JP2012113221A - Illuminator, projection device and projection type video display apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illuminator which can make speckles non-outstanding.SOLUTION: An illuminator 40 includes an optical element 50 in which each point thereof can diffuse coherent light to at least the whole of a region to be illuminated, and an irradiation unit 60 which irradiates the optical element with coherent light so that the coherent light scans the surface of the optical element. The optical element has a support base material 53. The support base material has a heat absorption layer 53a which absorbs heat of the optical element.

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. 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.

A first lighting device according to the present invention comprises:
An optical element in which each point can diffuse coherent light over at least the entire illuminated area;
An irradiation device for irradiating the optical element with the coherent light so that the coherent light scans the surface of the optical element;
The optical element has a support substrate;
The support substrate has a heat absorption layer that absorbs heat of the optical element.

In the first lighting device according to the present invention,
The optical element includes a hologram recording medium capable of reproducing an image of a scattering plate,
The irradiation device irradiates the optical element with the coherent light so that the coherent light scans on the hologram recording medium,
The irradiation device and the optical element are arranged so that the coherent light incident on each position of the hologram recording medium from the irradiation device reproduces an image superimposed on the illuminated area, respectively.
The support substrate supports the hologram recording medium;
The heat absorption layer may absorb heat of the hologram recording medium.

  In the first illumination device according to the present invention, the hologram recording medium is a reflection-type hologram recording medium, the support base is provided on the back side of the incident surface of the hologram recording medium, and further includes a light absorption layer. You may make it have.

  In the first illumination device according to the present invention, the light absorption layer and the heat absorption layer of the support base material may be arranged in this order from the incident surface side of the coherent light.

  In the first illumination device according to the present invention, the hologram recording medium is a reflection type hologram recording medium, the support base is provided on the back side of the incident surface of the hologram recording medium, and the heat absorption layer is Further, it may have a light absorbing function.

  In the first illumination device according to the present invention, the hologram recording medium may be a transmissive hologram recording medium, and the support base may have a frame shape having an opening.

  In the first illuminating device according to the present invention, the irradiation device changes the traveling direction of the coherent light from the light source that generates the coherent light, and the coherent light scans the hologram recording medium. And a scanning device for doing so.

In the first lighting device according to the present invention,
The optical element includes a lens array that changes a traveling direction of incident light,
The irradiation device irradiates the optical element with the coherent light so that the coherent light scans on the lens array,
The irradiation apparatus and the optical element are arranged so that the coherent light incident on each position of the optical element from the irradiation apparatus is changed in the traveling direction by the lens array to illuminate at least the entire illuminated area. Have been
The support substrate supports the lens array;
The heat absorption layer may absorb heat of the lens array.

  In the first lighting device according to the present invention, the support base material may have a frame shape having an opening.

  In the first illumination device according to the present invention, the irradiation device scans the lens array by changing a traveling direction of the coherent light from the light source that generates the coherent light and the coherent light. And a scanning device.

A first projection device according to the present invention comprises:
Any of the first lighting devices according to the invention described above;
A spatial light modulator disposed at a position overlapping the illuminated area and illuminated by the illumination device.

  The first projection device according to the present invention may further include a projection optical system that projects a modulated image obtained on the spatial light modulator onto a screen.

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

A second projection type video display device according to the present invention is:
Any of the first lighting devices according to the invention described above;
And a screen disposed at a position overlapping the illuminated area.

  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 for explaining the operation of the lighting apparatus shown in FIG. FIG. 6 is a view showing a modification of the optical element of FIG. FIG. 7 is a diagram showing a modification of the illumination device, the projection device, and the projection type video display device of FIG. FIG. 8 is a plan view of the back surface side of the incident surface of the optical element of FIG. FIG. 9 is a view showing a modification of the optical element of FIG. FIG. 10 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. 11 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. 12 is a view corresponding to FIG. 5, and is a perspective view for explaining a modified example of the irradiation apparatus and its operation. FIG. 13 is a view corresponding to FIG. 2, and is a perspective view for explaining another modification of the irradiation apparatus and its operation.

  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.

  FIGS. 1-13 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. Thereafter, an example of a modification to the illumination device, the projection device, and the projection type video display device according to the basic mode will be described with reference to FIGS. 6 to 13 as appropriate.

<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 scaled (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 display apparatus 10 described here, the illumination apparatus 40 described below illuminates the illuminated area LZ on which the spatial light modulator 30 is superimposed with coherent light that changes in angle with time. It is like that. More specifically, the illuminating device 40 described below illuminates the illuminated region LZ with diffused light composed of coherent light, and the incident angle of this diffused light changes over time. As a result, the diffusion pattern of the coherent light on the screen 15 also changes with time, and speckles generated by the diffusion of the coherent light are temporally superimposed and become inconspicuous. Hereinafter, such an illuminating device 40 will be described in more detail.

  The illumination device 40 shown in FIGS. 1 and 2 includes an optical element 50 that directs the traveling direction of the coherent light toward the illuminated region LZ, and an irradiation device 60 that irradiates the optical element 50 with the coherent light. . 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 includes a protective layer 51, a hologram recording medium 55, an adhesive layer 52, and a support base material 53. The support base 53 is provided on the back side of the incident surface of the hologram recording medium 55 and supports the hologram recording medium 55. The support base 53 is fixed to the hologram recording medium 55 by an adhesive layer 52. In the illustrated example, the support base 53 is formed of a heat absorption layer 53a. The heat absorption layer 53a is made of, for example, a heat conducting element such as a copper radiator plate (heat sink) or a Peltier element, and absorbs heat generated in the hologram recording medium 55. The protective layer 51 is made of, for example, a film or glass, and is provided on the incident surface of the hologram recording medium 55 to protect the incident surface.

  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.

  On the other hand, the irradiation device 60 irradiates the optical element 50 with the coherent light so that the coherent light of the hologram recording medium 55 scans the hologram recording medium 55 of the optical element 50. Therefore, the region on the hologram recording medium 55 that is irradiated with the coherent light by the irradiation device 60 at a certain moment is a part of the surface of the hologram recording medium 55, and in particular in the illustrated example, a minute region to be called a point. It has become.

  Then, the coherent light irradiated from the irradiation device 60 and scanned on the hologram recording medium 55 is diffracted by the hologram recording medium 55 at each position (each point or each region (hereinafter the same)) on the hologram recording medium 55. Incidence is made at an incident angle that satisfies the conditions. In particular, as shown in FIG. 2, the coherent light incident on each position of the hologram recording medium 55 from the irradiation device 60 is superimposed on the illuminated region LZ to reproduce the image 5 of the scattering plate 6. . That is, the coherent light that has entered the hologram recording medium 55 from the irradiation device 60 is diffused (expanded) by the optical element 50 and enters the illuminated area LZ. In FIG. 2 and FIGS. 4 and 5 described below, the components other than the hologram recording medium 55 of the optical element 50 are omitted in order to clarify the function of the hologram recording medium 55.

  In the illustrated example, a reflection 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 reflection type, the object light Lo is incident on the hologram photosensitive material 58 from the surface opposite to 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. It is recorded on the hologram recording material 58 as a pattern (in the case of a volume hologram, for example, 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 Bragg 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 55 that has the same positional relationship as (see FIG. 3).

  At this time, the reproduction light (light obtained by diffracting the reproduction illumination light La by the hologram recording medium 55) Lb that generates the reproduction image 5 of the scattering plate 6 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 object 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. Is spreading (spreading). 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 light source 61a that generates coherent light in a specific wavelength range, and a scanning device 65 that changes the traveling direction of the coherent light from the laser light source 61a. Have. 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 hologram recording medium 55 of the optical element 50.

  In particular, in the example shown in FIG. 2, the scanning device 65 includes a reflective device 66 having a reflective surface 66a that can be rotated about one axis RA1. More specifically, the reflection device 66 is configured as a mirror device having a mirror as a reflection surface 66a that can be rotated about one axis RA1. As shown in FIGS. 2 and 5, the mirror device 66 changes the traveling direction of coherent light from the laser light source 61a by changing the orientation of the mirror 66a. At this time, as shown in FIG. 2, the mirror device 66 generally receives coherent light from the laser light source 61a at the reference point SP. For this reason, the coherent light whose traveling direction is finally adjusted by the mirror device 66 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, the coherent light from the irradiation device 60 scans on the hologram recording medium 55, and the image of the scattering plate 6 in which the coherent light incident on each position on the hologram recording medium 55 has the same contour. 5 is reproduced at the same position (illuminated area LZ).

  The mirror device 66 shown in FIG. 2 is configured to rotate the mirror 66a along one axis line RA1. 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 rotation axis RA <b> 1 of the mirror 66 a has an XY coordinate system defined on the plate surface of the hologram recording medium 55 (that is, the XY plane is parallel to the plate surface of the hologram recording medium 55. It extends parallel to the Y axis of the (XY coordinate system). Then, since the mirror 66a rotates around the axis line RA1 parallel to the Y axis of the XY coordinate system defined on the plate surface of the hologram recording medium 55, the coherent light from the irradiation device 60 is applied to the optical element 50. The incident point IP reciprocates in a direction parallel to the X axis of the XY coordinate system defined on the plate surface of the hologram recording medium 55. That is, in the example shown in FIG. 5, the irradiation device 60 irradiates the optical element 50 with coherent light so that the coherent light scans on the hologram recording medium 55 along a linear path.

  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 wavelength 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 coherent light source 61a does not need to be exactly the same as the wavelength of the light used in the exposure process of 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. Actually, in the example shown in FIGS. 2 and 5, the mirror (reflecting surface) 66a of the mirror device 66 constituting the scanning device 65 is inevitably deviated from the rotation axis RA1. Therefore, when the mirror 66a is rotated around the rotation axis RA1 that does not pass through the reference point SP, the light incident on the hologram recording medium 55 may not be a single light beam that forms a divergent light beam from the reference point SP. is there. However, in practice, the image 5 can be substantially reproduced by being superimposed on the illuminated region LZ by coherent light from the irradiation device 60 having the illustrated configuration.

[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 irradiation device 60 irradiates the optical element 50 with coherent light so that the coherent light scans the hologram recording medium 55 of the optical element 50. Specifically, coherent light having a specific wavelength traveling along a certain direction is generated by the laser light source 61 a, and the traveling direction of the coherent light is changed by the scanning device 65. The scanning device 65 causes coherent light having a specific wavelength to enter each position on the hologram recording medium 55 at an incident angle that satisfies the Bragg condition at the position. As a result, the coherent light incident at each position is superimposed on the illuminated region LZ by the diffraction at the hologram recording medium 55 to reproduce the image 5 of the scattering plate 6. That is, the coherent light that has entered the hologram recording medium 55 from the irradiation device 60 is diffused (expanded) by the optical element 50 and enters the entire illuminated area LZ. In this way, the irradiation device 60 illuminates the illuminated area LZ with coherent light.

  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. In addition, when coherent light from the same laser light source is projected onto the screen from different directions by dividing the time, the mode is the same as the number of times the incident direction of the coherent light has changed during the time that cannot be resolved by the human eye. Will exist. 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.

  In the irradiation device 60 described above, the optical element 50 is irradiated with the coherent light so as to scan the hologram recording medium 55. The coherent light incident on each position of the hologram recording medium 55 from the irradiation device 60 illuminates the entire illuminated area LZ with the coherent light, but the illumination of the coherent light that illuminates the illuminated area LZ. The directions are different from each other. Since the position on the hologram recording medium 55 where the coherent light enters changes with time, the incident direction of the coherent light to the illuminated region LZ also changes with time.

  Considering the illuminated area LZ as a reference, coherent light constantly enters each position in the illuminated area LZ, but the incident direction constantly changes as indicated by an arrow A1 in FIG. It will be. 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 while changing the optical path over time as indicated by an arrow A2 in FIG. Will come to be.

  The coherent light continuously scans on the hologram recording medium 55. Accordingly, the incident direction of the coherent light from the irradiation device 60 to the illuminated region LZ also changes continuously, and the incident direction of the coherent light from the projection device 20 to the screen 15 also changes continuously. Here, if the incident direction of the coherent light from the projection device 20 to the screen 15 changes only slightly (for example, several degrees), the speckle pattern generated on the screen 15 also changes greatly, and an uncorrelated speckle pattern. Are sufficiently superimposed. In addition, the frequency of scanning devices 65 such as MEMS mirrors and polygon mirrors that are commercially available is usually several hundred Hz or higher, and scanning devices 65 that reach tens of thousands of Hz are not uncommon.

  From the above, according to the basic form described above, the incident direction of the coherent light changes temporally at each position on the screen 15 displaying an image, and this change is caused by human eyes. As a result, a non-correlated coherent light scattering pattern is multiplexed and observed by the human eye. 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 mode described above, the coherent light continuously scans on the hologram recording medium 55, and the coherent light incident on each position of the hologram recording medium 55 is superimposed on the spatial light modulator 30, respectively. The entire illuminated area LZ is illuminated. 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. 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.

  The speckle contrast of the basic projection type image display apparatus 10 described with reference to FIGS. 1 to 5 was 3.0% (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 reflective volume hologram. The speckle contrast in the case of using the relief type hologram as a computer-generated hologram (CGH) having a ratio of 3.7% was (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 sufficiently satisfies this standard. 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 the laser light source is shaped into a parallel light beam and incident on the spatial light modulator 30, that is, the spatial light modulator 30 of the projection display apparatus 10 shown in FIG. When the coherent light from the laser light source 61a was made incident as a parallel light beam without passing through 65 or 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 the non-coherent light from the LED light source was incident as a parallel light beam on the spatial light modulator 30 without passing through the scanning device 65 and 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 Condition 1 and Condition 2 were much better than the results of Condition 3, and were also better than 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.

  As described above, the coherent light is applied to the optical element 50 so as to scan the hologram recording medium 55. Accordingly, the hologram recording medium 55 generates heat due to the energy of the coherent light. In particular, since the screen 15 in the projection display apparatus 10 (that is, the illuminated region LZ in the illumination device 40) is preferably sufficiently bright, high-energy coherent light can be used. As a result, the amount of heat generated by the hologram recording medium 55 increases. Here, according to this basic form, the heat absorption layer 53 a provided on the back side of the incident surface of the hologram recording medium 55 absorbs heat generated in the hologram recording medium 55. Specifically, for example, when a heat sink or a Peltier element made of copper is used as the heat absorption layer 53a, these function to absorb the heat of the hologram recording medium 55 and dissipate it to the outside. Thereby, the temperature of the hologram recording medium 55 can be lowered.

  On the other hand, when the heat absorption layer 53a is not provided, the following problem may occur. That is, the hologram recording medium 55 gradually deteriorates due to continuous heat generation, and may eventually be damaged. Further, the hologram recording medium 55 may gradually expand or contract due to continuous heat generation, and the interference fringes may change, or molecular diffusion may occur and the contrast of the interference fringes may be lowered. As the light diffracted in (2) diffuses outside the illuminated area LZ, there is a possibility that the brightness and accuracy will decrease. Thus, the durability of the hologram recording medium 55 may be reduced by heat. According to this basic form, these problems can be effectively prevented, and the durability of the hologram recording medium 55 can be improved.

  Further, 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 light source 61a is excellent.

  Note that the heat absorption layer 53 a may not be provided on the entire back surface side of the hologram recording medium 55 as long as the heat absorption function necessary for the heat generation amount of the hologram recording medium 55 can be exhibited. That is, for example, the heat absorption layer 53a may have an opening. Alternatively, the heat absorption layer 53 a may be provided not on the back side of the incident surface of the hologram recording medium 55 but on the peripheral edge of the hologram recording medium 55. Thereby, the optical element 50 can be made inexpensive.

[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.

(Avoiding zero-order light)
In the basic form described above, part of the coherent light from the irradiation device 60 passes through the hologram recording medium 55 without being diffracted by the hologram recording medium 55 (so-called zero-order light). If zero-order light transmitted through such an optical element 50 enters the illuminated region LZ for some reason, an abnormal region (a point-like region, where the brightness (luminance) increases sharply compared to the surroundings, (Linear area, planar area) occurs in the illuminated area LZ.

  In the basic form, the optical path of the 0th-order light L101 that passes through the hologram recording medium 55 without being diffracted by the hologram recording medium 55 out of the coherent light incident on the hologram recording medium 55 from the irradiation device 60 is It deviates from the illumination area LZ. That is, the 0th-order light L101 of the coherent light that has entered the hologram recording medium 55 from the irradiation device 60 does not directly enter the illuminated region LZ. Thereby, it is possible to prevent an abnormal region (a dotted region, a linear region, a planar region) in which the brightness (luminance) increases sharply compared with the surroundings from occurring in the illuminated region LZ, The in-plane distribution of brightness can be made uniform. Moreover, in the projection apparatus 20 and the projection type video display apparatus 10, it is possible to display a scheduled video with high quality. Furthermore, when a laser light source that oscillates a laser beam having a high energy density is used as the light source of the irradiation device 60, it is very preferable in terms of safety.

  Here, in the modification of the optical element 50 shown in FIG. 6, the problem caused by the 0th-order light L101 is more reliably prevented. In the optical element 50, the protective layer 51, the hologram recording medium 55, the adhesive layer 52, the light absorbing layer 53b, the adhesive layer 52, and the heat absorbing layer 53a are arranged in this order from the incident surface side of the coherent light. The heat absorption layer 53 a and the light absorption layer 53 b function as the support base material 53. On the optical path of the 0th-order light L101 after passing through the hologram recording medium 55, a light absorption layer 53b that absorbs the 0th-order light L101 is provided. For this reason, it can prevent more reliably that the coherent light L101 which could not change the advancing direction to the direction anticipated in the optical element 50 enters into the to-be-illuminated area | region LZ from the direction which is not intended. In addition, when a laser light source that oscillates a laser beam with high energy density is used as the light source of the irradiation device 60, the zero-order light L101 is always irradiated to a certain place, for example, a part of the casing of the lighting device 40. As a result, it is possible to effectively prevent the casing of the lighting device from being damaged. Further, if the light absorption layer 53b can stably prevent the leakage of the coherent light, the output of the coherent light from the irradiation device 60 can be increased, and the illumination device 40 can uniformly and brightly illuminate the illuminated region LZ. In addition, the projection device 20 and the projection-type image display device 10 can brightly display a high-quality image without luminance unevenness.

  In particular, in the illustrated example, the light absorption layer 53b is disposed on the optical path of the 0th-order light L101 immediately after passing through the hologram recording medium 55. That is, it is arranged on the optical path of the 0th-order light L101 after passing through the hologram recording medium 55 and before changing the traveling direction by reflection or refraction. Since the coherent light can be dispersed without much reflection and refraction, the light absorption layer 53b in the example shown in FIG. 6 is very effective for the 0th-order light L101 transmitted through the hologram recording medium 55. Can be effectively suppressed from occurring due to the fact that the zero-order light L101 is absorbed unintentionally and leaks unintentionally.

  Note that the light absorption layer 53b is not particularly limited, and a member capable of widely absorbing coherent light can be used. Specifically, a black light-absorbing rubber material or an inorganic oxide (for example, black anodized aluminum) can be used.

  In the example illustrated in FIG. 6, an example in which two layers of the heat absorption layer 53 a and the light absorption layer 53 b are provided has been described. However, one layer having a heat absorption function and a light absorption function may be provided. . For example, the heat absorption layer 53a may further have a light absorption function.

  Furthermore, in the optical element 50, the protective layer 51, the hologram recording medium 55, the adhesive layer 52, the heat absorption layer 53a, the adhesive layer 52, and the light absorption layer 53b may be arranged in this order from the incident surface side of the coherent light. . In this arrangement, when the heat absorption layer 53a is made of a material that reflects coherent light, an opening is provided in the heat absorption layer 53a, and the opening is scanned with the coherent light. Thereby, the 0th-order light L101 transmitted through the hologram recording medium 55 can be absorbed by the light absorption layer 53b through the opening of the heat absorption layer 53a. When the heat absorption layer 53a is made of a material that transmits coherent light, it is not necessary to provide an opening in the heat absorption layer 53a.

(Transmission type hologram recording medium)
In the basic mode, an example of using a reflection type hologram recording medium has been described, but a transmission type hologram recording medium may be used.

  The projection display apparatus 10 shown in FIG. 7 is different from the basic form only in the optical element 50a. For other parts that can be configured in the same way as the already described configuration, the same reference numerals as those used for the already described configuration are used, and redundant description is omitted.

  In the example shown in FIG. 7, in the optical element 50a, the protective layer 51, the transmissive hologram recording medium 55a, the adhesive layer 52, and the support substrate 53 are arranged in this order from the incident surface side of the coherent light. In the illustrated example, the support base 53 is formed of a heat absorption layer 53a. The support base 53 has a frame shape having an opening. That is, the heat absorption layer 53a has an opening so that the coherent light that illuminates the illuminated region LZ is not blocked by diffraction on the hologram recording medium 55a.

  As shown in FIG. 8, when the optical element 50a is observed from the back side of the incident surface, an opening OP is formed at the center of the heat absorption layer 53a, and the hologram recording medium 55a is exposed at the opening OP. . The cross section of the optical element 50a in FIG. 7 corresponds to the AA cross section in FIG.

  Similar to the basic form, the hologram recording medium 55a can reproduce the image of the scattering plate by diffracting the reproduction illumination light incident on each position, in other words, each minute region that should be called each point. It is like that. Therefore, by scanning the coherent light along the scanning path shown in FIG. 8, the coherent light transmitted through the hologram recording medium 55a is diffused from the opening OP portion of the heat absorption layer 53a to the entire illuminated area LZ. Incident. Since other operations are the same as those of the basic mode, description thereof is omitted.

  Thereby, like the basic form, speckles can be made extremely inconspicuous for an observer who observes an image displayed on the screen 15.

  Further, as in the basic mode, the heat absorption layer 53a functions to absorb the heat of the hologram recording medium 55a and dissipate it to the outside. Therefore, since the temperature of the hologram recording medium 55a can be lowered, the deterioration of the characteristics of the hologram recording medium 55 due to heat can be prevented and its durability can be improved, as in the basic mode.

  Thus, even if the transmission type hologram recording medium 55a is used, the same effect as that of the basic mode can be obtained.

  Note that the shape of the opening OP of the heat absorption layer 53a is not limited to the circular shape described above, and may be an arbitrary shape. For example, as shown in FIG. 9A, four square openings OP may be provided in the heat absorption layer 53a. This figure is also a plan view showing the back side of the incident surface of the optical element 50a. With this configuration, the heat dissipation performance at the central portion of the hologram recording medium 55a can be improved as compared with the case where the opening OP is circular. In this case, for example, coherent light may be scanned along the scanning path 1 on the incident surface side or scanned along the scanning path 2. The scanning paths 1 and 2 are paths that span the two openings OP, respectively. For example, different diffusion plate images corresponding to the scanning path can be obtained by recording different diffusion plate images in the area corresponding to the scanning path 1 and the area corresponding to the scanning path 2 of the hologram recording medium 55a. You can also.

  Alternatively, two coherent light sources 61 a may be used to simultaneously scan two coherent lights along the scanning path 1 and the scanning path 2. For example, two coherent lights can be obtained by recording a diffusion plate image that illuminates the same illuminated area LZ in an area corresponding to the scanning path 1 and an area corresponding to the scanning path 2 of the hologram recording medium 55a. It is possible to illuminate the illuminated area LZ more brightly than when one coherent light is used without increasing the energy of.

  Here, for example, when scanning along the scanning path 1, a part 53 a P of the heat absorption layer 53 a overlaps an intermediate portion of the scanning path 1. Therefore, even when the coherent light is scanned over the portion 53aP of the heat absorption layer 53a, the coherent light transmitted through the hologram recording medium 55a is blocked by the portion 53aP of the heat absorption layer 53a, The illumination area LZ cannot be illuminated. Therefore, the coherent light source 61a may be turned off so as not to irradiate the coherent light at the timing when the coherent light scans the portion where the part 53aP of the heat absorption layer 53a overlaps. Further, when scanning the portion overlapping the part 53aP of the heat absorption layer 53a, the speed of scanning the coherent light may be increased. Thereby, the utilization efficiency of the coherent light from the coherent light source 61a can be improved.

  In addition, as shown in FIG. 9B, three rectangular openings OP may be provided in the heat absorption layer 53a in a slit shape. In this case, the coherent light may be scanned along any one of the scanning paths 1 to 3. The scanning paths 1 to 3 are paths in the opening OP, respectively. Thus, by scanning the coherent light so as not to overlap the heat absorption layer 53a, the utilization efficiency of the coherent light from the coherent light source 61a can be increased. Alternatively, the scanning paths 1 to 3 may be scanned simultaneously using three coherent lights.

  Furthermore, the plurality of openings OP of the heat absorption layer 53a may not have the same shape as shown in FIGS. 9A and 9B, and may not be evenly arranged.

Furthermore, in the optical element 50a, the support base 53 (heat absorption layer 53a), the adhesive layer 52, the transmission hologram recording medium 55a, and the protective layer 51 may be arranged in this order from the incident surface side of the coherent light. .
Alternatively, as long as the heat absorption function necessary for the heat generation amount of the hologram recording medium 55a can be exhibited, the heat absorption layer 53a is not provided on the incident surface side and the back surface side of the hologram recording medium 55a. You may be provided in the peripheral part. Thereby, the utilization efficiency of the coherent light from the coherent light source 61a can be improved.

  As described above, when zero-order light enters the illuminated area LZ, an abnormal area (a dotted area, a linear area, a planar area) in which the brightness (luminance) increases sharply as compared with the surrounding area. Region) occurs in the illuminated region LZ. When the reflection type hologram recording medium 55 is used, the spatial light modulator 30 and the projection optical system 25 are not arranged in the direction in which the zero order light travels, and therefore the zero order light can be avoided relatively easily. When the hologram recording medium 55a is used, it is highly possible that the spatial light modulator 30 and the projection optical system 25 are arranged in a direction close to the direction in which the 0th-order light travels, and caution is required. Specifically, the scanning device 65, the spatial light modulator 30, and the projection optical system 25 are controlled according to the travel path of the zero-order light so that the zero-order light does not pass through the spatial light modulator 30 and the projection optical system 25. It is necessary to design the location.

(Lighting device)
According to the embodiment 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, and in this case, unevenness in brightness (luminance unevenness, flicker) can be made inconspicuous.

  Moreover, you may use the illuminating device 40 mentioned above as illumination for scanners (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 region LZ by the illumination device 40 may be an elongated region (region also called a linear shape) 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. 10, 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. 10 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 extending in one direction (an area that is also referred to as a linear shape), and is arranged side by side in a direction orthogonal to the longitudinal direction. ing. In addition, each of the illuminated areas LZ-1, LZ-2,... Is located on the same virtual plane.

  In the example shown in FIG. 10, the illuminated areas LZ-1, LZ-2,... May be illuminated as follows. First, the irradiation device 60 repeatedly scans the path along the longitudinal direction (the one direction) of the first hologram recording medium 55-1 so that the coherent light repeatedly scans the first hologram recording medium 55-of the optical element 50. 1 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 area LZ-1 is illuminated with coherent light. When a predetermined time elapses, the irradiation device 60 irradiates the second hologram recording medium 55-2 adjacent to the first hologram recording medium 55-1 with the coherent light, and the first illuminated region LZ-1 Instead, the second illuminated area LZ-2 adjacent to the first illuminated area LZ-1 is illuminated with coherent light. Hereinafter, the hologram recording medium is 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.

(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, the speckles on the screen 15 can be made inconspicuous by the irradiation device 60 irradiating the optical element 50 with the coherent light so that the coherent light scans the hologram recording medium 55. .

  FIG. 11 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 the coherent light from the irradiation device 60 is scanning on the first hologram recording medium 55-1, the first illuminated region LZ-1 located at the rearmost side is illuminated. As an example, next, as shown in FIG. 11, the coherent light from the irradiation device 60 scans on the second hologram recording medium 55-2, and the second illuminated region LZ-2 located in the middle is formed. Illuminated. Thereafter, when the coherent light from the irradiation device 60 scans over the third hologram recording medium 55-3, the third illuminated area LZ-3 located in the foremost position is illuminated.

(Irradiation device)
In the embodiment described above, an example in which the irradiation device 60 includes the laser light source 61a and the scanning device 65 has been described. Although the scanning device 65 is an example of the uniaxial rotation type mirror device 66 that changes the traveling direction of the coherent light by reflection, the scanning device 65 is not limited thereto. As shown in FIG. 12, the scanning device 65 has a second rotation in which the mirror (reflection surface 66a) of the mirror device 66 intersects not only the first rotation axis RA1 but also the first rotation axis RA1. It may be rotatable about the axis RA2. In the example shown in FIG. 12, the second rotation axis RA2 of the mirror 66a is a first rotation axis RA1 extending in parallel with the Y axis of the XY coordinate system defined on the plate surface of the hologram recording medium 55. Are orthogonal. Since the mirror 66a is rotatable about both the first axis RA1 and the second axis RA2, the incident point IP of the coherent light from the irradiation device 60 to the optical element 50 is the plate of the hologram recording medium 55. It is possible to move in a two-dimensional direction on the surface. For this reason, as shown in FIG. 12 as an example, the incident point IP of the coherent light to the optical element 50 can be moved on the circumference.

  Further, the scanning device 65 may include two or more mirror devices 66. In this case, even if the mirror 66a of the mirror device 66 can be rotated only about a single axis, the incident point IP of the coherent light from the irradiation device 60 to the optical element 50 is expressed by the hologram recording medium 55. It can be moved in a two-dimensional direction on the plate surface.

  Specific examples of the mirror device 66a included in the scanning device 65 include a MEMS mirror and a polygon mirror.

  The scanning device 65 may include a device other than a reflection device (for example, the mirror device 66 described above) that changes the traveling direction of coherent light by reflection. For example, the scanning device 65 may include a refractive prism, a lens, and the like.

  In the first place, the scanning device 65 is not essential, and the light source 61a of the irradiation device 60 is configured to be displaceable (moving, swinging, rotating) with respect to the optical element 50, and from the light source 61a by the displacement of the light source 61a with respect to the optical element. The irradiated coherent light may be scanned on the hologram recording medium 55.

  Furthermore, although the light source 61a of the irradiation device 60 has been described on the assumption that the laser light shaped as a linear light beam is oscillated, 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, there is no inconvenience even if the coherent light irradiated to the optical element 50 from the light source 61a of the irradiation device 60 is not accurately shaped. For this reason, the coherent light generated from the light source 61a may be diverging light. Further, the cross-sectional shape of the coherent light generated from the light source 61a may be an ellipse or the like instead of a circle. Furthermore, the transverse mode of the coherent light generated from the light source 61a may be a multimode.

  When the light source 61a generates a divergent light beam, the coherent light is incident not on a point but in a region having a certain area when entering the hologram recording medium 55 of the optical element 50. In this case, the light diffracted by the hologram recording medium 55 and incident on each position of the illuminated area LZ is multiplexed in angle. In other words, at each moment, coherent light is incident on each position of the illuminated area LZ from a certain angle range. 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 embodiment described above, the scanning device 65 may further include a condensing lens 67 disposed on the downstream side of the mirror device 66 along the optical path of the coherent light. In this case, as shown in FIG. 13, the light from the mirror device 66 traveling along the optical path of the light beam constituting the divergent light beam becomes light traveling in a certain direction by the condenser lens 67. 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.

  In the embodiment described above, an example in which the irradiation device 60 has only a single laser light source 61a has been shown, but the present invention is not limited to this. For example, the irradiation device 60 may include a plurality of light sources that oscillate light in the same wavelength region. In this case, the illumination device 40 can illuminate the illuminated area LZ more brightly. Further, coherent lights from different solid laser light sources do not have coherence with each other. Therefore, the multiplexing of the scattering pattern further proceeds and the speckle can be made less noticeable.

  Further, the irradiation device 60 may include a plurality of light sources that generate coherent light in different wavelength ranges. 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 reflective 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. Further, the optical element 50 may include a volume hologram that is recorded using a photosensitive medium including a silver salt material. Furthermore, the optical element 50 may include 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, scattering due to the uneven structure on the surface may become a new speckle generation factor. In this respect, the volume type hologram is preferable. In the volume hologram, since hologram interference fringes are 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, in the case of a volume hologram that is recorded using a photosensitive medium containing a silver salt material, scattering by silver salt particles may be a new speckle generation factor. 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. 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 as an optical element to illuminate. Specific examples include a total reflection type or a refractive type Fresnel lens or a fly-eye lens provided with a diffusion function. Also in such an illuminating device 40, the irradiating device 60 scans the lens array with the coherent light so as to irradiate the optical element 50 with the coherent light. By configuring the irradiation device 60 and the optical element 50 so that the traveling direction of the coherent light incident on the position is changed by the lens array to illuminate the illuminated area LZ, speckles are effectively inconspicuous. Can be made.

  Even when the lens array is used, the durability of the lens array can be reduced by the heat generated by the incident coherent light as in the case of using the hologram recording medium 55. Moreover, although it is not originally intended, the light which permeate | transmits a lens array for some reason may arise. Considering these points, when the optical element 50 has a lens array, the following configuration may be adopted. Hereinafter, a case where the lens array is used as a transmissive element will be described.

As in the modification using the transmission-type hologram recording medium 55a described with reference to FIGS. 7 to 9, in the optical element, the lens array, the adhesive layer 52, and the support base 53 are formed from the incident surface side of the coherent light. You may arrange | position in this order. Similar to FIGS. 7 and 8, the support base 53 is formed of a heat absorption layer 53a and has a frame shape having an opening. That is, the heat absorption layer 53a has an opening so that the coherent light that illuminates the illuminated region LZ is not blocked by diffraction at the lens array.
With the above configuration, the heat absorption layer 53a can effectively dissipate the heat generated in the lens array by coherent light, as in the basic mode, so that the durability of the lens array can be improved. In addition, the shape of the opening OP of the heat absorption layer 53a, the position where the heat absorption layer 53a is provided, and the like can be appropriately changed as in the modification described with reference to FIGS.

In addition, when coherent light scans a lens array configured as an assembly of unit lenses, coherent light may be incident between two adjacent unit lenses. The light incident on this position cannot change the direction of travel to the originally intended direction, and whether the lens array is intended to change the direction of travel of light by refraction or reflection. Therefore, a lot of light (straightly transmitted light) that is transmitted in a substantially straight direction comes to exist. From this point, when the optical element 50 having a lens array is used, the coherent light from the irradiation device 60 passes through the position of the optical element 50 when it is assumed that the traveling direction is not changed by the optical element 50. It is preferable that the postulated optical path of the coherent light (straight forward transmitted light) is deviated from the illuminated region LZ. According to such an optical path design, the light whose traveling direction cannot be changed as planned by the optical element 50 for some reason including damage or dropping of the optical element 50 enters the illuminated area LZ. Can be effectively prevented.
A reflective layer may be provided on the back surface of the lens array, and the lens array may be used as a reflective element. Also in this case, the durability of the lens array can be improved by providing the heat absorption layer 53a as in the basic mode.

(Lighting method)
In the embodiment described above, the irradiation device 60 is configured to be able to scan the coherent light in the one-dimensional direction on the optical element 50, and the hologram recording medium 55 (or lens array) of the optical element 50 is irradiated to each position. An example is shown in which the coherent light is configured to diffuse (spread and diverge) in a two-dimensional direction, whereby the illumination device 40 illuminates the two-dimensional illuminated area LZ. However, as described above, the present invention is not limited to such an example. For example, the irradiation device 60 is configured to be able to scan the coherent light on the optical element 50 in a two-dimensional direction, and The hologram recording medium 55 (or lens array) of the optical element 50 is configured to diffuse (spread and diverge) the coherent light irradiated to each position in a two-dimensional direction. May illuminate the two-dimensional illuminated area LZ (the aspect already described with reference to FIG. 12).

  Further, as already mentioned, the irradiation device 60 is configured to be able to scan the coherent light on the optical element 50 in a one-dimensional direction, and the hologram recording medium 55 (or lens array) of the optical element 50 is used. Is configured to diffuse (spread and diverge) the coherent light irradiated to each position in a one-dimensional direction, so that the illumination device 40 illuminates the one-dimensional illuminated region LZ. It may be. In this aspect, the scanning direction of the coherent light by the irradiation device 60 and the diffusion direction (expansion direction) of the hologram recording medium 55 (or lens array) of the optical element may be parallel to each other.

  Further, the irradiation device 60 is configured to be able to scan the coherent light on the optical element 50 in a one-dimensional direction or a two-dimensional direction, and the hologram recording medium 55 (or lens array) of the optical element 50 is placed at each position. The irradiated coherent light may be configured to diffuse (spread and diverge) in a one-dimensional direction. In this aspect, as already described, the optical element 50 has a plurality of hologram recording media 55 (or lens arrays), and sequentially illuminates the illuminated area LZ corresponding to each hologram recording medium 55 (or lens array). By doing so, the illumination device 40 may illuminate a two-dimensional area. 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.

(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 image display device 15 Screen 20 Projection device 25 Projection optical system 30 Spatial light modulator 40 Illumination device 41 Beam stopper 42 Beam stopper 43 Beam stopper 50, 50a Optical element 51 Protective layer 52 Adhesive layer 53 Support Base material 53a Heat absorption layer 53b Light absorption layer 55, 55a Hologram recording medium 58 Hologram photosensitive material 60 Irradiation device 61a Light source 65 Scan device 66 Mirror device (reflection device)
66a Mirror (reflective surface)
67 Condensing lens LZ Illuminated area

Claims (14)

An optical element in which each point can diffuse coherent light over at least the entire illuminated area;
An irradiation device for irradiating the optical element with the coherent light so that the coherent light scans the surface of the optical element;
The optical element has a support substrate;
The said support base material is an illuminating device which has a heat absorption layer which absorbs the heat | fever of the said optical element. The optical element includes a hologram recording medium capable of reproducing an image of a scattering plate,
The irradiation device irradiates the optical element with the coherent light so that the coherent light scans on the hologram recording medium,
The irradiation device and the optical element are arranged so that the coherent light incident on each position of the hologram recording medium from the irradiation device reproduces an image superimposed on the illuminated area, respectively.
The support substrate supports the hologram recording medium;
The illumination device according to claim 1, wherein the heat absorption layer absorbs heat of the hologram recording medium. The hologram recording medium is a reflection type hologram recording medium,
The illumination device according to claim 2, wherein the support base material is provided on a rear surface side of the incident surface of the hologram recording medium and further includes a light absorption layer.   The lighting device according to claim 3, wherein the light absorption layer and the heat absorption layer of the support base are arranged in this order from the incident surface side of the coherent light. The hologram recording medium is a reflection type hologram recording medium,
The support base is provided on the back side of the incident surface of the hologram recording medium,
The lighting device according to claim 2, wherein the heat absorption layer further has a light absorption function. The hologram recording medium is a transmission type hologram recording medium,
The lighting device according to claim 2, wherein the support base has a frame shape having an opening.   The irradiation apparatus includes a light source that generates the coherent light, and a scanning device that changes a traveling direction of the coherent light from the light source so that the coherent light scans on the hologram recording medium. The illumination device according to any one of claims 2 to 6. The optical element includes a lens array that changes a traveling direction of incident light,
The irradiation device irradiates the optical element with the coherent light so that the coherent light scans on the lens array,
The irradiation apparatus and the optical element are arranged so that the coherent light incident on each position of the optical element from the irradiation apparatus is changed in the traveling direction by the lens array to illuminate at least the entire illuminated area. Have been
The support substrate supports the lens array;
The lighting device according to claim 1, wherein the heat absorption layer absorbs heat of the lens array.   The lighting device according to claim 8, wherein the support base has a frame shape having an opening.   The irradiation apparatus includes: a light source that generates the coherent light; and a scanning device that changes a traveling direction of the coherent light from the light source so that the coherent light scans the lens array. The lighting device according to claim 8 or 9. The lighting device according to any one of claims 1 to 10,
A projection apparatus comprising: a spatial light modulator disposed at a position overlapping the illuminated area and illuminated by 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 arranged at a position overlapping the illuminated area.

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