned OFF and light source 3 is turned ON:

Images of objects displayed on display 1 and moving from RIGHT to LEFT (i.e. from the right of display 1 to the left of display 1) will be perceived by viewer 2 as if they were in FRONT of display 1 as schematized on Figure 4a and 4b.

Images of objects displayed on display 1 and moving from LEFT to RIGHT (i.e. from the left of display 1 to the right of display 1) will be perceived by viewer 2 as if they were at the BACK of / BEHIND display 1 as schematized on Figure 5a and 5b.

On Figures 4a and 4b, images of a house 5, not moving with respect to e.g. the sides of display 1, and a flying plane 6 moving from the right to the left of display 1 are displayed. The light source 4 is turned off and does not emit light. The light source 3 is turned ON and illuminates the right eye of viewer 2.

The amount of light reaching the eyes is:

For the right eye: LR = light emitted by display 1 and reaching the right eye of viewer 2 + L3, the light emitted by light source 3 and reaching the right eye of viewer 2.

For the left eye: LE = light emitted by display 1 and reaching the left eye of viewer 2.

The difference in amount of light received by the right eye and the left eye of viewer 2 is thus LR - LE = L3, the light emitted by source 3 and reaching the right eye, which is different from zero when the light source 3 is turned ON. The first condition for the Pulfrich effect: inter-eye luminance disparity is fulfilled.

In some cases, inter-eye luminance disparity can be further amplified by the distribution of light emitted by the display. For instance, if the left side of the image on display 1 is black while the right side of the image on display 1 is white, the right eye can be more illuminated than the left eye by the display 1 itself. In some cases, it may be useful or needed to tailor the images being projected to optimize the inter-eye luminance disparity and the induced Pulfrich effect. The perception of the image of the house 5 being immobile with respect to the display and the viewer will not be affected by the Pulfrich effect.

On the other hand, the image of the aeroplane 6 moving with a velocity VP in the right to left direction, the aeroplane will be perceived by viewer 2 as if it were in FRONT of display 1, i.e. closer to the viewer 2 than display 1.

On Figures 5a and 5b, images of a house 5, not moving with respect to e.g. the sides of display 1, and a flying plane 6 moving from the right to the left of display 1 are displayed. The light source 4 is turned off and does not emit light. The light source 3 is turned ON and illuminates the left eye of viewer 2.

The amount of light reaching the eyes is:

- For the right eye: LR = light emitted by display 1 and reaching the right eye of viewer 2 + L3, the light emitted by light source 3 and reaching the right eye of viewer 2.

For the left eye: LE = light emitted by display 1 and reaching the left eye of viewer 2 The difference in amount of light received by the right eye and the left eye of viewer 2 is thus LR - LE = L3, the light emitted by the light source 3 and reaching the right eye, which is different from zero when the light source 3 is turned ON. The first condition for the Pulfrich effect: inter-eye luminance disparity, is fulfilled.

The perception of the image of the house 5 will not be affected by the Pulfrich effect because it is immobile with respect to the display and the viewer. The house will appear to be in the plane of display 1.

On the other hand, the image of the plane 6 moving with a velocity VP in the left to right direction, the plane will be perceived by viewer 2 as if it were at the BACK of / BEHIND display 1, i.e. further away from viewer 2 than display 1.

If light source 3 is turned OFF and light source 4 is turned ON:

Images of objects displayed on display 1 and moving from LEFT to RIGHT (i.e. from the right of display 1 to the left of display 1) will be perceived by viewer 2 as if they were in FRONT of display 1 as schematized on Figure 6a and 6b.

Images of objects displayed on display 1 and moving from RIGHT to LEFT (i.e. from the right of display 1 to the left of display 1) will be perceived by viewer 2 as if they were at the BACK of / BEHIND display 1 as schematized on Figure 7a and 7b.

In all cases, the amplitude d of the distance at which a moving object (the plane 6 in these examples) will be perceived behind or in front of the display 1 is function of (a) the amplitude of the inter-eye luminance disparity (i.e. LE-LR) as well as of (b) LE and LR, (c) the velocity VP of the moving object (and in particular the component of the velocity along the horizontal direction (dashed line H on e.g. Figure 4a), (d) the distance DO between the display 1 and the viewer 2 and very probably (e ) the visual system of the viewer 2 (by this we mean that while the biology of the visual system is the same for all human beings, different viewers in the same conditions may perceive the moving object at different distances dO).

The Pulfrich effect will occur even if the object moves diagonally across the screen. In other words, the effect will be present whenever (a) there is inter-eye luminance disparity and (b) the velocity of at least one object displayed on display 1 has a horizontal component i.e. a component along a direction parallel to the line joining the left eye and the right eye of the viewer 2.

The meaning of the velocity of an image displayed on display 1 is shown on Figure 8a and 8b.

If the position of the image of plane 6 displayed on display 1 has moved with respect to the display from e.g. the lower left corner of display 1 between a time t (Figure 8a) and to the upper right corner of display 1 at a time t + At (Figure 8b); the component of its velocity along the horizontal direction is Ax / At (the ratio of the displacement Ax in the horizontal direction and the time interval At) and the component of its velocity along the vertical direction is Ay / At (the ratio of the displacement Ay in the horizontal direction and the time interval At).

Ax and Ay can be measured in meters or centimeters or even in number of pixels, whichever is more convenient in function of the display and the settings in which the display is used.

The velocity of the image of an object is also illustrated on Figure 8c where both the image of a plane displayed at instant t and the image of a plane displayed at instant t + At are overlaid.

The image of a plane is displayed on display 1. At the time t, the image 6a of the plane is located in the lower left corner of display 1. At the time t + At, the image 6b of the plane is located in the upper right corner of display 1. The displacement Ax and Ay are given for the tip of the nose cone of the plane for the sake of illustration. The velocity V of the image of the plane has the component Vx = Ax / At along the horizontal direction and the component Vy = Ay/ At along the vertical direction. In normal circumstances the plane of the display is parallel with the local acceleration of gravity and the words horizontal and vertical have the usual meaning.

According to one interpretation of the Pulfrich effect, the Pulfrich effect is caused by a difference in response time between the right eye and the left eye .

If we consider the situation of Figure 4a and 4b, the left eye receiving less light than the right eye, the left eye would be "slower" than the right eye.

What this means is that while the right eye sees an image displayed at an instant t, the left eye would still see the image that was displayed at an earlier instant t - delay where delay is a function of the physiology and physical condition of viewer 2, pathologies that would affect the visual system of viewer 2 and the inter-eye luminance disparity (the difference between light received by the right eye and the light received by the left eye) as well as the amount of light reaching that eye.

The delay varies typically from a few ms when in a bright environment to tens of ms in a dark environment. The delay can also vary in function of time (for instance with dark adaptation of the eyes).

This is represented on Figures 9a and 9b. In the example of Figure 9a, light source 3 being lit-up, the right eye receives more light and is thus "faster" than the left eye. Let us consider a sequence of images displayed on display 1 wherein a point P moves from the right of the screen to the left of the screen.

The point P moving from the right to the left, it is perceived at the position P(t0) at an instant tO by the right eye while the left eye still perceives the point P at position P(t0- At) as it was displayed at instant tO - At, At being the delay induced by inter-eye luminance disparity.

By tracing the line between each eye and the image it perceives at instant tO, one can evaluate the parallax with which the viewer 2 sees the moving object being displayed. In the case of Figure 9a, the point P is perceived at instant (tO) as if it were at the intersection Pp, in front of display 1, closer to viewer 2 than display 1.

In the case of Figure 9b, the sequence of images being displayed on display 1 represents a point P moving from the left to the right of the screen. This time, the point P is perceived as if it were behind the display 1.

The means for inducing inter-eye luminance disparity are preferably provided for both eyes in the form of light sources and the light is increased on one side or the other of the viewer according to the movement of objects in the motion picture.

Therefore, a control unit is provided for increasing the illumination of the first and/or second light source according to command signals correlated to the displayed images of the displayed motion picture dependent upon horizontal movement of an object in the displayed images (optionally when at least one object is moving horizontally from left to right or right to left).

Real time motion detection algorithms may automatically detect a movement in the motion picture, and trigger the emission of command signals to the control unit, or the command signals can be pre-calibrated and emitted during the viewing of the motion picture. This embodiment is preferable as the light emitted by the first and/or second light source may then be increased progressively before the movement starts so as to be clearly seen by the viewer while viewing the motion pictures. Alternatively, in digital cinema, metadata can be included in the files encoding the motion picture. Said metadata determines when to activate light source 3 or 4, with which intensity, when to deactivate the light sources etc.

Tests were carried out with solid state, e.g. LED light sources and incandescent light sources to illuminate preferentially one of the eyes of a viewer V looking at moving images on a screen. The purpose of the tests was to determine whether or not it would be possible to induce the Pulfrich effect in a theater without using an absorbing filter in front of one of the eye of the viewers but instead to manipulate the light entering the eyes of the viewer directly and induce inter-eye luminance disparity. This problem involved solutions depending on antagonistic parameters. The solution had to be selective enough to allow illumination of one eye only (in order to induce a substantially different illumination of the retina of the left eye and the right eye) and applicable to a large audience of tens or hundreds of viewers. For application with a Barco Escape™ Display System, the solution had also to be as unobtrusive as possible, which excluded the use of filters and the associated glasses. The sought after solution had to keep the field of view of the viewer free. No discontinuity (caused by e.g. the rims of 3D glasses) was allowed in order not to spoil the immersive experience of the viewer.

It appeared from tests carried out with test subjects of European and East Asian descent that three positions to locate a light source close to the eye yielded better results. These positions are shown on Figure 10 and are "A" adjacent to the lateral cantus and at the level of or below the lateral hooding area of that eye, "B" at the level of or below the lower eyelid and "C" close to the medial canthus. The three positions were also advantageous to viewers wearing prescription glasses as the glass reflected part of the light back towards the eye of the viewer and thereby enhanced the effect. In the three positions, the light emitted by the light source was emitted in the general direction of the pupil (i.e. an area larger than the pupil can be lit).

In a first example of an embodiment of the present invention, a headset 91 seen on Figure 11 can be positioned on the head as seen on Figure 12. In this example, the headset has two lateral arms 91a and 91b extending from the back of the head. When worn by a viewer, the extremities of the arms 91a and 91b are close to the eye of the viewer wearing the headset 91. The extremity of each of the arms 91a and 91b supports a light source such as a solid state lamp of which an LED (Light emitting diode) is one example. A light source such as LED 92 is fastened to the arm 91b and a light source such as LED 93 is fastened to the arm 91a. Each light source such as an LED is connected to control electronics, e.g. on a Printed Circuit Board 95 by means of a cable such as a twisted cable pair 94 (shown only for light source, e.g. LED 92 on Figure 11). The electronics can include a switch to activate either the light source such as LED 92 or the light source such as LED 93 which is controlled depending upon the horizontal motion on the screen to be viewed. In the first version of an headset 91 that was used to evaluate the present invention, a connector 96 at the other end of the twisted cable pair 94 made it easier to connect and disconnect the light source such as the LED from the electronics, i.e. the PCB. The electronics, i.e. the PCB may accommodate a battery support 97 (to accommodate e.g. 3 AAA or AA batteries 97b) or it may itself be provided with a cable such as a twisted cable pair to connect to a power supply. The purpose of upper arm 91c is to help maintain the position of the lateral arms 91a and 91b.

In the first version of the headset 91, the electronics, i.e. PCB 95 accommodated two potentiometers 98 and 99, one for each of the light sources e.g. LED's on arms 91a and 91b. The potentiometer was used to vary the amount of light emitted by the light source, e.g. LED 92 and 93. Test subjects were requested to change the potentiometer settings to adjust the light level illuminating their eyes so that the Pulfrich effect would be visible without causing them discomfort. The tests were carried out with video sequences where images of objects moving in different directions are displayed.

One of the video sequences used is exemplified by Figure 13.

The images displayed in the example of video sequence comprise three groups of objects A, B and C. The objects in group A move from the right side of the screen towards the left side of the screen with velocities vl, y_2, v3. The objects in group B move from the left of the screen to the right of the screen with velocities y_4, y_5, y_6 .... The objects in group C either remain immobile or move in the vertical direction (i.e. from "DOWN" to "UP" or from "UP" to "DOWN") with velocities y7, v8, y9 .... The velocities of the objects in the group A and B varied from zero at the beginning of the video sequence up to more than one thousand pixels per second (i.e. the objects went from one side of the display to the other side in one second or less). Tests were performed with LCD displays (with a diagonal of 14 inches and 55 inches) as well as a front projection display (projector B1M from ASUS) with which images were projected on a wall painted in mat white. The resolution of the displays was 1280 X 800 pixels. Test subjects reported results as expected.

When the right eye of the subject was illuminated by the LED adjacent to it, the objects of group A appeared to move outside the plane of the display surface (i.e. the screen of the LCD display or the wall on which images were projected) and in front of the display surface while the objects of group B appeared to move behind the plane of the display surface. Objects in the group C appeared to stay in the plane of the display surface and between the objects in group A and B.

When the left eye of the subject was illuminated by the LED adjacent to it, the objects of group B appeared to move outside the plane of the display surface (i.e. the screen of the LCD display or the wall on which images were projected) and in front of the display surface while the objects of group A appeared to move behind the plane of the display surface. As previously, objects in the group C appeared to stay in the plane of the display surface and between the objects in group A and B.

The amplitude of the effect increased with the velocity (the higher the velocity, the more pronounced the effect) and with the intensity of the light illuminating the eye.

For a given intensity of light, the effect collapsed when the velocity of the objects moving in a specific direction exceeded a threshold or critical velocity VP critical.

The direction within which the collapse can occur depends on which eye is more illuminated than the other.

This can be understood based on the geometric construction that were used on Figures 9a and 9b.

Let us consider the case of Figure 14 where the right eye of viewer 2 is illuminated by the light source 3 adjacent to it while light source 4 is turned off. A sequence of images displayed on the display surface of display 1 represents a point P moving from the LEFT to the RIGHT. As explained before, the perceived position Pp of point P (instead of a point P, a small object like a little square box as on figure 13 can be used) is determined by the intersection of the lines joining the left and right eye to the position of point P perceived by each eye. From Figure 14, one sees that if the product of the velocity VP and the delay At induced by inter-eye luminance disparity exceeds the distance IED between the left and right pupils, the two lines will intersect behind the viewer 2. At the same time that the effect collapsed, the test subject reported visual artefacts affecting the images of the object in motion (apparent change of luminance and/or color, sensation of after image comparable to illusory palinopsia).

The critical velocity can be used to estimate the delay At induced by inter-eye luminance disparity. This allows us to establish Look-Up-Tables. For a set of display luminance (i.e. the amount of light emitted by the display and reaching the eyes of viewer 2), the delay At is evaluated for a set of luminance emitted by a light source (3, 4). The horizontal speed of objects moving through the screen can be measured directly. The intensity of the light emitted by the display 1 and reaching each of the eyes of viewer 2 can be measured with e.g. a photometer. In McGraw-Hill, Dictionary of scientific and technical terms, 6^th Edition, a photometer is defined as "Aw instrument used for making measurements of light or electromagnetic radiation, in the visible range. " When the viewer 2 experiences the collapse of the effect (as described earlier), it means the delay At induced by inter-eye luminance disparity is approximately equal to the ratio of IED, the distance between the left and right pupil, and the critical velocity VP critical:

At = IED / VP critical

The look-up table can be used to generate the metadata that will yield best results for a given video sequence on a given display and with given light sources 3 and 4.

The look-up table can be evaluated for different population groups, to take variations of the visual system from one group of individual to another. The look-up table can for instance be established for e.g. viewers aged 10 to 20, viewers aged 20 to 30 ... and viewers aged 90 to 100. The results obtained for a test group are averaged and the lookup table then gives the necessary data to optimize the 3D effect. If a movie is made for "All Audiences", the look-up table can be established based on a group of test subject representative of the general population.

When the display 1 used is a front projection display in a theater, it is known that the brightness of images projected on the screen will have a maximum brightness of 50 or 100 cd/m². The look-up table can be established e.g. for brightness varying from 0 to the maximum brightness by steps of 10 cd/ m². Once the light sources 3 and 4 are known (e.g. a given type of LED as in the headgear of Figure 11, 12 and power supply; with known characteristics), the delay At is evaluated in function of the light they emit or more easily the current with which they are driven or the duty cycle at which they are driven if Pulse Width modulation is used to control the output power of the light sources

3 and 4.

Once a movie has been edited, the metadata is generated for the video scenes that are to be seen in 3D. At the beginning of a scene to be experienced in 3D, the metadata comprises for instance a start signal; information about which light source must be lit up and the PWM duty cycle at which the light source 3 and/or 4 will be driven. At the end of a scene, the metadata comprises e.g. a stop signal. If the light intensity must be increased or decreased gradually, the metadata can also contain information about the rate at which the duty cycle must increase or decrease (if the sources of light are controlled with Pulse Width Modulation). As explained later, the light sources 3 and 4 can generate white light or colored light. In that case, the metadata can also contain information on the color that must be emitted by the light sources at a given time.

The tests were carried out with different types of displays. LCD displays with a refresh rate of 48 frame per seconds or more and with dimensions 60 mm X 35 mm; 310 mm X 17,5 mm and 890 mm X 500 mm. Tests were also carried out with projection displays: a digital cinema projector DP2K-20C from Barco as well as a variety of smaller projectors used in meeting rooms.

It appeared during the tests that a test subject found the use of the headset more pleasing (less intrusive) when the light source e.g. an LED was turned ON gradually, over the course of e.g. 0.5 second to 1 second or more.

The position of the light sources LED 92 and LED 93 is adjustable. The test subject can move the light source, i.e. LED 92 forward and backward. In a first version of the headset, the light source, e.g. the LED was soldered on a small PCB and the PCB fastened to the arm 91a by a ring that could slide along the arm 91a. This is not shown on Figures 11 and 12.

An alternative to a sliding mechanism to adjust the position of the light sources, e.g. LED 92 and 93 is to increase the area of the light source as shown on Figure 11. One or more light sources, e.g. LEDs 92, 92a, 92b ...are positioned in a cavity 100 and covered by a diffuser 110, light exiting the diffuser to illuminate the eye. With this alternative, the result is not as sensitive to the exact position of the headset. The bottom of the cavity can be coated with a reflective layer (e.g. silver paint, aluminum foil, etc...) The positions for the light sources, LED 92 and 93 that seem to be the best trade-off between the perceived amplitude of the Pulfrich effect and viewer experience (no or little negative sensation on nose etc ., no or little disturbance in the viewer's field of view) is close to the lateral cantus and at the level of or below the lateral hooding area of the eye (the light will reach the retina from the side) or below the lower eyelid (the light emitted by the LED will reach the retina from below the eye).

Tests were carried out with green, red, blue and white light sources, e.g. LEDs. The test subject preferred the white and blue light source e.g. LED with a marked preference for the white light source, e.g. LED.

The light source, e.g. LED is for instance a "cold white" LED with a maximum light output of less than 10 Cd. Figure 24 gives a schematic representation of a front projection display comprising three front projection screens (2408, 2409 and 2410) and three projectors (2411, 2412 and 2413), each projector projecting an image on one of the three projection screens. This display system corresponds to the Barco Escape™ Display system. Generating any color in the visible part of the spectrum is included within the scope of the present invention. If used in conjunction with a Barco Escape™ Display System (as illustrated on Figures 15a, 15b, 15c, 15d and Figure 24) it may be advantageous to match the color of the light emitted by one of the light sources, e.g. LED 92 and 93 with a color of the images projected on the lateral screens. For instance, if a dominant color on the left side of a viewer is blue (e.g. a landscape with a blue sky is projected on the screen on the left of the viewer), the light source close to the left eye will be driven to emit a blue or bluish light). The light source can be for instance a set of red and green light sources, such as Red Green and Blue LEDS with which different colors can be generated. Those light sources, e.g. LEDs can be discrete LEDs associated to a diffuser or a multicolor LED. When used in conjunction with a Barco Escape™ display system, the light emitted by a lateral screen and the light source, e.g. LED on the same side of the viewer can be used in tandem to enhance the Pulfrich effect. The intensity of the light illuminating the retina of e.g. the right eye results from light emitted by the light source, e.g. LED on the right side of the viewer, the light from the lateral screen on the right of the viewer, the front screen and any ambient light. The total intensity being larger than the intensity caused by either source of light on its own, the perceived amplitude of the Pulfrich effect is greater.

In another example of embodiment seen, the headset allows the positioning of other light sources below at the level of or below the lower eyelid and/or close to the medial canthus.

An extension of the arms 91a and 91b extends along the face of the viewer below the lower eyelid until the vicinity of the medial canthus. Additional sources of light can be positioned below the eyelid and/or close to the medial canthus on those extensions.

In another embodiment, the light sources, e.g. LED 92 and 93 are replaced by light funnels or light concentrators that collect the light emitted by one of the lateral screens in a Barco Escape™ display system as on figure 17 and 18 (the angle between a lateral screen 8 or 10 and the central screen 9 is 102.5 degrees). The light is collected and by refraction and/or reflection, it is directed towards the corresponding eye of the viewer (i.e. light of the lateral screen on the left of the viewer is redirected towards the left eye of the viewer and light of the lateral screen on the right of the viewer is redirected towards the right eye of the viewer). The light funnel can be a hollow and flexible light guide. It can also be an optical fiber or a bundle of optical fibers (a full light guide). The light guide can be a molded PMMA structure with a reflective coating on the outer surface.

Figure 15a illustrates how a viewer perceives an Escape display system when wearing filter glasses as they exist for 3D cinema.

Because of the wider than usual field of view covered by the screens 1511, 1510 and 1512 of an Escape display system, the glasses introduce discontinuities 1520 and 1530 in the field of view.

Figure 15b illustrates how a viewer perceives an Escape display system when wearing a device according to the invention. The light sources will be perceived as fuzzy blobs 1503 and 1504 at the limit of the visual field on the left and on the right.

Figure 15c illustrates the problem of wrong perspective that would occur in an Escape display system if anaglyphic images are projected for a viewer in a sweet spot. On Figure 15c a first viewer VI looks at the screen 1511 on which the anaglyphic image of a football 1540 under a table 1550. The perspective is correct.

For a second viewer V2 looks at the screen 1511 on which the anaglyphic image of a football 1540 under a table 155 is projected. Because of his position, the viewer V2 would expect to see all of the football and less of the surface of the table but sees images that were filmed for a viewer positioned frontally with respect to screen 1511 as viewer VI. The perspective is not correct.

When relying on the Pulfrich effect, static images or slowly moving images will not be affected. They will be perceived as any 2D images.

Images moving fast enough to allow the Pulfrich effect to be perceived, the perspective will change automatically in function of the position of the viewer. The principle is illustrated on Figure 15d which is a top view of an Escape display system.

A point P is moving on the lateral screen. When looking at the screen 1511, the viewer VI sees the point P moving with a velocity VP1 in the plane of the screen.

The viewer V2 being at an angle, will see the point P moving at a lower speed VP2 = VPl*cosP where β is the angle between the direction in which a viewer looks at the screen 1511 and the normal to that screen. For viewer VI, β is close to zero while for viewer V2 β is closer 90 degrees of angle, thereby seeing the point P move in the right to left direction with a speed VP2 = VPl*cos (80°). The reduction in speed will be more and more pronounced as the angle increases and the amplitude of the Pulfrich effect will be reduced thereby mitigating the problem of wrong perspective. Figure 16 illustrates another embodiment of a device 1400 according to the invention.

The device comprises a support structure, which in this embodiment has the shape of a headband 1420 which goes behind the head of the viewer. The headband has preferably two curved parts 1422 such that the headband goes around the ears, which increases the support. The headband may further comprise in-ears loud speakers 1430 designed to penetrate partially inside the ears. This feature further increases the support of the support structure when carried by a viewer. It also allows the viewer to hear the soundtrack of the moving picture via the headset device. However, the invention is not limited to in-ears loudspeakers and may comprise any type of loudspeaker used for headsets. In a proximity of the in-ears loud speakers, around the ears when the device of Figure 16 is carried, a compartment 1410, 1415 is foreseen, for example on each side of the device, for carrying a control unit, a receiver, and a power supply. The power supply could also be on one side and the control unit with the receiver on the other side.

Light sources, e.g. LEDs 92 and 93 are attached to the device 1400 by two plates 1440, 1450 respectively extending from compartments 1410, 1415. At an extremity of each plate 1440, 1450, two movable parts 1445, 1455 are attached to the plates preferably by a sliding mechanism. The light sources, e.g. LEDs 92 and 93 are fixed to the movable parts 1445 and 1455 respectively, on the inner side such that when the device is carried, light emitted by the light sources, e.g. LEDs is going towards the viewer's eyes.

The movable parts 1445, 1450 are preferably capable of sliding on plates 1440, 1450 in horizontal direction such as to adapt to distance of the light sources, e.g. LEDs to the eyes when the device 1400 is carried by the viewer, and in a vertical direction such as to adapt the height of the light sources, e.g. LEDs 92, 93 with respect to the viewer's eyes. The device of Figure 16 may be plugged directly in a viewer's seat, wherein two cables are provided: one for transmitting the audio signals, and one for transmitting the command signals.

In another preferred embodiment, the device 1400 comprises a wireless connection such as a WiFi connection or Bluetooth for 3D sound. Preferably, the command signals are transmitted to the device by an invisible radiation such as infra-red or other undetectable means such as a wireless connection , e.g. Bluetooth wavelengths, or ultrasound to change the light sources e.g. LEDs from one side to the other in dependence upon the horizontal motion of objects on the observed screen. Metadata corresponding to the sequence of images displayed can be sent to device 1400 or 91 wirelessly.

In a preferred embodiment, the loud speakers are configured to provide soundtrack synchronized with the motion picture. In a most preferred embodiment, the sound transmitted provides three dimensional audio effects. In a preferred embodiment, the techniques to render three-dimensional audio effects comprise binaural recording, and most preferably holophonic™ recording.

In another embodiment, the means for increasing the illumination in a viewer's eye, is incorporated directly in a viewer's seat, or in a "U-shaped head support pillow" attached to the seat. The light source can be attached to a brass coil neck, incorporated in the seat, which is flexible and whose position can therefore be manually set by the viewer. In another embodiment, a head support could be included in the seat in order to provide additional comfort to the viewer but also to remove the disturbance generated by the light sources of neighbouring viewers. When a pillow is used, the latter could be fixed by quick fixing means, such as Velcro™.

There may be circumstances where the electronics (like e.g. LEDs 92 and 93 and their drivers) and / or optics (like e.g. light funnels) required to induce the Pulfrich effect are not allowed. This can be for economic reasons or because of the viewers' expectations.

Directional lights suspended to the ceiling of the projection room might be activated selectively to illuminate both eyes of a viewer differently. If the lights are too directional, several lights are required to avoid a sweet spot. Those light adding to the ambient light, they will be responsible for a decrease of the contrast ratio which is undesirable. Furthermore, additional electronics is still required to activate the lights in synchronization with the images being projected.

The inventor found out that it is possible to use the light distribution on the one or more displays screens of a display system to induce the Pulfrich effect.

A first example of how different areas of a display system can be used to induce the Pulfrich effect is illustrated on figure 17 and 18.

The 3D display according to the invention comprises at least two display surfaces, in the current example LCD displays. A first display 171 and a second display 172. A third display surface (given the reference number 176), or LCD display can be positioned on the left side as well but has been omitted for the sake of simplifying the description.

A viewer 173 faces the first display 171 at a distance Dl as seen on figure 18. A second display 172 makes an angle (a) with the first display 171. In this example, the second display 172 is on the right side of the viewer 173 as indicated on figure 18.

The second display 172 is at a distance D2 from the first display 171, the distance D2 is measured as indicated on figure 18. The second display can also be shifted closer to the viewer; this shift is characterized by the distance D3 as indicated on figure 18.

The angle β is the angle beyond which objects on the right side will disappear from the field of view of the left eye. The angle β is the angle beyond which objects on the right side will disappear from the field of view of the left eye. The angle β may vary from individual to individual. For the test subjects who evaluated the display, β was in the interval 15 to 30 degrees. The angle β may vary from individual to individual and from the position of the viewer. While not necessary, it may be advantageous to position the viewer with respect to the second display 172 so that it will be outside of the field of view of the left eye of viewer 173 in order not to illuminate the left eye directly (i.e. ray of lights emitted by the second display 172 do not reach the left eye in a straight line).

Means for increasing the amount of light entering one eye of the viewer is, in the current example, provided by display 172 itself.

The average luminance of display 171 was modified in three ways:

- By varying the image content (e.g. an entirely black image is less bright than an entirely white image) that determines the state in which the spatial light modulator is.

By varying the luminance of the backlight (on most laptop computers, the brightness can be increased or decreased by using keyboard shortcut like e.g. Fn J, or Fn† on a DELL Latitude E6420 laptop computer).

By adding a filter covering part or whole of the screen.

In a series of tests, display 171 was the screen of a DELL LATITUDE E6420 laptop computer with a diagonal of 14 inches (the active display area being 310 mm X 175 mm), a 16:9 aspect ratio and a maximum average luminance of +/- 277 cd/m².

Display 172 was an Acer AL718 with a diagonal of 17 inches (the active display area being 340 mm X 270 mm) and a maximum average luminance of +/- 200 cd/ m².

The moving pictures used on display 171 to evaluate the Pulfrich effect were those of a merry-go-round (also known as carousel): the merry-go-round is seen from a lateral view (as seen on figure 19) and rotates at an apparent angular speed ω of Π/2 s^"1 (or 90 degrees of angle per second) which amounts to say that the moving pictures have a period T of 4 s. The direction of the movement in the plane of display 190 is from the right to the left from the viewer's perspective, the maximum amplitude A of the apparent movement in the plane of display 171 being 200 mm (that is, the position of given point of the image of the merry-go-round will vary between two extremes El and E2 on the screen of display 171, the maximum difference A between these two extremes for an outermost point of the merry-go-round being 200 mm or 2/3 of the width of the active display area). In the example of figure 19, El and E2 correspond to the tip of the left wing of an airplane- shaped nacelle 194.

The tests were carried-out in a closed room approximately 7 m X 5 m and 2.5 meter high. The only light sources during the test were the screens of display 1 and display 2 to emulate the situation in a cinema. The closest wall on the left side of the viewer was at approximately 2 meters from the viewer. The closest wall behind the viewer was at approximately 1.5 meters from the viewer.

The table on which display 171 and 172 stood was covered by a dark, matte tablecloth to limit reflection of light originating from display 2 onto the left eye of the viewer.

Tests were carried out with different configurations. In a first configuration, Dl = 1 m, D2 = 0 m, D3 = 0 m and a = 155 degrees of angle. In a second configuration, Dl = 0.8 m ("." Is used as decimal separator e.g. 0.1 is one tenth), D2 = 0.1, D3 = 0.3 m and a = 120 degrees of angle. In a third configuration Dl = 0.6 m, D2 = 0.2, D3 = 0.4 m and a = 100 degrees.

The contrast setting of display 171 was left at factory settings. The image displayed on display 172 during the tests were a white field (i.e. entire image is white), a black field (i.e. entire image is black), a light gray field and a dark gray field. The luminance of display 172 for these 4 images was evaluated: a white field

corresponded to an average luminance of approximately 200 cd/m², a black field corresponded to an average luminance of less than 5 cd/m², a light gray field corresponded to an average luminance of approximately 75 cd/m² and a dark gray field corresponded to an average luminance of approximately 50 cd/m².

The luminance of display 171 was evaluated on randomly selected still images in the moving pictures used to evaluate the Pulfrich effect. With a first filter positioned on the entire screen, the average luminance of the screen of display 1 appeared to be

approximately 10 cd/m². With a second filter (superposed to the first), the luminance of the screen appeared to be less than 1 cd/ m². There was no systematic dark adaptation before the tests. A 200W halogen lamp was used between tests on the different configurations to allow the configuration to be changed.

In spite of reflection of the light emitted by Display 172 on the walls, the viewer 173, the desk and reaching the left eye and cross talk between display 172 and display 171 (i.e. light emitted by display 172 impinged on display 171 either directly or by reflection on walls, desk and viewer), the Pulfrich effect was perceived when the luminance of the light from display 172 entering one eye was 10 times higher or lower than the luminance of the light entering the other eye from display 171 and this for all configurations (in the first configuration, part of display 172 was still in the field of view of the left eye and a louver positioned on the dorsum of the viewer's nose was used to prevent light emitted by display 172 from reaching the left eye in a straight line. The right eye being illuminated and the apparent motion of the nacelles on the screen of display 171 being directed from the right to the left, the nacelles (see figure 19) appeared in 3D, i.e.

appeared to come out of the screen on the right and to re-enter on the screen on the left. This was in agreement with the Pulfrich effect as described in e.g." THE MAGNITUDE OF THE PULFRICH STEREOPHENOMENON AS A FUNCTION OF BINOCULAR DIFFERENCES OF INTENSITY AT VARIOUS LEVELS OF ILLUMINATION" by Albert Lit in the American Journal of Psychology volume LXII No. 2 of April 1949 pages 159 to 181; and "Pulfrich auto-stereo display with micro-prism array" by Chien- Yue Chen et al and others who studied the effect.

The impression of a three dimensional merry-go-round disappeared when display 172 was turned off and re-appeared when display 172 was turned on again. Whether or not the effect disappeared or reappeared gradually was not evaluated. The test subject mentioned nevertheless that the effect seemed to persist for a brief instant after display 172 was turned off. In a cinema or home theater setting with three screens, the ratio of illuminations that enter one eye includes the ratio of the light from images on a first display surface 171 directly in front of the viewer combined with light from a lateral display surface 172 and any ambient light compared with the light entering the other eye from the first display surface 171 combined with light from the other lateral display surface 172 and any ambient light entering the other eye. This ratio should preferably be greater than 2, more preferably greater than 5 and even more preferably greater than 9 for a more pronounced effect in particular when images displayed on display 1 are bright and/or when the amount of ambient or stray light that reaches the eyes of viewer 173 is of the same order of magnitude than the amount of light from display 171 that reaches the eyes of viewer 173. The director of the film can select scenes that achieve this ratio or shoot scenes specifically to achieve this ratio in combination with one or more objects moving in a given directions so as to be perceived either closer to the viewer or farther away from the viewer than the display surface.

At low illuminations (i.e. when the amount of light emitted by display 171 and the amount of stray light that reaches the eyes of viewer 173 is low), the test subject reported that the Pulfrich effect was perceptible at a ratio as low as 2.

Instead of liquid crystal displays, the images can be projected on front projection screens, or back-projection screens. The images can be displayed on Cathode Ray Tube displays, plasma displays, OLED and LED displays. The displays do not necessarily need to be of the same type. For instance, tests were carried out with a liquid crystal display 171 and a rear projection display instead of the liquid crystal display 172. In other tests, a front projection display was used instead of the liquid crystal display 172. The inter-eye illumination disparity can be generated in different fashions: a small display screen closer to a viewer may have the same effect on inter-eye illumination disparity as a large display screen farther away from the viewer.

To allow the rapid evaluation of inter-eye illumination disparity in a given display system, one can use a device 200 as seen on figure 20. Two photodiodes 201 and 202 are used to measure the amount of lights that reach two points distant of +/- 6 cm, or more preferably to the average Inter Eye Distance or distance between the left eye and right eye of a human being. The photodiodes 201 and 202 are mounted on a (planar) printed circuit board 204.

A profile 203 (e.g. in cardboard) is positioned between the photodiode 201 and 202 and fastened to the printed circuit board 204. The profile 203 mimics the effect that the nose and forehead in a human face have on the light distribution on the face and the eyes in particular. In figure 20, the photosensitive plane 205 of the photodiode is parallel to the plane of the printed circuit board 204. The cardboard profile 203 may be limited to a rectangle or be a profile of a viewer as illustrated on figure 20B. The profile can be modified to include a louver as is the case with the profile 203B on figure 20B.

For instance, if a source of light is directed at the left side of a human face, the light will easily reach the left eye but, being blocked by the profile 203, it will hardly reach the right eye in straight line. Reflections on the wall and objects in the environment may reflect some of the light that will ultimately reach the right eye.

In one example of device 200, the photodiodes were BPW34 manufactured by Osram Opto Semiconductor and Vishay. The photodiodes can be adapted for human eye sensitivity and be (even) more representative of what a human being will perceive. "Adapted to the human eye sensitivity" means that the photodiode is equipped with optical correction filters that offer the sensor a spectral responsivity function that corresponds to the rods and cones of the human eye. Their signal was amplified with an operational amplifier 206, 207 having resistors 208, 209 respectively (e.g. LM324 from Texas Instruments) as illustrated on figure 21 for the left and right photodiodes respectively. The resistance of each of the feedback resistors R204 and R205 is 1.2 ΜΩ with a 5% tolerance.

The sensitive part of both photodiodes is oriented identically. In the example of figure 200 the photosensitive part is parallel to the plane of the printed circuit board.

During measurements, the device 200 is held with the photosensitive parts (the face 205A and 205B of the photodiodes in the example of figure 20) facing in the same direction as the viewer, so as to capture light in the same way as the eyes of a viewer.

In yet another embodiment, a more complex version of the device 200 allows modifying the position of the photodiodes independently of the profile 203 and the PCB 204. The photodiodes can be rotated with respect to the printed circuit board 204 to evaluate inter eye illumination disparity when the fixation point varies while the position of the viewer's head remains fixed with respect to the display surface(s).

During the measurements performed, the output signal varied from a few mV to several hundreds. The contribution of stray light (remote sources of light like e.g. the screen of a laptop used to drive the projector as well as the reflection on the walls) to the output signal of the operational amplifier amounted to up to lOmV. The contribution of the darkest sequence of images (in the binocular field of view) to the output signal of the operational amplifier amounted to lOmV or more. The images used were either black and white or color. As would be expected, images where most of the pixels were "black" (like a black background with a handful of bright pixels representing asteroids moving across the display surface) yielded good results. The output signals can be used to determine the photocurrent and, using the quantum yield, the number of photons reaching each eye. This can in turn be used by the technicians, engineers, artists involved in postproduction or computer graphics animation to determine a desired brightness for the images to be projected on the front screen and the lateral screen,

Alternatively, inter-eye illumination disparity can be evaluated by e.g. a camera (still or video) to take images of a viewer's face looking at a first display like 171 while a second display like 172 illuminates the right side of the viewer's face. An analysis of the pixel values at and/or around the position of the pupils on the (still of video) image(s) of the viewer' s face will yield information on the amount of light that reaches the left and right eyes of the viewer.

A device 200 was used to evaluate inter-eye illumination disparity with different types of display. Figure 25 gives the result for a display system comparable to the display system of figure 17 and 18. The first display is an LCD display 251 (e.g. a DELL Latitude E5570) and the second display is a rear projection system. The dimensions of the rear projection screen 252 are 100 cm by 70 cm. The projector 253 is a B1M from ASUS. The LCD display was positioned in the middle and against a diffusing surface 254 having the same dimension as the rear projection screen 252. The diffusing surface 254 was adjacent to the rear projection screen forming an angle between 90 and 100 degrees with the rear projection screen. The measurements were done at various positions indicated by a cross on figure 25. The value of the ratio 11/12 corresponding to a position is indicated next to that position on the figure. II is the output signal of the photodiode most illuminated and 12 the output signal of the photodiode least illuminated (i.e. the photodiode shielded by the cardboard profile 203). The device 200 is represented in the position it is to take measurements: the line joining both photodiodes 201 and 202 being horizontal and perpendicular to the rear projection screen 252.

A white field was projected on the rear projection screen while a test sequence was displayed on the LCD display.

Figure 26 gives results for a system where the lateral screen is a front projection screen. The dimensions of the screens are 350 cm by 200 cm. The gain of the screen was estimated to be approximately 0.7. The device 200 is represented with the line joining the two photodiodes being horizontal and perpendicular to the projection screen. The device 200 was positioned at x=0.25 L; 0.5 L and 0.75 L in a direction parallel to the screen and at a distance L from the screen. The screen to which the viewer would be facing would be at an angle (e.g. perpendicular) to the display surface 261 (either on the lfet or on the right). In the test, the " front" screen was an LCD screen placed either to the left or to othe right of 261 and perpendicular with it or with an angle > 90 degrees. On figure 26, the ratio 11/12 is indicated next to the positions marked by a cross "x". The test results of figure 26 show that the ratio is favorable to the Pulfrich effect at positions most likely to be occupied by a viewer, i.e. the three ratios 2, 3 and 3 at x=0.75L, x= 0.5L and x=0.25L , with y = L for all three, respectively.

The test sequence used to evaluate the perception of depth caused by the Pulfrich effect was similar to that of figure 13: colored squares moving in different directions (from right to left, from left to right and from top to bottom) on a black background. The side of a colored square is less than one 20^th of the side of the LCD display. The speed was varied from zero to more than 1000 pixels per second.

For both cases depicted on figures 25 and 26, a test subject (whose pupil line was parallel to the local horizontal) reported the perception of depth according to what is expected with the Pulfrich effect. With the lateral screen 252 on the right of the viewer:

- Objects moving from the left to the right on the screen 251 in front of the viewer appeared to be farther away from the viewer than the objects moving from top to bottom, the latter being perceived to be in the plane of the display surface.

- Objects moving from the right to the left on the screen 251 in front of the viewer appeared to be closer from the viewers than objects moving from left to right and objects moving from top to bottom.

With the lateral screen 252 on the left of the viewer: - Objects moving from the right to the left on the screen 251 in front of the viewer appeared to be farther away from the viewer than the objects moving from top to bottom the latter being perceived to be in the plane of the display surface.

- Objects moving from the left to the right appeared to be closer from the viewer than objects moving from left to right and objects moving from top to bottom.

No absorption of light at the level of the eyes was required to induce the Pulfrich effect.

The amplitude of the effect depended on the position of the viewer (the higher the ratio 11/12, the more pronounced the effect).

During the tests, it appeared that the eyes of a test subject did not respond identically to the same amount of light. It looked as if the right eye collected more light than the left eye. It was possible to cancel this asymmetry by illuminating the left eye with an image displayed on a display positioned to the left side of the test subject. This amounted to "biasing" the left eye of the viewer. This underlines the fact that when Look-up Tables are used to determine the conditions under which the Pulfrich effect will be induced and a desired 3D effect realized; different viewers may still perceive the effect differently. The display system may be re-calibrated by using test sequences and the device 200 to determine under which illumination conditions those viewers will perceive a desired 3D effect. The test subject affected by the asymmetry reported that, at low ratio 11/12, the Pulfrich effect was erratic but was still present.

In one test, identical absorbing filters were used in front of the two eyes at the same time in order to decrease the amount of light received by both eyes. Inter eye illumination disparity was still induced by modulating the distribution of light across the display surface. As expected, the amplitude of the Pulfrich effect was greater. Indeed, as reported by Albert Lit in "THE MAGNITUDE OF THE PULFRICH STEREOPHENOMENON AS A FUNCTION OF BINOCULAR DIFFERENCES OF INTENSITY AT VARIOUS LEVELS OF ILLUMINATION", the amplitude of the Pulfrich effect increases at lower levels of illumination.

Other examples of display surfaces are given on figures 22a to 22e.

For each of these examples we will explain in detail how the Pulfrich effect can be induced according to the present invention.

In each of these examples: A first sequence of images is projected in a first part of a display surface, the first part of the display surface being visible by both eyes of a viewer;

A second image or sequence of images is projected simultanesouly to the first sequence of images in a second part of the display surface, the second part of the display surface being in a monocular field of view of the viewer;

Be ill, the amount of light emitted by the first part of the display system and reaching both eyes of the viewer and be il2 the amount of light emitted by the second part of the display surface and reaching one of the eye of the viewer (by reflection, some of the light can also reach the other eye of the viewer).

- If thhe first sequence of images comprises at least one picture element moving across the first part of the display surface, the movement having a non zero component parallel to the pupil line of the viewer, and if the ratio (ill+il2)/ill is high enough to induce the Pulfrich effect, the viewer will perceive the at least one picture element as if it were closer or further away from the viewer than the display surface. When required, a louver positioned on the nose of the viewer to increase inter-eye illumination disparity by limiting the field of view of each eye to the opposite side: the louver limits the field of view of the left eye to the right and the louver limits the field of view of the right eye to the left. In Example 1 of figure 22a, two liquid crystal displays 221 and 222 are used.

A viewer 223 is facing the first display 221 and images displayed on the first display 221 are visible to both eyes 224 and 225 of viewer 223.

A first sequence of images is displayed on the first display 221.

A second image or sequence of images is displayed simultaneously or concurrently to the first sequence of images on the second display 222. The second display screen is in the right monocular field of view 226 of viewer 223.

Ignoring reflections on e.g. walls, the amount of light reaching the eyes is:

For the left eye of viewer 223: LL = light emitted by display 221 and reaching the left eye of viewer 223.

- For the right eye: LR = the light emitted by display 221 and reaching the right eye of viewer 223 + light emitted by display 222 and reaching the right eye of viewer 2.

The difference in amount of light received by the right eye and the left eye of viewer 2 is thus LR - LL = the amount of light emitted by display 223 and reaching the right eye, which is different from zero when images are displayed on the display screen 223. We therefore fulfill the first condition for the Pulfrich effect: inter-eye luminance disparity. The amount of light reaching the left eye and the right eye can be evaluated with a device 200. As the amplitude of the inter-eye luminance disparity increases, the amplitude of the Pulfrich effect will increase. If the images of a moving object are displayed on display 221, the movement having a component parallel to the line joining the left eye and the right eye of viewer 223, the second condition for the Pulfrich effect is fulfilled and the viewer 223 will perceive the moving object as if it were closer than the display 221 or farther away than display 221 in function of the direction (left to right or right to left) in which the object is moving on the display surface of display 221.

In Example 2 of figure 22b, a projector 230 projects images on walls 229a and 229b meeting at a corner 229 of a room.

The projector 230 projects a first sequence of images 227 on wall 229a and at the same time an image or sequence of images 228 on wall 229b.

In the example shown figures 22b and 22c, the image of an asteroid 232 is moving from left to right on wall 229a within the binocular field of view of viewer 223. At the same time, an image 228 of a brighter object, e.g. a sun 233 is projected on wall 229b. The image 228 can be static or dynamic.

The image 228 is in the right monocular field of view 226 of viewer 223.

A perspective view of the walls and the projected images is shown on figure 22c. The leftmost boundary of the right monocular field of view 226 is indicated by the dashed line 231 on wall 229b.

In example 3 of figure 22d a curved display surface is used (as e.g. a cylindrical screen or an hemispherical "dome" rear projection screen). The display surface 240 is a rear projection screen. Two or more projectors 241, 242, 243 project images on the back projection screen 240.

As in the previous example, inter-eye illumination disparity is obtained by projecting a first sequence of images in the binocular field of view of the viewer 223 and a second image or sequence of images in a monocular field of view 226b of the viewer 223.

In order to further exemplify the advantages of using a louver, figure 22d shows the wider monocular field of view 226b that can be obtained by positioning a louver 250 on the nose of the viewer as illustrated on figure 23.

As an example, let us consider a simulator in an amusement park.

To set-up the display system of figure 22d, test subjects #1, #2, #3... each look at the images of an asteroid 232 moving across the surface of the rear projection screen 240. Keeping their gaze on the central part of the screen

Each test subject can control the light sources of projectors 241, 242 and 243 with e.g. control knobs. For the sake of simplicity, we will discuss an example where projector 241 hardly projects any light (e.g. a few dim pinpoint-like stars are projected by projector 241).

As a sequence of images 227 is projected by projector 242, a test subject is requested to keep looking in direction A to make sure that the images projected by projector 243 remain in the right monocular field of view of the test subject. The brightness of the images 227 projected by projector 242 can be controlled with a first control knob. The brightness of the images 228 projected by projector 243 can be controlled with a second control knob. The control knobs are either graduated in known units (e.g. the maximum luminance that can be expected at that setting when a white field is projected), relative units (e.g. a scale from 1 to 10 as is for instance the case with a projector B1M from ASUS) or even Fuzzy terms like VERY DARK, DARK, MEDIUM, BRIGHT, VERY BRIGHT and known from Fuzzy Logic.

Each test subject in turn can modify the settings of projectors 142 and 143 to optimize the Pulfrich effect. A look-up table is preferably generated for each test subject (as e.g. can be the case for an arcade game where a player can personalize the game by saving settings of the game and/or the display system. The settings are advantageously retrieved every time the player uses the arcade game).

Alternatively for a given brightness setting of the projector 142, the test subjects can adjust the brightness settings of projector 143 only. For each test subject, the setting of projector 143 is recorded in a look-up table.

Different image sequences 227 are displayed, each sequence illuminating the face of the test subject differently. Each sequence of images 227 is characterized by at least one quantitative parameter or a qualitative parameter.

Examples of quantitative parameters that can be used are:

- The lowest of the two output signals of a photo- sensor device 200 positioned at the emplacement of the head of the test subject. Alternatively, the photodiodes can be positioned close to the eyes of the test subject. The parameter can be e.g. the maximum value measured by the least illuminated photodiode during the image sequence 227 (in other words, the contribution of image 227 only to the photo- sensor outputs). The parameter can also be an average or median value of the signal measured by the least illuminated photodiode during the image sequence 227.

- A "weighted luminance" i.e. the product of the maximum luminance achieved on screen by projector 142 when a white filed is projected (e.g. 50 or 100 cd/m²) and the average pixel value for that image sequence.

An example of qualitative parameter is borrowed from fuzzy logic: VERY DARK, DARK, MEDIUM, BRIGHT, and VERY BRIGHT.

The value of the parameter is either determined by a controller or by the test subject.

In an embodiment according to the present invention, a controller can be a human operator that e.g. keep records of the parameter that characterizes a scene or a data processing unit like a computer that can e.g. compute the weighted luminance of a sequence of images 227 for a given display system by computing the average pixel value or capturing the readings of a photo-sensor device like the device 200. The controller can also adjust the images projected (e.g. the brightness setting of a projector or even the image data) in function of a look-up-table in order to optimize the Pulfrich effect or as a function of the readings of the photo sensor device. In the second embodiment the photosensor device is configured to communicate with the controller. The adjustment can be done in real time or can be done in post-production. If done in post-production, the adjustment required can be stored as meta-data together with the image data. If necessary, the meta-data can be made theater dependent (since different wall covers and screens can impact the light distribution and as a result the inter-eye illumination disparity...).

Alternatively the test subject can enter a quantitative parameter when prompted by the controller.

Once the parameter P0 characterizing a sequence of images 227 has been determined, the test subject can modify the settings, e.g. the brightness of the image projected by projector 143. Once the test subject deems the result satisfactory, the brightness setting B0 of the projector is saved. Next to the brightness settings, the image data can be modified (modify the pixel value and/or the color point and/or any other image characteristics that will affect inter eye illumination disparity.

The results obtained for a group of test subjects can be processed to generate a look-up table like the one of Table 1 In the example of Table 1 the parameter P is qualitative and the brightness setting ranges from 1 to 10 as is the case for projectors like e.g. the B1M from ASUS.

Table 1

It may not always be possible to induce the Pulfrich effect satisfactorily when the sequence of images 227 in the binocular field of view of the viewer 223 is too bright. If the inter eye illumination disparity is monitored in real time, e.g. with a photo-sensor device 200 or by means of a photo-sensor positioned on the face of a viewer (e.g. a pilot or game in a simulator and wearing a helmet to increase the immersiveness of the simulation), the controller can adjust the brightness setting of the projector 143 in function of the measured inter eye illumination disparity.

In normal use, the attention of a viewer 223 is drawn to the sequence of images 227 by use of a visual and/or audio cue. The audio cue is preferably generated by a directional sound system like e.g. Auro-3D or IOSONO's wave field synthesis. Sounds generated by these technologies can be made to appear as if originating from a given point of the display surface and in particular the moving object in the sequence of images 227.

By drawing the attention of viewer 223 in a specific direction, the controller has a good estimate of which part of the display surface is in the binocular field of view and which part of the display surface is in the (right) monocular field of view of viewer 223. If the images projected by projector 143 can be modified on the fly by the controller, the image content of images 228 can be modified to exclude most or all bright pixels that would not be in the (right) monocular field of view 226 (or 226b when a louver 250 is used).

In the example 4 of figure 22e, 22f and 22g, three front projection screens 261, 262 and 263 are positioned next to each other as in an Escape display system.

In figure 22e, the viewer 223 looks at the central screen 262. In that case, images projected on the lateral screen 263 are in the right field of view 226 (or 226b when a louver 250 is used) of the viewer 223. Images 228 projected on the right lateral screen 263 can be used to generate inter eye illumination disparity when an image sequence 227 is projected on the central screen.

Similarly, images 228 projected on the left lateral screen 261 can be used to generate inter eye illumination disparity when an image sequence 227 is projected on the central screen.

In figure 22f, the viewer 223 looks at the left screen 261. In that case, images projected on the central screen are in the right field of view 226 (or 226b when a louver 250 is used) of the viewer 223. Images 228 projected on the central screen 262 can be used to generate inter eye illumination disparity when an image sequence 227 is projected on the left lateral screen 261.

In figure 22g, the viewer 223 looks at the right lateral screen 263. In that case, images projected on the central screen are in the left field of view 256 (or 256b when a louver 250 is used) of the viewer 223. Images 228 projected on the central screen 262 can be used to generate inter eye illumination disparity when an image sequence 227 is projected on the right lateral screen 262.

In a fifth example seen on figure 22h, a single planar projection screen can be used.

If the projection screen is large enough, some parts of the display surface can be in a monocular field of view of the viewer while other parts of the display are in the binocular field of view of the viewer. These examples illustrate how the Pulfrich effect can be induced by modulating the brightness of images displayed on a display surface:

In the display system of Example 4, directional screens can be used to further improve the system. Examples of such screens are described in e.g. WO2015036501 "Multiscreen projector settings" which is incorporated herewith in its entirety. The lateral display surfaces 261 and 263 are each at an angle to the front display surface 262 and can be configured so to reflect light projected onto them predominantly or exclusively in one or more angular ranges that do not intersect with the first display surface 262. The lateral screens can for instance be lenticular screens.

Indeed such directional screens decrease the cross talk between the lateral screens and the central screen as well as better direct the light of a lateral screen towards the corresponding eye of the viewer 223 (i.e. light from the lateral screen on the right of the viewer towards the right eye of the viewer and light from the lateral screen on the left of the viewer towards the left eye of the viewer). With directional screens, there will be less reflections (that can be considered as stray light) which will help increasing the inter-eye illumination disparity.

As was the case with the Liquid Crystal displays, the difference in light intensity illuminating the right eye and the left eye is preferably a factor 5 and preferably a factor 10 to induce the Pulfrich effect significantly. A lower difference in light intensity may still induce a Pulfrich effect albeit not as pronounced. At least one test subject reported a difference in how he perceived the images and that the moving pictures appeared more lifelike with lateral illumination than without lateral illumination. This indicates that a positive impact on the viewer's experience may be expected as long as light emitted by one of the lateral screens will illuminate preferentially one of the eyes of the viewer as described earlier. In particular, in a theater, viewers located at different positions with respect to the screens may experience the Pulfrich effect (for images like the first sequence of images projected on e.g. the central screen) differently but they are expected to perceive it at various degree as long as the lateral screen on their left is in the monocular field of view of their left eye and/or as long as the lateral screen on their right is in the monocular field of view of their right eye. A higher difference between the light intensity illuminating the (retinas of the) left eye and the right eye by a factor 10 or more will induce a more pronounced effect. Such differences in light intensity are for example achievable either for very dark central images and / or for displays with high and very high dynamic ranges (for example with minimum luminance lower than 5 and preferably 1 cd/m2 and maximum luminance higher than 50 cd/ m2 and preferably higher than 100 cd/m2). This is expected to be the case for large LED displays used in lieu of projection screens, tiled LCD displays and new generations of HDR (High Dynamic Range) projection displays for which the maximum luminance is at least 100 cd/m2.

In another example of embodiments, different types of displays are used: the central display 1 can be a projection screen and the lateral screens can be LCD displays or LED displays.

In order to evaluate whether or not variation in luminance (to be expected with moving pictures) on the lateral screens would impact negatively the Pulfrich effect, tests were carried out with simple patterns. In a first test, the luminance of a lateral screen was cycled by displaying a black image all over the lateral screen for a time interval Tl followed by a white image all over the lateral screen for a time interval T2. The first black image is shown on figure 27 and the second white image is shown on figure 28. The flickering on the lateral display surface (e.g. 263 in figure 22e or 172 on figure 18) was described as irritating by one test subject, regardless of the configuration for the central display surface and the lateral display surface. The Pulfrich effect was seriously affected for Tl > Is, moving objects being alternatively perceived in front of the screen (when the image on the lateral display surface was bright) or within the plane of the screen (when the image on the lateral screen was dark). The Pulfrich effect was somewhat affected for Tl between 0.5 s and Is and the Pulfrich effect being less and less affected as Tl further decreased below 0.5 s.

Tests were also carried out where the average luminance of the image displayed on screen was more or less constant even though the image varied with time. In the tests, a first image was displayed for a time Tl and was followed by a second image for a time T2 and the sequence was repeated for up to 30 seconds. In those tests, Tl was always equal to T2.

In those tests, the test subject reported that the sequence of images displayed on the lateral screen affected the perception of the Pulfrich effect less and less as the distance between the lateral screen and the test subject (e.g. the viewer 223 on figure 22e) increased. In particular, this was true for the images seen on Figures 29 and 30 (where the left half of the screen is white and right half of the screen black for a time T and the left half of the screen turns black and the right half of the screen turns white for a time T).

The distance between lateral display and test subject had less and less impact on how the Pulfrich effect was perceived when the "patches" of images for which the luminance varied were small when compared to the area of the lateral display surface within the monocular field of view of the viewer on the same side as lateral display surface. For instance, cycling through images seen on figure 31 and 32 had less impact than cycling through images seen on 33 and 34. A test subject reported that cycling through images seen on figure 35 and 36 had hardly any effect.

The impact of the distance between the lateral display and the corresponding eye of the viewer is linked to the monocular field of view of that eye. Indeed, in an extreme case, with images like those on figure 29 and 30, depending on the precise position of the viewer facing the central display, the eye will see the white (bright) part of the image (and not the other half) for T second and will see the black (dark) part of the image for the next T seconds. As the distance between the viewer 3 and the lateral display (e.g. 172 on figure 18) increased, the entire image displayed on the lateral display was within the monocular field of view of the eye on the same side of the viewer as the lateral screen. The luminance over the entire screen of display 172 being constant, so is more or less the intensity of the light reaching the retina of the eye. The test subject reported that in those cases, even long T had little or no impact on the perception of the Pulfrich effect, moving objects were clearly perceived in front of the screen as if the image on the lateral display was not changing. In a theater, where large screens are used, one should thus avoid large variations of luminance over large surfaces for scenes in which the Pulfrich effect is to be used (this remark applies first and foremost to the display surface in a monocular field of view). This is to avoid that the part of e.g. the lateral screen in the field of view of at least one viewer close to the lateral screen would be predominantly filled in by a part of the screen where large variations of luminance will occur (hence the inter-eye illumination disparity would fluctuate between values that are enough to induce the Pulfrich effect and values that are not enough to induce the Pulfrich effect and this during a scene for which an uninterrupted Pulfrich effect is desired for a given time interval).

Items

Embodiments of the present invention relate to the following items:

1. A display system comprising a first display for displaying images for a viewer looking at the display; a first light source positioned on the left side of the viewer and a second light source positioned on the right side of the viewer, wherein the first and second light sources are controlled by a control unit for controlling the amount of light emitted by the first and second light source so as to create 3D images according to the Pulfrich effect by inducing inter-eye luminance disparity.

2. A display system according to item 1 further characterized in that the amount of light reaching an eye of the viewer is at least twice the amount of light reaching the other eye of the viewer.

3. A display system according to item 1 or 2, wherein the amount of light reaching an eye of the viewer is at least 5 times the amount of light reaching the other eye of the viewer.

4. A display system according to any previous item further characterized in that the first light source is in the right monocular field of view of the viewer and the second light source is in the left monocular field of view of the viewer. A display system according to any previous item, wherein the display surfaces comprise at least one of an LCD, an LED, a projection screen, a back projection screen, an LED wall, a CRT or a plasma fixed format display. A display system according to any previous item, wherein the first and second light sources emit at least one of white, red, green, blue light or any combination thereof. A display system according to any previous item, wherein the at least one of the first and second light sources is positioned in a proximity of respectively the left and right eye. A display system according to item 7, wherein the at least one light source is positioned adjacent to the lateral cantus, at the level of or below the lateral hooding area of the eye, or at the level of or below the lower eyelid or close to the medial canthus. An arrangement comprising a display system according to any of the items 1 to 8, wherein the control unit is adapted to receive command signals correlated to the displayed images according to the horizontal moving direction of the at least one object. Arrangement according to item 9, wherein said command signals are transmitted by at least one of infrared light, or radio wavelengths or ultrasonic or infrasonic sound. Arrangement according to item 9 or 10, wherein at least one of the first and second light sources for inducing inter-eye luminance disparity is positioned in a monocular field of view of respectively the left and right eye. Arrangement according to any of the items 9 to 11, wherein the arrangement is installed within a cinema, a theatre, an opera, a conference room, a concert hall, in a room or an outdoor cinema at night. 13. A device for viewing three-dimensional effects in at least one motion picture displayed on at least one display surface, the device comprising :

first means for increasing the amount of light entering the right eye of a viewer compared to the amount of light entering the left eye when at least one object in images displayed on the at least one display surface is moving generally in a horizontal direction ,

second means for increasing the amount of light entering the left eye of the viewer compared to the amount of light entering the right eye when at least one object in images displayed on the at least one display surface is moving generally in a horizontal direction,

wherein the first and second means for increasing the illumination are controlled by a control unit for controlling the amount of light entering the left and right eye so as to create 3D images according to the Pulfrich effect by inducing inter-eye luminance disparity.

14. Device according to item 13, wherein the first and second means for increasing the amount of light comprise at least one light source positioned in a proximity of respectively the left and right eye.

15. Device according to item 13 or 14, wherein the control unit is adapted to receive command signals correlated to the displayed images of the at least one motion picture according to the horizontal moving direction of the at least one object.

16. Device according to item 15, wherein said command signals are transmitted with an invisible light, radiofrequency waves.

17. Device according to item 15, wherein said command signals are transmitted by at least one of ultrasonic sound, or infrasonic sound.

18. Device according to any of items 14 to 17, wherein at least one of the first and second light sources is positioned in a monocular field of view of respectively the right and left eye. Device according to any of the items 14 to 18, wherein the at least one light source is a solid state light source or is an incandescent source. Device according to any of the items 14 to 19, wherein said at least one light source emits at least one of white, red, green, blue light or any combination thereof. Device according to any of the items 14 to 20, wherein said at least one light source is a set of discrete LEDs associated to a diffuser or a multicolor LED. Device according to any of the items 14 to 21, wherein the at least one light source is positioned in a proximity of respectively the left and right eye. Device according to item 22, wherein the at least one light source is for positioning adjacent to the lateral cantus, at the level of or below the lateral hooding area of the eye, at the level of or below the lower eyelid or close to the medial canthus. Device according to any of the items 14 to 23, wherein the first and second light sources are mounted or attached by fixing means to a support structure adapted to maintain the first and second light sources in a constant position relative to the head of the viewer. Device according to item 24, wherein the support structure is one of a tiara, hard headband, cloth headband, plastic headband, wherein the headband goes over or behind the head, headphones, earphones, glasses, goggles, security glasses, hat, helmet, head accessory, or any type of hair accessory. Device according to item 24 or 25, wherein the support structure is configured to maintain a louver, which, when the support structure is placed on a viewer's head, the louver is positioned close to the root and/or dorsum of the nose. Device according to any of the items 13 to 26, wherein the control unit is configured to be attached by fixing means or is mounted to said support structure.

28. Device according to any of the items 13 to 27, wherein a mobile phone is used to receive command signals and control the first and second light sources.

29. Device according to any of the items 13 to 28, wherein said device is used in conjunction with a Barco Escape™ projection system comprising a first and second lateral screens and a third main screen . 30. Device according to any of items 14 to 29, wherein the color of the at least one light source is selected to match a color of the images projected on the first and/or second lateral screens.

31. Device according to item 29 or 30, wherein the first and second light sources comprise means for collecting light emitted by the first and second lateral screens of the Barco Escape™ projection system.

32. Device according to item 31, wherein the means for collecting light emitted by the first and second lateral screens comprise a hollow or full light funnel.

33. Device according to any of the items 13 to 32, wherein first and second means for increasing the amount of light entering the right and left eye respectively of a viewer compared to the amount of light entering the left and right eye

respectively further comprise a reflecting surface fastened to the support structure of a device positioned adjacent to the root and dorsum of the nose to reflect light into the eye.

34. Device according to any of items 13 to 33, wherein the device further comprises a light sensor for measuring the ambient light.

35. Device according to item 34, wherein the control unit further comprises means to control the intensity of the illumination provided by the means for increasing the light entering an eye as a function of the ambient light provided by the sensor. 36. Device according to any of items 13 to 35, wherein the control unit is further configured to establish a look-up-table in which the delay At induced by inter-eye luminance disparity is evaluated for a set of luminance vales emitted by a light source.

37. Device according to item 36, wherein the look-up table is established for

brightness varying from 0 to a maximum brightness by steps of 10 cd m², the maximum brightness being comprised in the range of 50 to 100 cd m².

38. Device according to item 36 or 37, wherein the look-up table is evaluated for different population groups, to take variations of the visual system from one group of individual to another.

Embodiments of the present invention also relate to the following items:

39. An arrangement of a first, second and third display surfaces on which either or both of still or moving images are to be displayed for viewing by a viewer with a left and a right eye,

the third display surface being positioned in front of the viewer,

the first display surface being positioned so that the viewer has the first display surface on a right side,

the second display surface being positioned so that the viewer has the second display surface on a left side;

a first means for increasing a first ratio of the illumination entering the right eye of the viewer compared to the illumination entering the left eye dependent upon at least one object in images on the third display surface moving generally in a horizontal direction, and

a second means for increasing a second ratio of the illumination entering the left eye of the viewer compared to the illumination entering the right eye dependent upon at least one object in images on the third display surface moving generally in a horizontal direction, and

wherein the first and second means for increasing the illumination are controlled by a control unit for automatically switching between the first and second ratios, so as to create 3D images according to the Pulfrich effect. Arrangement according to item 39, wherein the first and/or second ratio is 5 or more or at least 9 or at least 10. An arrangement according to item 39 or 40, wherein the control unit is adapted to receive command signals correlated to the displayed images according to the horizontal moving direction of the at least one object. Arrangement according to item 41, wherein said command signals are transmitted by fat least one of infrared light, or radio wavelengths or ultrasonic or infrasonic sound

Arrangement according to any of items 39 to 42, wherein the first and second means for increasing the illumination further comprise at least one light source positioned in a monocular field of view of respectively the left and right eye. Arrangement according to any of items 39 to 43, wherein the at least one light source is any of the first to third display surface. Arrangement according to any of items 39 to 44, wherein the display surfaces comprise at least one of an LCD, an LED, a projection screen, a back projection screen, an LED wall, a CRT or a plasma fixed format display. Arrangement according to any of the items 39 to 45, wherein a louver is provided for positioning on the dorsum of the viewer's nose Arrangement according to any of items 39 to 46, wherein the at least one light source is an incandescent source. Arrangement according to any of items 39 to 47, wherein the first means for increasing the first ratio and/or the second means for increasing the second ratio comprises at least one light source. Arrangement according to item 48, wherein said at least one light source emits at least one of white, red, green, blue light or any combination thereof. Arrangement according to any of the items 39 to 49, wherein the first means for increasing the first ratio and/or the second means for increasing the second ratio comprises at least one light source positioned in a proximity of respectively the left and right eye. Arrangement according to item 50, wherein the at least one light source is positioned adjacent to the lateral cantus, at the level of or below the lateral hooding area of the eye, or at the level of or below the lower eyelid or close to the medial canthus. Arrangement according to any of the items 39 to 51, wherein at least one of the display surfaces is a front projection screen. Arrangement according to any of the items 39 to 52, wherein at least one of the display surfaces is a back projection screen. Arrangement according to item 53, wherein the back projection screen comprises multiple back projectors. Arrangement according to item 54, wherein to reduce the depth of the side screens multiple back projection units are provided for projecting a multiple of images on to display surface. Arrangement according to any of the items 53 to 55, wherein the back projection screens are set up for temporary use. Arrangement according to any of the items 39 to 56, wherein the arrangement is installed within a cinema, a theatre, an opera, a conference room, a concert hall, in a room or an outdoor cinema at night. 58. A method for a viewer to visualize 3D images with a left and right eye, the 3D images being displayed in an arrangement of surface displays, the method comprising the steps of

increasing a first ratio of an illumination entering the right eye of the viewer compared to an illumination entering the left eye dependent upon at least one object in images on a display surface moving generally in a horizontal direction, and

increasing a second ratio of an illumination entering the left eye of the viewer compared to an illumination entering the right eye dependent upon at least one object in images on the display surface moving generally in a horizontal direction, and

controlling which of the first and second ratio is select so as to create 3D images according to the Pulfrich effect.

59. A device for viewing three-dimensional effects in at least one motion picture displayed on at least one display surface, the device comprising :

first means for increasing a first ratio of an illumination entering the right eye of a viewer compared to an illumination entering the left eye when at least one object in images displayed on the at least one display surface is moving generally in a horizontal direction ,

second means for increasing a ratio of an illumination entering the left eye of the viewer compared to an illumination entering the right eye when at least one object in images displayed on the at least one display surface is moving generally in a horizontal direction,

wherein the first and/or second ratio is five or more or at least nine and the first and second means for increasing the illumination are controlled by a control unit for automatically switching between the first and second ratios, so as to create 3D images according to the Pulfrich effect.

60. Device according to item 59, wherein the control unit is adapted to receive

command signals correlated to the displayed images of the at least one motion picture according to the horizontal moving direction of the at least one object. Device according to item 60, wherein said command signals are transmitted with an invisible light, radiofrequency waves. Device according to item 60 or 61, wherein said command signals are transmitted by at least one of ultrasonic sound, or infrasonic sound.

Device according to any of items 59 to 62, wherein the first and second means for increasing the first and second ratio further comprise at least one light source for being positioned in a monocular field of view of respectively the right and left eye. Device according to any of the items 59 to 63, wherein the first and second means for increasing the first and second ratio comprise at least one light source. Device according to item 64, wherein the at least one light source is a solid state light source or is an incandescent source. Device according to item64 or 65, wherein said at least one light source emits at least one of white, red, green, blue light or any combination thereof. Device according to any of the items 64 to 66, wherein said at least one light source is a set of discrete LEDs associated to a diffuser or a multicolor LED. Device according to any of the items 64 to 67, wherein the at least one light source is positioned in a proximity of respectively the left and right eye. Device according to item 68, wherein the at least one light source is for positioning adjacent to the lateral cantus, at the level of or below the lateral hooding area of the eye, at the level of or below the lower eyelid or close to the medial canthus. Device according to any of the items 59 to 69, wherein the first and second means for increasing the first and second ratio are mounted or attached by fixing means to a support structure adapted to maintain the first and second means for increasing the first and second ratio comprise in a position relative to the head of the viewer. Device according to item70, wherein the support structure is one of a tiara, hard headband, cloth headband, plastic headband, wherein the headband goes over or behind the head, headphones, earphones, glasses, goggles, security glasses, hat, helmet, head accessory, or any type of hair accessory. Device according to item 70 or 71, wherein the support structure is configured to maintain a louver, which, when the support structure is placed on a viewer's head, the louver is positioned close to the root and/or dorsum of the nose. Device according to any of the items 70 to72, wherein the control unit is configured to be attached by fixing means or is mounted to said support structure. Device according to item 73, wherein the fixing means can be at least one of glue, magnets, clipping mechanism, Velcro™. ... Device according to any of the items 59 to 74, wherein a mobile phone is used to receive command signals and control the first and second means for increasing the first and second ratio. Device according to any of the items 59 to75, wherein said device is used in conjunction with a Barco Escape™ projection system comprising a first and second lateral screens and a third main screen . Device according to any of the items 59 to76, wherein the color of the at least one light source is selected to match a color of the images projected on the first and/or second lateral screens. Device according to item 76 or 77, wherein the first and second means for increasing the first and second ratio comprise means for collecting light emitted by the first and second lateral screens of the Barco Escape projection system. Device according to item78, wherein the means for collecting light emitted by the first and second lateral screens comprise a hollow or full light funnel. Device according to any of the items 76 to 79, wherein first and second means for increasing the first and second ratio further comprise a reflecting surface fastened to the support structure of a device positioned adjacent to the root and dorsum of the nose to reflect light into the eye. Device according to item 80, wherein the reflecting surface is an integral part of a louver for positioning on the dorsum of the nose of the viewer. Device according to any of items 76 to 81, wherein the apparatus is powered and command signals are transmitted by light projected on the lateral screens. Device according to any of items 59 to 82, wherein the device further comprises a light sensor for measuring the ambient light. Device according to item 83, wherein the control unit further comprises means to control the intensity of the illumination provided by the means for increasing the light entering an eye as a function of the ambient light provided by the sensor. Device according to any of the items 59 to 84, wherein light projected can be infra-red light projected by one of the projectors or by a dedicated infra-red projector. Device according to any of the items 59 to 85 used in conjunction with an emissive display. A method of using the device according to any of the items 59 to 86, for viewing three dimensional images according to the Pulfrich effect.

Claims

1. An arrangement of a display surface having a first part and a second part, said first part being configured to be in the binocular field of view of a viewer and at least a portion of said second part being configured to be in the monocular field of view of the second eye of the viewer, said second eye being the left or the right eye, said first eye being the right or left eye, the arrangement comprising means for displaying a first sequence of images in the first part of the display surface, said first sequence of images showing at least one picture element of the first sequence of images at some time in movement wherein the movement has at least a non-zero horizontal component, comprised in the visual plane and parallel to the pupil line of the viewer,

means for displaying a second sequence of images in at least the portion of the second part of the display surface simultaneously with the first sequence, wherein the arrangement is further adapted to display the first and second sequence of images such that the intensity of at least a portion of at least some images of the first or second sequence emitted from the first or second part respectively is such that a ratio of illumination leaving the display surface for entering the second eye of the viewer compared to the first eye is at least of two.

2. An arrangement according to claim 1, wherein a louver configured to be positioned on the dorsum of a viewer's nose is provided so as to increase the monocular field of view of each eye of the viewer.

3. Arrangement according to claim 1 or 2, wherein the ratio of illumination between the second and first eye is preferably at least 5, more preferably at least 9.

4. Arrangement according to any of the preceding claims, wherein the arrangement does not comprise viewer glasses, glasses with polarization filters or with color filters.

5. Arrangement according to any of the preceding claims, wherein the means for adjusting the brightness of at least a portion of each image of the second sequence comprises a controller configured to read calibration data.

Arrangement according to claim 5, wherein the calibration data is provided by test-subjects or a photo sensor device configured to measure intereye illumination disparity, said photo sensor device comprising at least two photodiodes separated by a distance which is substantially the average human intereye distance.

Arrangement according to any of claims 5 or 6, wherein the calibration data comprises at least one of a look-up table storing a parameter related to the brightness setting of a projector and the inter eye luminance disparity, meta-data stored within the image data.

Arrangement according to any of claims 5 to 7, wherein the calibration data depends on at least one of a parameter characterizing a sequence of images, a qualitative parameter determined by a test-subject identifying a brightness level, a quantitative parameter computed with a photo sensor device, the surroundings of the arrangement such as the theater, the test subject, the brightness of the first sequence of images and/or the brightness of the second sequence of images, the horizontal speed of the moving object, the distance between the first part of the display surface and a viewer, the distance between the second part of the display surface and a viewer.

Arrangement according to claim 8, wherein said quantitative parameter comprises at least one of the lowest of the two output signals of a photo- sensor device, the maximum value measured by the least illuminated photodiode for the first sequence of images (227), an average or median value of the signal measured by the least illuminated photodiode for the first sequence of images (227), a weighted luminance measured as the product of the maximum luminance achieved on the first part of the display surface when a white field is projected and the average pixel value for that image sequence, a weighted luminance of a sequence of images for a given display system acquired by computing the average pixel value or capturing the readings of a photo-sensor device.

10. Arrangement according to any of the preceding claims, wherein the adaptation of the intensity of at least a portion of at least some images of the first or second sequence emitted from the first or second part respectively such that a ratio of illumination leaving the display surface for entering the second eye of the viewer compared to the first eye is at least of two is performed during the acquisition of the first and second sequence of images, during film editing, color grading, film production or in real time while displaying the first and second sequence of images.

11. Arrangement according to any of the preceding claims, wherein the adaptation of the intensity of at least a portion of at least some images of the first or second sequence of images in real time is performed by controlling at least one of the brightness setting of the projector, the intensity of at least a portion of the image data of the first and/or second sequence of images, the image data such as the pixel values and/or the color point and/or any other image characteristics which affect inter eye illumination disparity, the image content of the second sequence of images such that most or all bright pixels which are in the monocular field of view of the first eye of the viewer are dimmed.

12. An arrangement according to any of the preceding claims, wherein the inter eye illumination disparity is monitored in real time with at least one of a photo- sensor device such that the displaying of the first and second sequence of images such that the intensity of at least a portion of at least some images of the first or second sequence emitted from the first or second part respectively is such that a ratio of illumination leaving the display surface for entering the second eye of the viewer compared to the first eye is at least of two.

13. An arrangement according to claim 12, further comprising a visual cue and/or audio cue configured to draw the attention of a viewer during the first sequence of images.

14. An arrangement according to claim 13, wherein the audio cue is generated by a directional sound system.

15. Arrangement according to any of the preceding claims, wherein the display surfaces further comprises a third part, said third part being configured to be in the monocular field of view of the first eye of the viewer.

16. Arrangement according to any of claims 2 to 15 wherein the louver is incorporated in opera binoculars, in a mask, in glasses.

17. Arrangement according to any of the preceding claims, wherein the display

surface is at least one of an LCD, an LED, a projection screen, a back projection screen, an LED wall, a CRT or a plasma fixed format display.

18. A method for displaying on a display surface having a first part and a second part, wherein said first part is configured to be in the binocular field of view of a viewer and at least a portion of said second part is configured to be in the monocular field of view the second eye of the viewer, said second eye being the left or the right eye, said first eye being the right or left eye, the method comprising the steps of

displaying a first sequence of images in the first part of the display surface, said first sequence of images showing at least one picture element of the first sequence of images at some time in movement wherein the movement has at least a non- zero horizontal component comprised in the visual plane and parallel to the pupil line of the viewer,

19. A method according to claim 18, wherein the step of adapting to display the first and second sequence of images is performed during the acquisition of the first and second sequence of images, during film editing, color grading, film production or in real time while displaying the first and second sequence of images.

20. A photo- sensor device configured to measure intereye illumination disparity, said photo sensor device comprising at least two photodiodes separated by a distance which is substantially the average human intereye distance.

21. A photo-sensor device according to claim 20, configured to be worn by a viewer.

22. A photo-sensor device according to claim 20, configured to be placed in a display zone of a display system.

23. A photo- sensor device according to claim 22, further configured to communicate with a controller for controlling in real time a first and second sequence of images emitted by a first and second of a display surface.

24. A method for calibrating an arrangement according to any of claims 1 to 17 with a photosensor device according to claim any of claims 20 to 23, the method comprising the steps of

measuring with a photosensor device intereye illumination disparity,

25. A method according to claim 24, further comprising the step of storing in a lookup-table measurements obtained with a photo- sensor device for various locations in a display zone.

26. A method according to claim 24 or 25, further comprising the step of reading the measurements of the photo-sensor device.

27. A display system comprising a first display for displaying images for a viewer looking at the display; a first light source positioned on the left side of the viewer and a second light source positioned on the right side of the viewer, wherein the first and second light sources are controlled by a control unit for controlling the amount of light emitted by the first and second light source so as to create 3D images according to the Pulfrich effect by inducing inter-eye luminance disparity.

28. A display system according to claim 27 further characterized in that the amount of light reaching an eye of the viewer is at least twice the amount of light reaching the other eye of the viewer, preferably at least 5 times, and most preferably at least 9 times.

29. A display system according to claim 27 or 28 further characterized in that the first light source is in the right monocular field of view of the viewer and the second light source is in the left monocular field of view of the viewer.

30. A display system according to any of claims 27 to 29, wherein the at least one of the first and second light sources is positioned in a proximity of respectively the left and right eye.

31. A display system according to any of claims 27 to 30, wherein the at least one light source is positioned adjacent to the lateral cantus, at the level of or below the lateral hooding area of the eye, or at the level of or below the lower eyelid or close to the medial canthus.

32. An arrangement comprising a display system according to any of the claims 27 to 31, further comprising a control unit adapted to receive command signals correlated to the displayed images according to a horizontal moving direction of the at least one object.

33. A device for viewing three-dimensional effects in at least one motion picture displayed on at least one display surface, the device comprising :

34. Device according to claim 33, wherein the first and second means for increasing the amount of light comprise at least one light source positioned in a proximity of respectively the left and right eye.

35. Device according to claim 33 or 34, wherein the control unit is adapted to receive command signals correlated to the displayed images of the at least one motion picture according to the horizontal moving direction of the at least one object.

36. Device according to any of claims 33 to 35, wherein at least one of the first and second light sources is positioned in a monocular field of view of respectively the right and left eye.

37. Device according to any of claims 33 to 36, wherein the at least one light source is for positioning adjacent to the lateral cantus, at the level of or below the lateral hooding area of the eye, at the level of or below the lower eyelid or close to the medial canthus.

38. Device according to any of claims 33 to 37, wherein the first and second light sources are mounted or attached by fixing means to a support structure adapted to maintain the first and second light sources in a constant position relative to the head of the viewer.

39. Device according to any of claims 33 to 38, wherein said device is used in

conjunction with a Barco Escape™ projection system comprising a first and second lateral screens and a third main screen .

40. An arrangement of a first, second and third display surfaces on which either or both of still or moving images are to be displayed for viewing by a viewer with a left and a right eye,

the third display surface being positioned in front of the viewer,

a first means for increasing a first ratio of the illumination entering the right eye of the viewer compared to the illumination entering the left eye, dependent upon at least one object in images on the third display surface moving generally in a horizontal direction, and

wherein said illumination is emitted by at least one of a light source, the first display surface, the second display surface to directly enter the left or right eye of the viewer, and wherein the first and second means for increasing the illumination are controlled by a control unit for automatically switching between the first and second ratios, so as to create 3D images according to the Pulfrich effect.

41. Arrangement according to claim 40, wherein the first and/or second ratio is 5 or more or at least 9 or at least 10.

42. A method for a viewer to visualize 3D images with a left and right eye, the 3D images being displayed in an arrangement of surface displays, the method comprising the steps of

- increasing a second ratio of an illumination entering the left eye of the viewer compared to an illumination entering the right eye dependent upon at least one object in images on the display surface moving generally in a horizontal direction, and

43. A device for viewing three-dimensional effects in at least one motion picture displayed on at least one display surface, the device comprising :

44. Device according to claim 43, wherein said device is used in conjunction with a Barco Escape™ projection system comprising a first and second lateral screens and a third main screen.

45. A method of using the device according to claim 43 or 44, for viewing three dimensional images according to the Pulfrich effect.