JP3753033B2 - Reflective projector optical system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a three-plate projection projector using a reflective light valve, and more particularly to improving the contrast of a reflective projection projector optical system that uses a Philips-like prism to separate and synthesize color light.
[0002]
[Prior art]
As a liquid crystal projector for displaying a color image, R (red), G (green), and B (blue) light beams of the three primary colors are irradiated onto the corresponding three liquid crystal panels, and each piece of R, G, and B image information is displayed. Is widely known to synthesize these color lights and project them on a screen.
[0003]
By the way, in recent years, as a liquid crystal panel, a reflective type that can increase an aperture ratio and can satisfy a demand for higher resolution and higher illuminance than a transmissive type has been known. ing. In addition, a reflective liquid crystal projector disclosed in Japanese Patent Laid-Open No. 10-48762 is used as a liquid crystal projector that uses a reflective liquid crystal light valve having such advantages and is smaller, lighter and cheaper and can eliminate the adjustment of convergence by the user. One using a projection optical system is known.
[0004]
In the above-mentioned publication, first, the light components of each color of R, G, B are separated, and after the separation, the light is reflected by three polarization beam splitters provided corresponding to the light of each color. To be irradiated. This configuration has an advantage in that the polarization beam splitter may be a single color and the reflection / transmission separation performance is improved. However, since the number of polarizing beam splitters corresponding to each color is required, there is a problem that the apparatus becomes large and the configuration becomes complicated. In the projection type display device, there is a great demand for downsizing and downsizing, and there is an urgent need to solve the above-described problems of the prior art.
[0005]
In order to solve such a problem, the technique disclosed in Japanese Patent No. 2505758 shown in FIG. 11 is effective. In the prior art shown in FIG. 11, a so-called Philips type prism 111 is used, and reflection type liquid crystal light valves 112 to 114 are arranged so as to face the light emission end faces 111b to 111d of the respective prisms 111A to 111C. Reflecting mirrors 115 to 117 are located on the surface of the liquid crystal light valves 112 to 114 opposite to the prism side. In this configuration, a single polarization beam splitter 121 can be used to separate the direction of light incidence from the light source 123 and the direction of light emission to the screen 125 for all color lights. As a result, the apparatus can be made compact and the configuration can be simplified. In addition, liquid crystal driving units 118 to 120 are provided corresponding to the reflection type liquid crystal light valves 112 to 114 for the respective color lights.
[0006]
[Problems to be solved by the invention]
  However, in the prior art shown in FIG.1An air gap 111e is provided between the prism 111A and the second prism 111B, and there is also an air gap between the polarization beam splitter 121 and the first prism 111A. The light beam traveling through the second prism 111B is totally reflected on the adjacent surface of the air gap 111e, while the light beam traveling through the first prism 111A is totally reflected on the surface of the first prism 111A on the splitter 121 side. . Therefore, when the light set to be linearly polarized light is reflected by these total reflection surfaces, the vibration surface thereof is rotated (is elliptically polarized).
[0007]
  Since the liquid crystal projector controls the output of linearly polarized light to turn light on (white) / off (black), it is extremely important to maintain the linear polarization of illumination light and image light. FIG.1In the conventional technology shown in Fig. 4, the analyzer is not able to insert an analyzer for correcting the elliptical polarization into the optical path even though the linear polarization is easily lost inside the prism. The light component that is emitted becomes very large. As a result, there has been a problem that the contrast is lowered.
[0008]
In addition, assembling the prism 111 via the air gap 111e set at a predetermined interval makes the manufacturing process complicated and it is difficult to suppress an increase in manufacturing cost.
[0009]
In view of the above circumstances, the present inventors have proposed a novel prism optical system in Japanese Patent Application No. 2000-177694 (prism optical system for a reflective projection projector). This prism optical system is inexpensive to assemble, and in a projection optical system using a reflective light valve, the plane of polarization of polarized light guided to the color separation / combination prism rotates while passing through this prism. Is suppressed, and a decrease in contrast is prevented.
[0010]
On the other hand, a technique for improving contrast has been proposed from another approach.
[0011]
The first approach is the method disclosed in Japanese Patent No. 2006746 (or US Pat. No. 5,327,270) shown in FIG. In this method, a quarter wavelength plate 135 is inserted between the element 136 and the polarization beam splitter 132 to correct the rotated polarized light.
[0012]
The second approach is the method disclosed in US Pat. No. 5,986,815 shown in FIG. That is, a wavelength plate is inserted between the element and the prism in order to improve contrast with respect to the Philips prism. The polarization rotation is corrected by changing the retardance of the inserted wave plate from ¼ wavelength, and the polarization disturbance of the color light caused by the color separation means of the Philips prism (the polarized color light is converted into the elliptically polarized light by the color separation means). Is intended to be substantially eliminated.
[0013]
[Means for Solving the Problems]
The present invention is an improvement of the reflective projection projector prism proposed in Japanese Patent Application No. 2000-177694 described above, further improving the contrast, and the conventional approach method shown in FIGS. 12 (a) and 12 (b). Compared to the above, a remarkable contrast improvement effect is exhibited.
[0014]
In order to further improve the contrast improvement, a wave plate unit is provided between the reflection type light valve positioned opposite to the emission surface of each prism corresponding to G, R, and B and the light valve facing surface of each prism. Inserting, at least one of the wave plate units is composed of two wave plates.
[0016]
  In order to solve the above-mentioned problem, the invention described in claim 1 is a total of three reflective light valves provided corresponding to the three primary color lights of (green) and B (blue),
  Multiple prismsAre joined via a dichroic film for a predetermined color light, and have respective surfaces on which the respective color lights reflected by the respective reflective light valves are made to face each of the three reflective light valves.Prism optics,
  Each of the prism optical systemsSurface,EachInserted between each reflective light valve3 in totalWith the wavelength unit plateIn at least a reflective projector optical system,
  The threeAt least one of the wavelength unit platesA first wave plate for imparting a retardance in the range of λ / 3 to λ / 5 with respect to the central wavelength of the color light reflected by the reflective light valve opposed thereto, and λ with respect to the central wavelength of the G light A reflective projector optical system comprising a combination of a second wave plate that provides retardance in the range of / 3 to λ / 5The
[0017]
For example, in a prism that transmits a light component in the red band, a wave plate having a retardance of λ / 3 to λ / 5, more preferably λ / 3 to λ / 4, with respect to the red band light. And a wave plate having a retardance of λ / 3 to λ / 5 with respect to the center wavelength of the green band. Also, a prism that transmits light components in the blue band has a retardance of λ / 3 to λ / 5, more preferably a retardance of λ / 3 to λ / 4, with respect to the blue band light. It is more preferable to use a wave plate having a retardance of λ / 3 to λ / 5 with respect to the green center wavelength.
[0018]
In a prism that transmits light components in the green band, two wave plates each having a retardance of λ / 3 to λ / 5 with respect to the green center wavelength, or λ / 3 to 3 with respect to the green center wavelength. A combination of a wave plate having a retardance of λ / 5 and a wave plate having a retardance of λ / 3 to λ / 5 with respect to the center wavelength of another channel is preferable.
[0019]
  The invention according to claim 2 is the reflection type projector optical according to claim 1,
In the prism optical system, the plurality of prisms are configured by first to third prisms, and the first prism and the second prism are joined via a first dichroic film, and the second prism and A reflection type projector optical system characterized in that a third prism is joined via a second dichroic film.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a reflective projector optical system according to an embodiment of the present invention will be described with reference to the drawings.
[0027]
<First Embodiment>
FIG. 1 shows a reflective projection projector optical system 10 according to the first embodiment of the present invention. The reflective projection projector optical system 10 includes a light source 13, a prism optical system 11, and a polarizing beam splitter 15 positioned between the light source and the prism. The prism optical system 11 includes first to third prisms 11A to 11C corresponding to G (green), R (red), and B (blue), respectively. The first prism 11A and the second prism 11B are joined via the first dichroic film 27A, and the second prism and the third prism 11C are joined via the second dichroic film 27B.
[0028]
The reflection type projector optical system 10 also includes reflection light valves 17A to 17C positioned opposite to the emission surfaces 11a to 11c of the respective prisms, and wavelengths inserted between the emission surfaces of the respective prisms and the reflection type light valves. It has board units 19A-19C.
[0029]
At least one of the reflector units 19A to 19C is a combination of two wave plates. The two wave plates are assembled so as to be rotated relative to each other so as to obtain the best contrast.
[0030]
  In the example of FIG. 1, two wavelength plate units 19B used in the second prism 11B through which the red light component propagates and two wavelength plate units 19C used in the third prism 11C through which the blue light component propagates. It is composed of a wave plate. Of the two wave plates, the first wave plates 20 and 22 are retarders of 1/3 to 1/5 wavelength with respect to the center wavelength of the color band of the light component propagating through the prisms 11B and 11C.TheThe second wave plates 21 and 23 are retarders of 1/3 to 1/5 wavelength with respect to the center wavelength of the green band.TheHave
[0031]
More specifically, the first wave plate 20 of the red channel wave plate unit 19B has a phase difference of 1/3 wavelength (or 0.82 μm wavelength) with respect to light having a wavelength of 0.62 μm (red band). A quarter-wave phase difference) is given to the second light, and the second wavelength plate 21 is given a quarter-wave phase difference to the light having a wavelength of 0.546 μm (green band).
[0032]
The first wavelength plate 22 of the blue channel wave plate unit 19C is given a quarter-wave phase difference with respect to light having a wavelength of 0.460 μm (blue band). A phase difference of ¼ wavelength is given to light having a wavelength of 546 μm (green band). Alternatively, a phase difference of ¼ wavelength is given to the first wavelength plate 22 of the wavelength plate unit 19C at 0.436 μm (blue band), and the second wavelength plate 23 is given 1 / 0.5 at 0.546 μm (green band). 3. Give a phase difference of 2 wavelengths.
[0033]
In the example shown in FIG. 1, in any wave plate unit, the first wave plate is located on the reflective light valve 17 side, and the second wave plate is an air gap between the first wave plate and the first wave plate. The same is true even if the first wave plate is arranged on the prism emission surface side and the second wave plate is arranged on the light valve side. Performance and effects are achieved.
[0034]
  The operation of such a reflective projection projector optical system 10 is as follows. The light emitted from the light source 13 isThrough the filter 14The light is reflected by the splitter surface 15 A of the polarization beam splitter 15 and guided to the prism optical system 11. Of the light incident on the prism optical system 11, the light component in the green band is reflected by the first dichroic film 27A and propagates through the first prism 11A, and is given retardance by the first wave plate unit 19A. Light modulation is performed by the first reflection type light valve 17A. This optical path is the first channel.
[0035]
On the other hand, the light components in the red band and the blue band are transmitted through the first dichroic film 27A, propagated through the second prism 11B, and enter the second dichroic film 27B. Among them, the light component in the red band is reflected by the second dichroic film 27B, propagates through the second prism 11B, and is given retardance by the second wave plate unit 19B. Thereafter, the light is modulated by the second reflective light valve 17B. This optical path is the second channel.
[0036]
The light component in the blue band passes through the second dichroic film 27B, propagates through the third prism 11C, is given retardance by the third wave plate unit 19C, and is reflected by the third reflective light valve 17C. Modulated. This optical path is the third channel.
[0037]
This channel arrangement is arranged in descending order of the visual sensitivity characteristics of the three primary colors. That is, green having the highest visual sensitivity characteristic is first separated (channel 1), red light having the second highest visual sensitivity is separated from the transmitted light (channel 2), and the remaining blue is placed in channel 3. ing. However, as long as the green component is first separated, the prism arrangement is not limited to the example of FIG. 1, and the blue band may be channel 2 and the red band may be channel 3.
[0038]
The light components modulated by the respective reflection type light valves 17 return along the optical paths of the corresponding channels, are combined, and enter the polarization beam splitter 15 again. The modulated light passes through the splitter surface 15A and is guided to a screen (not shown).
[0039]
FIG. 2 shows a first modification of the first embodiment. In the configuration example of FIG. 2, wave plate units 19A and 19B made up of two wave plates are inserted into two locations of the green band (channel 1) and the red band (channel 2), respectively.
[0040]
The first wave plate 24 of the wave plate unit 19A used in the first prism 11A gives a phase difference of 1/5 wavelength to light having a wavelength of 0.55 μm (green band), and the second wave plate 25 is A phase difference of 1 / 3.36 wavelength is given to light having a wavelength of 0.62 μm (red band). The first wave plate 20 of the wave plate unit 19B used in the second prism 11B gives a phase difference of 1 / 3.36 wavelength to light having a wavelength of 0.62 μm (red band). The wave plate 21 gives a phase difference of 1/5 wavelength to light having a wavelength of 0.55 μm (green band).
[0041]
  OrSecond prism 11BIn the first wave plate 20 of the wave plate unit 19B used in the above, a phase difference of 1 / 3.36 wavelength is given to light having a wavelength of 0.62 μm (red band), and the second wave plate 21 , A phase difference of ¼ wavelength is given to light having a wavelength of 0.55 μm (green band). In the example of FIG. 2, the two wave plates used in the green channel are configured to give retardance to light of different color bands, respectively, but are configured to give retardance to light of the same color band. It is good. For example, both of the two wave plates constituting the wave plate unit 19A may be wave plates that give a phase difference of 1/3 wavelength to 1/5 wavelength with respect to light having a wavelength of 0.55 μm (green band). Good.
[0042]
The insertion position of the wave plate unit composed of two wave plates is not limited to the combination of two of the three channels shown in FIGS.
[0043]
FIG. 3 shows a second modification of the first embodiment. In this modification, a wave plate unit composed of a combination of two wave plates in at least one channel among the three prisms is used. In the example of FIG. 3, a combination of two wave plates is used only for channel 2 in the red band. In this way, even if only two wave plates are inserted into any one of the channels, the same contrast improvement effect as in the configuration examples of FIGS. 1 and 2 can be obtained.
[0044]
FIG. 4 shows a third modification of the first embodiment. In the third modification, wave plate units 19A to 19C made of a combination of two wave plates are inserted into all channels. In this case, since the characteristics are improved in accordance with the respective bands in all the channels, the effect of improving the image quality when the return lights are combined by the beam splitter 15 and displayed on the screen is the highest.
[0045]
In any of the arrangements of the first to third modifications, one of the two wave plates has a retardance value of λ / 3 to λ / 5 with respect to the center wavelength of the light in the green band. It is set as the structure which has. By combining the wave plates having a specific range of retardance in this way, as described in detail below, a single wavelength is provided between the polarizing beam splitter and the element as in the prior art shown in FIG. The contrast ratio is remarkably improved when a plate is inserted or when a single wavelength plate is inserted in each channel as shown in FIG.
[0046]
Next, with reference to FIGS. 5 to 9, the effect of improving the contrast by inserting two wave plates will be described in detail.
[0047]
5 and 6 show the experimental results of measuring the contrast by changing the retardance for each of the case where only one wave plate is inserted and the case where two wave plates are inserted in combination in the red channel. Show. In the graph of FIG. 5, the points plotted with ■ indicate the contrast when two wave plates are inserted, and the points plotted with ◆ indicate the contrast when only one wave plate is inserted. Detailed data (wavelength used, retardance, bright characteristics, dark characteristics, background noise, contrast, and total phase difference when converted to 620 nm wavelength) of the used wave plate are as shown in FIG.
[0048]
In the graph of FIG. 5, the point indicated as “λ / 3.36 at 620 nm” gives a phase difference (retardance) of 1 / 3.36 wavelength to light having a central wavelength of 620 nm. This is data when only one wave plate is inserted. This is disclosed in the above-mentioned US Pat. No. 5,986,815 (FIG. 11 (b)). Corresponds to a value that minimizes both the ellipticity of the color beam and the direction of elliptically polarized light. The contrast value at this time is 39.46.
[0049]
On the other hand, in the first embodiment of the present invention, as shown in the column of “Using two wave plates” in FIG. 6, the retardance of λ / 3.36 to λ / 4 at 620 nm (red band). When a wave plate (first plate) and a wave plate (second plate) having a retardance of λ / 5 to λ / 3.2 at 550 nm or 546 nm (green band) are inserted in combination, the contrast becomes 80 or more. Become. In particular, when a retardance wave plate of λ / 3.6 to λ / 4 in the red band and a wave plate of λ / 4 to λ / 5 in the green band are combined, the contrast ratio is about 110, which is a remarkable effect. Is obtained.
[0050]
As described above, the use of the two wave plates for light of different wavelength bands significantly improves the contrast not only due to the polarization disturbance due to the first dichroic film 27A but also due to the polarization beam splitter 15 due to the red wave. It is considered that these disturbances are brought into the channel and can be individually adjusted with two wave plates.
[0051]
7 and 8 show the experimental results of measuring the contrast by changing the retardance in each of the case where only one wave plate is inserted in the blue channel and the case where two wave plates are combined. In the graph of FIG. 7, the points plotted with ▪ indicate the contrast when two wave plates are inserted, and the points plotted with ◆ indicate the contrast when only one wave plate is inserted. Detailed data of the used wave plate (wavelength used, retardance, bright characteristics, dark characteristics, background noise, contrast, total phase difference when converted to 460 nm) is as shown in the table of FIG. .
[0052]
7 and 8, the value indicated as “1/9 wavelength at 460 nm” is “color caused by rotation of a part of the polarization of the color beam by the color separation means disclosed in US Pat. No. 5,986,815 mentioned above. This corresponds to a value that minimizes both the ellipticity of the beam and the direction of elliptical polarization. The contrast at this time is 35: 1.
[0053]
On the other hand, in the first embodiment of the present invention, by inserting two λ / 4 wave plates at 436 nm (blue band) and λ / 3.2 wave plates at 546 nm (G band), Contrast 44 is obtained, and the contrast in the blue band is significantly improved as compared with the conventional case where only one wave plate is inserted.
[0054]
As described above, slight elliptically polarized light is inevitably generated on the polarization plane of the incident light in the color separation dichroic films 27A and 27B formed on the joint surface of the prism. In addition, a slight polarization disturbance can occur in the beam splitter. In order to eliminate such polarization disturbances individually, in the first embodiment, two wave plates that give a phase difference to light in different wavelength bands are inserted.
[0055]
FIG. 9 shows the experimental results of measuring the light and dark characteristics when only one wave plate is inserted into the green channel and when two wave plates are inserted. In the green channel, the dark characteristic (black screen) is remarkably improved, and as a result, the image quality is greatly improved.
[0056]
In the graph of FIG. 9, the thin solid line shows the bright characteristics when one wave plate of “λ / 5 at 550 nm” is inserted, and the thin broken line shows the case when two wave plates of λ / 5 at 550 nm are inserted. Bright characteristics are shown. The characteristic when one wave plate of “λ / 5 at 550 nm” is inserted is disclosed in the above-mentioned US Pat. No. 5,986,815, “Color beam caused by rotation of a part of the polarization of the color beam by the color separation means”. This corresponds to a value that minimizes both the ellipticity and the direction of elliptical polarization.
[0057]
In the graph of FIG. 9, the thick broken line indicates the dark characteristic when one wave plate having a retardance value of λ / 5 is inserted at 550 nm, and the thick solid line indicates the dark characteristic when two sheets are used. . In general, the dark characteristic is preferably a profile obtained by translating the profile of the bright characteristic downward as it is. However, if only one wave plate is inserted as in the prior art, the peak of the dark characteristic shifts to the right side, and the profile itself is also deformed.
[0058]
On the other hand, when two wave plates are inserted in the green channel as in the first embodiment of the present invention, a good profile in which only the intensity is reduced while maintaining the bright characteristic is obtained, and the image quality is greatly improved. To be improved. In the graph of FIG. 9, two λ / 5 wave plates are inserted at 550 nm, but as shown in the example of FIG. 2, a λ / 5 wave plate at 550 nm and λ / 3.36 at 620 nm. Similar effects are achieved even when used in combination with a wave plate.
[0059]
In the examples shown in FIGS. 1 to 4, the first wave plates 20 and 22 used in the color band of the channel are arranged on the reflective bulb 17 side and used for light in the green band. The second wave plates 21 and 23 are arranged on the light exit surface side of the prism, and an air gap of about 1 mm is provided therebetween. Providing an air gap facilitates assembly and prevents friction when rotating the two wave plates to an optimum angle. However, the present invention is not limited to such a configuration, and the two wave plates are brought into contact with each other so as to be capable of rotational adjustment without being provided with an air gap, and are inserted between the prism exit surface and the reflective light valve 17. May be.
[0060]
Second Embodiment
FIG. 10 shows a reflective projection projector 30 according to the second embodiment of the present invention. In the second embodiment, the first wave plates 39A to 39C are inserted between the prisms 31A to 31C and the corresponding elements (reflection type light valves) 37A to 37C, respectively. A wave plate 41 is also inserted between the system 31.
[0061]
The first wave plates 39A to 39C have a retardance of λ / 3 to λ / 5 of the main wavelength in each channel. The second wave plate 41 has a retardance of λ / 3 to λ / 5 with respect to the green center wavelength. In the embodiment shown in FIG. 10, a wavelength plate of 546 nm and λ / 4 is inserted between the prism 31 and the beam splitter.
[0062]
In the example shown in FIG. 10, a wave plate 41 is inserted between the beam splitter, the green component of the light reflected by the beam splitter is retarded to correct the polarization disturbance, and the prism exit surface of each channel. In addition, a single wave plate is inserted between the reflection light valve 37 and the light component in the color band of each channel to further retardance, thereby improving the contrast.
[0063]
The present invention is not limited to this configuration, and a wave plate unit composed of two wave plates may be used in at least one channel at the same time as inserting the wave plate 41 between the beam splitter. One of the two wave plates has a retardance of λ / 3 to λ / 5 with respect to the center wavelength of the color band to be used, and the other wave plate has a center wavelength of green. It has a retardance of λ / 3 to λ / 5. The combination of the wave plates in this case preferably follows the combination described in the first embodiment.
[0064]
By inserting a wave plate between the beam splitter 15 and the prism 37 and using two wave plates in at least one channel, contrast and dark characteristics are remarkably improved, and an improvement in image quality is realized.
[0065]
【The invention's effect】
According to the reflection type projector optical system of the present invention, a compact optical system can be obtained, and contrast improvement that cannot be achieved by the conventional method can be achieved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an optical system of a reflective projection projector according to a first embodiment of the present invention.
FIG. 2 is a diagram of a first modification of the optical system shown in FIG.
3 is a diagram of a second modification of the optical system shown in FIG. 1. FIG.
FIG. 4 is a diagram of a third modification of the optical system shown in FIG.
5 is a graph showing contrast values when one wave plate is used for the red channel of the prism shown in FIG. 1 and when two wave plates are used. FIG.
6 is a table showing detailed information of the wave plate used in the contrast measurement of FIG.
7 is a graph showing contrast when one wave plate is used for the blue channel of the prism shown in FIG. 1 and when two wave plates are used. FIG.
8 is a table showing detailed information of the wave plate used in the contrast measurement of FIG.
9 is a graph showing profiles of light and dark characteristics when one wave plate is used for the green channel of the prism shown in FIG. 1 and when two wave plates are used. FIG.
FIG. 10 is a schematic configuration diagram of an optical system of a reflective projection projector according to a second embodiment of the invention.
FIG. 11 is a diagram showing an optical system using a conventional so-called Phillips type prism.
FIG. 12 shows an example in which a quarter-wave plate is inserted between the element and the polarization beam splitter in the prior art (FIG. 12A), and a wave plate between the output surface of the prism and the element in each channel. It is a figure which shows the example (FIG.12 (b)) which inserted one sheet.
[Explanation of symbols]
10, 30 Optical system for reflective projection project
11, 31 Prism optical system
13 Light source
14 Filter
15 Beam splitter
17A-11C, 37A-37C Reflective light valve
19A-19C Wave plate unit
20, 21, 22, 23, 24, 25 Wave plate

Claims (2)

A total of three reflective light valves provided corresponding to the three primary color lights of R (red), G (green), and B (blue);
A plurality of prisms are bonded to each other through a dichroic film for a predetermined color light, and each surface on which each color light reflected by each reflective light valve is made to face each of the three reflective light valves. A prism optical system,
And each surface of the prism optical system, said at least includes a reflective projector optical system 3 and the wavelength unit plate in total are inserted between each reflection type light valve,
At least one of the three wavelength unit plates is a first wave plate that gives a retardance in the range of λ / 3 to λ / 5 with respect to the central wavelength of the color light reflected by the reflective light valve facing the plate. If, reflective projector optical system characterized by being configured by combining the second wave plate to impart retardance ranging from λ / 3~λ / 5 with respect to the center wavelength of the G light. The reflection type projector optical system according to claim 1,
In the prism optical system, the plurality of prisms are configured by first to third prisms, and the first prism and the second prism are joined via a first dichroic film, A reflection type projector optical system characterized in that a third prism is joined via a second dichroic film .

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