DE4125241A1 - Laser projector deflection with system - projects stereoscopic 3=d image as partial picture sequences to right and left eye alternately using deflector - Google Patents

Abstract

The laser projector still or moving image is transmitted as consecutive sequences of image parts for the right and the left eye alternately by means of the deflection system (3). Two different values of an optical parameter of the laser light (1) incident on the deflector (3) are allocated respectively to the right and the left eye. The optical parameters are allocated such that on switching between the right and left eye, a selector for the parameter associated with this eye is also switched over in a coding device (2). Thus, on viewing the sequences of image parts to each eye through filter spectacles the image parts with the optical parameter allocated to one eye are allowed through but those allocated to the other are blocked. ADVANTAGE - Obtains very concise stereoscopic effect with greater spatial resolution.

Description

The invention relates to a laser projector in the Oberbe handle of claim 1 specified type.

Devices are referred to as laser projectors at which a laser beam is defined by suitable means in  two directions that are not perpendicular to a plane perpendicular to the directed laser beam, is deflected. Prefers An arrangement of is used as a deflection device two mirrors pivotable about orthogonal axes, whereby the mirrors are operated by galvanometer scanners.

The laser beam can pass through before it is deflected suitable means amplitude-modulated and / or in its spectral composition defined influenced. The like laser projectors are known and have because of their ability to display colored, luminous images to project almost any surface, a wide one Spread in the light show area and in the advertising the.

As a method for stereoscopic imaging using La radiation is the so-called "holography process" became known. However, this method is not suitable stereoscopic images for a larger view generating circle.

Different techniques for generating stereoscopic images so far they have been used in film and television. However, these are not suitable for laser performances.

From an object by two cameras or by computational methods two (film, video, computer) bil that produces those that are similar to those that the right or left human eye would perceive of the object.  

These two images are ko in a suitable way dated and the viewer simultaneously on a screen or canvas shown. With an appropriate coding it is possible to separate the images so that only the image intended for the right eye into the right one Eye of the beholder and that intended for the left eye Image gets into the viewer's left eye.

With all techniques, the one for spatial vision man's necessary information is simultaneously available poses. The pair of human eyes takes up the space depth of an object is true in that the of images of the object observed in the individual eyes appear from slightly different angles.

Different techniques for generating stereoscopic images so far they have been used in film and television. However, these are not from the beginning for laser performances suitable in.

Common to all known 3D rendering processes is that of an object by two cameras or by computing methods (two film, video, computer) images who are similar to those who have the right or left human eye would perceive of the object.

With all techniques, the one for spatial vision man's necessary information is simultaneously available poses. The pair of human eyes takes up the space depth of an object is true in that the of  images of the object observed in the individual eyes appear from slightly different angles.

The two images come together in the cinema projection projected onto a screen. The prerequisite for this is ent neither the waiver of information by reduction to a black and white representation and selection of the lin ke and the right eye certain image by means of Red / green color filtering (amalglyph process) or else a simultaneous projection if desired color rendering by means of two in their optical properties corresponding projectors and information selection using polarization of light and appropriate filters viewer.

These possibilities do not apply to laser projection because on the one hand, only a point-by-point representation is possible and on the other hand, a superimposed representation of two laser images the due to a lack of conformity of the deflection units two different projectors do not form an image leads to a three-dimensional Dar for the viewer of sufficient quality.

Methods are also known from television technology which also three-dimensional representations deliver. On the one hand, the process with red Green filtering used. Also with the television picture here even with the line-by-line scanning still a layer tion of the two colors created for the viewer excerpts made in black and white parts of the picture, whereby the portion causing the stereoscopic display presents itself in the form of color fringes.  

Here, too, there is a difference to laser projection in that the objects to be displayed in the last cannot be reproduced across the board.

A stereoscopic color reproduction of television pictures Spectators sitting freely in front of a screen or stand, is currently with that at stereoscopic display normal quality not possible. Are just off Process known which has certain pseudo stereo effects cause, such as that in EP-A-03 25 019 described method, which with a one opposite the other glass has slightly darkened glass send glasses works. Here are certain horizontal Movement effects perceived by the viewer as spatial.

The invention has for its object in a laser projector of the type mentioned in the one also stereoscopic accessible to a wider audience Representation should be generated.

This task is carried out with the characteristic features of the Claim 1 solved.

The invention is based on the finding that with image given by a free line a stereoscopic Representation by alternative use of the same laser rays with synchronous assignment of both the Ab steering means as well as the picture the left or right Eye-catching coding means a high quality stereoscopic display is possible. Such a thing The procedure is for cinema or television picture display  not possible because of a flat image display with single exposure of each point of the image area per Run out picture. In the method according to the invention individual parts of the picture surface are touched several times will.

It is particularly advantageous that without special Ju a very concise stereoscopic ef is fectively achievable, since all deflection devices ever because they just have to be there so that the two Representation assigned to one eye of the viewer leads to an almost exact stereo image, which gives a realistic spatial impression.

It is particularly favorable if the partial images are pure Li form train representation, because then an effect of be can achieve moving pictures from "dancing neon tubes".

If parts of the project representing the same object tion image shown in successive sequences are played back promptly, so that a any flickering effect is minimized.

The frame rate is before the moving image display moves according to the change of image in the cinema projection or television picture display adapted.

The coding is preferably carried out after the anaglyphic or the Polaroid process. Here it is possible to both images only after they have been created by the project encoding (e.g. projection through polarization fil  ter the polarization direction not be influential canvas).

With both coding methods, however, the different images generated by the laser projector on the Projection screen are aligned that for the Be watch the two pictures on the screen to coincide with a picture. By the invention Measures can be done with high precision, so that a good spatial impression can be achieved.

This eliminates the previously used two difficulties encountered by different projectors, which consisted of the fact that it is extremely difficult to pivotable mirror of two deflectors, usually operated by galvanometer scanners and subject to certain tolerances as mechanical systems are congruent to deflect.

However, deviations from the ideal match are annoying the desired stereoscopic effect. For mobile systems is sufficient, even if both projectors are not very spacious are separated from each other, an adjustment in Regarding the distance of the projectors from the projection area necessary. In addition, the deflectors are the Laser projectors are relatively expensive.

Because the images for the right and left eyes generated by the same deflection device according to the invention they are subject to the solution according to the invention the same Ver caused by the deflector  strains, so that the stereoscopic effect unimpaired remains.

Since the coding of the laser beam is preferred to the Rich deflection occurs, and the laser beam here generally just has a small beam cross section, it is possible to in the coding device according to the invention before used optical elements small and therefore only to keep low inertia and therefore fast to be able to pivot into the laser beam. Besides, it is possible to use optical devices that are only small Have apertures. Laser projections are common Frame rate of up to several 100 Hz. Here it succeeds in creating still pictures and - there an image for one of the two eyes at all times is visible - becomes the picture repetition too low typical flickering effect not magnified.

The color change required for the anaglyph process a white light laser beam is used in one th execution of the device according to the invention by the Introducing color filters into the laser beam. At a other version, the color is switched by Rotation of a prism or one (reflection or trans mission-) grating in the laser beam, whereby by a fixed aperture fixed the color passed becomes. Another version includes an acousto-opti filter (diffraction of the laser light on one by a acoustic wave generated phase grating in a kri stall, the lattice constant by a control signal is changeable) to define the color of the projected Picture.  

With two separate laser light sources, one of which one red and the other one blue and / or green Laser beam emitted, and their rays through a di chroic color splitter into a coaxial beam an interruption of the red laser is sufficient rays to create a blue / green image and vice versa returns.

For a defined interruption not by his Power supply of modulatable laser beam are several Process suitable: swiveling an aperture into the La laser beam, deflection of the laser beam over a fixed Aperture, electro-optical and acousto-optical modulators.

However, the Polaroid method is preferred since this Procedures colored representations allowed. The one to distract laser beam is either natural or linearly polarized by a polarizer. That beam is used to generate the image for z. B. ver the left eye turns. The deflection device is equipped so that the polarization of the deflected laser beam is different the polarization of the undeflected beam is not below separates. For devices that the laser beam through be can deflect moving mirrors, e.g. B. with aluminum steamed mirrors can be used. To create the image for the other eye the polarization direction of the un deflected laser beam rotated by 90 °. The rotation of the The direction of polarization can be adjusted by swiveling one Half wave plate (delay plate) in the laser beam done. In a preferred embodiment, this is Press the half-wave plate with a galvanometer scanner  does. Because of the small size of the half-wave plate the response speed is high. Half waves plates are available in achromatic versions, so that this method does not refer to only one color (waves length) is limited.

In particular, it is not necessary here - as with ent speaking procedures that work with cathode ray tubes ten - one eyeglass of the glasses by means of complicated to synchronize the synchronization devices darkly.

In another version, the pola is rotated direction of risk in a device that one or several electro-optical crystals such as B. KDP and ADP includes. Electro-optical crystals have the property the direction of polarization of the incident light Apply an electrical voltage to rotate. At a certain voltage, the direction of polarization is ge turned 90 °.

In a further embodiment, the pola is rotated Direction of risk in a device that has at least one egg ne twisted nematic or ferroelectric liquid crystal stall cell includes.

Twisted nematic liquid crystal cells turn off switched control voltage the polarization direction of the incident light by exactly 90 °, while with increasing Control voltage the rotation of the direction of polarization decreases to 0 °.  

In contrast, ferroelectric liquid crystal cells show a rather bistable behavior and turn the Polarisa direction of the incident light depends on the Control voltage by 0 ° or by 90 °.

These non-mechanical processes have the advantage inertia between the two polarization directions to be able to switch.

In a further embodiment, a laser beam arrives next to a mirror that can be pivoted about an axis, the in its rest position the laser beam on a Polarisa tion beam splitter cube reflected so that the by the Splitter cube transmitted beam to the deflecting device tung meets. This transmitted beam is linearly polar rized. In a second, different from the rest position the position of the mirror, the right of this reflected beam over a second fixed mirror to the side of the polarization beam splitter cube, the is orthogonal to the side through which the above transmit tated beam passes through, so that the in the Tei The cube reflects the beam onto the deflection device meets. This reflected beam is also linear polarized and its direction of polarization is lower right to the polarization direction of the above transmitted Beam. By swiveling the mirror between the two positions mentioned can between the polarization be switched back and forth between 0 ° and 90 °. The game gel can be in particular by a galvanometer scanner be done. Since the mirror can be very small, it results high response speed.  

Advantageous developments of the invention are in the Un claims are identified below along with the description of the preferred embodiment the invention with reference to the figures. It demonstrate:

Fig. 1 is a schematic representation of a first example of the invention From guide the laser projector,

Fig. 2 is a schematic representation of a detail of a second embodiment of the laser projector according to the invention,

Fig. 3 is a schematic representation of a detail of a further embodiment of the laser projector according to the invention, and

Fig. 4 is a block diagram of the laser projector according to the invention.

In the laser projector shown in Fig. 1 for generating stereoscopic images, the images intended for the right or left eye are alternately generated by the same deflection device in rapid succession, the laser beam being coded before its deflection so that the Representation when viewed through commercially available red / green or polaroid glasses, it appears spatially.

The incident laser beam 1, which is modulated with the brightness information, is encoded by means of a device 2 - shown in more detail below. The coded laser beam is then deflected directionally by the deflection device 3 . The preferred form of the deflection device 3 comprises two pivotable mirrors 4 , 5 about orthogonal axes 6 , 7 . The laser beam first strikes the lower mirror 4 and is reflected by it against the upper mirror 5 . By a defined rotation of the mirror 4, 5 of the light reflected from mirror 5 the laser beam can be deflected in virtually any direction within the allowed spatial angle range. The two mirrors 4 , 5 are each driven by a galvanometer scanner 8 , 9 , so that the positions of the images for the right or left eye can be controlled depending on the voltage applied.

It will be on a canvas or in a corresponding way reflective medium creates a projection image that from a person who is a corresponding one who timed consecutive information one eye at a time pointing, wearing glasses, can be viewed. This The representations appear to viewers spatially. With Ver it is using differently polarized radiation required that the projection surface reflect the Polarization properties of the incident beam holds.

To generate the image for the other eye by rotating the direction of polarization by 90 ° in an embodiment shown in FIG. 2, a coding device 2 is carried out by pivoting a half-wave plate (delay plate) 10 into the laser beam 1 . In this preferred embodiment, the half-wave plate 10 arranged on a pin 11 is pivotable about an axis 12 and can be actuated by a galvanometer scanner 13 . Because of the small size of the Halbwellenplätt Chen 10 there is a high response speed. Half-wave plates are available in achromatic versions, so that this method is not limited to one color (wavelength). This optical coding can take place either before or after the directional deflection of the laser beam.

In the further embodiment of a coding device 2 shown in FIG. 3, the optical coding takes place in that a laser beam 1 first reaches a pivotable about an axis 15 mirror 14 , the laser beam 16 in its rest position on a first page 20 of a te Polarization beam splitter cube 17 is reflected so that the beam transmitted through the splitter cube 17 hits the deflection device 3 (not shown). This transmitted beam is linearly polarized. In a second, from the rest position NEN position of the mirror 14 , the reflected from this re beam 18 passes via a second fixed mirror 19 to a second side 21 of the polarizing beam splitter 17 , which is orthogonal to the first side 20 through which first transmitted beam passes through, in such a way that the beam reflected in the divider cube 17 strikes the deflection device 3 . This second reflected beam is also linearly polarized and its direction of polarization is perpendicular to the direction of polarization of the first transmitted beam. By pivoting the mirror 14 between the two positions mentioned, it is thus possible to switch back and forth between the polarization directions 0 ° and 90 °. The mirror 14 can in particular be actuated by a galvanometer scanner. Since the mirror 14 can be very small, it gives a high response speed.

In Fig. 4, the control of the laser projector according to the invention is shown using a schematic block diagram. In an image processor 23 , projection images for the right and left eyes are generated computationally one after the other on the basis of the images recorded in a storage medium 22 . Depending on whether the projection image for the left or for the right eye is next delivered by the image processor 23 , a corresponding discrimination signal 24 is emitted, which controls the coding device 2 and switches if necessary, so that the emitted by the laser source 25 Laser beam 1 , which has already been amplitude-modulated by suitable means and / or has been defined in its spectral composition, arrives in the coding device 2 , corresponding to one of the two values of the optical parameters, each representing the projection image for the left or right eye have been permanently assigned, is encoded. Furthermore, the position of the Ablenkvor device 3 , which is used according to the invention to generate both projection images, is also controlled, depending on the projection image to be delivered, by a signal 26 provided by the image processor 23 .

The invention is not restricted in its implementation to the preferred embodiment given above  game. Rather, a number of variants are conceivable which of the solution shown also in principle makes use of different types.

Claims (20)

1. Laser projector with a deflection device for de flexion of a laser beam, characterized in that for generating a stereoscopic (3-D) still or moving image display at least parts of the projection image for the right eye and parts of the projection image for the left eye alternately in time as successive sequences are generated by means of the deflecting device ( 3 ), two different values of an optical parameter of the laser light ( 1 ) striking the deflecting device ( 3 ), by means of which this can be selectively assigned to the left or right eye, respectively are in such a way that with the switching between the sequences for generating the image portion assigned to the respective eye also selection means for the optical parameter assigned to this eye are switched in a coding device ( 2 ), so that an assignment of the sequences to the viewer to the respective eye using filter glasses, passes the image parts with the optical parameter assigned to this eye - but suppresses the image parts with the optical parameter assigned to the other eye - can take place. 2. Laser projector according to claim 1, characterized ge indicates that parts of the projection image  only a line drawing with lines provision of objects or representation of by stri limited areas, corresponding to one with neon lights illustrated image, form. 3. Laser projector according to one of the preceding claims che, characterized in that each parts of the project that represent the same object tion image shown in successive sequences will. 4. Laser projector according to one of the preceding claims che, characterized in that the Moving image display with a frame rate accordingly the change of picture in cinema projection or television picture playback takes place. 5. Laser projector according to one of the preceding claims che, characterized in that the Projection image for one eye only such wavelengths contains which in the projection image for the other eye do not occur. 6. Laser projector according to one of claims 1 to 5, characterized in that the projection images in the coding device ( 2 ) by a color filter inserted into the path of the laser beam ( 1 ) are color codable. 7. Laser projector according to one of claims 1 to 5, characterized in that the projection images in the coding device ( 2 ) are color codable by the rotation of a prism or reflection or transmission grating arranged in the path of the laser beam ( 1 ), the color that is allowed through is determined by means of a fixed aperture. 8. Laser projector according to one of claims 1 to 5, characterized in that the projection images in the coding device ( 2 ) are color codable by an acousto-optical filter, the laser beam at a Pha sengitter generated by an acoustic wave in one Crystal is diffracted and the lattice constant of the crystal can be changed by a control signal. 9. Laser projector according to one of claims 1 to 4, characterized in that the pro jection images in the coding device ( 2 ) are polarized and that the polarization of the projection images for the two eyes is linear and that the polarization directions are perpendicular to each other. 10. Laser projector according to one of claims 1 to 4, characterized in that the projection images in the coding device ( 2 ) are polarized and that the polarization of the projection images for the two eyes is circular and that the polarization directions of rotation are opposite to each other. 11. Laser projector according to one of claims 9 or 10, characterized in that the Än Change in polarization by the electrically induced optical activity of a crystal is effected. 12. Laser projector according to one of claims 9 or 10, characterized in that the Än Change in polarization by the electrically induced optical activity is generated in a liquid crystal. 13. Laser projector according to one of claims 9 or 10, characterized in that the change in polarization by a in the path of the laser beam ( 1 ) before or after its directional deflection inserted half-wave plate (delay plate) ( 8 ) he is witnessed. 14. Laser projector according to claim 9, characterized in that the coding device ( 2 ) has a pivotable about an axis ( 15 ) mirror ( 14 ), a polarization splitter cube ( 17 ) and a further mirror ( 19 ), the laser beam ( 1 ) a first position of the pivotable mirror ( 14 ) is reflected directly on a first side ( 20 ) of the polarization splitter cube ( 17 ) and in a second position of the pivotable mirror ( 14 ) via the further mirror ( 19 ) to a first side ( 20 ) orthogonally arranged second side ( 21 ) of the polarization splitter cube ( 17 ) is reflected. 15. Laser projector according to one of the preceding claims, characterized in that the deflection device ( 3 ) comprises two pivotable mirrors ( 4 , 5 ) about orthogonal axes ( 6 , 7 ). 16. Laser projector according to one of the preceding claims, characterized in that the deflection device ( 3 ) comprises a mirror which can be pivoted about two orthogonal axes ( 6 , 7 ). 17. Laser projector according to claim 15 or 16, characterized in that at least one mirror ( 6 , 7 ) of the deflection device ( 3 ) is driven by a galvanometer scanner ( 8 , 9 ). 18. Laser projector according to one of the preceding claims, characterized in that the deflection device ( 3 ) comprises a pivotable mirror and a rotating polygon mirror, the axes of which are oriented orthogonally to one another. 19. Laser projector according to one of claims 15 to 18, characterized in that at least one mirror ( 6 , 7 , 14 , 19 ) of the deflection device ( 3 ) is provided with a non-depolarizing reflection layer. 20. Laser projector according to one of the preceding claims, characterized in that the deflection device ( 3 ) has at least one acousto-optical deflector.