JP2012063564A - Projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a 3D projector which realizes an inexpensive and high quality 3D image with high light use efficiency with one projector.SOLUTION: The projector comprises: a light source; an illumination optical system 11 for condensing light emitted from the light source and guiding the light to a specific direction; a TIR prism 12 for making illumination light and projection light incoming and outgoing; and a polarization separation prism 13 which separates incident light into two polarized light whose polarization directions are orthogonal to each other and guides the polarized light to two DMDs 14 and 15. Images for a right eye and a left eye generated by reflecting at the two DMDs respectively are polarization-synthesized by passing through the polarization separation prism 13 again, and the synthesized image is made outgoing from one projection lens, to obtain a 3D image.

Description

  The present invention relates to a 3D projector capable of realizing a 3D image with one projector and polarized glasses.

  The following two methods are often used as means for realizing 3D video with a projector. One is a method using active shutter glasses, and the other is a method using polarized glasses.

  The method using the active shutter glasses can realize 3D with one projector. That is, 3D images can be realized by alternately displaying right-eye and left-eye images from the projector, and turning on / off the left and right of the active shutter glasses at the same timing. Although this method does not require a special optical system, a high-speed response is required for the display device. A DMD device is an example of a display device capable of high-speed response.

  On the other hand, since the DMD device is a time-axis modulated display device, there is a demerit that gradation representation is halved if the left and right images are divided on the time axis. Active shutter glasses are relatively expensive and are not very suitable for viewing with a large number of people.

  As a method of using polarized glasses, it is common to use two projectors. 3D images can be realized by projecting projection lights having different polarization axes onto the screen and overlaying the images. However, it is necessary to adjust the image alignment between the two projectors and adjust the brightness. In addition, since the image alignment adjustment is required again when the screen position is moved, it is difficult to use unless the projector and the screen can be installed permanently. Since the polarized glasses themselves are relatively inexpensive, they can be said to be suitable for viewing by a large number of people.

  Therefore, in order to facilitate 3D viewing with a large number of people, a method for realizing 3D with polarized glasses and one projector is desired. As means for realizing 3D with polarized glasses and one projector, for example, the following techniques are known.

  In Patent Document 1 (FIG. 8), a white light source 81, a color selection filter 82 (color wheel), a polarization separation means 83 (wire grid), two total reflection prisms 84 and 85 (TIR prism), and two A 3D projector having spatial light modulators 86 and 87 (DMD), polarization combining means 88 (polarization beam splitter), and projection means 89 (projection lens) is disclosed.

  In Patent Document 2 (FIG. 9), a light source 91, a color separation rotation filter 92 (color wheel), a first polarization separation element 93, an optical path selection rotation filter 94, a second polarization separation element 95, and a beam separation element. A 3D projector comprising 96 (TIR prism), a DMD element 97, and a projection lens 98 is disclosed.

JP 2004-205919 A JP 2007-17536 A

  In order to view 3D images with a large number of projectors, a method using polarized glasses, which is relatively inexpensive, is desired. However, in the method using two projectors, left and right image alignment adjustment and luminance adjustment adjustment are performed. Maintenance work is significantly reduced.

  In the configuration of Patent Document 1, 3D video can be realized by one projector, but two polarization separation means, two TIR prisms, and two DMDs are necessary, which is expensive and complicated in configuration. . Furthermore, since the incident directions of light to the two DMDs are different, two types of DMDs are necessary. For example, if the incident direction of the light to the first DMD is from the lower right direction, the incident direction of the light to the second DMD is the lower left direction. That is, it is necessary to prepare two DMDs having a mirror-symmetric pixel structure, which may be a bottleneck to realization.

  In the configuration of Patent Document 2, there is one DMD to be used and there is a cost advantage. However, since the optical path selection rotation filter is used, light on the optical path side that is not used is impaired. Half of the light is lost by simple calculation, so it is difficult to ensure brightness.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a projector excellent in maintainability for realizing 3D video with low cost and high light utilization efficiency with a single projector.

  The 3D projector according to the present invention includes a light source, an illumination optical system that guides light emitted from the light source in a specific direction, a TIR prism that inputs and emits illumination light from the illumination optical system, and illumination emitted from the TIR prism. A polarization separation prism that makes light incident, divides the illumination light into first linearly polarized light and second linearly polarized light whose polarization directions are orthogonal to each other, and emits the light from different positions; and the first linearly polarized light and the second linearly polarized light The third linearly polarized light and the fourth straight line obtained by modulating the two linearly polarized light respectively based on the input image information for the right eye and the left eye, which are located at the reflection position of the linearly polarized light. Two DMD elements that reflect polarized light into the polarization separating prism and the third linearly polarized light and the fourth linearly polarized light are combined as projection light by the polarization separating prism and output to the TIR prism. The emitted separately from the illumination light the projection light by TIR prism, and comprising the projection lens for projecting the projection light emitted by the TIR prism.

  According to the present invention, since a basic optical configuration for 3D display is completed with one TIR prism, one polarization separation prism, and two DMDs, a projector capable of 3D display easily at low cost can be provided. .

  It is possible to separate the illumination light into two polarization components orthogonal to each other with one polarization separation prism and to synthesize two polarizations for right eye and left eye modulated by each DMD. The illumination light and the projection light can be separated by one TIR prism.

  A wire grid can be used for the polarization separation surface of the polarization separation prism. The wire grid is formed by arranging fine metal slits on a glass substrate, and can transmit either the P-polarized component or the S-polarized component of the incident light and reflect the other. Further, it generally has polarization separation performance in a wider incident angle range than a polarizing beam splitter formed of a multilayer film.

  As an illumination optical system, color display is possible by combining a white light source and a color wheel. The color wheel is a rotating filter on a disk in which color filters including three primary colors of red, green, and blue, and in some cases, white and intermediate colors are formed at predetermined angles.

  As another illumination optical system, color display is possible by switching red, green, and blue monochromatic light sources such as LED light sources and laser light sources in order of colors.

  The DMD performs optical modulation of an image corresponding to each color switched in a time division manner. By switching the video of each color at high speed, it is recognized as a color video by the human eye due to the afterimage phenomenon. By using two DMDs and simultaneously projecting them as right-eye and left-eye images, a 3D image is displayed.

  If the number of reflections in the polarization splitting prism until the illumination light for the right eye and the left eye reaches the DMD is even or odd, the direction of the incident light on the DMD is for the right eye and the left eye. Therefore, DMDs of the same specification can be used. In addition, since the illumination distribution is not reversed for the right eye and the left eye, a uniform and high-quality 3D image can be obtained within the screen.

  The polarization separation prism may be designed so that the optical path lengths of the illumination light for the right eye and the left eye are the same. Since there is no optical path length difference between the right eye and the left eye, a uniform and high-quality 3D image can be obtained within the screen.

  In 3D video, video information on one eye may be mixed into both eyes, causing crosstalk that causes a reduction in 3D quality. In order to suppress crosstalk, a polarizing element may be installed in the middle of the optical path between the DMD and the polarization separation prism. Although the brightness decreases, crosstalk can be suppressed by increasing the polarization performance.

  An ND filter may be installed in the middle of the optical path between the DMD and the polarization separation prism. In the process of polarization separation / combination, the output may be biased between S-polarized light and P-polarized light. By correcting this with an ND filter, it is possible to suppress the occurrence of a luminance difference between the left-eye and right-eye images. I can do it.

  It is preferable to install a device for switching the aperture of the illumination optical system when displaying 3D video and when displaying 2D video. In the process of separating and synthesizing the polarized light, it is easier to improve the polarization performance if the light beam is collimated as much as possible. The beam is collimated more by deepening the aperture. When the aperture is deepened during 3D display, the brightness is reduced, but crosstalk can be suppressed, so that a high-quality 3D image can be obtained.

  According to the present invention, it is possible to provide a projector that is inexpensive, has high light utilization efficiency, and can achieve high-quality 3D images with a single projector, and that is excellent in maintainability.

The block diagram which shows 1st Embodiment of the 3D projector of this invention Configuration diagram of a polarization splitting prism used in the first embodiment of the present invention Configuration diagram of a polarization splitting prism used in the first embodiment of the present invention Configuration diagram of a polarization splitting prism used in the first embodiment of the present invention The block diagram which shows 2nd Embodiment of the 3D projector of this invention. The block diagram which shows 3rd Embodiment of the 3D projector of this invention. The block diagram which shows 4th Embodiment of the 3D projector of this invention. Configuration diagram of a conventional 3D projector Configuration diagram of a conventional 3D projector

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a configuration diagram showing a first embodiment of a 3D projector of the present invention. An illumination optical system 11 that generates illumination light of three primary colors in a time-division manner, a TIR prism 12 that inputs and outputs illumination light, a polarization separation prism 13 that simultaneously performs polarization separation and synthesis, and two DMDs (right-eye video) The DMD 14 to be generated, the DMD 15 to generate the image for the left eye), and the projection lens 16.

  The illumination optical system 11 includes a lamp 17, a concave mirror 18, an aspheric lens 19, a rod integrator 20, a color wheel 21, and a relay optical system 22.

  As the lamp 17, a high-pressure mercury lamp, a metal halide lamp, a xenon lamp, or the like can be used.

  The concave mirror 18 and the aspherical lens 19 are used for efficiently condensing the light emitted from the lamp 17 onto the rod integrator incident surface 23.

  The light incident on the rod integrator 20 repeats total reflection within the medium, and is emitted with a uniform illuminance distribution on the rod integrator exit surface 24.

  The relay optical system 22 irradiates the DMDs 14 and 15 with enlargement while maintaining the illuminance distribution on the exit surface of the rod integrator. The relay optical system is provided with an aperture 25 so that the aperture amount can be varied as required.

  The color wheel 21 is composed of red, green, and blue color filters, and is a rotary filter arranged in a disk shape at a predetermined angle. By rotating the color wheel at a predetermined number of rotations, it is possible to generate illumination light of three primary colors in a time division manner. The color wheel 21 is preferably installed in the vicinity of the rod integrator incident surface 23 or in the vicinity of the emission surface 24.

  The TIR prism 12 guides the illumination light 30 emitted from the relay optical system 22 to the DMDs 14 and 15 and guides the projection light 32 including the image information generated by the DMDs 14 and 15 to the projection lens 16.

  The polarization separation prism 13 has a PBS surface 43 and divides the illumination light 31 emitted from the TIR prism 12 into two linearly polarized light (S-polarized component 33 and P-polarized component 34) whose polarization directions are orthogonal to each other. Two orthogonally polarized light beams (S-polarized light component 35 and P-polarized light component 36) that are guided to the right-eye DMD 14 and the left-eye DMD 15 and reflected by the respective DMDs are again combined into one, and the TIR prism 12 is used as projection light. , It plays a role of guiding to the projection lens 16.

  In this configuration, the optical path lengths of the illumination light for the right eye and the left eye are the same, and the optical path length of the projection light is the same. Since there is no difference in optical path length between the right eye and the left eye, a uniform image can be obtained within the screen.

  Unless otherwise specified in the present invention, illumination light means a light beam from the light source until it reaches the DMD, and projection light means a light beam modulated by the DMD until it reaches the screen.

  The image projected from the projection lens includes a left-eye image and a right-eye image at the same time, and since the polarization axis directions are different, a 3D image can be realized through polarized glasses.

  FIG. 2 is a configuration diagram (Example 1) of the polarization separation prism used in the first embodiment of the present invention.

  The polarization separation prism 13a is configured by bonding a first prism 40a, a second prism 41a, and a flat wire grid 42a.

  The wire grid 42a is held by forming an air gap of several μm to several tens μm with the PBS surface 43a facing the first prism 40a. The reason for forming the air gap is that the polarization separation performance is impaired when the wire grid surfaces are joined with an adhesive. The back side 44a of the wire grid 42a and the second prism 41a can be joined with an optical adhesive.

  The wire grid can transmit one of the P-polarized component and the S-polarized component and reflect the other of the incident light. Which is reflected depends on the direction of the grid formed on the PBS surface. In the present invention, the S-polarized light component is arranged to be reflected, the right-eye DMD is described as the S-polarization side, and the left-eye DMD is described as the P-polarization side, but the actual configuration may be either.

  The illumination light 31 emitted from the TIR prism enters the polarization separation prism 13a, and is separated into the S polarization component 33a and the P polarization component 34a by the PBS surface 43a. The S-polarized component 33a reflected by the PBS surface 43a is totally reflected once in the first prism 40a, then emitted from the first prism 40a, and guided to the DMD 14 for the right eye. The S-polarized component 35a including the image information reflected by the right-eye DMD 14 is emitted to the TIR prism side along the path opposite to the illumination light through the polarization separation prism 13a (light ray 32).

  The P-polarized component 34a transmitted through the PBS surface 43a passes through the second prism 41a and is guided to the DMD 15 for the left eye. The P-polarized component 36a including the image information reflected by the left-eye DMD 15 is emitted to the TIR prism side along the path opposite to the illumination light through the polarization separation prism 13a (light ray 32).

  The total number of reflections of the illumination light in the polarization splitting prism until reaching the DMD is 2 for the right eye and 0 for the left eye, and is even. By aligning even-numbered times or odd-numbered times, the direction of light incident on the DMD is the same for the right eye and for the left eye, so the DMD of the same specification can be used. Also, since the illuminance distribution is not reversed for the right eye and the left eye, a uniform and high-quality 3D image can be obtained within the screen.

  FIG. 3 is a configuration diagram (example 2) of the polarization separation prism used in the first embodiment of the present invention.

  The polarization separation prism 13b is configured by bonding a first prism 40b, a second prism 41b, and a flat wire grid 42b.

  The illumination light 31 emitted from the TIR prism enters the polarization separation prism 13b, and is separated into the S polarization component 33b and the P polarization component 34b by the PBS surface 43b. The S-polarized component 33b reflected by the PBS surface 43b is emitted from the first prism 40b and guided to the DMD 14 for the right eye. The S-polarized component 35b including the image information reflected by the right-eye DMD 14 is emitted to the TIR prism side along the path opposite to the illumination light in the polarization separation prism (light ray 32).

  The P-polarized light component 34b transmitted through the PBS surface is reflected once by the reflecting surface 45 on which the reflecting coating of the second prism 41b is applied, and is guided to the DMD 15 for the left eye. The P-polarized light component 36b including the image information reflected by the left-eye DMD 15 is emitted to the TIR prism side along the path opposite to the illumination light in the polarization separation prism (light ray 32).

  The total number of reflections of the illumination light in the polarization splitting prism until reaching the DMD is 1 for the right eye and 1 for the left eye, and the odd number of times.

  FIG. 4 is a configuration diagram (example 3) of the polarization splitting prism used in the first embodiment of the present invention.

  The polarization separation prism 13c is configured by bonding a first prism 40c, a second prism 41c, and a flat wire grid 42c.

  The illumination light 31 incident on the polarization separation prism 13c is separated into an S-polarized component 33c and a P-polarized component 34c on the PBS surface 43c. The S-polarized component 33c reflected by the PBS surface 43c is reflected once by the reflection surface 46 on which the reflection coating of the first prism 40c is applied, and is guided to the DMD 14 for the right eye. The right-eye DMD 14 reflects the S-polarized component 35c including image information, and the light is emitted to the TIR prism side along the path opposite to the illumination light through the polarization separation prism 13c (light ray 32).

  The P-polarized component 34c transmitted through the PBS surface 43c passes through the second prism 41c and is guided to the left-eye DMD 15. The left-eye DMD 15 reflects the P-polarized light component 36c including image information, and the light is emitted to the TIR prism side along the path opposite to the illumination light through the polarization separation prism 13c (light ray 32).

  The total number of reflections of the illumination light in the polarization separation prism until reaching the DMD of the polarization separation prism 13c is 2 times for the right eye and 0 times for the left eye, and is aligned even times.

  In the description of FIGS. 2, 3, and 4, the PBS surface side of the wire grid is the first prism side, but the PBS surface side may be directed to the second prism side. However, the air gap is still required on the PBS surface side. In this example, a flat wire grid is attached, but an integrated type in which the wire grid is directly formed on the first prism surface or the second prism surface may be used.

  2, 3, and 4, the configuration of FIG. 2 is the configuration in which the back focus of the projection lens is the shortest, and the design of the projection lens is relatively easy.

  3 and 4, the polarization separation plane is a 45 ° plane, and the component layout is relatively easy. Even with a multi-layer type PBS coat, the polarization angle can be easily separated, so the first prism or comb forms a multi-layer PBS coat directly on the second prism without using a wire grid, and attaches both. A combined configuration may be used.

(Embodiment 2)
FIG. 5 is a block diagram showing a second embodiment of the 3D projector of the present invention. The basic configuration of the illumination optical system is the same as in FIG.

  The illumination light 31 emitted from the TIR prism 12 enters the polarization separation prism 13 and is separated into two polarization components by the PBS surface 43. The S-polarized light component 33 reflected from the PBS surface 43 is totally reflected once in the first prism 40 and then emitted from the first prism 40. A polarizing plate 60 that transmits the S-polarized component is attached to the exit surface of the first prism 40, and the degree of polarization of the S-polarized light is increased. The S-polarized light component emitted from the polarizing plate is guided to the right-eye DMD 14. The S-polarized light component including the image information reflected by the right-eye DMD 14 passes through the polarizing plate 60 again, and then is emitted to the TIR prism 12 side through the polarization separation prism 13 along the reverse path to the illumination light.

  Similarly, the P-polarized component 34 transmitted through the PBS surface 43 is emitted from the second prism 41. A polarizing plate 61 that transmits a P-polarized component is attached to the exit surface of the second prism, and the degree of polarization of P-polarized light is increased. The P-polarized light component emitted from the polarizing plate 61 is guided to the left-eye DMD 15. The P-polarized component including the image information reflected by the left-eye DMD 15 passes through the polarizing plate 61 again, and then exits the polarization separation prism 13 to the TIR prism 12 side along a path opposite to the illumination light.

  The projection light emitted from the TIR prism 12 is projected onto the screen through the projection lens 16. Since projection light with a high degree of polarization can be obtained, a 3D image with little crosstalk can be obtained.

(Embodiment 3)
FIG. 6 is a block diagram showing a third embodiment of the 3D projector of the present invention. The basic configuration of the illumination optical system is the same as in FIG.

  The illumination light 31 emitted from the TIR prism 12 enters the polarization separation prism 13 and is separated into two polarization components by the PBS surface 43. The S-polarized light component 33 reflected from the PBS surface 43 is totally reflected once in the first prism 40 and then emitted from the first prism 40. The S-polarized component including the image information reflected by the right-eye DMD 14 is emitted to the TIR prism side through the reverse path of the illumination light in the polarization separation prism.

  The P-polarized component 34 reflected by the PBS surface 43 is emitted from the second prism 41. The P-polarized component including image information reflected by the left-eye DMD 15 is emitted to the TIR prism 12 side through the polarization separating prism 13 along a path opposite to that of the illumination light.

  Here, the output ratio of the S-polarized light and the P-polarized light is ideally 1: 1, but there is a case where the output is biased between the S-polarized light and the P-polarized light in the process of polarization separation / combination. is there. In order to correct this deviation, an ND filter for adjusting the light quantity of either one of the polarizations is arranged. The ND filter can be disposed between the polarization separation prism 13 and the DMDs 14 and 15. In this example, the ND filter 62 is inserted between the second prism 41 and the left-eye DMD 15.

  Here, when the ND filter 62 is inserted, there is a difference in the optical path length between the left and right, and thus the AR-coated glass 63 having the same thickness as the ND filter is inserted between the first prism 40 and the right-eye DMD 14. Of course, the right and left optical path lengths may be aligned by adjusting the position of the DMD without using the AR-coated glass 63.

  As a result, it is possible to obtain a good 3D image in which there is no luminance difference between the left and right image information.

(Embodiment 4)
FIG. 7 is a configuration diagram showing a fourth embodiment of the 3D projector of the present invention.

  An illumination optical system 11 that generates illumination light of three primary colors in a time-sharing manner includes light sources 71, 72, and 73 that emit red, green, and blue light, a condensing lens 74, dichroic filters 75 and 76, and a rod, respectively. It is characterized by comprising an integrator 20 and a relay optical system 22.

  As the light sources 71 to 73, an LED light source, a laser light source, or the like can be used. Light emitted from the light sources 71 to 73 is reflected or transmitted through the dichroic filters 75 and 76 and is collected on the rod integrator incident surface 23 via the condenser lens 74.

  In this example, the dichroic filters 75 and 76 are arranged in a cross arrangement, the dichroic filter 75 has red reflection and green / blue transmission characteristics, and the dichroic filter 76 has red / green transmission and blue reflection characteristics.

  The light incident on the rod integrator 20 repeats total reflection in the medium, and is emitted with a uniform illuminance distribution on the exit surface 24 of the rod integrator.

  The relay optical system 22 irradiates and enlarges the DMD 14 and 15 surfaces while maintaining the illuminance distribution on the exit surface of the rod integrator. The relay optical system is provided with an aperture 25 so that the aperture amount can be varied as required.

  By causing the red, green, and blue light sources 71, 72, and 73 to emit light sequentially, it is possible to generate illumination light of three primary colors in a time-sharing manner.

  Since the configuration after the TIR prism is the same as that shown in FIG.

  With the configuration described above, it is possible to easily realize inexpensive, bright and high-quality 3D images with one projector without complicated installation adjustment. Since this method uses relatively inexpensive polarized glasses, a projector suitable for 3D viewing by a large number of people can be provided.

11 Illumination optical system 12 TIR prism 13 Polarization separation prism 14 DMD for right eye
15 DMD for left eye
DESCRIPTION OF SYMBOLS 16 Projection lens 17 Lamp 18 Concave mirror 19 Aspherical lens 20 Rod integrator 21 Color wheel 22 Relay optical system 23 Rod integrator entrance surface 24 Rod integrator exit surface 25 Diaphragm 30 Irradiation light emitted from relay optical system 31 TIR prism Illumination light 32 Projection light (ray)
33, 33a, 33b, 33c S-polarized component (illumination light)
34, 34a, 34b, 34c P-polarized component (illumination light)
35, 35a, 35b, 35c S-polarized light component (projection light)
36, 36a, 36b, 36c P-polarized light component (projection light)
40, 40a, 40b, 40c First prism 41, 41a, 41b, 41c Second prism 42, 42a, 42b, 42c Wire grid 43, 43a, 43b, 43c PBS surface 44a Back side of wire grid 45 Reflective surface (second prism)
46 Reflecting surface (first prism)
60 Polarizing plate (for S-polarized light transmission)
61 Polarizing plate (for P-polarized light transmission)
62 ND filter 63 Glass with AR coating 71 Light source (red)
72 Light source (green)
73 Light source (blue)
74 Condensing lens 75, 76 Dichroic filter 81 White light source 82 Color selection filter (color wheel)
83 Polarization separation means (wire grid)
84, 85 Total reflection prism (TIR prism)
86, 87 Spatial light modulator (DMD)
88 Polarization combining means (polarization beam splitter)
89 Projection means (projection lens)
91 Light source 92 Color separation rotation filter (color wheel)
93 First polarization separation element 94 Optical path selection rotation filter 95 Second polarization separation element 96 Beam separation element (TIR prism)
97 DMD element 98 Projection lens

Claims (8)

A light source;
An illumination optical system that collects and emits light emitted from the light source in a specific direction;
A TIR prism for entering and exiting illumination light from the illumination optical system;
A polarization separation prism that receives illumination light emitted from the TIR prism, divides the illumination light into first linearly polarized light and second linearly polarized light whose polarization directions are orthogonal to each other, and emits the light from different positions;
The first linearly polarized light and the second linearly polarized light are located at the reflection positions, and the two linearly polarized lights are respectively modulated based on the input right eye and left eye image information, and obtained by modulating the two linearly polarized lights. Two DMD elements for reflecting the third linearly polarized light and the fourth linearly polarized light into the polarization separating prism;
The third linearly polarized light and the fourth linearly polarized light are combined as projection light by the polarization separation prism and emitted to the TIR prism, and the projection light is separated from the illumination light by the TIR prism and emitted. A projection lens that projects the projection light emitted by the TIR prism;
A projector characterized by comprising:   The projector according to claim 1, comprising a color wheel as the illumination optical system, and generating illumination light of three primary colors in a time division manner.   2. The projector according to claim 1, wherein the illumination optical system includes three single-color light sources that respectively emit red, blue, and green light, and each light source emits light in a time-sharing manner.   The projector according to claim 1, wherein a wire grid is used as a polarization separation unit of the polarization separation prism.   The projector according to claim 1, wherein the number of reflections in the polarization splitting prism until the illumination light reaches each DMD is even or odd.   The projector according to claim 1, wherein the projector is designed so that the optical path lengths of illumination light for the right eye and for the left eye are the same.   The projector according to claim 1, wherein a polarizing plate is installed between the polarization separation prism and the DMD.   The projector according to claim 1, wherein an ND filter is installed between the polarization separation prism and the DMD.

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