JP6146626B2 - Optical element, illumination device, projection device, and projection-type image display device - Google Patents

Description

  The present invention relates to an optical element that diffracts light, and more particularly, to an optical element that can suppress an increase in temperature of the optical element due to incident light. The present invention also relates to an illumination device, a projection device, and a projection-type image display device that include an optical element and an irradiation device that irradiates light to the optical element.

  Various types of projection-type image display devices that display images by projecting light onto a screen have been proposed, including commercially available products called “optical projectors”. The basic principle of such a projection-type image display device is to use a spatial light modulator such as a liquid crystal micro display or DMD (Digital Micromirror Device) to generate an original two-dimensional image. A two-dimensional image is enlarged and projected on a screen using a projection optical system. For example, an optical projector is known in which a white light source such as a high-pressure mercury lamp is used to illuminate a spatial light modulator such as a liquid crystal display, and an obtained modulated image is enlarged and projected onto a screen by a lens.

  By the way, in a spatial light modulator such as a DMD, not all light is used, and a part of the light is absorbed as heat by the spatial light modulator and the optical element. Such heat generation becomes more prominent when light having a high luminous flux density is used.

  Various methods have been proposed to prevent deterioration of the characteristics and reliability of the spatial light modulator even when heat is generated due to light absorption. For example, in Patent Document 1, a spatial light modulator such as a DMD is provided on a surface opposite to a surface on which light is incident, and a heat receiving unit that absorbs heat generated in the spatial light modulator, and a cooling unit that cools the heat receiving unit And a metal fitting for holding the spatial light modulator, a heat conductive sheet attached to the spatial light modulator and the metal fitting, and a heat diffusing plate and a cooling unit for releasing the heat of the heat conductive sheet. Cooling devices have been proposed.

  By the way, a high-intensity discharge lamp such as a high-pressure mercury lamp has a relatively short life, and when used in an optical projector or the like, it is necessary to frequently replace the lamp. 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 light source 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 coherent light such as laser light. When speckle is generated on a screen, it is observed as a spotted brightness unevenness and observed. 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, the document “Speckle Phenomena in Optics, Joseph W. Goodman, Roberts & Co., 2006” provides a detailed theoretical discussion of speckle generation.

  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, Patent Literature 2 discloses an illumination device that illuminates a spatial light modulator and includes a hologram recording medium and an irradiation device that irradiates the hologram recording medium with coherent light so as to scan the hologram recording medium. A device has been proposed. In Patent Document 2, by illuminating the spatial light modulator using such an illuminating device, the incident angle of diffracted light that reaches each point on the spatial light modulator from the hologram recording medium is changed with time. be able to. As a result, speckle can be reduced.

  The recording layer on which the interference fringes of the hologram recording medium are recorded is generally formed by applying a photosensitive composition on a support such as glass. On the recording layer, as described in Patent Document 3, glass or a film is provided as a protective member.

JP 2011-170013 A Japanese Patent No. 4816819 JP-A-6-301322

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

  Members such as glass for supporting the hologram recording medium and glass or film for protecting the hologram recording medium are usually not members having high heat dissipation characteristics. Therefore, when the hologram recording medium is irradiated with light having a high luminous flux density, the temperature of the irradiated area becomes high, and as a result, the light diffraction characteristics of the hologram recording medium are affected. Can be considered.

  An object of this invention is to provide the optical element, the illuminating device, projection apparatus, and projection type video display apparatus which can solve such a subject effectively.

The optical element for diffracting coherent light according to the present invention is:
Comprising a transparent substrate, a hologram recording medium, an adhesive layer and a heat conductive member laminated in order from the side on which the coherent light is incident;
The hologram recording medium is configured to diffract coherent light that is transmitted through the transparent substrate and incident on the hologram recording medium;
The adhesive layer has a plurality of thermally conductive additives and a binder that fills between each thermally conductive additive,
The thermal conductivity of the thermal conductive member and the thermal conductivity of the thermal conductive additive are larger than the thermal conductivity of the transparent substrate.

  In the optical element according to the present invention, the thermally conductive additive of the adhesive layer may have an elongated shape extending along the normal direction of the transparent substrate. In this case, the dimension of the heat conductive additive of the adhesive layer in the normal direction of the transparent substrate may be substantially the same as the film thickness of the adhesive layer.

  In the optical element according to the present invention, the thermally conductive additive of the adhesive layer may include at least one of carbon particles, metal particles, carbon fibers, or metal fibers.

  In the optical element according to the present invention, the thermally conductive member may have a thermally conductive layer containing metal or carbon.

  In the optical element according to the present invention, the thermally conductive member may have a first thermally conductive layer and a second thermally conductive layer arranged in order from the adhesive layer side. In this case, the thermal conductivity of the second thermal conductive layer may be larger than the thermal conductivity of the first thermal conductive layer. In addition, at least one of the first heat conductive layer and the second heat conductive layer may contain a metal or carbon.

  In the optical element according to the present invention, the thermally conductive member may have a reflection suppressing portion and a thermally conductive portion in order from the adhesive layer side. In this case, the reflection suppressing portion constitutes the surface closest to the adhesive layer of the thermally conductive member, and suppresses reflection of coherent light incident from the adhesive layer side.

  In the optical element according to the present invention, the reflection suppressing portion may include a plurality of protrusions having a shape in which a cross-sectional area becomes smaller toward the adhesive layer side.

  In the optical element according to the present invention, the reflection suppressing portion may include a dielectric multilayer film including a plurality of layers having different refractive indexes.

The lighting device according to the present invention comprises:
An optical element according to the invention as described above;
An irradiation device for irradiating the optical element with coherent light so that the coherent light scans the hologram recording medium of the optical element;
A region on the hologram recording medium of the optical element that is irradiated with coherent light by the irradiation device at an arbitrary moment is a part of the hologram recording medium.

  In the illuminating device according to the present invention, the coherent light incident on each position of the holographic recording medium of the optical element from the irradiating device is diffracted by the holographic recording medium so as to illuminate at least a part of the overlapping area. Further, the irradiation device and the optical element may be arranged.

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

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

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

  According to the present invention, heat generated in the hologram recording medium can be appropriately released.

FIG. 1 is a diagram for explaining an embodiment according to the present invention, and is a diagram showing a schematic configuration of an optical element, an illumination device, a projection device, and a projection type video display device as one embodiment. 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 cross-sectional view showing the optical element shown in FIG. FIG. 7 is a cross-sectional view for explaining a modification of the adhesive layer of the optical element. FIG. 8 is a cross-sectional view for explaining a modification of the adhesive layer of the optical element. FIG. 9 is a cross-sectional view for explaining a modification of the heat conductive member of the optical element. FIG. 10 is a cross-sectional view for explaining a modification of the thermally conductive member of the optical element. FIG. 11 is an enlarged cross-sectional view showing a reflection suppressing portion of the heat conductive member shown in FIG. 12A and 12B are cross-sectional views for explaining a modification of the reflection suppressing portion of the optical element. FIG. 13 is a cross-sectional view for explaining a modification of the reflection suppressing portion of the optical element. FIG. 14 is a view for explaining a modification of the optical element, and is a plan view showing the optical element together with a corresponding illuminated region. FIG. 15 is a diagram for explaining an application form to which the basic form of one embodiment according to the present invention is applied, and is a lighting device, a projection apparatus, and a projection type video display apparatus as specific examples of the application form. It is a figure which shows schematic structure of these. FIG. 16 is a diagram showing the results of thermography observation of the optical element according to Example 1. FIG. 17 is a diagram showing a thermographic observation result of the optical element according to Comparative Example 1.

  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.

  1 to 15 are diagrams for explaining an optical element, an illumination device, a projection device, a projection-type image display device, and a modification thereof according to an embodiment of the present invention. Among these, with reference to FIGS. 1-6, the optical element which concerns on one Embodiment, an illuminating device, a projection apparatus, and a projection type video display apparatus are demonstrated. Thereafter, an example of a modification to the optical element, the illumination device, the projection device, and the projection type video display device according to the embodiment will be described with reference to FIGS. 7 to 15 as appropriate.

〔Constitution〕
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.

  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. When the screen 15 is configured as a reflective screen, the observer observes an image displayed by the 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 transmission screen, the observer observes the image displayed by the 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 illuminating device 40 shown in FIGS. 1 and 2 diffracts incident coherent light to direct the traveling direction of the coherent light toward the illuminated region LZ, and an irradiating device that irradiates the optical element 50 with the coherent light. 60. In the following description of the optical element 50 and each component of the optical element 50, “one side” means a side on which coherent light from the irradiation device 60 is incident, and “other side” means one side. Means the other side. In FIG. 1, the surface on one side of the optical element 50 is indicated by reference numeral 50a, and the surface on the other side of the optical element 50 is indicated by reference numeral 50b.

  The optical element 50 includes a hologram recording medium 55 that functions as a light diffusing element or a light diffusing element, in particular, 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 transparent substrate 51, a hologram recording medium 55, an adhesive layer 56, and a heat conductive member 52 that are stacked in order from the side on which coherent light enters, that is, one side. The transparent substrate 51 is made of a material having sufficient translucency. Therefore, most of the light incident on the optical element 50 from one side passes through the transparent substrate 51 and reaches the hologram recording medium 55. The “hologram recording medium” is a medium on which a hologram is recorded.

  The hologram recording medium 55 of the optical element 50 receives the coherent light irradiated from the irradiation device 60 and transmitted through the transparent substrate 51 and incident on the hologram recording medium 55 as the reproduction illumination light La, and diffracts the coherent light with high efficiency. can do. 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 an arbitrary moment is a part of the entire surface of the hologram recording medium 55, and in particular, in the illustrated example, is called a point. It is a very small area.

  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. The coherent light incident on each position of the hologram recording medium 55 from the irradiation device 60 is diffracted by the hologram recording medium 55 and illuminates areas that overlap each other at least partially. In particular, in the embodiment described here, the coherent light incident on each position of the hologram recording medium 55 from the irradiation device 60 is diffracted by the hologram recording medium 55 to illuminate the same illuminated region LZ. . More specifically, 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. It has become. 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 same illuminated area LZ. 2 and FIGS. 4 and 5 to be described later, in order to clarify the function of the hologram recording medium 55, the components other than the hologram recording medium 55 among the components of the optical element 50 are described. Omitted.

  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 reference light Lr is incident on each position of the hologram photosensitive material 58 with a substantially uniform light amount from the entire area of the exit surface 6 a of the scattering plate 6. It becomes easy. In such a case, the light incident on each position of the obtained hologram recording medium 55 reproduces the image 5 of the scattering plate 6 with the same brightness, and the reproduced scattering plate 6 It can be realized that the image 5 is observed with substantially uniform brightness.

  As described above, when the hologram recording material 58 is exposed to the reference light Lr and the object light Lo, an interference fringe formed by the interference of the reference light Lr and the object light Lo is generated. In the case of a pattern and a volume hologram, for example, it is recorded on the hologram recording material 58 as a refractive index modulation pattern. Thereafter, appropriate post-processing corresponding to the type of the hologram photosensitive material 58 is performed, and the hologram recording medium 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 with respect 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 scattered light Lo emitted from each position on the exit surface 6 a of the scattering plate 6 in the exposure process is incident on almost the entire region of the hologram photosensitive material 58. 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 apparatus 60 includes a laser light source 61a that generates coherent light in a specific wavelength region, and a scanning device 65 that changes the optical path of the coherent light from the laser light source 61a. doing. The scanning device 65 changes the optical path of the coherent light with time, and changes the incident position of the coherent light on the optical element 50. 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 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 optical path of the 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.

  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 coherent light that illuminates the illuminated area LZ. The illumination directions are different from each other. Since the position on the hologram recording medium 55 on which the coherent light is incident changes with time, the incident direction of the coherent light to the illuminated region LZ also changes with time, as indicated by an arrow A1 in FIG. 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. For this reason, the coherent light scattering pattern having no correlation 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.

  By the way, the wavelength of the coherent light incident on the hologram recording medium 55 of the optical element 50 does not need to exactly match the wavelength of the light used in the exposure process (recording process) in FIG. Even if it is slightly deviated from the wavelength, the image 5 can be substantially reproduced in the illuminated area LZ. In the first place, as a practical problem, there is a case where the hologram photosensitive material 58 contracts when the hologram recording medium 55 is produced. In such a case, the hologram recording material 58 is considered in consideration of the contraction of the hologram photosensitive material 58. When the medium 55 is manufactured, it is preferable that the incident angle of the coherent light is adjusted. From this point, 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 (recording process) in FIG. .

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

  As described above, in the present embodiment, the region (position) on the hologram recording medium 55 that is irradiated with the coherent light by the irradiation device 60 at an arbitrary moment is a part of the hologram recording medium 55. . Further, as described above, the image 5 of the scattering plate 6 having the same contour is reproduced at the same position (illuminated region LZ) by the coherent light incident on each position on the hologram recording medium 55 at each moment. . Accordingly, in the present embodiment, on average, the energy of light necessary for reproducing the entire image 5 of the scattering plate 6 at each moment is incident on each position on the hologram recording medium 55 at each moment. It is obtained by the energy of the coherent light.

  Most of the coherent light incident on the hologram recording medium 55 is diffracted, and the other part is transmitted through the hologram recording medium 55 or absorbed as heat by the hologram recording medium 55. Here, when the luminous flux density of the coherent light irradiated to the hologram recording medium 55 is high, the energy of the coherent light absorbed as heat in each region of the hologram recording medium 55 also increases. Here, in the present embodiment, the temperature increase of the hologram recording medium 55 can be suppressed by disposing the heat conductive member 52 on the other side of the hologram recording medium 55 via the adhesive layer 56. Hereinafter, the structure of the optical element 50 including the adhesive layer 56 and the heat conductive member 52 will be described in detail with reference to FIG.

  FIG. 6 is a cross-sectional view showing the optical element 50 including the adhesive layer 56 and the heat conductive member 52. As described in Patent Document 3 above, in a general optical element having a hologram recording medium, a support such as glass or a protective member made of glass or a film is disposed on both sides of the hologram recording medium. Has been. On the other hand, in the present embodiment, as shown in FIG. 6, an adhesive layer 56 is interposed on the other side of the hologram recording medium 55, that is, on the opposite side of the hologram recording medium 55 from the side facing the transparent substrate 51. The heat conductive member 52 is disposed. This thermal conductive member 52 is configured such that its thermal conductivity is larger than that of the transparent substrate 51. By providing such a heat conductive member 52, heat generated in the hologram recording medium 55 can be appropriately released to the outside, and thereby the temperature of the hologram recording medium 55 rises due to heat generated by incident light. Can be suppressed. Note that “the thermal conductivity of the thermal conductive member 52 is larger than the thermal conductivity of the transparent substrate 51” means that the thermal conductive member 52 is disposed on the other side of the hologram recording medium 55 as in the present embodiment, for example. The hologram recording medium 55 when the temperature of the hologram recording medium 55 is assumed to be the same member as that of the transparent substrate 51 disposed on the other side of the hologram recording medium 55 instead of the heat conductive member 52 for comparison. It means that it is lower than the temperature of. Further, when it is possible to calculate the thermal conductivity of the thermal conductive member 52 as a whole based on the thermal conductivity of each component constituting the thermal conductive member 52, the calculated thermal conductivity and the transparent substrate The thermal conductivity of 51 may be compared.

  As shown in FIG. 6, the heat conductive member 52 includes a first heat conductive layer 54 a disposed on the adhesive layer 56 side, that is, on the opposite side of the adhesive layer 56 from the side facing the hologram recording medium 55. It is out. The first thermal conductive layer 54 a is made of a material having a higher thermal conductivity than glass or the like constituting the transparent substrate 51. For example, at least one of the first thermal conductive layer 54a and the second thermal conductive layer 54b includes any one of silicon, a metal such as iron or copper, or carbon. The thickness and thermal conductivity of the first thermal conductive layer 54 a are appropriately set according to heat generation assumed in the hologram recording medium 55, heat resistance characteristics of the hologram recording medium 55, and the like.

  Next, the adhesive layer 56 interposed between the hologram recording medium 55 and the heat conductive member 52 will be described. As shown in FIG. 6, the adhesive layer 56 has a plurality of thermally conductive additives 56a and a binder 56b that fills between the thermally conductive additives 56a. FIG. 6 shows an example in which each thermally conductive additive 56a is configured as particles.

  Each thermal conductive additive 56a of the adhesive layer 56 is made of a material having higher thermal conductivity than the glass constituting the transparent substrate 51, like the first thermal conductive layer 54a. For example, each thermally conductive additive 56a is configured as particles having high thermal conductivity such as carbon particles and metal particles. For this reason, compared with the case where only a general adhesive is interposed between the hologram recording medium 55 and the heat conductive member 52, the heat generated in the hologram recording medium 55 is more efficiently generated. Can be conducted. Thereby, the temperature rise of the hologram recording medium 55 can be further suppressed. The material used as the binder 56b of the adhesive layer 56 is not particularly limited as long as the space between the respective heat conductive additives 56a can be appropriately filled, and a general adhesive or the like is used as the binder 56b. .

  The film thickness of the adhesive layer 56 is not particularly limited as long as the hologram recording medium 55 and the heat conductive member 52 can be appropriately bonded, but is, for example, in the range of 1 μm to 100 μm.

  According to the embodiment 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 area LZ in the illumination device 40 is preferably sufficiently bright, coherent light having a high light flux density is used. As a result, the amount of heat generated by the hologram recording medium 55 increases. Here, according to the present embodiment, the heat conductive member 52 is provided on the other surface of the hologram recording medium 55, that is, the back surface side of the incident surface. For this reason, the heat generated in the hologram recording medium 55 can be appropriately released to the outside. Further, the hologram recording medium 55 and the heat conductive member 52 are bonded by an adhesive layer 56 having a plurality of heat conductive additives 56a. For this reason, the heat generated in the hologram recording medium 55 can be more efficiently conducted to the heat conductive member 52. By these things, the temperature rise of the hologram recording medium 55 can fully be suppressed.

  On the other hand, when the heat conductive member 52 and the adhesive layer 56 are not provided, the following problems 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 the present embodiment, these problems can be effectively prevented, and the durability of the hologram recording medium 55 can be improved.

  Accordingly, the illumination device 40, the projection device 20, and the projection type image display device 10 also include the optical element 50 having the heat conductive member 52 provided through the adhesive layer 56 described above. It is possible to prevent deterioration of brightness and accuracy and improve durability of each device.

[Modification]
Various modifications can be made to the present embodiment described based on one 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 portions in the above-described embodiment are used, and redundant descriptions are omitted.

(Adhesive layer of optical element)
In the present embodiment described above, the example in which each heat conductive additive 56a of the adhesive layer 56 is made of particles having no particular direction has been shown. However, the present invention is not limited to this, and as shown in FIG. 7, each thermally conductive additive 56 a may have an elongated shape extending along the normal direction of the transparent substrate 51. Here, “extends along the normal direction” means that each of the thermal conductive additives 56 a in the direction normal to the transparent substrate 51 is in the direction perpendicular to the normal direction of the transparent substrate 51. It means that it is larger than the dimension of the object 56a. By configuring each thermally conductive additive 56a in this manner, the heat generated in the hologram recording medium 55 can be more efficiently conducted to the thermally conductive portion 54.

  As shown in FIG. 7, the dimension of each thermally conductive additive 56 a in the normal direction of the transparent substrate 51 may be substantially the same as the film thickness of the adhesive layer 56. That is, each heat conductive additive 56 a may be in contact with the hologram recording medium 55 and the heat conductive member 52. Thereby, the heat generated in the hologram recording medium 55 can be more efficiently conducted to the heat conductive portion 54. Note that “substantially the same” means that the dimension of each thermally conductive additive 56a in the normal direction of the transparent substrate 51 is the thickness of the binder 56b unless an excessive pressure is applied to the hologram recording medium 55 or the thermally conductive member 52. It means that it may be larger.

  Moreover, in this Embodiment mentioned above, the example in which each heat conductive additive 56a is comprised as particle | grains was shown. However, the present invention is not limited to this, and as shown in FIG. 8, each thermally conductive additive 56 a may be configured as a fibrous substance. Examples of such a heat conductive additive 56a include carbon fiber and metal fiber. Also in the example shown in FIG. 8, each heat conductive additive 56 a preferably has an elongated shape extending along the normal direction of the transparent substrate 51. Further, the dimension of each thermally conductive additive 56 a in the normal direction of the transparent substrate 51 is substantially the same as the film thickness of the adhesive layer 56. Thereby, the heat generated in the hologram recording medium 55 can be more efficiently conducted to the heat conductive portion 54.

(Thermal conductive member of optical element)
Moreover, in this Embodiment mentioned above, the heat conductive member 52 showed the example containing the 1st heat conductive layer 54a and the 2nd heat conductive layer 54b. However, the present invention is not limited to this, and although not illustrated, the heat conductive member 52 may include more heat conductive layers. Moreover, as shown in FIG. 9, the heat conductive part 54 may be comprised only from the 1st heat conductive layer 54a. In this case, the first thermal conductive layer 54a may include any one of silicon, a metal such as iron or copper, or carbon.

(Reflection suppression part of thermal conductive member)
As shown in FIG. 10, the heat conductive member 52 constitutes the most side of the heat conductive member 52, that is, the surface on the adhesive layer 56 side, and reflects the coherent light incident from the adhesive layer 56 side. It may have a reflection suppressing portion 53 that suppresses. In this case, the first thermal conductive layer 54a and the second thermal conductive layer 54b described above are arranged on the other side of the reflection suppressing portion 53, that is, on the side opposite to the side facing the adhesive layer 56 side of the reflection suppressing portion 53. And function as a thermally conductive portion 54 having a high thermal conductivity. In this case, the heat conductive member 52 has a function of suppressing the coherent light that passes through the hologram recording medium 55 and reaches the heat conductive member 52 from being reflected by the heat conductive member 52, and the hologram recording medium 55. It has both the function of releasing heat. Accordingly, an increase in the temperature of the hologram recording medium 55 can be suppressed while suppressing unnecessary reflections from increasing due to the provision of the heat conductive member 52.

  As shown in FIG. 10, the reflection suppressing portion 53 includes a plurality of minute protrusions 53 a having a shape in which a cross-sectional area becomes smaller toward one side, that is, the adhesive layer 56 side. Therefore, a plurality of minute concavo-convex structures are formed on one surface of the heat conductive member 52.

  FIG. 11 is an enlarged cross-sectional view of the reflection suppressing portion 53 including a plurality of protrusions 53a. In FIG. 11, the pitch between the protrusions 53 a is indicated by a symbol p, the width of one end of each protrusion 53 a is indicated by a symbol w, and the height of each protrusion 53 a is indicated by a symbol d. ing. 10 and 11, the height of the protrusion 53a is synonymous with the depth of the concave portion of the concavo-convex structure formed on one surface of the heat conductive member 52. The pitch p is smaller than the wavelength of the coherent light used, and is preferably half or less of the wavelength of the coherent light used. In this case, the concavo-convex structure constituted by the plurality of protrusions 53a causes a continuous change in refractive index along the protrusion direction of each protrusion 53a at the interface between the adhesive layer 56 and the heat conductive member 52. That is, the change in the refractive index at the interface between the adhesive layer 56 and the heat conductive member 52 is moderate for the coherent light incident on the heat conductive member 52.

  In general, reflection of light at a material interface occurs due to a discontinuous and rapid change in refractive index at the material interface. Here, according to the present embodiment, by providing the plurality of protrusions 53a, the change in the refractive index at the interface can be moderated, thereby suppressing the reflection of light at the interface. . As a result, it is possible to prevent the light transmitted through the hologram recording medium 55 from being reflected from the heat conductive member 52 and emitted from one side of the optical element 50. Such a reflection suppressing structure is known as a moth-eye type reflection suppressing structure, and further description thereof is omitted here. For further details of the moth-eye type reflection suppressing structure, refer to documents such as Japanese Patent Laid-Open No. 50-70040 and Japanese Patent No. 4197100.

  Preferably, the pitch p of each protrusion 53a is 200 nm or less. Thereby, the wavelength dependency of the light reflectance in the reflection suppressing portion 53 can be reduced. The height d of each protrusion 53a, that is, the depth of the concave portion of the concavo-convex structure is appropriately set according to the required reflectance, and is in the range of 150 nm to 450 nm, for example. In general, the greater the depth of the concave portion, the smaller the reflectance in the heat conductive member 52 can be made. Further, the width w of the tip portion of each protrusion 53a is also appropriately set according to the required reflectance, and is in the range of 0 nm to 30 nm, for example. In general, the smaller the width w, the lower the reflectance in the entire visible light wavelength range. The form in which the width w is 0 nm is not the form shown in FIG. 11 in which each protrusion 53a has a truncated cone or polygonal truncated pyramid shape, but the form in which each protrusion 53a has a truncated cone or polygonal pyramid shape. Means that will be adopted.

  Moreover, the shape of each projection part 53a is not restricted to the shape of the above-mentioned truncated cone, polygonal frustum, cone, or polygonal pyramid, and the projection part 53a of various shapes can be employ | adopted. For example, as shown to Fig.12 (a), each projection part 53a may have a hemispherical shape. Further, as shown in FIG. 12B, a shape in which an inflection point appears in the contour of the cross section of the protrusion 53a as it goes to one side may be employed. In any example, each protrusion 53a is configured to have a cross-sectional area that decreases toward one side, thereby suppressing light reflection at the interface. In particular, according to the embodiment shown in FIG. 12B, the change in the cross-sectional area of each protrusion 53a can be made substantially proportional to the position of the protrusion 53a in the protruding direction. Thereby, reflection of light at the interface can be further suppressed, and ideally reflection can be made zero.

  Further, in each modification shown in FIGS. 10 to 12 (a) and 12 (b), an example is shown in which the reflection suppressing portion 53 includes a plurality of minute protrusions 53a having a shape in which the cross-sectional area decreases toward one side. It was. However, the structure employed in the reflection suppressing portion 53 in order to suppress reflection is not limited to this. For example, as shown in FIG. 13, the reflection suppressing portion 53 may include a dielectric multilayer film 53b including a plurality of layers having different refractive indexes. In this case, by appropriately setting the thickness and refractive index of each layer constituting the dielectric multilayer film 53b, it is possible to cancel the reflected lights from the respective layers, thereby reflecting the light in the heat conductive member 52. Can be suppressed. When the reflection suppressing portion 53 is configured by the dielectric multilayer film 53b, the reflection suppressing portion 53 is disposed on the other side of the hologram recording medium 55 without causing an air gap even if the adhesive layer 56 is not provided. It becomes easy to make.

(Optical element hologram recording medium)
Furthermore, as shown in FIG. 14, 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. 14 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. 14, 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. Also in this modification, the hologram recording media 55-1, 55-2,... Are provided on the other side of the hologram recording media 55-1, 55-2,. The heat generated at 2,... Can be appropriately released to the outside.

(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 having the 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 projection type image display apparatus 10 in the above-described embodiment, and the screen 15 is positioned so as to overlap the illuminated area LZ. By disposing, it is possible to display some pattern recorded on the hologram recording medium 55 on the screen 15. 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. .

(Optical element hologram recording medium)
In the embodiment described above, the reflection type hologram recording medium 55 of the optical element 50 is composed of the volume hologram 55 using a photopolymer. However, the present invention is not limited to this. 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 the hologram interference fringe is recorded as a refractive index modulation pattern (refractive index distribution) inside the medium, it is not affected by scattering due to the uneven structure on the surface.

  However, 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. However, when a Fourier transform type hologram recording medium is used, a lens may also be used during image reproduction.

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

(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.

<Application form>
[Configuration of application form and operation of application form]
Next, an application form obtained by applying the basic form described above will be described with reference to the illumination device 40, the projection device 20, and the projection type video display device 10 illustrated in FIG. In the following description, only points that are added to the basic form described above will be described, and other parts that may be configured in the same manner as the basic form described above are denoted by the same reference numerals as in the basic form described above in FIG. The duplicated explanation is omitted.

  In the basic mode described above, the irradiation apparatus 60 has an example having only a single light source 61a that generates coherent light. The coherent light generated from the single light source 61a is typically light in a narrow wavelength band and is monochromatic light, as represented by laser light. Further, coherent light generated from a substantially usable light source, that is, a light source which can be obtained at a low cost and has a sufficient output is limited to light of a specific wavelength (range). That is, light of various colors cannot be displayed with light from a single light source. On the other hand, in many cases today, it is desirable to illuminate the illuminated area or display an image in a desired color that cannot be displayed with a single light source, or in multiple colors, typically full color. It is rare. The form shown in FIG. 15 is an application of the basic form described above in consideration of such points.

  In the applied form, the irradiation device 60 irradiates the optical element 50 with the synthesized light SL formed by synthesizing a plurality of coherent lights having different wavelength ranges. In the example shown in FIG. 15, the irradiation device 60 includes the first coherent light La in the first wavelength region, the second coherent light Lb in the second wavelength region different from the first wavelength region, the first wavelength region, The synthetic light SL formed by synthesizing the third coherent light Lc in the third wavelength range different from both of the second wavelength ranges is irradiated. In particular, in the following, the first wavelength region corresponds to the first primary color component (for example, red component), the second wavelength region corresponds to the second primary color component (for example, green component), and the third wavelength. An example in which the irradiating device 60 emits white light by additive color mixing of the first to third primary color components corresponding to the third primary color component (for example, blue component) will be described.

  In the example illustrated in FIG. 15, the irradiation apparatus 60 includes the scanning device 65 described above and a light source mechanism 61 that generates the combined light SL. The light source mechanism 61 includes a plurality of light sources 61a, 61b, and 61c that respectively oscillate coherent light in a wavelength region corresponding to the wavelength region of each coherent light, and a combining device that combines the coherent light from the plurality of light sources 61a, 61b, and 61c. 62. The light source mechanism 61 includes, as a plurality of light sources, a first light source 61a that oscillates the first coherent light La in the first wavelength region, a second light source 61b that oscillates the second coherent light Lb in the second wavelength region, And a third light source 61c that oscillates the third coherent light Lc in the three wavelength regions. On the other hand, as the synthesizing device 62, various members, components, apparatuses, and the like that synthesize two lights can be used. In the illustrated example, a half mirror having an advantage of being inexpensive and small compared with a cross dichroic prism or the like is used as the combining device 62.

  In the example shown in FIG. 15, the optical element 50 includes a hologram recording medium 55 made of a reflective volume hologram that diffracts the combined light and illuminates the illuminated area LZ. However, the reflective volume hologram has a strong wavelength selectivity. For this reason, the hologram recording medium 55 of the illustrated optical element 50 includes first to third hologram elements 55a, 55b, and 55c provided corresponding to coherent light in each wavelength region. The first hologram element 55a is provided corresponding to the first coherent light La in the first wavelength range, the second hologram element 55b is provided corresponding to the second coherent light Lb in the second wavelength range, and the third The hologram element 55c is provided corresponding to the third coherent light Lc in the third wavelength region.

  Each of the first to third hologram elements 55a, 55b, and 55c can reproduce the image 5 of the scattering plate 6. In particular, the first hologram element 55a diffracts the first coherent light La in the first wavelength region as the reproduction illumination light, and the second hologram element 55b diffracts the second coherent light Lb in the second wavelength region as the reproduction illumination light. As a result, the third hologram element 55c diffracts the third coherent light Lc in the third wavelength region as the reproduction illumination light, so that the images 5 of the same scattering plate 6 can be reproduced. .

  Note that the hologram elements 55a, 55b, and 55c for coherent light in each wavelength region are used as exposure light (reference light Lr and object light Lo) in the method already described with reference to FIGS. 3 and 4, for example. , By using coherent light in the corresponding wavelength range.

  As shown in FIG. 15, the first to third hologram elements 55a, 55b, and 55c of the hologram recording medium 55 are stacked on each other. Similarly to the basic form described above, when the irradiation device 60 irradiates the optical element 50 with the synthesized light SL, the synthesized light SL scans on the hologram recording medium 55. As a result, at least the first coherent light La of the combined light SL scans on the first hologram element 55a, and at least the second coherent light Lb of the combined light SL scans on the second hologram element 55b to combine the light. At least the third coherent light Lc of the light SL scans on the third hologram element 55c. Then, the first coherent light La of the combined light SL incident on each position of the hologram recording medium 55 from the irradiation device 60 reproduces the image 5 so as to overlap the illuminated region LZ, and from the irradiation device 60 to the hologram recording medium 55. The second coherent light Lb of the combined light SL incident on each of the positions of the combined light reproduces the image 5 superimposed on the illuminated region LZ, and is incident on each position of the hologram recording medium 55 from the irradiation device 60 The optical element 50 and the irradiation device 60 are positioned so that the third coherent light Lc of the light SL is superimposed on the illuminated area LZ to reproduce the image 5.

  In the application mode shown in FIG. 15, when the combined light SL from the irradiation device 60 enters the optical element 50, coherent light (first to third coherent light) La, Lb, and Lc in each wavelength region that forms the combined light. Thus, the image 5 of the scattering plate 6 is reproduced so as to overlap the illuminated area LZ. As a result, the illuminated area LZ is illuminated with a color obtained by additive color mixing of the first to third coherent lights La, Lb, and Lc. That is, in this example, the illumination device 60 illuminates the illuminated area LZ with white light.

  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 of the coherent lights La, Lb, and Lc in each wavelength region. In this case, it is possible to display a video in a plurality of colors, and further to display a video in full color. Even if the spatial light modulation area does not include a color filter, the irradiation device 60 time-divides the coherent light La, Lb, and Lc in each wavelength area, that is, the coherent light La, Lb, and Lc in fine time units. Irradiation may be performed sequentially, and the spatial light modulator 30 may be operated in a time division manner so as to form a modulated image corresponding to the coherent light in the irradiated wavelength region. Even in such an example, if the time-division operation is fast enough to be undetectable by the human eye, the image can be displayed in a plurality of colors when viewed by the human eye, and further, the image can be displayed in full color. Can be displayed.

  Further, according to the application form shown in FIG. 15, similarly to the basic form described above, the illuminated areas LZ of the respective coherent lights La, Lb, Lc diffracted by the hologram elements 55a, 55b, 55c of the optical element 50 are provided. The incident direction at each position of the lens changes continuously. Accordingly, the incident direction of the image light composed of the first to third coherent lights La, Lb, and Lc projected from the projection device 20 to each position on the screen 15 also changes continuously. For this reason, as already described in the basic embodiment, uncorrelated speckle patterns are superimposed and averaged, and as a result, speckles observed by the observer's eyes can be made inconspicuous.

  In addition, in the form shown in FIG. 15, the first to third coherent lights La, Lb, and Lc simultaneously illuminate the illuminated area LZ and are projected onto the screen 15 at the same time. The first to third coherent lights La, Lb, and Lc are generated by different light sources 61a, 61b, and 61c, and thus have no coherency. That is, the speckle pattern resulting from each of the coherent lights La, Lb, and Lc is uncorrelated, and the uncorrelated speckle pattern is superimposed on the screen 15 and averaged. For this reason, in the application form shown in FIG. 15, the speckle pattern can be made less noticeable.

  Also in the applied form shown in FIG. 15, the adhesive layer 56 and the heat conductive member 52 are provided on the other side of the hologram recording medium 55 including the first to third hologram elements 55a, 55b, and 55c. For this reason, the heat generated in the first to third hologram elements 55a, 55b, and 55c of the hologram recording medium 55 can be appropriately released to the outside.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to this Example.

[Examples and comparative examples concerning heat dissipation characteristics]
Example 1
As the transparent substrate 51, a 1 mm thick blue plate glass having a thermal conductivity of 1 W / m · K in the thickness direction and the surface direction was prepared. Next, a hologram photosensitive material 58 was provided on the other surface of the transparent substrate 51. As the hologram photosensitive material 58, the photosensitive composition for volume hologram recording described in Patent Document 3 described above was used. Next, the hologram photosensitive material 58 was irradiated with object light and reference light, whereby the hologram recording medium 55 was formed on the other side of the transparent substrate 51.

  Further, a heat conductive member 52 including a first heat conductive layer 54a made of a silicon wafer having a thermal conductivity 168 W / m · K in the thickness direction and the surface direction was prepared. Next, the hologram recording medium 55 formed on the transparent substrate 51 and the heat conductive member 52 were bonded using an adhesive layer 56 made of H20E. Thus, the optical element 50 provided with the transparent substrate 51, the hologram recording medium 55, the adhesive layer 56, and the heat conductive member 52 was produced. The adhesive layer 56 composed of H20E had a heat conductive additive 56a containing silver particles having a diameter of 45 μm or less and a binder 56b containing an epoxy UV curable resin. The thickness of the adhesive layer 56 was about 50 μm. Moreover, the thickness of the silicon wafer which comprises the 1st heat conductive layer 54a was 1 mm.

A region on the hologram recording medium 55 of the optical element 50 manufactured as described above was irradiated with laser light having a light flux density of 1.6 W / mm ² for 1 hour at room temperature. At this time, the beam diameter of the laser beam was about 1 mm.

  The optical element 50 after being irradiated with laser light for 1 hour was observed using thermography. FIG. 16 shows the observation result by thermography. As shown in FIG. 16, the maximum temperature of each region on the optical element 50 was 33.2 ° C. Further, in the optical element 50, a region where the temperature was significantly higher than the other regions, that is, a so-called heat spot was not observed. As an apparatus for thermography observation, a thermo gear G100 manufactured by NEC AVIO was used.

(Example 2)
An optical element 50 was produced in the same manner as in Example 1 except that the hologram recording medium 55 and the heat conductive member 52 were adhered using the adhesive layer 56 composed of H44. The adhesive layer 56 composed of H44 had a thermally conductive additive 56a containing gold particles having a diameter of 50 μm or less and a binder 56b containing an epoxy UV curable resin. Further, in the same manner as in Example 1, laser light was irradiated to a region on the hologram recording medium 55 of the optical element 50, and then the optical element 50 was observed using thermography. As a result, the maximum temperature of each region on the optical element 50 was about 35 ° C. Moreover, no heat spot was observed.

(Example 3)
An anisotropic conductive film HM-2 was used as the adhesive layer 56, and a graphite sheet (PGS) having a thermal conductivity of 700 W / m · K to 1600 W / m · K in the plane direction as the first thermal conductive layer 54a. The optical element 50 was produced in the same manner as in Example 1 except that. The adhesive layer 56 composed of the anisotropic conductive film HM-2 had a thermally conductive additive 56a containing vapor-grown carbon fibers and a binder 56b containing polyamide. Moreover, the thickness of the graphite sheet which comprises the 1st heat conductive layer 54a was 0.1 mm.

  In the same manner as in Example 1, a region of the optical element 50 on the hologram recording medium 55 was irradiated with laser light, and then the optical element 50 was observed using thermography. As a result, the maximum temperature of each region on the optical element 50 was about 30 ° C. Moreover, no heat spot was observed.

Example 4
A graphite sheet (PGS) having a thermal conductivity of 700 W / m · K to 1600 W / m · K in the surface direction is used as the first thermal conductive layer 54 a, and the thickness of the adhesive layer 56 is set to the heat of the adhesive layer 56. An optical element 50 was produced in the same manner as in Example 1, except that the diameter was approximately the same as the diameter of the silver particles constituting the conductive additive 56a. In the same manner as in Example 1, laser light was irradiated to a region on the hologram recording medium 55 of the optical element 50, and then the optical element 50 was observed using thermography. As a result, the maximum temperature of each region on the optical element 50 was about 30 ° C. Moreover, no heat spot was observed.

(Example 5)
The optical element 50 obtained by adding the 2nd heat conductive layer 54b which consists of a graphite sheet to the optical element 50 of the above-mentioned Example 1 was prepared. Specifically, in this embodiment, a second thermal conductive layer 54b made of a graphite sheet is provided on the other side of the first thermal conductive layer 54a made of a silicon wafer.

  Next, in the same manner as in Example 1, a region of the optical element 50 on the hologram recording medium 55 was irradiated with laser light. Then, the optical element 50 was observed using thermography. As a result, the maximum temperature of each region on the optical element 50 was about 35 ° C. Moreover, no heat spot was observed.

(Example 6)
As the heat conductive member 52, it arrange | positions on the other side of the contact bonding layer 56, the 2nd heat | fever which is arrange | positioned on the other side of the 1st heat conductive layer 54a which consists of a copper plate, and the 1st heat conductive layer 54a, and consists of a graphite sheet. The optical element 50 was produced in the same manner as in Example 1 except that the heat conductive member 52 having the conductive layer 54b was used. The thickness of the copper plate constituting the first thermally conductive layer 54a was 1 mm.

  In the same manner as in Example 1, a region of the optical element 50 on the hologram recording medium 55 was irradiated with laser light, and then the optical element 50 was observed using thermography. As a result, the maximum temperature of each region on the optical element 50 was about 30 ° C. Moreover, no heat spot was observed.

(Comparative Example 1)
Except that the same member as the transparent substrate 51 is disposed on the other side of the hologram recording medium 55 through an adhesive layer made of LCR0631 instead of the heat conductive member 52, the same as in the case of the first embodiment. Then, an optical element including the hologram recording medium 55 was produced. The adhesive layer composed of CR0631 includes an acrylic UV curable resin having a refractive index of 1.51, but does not include the above-described heat conductive additive 56a.

  In the same manner as in the case of Example 1, a region of the manufactured optical element on the hologram recording medium 55 was irradiated with laser light. Then, the optical element 50 was observed using thermography. FIG. 17 shows the observation result by thermography. As shown in FIG. 17, the maximum temperature of each region on the optical element was 47.2 ° C. In addition, as shown in FIG. 17, a region where the temperature is significantly higher than the other region, that is, a so-called heat spot was observed in the optical element.

  As is clear from the comparison between Examples 1 to 6 and Comparative Example 1, the adhesive layer 56 including the heat conductive additive 56 a and the heat conductive member 52 are disposed on the other side of the hologram recording medium 55. As a result, the temperature increase of the hologram recording medium 55 could be suppressed. Further, it was possible to prevent heat spots from being generated on the hologram recording medium 55.

DESCRIPTION OF SYMBOLS 5 Image 6 Scattering plate 10 Projection type image display apparatus 15 Screen 20 Projection apparatus 25 Projection optical system 30 Spatial light modulator 40 Illumination apparatus 50 Optical element 50a One side 50b The other side 51 Transparent substrate 52 Thermally conductive member 53 Reflection suppressing portion 53a Protruding portion 53b Dielectric multilayer film 54 Thermally conductive portion 54a First thermally conductive layer 54b Second thermally conductive layer 55 Hologram recording medium 56 Adhesive layer 56a Thermally conductive additive 56b Binder 58 Holographic photosensitive material 60 Irradiation device 61a Light source 65 Scanning device 66 Mirror device (reflection device)
66a Mirror (reflective surface)
67 Condensing lens LZ Illuminated area

Claims (12)

In an optical element that diffracts coherent light,
Comprising a transparent substrate, a hologram recording medium, an adhesive layer and a heat conductive member laminated in order from the side on which the coherent light is incident;
The hologram recording medium is configured to diffract coherent light that is transmitted through the transparent substrate and incident on the hologram recording medium;
The adhesive layer has a plurality number of thermally conductive additive, a binder to fill between each of the heat-conductive additive, and
The thermal conductivity of the thermal conductive member and the thermal conductivity of the thermal conductive additive are larger than the thermal conductivity of the transparent substrate,
The thermally conductive member has a reflection suppressing portion and a thermally conductive portion in order from the adhesive layer side,
The reflection suppressing portion constitutes the surface closest to the adhesive layer of the thermally conductive member, and suppresses reflection of coherent light incident from the adhesive layer side,
The thermal element includes an optical element having a thermally conductive layer containing a metal.   The optical element according to claim 1, wherein the thermally conductive additive of the adhesive layer has an elongated shape extending along a normal direction of the transparent substrate.   The optical element according to claim 2, wherein a dimension of the heat conductive additive of the adhesive layer in a normal direction of the transparent substrate is substantially the same as a film thickness of the adhesive layer.   The optical element according to any one of claims 1 to 3, wherein the thermally conductive additive of the adhesive layer includes at least one of carbon particles, metal particles, carbon fibers, or metal fibers. The thermally conductive layer of the thermally conductive part of the thermally conductive member has a first thermally conductive layer and a second thermally conductive layer arranged in order from the adhesive layer side,
5. The optical element according to claim 1, wherein a thermal conductivity of the second thermal conductive layer is larger than a thermal conductivity of the first thermal conductive layer.   The optical element according to claim 1, wherein the reflection suppressing portion includes a plurality of protrusions having a shape in which a cross-sectional area becomes smaller toward the adhesive layer side.   The optical element according to claim 1, wherein the reflection suppressing portion includes a dielectric multilayer film including a plurality of layers having different refractive indexes. An optical element that diffracts coherent light;
An irradiation device that irradiates the optical element with coherent light, and
The optical element includes a transparent substrate, a hologram recording medium, an adhesive layer, and a heat conductive member that are sequentially stacked from the side on which coherent light enters.
The hologram recording medium is configured to diffract coherent light that is transmitted through the transparent substrate and incident on the hologram recording medium;
The adhesive layer has a plurality number of thermally conductive additive, a binder to fill between each of the heat-conductive additive, and
The thermal conductivity of the thermal conductive member and the thermal conductivity of the thermal conductive additive are larger than the thermal conductivity of the transparent substrate,
The thermally conductive member has a reflection suppressing portion and a thermally conductive portion in order from the adhesive layer side,
The reflection suppressing portion constitutes the surface closest to the adhesive layer of the thermally conductive member, and suppresses reflection of coherent light incident from the adhesive layer side,
The thermally conductive portion has a thermally conductive layer containing a metal,
The irradiation device irradiates the optical element with coherent light so that the coherent light scans the hologram recording medium of the optical element,
A region on the hologram recording medium of the optical element irradiated with light by the irradiation device at an arbitrary moment is a part of the hologram recording medium.   The irradiating device and the irradiating device and the coherent light incident on each position of the holographic recording medium of the optical element from the irradiating device so as to illuminate regions that are diffracted by the holographic recording medium and overlap each other at least partially. The lighting device according to claim 8, wherein an optical element is disposed. A lighting device;
A spatial light modulator disposed at a position illuminated by coherent light from the illumination device,
The illumination device includes an optical element that diffracts coherent light, and an irradiation device that irradiates the optical element with coherent light.
The optical element includes a transparent substrate, a hologram recording medium, an adhesive layer, and a heat conductive member that are sequentially stacked from the side on which coherent light enters.
The hologram recording medium is configured to diffract coherent light that is transmitted through the transparent substrate and incident on the hologram recording medium;
The adhesive layer has a plurality number of thermally conductive additive, a binder to fill between each of the heat-conductive additive, and
The thermal conductivity of the thermal conductive member and the thermal conductivity of the thermal conductive additive are larger than the thermal conductivity of the transparent substrate,
The thermally conductive member has a reflection suppressing portion and a thermally conductive portion in order from the adhesive layer side,
The reflection suppressing portion constitutes the surface closest to the adhesive layer of the thermally conductive member, and suppresses reflection of coherent light incident from the adhesive layer side,
The thermally conductive portion has a thermally conductive layer containing a metal,
The irradiation device irradiates the optical element with coherent light so that the coherent light scans the hologram recording medium of the optical element,
The projection device, wherein a region on the hologram recording medium of the optical element irradiated with light by the irradiation device at an arbitrary moment is a part of the hologram recording medium. A projection device comprising: an illumination device; and a spatial light modulator disposed at a position illuminated by coherent light from the illumination device;
A screen on which a modulated image obtained on the spatial light modulator is projected,
The illumination device includes an optical element that diffracts coherent light, and an irradiation device that irradiates the optical element with coherent light.
The optical element includes a transparent substrate, a hologram recording medium, an adhesive layer, and a heat conductive member that are sequentially stacked from the side on which coherent light enters.
The hologram recording medium is configured to diffract coherent light that is transmitted through the transparent substrate and incident on the hologram recording medium;
The adhesive layer has a plurality number of thermally conductive additive, a binder to fill between each of the heat-conductive additive, and
The thermal conductivity of the thermal conductive member and the thermal conductivity of the thermal conductive additive are larger than the thermal conductivity of the transparent substrate,
The thermally conductive member has a reflection suppressing portion and a thermally conductive portion in order from the adhesive layer side,
The reflection suppressing portion constitutes the surface closest to the adhesive layer of the thermally conductive member, and suppresses reflection of coherent light incident from the adhesive layer side,
The thermally conductive portion has a thermally conductive layer containing a metal,
The irradiation device irradiates the optical element with coherent light so that the coherent light scans the hologram recording medium of the optical element,
An area on the hologram recording medium of the optical element irradiated with light by the irradiation apparatus at an arbitrary moment is a part of the hologram recording medium. A lighting device;
A screen disposed at a position illuminated by coherent light from the illumination device,
The illumination device includes an optical element that diffracts coherent light, and an irradiation device that irradiates the optical element with coherent light.
The optical element includes a transparent substrate, a hologram recording medium, an adhesive layer, and a heat conductive member that are sequentially stacked from the side on which coherent light enters.
The hologram recording medium is configured to diffract coherent light that is transmitted through the transparent substrate and incident on the hologram recording medium;
The adhesive layer has a plurality number of thermally conductive additive, a binder to fill between each of the heat-conductive additive, and
The thermal conductivity of the thermal conductive member and the thermal conductivity of the thermal conductive additive are larger than the thermal conductivity of the transparent substrate,
The thermally conductive member has a reflection suppressing portion and a thermally conductive portion in order from the adhesive layer side,
The reflection suppressing portion constitutes the surface closest to the adhesive layer of the thermally conductive member, and suppresses reflection of coherent light incident from the adhesive layer side,
The thermally conductive portion has a thermally conductive layer containing a metal,
The irradiation device irradiates the optical element with coherent light so that the coherent light scans the hologram recording medium of the optical element,
An area on the hologram recording medium of the optical element irradiated with light by the irradiation apparatus at an arbitrary moment is a part of the hologram recording medium.