JP2004271965A - Illuminator, and projection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illuminator capable of generating uniform polarized light with high polarized light changing efficiency by a simple optical system. <P>SOLUTION: A concave reflection mirror 21b and a rod integrator 21d thoroughly make illuminating light emitted from a light source 21a incident on a polarized light changing element 21e, and also make returning reflected light LR which is not changed to P polarized light by the element 21e incident on the element 21e again in a state where the light is superposed while it is divided in terms of wave surface with low loss. Since a scattering member 21g properly scatters the light made incident on the element 21e or reflected by the element 21e, the uniformity of the illumination of the element 21e is enhanced. That means, the uniformity of the intensity distribution and the emitting angle of the illuminating light emitted from the element 21e is enhanced to realize uniform and efficient illumination for a liquid crystal light valve or the like. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an illumination device for illuminating a liquid crystal display element and other spatial light modulation devices, and a projection device that projects an image using the spatial light modulation device and the illumination device.
[0002]
[Prior art]
2. Related Art As a lighting device for a liquid crystal projector, there is known a lighting device that emits illumination light from a lamp light source into desired linearly polarized light using a grid-type polarizer (for example, see Patent Document 1). In this illumination device, the reflected light of the S-polarized light from the polarizer provided on the emission side is returned to the light source side, reciprocates with the light source side, and reenters the polarizer on the emission side. At this time, since the quarter-wave plate is disposed so as to face the polarizer, the reflected light from the polarizer passes twice through the quarter-wave plate, and It is converted to P-polarized light and almost passes through the polarizer. In such an illuminating device, the polarization conversion efficiency of the illuminating light can be enhanced by the presence of the quarter-wave plate.
[0003]
[Patent Document 1]
JP-A-11-6989 [Problems to be Solved by the Invention]
However, in the above-described lighting device, it is necessary to precisely arrange the light source and the reflecting mirror, which leads to a complicated structure of the light source and an increase in cost. Further, in such a lighting device, the light from the light source cannot be sufficiently uniformized. In particular, when an LED or the like is used as a light source, bias is likely to occur in the radiation angle distribution, and it is not easy to form uniform illumination light.
[0004]
Therefore, an object of the present invention is to provide an illumination device that can generate uniform polarized light with high polarization conversion efficiency by a simple optical system.
[0005]
Another object of the present invention is to provide a projection device that can easily, efficiently and uniformly illuminate and project a high-quality image by incorporating such a lighting device.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, a lighting device according to the present invention includes a light source that generates illumination light, and reflects a part of the illumination light from the light source, transmits the remaining light, and converts the light into polarized light in a specific direction. A polarization conversion element, a scattering member provided on the incident surface side of the polarization conversion element to scatter the passing light, and a light returning the illumination light reflected by the polarization conversion element to the polarization conversion element again via the scattering member. Return means.
[0007]
In the above illumination device, since the scattering member provided on the incident surface side of the polarization conversion element scatters light passing therethrough, the light reflected by the polarization conversion element is incident on the polarization conversion element again by the light feedback means. During this time, the uniformity of the illumination light can be improved. Therefore, the uniformity of the intensity distribution and the exit angle of the illumination light emitted from the polarization conversion element is enhanced, and uniform and efficient illumination of a liquid crystal light valve or the like to be illuminated becomes possible.
[0008]
In a specific embodiment of the illumination device, the polarization conversion element is a grid-type polarizer in which conductive lines are formed in a stripe shape on a transparent substrate. In this case, the grid-type polarizer having a simple structure and durability and having relatively moderate incident angle conditions enables stable polarization, so that the illumination light emitted from the polarization conversion element can be stabilized for a long time. Can be done.
[0009]
In another specific aspect of the lighting device, the scattering member has a surface uneven pattern formed on the back surface of the transparent substrate. In this case, the processing of the scattering member is simple, and the manufacture of the lighting device is simplified as compared with the case where the scattering members are individually provided.
[0010]
In another specific aspect of the lighting device, the surface uneven pattern is an aggregate including at least one of a lens-shaped protrusion and a recess. In this case, a desired scattering state can be easily realized by adjusting the arrangement and shape of the lens-shaped projections or recesses, and the controllability of illumination of the liquid crystal light valve and the like can be improved.
[0011]
In another specific aspect of the lighting device, the surface uneven pattern is an aggregate including at least one of a cone-shaped protrusion and a concave portion. In this case, a desired scattering state can be easily realized by adjusting the arrangement and the shape of the conical protrusions or recesses, and the controllability of illumination of the liquid crystal light valve or the like can be improved.
[0012]
In another specific mode of the above-mentioned lighting device, a wavelength plate for changing a polarization state of light reflected from the polarization conversion element is further provided between the polarization conversion element and the light feedback unit. In this case, when the light reflected by the polarization conversion element is returned to the polarization conversion element by the light feedback means, the light can be converted into polarized light that efficiently transmits through the polarization conversion element. Efficient extraction is possible.
[0013]
In another specific aspect of the illumination device, the light feedback unit is a concave reflecting mirror that collects illumination light emitted from the light source. In this case, since the reflected light from the polarization conversion element is returned to the polarization conversion element again while condensing the illumination light, the distribution of the emission angle of the illumination light and the like can be aligned within a certain range.
[0014]
In another specific aspect of the illumination device, the illumination device further includes an optical integrator that causes the illumination light from the light source to be split into wavefronts and superimposed and incident on the polarization conversion element via the scattering member. In this case, since the light from the light source is divided into wavefronts and superimposed by the optical integrator, the uniformity of the intensity distribution and the distribution of the emission angle of the illumination light emitted from the device can be improved.
[0015]
Further, the first projection device according to the present invention includes the illumination device described above, a spatial light modulation device that is illuminated by illumination light from the illumination device, and a projection optical system that projects image light from the spatial light modulation device. Is provided. Here, the "spatial light modulator" is an optical device represented by, for example, a liquid crystal light valve.
[0016]
In the first projection device, since the spatial light modulator is illuminated using the above-described illumination device, uniform polarized light can be efficiently generated, and a high-quality image can be projected by an inexpensive device. it can.
[0017]
In addition, a second projection device according to the present invention includes a plurality of image forming units for each color, each including the above-described illumination device and a spatial light modulation device illuminated by illumination light from the illumination device, and a plurality of images. A light combining member that combines and emits the image light from the forming unit, and a projection optical system that projects the image light combined through the light combining member.
[0018]
In the second projection device, since the spatial light modulator is illuminated using the above-described illumination device, uniform polarized light can be efficiently generated for each color, and a high-quality color image can be obtained by an inexpensive device. Can be projected.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
FIG. 1 is a block diagram conceptually illustrating the structure of the projection device according to the first embodiment. The projection device, that is, the projector 10 includes an illumination device 20, a light modulation device 30, a projection lens 40, and a control device 50. Here, the lighting device 20 includes an R light lighting device 21, a G light lighting device 23, a B light lighting device 25, and a light source driving device 27. The light modulator 30 outputs drive signals to the three liquid crystal light valves 31, 33, and 35 that are spatial light modulators, the cross dichroic prism 37 that is a photosynthetic member, and the liquid crystal light valves 31, 33 and 35. And an element driving device 38 that performs the operation. The R light illumination device 21 and the liquid crystal light valve 31 are referred to as an image forming unit as a set. Similarly, the unit of the G light illumination device 23 and the liquid crystal light valve 33 and the unit of the B light illumination device 25 and the liquid crystal light valve 35 are also called image forming units.
[0020]
FIG. 2 is a diagram illustrating the structure of the R light illumination device 21 of the illumination device 20. The R light illuminating device 21 includes a light source 21a that generates R light of the three primary colors, a concave reflecting mirror 21b that collects illumination light emitted from the light source 21a to the side, and fixed to an opening of the concave reflecting mirror 21b. (Λ / 4) plate 21c which is the divided wavelength plate, a rod integrator 21d fixed in a state of facing the concave reflecting mirror 21b with the (λ / 4) plate 21c interposed therebetween, and an emission end of the rod integrator 21d. And a polarization conversion element 21e connected thereto. Among them, the concave reflecting mirror 21b functions as a light feedback unit that returns the reflected light from the polarization conversion element 21e to the polarization conversion element 21e again, and the rod integrator 21d splits and mixes the illumination light from the light source 21a. -Functions as an integrator.
[0021]
Here, the light source 21a is an LED package also called a solid-state light source, and incorporates a light emitting unit, that is, a diode chip PC. The light beam LF emitted from the diode chip PC while diverging in the front direction is converted into a light beam having a certain spread by the lens portion LP of the light source 21a, and is incident on the rod integrator 21d via the (λ / 4) plate 21c. Light enters from end IP. The light beam LS emitted from the diode chip PC while diverging in the side direction is also converted into a light beam having a certain spread by the concave reflecting mirror 21b, and enters the rod integrator 21d via the (λ / 4) plate 21c. I do.
[0022]
The rod integrator 21d has a structure in which a quadrangular prism-shaped cylindrical inner surface is formed on a reflecting surface, and divides the illumination light incident from the incident end IP into a wavefront by internal reflection according to the angle, and is thus divided into wavefronts. The illuminating light is superimposedly synthesized and is incident on the emission end EP from inside. Thus, illumination light having a uniform distribution can be emitted from the emission end EP with a relatively uniform angular distribution within a desired angle range. At this time, the size of the opening AP of the concave reflecting mirror 21b and the size of the incident end IP of the rod integrator 21d are matched, and reflection surfaces (not shown) functioning as auxiliary light feedback means are provided at the four corners of the incident end IP. Since it is formed, the illumination light emitted from the diode chip PC can be coupled to the rod integrator 21d without leakage, and the return reflected light LR returned from the polarization conversion element 21e is reflected by the rod integrator 21d and the concave reflecting mirror 21b. (Λ / 4) Leakage to the outside at the joint with the plate 21c can be reliably prevented.
[0023]
The polarization conversion element 21e is formed of a grid polarizer that is a type of a reflective polarizer that reflects light that has not been polarized without absorbing it. The polarization conversion element 21e has a stripe conductive line SC made of a conductor pattern of equal width formed at equal intervals and also called a wire grid on the surface of the transparent substrate TP. Since the width and interval of the stripe conductor SC are set to be equal to or less than the wavelength of the R light, of the light incident on the polarization conversion element 21e, polarized light perpendicular to a specific direction in which the stripe conductor SC extends (hereinafter referred to as P for convenience). Only polarized light) selectively passes through the polarization conversion element 21e.
[0024]
On the incident surface side of the polarization conversion element 21e, that is, on the back surface side of the transparent substrate TP, a scattering member 21g in which lens-shaped minute protrusions PP are randomly arranged at an appropriate density is formed. The scattering member 21g is for scattering light passing through the scattering member 21g in random directions. Therefore, the light passing through the scattering member 21g and entering the polarization conversion element 21e has a relatively uniform angular distribution within a certain incident angle range. Also, light that passes through the scattering member 21g in the opposite direction and enters the rod integrator 21d also has a relatively uniform angular distribution within a certain incident angle range, and when the light travels backward through the rod integrator 21d, The two-dimensional distribution of the luminance of the illumination light is further uniformed in a plane perpendicular to the axis of 21d. In particular, when a solid-state light source such as an LED is used as the light source 21a, the illuminating light emitted from the solid-state light source often has a fixed pattern. Therefore, by disposing the scattering member 21g in front of the polarization conversion element 21e, the polarization conversion element Illumination light incident on 21e can be effectively uniformized. Since the polarization conversion element 21e is a wire grid polarization element, the allowable range of the incident angle of the illumination light incident on the polarization conversion element 21e is wide. Therefore, according to such a polarization conversion element 21e, even if the illumination light has various angles to some extent, it is possible to extract the P-polarized light in a state where the leakage of the S-polarized light is small and the polarization conversion efficiency is high.
[0025]
The scattering member 21g can be formed, for example, as follows. First, a resist film is applied to the rear surface side of the transparent substrate TP of the polarization conversion element 21e, and an image of a mask having randomly arranged circular shielding portions is projected onto the resist film in a state where the focus is appropriately removed. On the resist film after the development, convex portions randomly arranged corresponding to the arrangement of the circular shielding portions of the mask are formed. By removing the processed resist film by dry etching, convex lens-shaped microprojections PP corresponding to the convex portions of the resist film are formed at random at a desired density.
[0026]
As another method, a glass substrate or a plastic substrate to be a transparent substrate TP is heated to an appropriate softening temperature, and a mold having a transfer surface including a large number of minute concave portions corresponding to the pattern of the minute projections PP is formed on the glass substrate. It is also possible to press a substrate or a plastic substrate and emboss the minute projections PP to be the scattering members 21g on the surface of the substrate. Note that, for example, the stripe conducting wire SC is formed on the front surface side of the transparent substrate TP after the minute projection PP is formed by embossing on the rear surface side. For example, the stripe conducting wire SC is formed by depositing a metal film on the surface side of the transparent substrate TP, forming a stripe pattern of a resist film thereon, and etching the metal film by using such a stripe pattern as a mask to form a large number of thin wires. It is formed by processing.
[0027]
The operation of the R light illumination device 21 shown in FIG. 2 will be described. The light beams LF and LS emitted from the diode chip PC incorporated in the light source 21a while diverging in the front direction and the side direction are narrowed down to an appropriate divergence angle. Then, the light passes through the (λ / 4) plate 21c, goes straight through the rod integrator 21d, or enters the polarization conversion element 21e in a uniform state by being reflected once or more on the inner surface. As a result, the polarization conversion element 21e is almost uniformly illuminated by the illumination light from the light source 21a. Of the light beams LF and LS that have entered the polarization conversion element 21e, those that have passed through the polarization conversion element 21e are almost P-polarized light only. On the other hand, of the illumination light incident on the polarization conversion element 21e, the light reflected by the polarization conversion element 21e substantially consists only of S-polarized light, and such reflected light is disposed at the incident end IP of the rod integrator 21d. The light passes through the (λ / 4) plate 21c and is converted into circularly polarized light. The reflected light in a circularly polarized state that has passed through the (λ / 4) plate 21c is returned to the concave reflecting mirror 21b. The concave reflecting mirror 21b reflects such return reflected light LR from the polarization conversion element 21e one or more times so as to be incident again on the polarization conversion element 21e. At this time, the circularly polarized light reflected by the concave reflecting mirror 21b has its rotation direction reversed but is maintained as circularly polarized light, and passes when re-entering the polarization conversion element 21e via the rod integrator 21d (λ / 4). ) Plate 21c converts circularly polarized light into P-polarized light. As a result, the return reflected light LR re-entering the polarization conversion element 21e efficiently passes through the polarization conversion element 21e. As a result, the illumination light emitted from the light source 21a is almost completely converted into P-polarized light and emitted as output light from the emission side of the polarization conversion element 21e.
[0028]
In this case, the concave reflecting mirror 21b and the rod integrator 21d function as a light confinement container, and the illumination light emitted from the light source 21a is incident on the polarization conversion element 21e without leakage, and is converted into P-polarized light by the polarization conversion element 21e. The returned reflected light LR that has not been superimposed is split into wavefronts with low loss and superimposed, and is incident again on the polarization conversion element 21e. Further, the scattering member 21g appropriately scatters light that enters the polarization conversion element 21e or is reflected by the polarization conversion element 21e, so that the uniformity of illumination of the polarization conversion element 21e can be further improved. That is, the uniformity of the intensity distribution and the emission angle of the illumination light emitted from the polarization conversion element 21e is improved, and uniform and efficient illumination of the liquid crystal light valve 31 is enabled.
[0029]
As is clear from the above description, according to the R light illuminating device 21, the illuminating light emitted from the light source 21a is converted into an extremely uniform and high-luminance P-polarized output light and emitted. As a result, not only can the liquid crystal light valve 31 in the subsequent stage be uniformly illuminated, but also the heat generated by the polarizing plate and the like disposed around the liquid crystal light valve 31 can be reduced.
[0030]
The uniformity of the output light and the range of the incident angle to the liquid crystal light valve 31 can be appropriately adjusted by appropriately adjusting the arrangement of the light source 21a, the focal length of the concave reflecting mirror 21b, the length of the rod integrator 21d, and the like. it can. Also, by appropriately adjusting the radius of curvature and the like of the minute projections PP constituting the scattering member 21g, the incident angle range of the illumination light incident on the polarization conversion element 21e can be appropriately adjusted.
[0031]
In the above description, only the structure of the R light illuminating device 21 of the illuminating device 20 of FIG. 1 has been described. The structure is basically the same as that of the R light illumination device 21 only by being changed.
[0032]
In other words, the liquid crystal light valve 33 for G light is illuminated extremely uniformly by the G light from the G light illuminating device 23. At this time, the illuminating light almost completely illuminates the G light from the LED package which is a solid light source. It is efficiently converted to P-polarized light. The liquid crystal light valve 35 for B light is extremely uniformly illuminated by the B light from the B light illuminating device 25, and the illuminating light at this time almost completely eliminates the B light from the LED package which is a solid light source. It is efficiently converted to P-polarized light.
[0033]
Light from the illumination devices 21, 23, and 25 of the respective colors incident on the liquid crystal light valves 31, 33, and 35 is two-dimensionally modulated by the liquid crystal light valves 31, 33, and 35, respectively. The light of each color having passed through each of the liquid crystal light valves 31, 33, 35 is synthesized by a cross dichroic prism 37, which is a light synthesizing member, and emitted from one side thereof. The image of the combined light emitted from the cross dichroic prism 37 is incident on a projection lens 40 which is a projection optical system, and is projected on a screen (not shown) provided outside the projector 10 at an appropriate magnification. That is, the projector 10 projects a color image obtained by combining the images of the respective colors R, G, and B appropriately formed on the liquid crystal light valves 31, 33, and 35 on the screen. Although not shown, a polarizing plate is disposed at an appropriate position near each of the liquid crystal light valves 31, 33, and 35 to illuminate and read the liquid crystal light valves 31, 33, and 35 with polarized light. ing.
[0034]
The control device 50 includes a microcomputer or the like, and outputs control signals to the light source driving device 27 and the element driving device 38 to operate the light illumination devices 21, 23, 25 of each color and the liquid crystal light valves 31, 33, 35. Is controlled indirectly. Thereby, for example, a color moving image or a still image is projected and displayed on the screen with high luminance in accordance with an image signal input from outside to the projector 10 via the control device 50.
[0035]
[Second embodiment]
Hereinafter, a projector according to the second embodiment will be described. The projector according to the second embodiment is obtained by modifying the illumination devices 21, 23, and 25 of the projector according to the first embodiment.
[0036]
FIG. 3 is a diagram illustrating a part of the R light illumination device incorporated in the projector according to the second embodiment. This R-light illuminating device includes a scattering member 121g on the incident surface side of the polarization conversion element 21e. However, unlike the first embodiment shown in FIG. 2, the conical microprojections PP 'are formed with an appropriate density. They are arranged randomly. Light that passes through the scattering member 121g and enters the polarization conversion element 21e has a relatively uniform incident angle distribution within a desired incident angle range. The light that passes through the scattering member 121g and returns to the rod integrator 21d (see FIG. 2) also has a relatively uniform incident angle distribution within a certain incident angle range. As a result, the uniformity of illumination of the polarization conversion element 21e can be improved, the intensity distribution and the emission angle of the illumination light emitted from the polarization conversion element 21e can be increased, and the uniformity and efficiency of the liquid crystal light valve 31 can be improved. Lighting becomes possible.
[0037]
Although the present invention has been described with reference to the embodiment, the present invention is not limited to the above embodiment. For example, in the first and second embodiments, a grid type polarizer is used as the polarization conversion element 21e, but instead, a polarization conversion element including an array of polarization beam splitters and other reflection type polarizing plates are used. be able to.
[0038]
Further, in the above embodiment, the rod integrator 21d is provided between the concave reflecting mirror 21b and the polarization conversion element 21e, but the rod integrator 21d is omitted and the concave reflection mirror 21b and the polarization conversion element 21e are directly connected. You can also. In this case, the size of the lighting device for each color can be reduced. At this time, the concave reflecting mirror 21b functions as a light confinement container or an optical integrator, and allows the illumination light emitted from the light source 21a to enter the polarization conversion element 21e without leakage, and is converted into P-polarized light by the polarization conversion element 21e. The returned reflected light LR that has not been superimposed is split into wavefronts with low loss and superimposed, and is incident again on the polarization conversion element 21e. In the case where the rod integrator 21d is left, the rod integrator 21d can be shortened while maintaining the uniformity of illumination due to the presence of the scattering members 21g and 121g. Therefore, the illumination device and the projection device can be downsized. it can.
[0039]
In the above embodiment, the output light from the polarization conversion element 21e is directly incident on the liquid crystal light valve 31, but an appropriate relay lens can be inserted between them.
[0040]
In the projector 10 of the above embodiment, the light modulation device 30 is configured by the transmission type liquid crystal light valves 31, 33, and 35, but may be configured by a reflection type liquid crystal element. Further, the liquid crystal light valve can be a light-writing type liquid crystal light valve or the like.
[0041]
Further, in the above embodiment, the light source is configured using the LED, but another solid state light source such as an EL light emitting element and an LD can be used instead of the LED.
[0042]
Further, the scattering member 21g incorporated in the device of the first embodiment may have a lens-shaped minute concave portion, that is, a minute concave surface instead of the lens-shaped minute protrusion PP. The scattering member 121g in the embodiment may also have a conical or pyramidal minute concave portion instead of the conical minute projection PP '. In addition, the scattering member can be formed of an aggregate in which irregularities of various shapes and sizes are mixed. Further, the scattering member can be constituted by a stripe-like pattern in which large and small ridges having a hemispherical cross section or a wedge-shaped cross section are randomly arranged in the short direction.
[0043]
Further, the scattering members 21g and 121g are not limited to the above-described method, and can be manufactured by various methods. For example, by processing the back surface of the transparent substrate TP with a chemical agent or mechanically processing with a polishing material, random minute protrusions can be formed here. Further, it is also possible to separately prepare a scattering plate provided with a large number of random minute projections PP and PP ', and to attach this scattering plate to the back surface of the transparent substrate TP of the polarization conversion element 21e.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a structure of a projector according to a first embodiment.
FIG. 2 is a diagram illustrating a structure of a light illumination device in the device of FIG.
FIG. 3 is a diagram illustrating a second embodiment.
[Explanation of symbols]
10 Projector 20 Illumination device 21 R light illumination device 23 G light illumination device 25 B light illumination device 21a Light source 21b Concave reflector 21c (λ / 4) plate 21d Rod integrator 21e Polarization conversion element 21g Scattering members 31, 33, 35 Liquid crystal light Valve 37 Cross dichroic prism 40 Projection lens 50 Control device PP Micro projection SC Stripe conductor TP Transparent substrate

Claims (10)

A light source for generating illumination light,
A polarization conversion element that reflects a part of the illumination light from the light source, transmits the remaining light, and converts the light into polarized light in a specific direction.
A scattering member that is provided on the incident surface side of the polarization conversion element and scatters passing light,
A light feedback unit that returns the illumination light reflected by the polarization conversion element to the polarization conversion element again via the scattering member. The lighting device according to claim 1, wherein the polarization conversion element is a grid-type polarizer in which conductive lines are formed in a stripe shape on a transparent substrate. The lighting device according to claim 2, wherein the scattering member has a surface uneven pattern formed on a back surface of the transparent substrate. The lighting device according to claim 3, wherein the surface uneven pattern is an aggregate including at least one of a lens-shaped protrusion and a concave portion. The lighting device according to claim 3, wherein the surface uneven pattern is an aggregate including at least one of a cone-shaped protrusion and a concave portion. The wavelength conversion device according to claim 1, further comprising a wavelength plate that changes a polarization state of light reflected from the polarization conversion element, between the polarization conversion element and the light feedback unit. The lighting device according to any one of the preceding claims. The lighting device according to claim 1, wherein the light feedback unit is a concave reflecting mirror that collects illumination light emitted from the light source. 8. The optical integrator according to claim 1, further comprising an optical integrator that causes the illumination light from the light source to be incident on the polarization conversion element via the scattering member in a state where the illumination light is divided into wavefronts and superimposed. The lighting device according to claim 1. The lighting device according to any one of claims 1 to 8,
A spatial light modulator illuminated by illumination light from the illumination device,
A projection optical system for projecting image light from the spatial light modulator. A plurality of image forming units for each color, each including the lighting device according to any one of claims 1 to 8, and a spatial light modulator illuminated by illumination light from the lighting device,
A light combining member that combines and emits image light from the plurality of image forming units,
A projection optical system for projecting image light synthesized through the light synthesizing member.

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