JP5429343B2 - Image display device - Google Patents

Description

  The present invention relates to an illumination device, an image display device, and a polarization conversion diffusing member.

2. Description of the Related Art In recent years, projectors that illuminate a light modulation device with an illumination device and enlarge and project image light emitted from the light modulation device onto a screen using a projection optical system such as a projection lens are widely known.
Conventionally, metal halide lamps, halogen lamps, and the like have been used as illumination devices for the projectors, but in recent years, use of semiconductor lasers (LDs) has been proposed in order to reduce the size of the illumination devices and projectors. Advantages of the laser light source include not only miniaturization but also good color reproducibility, video display with high brightness and contrast, and instant lighting.

  However, since the laser light is coherent light, a speckle pattern in which bright spots and dark spots are randomly distributed is generated in the enlarged projected image light. The speckle pattern is generated when light emitted from each point of the projection optical system interferes with an irregular phase relationship. An image having this speckle pattern is a problem because it gives a glare and glimmer to the observer.

In order to solve this problem, an image display device has been proposed in which light emitted from a light source is diffused by a diffusion plate to reduce speckle noise (see, for example, Patent Documents 1 to 3).
In the display device described in Patent Document 1, light emitted from a laser light source is diffused by a diffusion element, and the diffused light is focused on a spatial light modulator by a lens. The light converted into an image by the spatial light modulator is displayed on the observation surface.

  In the projection type image display device described in Patent Document 2, the light emitted from the first dimensional display element is scanned by a galvanometer mirror, and the scanned light passes through a vibrating diffuser. Thereby, the light emitted from the diffuser is diffused and projected on the screen by the projection lens.

  In addition, in the image display system described in Patent Document 3, the first optical system forms an intermediate image of light emitted from the light source on the light diffusion angle conversion element, and the incident angle incident on the light diffusion angle conversion element. The emission angle emitted from the light diffusion angle conversion element is increased. By oscillating the light diffusion angle conversion element, the temporal change of the speckle pattern is integrated in the human eye, and speckle noise can be reduced.

Japanese Patent Laid-Open No. 6-208089 JP 2005-84117 A JP 2006-53495 A

However, in the techniques described in Patent Documents 1 and 2, speckle noise is reduced by diffusing the light emitted from the light source by the diffusion plate, but to a level that cannot be perceived by human eyes with only the diffusion plate. It is difficult to reduce speckle noise.
In the technique of Patent Document 3, since many scattering patterns can be projected on the screen by optimizing the relationship between the scattering angle of the light diffusion angle conversion element and the swallowing angle of the projection lens, it is bright and has specs. It is possible to project an image with reduced noise. However, even in this configuration, it is difficult to reduce speckle noise to a level that cannot be perceived by human eyes.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an illumination device, an image display device, and a polarization conversion diffusing member that can more reliably reduce speckle noise. To do.

An image display apparatus according to the present invention is an image display apparatus that irradiates a projection surface, a laser light source that emits laser light, and a polarization direction of incident laser light that is converted into a first polarization direction and emitted. A polarization conversion device disposed at a subsequent stage of the laser light source, and a second region that converts the polarization direction of the incident laser light into a second polarization direction to be emitted, and the laser A light modulation device that is arranged downstream of the light source and modulates the incident laser light in accordance with an image signal; a projection unit that is arranged in the rear stage of the light modulation device and projects the incident laser light on the projection surface; A light diffusing unit provided at a subsequent stage of the polarization conversion device, wherein the polarization conversion device is disposed at an aperture stop or a pupil position of the projection unit, and the light diffusion unit is located at an intermediate image position of the light modulation device. Arranged by the polarization converter After converting the polarization direction of the laser light emitted from the light source to each of said areas, the converted laser beam, characterized in that diffusing by the light diffusing portion.

In the image display device according to the present invention, the laser light emitted from the laser light source is modulated in accordance with the image signal by the light modulation device, and the modulated laser light is projected onto the projection surface by the projection means. At this time, the laser light projected on the projection surface is modulated by, for example, a light modulation device and enters the polarization conversion element. That is, the polarization direction of the image emitted from the light modulation device is converted for each region. Then, laser beams having different polarization directions are projected onto the projection surface. Therefore, since laser beams having different polarization directions do not interfere with each other, it is possible to reduce speckle noise of an image projected on the projection surface. In addition, since the polarization conversion device is arranged at the aperture stop or pupil position of the projection means, it is possible to give different polarization information to various spatial frequencies. Further, after the polarization direction of the laser light is converted for each region by the polarization conversion device , the laser light is further diffused by the light diffusion unit disposed at the intermediate image position of the light modulation device. That is, since the laser beams having different polarization directions are diffused for each region, the laser beams having different polarization directions are superimposed on the projection surface. Therefore, it is possible to further reduce speckle noise of the image projected on the projection surface.
In the image display device of the present invention, it is preferable that the size of the first region and the second region is smaller than the size of the aperture stop of the projection unit.
In the image display device according to the present invention, since the sizes of the first region and the second region are smaller than the size of the aperture stop of the projection unit, speckle noise can be reliably reduced.
In the image display device of the present invention, it is preferable that the polarization converter is rotated or rocked.
In the case where the light modulation device is a liquid crystal element, laser light having a specific polarization direction is made incident on the light modulation device using a polarizing member. Therefore, by arranging the polarization conversion device on the rear stage side of the liquid crystal element, it becomes possible to efficiently project laser beams having different polarization directions for each region onto the projection surface.

  In the image display device according to the present invention, the laser light emitted from the laser light source or the laser light emitted from the polarization conversion device is diffused by the light diffusing unit. That is, by providing the light diffusing unit, the laser light can be more reliably diffused, so that speckle noise of an image projected on the projection surface can be more effectively reduced.

  In the image display device of the present invention, the polarization conversion device and the light diffusing unit are disposed on an optical path between the light modulating device and the projection surface, and at least the light diffusing unit includes the light modulating unit. It is preferably arranged at a position where an intermediate image is formed by laser light emitted from the apparatus.

  In the image display device according to the present invention, the laser light modulated by the light modulation device has its polarization direction converted for each region by the polarization conversion device, for example, and is diffused by the light diffusion unit. At this time, since the light diffusing unit is disposed at a position where the intermediate image is formed, the intermediate image is diffused by the light diffusing unit and the image is projected onto the projection surface. Therefore, speckle noise of an image projected on the projection surface can be more reliably reduced.

  In the image display device of the present invention, an intermediate image forming optical system is disposed on an optical path between the light modulation device and the light diffusing unit, and the intermediate image is formed by the intermediate image forming optical system. Is preferred.

In the image display device according to the present invention, the laser light modulated by the light modulation device forms an intermediate image by the intermediate image forming optical system and is diffused by the light diffusion portion. In addition, since the polarization direction of the laser light projected onto the projection surface is different for each region by the polarization conversion device, it is possible to reduce speckle noise in the image projected onto the projection surface.
Therefore, by forming the intermediate image with the intermediate image forming optical system, the intermediate image can be more reliably formed at the position of the light diffusing portion, so speckle noise of the image projected on the projection surface can be more reliably generated. It becomes possible to reduce it.

  In the image display device of the present invention, it is preferable that the light diffusing portion is formed by causing two lights to interfere with the other surface.

  In the image display device according to the present invention, since the light diffusing portion is formed by causing two lights to interfere with each other, generation of high-order diffracted light can be controlled by the light diffusing portion. That is, it is possible to improve the light utilization efficiency by irradiating two lights and forming a light diffusion portion that does not generate unnecessary high-order diffracted light.

In the image display device of the present invention, it is preferable that the light diffusion portion is a diffraction element.
In the image display device according to the present invention, since the light diffusion portion is a diffraction element, the diffusion angle of the laser light diffused in the light diffusion portion can be within a predetermined range. Therefore, it becomes possible to improve the utilization efficiency of laser light.

  In the image display device of the present invention, after the polarization direction of the laser light emitted from the light source by the polarization conversion device is converted for each region, the converted laser light is diffused by the light diffusion unit. preferable.

  In the image display device according to the present invention, after the polarization direction of the laser beam is converted for each region by the polarization conversion device, the converted laser beam is diffused by the light diffusion unit. In other words, since laser light having a different polarization direction is diffused in each region, laser light having a different polarization direction is superimposed on the projection surface, so that speckle noise of an image projected on the projection surface is more effective. It becomes possible to reduce it.

In the image display device of the present invention, it is preferable that the polarization conversion device is made of a birefringent material having a phase difference between an ordinary ray and an extraordinary ray.
In the image display device according to the present invention, since the polarization conversion device is made of a birefringent material in which the phase difference between the ordinary ray and the extraordinary ray is different, the polarization direction can be efficiently converted for each region.

  In the image display device of the present invention, 0 ≦ Re ≦ λ / 2, where λ is the wavelength of the laser beam emitted from the laser light source and Re is the phase difference between the ordinary ray and the extraordinary ray. It is preferable.

  In the image display device according to the present invention, the polarization conversion device is made of a birefringent material in which the phase difference Re between the ordinary ray and the extraordinary ray is in the range of 0 ≦ Re ≦ λ / 2. Therefore, it is possible to reduce speckle noise.

In the image display device of the present invention, it is preferable that the concave portion is formed by sandblasting.
In the image display device according to the present invention, the concave portion can be formed by a simple method by sandblasting.

  In the image display device of the present invention, it is preferable to form the concave portion by photolithography and etching.

  In the image display device according to the present invention, the concave portion is formed by a simple method by photolithography and etching. Further, since the size of the concave portion can be changed by changing the size of the opening of the mask and the transmittance, the concave portion can be formed as designed as compared with the sandblasting process.

  In the image display device of the present invention, it is preferable that the size of the first region and the second region is smaller than the size of the image forming region of the light modulation device.

  In the image display device according to the present invention, since the size of the first region and the second region is smaller than the size of the image forming region of the light modulation device, the image emitted from the image forming region is polarization-converted. When it passes through the device, it is divided into a plurality of regions having different polarization directions. Therefore, since images having different polarization directions for each region are projected onto the projection surface, speckle noise can be reliably reduced.

  Further, the polarization conversion diffusing member of the present invention includes a first region for converting the polarization direction of the incident laser light into the first polarization direction to be emitted, and a polarization direction of the incident laser light in the second polarization direction. A second region to be converted and emitted, and a polarization conversion device provided on one surface of the base material, and provided on the other surface of the base material opposite to the one surface and incident A light diffusing portion for diffusing the laser light to be formed, and the light diffusing portion is formed by causing two lights to interfere with the other surface.

  In the polarization conversion diffusing member according to the present invention, since the light diffusing portion is formed by causing two lights to interfere with each other, the generation of high-order diffracted light can be controlled by the light diffusing portion. That is, it is possible to improve the light use efficiency by irradiating two lights and forming a diffusion layer that does not generate unnecessary high-order diffracted light.

1 is a plan view showing a projector according to a first embodiment of the invention. It is a top view which shows the projection apparatus of the projector of FIG. It is a front view which shows the polarization conversion part of the projector of FIG. It is sectional drawing which shows the polarization conversion part of the projector of FIG. It is explanatory drawing which shows the difference in the polarization direction of the laser beam which passes the polarization conversion part of the projector of FIG. It is a top view which shows the projector which concerns on 2nd Embodiment of this invention. It is a top view which shows the projector which concerns on 3rd Embodiment of this invention. It is a top view which shows the modification of the projector which concerns on 3rd Embodiment of this invention. It is a top view which shows the modification of the projector which concerns on 3rd Embodiment of this invention. It is a front view which shows the polarization conversion part of the projector of FIG. 8, FIG. It is a top view which shows the polarization conversion diffusion member which concerns on 4th Embodiment of this invention. It is a top view which shows the polarization conversion diffusion member which concerns on 5th Embodiment of this invention. It is a top view which shows the formation method of the polarization conversion diffusion member which concerns on 6th Embodiment of this invention. It is a top view which shows the formation method of the polarization conversion diffusion member which concerns on 7th Embodiment of this invention.

  Hereinafter, embodiments of an illumination device, an image display device, and a diffusion member according to the present invention will be described with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

[First Embodiment]
A projector according to a first embodiment of the invention will be described with reference to FIGS.
In the present embodiment, a projector that projects color light including image information generated by a spatial light modulation device on a screen as a projector on a screen will be described as an example.

In the projector (image display device) 1 according to the present embodiment, as shown in FIG. 1, a reflective screen (projected surface) 50 is used, and light including image information is projected onto the screen 50 from the front side of the screen 50. Project.
The projector 1 includes a light source device (laser light source) 10, a light modulation device 20, a dichroic prism (color light combining unit) 30, and a projection device (projection unit) 40. In the following description, the light modulation device is referred to as a liquid crystal light valve.

The light source device 10 includes a red light source device (laser light source) 10R that emits red laser light, a green light source device (laser light source) 10G that emits green laser light, and a blue light source device that emits blue laser light (laser light source). Laser light source) 10B.
The liquid crystal light valve (light modulation device) 20 includes a two-dimensional transmissive red light modulation device 20R that modulates the laser light emitted from the red light source device 10R according to image information, and a green light source device 10G. Two-dimensional transmissive green light modulator 20G that modulates the laser light emitted from the light source according to image information, and two-dimensional light that modulates the laser light emitted from the blue light source device 10B according to the image information. And a transmissive blue light modulation device 20B. Further, the dichroic prism 30 synthesizes each color light modulated by each light modulator 20R, 20G, 20B.
The projection device 40 projects the laser beam synthesized by the dichroic prism 30 onto a screen (projected surface) 50.

  Each of the light source devices 10R, 10G, and 10B adjusts the light source 11 that emits laser light, the diffractive optical element 12 that diffracts the laser light emitted from the light source 11, and the emission angle of the laser light diffracted by the diffractive optical element 12. And an angle adjusting optical element 14. In addition, the structure of each light source device 10R, 10G, 10B is not restricted to this.

The projection device 40 will be described with reference to FIG. 2 shows the liquid crystal light valves 20R, 20G, and 20B, the projection device 40, and the screen 50 in order to make it easy to see the optical path diagram in which the laser light incident on the liquid crystal light valves 20R, 20G, and 20B is projected on the screen 50. A linear arrangement is shown, and the dichroic prism 30 is omitted.
As shown in FIG. 2, the projection device 40 includes a first lens group 41, a polarization conversion plate (polarization conversion device) 43, and a second lens group 45 in this order on the optical path. The polarization conversion plate 43 is rotated by an actuator (not shown) around a rotation axis P that is a central portion. Although the central portion of the polarization conversion plate 43 is the rotation axis P, the present invention is not limited to this, and the end portion of the polarization conversion plate 43 may be the rotation axis P.

  The first lens group (intermediate image forming optical system) 41 forms the laser beam synthesized in the dichroic prism 30 as an intermediate image on or near the polarization conversion plate 43. The first lens group 41 is an equal-magnification imaging lens including a front lens group 41a and a rear lens group 41b that are arranged substantially symmetrically with respect to the aperture stop 42. Further, it is desirable that the front lens group 41a and the rear lens group 41b have both-side telecentric characteristics in consideration of the viewing angle characteristics of the liquid crystal light valves 20R, 20G, and 20B. The front lens group 41a and the rear lens group 41b are configured to include a plurality of convex lenses and concave lenses, but the shape, size, arrangement interval and number of lenses, telecentricity, magnification and other lens characteristics are required. It is appropriately changed depending on the characteristics.

As shown in FIG. 3, the polarization conversion plate 43 has a plurality of regions A, and laser light having a plurality of types of polarization directions is emitted from the plurality of regions A. That is, for example, the polarization directions of the laser light emitted from the first region A1 and the fourth region A4 are linearly polarized light having different vibration directions, and are emitted from the second region A2 and the third region A3. The polarization direction of the laser light is elliptically polarized. Note that the polarization directions of the laser beams emitted from the plurality of regions A may all be different, or some of the same polarization directions may exist.
Further, as shown in FIG. 3, the polarization conversion plate 43 is disposed at a position where the intermediate image T formed by the first lens group 41 is formed. The size of each region A of the polarization conversion plate 43 is smaller than the size of the intermediate image T. Further, since the first lens group 41 is an equal-magnification imaging lens, the size of the image forming area of the liquid crystal light valves 20R, 20G, and 20B is substantially the same as that of the intermediate image T. Accordingly, the size of each region A of the polarization conversion plate 43 is smaller than the size of the image forming regions of the liquid crystal light valves 20R, 20G, and 20B.
Note that the size of each region A of the polarization conversion plate 43 may be smaller than the size of the aperture stop 42.
In the present embodiment, the sizes of the regions A of the polarization conversion plate 43 are all the same, but they may all be different, or several types of sizes may be mixed.

Specifically, as shown in FIG. 4, the polarization conversion plate 43 has a plurality of rectangular shapes with different depths on the exit end face 43b opposite to the entrance end face 43a on which the laser light synthesized from the dichroic prism 30 enters. It has a recess (uneven structure) 43M. Thereby, the laser beam emitted from the polarization conversion plate 43 is diffused. Further, one recess 43M forms one region A shown in FIG.
The polarization conversion plate 43 is made of a material having a high photoelastic coefficient, for example, polycarbonate. Polycarbonate can have different refractive indexes in a stretching direction and a direction substantially perpendicular to the stretching direction due to stress applied to the material during stretching, and functions as a birefringent material having uniaxial optical anisotropy. .

Next, the polarization direction of the laser light passing through each region A of the polarization conversion plate 43 will be described with reference to FIG. In FIG. 5, the size of the other regions Ac, Ad, Ae... Is larger than that of the other regions Ac, Ad, Ae... For easy understanding of the polarization direction of the laser light emitted from the regions Aa and Ab. In practice, the laser beam synthesized by the dichroic prism 30 is not incident on each region A of the polarization conversion plate 43, but is incident on the entire incident end face 43a.
Here, when the photoelastic coefficient of the material forming the polarization conversion plate 43 is C [Pa ⁻¹ ] and the stress applied to the material during stretching is σ [Pa], the refractive index difference between the ordinary ray and the extraordinary ray is

It is represented by
In addition, a material having a refractive index difference Δn has a thickness difference between adjacent regions A as d.

The relationship holds. Therefore, the phase difference Re can be given to the ordinary ray and the extraordinary ray due to the thickness difference d between the adjacent regions A, and the polarization direction of the laser light passes through the polarization conversion plate 43 so that the polarization direction is different for each region A. Different.

  Thereby, when a linearly polarized light beam inclined by 45 ° with respect to the optical axis of the material of the polarization conversion plate 43 is incident on the polarization conversion plate 43 made of a material having uniaxial optical anisotropy, the adjacent region The phase difference Re varies depending on the difference in the thickness difference d of A. That is, as shown in FIG. 5, the polarization direction of the light beam emitted from the emission end face 43 b of the polarization conversion plate 43 is different for each region A. For example, the polarization direction of the emitted light emitted from the area Aa is the same direction as the incident light indicated by the arrow B1 because the optical distance between the ordinary ray and the extraordinary ray is different and the phase is the same. On the other hand, since the polarization direction of the emitted light emitted from the region Ab is different from the optical distance and the phase of the ordinary ray and the extraordinary ray, the direction of the incident light and the phase rotated by 90 ° as indicated by an arrow B2 Become. The phase difference Re for each region A may be in the range of 0 to λ / 2. In this way, laser beams of a plurality of types of polarization directions are emitted from the plurality of regions Aa, Ab, Ac...

Next, a method for displaying an image on the screen 50 by the projector 1 of the present embodiment configured as described above will be described.
First, red light, green light, and blue light emitted from each of the light source devices 10R, 10G, and 10B become uniform laser light and enter the angle adjusting optical element 14. The uniform red light, green light, and blue light emitted from the angle adjusting optical element 14 enter the liquid crystal light valves 20R, 20G, and 20B and are combined by the dichroic prism 30.
The combined laser light enters the polarization conversion plate 43 through the first lens group 41. The polarization direction of the laser light incident on the polarization conversion plate 43 is linearly polarized light. Then, in the polarization conversion plate 43, the polarization direction is converted for each region A and then diffused at the exit end face 43b. Therefore, a plurality of types of linearly polarized light having different polarization directions and elliptically polarized light having different ellipticities are emitted from the polarization conversion plate 43. Then, images having different polarization directions for each region A are projected onto the screen 50 by the second lens group 45. At this time, the laser light projected onto the screen 50 is also laser light having a different polarization direction for each region A.

In the projector 1 according to the present embodiment, laser beams of a plurality of types of polarization directions emitted from the polarization conversion plate 43 are diffused and projected onto the screen 50. Therefore, laser beams having different polarization directions do not interfere with each other, and speckle noise of an image projected on the screen 50 can be reduced.
In addition, since the polarization conversion plate 43 is disposed at a position where the intermediate image is formed, the intermediate image T is diffused by changing the polarization direction for each region A, so speckle noise can be reduced more reliably. It becomes. In addition, since the intermediate image is formed by the first lens group 41, the intermediate image T can be more reliably formed at the position of the polarization conversion plate 43.
Further, since the polarization conversion plate 43 has the concave portion 43M and diffuses the laser light emitted from each of the light source devices 10R, 10G, and 10B, it is possible to reduce the size and cost of the entire device.

Further, since polycarbonate having a high birefringence is used as the material of the polarization conversion plate 43, the phase difference Re between the ordinary ray and the extraordinary ray can be increased. As a result, the laser light projected on the screen 50 is less likely to interfere, and speckle noise can be reduced.
That is, the projector 1 of this embodiment can reduce speckle noise more reliably.

  Also, an illumination that includes a laser light source that emits laser light and the polarization conversion plate 43 described above, and projects diffused laser light having a different polarization direction onto the projection surface for each region A emitted from the polarization conversion plate 43. It may be a device. Moreover, the illuminating device may be provided with projection means for projecting laser light onto the projection surface. When such an illuminating device is used in a laser processing machine or a laser exposure machine, the projection surface can be irradiated with laser light with reduced speckle noise, so that laser processing and laser exposure can be performed with high accuracy. It becomes possible.

In this embodiment, polycarbonate is used as a material for forming the polarization conversion plate 43, but the present invention is not limited to this. The material for forming the polarization conversion plate 43 is preferably formed of a material having a high birefringence.
Further, although the polarization conversion plate 43 is configured to rotate, it may not be rotated depending on the shape of the screen. Furthermore, the structure which rocks | polarizes the polarization converter plate 43 may be sufficient.
Moreover, although the polarization conversion plate 43 having a diffusion function has been described as an example, the present invention is not limited to this, and a light diffusion unit that diffuses laser light may be provided separately from the polarization conversion plate 43. In this configuration, the polarization conversion plate 43 and the light diffusing unit may be arranged close to or in contact with each other. Further, when the polarization conversion plate 43 and the light diffusing portion are provided separately, at least the light diffusing portion may be arranged at a position where the intermediate image is formed. As described above, by providing the light diffusing unit, the laser light can be more reliably diffused, so that speckle noise can be further reduced.
Moreover, although the polarization conversion plate 43 in which the recessed part 43M was formed in the output end surface 43b was used, the recessed part may be formed also in the incident end surface 43a.
Further, although a transmissive liquid crystal light valve is used as the light modulation device, any of a reflective liquid crystal light valve, DMD (Digital Mirror Device), and LCOS (Liquid Crystal On Silicon) may be used.

[Second Embodiment]
Next, a second embodiment according to the present invention will be described with reference to FIG. In the drawings of the respective embodiments described below, portions having the same configuration as those of the projector 1 according to the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.
The projector 60 according to this embodiment differs from the first embodiment in that a polarization conversion plate 43 similar to that of the first embodiment is disposed between the light path between the light source (laser light source) 61 and the reflective light valve 64. Different. Other configurations are the same as those of the first embodiment.

As shown in FIG. 6, the projector (image display device) 60 includes a light source 61, a hologram element 62, a polarization conversion plate (polarization conversion device) 43, a collimating lens 63, and a reflection type light valve (reflection type light). A modulation device 64 and a projection device 65 are provided.
The light source 61 is an LD (Laser Diode) that emits laser light. The hologram element 62 is an element that converts laser light emitted from the light source 61 into rectangular illumination light.
Similar to the first embodiment, the polarization conversion plate 43 diffuses the incident laser light by changing the polarization direction for each region A, and is rotatable about the rotation axis P. Accordingly, when the laser light emitted from the hologram element 62 passes through the polarization conversion plate 43, laser light having a plurality of types of polarization directions is diffused and emitted from a plurality of regions.

The collimating lens 63 converts the diffused laser light emitted from the polarization conversion plate 43 into substantially parallel light and makes it incident on the reflective light valve 64.
The reflective light valve (light modulation device) 64 modulates the parallel laser light emitted from the collimating lens 63 according to the image signal. As the reflective light valve 64, for example, a DMD (Digital Mirror Device) can be used.
The projection device 65 is constituted by a plurality of lenses, and projects the image modulated by the reflective light valve 64 toward the screen 50.

Next, a method for displaying an image on the screen 50 by the projector 60 of the present embodiment having the above configuration will be described.
First, the laser beam emitted from the light source 61 is converted into a rectangular laser beam by the hologram element 62 and enters the polarization conversion plate 43. The polarization direction of the laser light incident on the polarization conversion plate 43 is linearly polarized light. In the polarization conversion plate 43, the laser light whose polarization direction has been converted for each region is diffused into a plurality of types of linearly polarized light or elliptically polarized light having different ellipticities, and enters the reflective light valve 64. Then, images with different polarization directions are projected onto the screen 50 by the projection device 65 for each region reflected by the reflective light valve 64. At this time, the laser light projected on the screen 50 is also laser light having a different polarization direction for each region.

  The projector 60 according to the present embodiment can obtain the same effects as the projector 1 of the first embodiment. Further, in the projector 60 of the present embodiment, the polarization conversion plate 43 is disposed in front of the reflection type light valve 64, so that laser light having a different polarization direction is diffused for each region and enters the reflection type light valve 64. . That is, in this embodiment, since it is not necessary to form an intermediate image as in the first embodiment, it is possible to reduce the size of the entire apparatus.

Note that the hologram element 62 is used as means for illuminating the reflective light valve 64, but the present invention is not limited to this, and any means capable of illuminating the reflective light valve 64 may be used.
Moreover, although DMD was used as a light modulation device, it is not limited to this, and any light modulation device that does not need to pass through a polarizing plate may be used.
In order to project a color image on the screen 50, red, green and blue laser light sources are combined as a light source 61 by a dichroic prism or the like, and are incident on the hologram element 62. At this time, each of the RGB light sources is driven in a time-sharing manner. With this configuration, a color image can be projected onto the screen 50.

[Third Embodiment]
Next, a third embodiment according to the present invention will be described with reference to FIG.
The projector (image display device) 70 according to this embodiment is different from the second embodiment in that the polarization conversion plate 51 and the light diffusion plate 52 are provided separately.

The polarization conversion plate (polarization conversion device) 51 is disposed on the optical path between the hologram element 62 and the parallelizing lens 63 as shown in FIG. The polarization conversion plate 51 is made of polycarbonate, and changes the polarization direction of the laser light emitted from the hologram element 62 for each region. Note that the polarization conversion plate 51 may be disposed on the optical path between the light source 61 and the reflective light valve 64.
A light diffusing plate (light diffusing unit) 52 is disposed on the optical path between the reflective light valve 64 and the projection device 65. The light diffusing plate 52 is, for example, a glass plate having a concavo-convex portion, and diffuses the laser light emitted from the reflective light valve 64 so as to enter the projection device 65. The light diffusing plate 52 is disposed at the intermediate image position of the reflective light valve 64. Further, an intermediate image lens 66 is provided between the reflective light valve 64 and the light diffusion plate 52 in order to form an intermediate image.

  In the projector 70 according to the present embodiment, since the light diffusing plate 52 is provided on the projection device 65 side from the reflective light valve 64, the light valve is illuminated without reducing the proportion of light rays incident on the light valve. It is possible. It is possible to improve so-called illumination efficiency. A light diffusing plate 52 is disposed on the optical path between the light source device 61 and the reflective light valve 64, and a polarization conversion plate 51 is disposed on the optical path between the reflective light valve 64 and the screen 50. Also good.

Further, as a more preferable form, it is preferable that the polarization conversion plate is disposed at the aperture stop or the pupil position of the projection device 65. Specifically, as shown in FIG. 8, on the optical path of the light emitted from the light source 61, a hologram element 62, a light diffusion plate 52 , a collimating lens 63, and the transmission type liquid crystal light shown in the first embodiment. The valve 20 and the projection device 65 are arranged in this order. The projection device 65 includes a first lens group 65a and a second lens group 65b, and an aperture stop 67 is provided between the first lens group 65a and the second lens group 65b. A polarization conversion unit 68 is provided in the opening 67a of the aperture stop 67, and the polarization conversion unit 68 emits the incident laser light with the polarization direction being changed for each region.
As shown in FIG. 9, as in the first embodiment, in the configuration in which the aperture stop 42 is provided between the front lens group 41a and the rear lens group 41b of the first lens group 41, the aperture of the aperture stop 42 is set. A configuration in which the polarization conversion unit 69 is provided in 42a may be employed.
As described above, in the case where the polarization converters 68 and 69 are provided at the position of the aperture stop 42, the relationship between the size of each region A and the size T1 of the opening 42a of the aperture stop 42 is shown in FIG. As described above, the size of one of the plurality of regions A is smaller than the size of the opening 42 a of the aperture stop 42.

Furthermore, in the example shown in FIGS. 7 and 9, the laser light emitted from the light source device 61 is incident on the polarization conversion plates 51 and 69 and the light diffusion plate 52 in this order. Thereby, since the laser light having a different polarization direction is diffused for each region, the laser light having a different polarization direction is superimposed on the screen 50, so that speckle noise can be further reduced.

In the present embodiment, the polarization conversion plate 51 and the light diffusion plate 52 are formed of different materials, but the polarization conversion plate 51 and the light diffusion plate 52 may be formed of the same material.
Further, the laser light emitted from the first lens group 41 may be incident on the polarization conversion plate 51 and the light diffusion plate 52 in this order. The laser light emitted from the first lens group 41 may be incident on the light diffusion plate 52 and the polarization conversion plate 51 in this order.
Further, when a transmissive liquid crystal light valve is used as the light modulation device as in the first embodiment, and the polarization conversion plate 51 and the light diffusion plate 52 are provided separately, the polarization conversion plate 51 is provided in the liquid crystal light valve 20R, The light diffusion plate 52 is disposed on the optical path between the light source device 10 and the liquid crystal light valves 20R, 20G, and 20B. That is, when the light modulation device is the liquid crystal light valve 20R, 20G, or 20B, laser light having a specific polarization direction is incident on the liquid crystal light valve 20R, 20G, or 20B using the polarizing member. Therefore, by arranging the polarization conversion plate 51 on the rear stage side of the liquid crystal light valves 20R, 20G, and 20B, it becomes possible to efficiently project laser beams having different polarization directions on the screen 50 for each region.

[Fourth Embodiment]
Next, a fourth embodiment according to the present invention will be described with reference to FIG.
The projector according to the present embodiment is different from the third embodiment in that it is a diffuser 71 in which the polarization conversion unit 73 and the light diffusion plate 74 are integrally formed. Other configurations are the same as those of the third embodiment.
As shown in FIG. 11, in the diffuser (polarization conversion diffusion member) 71, a polarization conversion portion 73 is formed on one surface 72a of a base material 72 made of polycarbonate, and light is applied to the other surface 72b opposite to the one surface 72a. A diffusion portion 74 is formed. In other words, the polarization conversion unit 73 and the light diffusion unit 74 of the present embodiment are configured integrally with the same material. The laser light is incident from one surface 72 a of the diffuser 71.
The polarization conversion unit 73 includes a recess 72M like the polarization conversion unit 43 of the first embodiment shown in FIG. Thereby, laser beams having a plurality of types of polarization directions are emitted from a plurality of regions A.

  The light diffusing portion 74 forms a light diffusing portion 74 having an arbitrary diffusion pattern by applying a photosensitive material to the other surface 72b of the base material 72 made of polycarbonate and irradiating and interfering with two exposure beams. .

The diffuser 71 of this embodiment can control the generation of diffracted light by the light diffusing unit 74 by using two-beam interference. That is, it is possible to improve the light utilization efficiency by irradiating the two exposure beams and forming the light diffusion portion 74 that does not generate unnecessary high-order diffracted light.
Further, since no interface is generated between the polarization conversion unit 73 and the light diffusion unit 74, the light emitted from the polarization conversion unit 73 and incident on the light diffusion unit 74 is transmitted to the polarization conversion unit 73, the light diffusion unit 74, and the like. No refraction occurs between the two. Therefore, it is possible to prevent the laser light from diffusing beyond the aperture of the second lens group 45 disposed in the subsequent stage.
Although the laser beam is incident from one surface 72a of the base material 72, it may be incident from the other surface 72b.

[Fifth Embodiment]
Next, a fifth embodiment according to the present invention will be described with reference to FIG.
The projector according to the present embodiment is different from the third embodiment in that the polarization conversion unit 77 and the light diffusion unit 78 are a diffuser 75 configured integrally. Other configurations are the same as those of the third embodiment.

As shown in FIG. 12, in the diffuser (polarization conversion diffusion member) 75, a polarization conversion portion 77 is formed on one surface 76a of a substrate 76 made of polycarbonate, and light is applied to the other surface 76b opposite to the one surface 76a. A diffusion portion 78 is formed. That is, the polarization conversion unit 77 and the light diffusing unit 78 of the present embodiment are configured integrally with the same material. Laser light is incident from one surface 76 a of the diffuser 75.
The polarization conversion unit 77 includes a recess 76M like the polarization conversion unit 43 of the first embodiment shown in FIG. Thereby, laser beams having a plurality of types of polarization directions are emitted from a plurality of regions A.
The light diffusing unit 78 is a surface relief type diffraction element having a plurality of grooves 78a in a two-dimensional array.

Since the diffuser 75 of the present embodiment does not generate an interface between the polarization conversion unit 77 and the light diffusion unit 78, similarly to the diffuser 71 of the fourth embodiment, the polarization conversion unit 77 and the light diffusion unit 78 No refraction occurs between them. Therefore, it is possible to prevent the laser light from diffusing beyond the aperture of the second lens group 45 disposed in the subsequent stage.
Further, since the surface relief type diffraction element which is the light diffusion portion 78 is formed on the other surface 76b of the base material 76, the diffusion angle of the laser light diffused in the light diffusion portion 78 is within a predetermined range. Can be. Therefore, it becomes possible to improve the utilization efficiency of laser light.

[Sixth Embodiment]
Next, a sixth embodiment according to the present invention will be described with reference to FIG.
In the projector according to the present embodiment, a method for forming a polarization conversion plate by sandblasting will be described. In the present embodiment, the polarization conversion plate 80 is different in the size of the region A.
As shown in FIG. 13, the polarization conversion plate (polarization conversion device) 80 has a plurality of recesses 81a formed in a base material 81 made of polycarbonate. When the thickness of the substrate 81 is t, t> λ / (2 · Δn), and a phase difference of λ / 2 or more can be obtained.
As a method of forming the recess 81a, the maximum difference d in the thickness of the adjacent region A is a phase difference of λ / 2, that is, d (max) = Re (max) / Δn = λ / (2 · Δn). Then, the surface is processed by a sandblasting process in which a sandblasting medium 82 is sprayed on the surface 81 b of the base material 81.
Thus, by forming the polarization conversion plate 80 by sandblasting, the recess 81a can be formed in the base material 81 by a simple method.

[Seventh Embodiment]
Next, a seventh embodiment according to the present invention will be described with reference to FIG.
In the projector according to the present embodiment, a method for forming a polarization conversion plate by photolithography and etching will be described. In the present embodiment, the polarization conversion plate 90 has a different area A size.
As shown in FIG. 14, the polarization conversion plate (polarization conversion device) 90 has a plurality of recesses 91a formed in a base material 91 made of polycarbonate. When the thickness of the substrate 91 is t, t> λ / (2 · Δn), and a phase difference of λ / 2 or more can be obtained.
As a method for forming the recess 91a, the maximum difference d in the thickness of the adjacent region A is a phase difference of λ / 2, that is, d (max) = Re (max) / Δn = λ / (2 · Δn). The mask 92 having a different aperture ratio (size of the opening portion 93) and transmittance (ratio of light rays that pass through the opening portion 93) for each region A is used for the surface 91b of the base material 91. And a resist is apply | coated to the surface 91b of the base material 91, a light ray is irradiated from the surface 92b opposite to the surface 92a of the mask 92 facing the base material 91, and a resist is patterned. Thereafter, the recess 91a is formed by performing an etching process.

In the present embodiment, by changing the size and transmittance of the opening 93 of the mask 92, the recess 91a having a desired depth can be formed. That is, the base material 91 can be processed as designed as compared with the sandblasting process of the sixth embodiment. Furthermore, by changing the size and transmittance of the opening 93 of the mask 92, the pattern of the recess 91a can be formed in a more complicated manner.
Further, the etching method may be dry etching or wet etching. Further, since the resist residual film amount can be freely changed by using a transmittance modulation mask (including area gradation), the etching depth can be freely changed. That is, the polarization conversion plate 90 can be easily adjusted to a desired phase difference.
Further, the mask 92 used for patterning the recess 91a may be directly processed using a metal mask.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, although the dichroic prism is used as the color light combining means, the present invention is not limited to this. As the color light synthesizing means, for example, a dichroic mirror having a cross arrangement to synthesize color light, or a dichroic mirror arranged in parallel to synthesize color light can be used.
Further, the polarization conversion unit used in the illumination device, for example, a laser processing machine or a laser exposure machine, is not limited to the polarization conversion unit of the first embodiment, and any of the polarization conversion unit and the light diffusion unit of the second to seventh embodiments. May be used.
Further, for example, the above-described implementation is applied to a so-called slide projector that does not include a liquid crystal light valve and illuminates the surface of a slide (positive film) including image information with a lighting device and projects light including image information on a screen. It is also possible to apply a lighting device of the form.

  T ... Intermediate image 1, 60, 70 ... Projector (image display device), 10 ... Light source device (laser light source), 20 ... Liquid crystal light valve (light modulation device), 40, 65 ... Projection device (projection means), 43 , 51, 80, 90... Polarization conversion plate (polarization conversion device), 43M, 72M, 76M, 81a, 91a... Concave portion, 50... Screen (projected surface), 52 .. light diffusion plate (light diffusion portion), 64. Reflection type light valve (reflection type light modulation device), 72, 76, 81, 91... Base material, 73, 77... Polarization conversion unit, 74, 78 ... light diffusion unit, 75 ... diffuser (polarization conversion diffusion member).

Claims (3)

An image display device for irradiating a projection surface,
A laser light source for emitting laser light;
A first region in which the polarization direction of the incident laser light is converted into the first polarization direction and emitted; a second region in which the polarization direction of the incident laser light is converted into the second polarization direction and emitted; A polarization conversion device disposed downstream of the laser light source,
A light modulation device that is arranged downstream of the laser light source and modulates incident laser light in accordance with an image signal;
A projection unit disposed at a subsequent stage of the light modulation device and projecting incident laser light onto the projection surface;
A light diffusing unit provided at a subsequent stage of the polarization conversion device ,
The polarization converter is disposed at the aperture stop or pupil position of the projection means;
The light diffusing unit is disposed at an intermediate image position of the light modulation device;
An image display device characterized in that after the polarization direction of laser light emitted from the light source is converted for each region by the polarization conversion device, the converted laser light is diffused by the light diffusion unit .   The image display apparatus according to claim 1, wherein the first area and the second area are smaller in size than an aperture stop of the projection unit.   The image display device according to claim 1, wherein the polarization conversion device is rotated or rocked.

Images