JP5954641B2 - Illumination device, optical module, projection device, and projection-type image display device - Google Patents

Description

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

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

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

  However, high-intensity discharge lamps such as high-pressure mercury lamps have a relatively short life, and when used in optical projectors or the like, it is necessary to frequently replace the lamps. Further, since it is necessary to use a relatively large optical system such as a dichroic mirror in order to extract the light of each primary color component, there is a problem that the entire apparatus becomes large.

  In order to cope with such a problem, a method using a coherent light source such as a laser 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 laser light or other coherent light. When it appears on a screen, it is observed as speckled brightness irregularities (brightness irregularities). It becomes a factor having a physiological adverse effect on the person. The reason why speckles occur when coherent light is used is that coherent light reflected by each part of a scattering reflection surface such as a screen interferes with each other because of its extremely high coherence. . For example, in the following Non-Patent Document 1, detailed theoretical considerations regarding the generation of speckle are made.

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

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

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

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

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

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

A first lighting device according to the present invention comprises:
An optical element including a hologram recording medium capable of reproducing an image of a scattering plate;
An irradiation device for irradiating the optical element with the coherent light so that the coherent light scans on the hologram recording medium,
The coherent light is incident on each position of the hologram recording medium from the irradiation device along a certain direction, and the coherent light incident on each position of the hologram recording medium from the irradiation device is respectively input to the illuminated area. The irradiation device and the optical element are arranged so as to reproduce an image in a superimposed manner.

A second lighting device according to the present invention comprises:
An optical element including a hologram recording medium;
An irradiation device for irradiating the optical element with the coherent light so that the coherent light scans on the hologram recording medium,
The coherent light is incident on each position of the hologram recording medium from the irradiation device along a certain direction, and the coherent light incident on each position of the hologram recording medium from the irradiation device is the hologram recording medium. The illuminating device and the optical element are arranged so as to illuminate a region that is diffracted at (1) and overlaps at least partially.

  In the first or second illuminating device according to the present invention, the irradiation device changes the optical path of the coherent light from the light source that generates the coherent light and the coherent light on the hologram recording medium. A scanning device that scans the coherent light, and the scanning device includes a reflective surface that reflects the coherent light and is rotatable about at least one axis; And a deflecting element that deflects the traveling method of the light reflected by the reflecting device in the predetermined direction.

  In the first or second illumination device according to the present invention, the irradiation device includes a light source that generates the coherent light, and a holding mechanism that holds the light source so that an arrangement of the light source with respect to the optical element can be changed. The holding mechanism may change the arrangement of the light source with respect to the optical element so that the coherent light from the light source scans on the hologram recording medium.

A third lighting device according to the present invention comprises:
An optical element including a lens array that changes an optical path of incident light;
An irradiation device that irradiates the optical element with the coherent light so that the coherent light scans on the lens array;
The coherent light is incident on each position of the optical element from the irradiation device along a certain direction, and the coherent light incident on each position of the optical element from the irradiation device passes through an optical path by the lens array. The irradiation device and the optical element are arranged so as to change and illuminate the illuminated area.

A fourth lighting device according to the present invention includes:
An optical element including a light diffusing element that changes an optical path of incident light;
An irradiation device that irradiates the optical element with the coherent light so that coherent light scans the light diffusing element;
The coherent light is incident on each position of the light diffusing element from the irradiation device along a certain direction, and the coherent light incident on each position of the light diffusing element from the irradiation device is the light diffusing element. The irradiating device and the optical element are arranged so as to illuminate a region where the optical path is changed by at least a part of the optical path.

  In the third or fourth illumination device according to the present invention, the irradiation device changes a light source that generates the coherent light and an optical path of the coherent light from the light source so that the coherent light is the lens array or the A scanning device configured to scan the light diffusing element, and the scanning device includes a reflective surface that reflects the coherent light and is rotatable about at least one axis. You may make it have a reflective device and the deflection | deviation element which deflects the traveling method of the light reflected by the said reflective device in the said fixed direction.

  In the third or fourth illumination device according to the present invention, the irradiation device includes a light source that generates the coherent light, and a holding mechanism that holds the light source so that an arrangement of the light source with respect to the optical element can be changed. The holding mechanism may change the arrangement of the light source with respect to the optical element so that the coherent light from the light source scans the lens array or the light diffusing element.

The projection apparatus according to the present invention
Any one of the first to fourth lighting devices according to the present invention described above;
A spatial light modulator disposed at a position illuminated by coherent light from the illumination device.

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

  The projection device according to the present invention may further include an integrator rod disposed between the illumination device and the spatial light modulator in the optical path of coherent light. Such a projection apparatus according to the present invention may further include a relay optical system disposed between the integrator rod and the spatial light modulator in the optical path of coherent light.

  The projection device according to the present invention may further include a relay optical system disposed between the illumination device and the spatial light modulator in the optical path of coherent light.

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

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

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

FIG. 1 is a diagram for explaining an embodiment according to the present invention, and is a diagram showing a schematic configuration of an illumination device, a projection device, and a projection type video display device as an 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 diagram for explaining a modification of the optical element, and is a plan view showing the optical element together with a corresponding illuminated region. FIG. 7 is a diagram for explaining another modification of the optical element, and is a plan view showing the optical element together with a corresponding illuminated region. FIG. 8 is a diagram corresponding to FIG. 5, and is a perspective view for explaining a modified example of the irradiation apparatus and its operation. FIG. 9 is a diagram corresponding to FIG. 1 and a schematic configuration diagram for explaining another modification of the irradiation apparatus. FIG. 10 is a diagram corresponding to FIG. 1 and is a schematic configuration diagram for explaining a modification of the projection device. FIG. 11 is a diagram corresponding to FIG. 1 and is a schematic configuration diagram for explaining another modification of the projection device.

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

  FIGS. 1-11 is a figure for demonstrating the illuminating device which concerns on one embodiment of this invention, a projection apparatus, a projection type video display apparatus, and its modification. Among these, with reference to FIGS. 1-5, the illuminating device which concerns on one Embodiment, a projection apparatus, and a projection type video display apparatus are demonstrated. Thereafter, an example of a modification to the illumination device, the projection device, and the projection type image display device according to the embodiment will be described with reference to FIGS. 6 to 11 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. In the apparatus disclosed in Patent Document 2 described above, DMD is used as a spatial light modulator.

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

  The screen 15 may be configured as a transmissive screen or may be configured as a reflective screen. 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 illumination device 40 shown in FIGS. 1 and 2 includes an optical element 50 that directs the traveling direction of the coherent light toward the illuminated region LZ, and an irradiation device 60 that irradiates the optical element 50 with the coherent light. . The optical element 50 includes a hologram recording medium 55 that 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 is formed from a hologram recording medium 55.

  The hologram recording medium 55 constituting the optical element 50 in the illustrated example can receive the coherent light emitted from the irradiation device 60 as the reproduction illumination light La, and can diffract the coherent light with high efficiency. In particular, the hologram recording medium 55 can reproduce the image 5 of the scattering plate 6 by diffracting coherent light incident on each position, in other words, each minute region that should be called each point. ing.

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

  Then, the coherent light irradiated from the irradiation device 60 and scanned on the hologram recording medium 55 is diffracted by the hologram recording medium 55 at each position (each point or each region (hereinafter the same)) on the hologram recording medium 55. Incidence is made at an incident angle that satisfies the conditions. 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.

  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.

  For example, laser light from a laser light source that oscillates laser light in a specific wavelength region is used as the reference light Lr, and the reference light Lr travels along a certain direction as a parallel light flux and enters the hologram photosensitive material 58. As a specific example, laser light as a straight beam emitted from a laser light source is first diverged (spread) by a spatial filter or the like to be converted into a divergent light beam, and then a predetermined beam using a collimator. The light is converted into a parallel light beam having a cross-sectional area and then incident on the hologram photosensitive material 58.

  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 entire area of the hologram photosensitive material 58 with a substantially uniform light amount distribution. It becomes possible to do. 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. It is recorded on the hologram recording material 58 as a pattern (in the case of a volume hologram, for example, a refractive index modulation pattern). Thereafter, appropriate post-processing corresponding to the type of the hologram recording material 58 is performed, and the hologram recording material 55 is obtained.

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

  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. Therefore, each of the light beams forming the parallel light beam functioning as the reproduction illumination light La shown in FIG. 4 is individually incident on each position of the hologram recording medium 55 and has the same contour as each other. The images 5 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 such a hologram recording medium 55 with the coherent light irradiates each position of the hologram recording medium 55 of the optical element 50 with the coherent light traveling in a certain direction ds. It has become. In other words, the irradiation device 60 irradiates each position of the hologram recording medium 55 of the optical element 50 with coherent light along the optical path of one light beam forming a virtual parallel light beam.

  As a specific configuration, in the example shown in FIGS. 1, 2, and 5, the irradiation device 60 includes a laser light source 61a that generates coherent light in a specific wavelength region, and an optical path of the coherent light from the laser light source 61a. And a scanning device 65 to be changed. The scanning device 65 changes the optical path of the coherent light with time, so that the coherent light enters the optical element 50 so as to scan the hologram recording medium 55. In the example shown in FIGS. 1, 2, and 5, the irradiation device 60 is a reflection device that has a reflection surface 66 a that reflects coherent light and is rotatable about at least one axis RA. 66 and a deflecting element 67 that deflects the optical path of the light reflected by the reflecting device 66 in a direction parallel to a certain direction ds.

  In the illustrated embodiment, the reflecting device 66 is configured as a mirror device having a mirror as a reflecting surface 66a that can be rotated about one axis RA1. As shown in FIGS. 2 and 5, the mirror device 66 changes the traveling direction of coherent light from the laser light source 61a by changing the orientation of the mirror 66a. At this time, as shown in FIG. 2, the mirror device 66 receives the coherent light from the laser light source 61a at a certain position (reference position) SP. For this reason, the coherent light is changed in the traveling direction by the mirror device 66 that periodically rotates within a predetermined angle range, and then travels along the optical path of the light beam that diverges from the reference position SP. Become.

  On the other hand, the deflecting element 67 in the present embodiment is configured to collimate the divergent light beam diverging from the reference position SP and convert it into a parallel light beam, corresponding to the above configuration of the reflection device 66. Specifically, the deflection element 67 is configured as a lens and is disposed at a position where a divergent light beam diverging from the reference position SP can be collimated. For this reason, the coherent light whose optical path is reconstructed by the deflecting element 67 can be incident on the hologram recording medium 55 of the optical element 50 as reconstructed illumination light La that forms one light beam of a parallel light beam. 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. Are reproduced at the same position (illuminated area LZ).

  FIG. 5 shows a perspective view of the configuration of the illumination device 40 shown in FIG. The reflection device 66 shown in FIGS. 2 and 5 is configured to rotate the mirror 66a along one axis RA1. For this reason, the incident point IP1 of the coherent light whose traveling direction is continuously changed by the reflection device 66 to the deflection element 67 reciprocates along the linear scanning path PW1 on the incident surface of the lens forming the reflection device 66. become. In particular, in the example shown in FIG. 5, the rotation axis RA <b> 1 of the reflection device 66 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. Extending in parallel with the Y axis of the XY coordinate system. Then, the reflection surface 66a periodically rotates about an axis line RA1 parallel to the Y axis of the XY coordinate system defined on the plate surface of the hologram recording medium 55, so that the coherent light from the irradiation device 60 is reflected. The incident point IP2 to the optical element 50 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 the linear path PW2.

  Note that the wavelength of the coherent light incident on the hologram recording medium 55 of the optical element 50 does not need to be exactly the same as 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 recording material 58 contracts when the hologram recording medium 55 is produced. In such a case, the irradiation apparatus is considered in consideration of the contraction of the hologram recording material 58. It is better that the wavelength of the coherent light irradiated from 60 to the optical element 50 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. .

  For the same reason, even if the traveling direction of the light incident on each position of the hologram recording medium 55 of the optical element 50 does not take a path exactly along the same direction, the image 5 is substantially formed in the illuminated region LZ. Can be replayed. Actually, in the example shown in FIGS. 2 and 5, the mirror (reflective surface) 66a of the reflective device 66 is inevitably shifted from the rotation axis RA1. Therefore, when the mirror 66a is rotated about the rotation axis RA1 that does not pass through the reference position SP, the coherent light traveling from the reflection device 66 to the deflecting element 67 is divergent from the reference position SP in a strict sense. As a result, the coherent light traveling from the scanning device 65 toward the optical element 50 may not always travel in the same constant direction ds in a strict sense. However, in practice, the image 5 is substantially reproduced on the illuminated area LZ by coherent light incident on each position on the hologram recording medium 55 forming the optical element 50 from the irradiation device 60 having the illustrated configuration. be able to.

  From these points, terms that specify the geometric conditions such as “same direction”, “constant direction”, “parallel” and the like used in this specification are not limited to strict meanings, but have similar optical functions. Is to be interpreted including an error that can be expected.

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

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

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

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

  According to the aforementioned Non-Patent Document 1, it is effective to multiplex parameters such as polarization, phase, angle, and time and increase the mode in order to make speckle inconspicuous. The mode here refers to speckle patterns that are uncorrelated with each other. For example, when coherent light is projected from different directions onto the same screen from a plurality of laser light sources, there are as many modes as the number of laser light sources. In addition, when coherent light from the same laser light source is projected onto the screen from different directions by dividing the time, the mode is the same as the number of times the incident direction of the coherent light has changed during the time that cannot be resolved by the human eye. Will exist. When there are a large number of these modes, it is considered that the interference patterns of light are overlapped uncorrelatedly and averaged, and as a result, speckles observed by the observer's eyes become inconspicuous.

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

  Considering the illuminated area LZ as a reference, coherent light constantly enters each position in the illuminated area LZ, but the incident direction constantly changes as indicated by an arrow A1 in FIG. It will be. As a result, the light forming each pixel of the image formed by the light transmitted through the spatial light modulator 30 is projected to a specific position on the screen 15 while changing the optical path over time as indicated by an arrow A2 in FIG. Will come to be.

  The coherent light continuously scans on the hologram recording medium 55. Therefore, the incident position of the coherent light from the irradiation device 60 to the illuminated region LZ changes continuously, and accordingly, the incident direction of the coherent light from the projection device 20 to the screen 15 also changes continuously. Here, if the incident direction of the coherent light from the projection device 20 to the screen 15 changes only slightly (for example, several degrees), the speckle pattern generated on the screen 15 also changes greatly, and an uncorrelated speckle pattern. Are sufficiently superimposed. In addition, although the reflection device 66 of the scanning device 65 is configured by a MEMS mirror, a polygon mirror, or the like, the frequency of the reflection device 66 such as a MEMS mirror or a polygon mirror that is actually commercially available is usually several hundred Hz or more. A reflection device 66 reaching tens of thousands of Hz is not uncommon.

  From the above, according to this embodiment described above, the incident direction of coherent light changes temporally at each position on the screen 15 displaying an image, and this change is As a result, a non-correlated coherent light scattering pattern is multiplexed and observed by the human eye. Therefore, speckles generated corresponding to each scattering pattern are overlapped and averaged and observed by an observer. Thereby, speckles can be made very inconspicuous for an observer who observes the image displayed on the screen 15.

  Note that conventional speckles observed by humans include not only speckles on the screen caused by scattering of coherent light on the screen 15, but also scattering of coherent light before being projected on the screen. Speckle on the projection device side can also occur. The speckle pattern generated on the projection device side is projected onto the screen 15 via the spatial light modulator 30 so that it can be recognized by the observer. However, according to the present embodiment described above, the coherent light continuously scans on the hologram recording medium 55, and the coherent light incident on each position of the hologram recording medium 55 is the spatial light modulator 30. Are illuminated over the entire illuminated area LZ. That is, the hologram recording medium 55 forms a new wavefront that is separate from the wavefront used to form the speckle pattern, and the illumination area LZ and further the spatial light modulator 30 are formed in a complex and uniform manner. Through this, the screen 15 is illuminated. Due to the formation of a new wavefront on the hologram recording medium 55, the speckle pattern generated on the projection apparatus side is made invisible.

  By the way, Non-Patent Document 1 described above proposes a method using a numerical value called speckle contrast (unit%) as a parameter indicating the degree of speckle generated on the screen. This speckle contrast is defined as a value obtained by dividing the standard deviation of the actual luminance variation on the screen divided by the average luminance value when displaying a test pattern image that should have a uniform luminance distribution. Amount. The larger the speckle contrast value is, the larger the speckle occurrence level on the screen is, which indicates that the spot-like luminance unevenness pattern is more prominently presented to the observer.

  When the speckle contrast was measured for the projection display apparatus 10 described with reference to FIGS. 1 to 5, it was 3.0% (Condition 1). Further, as the above-described optical element 50, an uneven shape designed by using a computer so that the image 5 of the scattering plate 6 can be reproduced when receiving specific reproduction illumination light instead of the reflective volume hologram. The speckle contrast in the case of using the relief type hologram as a computer-generated hologram (CGH) having a ratio of 3.7% was (Condition 2). In HDTV (high-definition television) video display applications, a speckle contrast of 6.0% or less is a standard (for example, WO / 2001/081996) as a level at which an uneven brightness pattern is hardly recognized when an observer observes with the naked eye. However, the present embodiment described above sufficiently satisfies this criterion. In addition, when actually observed with the naked eye, brightness unevenness (brightness unevenness) that could be visually recognized did not occur.

  On the other hand, when the spatial light modulator 30 is illuminated with the laser light from the laser light source as a mere parallel light beam, that is, the scanning device 65 or the optical device is added to the spatial light modulator 30 of the projection display apparatus 10 shown in FIG. When the coherent light from the laser light source 61a was shaped into a parallel light beam and entered without passing through the element 50, the speckle contrast was 20.7% (Condition 3). Under these conditions, a spot-like luminance unevenness pattern was observed quite noticeably by visual observation.

  Further, when the light source 61a is replaced with a green LED (non-coherent light source) and light from the LED light source is incident on the spatial light modulator 30, that is, the projection type video display device 10 shown in FIG. When the non-coherent light from the LED light source was incident as a parallel light beam on the spatial light modulator 30 without passing through the scanning device 65 and the optical element 50, the speckle contrast was 4.0% (Condition 4). Under these conditions, brightness unevenness (brightness unevenness) that could be visually recognized by naked eye observation did not occur.

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

  In addition, according to the above-described embodiment, the following advantages can be obtained.

  According to the present embodiment described above, the reproduction illumination light La composed of coherent light emitted from the irradiation device 60 travels along the fixed direction ds toward the optical element 50, and the hologram recording of the optical element 50 is performed. The light enters each position of the medium 55. That is, the reproduction illumination light La made of coherent light irradiated from the irradiation device 60 follows the optical path of the light beam forming the parallel light flux and enters each position of the hologram recording medium 55 of the optical element 50. Therefore, the hologram recording medium 55 only needs to satisfy the Bragg condition by the reproduction illumination light La as a parallel light beam. According to the hologram recording medium 55 according to the present embodiment, the handling of the reproduction illumination light La can be greatly facilitated as follows.

  Unlike the present embodiment, when a hologram recording medium whose Bragg condition is satisfied by the reproduction illumination light as a divergent light beam, that is, by the reproduction illumination light traveling along the optical path of the light beam forming the divergent light beam, is used. When a hologram recording medium that satisfies the Bragg condition is used, the coherent light from the irradiation device must be incident on the hologram recording medium along the optical path of the light beam forming the divergent light beam. In this case, it is necessary to position the divergence point (divergence center) of the divergent light beam with respect to the hologram recording medium. However, in this embodiment, only the traveling direction ds of the coherent light is adjusted with respect to the hologram recording medium 55. In this respect, handling of the reproduction illumination light can be simplified. In addition, the divergent light beam gradually expands as the distance from the diverging point increases, but the optical path width of the parallel light beam does not increase. Further, the optical path of the parallel light beam can be changed by simple means such as a mirror. From these points, according to the present embodiment, the handling of the reproduction illumination light can be greatly facilitated, and the illumination device 40 can be downsized.

  Furthermore, the hologram recording medium 55 according to the present embodiment in which the Bragg condition is satisfied by the reproduction illumination light La as a parallel light beam can be manufactured by the above-described interference exposure method using the parallel light beam as the reference light Lr. When the hologram photosensitive material 58 is exposed using the reference light Lr composed of a parallel light beam, the handling of the reproduction illumination light La described above can be facilitated as compared with the case where the reference light composed of a convergent light beam or a divergent light beam is used. For the same reason, the handling of the reference light Lr can be greatly facilitated. From this point, according to the present embodiment, the design and mass replication of the hologram recording medium 55 can be facilitated.

  Moreover, according to this Embodiment mentioned above, the optical element 50 for making speckle inconspicuous functions also as an optical member for shaping and adjusting the beam form of the coherent light irradiated from the irradiation apparatus 60. Can do. Therefore, the optical system can be reduced in size and simplified.

  Furthermore, according to the present embodiment described above, coherent light incident on each position of the hologram recording medium 55 generates the image 5 of the scattering plate 6 at the same position and overlaps the image 5. A spatial light modulator 30 is arranged. Therefore, the light diffracted by the hologram recording medium 55 can be used for image formation with high efficiency, and the use efficiency of light from the light source 61a is excellent.

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

(Lighting device)
According to the embodiment described above, speckle can be effectively made inconspicuous. However, this effect is mainly due to the lighting device 40. Therefore, the lighting device 40 can be usefully used in various aspects. For example, the illumination device 40 can be used as simple illumination, and in this case, unevenness in brightness (luminance unevenness, flicker) can be made inconspicuous.

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

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

  Furthermore, as shown in FIG. 6, 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. 6 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. 6, the illuminated areas LZ-1, LZ-2,... May be illuminated as follows. First, the irradiation device 60 repeatedly scans the first hologram recording medium 55 of the optical element 50 so that the coherent light repeatedly scans the path PW2 along the longitudinal direction (the one direction) of the first hologram recording medium 55-1. -1 is irradiated with the coherent light. The coherent light incident on each position of the first hologram recording medium 55-1 is superimposed on the first illumination area LZ-1 to reproduce the image 5 of the linear or elongated scattering plate 6, and the first One illumination area LZ-1 is illuminated with coherent light. When a predetermined time elapses, the irradiation device 60 irradiates the second hologram recording medium 55-2 adjacent to the first hologram recording medium 55-1 with the coherent light, and the first illuminated region LZ-1 Instead, the second illuminated area LZ-2 adjacent to the first illuminated area LZ-1 is illuminated with coherent light. Hereinafter, the hologram recording medium is sequentially irradiated with coherent light, and the illuminated area corresponding to the hologram recording medium is illuminated with the coherent light. According to such a method, it is possible to read two-dimensional image information without moving the illumination device.

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

  In the embodiment described above, the illumination device 40 has the optical element 50 including the light diffusing element 55 made of a hologram recording medium, a lens array, or the like, and the coherent light whose profile is shaped by the light diffusing element 55 is converted into the spatial light modulator 30. An example of direct incidence is shown. However, the configuration of the projection device 20 including the illumination device 40 and the spatial light modulator 30 can be appropriately changed without being limited to such a configuration. As an example, in the example shown in FIG. 10, the integrator rod 22 and the relay optical system 23 are arranged in this order between the illumination device 40 and the spatial light modulator 30 in the optical path of the coherent light. In another example shown in FIG. 11, only the relay optical system 23 is disposed between the illumination device 40 and the spatial light modulator 30 in the optical path of coherent light.

  Many conventional projection devices and projection display devices, typically large conventional projection devices and projection display devices, have an integrator rod for making the illuminance distribution uniform upstream of the spatial light modulator. A relay optical system capable of transmitting cross-sectional information of the light traveling through the position to another position. The illumination device 40 described in the above-described embodiment can be applied to such a conventional projection device and projection display device. As an example, as shown in FIG. 10, the integrator rod 22 and the relay optical system 23 are used as they are. It is possible to use the relay optical system 23 as it is by removing the integrator rod 22 as shown in FIG. In the example shown in FIG. 11, the relay optical system 23 can transmit to the spatial light modulator 30 the light cross-section information on the surface VP on which the incident surface 22 a of the integrator rod 22 is disposed in FIG. 10. It has become. That is, the relative position of the relay optical system 23 in the example shown in FIG. 11 with respect to the optical element 50 matches the relative position of the incident surface 22a of the integrator rod 22 with respect to the optical element 50 in FIG.

(Projection-type image display device)
Moreover, although the example in which the hologram recording medium 55 is manufactured by the interference exposure method using the planar scattering plate 6 having a shape corresponding to the incident surface of the spatial light modulator 30 is shown, the present invention is not limited thereto. The hologram recording medium 55 may be manufactured by an interference exposure method using a scattering plate having a certain pattern. In this case, the image of the scattering plate having a certain pattern is reproduced by the hologram recording medium 55. In other words, the optical element 50 (hologram recording medium 55) illuminates the illuminated area LZ having a certain pattern. When this optical element 50 is used, the spatial light modulator 30 and the projection optical system 25 are also omitted from the projection-type image display device 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. .

  FIG. 7 discloses a specific example of such a modification. In the illustrated example, the optical element 50 includes first to third hologram recording media 55-1, 55-2, and 55-3. The first to third hologram recording media 55-1, 55-2, and 55-3 are arranged on surfaces parallel to the incident surface of the optical element 50 so as not to overlap each other. Each of the hologram recording media 55-1, 55-2, 55-3 can reproduce the image 5 having the outline of the arrow, in other words, the illuminated areas LZ-1, LZ- having the outline of the arrow. 2 and LZ-3 can be illuminated with coherent light. The first to third illuminated areas LZ-1, LZ-2, and LZ-3 respectively corresponding to the hologram recording media 55-1, 55-2, and 55-3 overlap each other on the same virtual plane. It is arranged not to become. In particular, in the illustrated example, the directions indicated by the arrows forming the illuminated areas LZ-1, LZ-2, and LZ-3 are all the same, and the first to third illuminated areas LZ-1, LZ-2 and LZ-3 are positioned in this order. For example, when the coherent light from the irradiation device 60 is scanning on the first hologram recording medium 55-1, the first illuminated region LZ-1 located at the rearmost side is illuminated. As an example, next, as shown in FIG. 7, the coherent light from the irradiation device 60 scans the second hologram recording medium 55-2, and the second illuminated region LZ-2 located in the middle is Illuminated. Thereafter, when the coherent light from the irradiation device 60 scans over the third hologram recording medium 55-3, the third illuminated area LZ-3 located in the foremost position is illuminated.

(Irradiation device)
In the embodiment described above, an example in which the irradiation device 60 includes the laser light source 61a and the scanning device 65 has been described. The scanning device 65 is a uniaxial rotation type reflection device 66 that changes the traveling direction of the coherent light by reflection, and the deflection that deflects the traveling direction of the coherent light traveling in various traveling directions from the reflecting device 66 in the same direction ds. Although the example which has the element 67 was shown, it is not restricted to this. As shown in FIG. 8, in the reflection device 66 of the scanning device 65, the mirror (reflection surface 66a) of the reflection device 66 intersects not only the first rotation axis RA1 but also the first rotation axis RA1. It may be rotatable about the second rotation axis RA2. In the example shown in FIG. 8, the second rotation axis RA2 of the mirror 66a is a first rotation axis RA1 extending in parallel with the Y axis of the XY coordinate system defined on the plate surface of the hologram recording medium 55. Are orthogonal. Since the mirror 66a is rotatable about both the first axis RA1 and the second axis RA2, the incident point IP1 of the coherent light from the reflection device 66 on the surface of the deflecting element 67 is in a two-dimensional direction. It becomes possible to move. As a result, the incident point IP <b> 2 of the coherent light from the irradiation device 60 to the optical element 50 can be moved in a two-dimensional direction on the plate surface of the hologram recording medium 55. As an example, as shown in FIG. 8, the incident point IP1 of the coherent light to the deflecting element 67 may be moved on the circumferential scanning path PW1, and the coherent light to the optical element 50 may be moved. The incident point IP2 may be moved on the circumferential scanning path PW2.

  The scanning device 65 may include two or more reflection devices (mirror devices) 66. In this case, even if the reflecting surface (mirror) 66a of each reflecting device 66 is rotatable only about a single axis, the incident point IP2 of the coherent light from the irradiation device 60 to the optical element 50 is The hologram recording medium 55 can be moved in a two-dimensional direction on the plate surface.

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

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

  On the other hand, specific examples of the deflection element 67 included in the scanning device 65 include a Fresnel lens, a hologram lens, a diffractive optical element (DOE), and the like in addition to the above-described resin and glass lenses. Can do.

  In the first place, the scanning device 65 is not essential, and the light source 61a of the irradiation device 60 is configured to be displaceable (moving, swinging, rotating) with respect to the optical element 50, and from the light source 61a by the displacement of the light source 61a with respect to the optical element. The irradiated coherent light may be scanned on the hologram recording medium 55. That is, in addition to continuously changing the optical path of the coherent light emitted from the light source 61a, or instead of continuously changing the optical path of the coherent light emitted from the light source 61a, the orientation of the light source 61a. It is also possible to change the emission direction of coherent light from the light source 61a by changing (arrangement, orientation, etc.).

  As a specific example, as illustrated in FIG. 9, the irradiation device 60 includes a light source 61 a that generates coherent light, and a holding mechanism 69 that holds the light source 61 a so that the arrangement of the light source 61 a with respect to the optical element 50 can be changed. You may make it have. The holding mechanism 69 changes the arrangement of the light source 61 a with respect to the optical element 50 so that the coherent light from the light source 61 a scans on the hologram recording medium 55. Also in the example shown in FIG. 9, the traveling direction of the coherent light incident on each position of the hologram recording medium 55 is a constant direction ds. The holding mechanism 69 is configured to translate (move in parallel) the light source 61a in a direction orthogonal to the traveling direction of the coherent light.

  Furthermore, although the light source 61a of the irradiation device 60 has been described on the assumption that the laser light shaped as a linear light beam is oscillated, the present invention is not limited to this. In particular, in the above-described form, the coherent light irradiated to each position of the optical element 50 is shaped by the optical element 50 into a light beam that enters the entire illuminated area LZ. Therefore, there is no inconvenience even if the coherent light irradiated to the optical element 50 from the light source 61a of the irradiation device 60 is not accurately shaped. For this reason, the coherent light generated from the light source 61a may be a divergent light beam. Further, the cross-sectional shape of the coherent light generated from the light source 61a may be an ellipse or the like instead of a circle. Furthermore, the transverse mode of the coherent light generated from the light source 61a may be a multimode.

  When the light source 61a generates a divergent light beam, the coherent light is incident not on a point but in a region having a certain area when entering the hologram recording medium 55 of the optical element 50. In this case, the light diffracted by the hologram recording medium 55 and incident on each position of the illuminated area LZ is multiplexed in angle. In other words, at each moment, coherent light is incident on each position of the illuminated area LZ from a certain angle range. Speckle can be made more inconspicuous by such multiplexing of angles.

  On the other hand, from the viewpoint of illuminating the spatial light modulator 30 with more accurately shaped light using the light diffusing element 55 comprising a hologram recording medium or a lens array, as shown by a two-dot chain line in FIG. The lens 62 may be disposed in the optical path from the light source 61a to the scanning device 65. The lens 62 is positioned so that the optical axis of the lens 62 is aligned with the optical axis of the coherent light emitted from the light source 61a. According to such a lens 62, divergent light from the light source 61a can be condensed and irradiated on the reference position SP (see FIG. 5). In this case, the coherent light can be incident on each position of the light diffusing element 55 of the optical element 50 from a predetermined direction more accurately. As a result, the spatial light modulator 30 is scheduled more accurately. It becomes possible to illuminate from the direction. As a result, the above-described effects can be achieved while effectively suppressing the light loss.

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

  Further, the irradiation device 60 may include a plurality of light sources that generate coherent light in different wavelength ranges. According to this example, a color that is difficult to display with a single laser beam can be generated by additive color mixing, and the illuminated area LZ can be illuminated with that color. In this case, in the projection apparatus 20 or the projection display apparatus 10, the spatial light modulator 30 includes, for example, a color filter, and a modulated image can be formed for each coherent light in each wavelength region. Makes it possible to display images in a plurality of colors. Alternatively, even if the spatial light modulator 30 does not include a color filter, the irradiation device 60 irradiates the coherent light of each wavelength region in a time-sharing manner, and the spatial light modulator 30 is irradiated with the wavelength region. Even when operating in a time-sharing manner so as to form a modulated image corresponding to the coherent light, it is possible to display an image in a plurality of colors. In particular, in the projection device 20 or the projection display apparatus 10, the irradiation device 60 includes a light source that generates coherent light in a wavelength region corresponding to red light, and a light source that generates coherent light in a wavelength region corresponding to green light. In the case where it includes a light source that generates coherent light in a wavelength range corresponding to blue light, it is possible to display an image in full color.

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

(Optical element)
In the embodiment described above, an example in which the optical element 50 includes the reflective volume hologram 55 using a photopolymer has been described, but the present invention is not limited thereto. As already described, the optical element 50 may include a plurality of hologram recording media 55. Further, the optical element 50 may include a volume hologram that is recorded using a photosensitive medium including a silver salt material. Further, the optical element 50 may include a transmission type volume hologram recording medium or a relief type (emboss type) hologram recording medium.

  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.

  Furthermore, in the embodiment described above, the optical element 50 expands the coherent light irradiated to each position, and uses the expanded coherent light as a light diffusing element or light diffusing element that illuminates the entire illuminated area LZ. Although the example which has the hologram recording medium 55 was shown, it is not restricted to this. The optical element 50 changes or diffuses the traveling direction of the coherent light irradiated to each position instead of the hologram recording medium 55 or in addition to the hologram recording medium 55, and diffuses the entire illuminated area LZ with coherent light. You may make it have a lens array as a light-diffusion element to illuminate. Specific examples of the lens array that functions as a light diffusing element include a total reflection type or a refractive type Fresnel lens or a fly-eye lens provided with a diffusion function. Also in such an illuminating device 40, the irradiating device 60 scans the light diffusing element formed of the lens array so that the coherent light scans the optical element 50, and the irradiating device 60 emits the coherent light. The irradiation device 60 and the optical element 50 are configured so that the coherent light incident on each position of the optical element 50 is changed in the traveling direction by the lens array that forms the light diffusing element and illuminates the illuminated area LZ. Thus, speckle can be effectively inconspicuous. Further, in the aspect in which the optical element 50 includes the lens array, other configurations such as the irradiation device 60, the spatial light modulator 30, the projection optical system 25, and the screen are similar to the aspect in which the optical element 50 includes the hologram recording medium 55. Various modifications (corrections / changes) can be made to 15.

(Lighting method)
In the above-described embodiment, the light diffusing device 60 is configured so that the irradiation device 60 can scan the coherent light on the optical element 50 in a one-dimensional direction, and includes the hologram recording medium 55 of the optical element 50, a lens array, and the like. The element 55 is configured to diffuse (spread and diverge) the coherent light irradiated to each position in a two-dimensional direction, whereby the illumination device 40 illuminates the two-dimensional illuminated region LZ. An example to do. However, as described above, the present invention is not limited to such an example. For example, the irradiation device 60 is configured to be able to scan the coherent light on the optical element 50 in a two-dimensional direction, and A light diffusing element 55 including a hologram recording medium 55 and a lens array of the optical element 50 is configured to diffuse (spread and diverge) the coherent light irradiated to each position in a two-dimensional direction. Thereby, the illuminating device 40 may illuminate the two-dimensional illuminated area LZ (the aspect already described with reference to FIG. 8).

  Further, as already mentioned, the irradiation device 60 is configured to be able to scan the coherent light on the optical element 50 in a one-dimensional direction, and from the hologram recording medium 55 or the lens array of the optical element 50. The configured light diffusing element 55 is configured to diffuse (spread and diverge) the coherent light irradiated to each position in a one-dimensional direction. The illumination area LZ may be illuminated. In this aspect, the scanning direction of the coherent light by the irradiation device 60 and the diffusion direction (expanding direction) of the light diffusing element 55 including the hologram recording medium 55 or the lens array of the optical element are parallel to each other. Also good.

  Further, the irradiation device 60 is configured to be able to scan the coherent light on the optical element 50 in a one-dimensional direction or a two-dimensional direction, and is configured from the hologram recording medium 55 of the optical element 50, a lens array, or the like. The diffusing element 55 may be configured to diffuse (spread and diverge) the coherent light irradiated to each position in a one-dimensional direction. In this aspect, as already described, the optical element 50 has a plurality of light diffusing elements 55, and the illumination device 40 is illuminated by sequentially illuminating the illuminated region LZ corresponding to each light diffusing element 55. A dimensional area may be illuminated. At this time, each illuminated area LZ may be sequentially illuminated at a speed as if it were illuminated simultaneously by the human eye, or it can be recognized that the illuminated area LZ is also illuminated sequentially by the human eye. It may be illuminated sequentially at such a slow speed.

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

5 Image 6 Scattering plate 10 Projection type image display device 15 Screen 20 Projection device 25 Projection optical system 30 Spatial light modulator 40 Illumination device 50 Optical element 55 Hologram recording medium 58 Hologram photosensitive material 60 Irradiation device 61a Light source 65 Scanning device 66 Mirror device (Reflection device)
66a Mirror (reflective surface)
67 Deflector (Condenser lens)
69 Holding mechanism LZ Illuminated area

Claims (14)

An optical element including a hologram recording medium;
An irradiation device for irradiating the optical element with the coherent light so that the coherent light scans on the hologram recording medium,
The coherent light is incident on each position of the hologram recording medium from the irradiation device along a certain direction, and the coherent light incident on each position of the hologram recording medium stationary from the irradiation device is the hologram. The irradiation is performed so that the entire area of the illuminated area is continuously illuminated while being diffracted by the recording medium and illuminating at least the entire illuminated area and scanning the hologram recording medium with the coherent light. An apparatus and the optical element are arranged,
The irradiation apparatus includes a light source that generates the coherent light, and a scanning device that changes the optical path of the coherent light from the light source so that the coherent light scans the hologram recording medium. ,
The scanning device includes a reflecting device that reflects the coherent light and has a reflecting surface that can be rotated about at least one axis, and the light reflected by the reflecting device to the optical element. A deflecting element that deflects the incident direction in the constant direction,
The illumination device has a lens in an optical path from the light source to the scanning device. An optical element including a light diffusing element that changes an optical path of incident light;
An irradiation device that irradiates the optical element with the coherent light so that coherent light scans the light diffusing element;
The coherent light is incident on each position of the light diffusing element from the irradiation device along a certain direction, and the coherent light incident on each position of the light diffusing element stationary from the irradiation device is the light. The light path is changed by the diffusing element to illuminate at least the entire illuminated area, so that the entire illuminated area continues to be illuminated while the coherent light is scanned over the light diffusing element. The irradiation device and the optical element are arranged,
The irradiation apparatus includes a light source that generates the coherent light, and a scanning device that changes the optical path of the coherent light from the light source so that the coherent light scans the light diffusing element. ,
The scanning device includes a reflecting device that reflects the coherent light and has a reflecting surface that can be rotated about at least one axis, and the light reflected by the reflecting device to the optical element. A deflecting element that deflects the incident direction in the constant direction,
The illumination device has a lens in an optical path from the light source to the scanning device.   The lighting device according to claim 2, wherein the diffusing element is a fly-eye lens. The reflective surface has a reference position for receiving coherent light from the light source;
The lens condenses and irradiates divergent light from the light source at a reference position,
The illumination device according to any one of claims 1 to 3, wherein the deflecting element is configured to collimate a divergent light beam diverging from the reference position and convert the divergent light beam into a parallel light beam.   The illuminating device according to claim 1, wherein the light source emits lateral multimode coherent light.   The illumination device according to any one of claims 1 to 4, wherein a cross-sectional shape of the coherent light emitted from the light source is an elliptical shape. The lighting device according to any one of claims 1 to 6,
A spatial light modulator disposed at a position illuminated by coherent light from the illumination device.   The projection apparatus according to claim 7, further comprising a projection optical system that projects a modulated image obtained on the spatial light modulator onto a screen.   The projection device according to claim 7, further comprising an integrator rod disposed between the illumination device and the spatial light modulator in an optical path of coherent light.   The projection apparatus according to claim 9, further comprising a relay optical system disposed between the integrator rod and the spatial light modulator in the optical path of coherent light.   The projection device according to claim 7, further comprising a relay optical system disposed between the illumination device and the spatial light modulator in an optical path of coherent light. The projection device according to any one of claims 7 to 11,
And a screen on which a modulated image obtained on the spatial light modulator is projected. The lighting device according to any one of claims 1 to 6,
A projection-type image display device comprising: a screen disposed at a position illuminated by coherent light from the illumination device. An optical element including a light diffusing element that changes an optical path of incident light;
A scanning device that changes the optical path of the coherent light from a light source that generates coherent light so that the coherent light scans over the light diffusing element; and
The coherent light is incident on each position of the light diffusing element from the scanning device along a certain direction, and the coherent light incident on each position of the light diffusing element stationary from the scanning device is the light. The light path is changed by the diffusing element to illuminate at least the entire illuminated area, so that the entire illuminated area continues to be illuminated while the coherent light is scanned over the light diffusing element. The scanning device and the optical element are arranged,
The scanning device includes a reflecting device that reflects the coherent light and has a reflecting surface that can be rotated about at least one axis, and the light reflected by the reflecting device to the optical element. An optical module comprising: a deflecting element that deflects an incident direction in the predetermined direction.

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