JP2015114614A - Illumination device and projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to expand a region to be uniformly illuminated as much as possible.SOLUTION: An illumination device comprises: an optical element that causes incident coherent light to be diffused; a converging optical system that converges the coherent light diffused by the optical element; and a uniformizing optical system that, while causing the coherent light converged by the converging optical system to be totally reflected, emits the converged coherent light after causing the converged coherent light to propagate. An incidence surface of the uniformizing optical system is configured to be arranged at a rear side focus position of the converging optical system and an optical distance from a divergence point of the optical element to the converging optical system is configured to be longer than an optical distance from the converging optical system to the incidence surface of the uniformizing optical system.

Description

  The present invention relates to an illumination device and a projection device that can uniformly illuminate a predetermined area using coherent light.

  In an optical projection device (projector), it is important to uniformly illuminate a screen with light emitted from a light source. As a technique for realizing uniform illumination of the screen, a fly-eye lens system for liquid crystal devices, an integrator rod system for DMD (Digital Micromirror Device), and the like have been proposed.

  Conventionally, a high-intensity mercury lamp such as a high-pressure mercury lamp has been used as a light source for a projector. However, since this type of lamp has a short life, it is attracting attention to use a coherent light source such as a semiconductor laser.

  However, the coherent light emitted from the coherent light source has a problem of generating speckle. Speckle is a speckled pattern that appears when a scattering surface is irradiated with coherent light such as laser light. When speckle is generated on a screen, it is observed as speckled brightness unevenness (brightness unevenness). In addition to degradation of quality and image quality, it becomes a factor that adversely affects the observer physiologically. The reason why speckles occur when coherent light is used is that coherent light reflected by each part of a scattering reflection surface such as a screen interferes with each other because of its extremely high coherence. .

  In the past, the present inventors invented an illuminating device that scans coherent light with an optical scanning device and makes speckles in the illuminated region inconspicuous when illuminating the illuminated region with coherent light. The present inventors have invented a projection device that makes speckles generated on a screen inconspicuous when a light-modulated image is projected on the screen using this type of illumination device (see Patent Document 1).

JP 2012-58481 A

  In the illumination device for the projection device, a surface light source having a uniform illuminance distribution is required. Conventionally, an integrator rod has been used for this type of surface light source. The integrator rod is intended to cause the light incident on the incident surface to propagate while being totally reflected by the inner wall of the cylindrical member, and to emit uniform light from the entire area of the output surface. However, if the angular spread of incident light is small, the range of light diffused inside the cylindrical member becomes small, and as a result, it becomes difficult to make the light quantity uniform over the entire exit surface. In addition, from the viewpoint of reducing speckles, it is preferable that the light emitted from each point of the integrator rod exit surface has a complicated and wide angular distribution, but the size of the integrator rod entrance surface is limited. It has not been easy to efficiently enter a light beam having a sufficient angular distribution.

  The present invention has been made in order to solve the above-described problems, and its purpose is to make it possible to widen the uniformly illuminated region as much as possible and to have a sufficient angular distribution in the uniformizing optical system. It is an object of the present invention to provide an illumination device and a projection device that can efficiently enter the projector.

In order to solve the above problems, in one embodiment of the present invention, an optical element that diffuses incident coherent light; and
A condensing optical system for condensing the coherent light diffused by the optical element;
A uniformizing optical system that emits the coherent light collected by the condensing optical system after being propagated while being totally reflected, and
The entrance surface of the homogenizing optical system is disposed at the rear focal position of the condensing optical system,
An illuminating device is provided in which the optical distance from the divergence point of the optical element to the condensing optical system is longer than the optical distance from the condensing optical system to the entrance surface of the uniformizing optical system.

  The optical distance from the divergence point of the optical element to the condensing optical system may be longer than three times the optical distance from the condensing optical system to the entrance surface of the uniformizing optical system.

  When the optical element is a diffusing member having a diffusing surface, the divergence point may be the position of the diffusing surface.

  When the optical element includes a concave lens, the divergence point may be a front focal position of the concave lens.

  The optical element may be a lens array in which a plurality of concave lenses are arranged on a surface orthogonal to the optical axis of the concave lens.

  When the optical element includes a convex lens, the divergence point may be a rear focal position of the convex lens.

  The optical element may be a lens array in which a plurality of convex lenses are arranged on a surface orthogonal to the optical axis of the convex lens.

  The optical element may be a hologram recording medium on which interference fringes for reproducing an image of a reference member are recorded.

  The homogenizing optical system propagates the coherent light collected by the condensing optical system incident on the incident surface while being totally reflected by the inner wall of the cylindrical housing, so that the amount of light is uniform throughout the exit surface. It is also possible to have an integrator rod that emits coherent light.

A light source that emits coherent light;
An optical scanning device that changes a traveling direction of the coherent light emitted from the light source and scans the surface of the optical element with the coherent light.

A lighting device according to any one of claims 1 to 10,
An optical modulator that is illuminated with coherent light emitted from the homogenizing optical system to generate a modulated image;
And a projection optical system that projects the modulated image onto a predetermined projection member.

  According to the present invention, it is possible to enlarge the region to be illuminated uniformly as much as possible. Further, according to the present invention, it is possible to efficiently enter a light beam having a sufficient angular distribution into the uniformizing optical system. .

The block diagram which shows schematic structure of the projection apparatus 20 provided with the illuminating device 40 by one Embodiment of this invention. The block diagram which added the relay optical system to FIG. The figure which shows the light beam path | route until the coherent light diffused by the optical element 50 is incident on the integrator rod 76 through the condensing optical system 70. (A) is a figure which shows the light ray path by a 1st comparative example, (b) is a figure which shows the light ray path by a 2nd comparative example. The figure which shows the positional relationship of the optical element 50, the condensing optical system 70, and the integrator rod 76. FIG. (A) And (b) is a figure explaining a divergence point. The graph which shows the relationship between f '/ f and b / a. The graph which differentiated b / a once by (f '/ f). The graph which differentiated b / a twice by (f '/ f).

  Hereinafter, embodiments of the present invention will be described in detail. In the drawings attached to the present specification, for convenience of illustration and understanding, the scale, the vertical / horizontal dimensional ratio, and the like are appropriately changed or exaggerated from those of the actual ones.

  FIG. 1 is a block diagram showing a schematic configuration of a projection device 20 including an illumination device 40 according to an embodiment of the present invention. 1 includes an irradiation device 60, an optical element 50, a condensing optical system 70, a homogenizing optical system 75, a light modulator 30, and a projection optical system 80. The illumination device 40 is configured by the optical element 50 and the irradiation device 60.

  The optical element 50 has a lens array 53 including a plurality of element lenses 54. Each of the plurality of element lenses 54 is, for example, a concave lens. Alternatively, each of the plurality of element lenses 54 may be a convex lens. When the lens array 53 is configured by a plurality of concave lenses or convex lenses, these concave lenses or convex lenses may be arranged side by side on a plane orthogonal to the optical axis of each lens.

  The irradiation device 60 irradiates the lens array 53 with coherent light so that the coherent light scans the surfaces of the plurality of element lenses 54 in the lens array 53. The irradiation device 60 includes a laser light source 61 that emits coherent light, and a scanning device 65 that scans the surface of the plurality of element lenses 54 in the lens array 53 with the coherent light emitted from the laser light source 61.

  The scanning device 65 varies the reflection angle of the incident coherent light at a constant period so that the reflected coherent light scans the lens array 53.

  The condensing optical system 70 condenses the coherent light diffused by the optical element 50. The homogenizing optical system 75 propagates the coherent light collected by the condensing optical system 70 while totally reflecting it, and then emits it from the exit surface. Since the exit surface of the uniformizing optical system 75 is illuminated with a uniform amount of light, the exit surface of the uniformizing optical system 75 can be used as surface illumination light. In FIG. 1, the exit surface of the homogenizing optical system 75 is an illuminated area LZ. By providing the uniformizing optical system 75, the entire area within the illuminated area LZ is illuminated with a uniform light amount.

  The homogenizing optical system 75 can be configured using, for example, an integrator rod 76. The integrator rod 76 has a cylindrical shape, and propagates the coherent light incident on the incident surface in the direction of the exit surface while totally reflecting the light on the inner wall. As a result, coherent light having a uniform amount of light is emitted from the exit surface of the uniformizing optical system 75 throughout the exit surface. Here, the degree of homogenization varies depending on each usage pattern, but as a rough guide, the variation in the luminance distribution on the exit surface is within 10%.

  The light modulator 30 receives the illumination light of the illuminated area LZ and generates a modulated image. FIG. 1 shows an example in which the light modulator 30 is disposed so as to contact the exit surface of the integrator rod 76, but as shown in FIG. 2, a relay optical system 77 is provided behind the integrator rod 76, The optical modulator 30 may be provided further behind the relay optical system 77. In this case, the exit surface position of the integrator rod 76 and the position of the optical modulator 30 are positioned so as to have a conjugate relationship.

  As the light modulator 30, a reflection type micro display can be used. In this case, a modulated image is formed by the reflected light from the light modulator 30, the surface on which the coherent light is irradiated from the illumination device 40 to the light modulator 30, and the image light (the modulated image generated by the light modulator 30 ( The exit surface of the (reflected light) is the same surface. When using such reflected light, a MEMS (Micro Electro Mechanical Systems) element such as DMD (Digital Micromirror Device) can be used as the optical modulator 30.

  Alternatively, a transmissive liquid crystal micro display such as LCOS (Liquid Crystal on Silicon) can be used as the light modulator 30. In this case, the liquid crystal micro display illuminated in a planar shape by the illumination device 40 selects and transmits coherent light for each pixel, thereby forming a modulated image on the liquid crystal micro display. The modulated image (video light) obtained in this way is scaled as necessary by the projection optical system 80 and projected onto the diffusion screen 15. Since the speckle pattern of the modulated image projected on the diffusing screen 15 changes with time, the speckle is invisible.

  Moreover, it is preferable that the incident surface of the light modulator 30 has the same shape and size as the illuminated region LZ where the illumination device 40 emits coherent light. In this case, it is because the coherent light from the illuminating device 40 can be utilized with high utilization efficiency for displaying the image on the diffusion screen 15.

  The projection optical system 80 that projects the modulated image generated by the light modulator 30 onto the diffusing screen 15 includes, for example, a double-sided projection lens 81, and the modulated image generated by the light modulator 30 is the projection lens 81. And the modulated image 71 is projected onto the diffusion screen 15. The size of the modulated image 71 projected on the diffusion screen 15 can be adjusted by the diameter of the projection lens 81, the distance between the projection lens 81 and the light modulator 30, and the distance between the projection lens 81 and the diffusion screen 15. . The diffusing screen 15 in FIG. 1 is a transmission type, and diffuses the projected modulated image light. The diffusing screen 15 may be a reflective type.

  The light modulator 30 can generate various modulated images. The light modulator 30 generates a modulated image and illuminates it in the illuminated area LZ, thereby projecting the various modulated images on the diffusion screen. can do.

  As the laser light source 61 in the irradiation apparatus 60, for example, a plurality of laser light sources 61 that emit laser beams of different wavelength bands may be used. When a plurality of laser light sources 61 are used, the laser light from each laser light source 61 is irradiated on the scanning device 65. Thereby, the lens array 53 is illuminated with the reproduction illumination light in which the illumination colors of the laser light sources 61 are mixed.

  The laser light source 61 may be a monochromatic laser light source 61 or a plurality of laser light sources 61 having different emission colors. For example, a plurality of laser light sources 61 of red, green, and blue may be used. In the case of using a plurality of laser light sources 61, if each laser light source 61 is arranged so that the coherent light from each laser light source 61 is irradiated onto the scanning device 65, the incident angle of the coherent light from each laser light source 61 is set. The light is reflected at a corresponding reflection angle, is incident on the lens array 53, is separately collected and diverges from the lens array 53, and is superimposed on the illuminated area LZ to be a composite color. For example, when a plurality of laser light sources 61 of red, green, and blue are used, the color becomes white. Alternatively, a separate scanning device 65 may be provided for each laser light source 61.

  For example, when illuminating in white, it may be possible to reproduce a color closer to white by separately providing a laser light source 61 that emits light in a color other than red, green, and blue, for example, a laser light source 61 that emits light in yellow. . Therefore, the type of the laser light source 61 provided in the irradiation device 60 is not particularly limited.

  When forming a color modulation image, various realization methods can be considered. When the light modulator 30 is composed of LCOS or the like and has a color filter for each pixel, the modulated image generated by the light modulator 30 is colored by making the illuminated area LZ white light. can do.

  Alternatively, for example, an optical modulator 30 that generates a red modulated image, an optical modulator 30 that generates a green modulated image, and an optical modulator 30 that generates a blue modulated image are arranged close to each other. The three illuminated areas LZ that illuminate each of the light modulators 30 may be sequentially illuminated with diffused light from the lens array 53. As a result, the three color modulation images generated by the three light modulators 30 are combined to generate a color modulation image. Instead of such time-division driving, three color modulation images generated simultaneously by the three optical modulators 30 may be combined using a prism or the like to generate a color modulation image.

  The projection optical system 80 described above is provided mainly for projecting the modulated image of the light modulator 30 onto the diffusing screen 15. By providing the diffusion screen 15, speckles are overlapped and averaged, and as a result, speckles are not noticeable.

  The scanning device 65 changes the traveling direction of the coherent light with time, and directs it in various directions so that the traveling direction of the coherent light is not constant. As a result, the coherent light whose traveling direction is changed by the scanning device 65 scans the incident surface of the lens array 53 of the optical element 50.

  The coherent light emitted from the scanning device 65 is preferably parallel light. This is because in the case of parallel light, the element lens 54 in the lens array 53 can condense coherent light in the direction of the condensing optical system 70. If the coherent light emitted from the scanning device 65 is diffused light, the coherent light traveling from one element lens 54 toward the condensing optical system 70 is dispersed in various directions, and the condensing optical system. The amount of light incident on 70 is reduced. Therefore, it is desirable to provide the scanning device 65 with a collimator optical system (not shown) for making the emitted light parallel. Alternatively, another lens array may be provided between the lens array 53 and the condensing optical system 70.

  As described above, the irradiation device 60 illuminates the illuminated area LZ with coherent light. For example, when the laser light source 61 has a plurality of laser light sources 61 that emit light of different colors, the illuminated region LZ is illuminated with each color. Therefore, when these laser light sources 61 emit light at the same time, the illuminated area LZ is illuminated with white in which three colors are mixed.

  The irradiation device 60 described above irradiates the optical element 50 with coherent light so that the coherent light scans the surfaces of the plurality of element lenses 54 in the lens array 53. In addition, coherent light incident on an arbitrary position in the lens array 53 from the irradiation device 60 illuminates the entire illuminated area LZ, but the illumination directions of the coherent light that illuminate the illuminated area LZ are different from each other. Since the position on the lens array 53 where the coherent light enters changes with time, the incident direction of the coherent light to the illuminated region LZ also changes with time.

  As described above, in this embodiment, coherent light continuously scans on the lens array 53. Along with this, the incident direction of coherent light incident on the illuminated area LZ from the irradiation device 60 via the optical element 50 also changes continuously. Here, if the incident direction of the coherent light from the optical element 50 to the illuminated area LZ changes only slightly (for example, several degrees), the pattern of speckles generated on the illuminated area LZ also changes greatly, and is uncorrelated. A speckle pattern is superimposed.

  In the present embodiment, the incident direction of coherent light changes temporally at each position of the illuminated region LZ, and this change is at a speed that cannot be resolved by human eyes. Accordingly, if a screen is arranged in the illuminated area LZ, speckles generated corresponding to each incident angle are overlapped and averaged and observed by the observer, so that the image displayed on the screen Speckle can be made very inconspicuous for an observer who observes the above. In the case of the present embodiment, the light modulator 30 is arranged so as to overlap the position of the illuminated region LZ, and the light modulator 30 projects onto the diffusion screen 15 via the projection optical system 80. Similarly, since speckles generated on the diffusion screen 15 are overlapped and averaged, the speckles generated on the diffusion screen 15 become inconspicuous.

  In the present embodiment, the incident surface of the integrator rod 76 is disposed at the rear focal position of the condensing optical system 70, and the optical distance from the divergence point of the optical element 50 to the condensing optical system 70 is set as the condensing optical system 70. It is longer than the focal length.

  FIG. 3 is a diagram showing a light beam path until the coherent light diffused by the optical element 50 enters the integrator rod 76 through the condensing optical system 70. As shown in the figure, the coherent light from the optical element 50 is incident on the condensing optical system 70 with a spread, but the condensing optical system 70 narrows the coherent light and makes it incident on the integrator rod 76. As a result, the coherent light incident on the integrator rod 76 is incident at a large angle with respect to the normal direction of the incident surface of the integrator rod 76, and is easily totally reflected by the inner wall of the integrator rod 76. A uniform amount of light can be obtained over the entire exit surface of the rod 76.

  FIG. 4A is a diagram illustrating a light beam path according to the first comparative example, and FIG. 4B is a diagram illustrating a light beam path according to the second comparative example. In the case of FIG. 4A, the optical element 50 is disposed close to the condensing optical system 70. Accordingly, the coherent light exiting the optical element 50 is incident on the condensing optical system 70 without spreading so much, and the coherent light exiting the condensing optical system 70 is incident on the integrator rod 76 while being diverged. That is, as shown in FIG. 4A, when the optical element 50 is disposed in the vicinity of the condensing optical system 70, the condensing optical system 70 cannot condense incident coherent light. Therefore, in order to increase the light incident efficiency to the integrator rod 76, the coherent light emitted from the condensing optical system 70 is incident on the integrator rod 76 with a small diffusion angle on the incident surface of the integrator rod 76. . In this case, the angular spread of the light totally reflected by the inner wall of the integrator rod 76 is reduced, and the illuminance distribution on the exit surface tends to be uneven. In addition, the ratio at which the diffused light from each point of the optical element 50 is superimposed on the exit surface of the integrator rod 76 becomes small, and the speckle reduction effect by angle multiplexing becomes insufficient.

  In the case of FIG. 4B, the optical element 50 is provided in front of the front focal position of the condensing optical system 70. Accordingly, the coherent light diffused by the optical element 50 and incident on the condensing optical system 70 converges on the incident surface side of the integrator rod 76 with respect to the exit surface of the condensing optical system 70. In this case, the light incident efficiency to the integrator rod 76 is increased, that is, the angular spread of the light totally reflected by the inner wall of the integrator rod 76 is increased while the light beam area on the incident surface of the integrator rod 76 is kept small. Thus, the illuminance distribution in the exit surface can be made closer to uniform.

  As can be seen from FIGS. 3 and 4, most of the coherent light emitted from the condensing optical system 70 is totally reflected by the inner wall of the integrator rod 76 while keeping the light beam area at the entrance surface of the integrator rod 76 small. In order to increase the angular spread of the light, the coherent light diffused by the optical element 50 is incident on the condensing optical system 70 with a beam diameter as large as possible, and is incident on the incident surface of the integrator rod 76 with a beam diameter as small as possible. Need to be done.

  FIG. 5 is a diagram showing the positional relationship among the optical element 50, the condensing optical system 70, and the integrator rod 76. In FIG. 5, the optical distance from the divergence point of the optical element 50 to the condensing optical system 70 is f ′, and the optical distance from the condensing optical system 70 to the entrance surface of the integrator rod 76 is f. Since the integrator rod 76 is disposed at the rear focal position of the condensing optical system 70, the optical distance f from the condensing optical system 70 to the entrance surface of the integrator rod 76 is the focal length of the condensing optical system 70. equal to f.

  The divergence point of the optical element 50 is the position of the diffusion surface when the optical element 50 is a diffusion member having a diffusion surface. When the optical element 50 is a lens array 53 composed of a plurality of concave lenses 54, the front focal position of the concave lens 54 is a divergence point as shown in FIG. When the optical element 50 is a lens array 53 including a plurality of convex lenses 54, the rear focal position of the convex lens 54 is a divergence point as shown in FIG. 6B.

  As can be seen from FIGS. 6A and 6B, when the convex lens 54 is used as the lens array 53, light rays intersect between the convex lens 54 and the condensing optical system 70. And the condensing optical system 70 are longer than the optical distance between the convex lens 54 and the condensing optical system 70. Therefore, it is desirable to use the concave lens 54 for the lens array 53 from the viewpoint of miniaturization of the apparatus.

  In FIG. 5, the beam diameter indicating the range in which the light diffused from the optical element 50 is incident on the condensing optical system 70 is a, and the light emitted from the condensing optical system 70 is incident on the incident surface of the integrator rod 76. The beam diameter indicating the range is b.

  As described above, in order to make the illuminance distribution uniform throughout the exit surface of the integrator rod 76, it is desirable that b / a be as small as possible. The fact that b / a is small indicates that the convergence angle with respect to the incident surface of the integrator rod 76 is large. In this case, the angular spread of the coherent light is increased inside the integrator rod 76. Therefore, the present inventor sets the optimum condition of the optical distance f ′ from the divergence point of the optical element 50 to the condensing optical system 70 and the optical distance f from the condensing optical system 70 to the entrance surface of the integrator rod 76. Verified.

  FIG. 7 is a graph showing the relationship between f '/ f and b / a, where the horizontal axis is f' / f and the vertical axis is b / a. The graph of FIG. 7 shows an inversely proportional relationship in which b / a decreases as f ′ / f increases. B / a changes abruptly with a region r1 surrounded by a circle in FIG. 7 as a boundary.

  FIG. 8 is a graph obtained by differentiating b / a once by (f ′ / f), and FIG. 9 is a graph obtained by differentiating b / a twice by (f ′ / f). FIG. 8 shows the degree of change of the graph of FIG. 7, and FIG. 9 shows the degree of change of the graph of FIG.

  In the graph of FIG. 8, when f ′ / f = 3 is exceeded, the inclination is drastically reduced. In the graph of FIG. 9, when f ′ / f = 3 is exceeded, the slope converges to almost zero.

  From these results, it can be seen that if f ′ / f> 3, b / a can be set large enough to be practically sufficient. Even if f ′ / f ≦ 3, if f ′ / f> 1, the light flux area on the incident surface of the integrator rod 76 may be slightly increased, but the illumination device 40 and the projection device 20 are used. Can be used practically without problems.

  Usually, when designing an optical system, in order to reduce the size of the apparatus, the distance f ′ between the optical element 50 and the condensing optical system 70 and the distance f between the condensing optical system 70 and the entrance surface of the integrator rod 76 are used. Never make it bigger. That is, a person skilled in the art should be able to assume that f ′ ≦ f, but it cannot be assumed that f ′> f.

  On the other hand, the present inventor can expand the uniform range on the exit surface while maintaining the incident light beam area to the integrator rod 76 small by setting f ′> f by the verification of FIGS. 7 to 9. This knowledge has never been conceived by knowledge normally used by those skilled in the art.

  By setting f ′> f, the optical distance of the entire apparatus becomes long, which can hinder downsizing of the apparatus, but the uniformizing region of the light amount on the exit surface of the integrator rod 76 becomes wide. Forty, the performance is improved.

  For example, the scanning device 65 of the present embodiment changes the reflection angle of coherent light from the laser light source 61 with time. Thereby, the coherent light from the scanning device 65 scans on the optical element 50. More specifically, the coherent light from the scanning device 65 is diffused according to the light diffusion characteristics of the optical element 50 while temporally changing the incident position on the optical element 50. Accordingly, coherent light whose incident angle changes with time is incident on the uniformizing optical system 75, and these coherent light propagates in the direction of the exit surface while being totally reflected in the uniformizing optical system 75. The exit surface of the system 75 will be illuminated at different angles in time and with uniform illuminance.

  In some wavelength regions, for example, blue component coherent light, speckles may hardly be noticed because the visibility of human eyes is low. Therefore, it is not always essential to provide the scanning device 65 in the irradiation apparatus 60 and scan the coherent light on the optical element 50.

  Further, FIG. 1 shows an example in which the scanning device 65 is provided in the irradiation device 60 and the coherent light is scanned on the optical element 50. Instead of providing the scanning device 65, the optical element 50 may be vibrated. Good. Thereby, even if the irradiation position of the coherent light from the irradiation device 60 is fixed, as a result, the coherent light can be scanned on the optical element 50, and the speckle reduction is the same as when the scanning device 65 is provided. An effect is obtained. In order to vibrate the optical element 50, for example, a vibration mechanism such as a vibration motor or a voice coil may be provided.

  In FIG. 1, the example in which the lens array 53 is used as the optical element 50 has been described. However, as a specific example of the lens array 53, a total reflection type or refractive type Fresnel lens having a diffusion function, a fly-eye lens, or the like can be applied. It is.

  Further, the optical element 50 is not necessarily limited to the lens array 53, and for example, a hologram recording medium may be used. In the hologram recording medium in this case, interference fringes that can reproduce the image of the scattering plate are formed in the illuminated area LZ. When the hologram recording medium is irradiated with coherent light from the irradiation device 60, the coherent light diffracted by the interference fringes is emitted as divergent light (diffused light). More specifically, the coherent light incident on each position of the hologram recording medium from the irradiation device 60 is diffracted by the hologram recording medium, passes through the condensing optical system 70, and then enters the integrator rod 76.

  The hologram recording medium may be a reflection type volume hologram using a photopolymer, or may include a type of volume hologram which is recorded using a photosensitive medium containing a silver salt material. The optical element 50 may include a transmission type volume hologram recording medium, or may include a relief type (emboss type) hologram recording medium.

  Alternatively, the optical element 50 can be configured by a diffusion plate. As the diffusion plate, a glass member such as an opal glass file or a resin diffusion plate can be considered. Since the diffusion plate diffuses the coherent light reflected by the scanning device 65, it is possible to illuminate the illuminated region LZ from various directions as in the case of using the hologram recording medium or the lens array 53. Note that “diffusion” in the optical element 50 in the present embodiment means that incident light is angularly expanded in a predetermined direction and emitted, and the diffusion angle by the diffractive optical element 50, the lens array 53, and the like is sufficiently controlled. This includes not only the case where the emission angle is increased, but also the case where the emission angle is expanded by scattering particles such as opal glass.

  As described above, in this embodiment, the incident surface of the uniformizing optical system 75 is disposed at the rear focal position of the condensing optical system 70, and the optical distance from the divergence point of the optical element 50 to the condensing optical system 70 is collected. Since the optical distance from the optical optical system 70 to the uniform optical system is also increased, the coherent light incident on the uniform optical system 75 can be propagated and emitted while being efficiently totally reflected by the inner wall of the uniform optical system 75, The amount of light emitted from the entire exit surface of the uniformizing optical system 75 can be made uniform. Therefore, the illuminating device 40 which can illuminate the illuminated area LZ having a large size and a high degree of uniformity in the amount of light can be realized.

  In addition, by causing the scanning device 65 to scan the coherent light on the optical element 50, the emission angle of the coherent light on the emission surface of the homogenizing optical system 75 changes with time. Therefore, by guiding the coherent light on the exit surface of the homogenizing optical system 75 to the projection optical system 80, the speckle pattern projected on the diffusion screen 15 or generated on the diffusion screen 15 is temporally changed. And the observed speckle is made invisible.

  The aspect of the present invention is not limited to the individual embodiments described above, and includes various modifications that can be conceived by those skilled in the art, and the effects of the present invention are not limited to the contents described above. That is, various additions, modifications, and partial deletions can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

  15 Diffusion screen, 20 Projection device, 30 Light modulator, 40 Illumination device, 50 Optical element, 53 Lens array, 54 Element lens, 60 Irradiation device, 61 Lens light source, 65 Scanning device, 70 Condensing optical system, 75 Uniformization Optical system, 76 integrator rod, 77 relay optical system, 80 projection optical system, 81 projection lens,

Claims (11)

An optical element for diffusing incident coherent light;
A condensing optical system for condensing the coherent light diffused by the optical element;
A uniformizing optical system that emits the coherent light collected by the condensing optical system after being propagated while being totally reflected, and
The entrance surface of the homogenizing optical system is disposed at the rear focal position of the condensing optical system,
The illuminating device, wherein an optical distance from the divergence point of the optical element to the condensing optical system is longer than an optical distance from the condensing optical system to an incident surface of the uniformizing optical system.   2. The illumination device according to claim 1, wherein an optical distance from a divergence point of the optical element to the condensing optical system is longer than three times an optical distance from the condensing optical system to an incident surface of the uniformizing optical system.   The illumination device according to claim 1, wherein when the optical element is a diffusing member having a diffusing surface, the divergence point is a position of the diffusing surface.   The illumination device according to claim 1, wherein when the optical element includes a concave lens, the divergence point is a front focal position of the concave lens.   The illumination device according to claim 4, wherein the optical element is a lens array in which a plurality of concave lenses are arranged on a surface orthogonal to the optical axis of the concave lenses.   3. The illumination device according to claim 1, wherein when the optical element includes a convex lens, the divergence point is a rear focal position of the convex lens.   The illumination device according to claim 6, wherein the optical element is a lens array in which a plurality of convex lenses are arranged on a surface orthogonal to the optical axis of the convex lens.   The illumination device according to claim 1, wherein the optical element is a hologram recording medium on which interference fringes for reproducing an image of a reference member are recorded.   The homogenizing optical system propagates the coherent light collected by the condensing optical system incident on the incident surface while being totally reflected by the inner wall of the cylindrical housing, so that the amount of light is uniform throughout the exit surface. The illuminating device according to claim 1, further comprising an integrator rod that emits coherent light. A light source that emits coherent light;
An illumination apparatus according to claim 1, further comprising: an optical scanning device that changes a traveling direction of the coherent light emitted from the light source and scans the surface of the optical element with the coherent light. . A lighting device according to any one of claims 1 to 10,
An optical modulator that is illuminated with coherent light emitted from the homogenizing optical system to generate a modulated image;
A projection optical system that projects the modulated image onto a predetermined projection member.