WO2009024645A1

WO2009024645A1 - Arrangement for distributing radiation

Info

Publication number: WO2009024645A1
Application number: PCT/FI2008/050460
Authority: WO
Inventors: Erkki Rantalainen
Original assignee: Supponor Oy
Priority date: 2007-08-21
Filing date: 2008-08-13
Publication date: 2009-02-26
Also published as: FI20070630A0; FI20070630L

Abstract

An arrangement for distributing radiation, the arrangement comprising a radiation source (1) and a plate-like distributor element (3), positioned in the passage of a radiation beam (2) produced by the radiation source, for distributing the radiation. According to the invention, the radiation beam (2) is oriented at a slight angle to the plane (4) of the distributor element, and the distributor element comprises a plate-like body portion (5) made from a transparent material and reflective surfaces (7) arranged stepwise one after the other and side by side on the body portion (5) in the direction of the radiation beam (2) and at an angle to the plane (4) of the distributor element for dividing the radiation beam into substantially mutually parallel sub-beams (8) in a direction that differs from the direction of the radiation beam.

Description

ARRANGEMENT FOR DISTRIBUTING RADIATION FIELD OF THE INVENTION

The invention relates to an arrangement for distributing electromagnetic radiation produced by a radiation source.

BACKGROUND OF THE INVENTION

There are many applications where it would be necessary to have parallel radiation with uniform in- tensity distribution deriving from a larger area instead of a widening radiation beam with often nonuniform intensity distribution produced by a small radiation source. In many such applications, for example in the case of spotlighting, it would also be advanta- geous if such radiation distributing area was one transmitting visible light wavelengths.

Different spotlighting arrangements are typically based on a practically point-like, or in any case rather small light source, relative to the size of the object. This causes problems for the lighting result itself and for the arrangement of the lighting. When lighting an object encompassing various shapes with a small source, the rays of light fall on different parts of the object from different directions, which may produce unwanted shadows or in other respects non-uniform lighting. On the other hand, the difficulty in producing uniform lighting is also met in lighting planar billboards, when the lighting must be arranged from outside the advertising area, either from close to the advertisement at a very oblique angle, or alternatively from a relatively long distance. In the first case, the particularly complicating factor in smoothing the obliquely directed lighting is that the radiation beam produced by a small or point- like light source must necessarily be clearly widen- ing, in which case the intensity, in addition to the possible directional dependency, is strongly reduced when receding from the source, the radiation being distributed over a larger and larger area. On the ot- her hand, when the light source is placed far from the object, the efficiency of the light source must be increased. Correspondingly, in the case of display windows, the object which may even be quite large, such as a mannequin or a piece of furniture, must be placed at a sufficient distance from the light source in order to expand the light beam produced by the source to be sufficiently large. In addition to the drawbacks in the lighting result itself described above, this requires that high—cost space that is useless as such be arranged between the lamps, typically placed close to the window and directed inwards, and the illuminated obj ect .

When it is desirable to transform radiation produced by a small source into a larger radiating surface, it is known to use for example an opal glass or other functionally similar transmitting or reflecting diffusing plate which transforms a small source into a larger surface radiator. This can also be used for smoothing the radiation coming from a source of non-uniform intensity distribution. However, the diffusing element distributes, following its essential quality, the radiation to a wide angle, so this kind of solution does not aid when substantially parallel radiation is specifically desirable to have produced close to the radiation distributor.

Also known is to direct the lighting produced for example by fluorescent tubes so as to be parallel by placing in front of the sources a grid comprised of thin plates extending in the desired direction of the radiation and in perpendicular directions to that direction, wherein the surfaces may additionally be treated to be absorbent in order to minimize other radiation apart from that in the desired direction. This technique has been applied for example in film studios . In addition to being a mechanically complex and operationally inadequate solution, a further drawback of this solution is that this beam modifier is not transparent either in case where the lamp is set directly behind the radiation distributing plane and is therefore not suitable for situations where it would be desirable to have lighting in alignment with the direction from which the illuminated objet is viewed.

OBJECTIVE OF THE INVENTION

The objective of the invention is to provide an arrangement for distributing radiation, which arrangement can be realized by simple elements and be used for dividing a radiation beam produced by a radiation source into substantially parallel radiation with uniform intensity distribution and produced by a substantially larger area than the original radiation beam, said area being substantially transparent. In this context, uniformity of the intensity distribution means that the intensity may de derived from many areas which are per se separate and set at a distance from each other and wherein the mutual intensities are yet substantially equal.

SUMMARY OF THE INVENTION

The arrangement for distributing radiation according to the invention comprises a radiation source and a plate-like distributor element, positioned in the passage of a radiation beam produced by the radiation source, for distributing the radiation. The radiation source may be, depending on the applica- tion, a conventional incandescent or fluorescent lamp, a light emitting diode (LED) or other equivalent ra- diation source producing electromagnetic radiation on the visible light, infrared or other wavelength.

According to the invention, the radiation beam is directed to be at a slight angle relative to the plane of the distributor element. The direction of the radiation beam refers herein and below to the center line of the beam or, in the case of an asymmetrical radiation pattern, to the main direction of the beam, determined by other means, for example by the maximum intensity. The slight angle means herein an angle which is considerably smaller than 45 degrees, for example less than 25 degrees. It may also be zero degrees in which case the main direction of the radiation beam is parallel to the plane of the distributor element. The plane of the distributor element means the main direction of the plate-like distributor element which may even be slightly curved or of varying thickness .

Further according to the invention, the dis- tributor element comprises a body portion made from transparent material, for example glass or clear plastic, and reflective surfaces arranged on the body portion stepwise one after the other and side by side in the direction of the radiation beam and at an angle to the plane of the distributor element for dividing the radiation beam into substantially mutually parallel sub-beams in a direction which differs from the direction of the radiation beam. The transparent body portion makes it possible to visually perceive an object on the other side of the distributor element, which feature is particularly useful for example in spotlighting applications. The stepwise positioning one after the other and side by side means that, as seen in the direction of propagation of the radiation, the reflective surfaces are set one after the other, yet not directly in alignment with each other but, in- stead, so that they seem to be side by side as seen in the direction of propagation of the radiation beam. More precisely, the reflective surfaces are side by side in the longitudinal direction of the elongated projection, imagined on the plane of the distributor element, of the radiation beam falling at a slight angle to the plane of the distributor element. On the other hand, in the transverse direction of the projection, each reflective surface is preferably equally wide as the radiation beam, extending over the entire width of said projection. The dimensions of the reflective surfaces in a perpendicular direction to this lateral direction are preferably so selected that together, the reflective surfaces cover the entire cross-sectional area of the radiation beam. The direction of the radiation source relative to the distributor element and the orientation of the reflective surfaces may, in turn, be arranged for example so that the sub-beams coming from the distributor element are substantially perpendicular to the plane of the distributor element.

The reflective surfaces may be positioned on the outer surface of the distributor element or alternatively inside the distributor element, in which case the radiation beam is directed so as to propagate along the distributor element. When the reflective surface is positioned on the outer surface of the distributor element, it may be directed so as to reflect the radiation either away from the surface of the dis- tributor element or through the distributor element to the other side thereof. When the reflective surface is positioned inside the distributor element, the cross section of the distributor element may have for example the shape of a wedge tapering away from the radia- tion source in order to direct the radiation propagat- ing inside the distributor element towards the point of the wedge by means of total internal reflections.

Depending on their structure and material, the reflective surfaces may reduce the amount of ra- diatiόn passing through the distributor element. This must be taken into account particularly by sizing and placing the non-transparent reflective surfaces in such manner that the distributor element will not attenuate too much of the radiation intensity. However, in visible light applications, the excellent adaptability of the human eye to the brightness of the lighting reduces the effect of said phenomenon. Therefore, even non-transparent reflective surfaces may, depending on the application, cover for example up to 50% of the plane of the distributor element without this causing too much interference. A smaller coverage of for example 10% does practically not affect much the transparency of the distributor element.

In a preferred embodiment of the invention, the height of the reflective surface in the longitudinal direction of the projection of the radiation beam imagined on the plane of the distributor element is selected to be smaller than the height according to the typical angular resolution of the human eye. Therefore, when looking through the distributor element in a perpendicular direction to the plane of the distributor element, the reflective surfaces are not perceived at all, but instead the distributor element seems to the viewer to be a normal window glass or a transparent plexiglass. This is a very advantageous feature when the arrangement according to the invention is used in different kinds of spotlighting applications. The angular resolution of the human eye is about 0.034 degrees, so when the viewing distance is for example 2 meters from the distributor element, the height of the reflective element must be less than about. 1.2mm. Combined with the above-mentioned 10% coverage of the reflective surfaces over the plane of the distributor element, one preferred sizing, suitable for example for spotlighting applications, is such where the distributor element comprises reflective surfaces not higher than lmm at intervals of at least lcm.

The reflective surface may be, for example, a metalized mirror surface. It is possible to provide high-quality mirror surfaces by metalizing the reflective surfaces arranged in glass or clear plastic. On the other hand, the reflective surface may be a boundary surface between materials of higher and lower optical density set at such angle to the incoming radia- tion that total internal reflection occurs on the boundary surface. The total internal reflectance boundary surface may be, for example, the surface of a projection formed on the surface of the distributor element. On the other hand, the total internal reflec- tance surface may also be a boundary surface between the body portion of the distributor element and a recess formed therein and filled with a material of lower optical density than the body portion in order to reflect the radiation propagating inside the body portion of the distributor element. In this kind of application, the radiation produced by the radiation source is first directed to propagate inside the distributor element, preferably in the direction of the plane of the distributor element. The material of lower optical density may, in the case where the distributor element is made for example from glass, be air at the simplest. The direction of the sub-beams depends, also in the case where the reflective surfaces are surfaces of total internal reflectance, on the direction of the reflective surfaces relative to the direction of the radiation falling thereon. The reflective surface may be slightly curved in order to form the sub-beam as a widening sector. In addition to convexity, the curvature also refers herein to concavity, in which case the sub-beam is first reduced but then widens after the focus as in the case of a convex surface . The curvature may be realized in both lateral and vertical direction of the reflective surface. A widening sub-beam permits smoothing the intensity of the radiation, emitted by the distributor element, in proximity to the distributor element. In practice, the reflective surfaces always scatter light also into a specific sector around the actual mean direction of the reflection, but the intensity of the radiation falling onto an object placed sufficiently close to the distributor element may, in the case of very even reflective surfaces, be distributed in a point-like or linear manner.

Depending on the type of the radiation source and the shape of the radiation beam, there may be a collimator element arranged in front of the radiation source for collimating the radiation beam before the distributor element. One simple element used in colli- mation is for example a cylinder lens . A collimated radiation beam facilitates the realization of the dis- tributor element because, in this manner, the reflective elements may be parallel to each other .

The arrangement of the invention provides numerous significant advantages compared to the prior art. From the operational standpoint, the arrangement of the invention for distributing radiation enables transforming a widening radiation beam from a point- like or small radiation source, in which the intensity is dependent on the direction, into substantially parallel radiation with uniform intensity distribution emitted by a considerably larger area. The invention is advantageous for numerous lighting applications in which, when using point-like light sources, the object would have to be placed at a considerably longer distance from the light source than in the arrangement of the invention, without achieving, however, suffi- ciently uniform and parallel lighting. The transparent distributor element according to the invention may be realized in such manner that the reflective surfaces therein do practically not interfere at all with viewing through the distributor element. In this manner, the distributor element that illuminates the object may simultaneously operate as a window between the object and the viewer. As an essential part of the arrangement of the invention, the distributor element is structurally extremely simple and can be readily real- ized by modern glass or plastic production processes and metalizing techniques. Furthermore, the invention is extremely versatile, being applicable for the most different kinds of spotlighting, indicating or equivalent applications using both visible light and for ex- ample infrared radiation.

LIST OF FIGURES

In the following section, the invention will be described in detail by means of exemplifying em- bodiments and with reference to the accompanying schematic drawings describing the principles of the invention, in which

Fig. 1 is a side view of one arrangement according to the invention, Fig. 2 is a front view of the arrangement of

Fig. 1, and

Fig. 3 to 5 are side views of other arrangements according to the invention.

DETAILED DESCRIPTION OF THE INVENTION The corresponding features in the arrangements of Fig. 1 to 5 are indicated by the same reference numbers in the figures . In order to improve clarity, the dimensions of the parts in the arrangements are presented in the figures as differing from the actual dimensions .

Fig. 1 shows a radiation source 1 producing a widening radiation beam 2, presented in the figure, for the purposes of simplicity, as having uniform in- tensity in terms of directional dependency, the beam being directed towards a distributor element 3 at an angle α of 15 degrees relative to the direction of the plane 4 of the distributor element. Between the radiation beam 2 and the distributor element 3, there is a lens 11 for collimating the radiation beam. The distributor element 3 includes a plate-like body 5 made from a transparent material with cross-sectionally triangular protrusions 6 which are elongated in a perpendicular plane relative to this cross-sectional plane arranged on the lateral surface, on the side of the radiation source, of the distributor element, in which protrusions the surfaces 7 facing the radiation source are metal-coated in order to be formed as mirror surfaces. The mirror surfaces 7 are positioned one after the another in the direction of propagation of the radiation emitted by the radiation source and side by side in the longitudinal direction of the projection of the radiation beam, imagined on the surface of the distributor element, at a distance from each other, in such manner that each of the mirror surfaces is covered by a section of the radiation beam falling onto the distributor element. Together, the mirror surfaces cover the entire cross-sectional area of the incoming radiation beam, thereby reflecting all radia- tion power of the radiation beam into the sub-beams 8 emitted by the mirror surfaces 7. The direction of the mirror surfaces 7 relative to the direction of the incoming radiation is so adjusted that the sub-beams 8 are perpendicular to the plane 4 of the distributor element. Alternatively, they could be placed in such manner that the direction of the sub-beams 8 differs slightly from the perpendicular, so that in the case where the distributor element 3 operates for example as a luminous display window the object would be illuminated from a slightly oblique direction. Each mirror surface 7 is slightly curved, so that the sub-beam 8 it reflects are formed as slightly widening. This smooths the intensity of the light falling onto the surface of the illuminated object, which may be set very close to the distributor element for example in the illumination application, which intensity might otherwise be distributed in a linear manner.

Fig. 2 shows the arrangement of Pig. 1 from the front, i.e. in a perpendicular direction relative to the plane 4 of the distributor element, and from the side of the sub-beams 8. Each of the mirror surfaces 7 is covered by a section of the radiation beam 2, originally formed as a square with rounded angles, so that the distributor element 3 practically operates as a plane radiator divided into rectangular, mutually equally bright radiating surfaces over one large surface. The cover zones of the radiation beam over the reflective surfaces 7 are indicated in the figure by diagonal lines. It is obvious to a person skilled in the art that there could also be several adjacent ra- diation sources 1, in which case the distributor element 3 and the reflective surfaces 7 placed upon it would correspondingly be wider. On the other hand, the radiation source could also be one single elongated radiation source extending in the direction of the width of the distributor element 3, such as, for example, a fluorescent lamp. In the solution of Fig. 3, the distributor element 3 is formed by two smaller plates 3a, 3b which are wedge-shaped in cross-section and connected to each other. Opposing recesses 9a, 9b have been worked or formed, during casting of the smaller plates, on those surfaces of the smaller plates which are set against each other, the recesses forming air-filled cavities 10 inside the distributor element 3 when the plates are connected to each other. The radiation beams 2a and 2b collimated by lenses 11 of the radiation sources Ia and Ib are directed so as to propagate inside the plate-like distributor element 3 in the direction of the plane of the distributor element. The longer lateral surfaces 7a, 7b of the recesses 9a, 9b are even and arranged at such angle that the radiation falling thereupon is reflected by total internal reflection into sub-beams 8a, 8b which are directed perpendicularly to and away from the plane of the distributor element. The cavities 10 required in forming the reflective surfaces 7a, 7b bring about lateral displacement in the radiation propagating through the distributor element as it passes right by the cavities, but do not exactly subdue the radiation, the lateral displacement being dependent on the refraction index of the material of the distributor element. In this manner, the reflective surfaces 7a, 7b arranged onto the distributor element 3 do practically not affect the transparency of the distributor element at all, as measured as the luminosity passing through the distributor element. The radiation sources Ia, Ib may produce radiation at mutually different wavelengths. For example, one may be a visible light lamp and the other one an infrared radiator. Such arrangement is suitable for example in the application for modifying a television signal, in which the distributor element 3 is used, on one hand, for illuminating for example a billboard and, on the other hand, for emitting in the opposite direction infrared radiation to a detector near a television camera so that the object being filmed and positioned in conjunction with the dis- tributor element would be identified in order to modify the television signal. Such television signal modification method is specifically described in more detail in the applicant's earlier patent application WO 01/58417 Al. In the arrangement of Fig. 4, the radiation beam 2 falling onto the distributor element 3 is slightly widening. This causes a drop in the intensity as the distance from the radiation source increases. Therefore, the distributor element 3 is slightly con- cave, as seen from the side of the radiation source, thereby smoothing the intensity distribution of the radiation formed by the emitted sub-beams 8. In order to ensure sufficient collimation of the sub-beams, the directions of the reflective surfaces 7 may, if re- quired, be separately adapted to correspond with those directions of the different parts of the incoming radiation beam 2 which differ from each other.

Fig. 5 shows a sequence of the distributor element 3 made from a material that is optically denser than the ambient, with projections 12 arranged on one surface thereof. The upper surface of each projection 12 is adapted to be substantially perpendicular to the direction of propagation of the incoming radiation beam 2. The lower surface of the projection 12, on the other hand, is at such angle that the radiation falling onto the projection through the upper surface is reflected by total internal reflections through the distributor element and to the other side thereof from the boundary surface between the lower surface of the projection and the ambient and in a di- rection which is substantially perpendicular to the plane of the distributor element.

The invention is not limited merely to the exemplary embodiments referred to above; instead, many variations are possible within the scope of the inventive idea defined by the claims .

Claims

1. An arrangement for distributing radiation, the arrangement comprising a radiation source (1) and a plate-like distributor element (3), positioned in the passage of a radiation beam (2) produced by the radiation source, for distributing the radiation, charac t eri z ed in that the radiation beam (2) is oriented at a slight angle to the plane (4) of the distributor element, and that the distributor element comprises a plate-like body portion (5) made from a transparent material, and reflective surfaces (7) arranged on the body portion (5) stepwise one after the other and side by side in the direction of the radiation beam (2) and at an angle to the plane (4) of the distributor element for dividing the radiation beam into sub- stantially mutually parallel sub-beams (8) in a direction which differs from the direction of the radiation beam.

2. The arrangement according to claim 1, charac t eri z ed in that the height of a reflec- tive surface (7) in the longitudinal direction of a projection of the radiation beam (2) imagined on the plane (4) of the distributor element is smaller than the height according to the typical angular resolution of the human eye .

3. The arrangement according to claim 1 or 2 , charac ter i z ed in that the reflective surface (7) is a metalized mirror surface.

4. The arrangement according to claim 1 or 2 , charac t eri z ed in that the reflective surface (7) is a total internal reflectance boundary surface between materials of higher and lower optical density.

5. The arrangement according to claim 4, charac teri z ed in that the reflective surface (7) is a boundary surface between the body portion (5) and a recess (9) formed therein and filled with mate- rial of lower optical density than the body portion for reflecting the radiation propagating in the body portion from the boundary surface by total internal reflection.

6. The arrangement according to any one of claims 1 to 5, charac t eri z ed in that the reflective surface (7) is curved to form the sub-beam as a widening sector.

7. The arrangement according to any one of claims 1 to 6, charac t eri z ed in that a colli- mating element (11) is arranged in front of the radiation source (1) for collimating the radiation beam (2) before the distributor element (3) .