JP2012230360A - Illumination device, projection device and projection type image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device capable of reducing visibility of speckle.SOLUTION: An illumination device 40 includes: an optical element 50 that can diffuse coherent light; and a plurality of coherent light sources 61a, 61b, 61c emitting coherent beams at the same wavelength. The optical element includes a plurality of incident regions 55a, 55b, 55c. The coherent beam from each coherent light source is incident to the corresponding incident region of the optical element. The coherent beams incident to the respective incident regions of the optical element and then diffused illuminate regions that at least partially overlapping each other.

Description

  The present invention relates to an illumination device that illuminates an illuminated area with coherent light, a projection device that projects coherent light, and a projection-type image display device that displays an image using coherent light, and in particular, generation of speckle is inconspicuous. The present invention relates to a lighting device, a projection device, and a projection-type image display device that can be made to operate.

  Projection-type image display devices having a screen and a projection device that projects image light on the screen are widely used. In a typical projection-type image display device, an original two-dimensional image is generated by using a spatial light modulator such as a liquid crystal micro display or a DMD (Digital Micromirror Device), and the two-dimensional image is projected into an optical system. An image is displayed on the screen by enlarging and projecting on the screen using the system.

  Various types of projectors have been proposed, including commercially available products called “optical projectors”. In general optical projectors, a spatial light modulator such as a liquid crystal display is illuminated using a lighting device consisting of a white light source such as a high-pressure mercury lamp, and the resulting modulated image is projected onto a screen using a lens. Adopted. For example, in Patent Document 1 below, white light generated by an ultra-high pressure mercury lamp is divided into three primary color components of R, G, and B by a dichroic mirror, and these lights are guided to a spatial light modulator for each primary color. A technique is disclosed in which a generated modulated image for each primary color is synthesized by a cross dichroic prism and projected onto a screen.

  However, high-intensity discharge lamps such as high-pressure mercury lamps have a relatively short life, and when used in optical projectors or the like, it is necessary to frequently replace the lamps. Furthermore, it is not preferable to use a high-pressure mercury lamp that uses mercury from the viewpoint of environmental impact. Further, since it is necessary to use a relatively large optical system such as a dichroic mirror in order to extract the light of each primary color component, there is a problem that the entire apparatus becomes large.

  In order to cope with such a problem, a method using a coherent light source such as a laser has been proposed. For example, a semiconductor laser widely used in the industry has a very long life compared to a high-intensity discharge lamp such as a high-pressure mercury lamp. In addition, since the light source can generate light having a single wavelength, a spectroscopic device such as a dichroic mirror is not necessary, and the entire device can be reduced in size.

  On the other hand, a method using a coherent light source such as a laser beam has a new problem such as generation of speckle. A speckle is a speckled pattern that appears when a scattering surface is irradiated with laser light or other coherent light. When it appears on a screen, it is observed as speckled brightness irregularities (brightness irregularities). It becomes a factor having a physiological adverse effect on the person. 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. . For example, in the following Non-Patent Document 1, detailed theoretical considerations regarding the generation of speckle are made.

  As described above, in the system using the coherent light source, a problem inherent to the generation of speckles occurs, and thus a technique for suppressing the generation of speckles has been proposed. For example, in Patent Document 2 below, the speckle is reduced by irradiating a scattering plate with laser light, guiding the scattered light obtained therefrom to a spatial light modulator, and rotating the scattering plate by a motor. Technology is disclosed.

JP 2004-264512 A Japanese Patent Laid-Open No. 6-208089

Speckle Phenomena in Optics, Joseph W. Goodman, Roberts & Co., 2006

  As described above, technologies for reducing speckles have been proposed in projection devices and projection-type video display devices using a coherent light source. However, the methods proposed so far effectively and sufficiently suppress speckles. I can't do it. For example, in the method disclosed in the above-mentioned Patent Document 2, laser light is irradiated on the scattering plate and scattered, and therefore, part of the laser light is wasted without contributing to video display at all. Moreover, although it is necessary to rotate a scattering plate for speckle reduction, such a mechanical rotation mechanism becomes a comparatively large apparatus, and also power consumption becomes large. Furthermore, even if the scattering plate is rotated, the position of the optical axis of the illumination light does not change, so that speckles generated due to diffusion on the screen cannot be sufficiently suppressed.

  Speckle is not a problem specific to a projection device or a projection type image display device, but is a problem in various devices in which an illumination device that illuminates coherent light in an illuminated area. For example, a scanner that reads image information incorporates an illumination device that illuminates an object to be read. When speckle is generated by the light that illuminates the object to be read, the image information cannot be read accurately. In order to avoid such an inconvenience, a scanner using coherent light needs to perform special processing such as image correction.

  The inventors of the present invention have made extensive studies based on the above points, and as a result, invented an illuminating device that illuminates an illuminated area with coherent light, which can make speckle inconspicuous. I went to. That is, an object of the present invention is to provide an illuminating device capable of making speckles inconspicuous, a projection device including the illuminating device, and a projection-type image display device.

The lighting device according to the present invention comprises:
An optical element capable of diffusing coherent light;
A plurality of coherent light sources that emit coherent light of the same wavelength, and
The optical element has a plurality of incident areas;
The coherent light from each coherent light source is incident on a corresponding incident region of the optical element;
The coherent light that has entered and diffused into each incident region of the optical element illuminates regions that overlap each other at least in part.

In the lighting device according to the present invention,
An incident-side optical system that guides the coherent light to each incident region of the optical element may be provided between the plurality of coherent light sources and the optical element.

In the lighting device according to the present invention,
The incident side optical system may include an imaging optical system that forms an image of each of the coherent light sources on a corresponding incident region of the optical element.

In the lighting device according to the present invention,
The incident side optical system may be a lens, a diffractive optical element, or a prism.

In the lighting device according to the present invention,
An optical fiber that guides the coherent light to the corresponding incident region of the optical element may be provided between each coherent light source and the corresponding incident region of the optical element.

In the lighting device according to the present invention,
The optical element may be a hologram recording medium.

In the lighting device according to the present invention,
The optical element may be a lens array that changes a traveling direction of incident light.

In the lighting device according to the present invention,
The optical element may be a diffusion plate that changes a traveling direction of incident light.

In the lighting device according to the present invention,
The diffusion plate may be opal glass, frosted glass, or a resin diffusion plate.

In the lighting device according to the present invention,
The plurality of coherent light sources may be built in a laser array.

In the lighting device according to the present invention,
The plurality of coherent light sources may be a plurality of independent laser light sources.

The projection apparatus according to the present invention
A lighting device according to the invention as described above;
A spatial light modulator disposed at a position illuminated by coherent light from the illumination device.

In the projection apparatus according to the present invention,
You may further provide the projection optical system which projects the modulation image obtained on the said spatial light modulator on a screen.

A first projection display apparatus according to the present invention is:
A projection device according to the invention as described above;
And a screen on which a modulated image obtained on the spatial light modulator is projected.

A second projection type video display device according to the present invention is:
A lighting device according to the invention as described above;
And a screen disposed at a position illuminated by coherent light from the illumination device.

  ADVANTAGE OF THE INVENTION According to this invention, the speckle on the to-be-illuminated area | region or the surface which projects an image | video can be made effectively inconspicuous.

FIG. 1 is a diagram for explaining a basic form of an embodiment according to the present invention, and shows a schematic configuration of a lighting device, a projection apparatus, and a projection type video display apparatus as one specific example of the basic form. FIG. FIG. 2 is a diagram illustrating the illumination device illustrated in FIG. 1. FIG. 3 is a diagram for explaining an exposure method for producing a hologram recording medium that forms an optical element of the illumination device of FIG. FIG. 4 is a diagram for explaining the operation of the hologram recording medium manufactured through the exposure method of FIG. FIG. 5 is a perspective view of the lighting device shown in FIG. FIG. 6 is a view showing a modification of the irradiation apparatus. FIG. 7 is a diagram showing another modification of the irradiation apparatus. FIG. 8 is a diagram for explaining a modification of the optical element, and is a plan view showing the optical element together with a corresponding illuminated region. FIG. 9 is a diagram for explaining another modified example of the optical element, and is a plan view showing the optical element together with a corresponding illuminated region. FIG. 10 is a view corresponding to FIG. 5, and is a perspective view for explaining another modification of the irradiation apparatus and its operation. FIG. 11 is a diagram for explaining a modification of the incident-side optical system, and is a diagram illustrating a schematic configuration of the illumination device, the projection device, and the projection-type image display device. FIG. 12 is a diagram for explaining another modified example of the incident side optical system, and is a diagram illustrating a schematic configuration of the illumination device, the projection device, and the projection type video display device.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to the present specification, for the sake of illustration and ease of understanding, the scale, the vertical / horizontal dimension ratio, and the like are appropriately changed and exaggerated from those of the actual product.

  The illumination device, the projection device, and the projection-type image display device according to an embodiment of the present invention have a configuration that can effectively prevent speckle as a basic configuration.

  FIGS. 1-12 is a figure for demonstrating the illuminating device which concerns on one embodiment of this invention, a projection apparatus, a projection type video display apparatus, and its modification. Among these, with reference to FIGS. 1-5, the illuminating device which concerns on the basic form of one Embodiment, a projection apparatus, and a projection type video display apparatus are demonstrated. Then, an example of the modification with respect to the illuminating device which concerns on a basic form, a projection apparatus, and a projection type video display apparatus is demonstrated.

<Basic form>
[Configuration of basic form]
First, the configuration of a projection-type image display device that includes an illumination device that projects coherent light and a projection device and can make speckles inconspicuous will be described mainly with reference to FIGS.

  A projection video display device 10 shown in FIG. 1 includes a screen 15 and a projection device 20 that projects video light including coherent light. The projection device 20 includes an illuminating device 40 that illuminates the illuminated region LZ located on the virtual plane with coherent light, and a spatial light modulator that is disposed at a position overlapping the illuminated region LZ and that is illuminated with the coherent light by the illuminating device 40. 30 and a projection optical system 25 that projects the coherent light from the spatial light modulator 30 onto the screen 15.

  As the spatial light modulator 30, for example, a transmissive liquid crystal microdisplay can be used. In this case, the spatial light modulator 30 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 screen of the display that forms the spatial light modulator 30. Will come to be. The modulated image (video light) thus obtained is projected onto the screen 15 at the same magnification or scaled by the projection optical system 25. As a result, the modulated image is displayed on the screen 15 at the same magnification or at a variable magnification, usually enlarged, and the observer can observe the image.

  As the spatial light modulator 30, a reflective micro display can be used. In this case, a modulated image is formed by the reflected light from the spatial light modulator 30, the surface on which the spatial light modulator 30 is irradiated with coherent light from the illumination device 40, and the image light that forms the modulated image from the spatial light modulator 30. The surface where the lead is the same surface. When such reflected light is used, a MEMS element such as a DMD (Digital Micromirror Device) can be used as the spatial light modulator 30. In the apparatus disclosed in Patent Document 2 described above, DMD is used as a spatial light modulator.

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

  The screen 15 may be configured as a transmissive screen or may be configured as a reflective screen. In the case where the screen 15 is configured as a reflective screen, the observer observes an image displayed by coherent light reflected by the screen 15 from the same side as the projection device 20 with respect to the screen 15. On the other hand, when the screen 15 is configured as a transmissive screen, the observer observes an image displayed by coherent light transmitted through the screen 15 from the side opposite to the projection device 20 with respect to the screen 15. .

  By the way, the coherent light projected on the screen 15 is diffused and recognized as an image by the observer. At this time, the coherent light projected on the screen interferes by diffusion and causes speckle. However, in the projection-type image display device 10 described here, the illumination device 40 described below includes a plurality of coherent lights having different incident angles and not coherent with each other, and the spatial light modulator 30 is overlaid. The illuminated area LZ is illuminated at the same time. More specifically, the illuminating device 40 described below illuminates the illuminated region LZ simultaneously with a plurality of diffused light composed of coherent light, but the incident angles of these diffused light are different from each other. As a result, the coherent lights projected on the screen 15 also have different incident angles, so that speckle patterns are generated on the screen 15 by the number of coherent lights, and these speckle patterns do not interfere with each other and are spatially generated. Is superimposed on. Therefore, speckles generated by the diffusion of coherent light are superimposed and become inconspicuous. Hereinafter, such an illuminating device 40 will be described in more detail.

  1 and 2 includes an optical element 50 that diffuses coherent light and directs the traveling direction of the coherent light toward the illuminated region LZ, and an irradiation apparatus 60 that irradiates the optical element 50 with the coherent light. ,have. The optical element 50 is capable of diffusing coherent light with respect to at least the entire illuminated area LZ at each point. The optical element 50 includes a hologram recording medium 55 that can reproduce the image 5 of the scattering plate 6. In the illustrated example, the optical element 50 is formed from a hologram recording medium 55.

  The hologram recording medium 55 constituting the optical element 50 in the illustrated example can receive the coherent light emitted from the irradiation device 60 as the reproduction illumination light La, and can diffract the coherent light with high efficiency. In particular, the hologram recording medium 55 can reproduce the image 5 of the scattering plate 6 by diffracting coherent light incident on each position, in other words, each minute region that should be called each point. ing. As shown in FIG. 1, the hologram recording medium 55 has three incident areas 55a, 55b, and 55c. However, each of the incident areas 55a, 55b, and 55c represents an area where the corresponding coherent light can enter, and the hologram recording medium 55 may not be actually partitioned.

  On the other hand, the irradiation device 60 has the same wavelength with no coherence to the optical element 50 so that each coherent light is incident only on the corresponding incident areas 55a, 55b, 55c on the hologram recording medium 55 of the optical element 50. A plurality of coherent lights, here, three coherent lights are irradiated. The region on the hologram recording medium 55 irradiated with certain coherent light by the irradiation device 60 is a part of the surface of the hologram recording medium 55, and in particular, in the example shown in the drawing, is a minute region to be called a point. When two or more coherent lights having no interference with each other are irradiated to the same point on the surface of the hologram recording medium 55, speckles are caused.

  Then, each coherent light irradiated from the irradiation device 60 onto the hologram recording medium 55 is placed at a corresponding position (corresponding point or corresponding region (hereinafter the same)) on the hologram recording medium 55. Are incident at the same angle so as to satisfy the diffraction conditions. The coherent light that is diffused by being incident on the incident areas 55a, 55b, and 55c of the hologram recording medium 55 from the irradiation device 60 is diffracted by the hologram recording medium 55 and illuminates areas that overlap each other at least partially. In particular, in the embodiment described here, the coherent light incident on the incident areas 55a, 55b, and 55c of the hologram recording medium 55 from the irradiation device 60 is diffracted by the hologram recording medium 55 to illuminate the same illuminated area LZ. It is supposed to be. More specifically, as shown in FIG. 2, the coherent light that has entered the three incident areas 55a, 55b, and 55c of the hologram recording medium 55 from the irradiation device 60 is superimposed on the illuminated area LZ, and the scattering plate 6 The image 5 is reproduced. That is, the coherent light that has entered the three positions of the hologram recording medium 55 from the irradiation device 60 is diffused by the optical element 50 and simultaneously enters the illuminated area LZ. That is, when considered on a virtual surface located closer to the hologram recording medium 55 than the illuminated region LZ, the coherent light incident and diffracted on each of the incident regions 55a, 55b, and 55c of the hologram recording medium 55 is on this virtual surface. The corresponding regions in are at least partially illuminated so as to overlap each other.

  In the illustrated example, a transmission type volume hologram using a photopolymer is used as the hologram recording medium 55 that enables the diffraction action of such coherent light. As shown in FIG. 3, the hologram recording medium 55 is manufactured by using the scattered light from the actual scattering plate 6 as the object light Lo. FIG. 3 shows a state in which the hologram photosensitive material 58 having photosensitivity that forms the hologram recording medium 55 is exposed to the reference light Lr and the object light Lo, which are coherent light beams having coherence with each other. ,It is shown.

  As the reference light Lr, for example, laser light from a laser light source that oscillates laser light in a specific wavelength region is used, and passes through the condensing element 7 formed of a lens and enters the hologram photosensitive material 58. In the example shown in FIG. 3, the laser light that forms the reference light Lr is incident on the condensing element 7 as a parallel light beam parallel to the optical axis of the condensing element 7. The reference light Lr passes through the condensing element 7, so that it is shaped (converted) into a convergent light beam from the parallel light beam so far, and is incident on the hologram photosensitive material 58. At this time, the focal position FP of the convergent light beam Lr is at a position beyond the hologram photosensitive material 58. In other words, the hologram photosensitive material 58 is disposed between the condensing element 7 and the focal position FP of the convergent light beam Lr collected by the condensing element 7.

  Next, the object light Lo is incident on the hologram photosensitive material 58 as scattered light from a scattering plate 6 made of, for example, opal glass. Here, since the hologram recording medium 55 to be manufactured is a transmission type, the object light Lo is incident on the hologram photosensitive material 58 from the same plane as the reference light Lr. The object light Lo needs to have coherency with the reference light Lr. Therefore, for example, laser light oscillated from the same laser light source can be divided, and one of the divided lights can be used as the reference light Lr and the other can be used as the object light Lo.

  In the example shown in FIG. 3, a parallel light beam parallel to the normal direction to the plate surface of the scattering plate 6 is incident on and scattered by the scattering plate 6, and the scattered light transmitted through the scattering plate 6 is the object light Lo. The light enters the hologram photosensitive material 58. According to this method, when an isotropic scattering plate that is usually available at a low cost is used as the scattering plate 6, the object light Lo from the scattering plate 6 is incident on the hologram photosensitive material 58 with a substantially uniform light amount distribution. Is possible. Further, according to this method, although depending on the degree of scattering by the scattering plate 6, the object light Lo is incident on each position of the hologram photosensitive material 58 with a substantially uniform light amount from the entire area of the exit surface 6 a of the scattering plate 6. It becomes easy. In such a case, the light incident on each position of the obtained hologram recording medium 55 reproduces the image 5 of the scattering plate 6 with the same brightness, and the reproduced scattering plate 6 It can be realized that the image 5 is observed with substantially uniform brightness.

  As described above, when the hologram recording material 58 is exposed to the reference light Lr and the object light Lo, an interference fringe formed by the interference of the reference light Lr and the object light Lo is generated. In the case of a pattern, that is, a volume hologram, for example, it is recorded on the hologram recording material 58 as a refractive index modulation pattern. Thereafter, appropriate post-processing corresponding to the type of the hologram recording material 58 is performed, and the hologram recording material 55 is obtained.

  FIG. 4 shows the diffraction action (reproduction action) of the hologram recording medium 55 obtained through the exposure process of FIG. As shown in FIG. 4, the hologram recording medium 55 formed from the hologram photosensitive material 58 of FIG. 3 is light having the same wavelength as the laser beam used in the exposure process, and the optical path of the reference light Lr in the exposure process. The light traveling in the opposite direction satisfies the diffraction condition. That is, as shown in FIG. 4, the reference point SP positioned with respect to the hologram recording medium 55 in the same positional relationship as the relative position of the focal point FP (see FIG. 3) with respect to the hologram photosensitive material 58 during the exposure process. The divergent light beam that diverges from the light and has the same wavelength as the reference light Lr during the exposure process is diffracted as the reproduction illumination light La to the hologram recording medium 55, and the relative position of the scattering plate 6 relative to the hologram photosensitive material 58 during the exposure process A reproduced image 5 of the scattering plate 6 is generated at a specific position with respect to the hologram recording medium 50 that has the same positional relationship as (see FIG. 3).

  At this time, the reproduction light Lb for generating the reproduction image 5 of the scattering plate 6, that is, the light formed by diffracting the reproduction illumination light La by the hologram recording medium 55 travels from the scattering plate 6 toward the hologram photosensitive material 58 during the exposure process. Each point of the image 5 of the scattering plate 6 is reproduced as light traveling in the opposite direction along the optical path of the object light Lo that has been emitted. As described above and as shown in FIG. 3, the scattered light Lo emitted from each position on the exit surface 6 a of the scattering plate 6 in the exposure process is incident on almost the entire region of the hologram photosensitive material 58. Has spread. That is, the object light Lo from the entire area of the exit surface 6 a of the scattering plate 6 is incident on each position on the hologram photosensitive material 58, and as a result, information on the entire exit surface 6 a is placed on each position of the hologram recording medium 55. Each is recorded. For this reason, each light which forms the divergent light beam from the reference point SP functioning as the reproduction illumination light La shown in FIG. 4 is incident on each position of the hologram recording medium 55 independently and has the same contour. The image 5 of the scattering plate 6 can be reproduced at the same position (illuminated area LZ).

  On the other hand, the irradiation device 60 that irradiates the optical element 50 composed of the hologram recording medium 55 with the coherent light can be configured as follows. In the example shown in FIGS. 1 and 2, the irradiation device 60 includes a laser array 62 and a concave lens 71 as the incident side optical system 70.

  The laser array 62 includes three laser light sources (coherent light sources) 61a, 61b, and 61c each generating coherent light having the same wavelength in one chip. The coherent lights from the different solid laser light sources 61a, 61b, 61c are not coherent with each other. In this basic mode, an example including three laser light sources 61a, 61b, and 61c will be described in order to clarify the explanation, but it is preferable that the number of laser light sources is large. This is because, as will be described later, speckles can be made inconspicuous as the number of laser light sources increases.

  The concave lens 71 is disposed between the laser light sources 61a, 61b, 61c and the optical element 50. Laser light sources 61a, 61b, and 61c in the laser array 62 emit coherent light in parallel directions. The concave lens 71 guides each coherent light to the corresponding incident areas 55a, 55b, and 55c of the hologram recording medium 55 so that these parallel coherent lights spread. Thereby, the coherent light from each laser light source 61a, 61b, 61c is incident only on the corresponding incident area of the hologram recording medium 55. The coherent light from the concave lens 71 is coherent light that can form one light beam from the reference point SP in FIG. The incident side optical system 70 may be a diffractive optical element or a prism.

  Only the coherent light from the laser light source 61a is incident on a predetermined position of the incident area 55a, whereby the image 5 of the scattering plate 6 is reproduced over the entire illuminated area LZ. The positions of the laser light source 61a and the concave lens 71 are determined so that the coherent light is not incident on a position deviated from the incident region 55a. Similarly, only coherent light from the laser light source 61b is incident on a predetermined position of the incident area 55b, and the image 5 of the scattering plate 6 is reproduced over the entire illuminated area LZ. Further, only the coherent light from the laser light source 61c is incident on a predetermined position of the incident region 55c, and the image 5 of the scattering plate 6 is reproduced over the entire illuminated region LZ.

  Eventually, the illuminated region LZ is simultaneously illuminated with coherent light from the incident region 55a, coherent light from the incident region 55b, and coherent light from the incident region 55c that are not coherent with each other.

  In this way, each coherent light whose traveling direction is adjusted by the concave lens 71 is reproduced illumination light La (see FIG. 4) that can form one light beam diverging from the reference point SP, and the hologram recording medium 55 of the optical element 50. Can be incident. As a result, coherent light beams having no interference from the laser light sources 61a, 61b, and 61c are incident on three positions on the hologram recording medium 55, and are incident on the respective positions on the hologram recording medium 55. The image 5 of the scattering plate 6 having coherent light having the same contour is reproduced simultaneously at the same position (illuminated region LZ).

  FIG. 5 shows the configuration of the illumination device 40 shown in FIG. 2 as a perspective view. In the example shown in FIG. 5, the incident points IP1, IP2, and IP3 of the coherent light from the irradiation device 60 to the optical element 50 are XY coordinate systems defined on the plate surface of the hologram recording medium 55, that is, XY. The plane is located on a straight line parallel to the X axis of the XY coordinate system that is parallel to the plate surface of the hologram recording medium 55. In FIG. 5, the description of the reproduction light Lb from the incident point IP2 is omitted for clarity.

  As a practical problem, the hologram recording material 58 may shrink when the hologram recording medium 55 is produced. In such a case, it is preferable to adjust the incident / exit angle of the coherent light irradiated from the irradiation device 60 to the optical element 50 in consideration of the shrinkage of the hologram recording material 58. Therefore, the wavelength of the coherent light generated by the laser light sources 61a, 61b, and 61c does not need to be exactly the same as the wavelength of the light used in the exposure process (recording process) in FIG. 3, and may be substantially the same. .

  For the same reason, even if the traveling direction of the light incident on the hologram recording medium 55 of the optical element 50 does not take exactly the same path as the one light beam included in the divergent light beam from the reference point SP, it is illuminated. The image 5 can be reproduced in the region LZ.

[Effects of basic form]
Next, the operation of the illumination device 40, the projection device 20, and the projection display device 10 having the above-described configuration will be described.

  First, the laser light sources 61a, 61b, and 61c of the irradiation device 60 generate three coherent lights having the same wavelength that travel in parallel. As described above, these coherent lights are not coherent. The traveling direction of these coherent lights can be changed by the concave lens 71. The concave lens 71 causes the coherent lights to be incident on three positions (incident areas) on the hologram recording medium 55 at an incident angle that satisfies the Bragg condition at the positions so as not to overlap each other. As a result, the coherent light incident on the three positions is superimposed on the illuminated region LZ by the diffraction on the hologram recording medium 55, and the image 5 of the scattering plate 6 is simultaneously reproduced. That is, the coherent light that has entered the three positions of the hologram recording medium 55 from the irradiation device 60 is diffused by the optical element 50 and enters the entire illuminated area LZ. In this way, the irradiation device 60 simultaneously illuminates the illuminated area LZ with coherent light having no coherence.

  As shown in FIG. 1, in the projection device 20, the spatial light modulator 30 is arranged at a position overlapping the illuminated area LZ of the illumination device 40. For this reason, the spatial light modulator 30 is illuminated in a planar shape by the illumination device 40, and forms an image by selecting and transmitting the coherent light for each pixel. This image is projected onto the screen 15 by the projection optical system 25. The coherent light projected on the screen 15 is diffused and recognized as an image by the observer. However, at this time, the coherent light projected on the screen interferes by diffusion and causes speckle.

  However, according to the lighting device 40 in the basic mode described here, speckles can be made extremely inconspicuous as described below.

  According to the aforementioned Non-Patent Document 1, it is effective to multiplex parameters such as polarization, phase, angle, and time and increase the mode in order to make speckle inconspicuous. The mode here refers to speckle patterns that are uncorrelated with each other. For example, when coherent light is projected from different directions onto the same screen from a plurality of laser light sources, there are as many modes as the number of laser light sources. When there are a large number of these modes, the interference patterns of light are uncorrelated and averaged, and as a result, speckles observed by the observer's eyes are considered inconspicuous.

  The irradiation device 60 described above irradiates the corresponding position (incident area) of the hologram recording medium 55 of the optical element 50 with three coherent lights having no interference with each other. Further, the coherent light incident on the three positions of the hologram recording medium 55 from the irradiation device 60 simultaneously illuminates the entire illuminated area LZ with the coherent light, but the coherent light illuminates the illuminated area LZ. The illumination directions of light are different from each other.

  Considering the illuminated area LZ as a reference, coherent light enters each position in the illuminated area LZ from three incident directions. As a result, the light forming each pixel of the image formed by the light transmitted through the spatial light modulator 30 is projected to a specific position on the screen 15 with different optical paths (angles).

  From the above, according to the basic form described above, uncorrelated coherent light scattering patterns are multiplexed and observed at each position on the screen 15 displaying an image. Therefore, speckles generated corresponding to each scattering pattern are overlapped and averaged and observed by an observer. Thereby, speckles can be made very inconspicuous for an observer who observes the image displayed on the screen 15.

  Note that conventional speckles observed by humans include not only speckles on the screen caused by scattering of coherent light on the screen 15, but also scattering of coherent light before being projected on the screen. Speckle on the projection device side can also occur. The speckle pattern generated on the projection device side is projected onto the screen 15 via the spatial light modulator 30 so that it can be recognized by the observer. However, according to the basic form described above, coherent light having no coherence incident on three positions of the hologram recording medium 55 illuminates the entire illuminated area LZ on which the spatial light modulator 30 is superimposed. To come. That is, the hologram recording medium 55 forms a new wavefront that is separate from the wavefront used to form the speckle pattern, and the illumination area LZ and further the spatial light modulator 30 are formed in a complex and uniform manner. Through this, the screen 15 is illuminated. Due to the formation of a new wavefront on the hologram recording medium 55, the speckle pattern generated on the projection apparatus side is made invisible.

  By the way, Non-Patent Document 1 described above proposes a method using a numerical value called speckle contrast (unit%) as a parameter indicating the degree of speckle generated on the screen. This speckle contrast is defined as a value obtained by dividing the standard deviation of the actual luminance variation on the screen divided by the average luminance value when displaying a test pattern image that should have a uniform luminance distribution. Amount. That is, this speckle contrast is an amount proportional to the reciprocal of the square root of the number of modes. In this basic form, the number of modes is the number of laser light sources. Therefore, this speckle contrast is proportional to the reciprocal of the square root of the number of laser light sources. The larger the speckle contrast value is, the larger the speckle occurrence level on the screen is, which indicates that the spot-like luminance unevenness pattern is more prominently presented to the observer. That is, as described above, the larger the number of laser light sources, the smaller the speckle contrast value, and the speckle can be made inconspicuous.

  With respect to the projection-type image display device 10 of the basic form described with reference to FIGS. 1 to 5, not only the three laser light sources 61a, 61b, and 61c illustrated, but also more speckles are used. When the contrast was measured, it was 5.0% (Condition 1). Further, as the above-described optical element 50, an uneven shape designed by using a computer so that the image 5 of the scattering plate 6 can be reproduced when receiving specific reproduction illumination light instead of the transmission type volume hologram. The speckle contrast in the case of using a relief hologram as a computer-generated hologram (CGH) having a value of 6.2 was 6.2% (Condition 2). In HDTV (high-definition television) video display applications, a speckle contrast of 6.0% or less is a standard (for example, WO / 2001/081996) as a level at which an uneven brightness pattern is hardly recognized when an observer observes with the naked eye. The basic form described above satisfies this standard to some extent. In addition, when actually observed with the naked eye, brightness unevenness (brightness unevenness) that could be visually recognized did not occur.

  On the other hand, when the laser light from one laser light source is shaped into a parallel light beam and made incident on the spatial light modulator 30 without using a plurality of laser light sources, that is, the projection-type image display device shown in FIG. When coherent light from one laser light source 61a was incident as a parallel light beam on ten spatial light modulators 30 without passing through the optical element 50, the speckle contrast was 20.7% (Condition 3). Under these conditions, a spot-like luminance unevenness pattern was observed quite noticeably by visual observation.

  Further, when the light source 61a is replaced with a green LED (non-coherent light source) and light from the LED light source is incident on the spatial light modulator 30, that is, the projection type video display device 10 shown in FIG. When non-coherent light from one LED light source was incident as a parallel light beam on the spatial light modulator 30 without passing through the optical element 50, the speckle contrast was 4.0% (Condition 4). Under these conditions, brightness unevenness (brightness unevenness) that could be visually recognized by naked eye observation did not occur.

  The results of conditions 1 and 2 were much better than the results of condition 3, and were comparable to the measurement results of condition 4. As already mentioned, the problem of speckle generation is a problem inherent in the case of using a coherent light source such as a laser beam in practice, and it is necessary to consider in an apparatus using a non-coherent light source such as an LED. There is no problem. In addition, in condition 1 and condition 2, as compared with condition 4, an optical element 50 that can cause speckles is added. From these points, it can be said that Condition 1 and Condition 2 were sufficient to cope with speckle defects.

  In addition, according to the basic mode described above, the following advantages can be obtained.

  According to the basic form described above, the optical element 50 for making speckles inconspicuous can also function as an optical member for shaping and adjusting the beam form of coherent light emitted from the irradiation device 60. Therefore, the optical system can be reduced in size and simplified.

  Further, according to the basic form described above, coherent light incident on each position of the hologram recording medium 55 generates an image 5 of the scattering plate 6 at the same position, and is superimposed on the image 5 to generate spatial light. A modulator 30 is arranged. Therefore, the light diffracted by the hologram recording medium 55 can be used for image formation with high efficiency, and the use efficiency of light from the laser light sources 61a, 61b, 61c is excellent.

[Deformation to basic form]
Various modifications can be made to the basic form described based on the specific example illustrated in FIGS. Hereinafter, an example of modification will be described with reference to the drawings. In the drawings used in the following description, the same reference numerals as those used for the corresponding parts in the above-described embodiment are used, and redundant descriptions are omitted.

(Projection device)
In the basic mode, an example in which the spatial light modulator 30 is disposed at a position overlapping the illuminated region LZ has been described, but the spatial light modulator 30 may not be disposed at a position strictly overlapping the illuminated region LZ. . For example, in the configuration of FIG. 1, the spatial light modulator 30 may be disposed closer to the optical element 50 than the illuminated region LZ, or may be disposed closer to the projection optical system 25 than the illuminated region LZ. In other words, the optical element 50 and the spatial light modulator 30 only have to be arranged so that the coherent light that is diffracted by being incident on each incident region of the optical element 50 overlaps and illuminates the spatial light modulator 30.

(Lighting device)
As shown in FIG. 6, the laser light sources 61a, 61b, 61c of the illumination device 60 may be independent laser light sources. In the example of FIG. 6, since the three laser light sources 61a, 61b, and 61c are arranged away from each other, a part of the parallel coherent light from the laser light sources 61a, 61b, and 61c is directly generated by the hologram recording medium 55. Cannot enter. Therefore, the illuminating device 60 serves as an incident-side optical system 70 that guides coherent light to the incident regions 55a, 55b, and 55c of the hologram recording medium 55 between the laser light sources 61a, 61b, and 61c and the hologram recording medium 55. A convex lens 72 is provided. With this convex lens 72, three coherent lights can be converged and irradiated onto the corresponding incident areas 55a, 55b, and 55c of the hologram recording medium 55, respectively. Even with such a configuration, an effect similar to that of the basic mode described above can be obtained. In such an example, a divergent light beam is used as the reference light Lr in place of the above-described convergent light beam in the exposure process when the hologram recording medium 55 is manufactured. The incident side optical system 70 may be a diffractive optical element or a prism.

  In addition, as shown in FIG. 7, the illumination device 60 is replaced with the incident optical system 70 between the laser light sources 61 a, 61 b, 61 c and the corresponding incident areas 55 a, 55 b, 55 c of the hologram recording medium 55. In addition, optical fibers 64a, 64b, and 64c that guide the coherent light to the corresponding incident regions 55a, 55b, and 55c of the hologram recording medium 55 may be provided.

  The coherent light from the laser light source 61a is coupled by the optical coupling part CIa at the incident end of the optical fiber 64a and propagates through the optical fiber 64a, and the corresponding incident light of the hologram recording medium 55 from the optical coupling part COa at the outgoing end. The light is emitted to the region 55a. Similarly, the coherent light from the laser light source 61b is coupled by the optical coupling unit CIb, propagates through the optical fiber 64b, and is emitted from the optical coupling unit COb to the corresponding incident region 55b of the hologram recording medium 55. The coherent light from the laser light source 61c is coupled by the optical coupling unit CIc, propagates through the optical fiber 64c, and is emitted from the optical coupling unit COc to the corresponding incident region 55c of the hologram recording medium 55. The optical fibers 64a, 64b, and 64c may be physically bundled (bundled) at an intermediate portion.

  According to such a configuration, coherent light having no coherency propagates through the corresponding optical fibers, and thus there is no possibility of being mixed with each other during propagation. Therefore, each coherent light can be incident only on the corresponding incident region more reliably. Thereby, speckle can be made inconspicuous more reliably. Furthermore, since the laser light sources 61a, 61b, 61c can be arranged at arbitrary positions, restrictions on the arrangement of the optical system can be reduced, and the illumination device 40 can be downsized.

  Moreover, according to the basic form described above, speckle can be effectively made inconspicuous. However, this effect is mainly due to the lighting device 40. Therefore, the lighting device 40 can be usefully used in various aspects. For example, the illumination device 40 can be used as simple illumination. In this case, brightness unevenness such as brightness unevenness and flickering can be made inconspicuous.

  Moreover, you may use the illuminating device 40 mentioned above as illumination for an image reading apparatus as an example. In such an example, the speckle generated on the target object can be made inconspicuous by arranging the target object to be scanned on the illuminated region LZ of the lighting device 40. As a result, it is possible to eliminate image correction means and the like that are conventionally required.

  When the illuminating device 40 is incorporated in a scanner, the illuminated area LZ by the illuminating device 40 may be a surface as in the above-described form. Alternatively, the illuminated area LZ by the illumination device 40 may be an elongated area or a linear area extending in one direction. In this case, two-dimensional image information can be read by the illuminating device 40 incorporated in the scanner moving relative to the object along a direction orthogonal to the one direction.

  Furthermore, as shown in FIG. 8, the optical element 50 may include a plurality of hologram recording media 55-1, 55-2,... Arranged side by side so as not to overlap. Each of the hologram recording media 55-1, 55-2,... Shown in FIG. 8 is formed in a strip shape, and is arranged side by side with no gap in a direction orthogonal to the longitudinal direction. Further, the hologram recording media 55-1, 55-2,... Are located on the same virtual plane. Each hologram recording medium 55-1, 55-2,... Has an image 5 of the scattering plate 6 in the illuminated areas LZ-1, LZ-2,. Generate, in other words, illuminate the illuminated areas LZ-1, LZ-2,... With coherent light. Each of the illuminated areas LZ-1, LZ-2,... Is formed as an elongated area or a linear area extending in one direction, and arranged side by side in the direction orthogonal to the longitudinal direction without any gap. Yes. In addition, each of the illuminated areas LZ-1, LZ-2,... Is located on the same virtual plane.

  In the example shown in FIG. 8, the illuminated areas LZ-1, LZ-2,... May be illuminated as follows. First, the irradiation device 60 is optical so that each coherent light is incident on a corresponding incident point among the incident points IP1 to IP3 along the longitudinal direction (the one direction) of the first hologram recording medium 55-1. The first hologram recording medium 55-1 of the element 50 is irradiated with the coherent light. The coherent light incident on each position of the first hologram recording medium 55-1 is superimposed on the first illumination area LZ-1 to reproduce the image 5 of the linear or elongated scattering plate 6, and the first One illumination region LZ-1 is illuminated simultaneously with coherent light. When a predetermined time elapses, the irradiation device 60 changes the direction of the laser array 62, for example, and changes the three incident points on the second hologram recording medium 55-2 adjacent to the first hologram recording medium 55-1. Then, instead of the first illuminated area LZ-1, the second illuminated area LZ-2 adjacent to the first illuminated area LZ-1 is illuminated with the coherent light. Thereafter, three incident points on each hologram recording medium are sequentially irradiated with coherent light, and the illuminated area corresponding to the hologram recording medium is illuminated with the coherent light. According to such a method, it is possible to read two-dimensional image information without moving the illumination device. In FIG. 8, only the reproduction light Lb from the incident point IP2 is shown for clarity of explanation.

(Spatial light modulator, projection optical system, screen)
According to the embodiment described above, speckle can be effectively made inconspicuous. However, this effect is mainly due to the lighting device 40. Even if this lighting device 40 is combined with various known spatial light modulators, projection optical systems, screens, etc., speckles can be effectively made inconspicuous. From this point, the spatial light modulator, the projection optical system, and the screen are not limited to those illustrated, and various known members, components, devices, and the like can be used.

(Projection-type image display device)
Moreover, although the example in which the hologram recording medium 55 is manufactured by the interference exposure method using the planar scattering plate 6 having a shape corresponding to the incident surface of the spatial light modulator 30 is shown, the present invention is not limited thereto. The hologram recording medium 55 may be manufactured by an interference exposure method using a scattering plate having a certain pattern. In this case, the image of the scattering plate having a certain pattern is reproduced by the hologram recording medium 55. In other words, the optical element 50 (hologram recording medium 55) illuminates the illuminated area LZ having a certain pattern. When this optical element 50 is used, the spatial light modulator 30 and the projection optical system 25 are also omitted from the basic form described above, and the screen 15 is disposed on the screen 15 by overlapping with the illuminated region LZ. Any pattern recorded on the hologram recording medium 55 can be displayed. Also in this display device, non-coherent coherent light from each of the laser light sources 61a, 61b, 61c is incident only on the corresponding incident region of the hologram recording medium 55, thereby making speckles on the screen 15 inconspicuous. be able to.

  FIG. 9 discloses an example of such an example. In the illustrated example, the optical element 50 includes first to third hologram recording media 55-1, 55-2, and 55-3. The first to third hologram recording media 55-1, 55-2, and 55-3 are arranged on surfaces parallel to the incident surface of the optical element 50 so as not to overlap each other. Each of the hologram recording media 55-1, 55-2, 55-3 can reproduce the image 5 having the outline of the arrow, in other words, the illuminated areas LZ-1, LZ- having the outline of the arrow. 2 and LZ-3 can be illuminated with coherent light. The first to third illuminated areas LZ-1, LZ-2, and LZ-3 respectively corresponding to the hologram recording media 55-1, 55-2, and 55-3 overlap each other on the same virtual plane. It is arranged not to become. In particular, in the illustrated example, the directions indicated by the arrows forming the illuminated areas LZ-1, LZ-2, and LZ-3 are all the same, and the first to third illuminated areas LZ-1, LZ-2 and LZ-3 are positioned in this order. For example, when each coherent light from the irradiation device 60 is simultaneously incident on the corresponding incident points IP1-1 to IP3-1 on the first hologram recording medium 55-1, the first rearmost position is placed. Illuminated area LZ-1 is illuminated. As an example, next, as shown in FIG. 9, for example, by changing the direction of the laser array 62, each coherent light from the irradiation device 60 corresponds to a corresponding incident point IP <b> 1-2 on the second hologram recording medium 55-2. Are incident on the IP3-2 at the same time, and the second illuminated region LZ-2 located in the middle is illuminated. Thereafter, when each coherent light from the irradiation device 60 enters the corresponding incident points IP1-3 to IP3-3 on the third hologram recording medium 55-3 at the same time, the third illuminated object positioned at the foremost position. Area LZ-3 is illuminated. In FIG. 9, only the reproduction light Lb from the incident points IP2-1, IP2-2, and IP2-3 is shown for clarity of explanation.

(Irradiation device)
In the above-described embodiment, an example in which the irradiation device 60 simultaneously irradiates the coherent light to the three incident points positioned on the straight line on the plate surface of the hologram recording medium 55 has been described. As shown in FIG. 10, the incident points IP <b> 1 to IP <b> 3 of the coherent light from the irradiation device 60 to the hologram recording medium 55 may be at arbitrary positions on the plate surface of the hologram recording medium 55. That is, the incident points IP <b> 1 to IP <b> 3 may be two-dimensionally positioned on the plate surface of the hologram recording medium 55. In FIG. 10, the description of the reproduction light Lb from the incident point IP2 is omitted for clarity of explanation. Further, in FIG. 10, three incident points IP <b> 1 to IP <b> 3 are shown to clarify the explanation, but it is preferable that the laser array 62 has more laser light sources as described above. In that case, the laser array 62 may have laser light sources in a matrix, and these laser light sources may emit coherent light to a plurality of incident points positioned in a matrix on the plate surface of the hologram recording medium 55.

  Furthermore, although the laser light sources 61a, 61b, and 61c of the irradiation device 60 have been described on the premise that they oscillate laser light shaped as linear rays, the present invention is not limited to this. In particular, in the above-described form, the coherent light irradiated to each position of the optical element 50 is shaped by the optical element 50 into a light beam that enters the entire illuminated area LZ. Therefore, inconvenience does not occur even if the coherent light irradiated to the optical element 50 from the light sources 61a, 61b, 61c of the irradiation device 60 is not accurately shaped. For this reason, the coherent light generated from the light sources 61a, 61b, and 61c may be diverging light. Further, the cross-sectional shape of the coherent light generated from the light sources 61a, 61b, and 61c may be an ellipse or the like instead of a circle. Furthermore, the transverse mode of the coherent light generated from the light sources 61a, 61b, 61c may be a multimode.

  When the laser light sources 61a, 61b, and 61c generate divergent light beams, the coherent light is incident on a region having a certain area instead of a point when entering the hologram recording medium 55 of the optical element 50. Become. In this case, the light diffracted by the hologram recording medium 55 and incident on each position of the illuminated region LZ is multiplexed with an angle rather than the basic form. Speckle can be made more inconspicuous by such multiplexing of angles.

  Furthermore, although the irradiation apparatus 60 showed the example which injects coherent light into the optical element 50 so that the optical path of one light ray contained in a divergent light beam may be followed in the form mentioned above, it is not restricted to this. For example, in the form shown in FIG. 1, the irradiation device 60 may not include the concave lens 71. In this case, coherent light from each of the laser light sources 61a, 61b, 61c is directly incident only on the corresponding incident region of the hologram recording medium 55 of the optical element 50. That is, the irradiation device 60 causes the coherent light to be incident on the optical element 50 so as to follow the optical path of the light beam constituting the parallel light flux. In such an example, a parallel light beam is used as the reference light Lr instead of the above-described convergent light beam in the exposure process when the hologram recording medium 55 is manufactured. Such a hologram recording medium 55 can be produced and duplicated more easily.

  Further, the irradiation device 60 may include a plurality of light sources that generate coherent light in different wavelength ranges. Even in this case, the irradiation device 60 needs to include a plurality of light sources each generating coherent light having the same wavelength and no interference with each wavelength region. According to this example, a color that is difficult to display with a single laser beam can be generated by additive color mixing, and the illuminated area LZ can be illuminated with that color. Further, in this case, in the projection device 20 or the transmissive image display device 10, the spatial light modulator 30 includes, for example, a color filter, and a modulated image can be formed for each coherent light in each wavelength region. Makes it possible to display images in a plurality of colors. Alternatively, even if the spatial light modulator 30 does not include a color filter, the irradiation device 60 irradiates the coherent light of each wavelength region in a time-sharing manner, and the spatial light modulator 30 is irradiated with the wavelength region. Even when operating in a time-sharing manner so as to form a modulated image corresponding to the coherent light, it is possible to display an image in a plurality of colors. In particular, in the projection device 20 or the transmissive image display device 10, the irradiation device 60 includes a light source that generates coherent light in a wavelength region corresponding to red light, and a light source that generates coherent light in a wavelength region corresponding to green light. In the case where it includes a light source that generates coherent light in a wavelength range corresponding to blue light, it is possible to display an image in full color.

  Note that the hologram recording medium 55 included in the optical element 50 has wavelength selectivity. Therefore, when the irradiation device 60 includes light sources having different wavelength ranges, the hologram recording medium 55 includes the hologram elements corresponding to the wavelength ranges of the coherent light generated by the respective light sources in a stacked state. You may make it. The hologram element for coherent light in each wavelength region is obtained by using, for example, the coherent light in the corresponding wavelength region as exposure light (reference light Lr and object light Lo) in the method already described with reference to FIGS. It can be made by using light. Further, instead of stacking hologram elements in each wavelength region to produce the hologram recording medium 55, the object light Lo and the reference light Lr made of coherent light in each wavelength region are simultaneously exposed to the hologram photosensitive material 58, respectively. A single hologram recording medium 55 may diffract light in a plurality of wavelength ranges.

(Optical element)
In the embodiment described above, an example in which the optical element 50 includes the transmission type volume hologram 55 using a photopolymer has been described, but the present invention is not limited thereto. As already described, the optical element 50 may include a plurality of hologram recording media 55. For example, the optical element 50 shown in FIG. 1 may include three hologram recording media corresponding to the incident areas 55a, 55b, and 55c, and each coherent light may enter only the corresponding hologram recording medium. Further, the optical element 50 may include a volume hologram that is recorded using a photosensitive medium including a silver salt material. Further, the optical element 50 may include a reflection type volume hologram recording medium or a relief type (emboss type) hologram recording medium.

  However, in the relief (embossed) hologram, hologram interference fringes are recorded by the concavo-convex structure on the surface. However, in the case of this relief type hologram, the scattering due to the uneven structure on the surface may cause an unintended new speckle generation in addition to the loss of light amount. In this respect, the volume type hologram is preferable. In the volume hologram, since the hologram interference fringe is recorded as a refractive index modulation pattern (refractive index distribution) inside the medium, it is not affected by scattering due to the uneven structure on the surface.

  However, even volume holograms that are recorded using a photosensitive medium containing a silver salt material may cause scattering due to silver salt particles to cause unintended new speckle generation in addition to light loss. . In this respect, the hologram recording medium 55 is preferably a volume hologram using a photopolymer.

  In addition, in the exposure process shown in FIG. 3, a so-called Fresnel type hologram recording medium is produced. However, a Fourier transform type hologram recording medium obtained by performing recording using a lens may be produced. Absent. However, when a Fourier transform type hologram recording medium is used, a lens may also be used during image reproduction.

  Further, the striped pattern (refractive index modulation pattern or concave / convex pattern) to be formed on the hologram recording medium 55 does not use the actual object light Lo and reference light Lr, but the planned wavelength and incident direction of the reproduction illumination light La. In addition, it may be designed using a computer based on the shape and position of the image to be reproduced. The hologram recording medium 55 obtained in this way is also called a computer-generated hologram. When a plurality of coherent lights having different wavelength ranges are irradiated from the irradiation device 60 as in the above-described modification, the hologram recording medium 55 as a computer-generated hologram corresponds to each coherent light in each wavelength range. The coherent light in each wavelength region may be diffracted in the corresponding region to reproduce an image.

  Further, in the above-described embodiment, the optical element 50 includes the hologram recording medium 55 that expands the coherent light irradiated to each position and illuminates the entire illuminated area LZ using the expanded coherent light. However, the present invention is not limited to this. The optical element 50 changes or diffuses the traveling direction of the coherent light irradiated to each position instead of the hologram recording medium 55 or in addition to the hologram recording medium 55, and diffuses the entire illuminated area LZ with coherent light. You may make it have a lens array or a diffuser as an optical element to illuminate. Specific examples of such a lens array include a total reflection type or a refractive type Fresnel lens or a fly-eye lens provided with a diffusion function. Specific examples of such a diffusion plate include opal glass, frosted glass, or resin diffusion plate provided with a diffusion function. Also in such an illuminating device 40, the irradiation device 60 irradiates the lens array or the diffusion plate with coherent light, and the coherent light incident on each position of the lens array or the diffusion plate from the irradiation device 60 respectively. By configuring the irradiation device 60 and the optical element 50 so that the traveling direction is changed by the lens array or the diffusion plate to illuminate at least the illuminated area LZ, the speckle can be effectively inconspicuous. .

(Lighting method)
In the embodiment described above, the irradiation device 60 is configured to irradiate the coherent light on each position arranged in the one-dimensional direction on the optical element 50, and the hologram recording medium 55, the lens array, or the diffusion plate of the optical element 50 is provided. An example in which the coherent light irradiated to each position is configured to diffuse in a two-dimensional direction and the illumination device 40 illuminates the two-dimensional illuminated region LZ by this is shown. However, as already described, the present invention is not limited to such an example. For example, the irradiation device 60 is configured to irradiate each position on the optical element 50 that is two-dimensionally arranged with coherent light. In addition, the hologram recording medium 55, the lens array, or the diffusing plate of the optical element 50 is configured to diffuse the coherent light irradiated to each position in a two-dimensional direction. The illumination area LZ may be illuminated (aspect already described with reference to FIG. 10).

  Further, as already mentioned, the irradiation device 60 is configured to irradiate each position on the optical element 50 that is aligned in the one-dimensional direction, and the hologram recording medium 55 and the lens of the optical element 50. The array or the diffusion plate may be configured to diffuse the coherent light irradiated to each position in a one-dimensional direction, and thereby the illumination device 40 may illuminate the one-dimensional illuminated area LZ. In this aspect, the arrangement direction of the positions where the coherent light is irradiated by the irradiation device 60 and the diffusion direction of the hologram recording medium 55, the lens array, or the diffusion plate of the optical element may be parallel.

  Further, the irradiation device 60 is configured to irradiate the coherent light on each position arranged in the one-dimensional direction on the optical element 50 or each position arranged two-dimensionally, and the hologram recording medium 55 of the optical element 50, The lens array or the diffusion plate may be configured to diffuse the coherent light irradiated to each position in a one-dimensional direction. In this aspect, as already described, the optical element 50 has a plurality of hologram recording media 55, lens arrays or diffusion plates, and the illuminated areas LZ corresponding to the hologram recording media 55, lens arrays or diffusion plates are sequentially arranged. The illumination device 40 may illuminate a two-dimensional area by illuminating. At this time, each illuminated area LZ may be sequentially illuminated at a speed as if it were illuminated simultaneously by the human eye, or it can be recognized that the illuminated area LZ is also illuminated sequentially by the human eye. It may be illuminated sequentially at such a slow speed.

(Incident side optical system)
The incident side optical system 70 may include an imaging optical system 80.

  FIG. 11 is a diagram for explaining a modification of the incident-side optical system 70, and is a diagram illustrating a schematic configuration of the illumination device, the projection device, and the projection type video display device. As shown in FIG. 11, the incident-side optical system 70 forms an image of each laser light source (coherent light source) 61 a, 61 b, 61 c on the corresponding incident regions 55 a, 55 b, 55 c of the optical element 50. 80. That is, the image of the laser light source 61a is formed on the corresponding incident area 55a, the image of the laser light source 61b is formed on the corresponding incident area 55b, and the image of the laser light source 61c is formed on the corresponding incident area 55c. Image. The image plane 61X of the light source is, for example, a plane parallel to the incident surface of the optical element 50, and is located in the optical element 50.

  The imaging optical system 80 includes a convex lens 81 and a concave lens 82, and the convex lens 81 is disposed on the side close to the laser light sources 61a, 61b, 61c. The coherent light from the laser light sources 61a, 61b, and 61c passes through the convex lens 81 and the concave lens 82 in this order, and enters the optical element 50. The convex lens 81 forms images of the laser light sources 61a, 61b, and 61c on the corresponding incident areas 55a, 55b, and 55c of the optical element 50. The concave lens 82 spreads each coherent light beam from the laser light sources 61a, 61b, 61c of the dense laser array 62, as in the basic form of FIG. That is, the concave lens 82 increases the interval between the coherent light beams in order to reduce speckle.

  With such a configuration, each coherent light from each laser light source 61a, 61b, 61c is reliably transmitted only to the corresponding incident region 55a, 55b, 55c on the hologram recording medium 55 of the optical element 50, as compared with the basic form described above. Incident. Therefore, different speckle patterns can be generated on the screen 15 more reliably. Since these speckle patterns are spatially superimposed without interference, speckles generated by the diffusion of coherent light are superimposed and become inconspicuous.

  FIG. 12 is a diagram for explaining another modified example of the incident-side optical system 70, and is a diagram illustrating a schematic configuration of an illumination device, a projection device, and a projection type video display device. As shown in FIG. 12, in this modification, the imaging optical system 80 has a concave lens 83 and a convex lens 84, and the concave lens 83 is arranged on the side close to the laser light sources 61a, 61b, 61c. Different from the example of FIG. As in the example of FIG. 11, the imaging optical system 80 forms images of the laser light sources 61 a, 61 b, 61 c on the corresponding incident areas 55 a, 55 b, 55 c of the optical element 50.

  The coherent light that is parallel light from the laser light sources 61a, 61b, and 61c is diverged by the concave lens 83, and is then made parallel light again by the convex lens 84. The convex lens 84 forms images of the laser light sources 61a, 61b, and 61c on the corresponding incident areas 55a, 55b, and 55c of the optical element 50. That is, according to this configuration, each coherent light can be efficiently separated and incident only on the corresponding incident regions 55a, 55b, and 55c of the optical element 50. As in the example of FIG. 11, different speckle patterns can be generated on the screen 15 more reliably.

  Also in this example, the image plane 61X of the light source is, for example, a plane parallel to the incident surface of the optical element 50 and is located in the optical element 50. The imaging optical system 80 may be configured using one lens or three or more lenses.

(Combination of modified examples)
In addition, although the some modification with respect to the basic form mentioned above has been demonstrated above, naturally, it is also possible to apply combining several modifications suitably.

5 Image 6 Scattering plate 10 Projection display device 15 Screen 20 Projection device 25 Projection optical system 30 Spatial light modulator 40 Illumination device 50 Optical element 55 Hologram recording medium 58 Hologram photosensitive material 60 Irradiation devices 61a, 61b, 61c Laser light source ( Coherent light source)
62 Laser array 64a, 64b, 64c Optical fiber 70 Incident side optical system 71 Concave lens 72 Convex lens 80 Imaging optical system 81, 84 Convex lens 82, 83 Concave lens LZ Illuminated area

Claims (14)

An optical element capable of diffusing coherent light;
A plurality of coherent light sources that emit coherent light of the same wavelength, and
The optical element has a plurality of incident areas;
The coherent light from each coherent light source is incident on a corresponding incident region of the optical element;
The coherent light that has entered and diffused into each incident region of the optical element illuminates regions that overlap each other at least in part.   The illumination apparatus according to claim 1, further comprising an incident side optical system that guides the coherent light to each incident region of the optical element between the plurality of coherent light sources and the optical element.   The illumination apparatus according to claim 2, wherein the incident side optical system includes an imaging optical system that forms an image of each of the coherent light sources in a corresponding incident region of the optical element.   The illumination device according to claim 1, further comprising an optical fiber that guides the coherent light to a corresponding incident region of the optical element between each coherent light source and the corresponding incident region of the optical element.   The illumination device according to claim 1, wherein the optical element is a hologram recording medium.   The illumination device according to claim 1, wherein the optical element is a lens array that changes a traveling direction of incident light.   The illumination device according to claim 1, wherein the optical element is a diffusion plate that changes a traveling direction of incident light.   The lighting device according to claim 7, wherein the diffusion plate is opal glass, ground glass, or a resin diffusion plate.   The illumination device according to any one of claims 1 to 8, wherein the plurality of coherent light sources are built in a laser array.   The illuminating device according to claim 1, wherein the plurality of coherent light sources are independent laser light sources. The lighting device according to any one of claims 1 to 10,
A spatial light modulator disposed at a position illuminated by coherent light from the illumination device.   The projection apparatus according to claim 11, further comprising a projection optical system that projects a modulated image obtained on the spatial light modulator onto a screen. A projection device according to claim 11 or 12,
And a screen on which a modulated image obtained on the spatial light modulator is projected. The lighting device according to any one of claims 1 to 10,
A projection-type image display device comprising: a screen disposed at a position illuminated by coherent light from the illumination device.

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