JP2010096843A - Total reflection prism and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a total reflection prism in which transmissivity properties to an incidence angle less than a critical angle are improved without exerting influence on reflectivity properties to an incidence angle equal to or more than a critical angle. <P>SOLUTION: In the total reflection prism 10 where the first optical face 11a of a first prism 11 and the second optical face 12a of a second prism 12 are confronted via an air gap 13, each of the first optical face 11a and the second optical face 12a is acted as a total reflection face or a transmission face in accordance with the incidence angle of light in the corresponding first prism 11 and second prism 12, total reflection light is emitted from the corresponding first prism 11 or second prism 12, the transmission light of the first optical face 11a is passed through the air gap 13, is made incident on the second prism 12 from the second optical face 12a, and is emitted, and the transmission light of the second optical face 12a is passed through the air gap 13, is made incident on the first prism 11 from the first optical face 11a, and is emitted, at least either the first optical face 11a or the second optical face 12a is provided with an antireflective film 14. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a total reflection prism and a projection apparatus using the same.

  Conventionally, there is known a TIR (Total Internal Reflection) prism having two triangular prisms as total reflection prisms, each of which is disposed so as to face each other in parallel via an air gap. .

  Further, as a projection apparatus using such a TIR prism, for example, a projection apparatus having a configuration as shown in FIG. 5 is known (see, for example, Patent Document 1).

  The projection apparatus shown in FIG. 5 causes illumination light from the light source 101 to enter the TIR prism 104 through the integrator element 102 and the illumination lens 103, transmit the TIR prism 104, and transmit the illumination light transmitted through the TIR prism 104. Is incident on a digital micromirror device (DMD) 105 which is a reflective spatial light modulator. Also, the projection light spatially modulated by the DMD 105 in accordance with the display image (ON light of the DMD 105) is incident on the TIR prism 104 and totally reflected by the TIR prism 104, and this totally reflected projection light is screen 106. Is projected on the screen.

  The TIR prism 104 includes a first prism 111 and a second prism 112 each having a triangular prism shape, and the optical surface 111a of the first prism 111 and the optical surface 112a of the second prism 112 are parallel to each other via an air gap 113. A first prism 111 and a second prism 112 are arranged to face each other.

  In the projection device shown in FIG. 5, the illumination light passing through the illumination lens 103 is incident on the optical surface 111a from the optical surface 111b of the first prism 111 at an incident angle less than the critical angle, thereby transmitting the optical surface 111a. The illumination light transmitted through the optical surface 111a is incident on the second prism 112 from the optical surface 112a of the second prism 112 through the air gap 113, and is emitted from the optical surface 112b of the second prism 112 to obtain the DMD 105. To guide you to.

  Further, the projection light from the DMD 105 is incident on the optical surface 112b of the second prism 112 at an incident angle different from the emission angle of the illumination light, and is incident on the optical surface 112a at an incident angle greater than the critical angle. Thus, the light is totally reflected by the optical surface 112a and emitted from the optical surface 112c of the second prism 112.

  As described above, the TIR prism 104 is used to appropriately set the incident angle of the illumination light with respect to the optical surface 111a and the incident angle of the projection light with respect to the optical surface 112a. Can be separated from each other, and the projector can be miniaturized.

US Pat. No. 6,880,935

  By the way, a TIR prism causes light to be totally reflected or transmitted according to the incident angle by making light incident on an air (air gap) side having a low refractive index from an optical member (prism) side having a high refractive index. I am doing so. Here, if the refractive index of the prism is n and the refractive index of the air gap is 1, the critical angle (total reflection angle) θc is given by θc = arcsin (1 / n). Therefore, if light is incident with the incident angle being equal to or greater than the critical angle θc, the incident light can be totally reflected. If incident light is less than the critical angle θc, the incident light can be transmitted.

  However, according to experiments by the present inventor, when reflecting light, the conventional TIR prism uses total reflection with the incident angle being equal to or greater than the critical angle, so that a reflectance of almost 100% can be obtained. However, it was found that when the incident angle is less than the critical angle and light is transmitted, sufficient transmittance cannot be obtained.

  FIG. 6 shows the reflectance characteristics in the visible light region of the conventional TIR prism that the present inventors have experimented, and shows a case where a prism having a refractive index of 1.65 is used. In FIG. 6, the solid line indicates the P-polarized component, and the broken line indicates the S-polarized component. In this case, the critical angle θc is around 37 degrees, and at the incident angle greater than the critical angle θc, almost 100% reflectance is obtained for both P-polarized light and S-polarized light. In the case of transmitting light, particularly with respect to S-polarized light, it can be seen that the reflectance is not sufficiently lowered even in the vicinity of the critical angle, and a sufficient transmittance is not obtained.

  For this reason, when the incident angle is less than the critical angle and the light is transmitted, a light amount loss occurs, and the light use efficiency decreases. In particular, in the case of a TIR prism, the light quantity loss becomes further remarkable because the light passes through two optical surfaces that are very close to each other through an air gap.

  In the case of a projection apparatus using a DMD as shown in FIG. 5, the angle formed between the illumination light incident on the DMD and the projection light (ON light) reflected from the DMD is determined by the DMD and secured sufficiently large. Is difficult. For this reason, in the TIR prism, since the incident angle of the illumination light and the incident angle of the projection light are generally close to each other, for example, the critical angle is intermediate between the incident angle of the illumination light and the incident angle of the projection light. In the case of FIG. 5, the incident angle of the illumination light is in the vicinity of the critical angle, and the light quantity loss of the illumination light is increased. Projection light with sufficient brightness cannot be obtained. As a result, a light source with a large amount of light is required, and there is a concern that the apparatus may be increased in size and cost. Such a problem also occurs when LCOS (Liquid Crystal On Silicon) is used as the reflective spatial light modulator.

  Therefore, the first object of the present invention made in view of the above points can improve the transmittance characteristics for incident angles below the critical angle without affecting the reflectance characteristics for incident angles greater than the critical angle, An object of the present invention is to provide a total reflection prism capable of reducing light loss.

  Furthermore, a second object of the present invention is to provide a projection apparatus that can improve the light use efficiency by using the total reflection prism and can reduce the size and cost of the apparatus.

The invention of the total reflection prism according to claim 1, which achieves the first object,
The first optical surface of the first prism and the second optical surface of the second prism are opposed to each other via an air gap, and the first prism and the second prism are arranged, and the first optical surface and Each of the second optical surfaces acts as a total reflection surface or a transmission surface according to the incident angle of the light beam in the corresponding first prism and second prism, and the total reflection light corresponds to the corresponding first prism. The first prism or the second prism emits light, and the transmitted light of the first optical surface enters the second prism from the second optical surface through the air gap, and is emitted from the second prism. The transmitted light of the second optical surface is incident on the first prism from the first optical surface through the air gap, and is emitted from the first prism.
An antireflection film is provided on at least one of the first optical surface and the second optical surface.

The invention according to claim 2 is the total reflection prism according to claim 1,
The antireflection film is provided on both the first optical surface and the second optical surface.

Furthermore, the invention of the projection apparatus according to claim 3 for achieving the second object is as follows:
A light source that emits illumination light;
The first optical surface of the first prism and the second optical surface of the second prism are opposed to each other through an air gap, and the first prism and the second prism are arranged. A total reflection prism provided with an antireflection film on at least one of the second optical surfaces;
A reflective spatial light modulation element that spatially modulates illumination light from the light source according to a display image and reflects it as projection light in a direction different from the incident light direction;
Illumination light from the light source is incident on the first prism, is incident on the first optical surface at an incident angle less than a critical angle, and illumination light transmitted through the first optical surface is the first optical surface. Alternatively, illumination light emitted from the second prism is incident on the second prism through the antireflection film provided on at least one of the second optical surfaces and the air gap, and is incident on the second prism. Led to the light modulator,
Projection light from the spatial light modulation element is incident on the second prism, is incident on the second optical surface at an incident angle greater than a critical angle, is totally reflected by the second optical surface, and is reflected on the second prism. The projection light emitted from the projector is projected.

The invention according to claim 4 is the projection apparatus according to claim 3,
The incident angle of the illumination light with respect to the first optical surface is set to an angle at which the reflectance of the illumination light on the first optical surface is substantially minimum.

Furthermore, the invention of the projection device according to claim 5 for achieving the second object is as follows:
A light source that emits illumination light;
The first optical surface of the first prism and the second optical surface of the second prism are opposed to each other through an air gap, and the first prism and the second prism are arranged. A total reflection prism provided with an antireflection film on at least one of the second optical surfaces;
A reflective spatial light modulation element that spatially modulates illumination light from the light source according to a display image and reflects it as projection light in a direction different from the incident light direction;
Illumination light from the light source is incident on the second prism and incident on the second optical surface at an incident angle greater than or equal to a critical angle, and illumination light totally reflected by the second optical surface is converted into the second optical surface. Emitted from the prism and led to the spatial light modulator,
Projection light from the spatial light modulation element is incident on the second prism, is incident on the second optical surface at an incident angle less than a critical angle, and is projected through the second optical surface. Projected light that is incident on the first prism from the first optical surface via the antireflection film and the air gap provided on at least one of the first optical surface and the second optical surface and is emitted from the first prism This is characterized in that it is configured to project.

The invention according to claim 6 is the projection apparatus according to claim 5,
The incident angle of the projection light with respect to the second optical surface is set to an angle at which the reflectance of the projection light on the second optical surface is substantially minimum.

The invention according to claim 7 is the projection apparatus according to any one of claims 3 to 6,
The antireflection film is provided on both the first optical surface and the second optical surface of the total reflection prism.

  According to the total reflection prism of the present invention, an antireflection film is formed on at least one of the first optical surface of the first prism or the second optical surface of the second prism facing the first optical surface via an air gap. Therefore, when light is transmitted through the first prism and the second prism, the transmittance characteristic of the transmitted light can be improved by the antireflection film, and the light amount loss can be reduced.

  Furthermore, according to the projection device of the present invention, it is possible to improve the transmittance characteristic of the transmitted light in the total reflection prism and reduce the light amount loss, so that the utilization efficiency of the illumination light from the light source can be improved, and as a result Since there is no need to increase the size of the light source, the apparatus can be reduced in size and cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram schematically showing a configuration of a total reflection prism according to the first embodiment of the present invention. The total reflection prism 10 constitutes a TIR prism and includes a first prism 11 and a second prism 12 each having a triangular prism shape. The first prism 11 and the second prism 12 include an optical surface 11 a that is a first optical surface of the first prism 11 and an optical surface 12 a that is a second optical surface of the second prism 12 via an air gap 13. Arrange them to face each other in parallel.

  In the present embodiment, reflection of transmitted light in the visible light region is prevented by the optical surface 11a of the first prism 11 and the optical surface 12a of the second prism 12 that are opposed in parallel via the air gap 13. The antireflection film 14 is formed respectively.

  The antireflection film 14 is formed by stacking a plurality of dielectric thin films by vapor deposition, for example. For example, when the first prism 11 and the second prism 12 are made of glass having a refractive index of 1.65, the antireflection film 14 is a nine-layer dielectric thin film having the refractive index and thickness shown in Table 1. It is constructed by stacking. In Table 1, the layer order is 1 to 9 from the prism toward the air gap 13, and each layer is formed to have an absorption coefficient of 0 using a known dielectric material.

  In this way, among the light rays that enter the first prism 11 from the optical surface 11b or the optical surface 11c of the first prism 11, light rays that are incident on the optical surface 11a at an incident angle less than the critical angle are incident on the optical surface 11a. Reflection is prevented by the antireflection film 14 formed on the optical surface 11a and transmitted through the optical surface 11a and the antireflection film 14, and the transmitted light is transmitted from the optical surface 12a of the second prism 12 through the air gap 13 to the optical surface. Reflection is prevented by the antireflection film 14 formed on the surface 12a, and the light enters the second prism 12, and is emitted from the optical surface 12b or the optical surface 12c of the second prism 12 according to the triangular shape of the second prism 12. Let

  Of the light rays that enter the first prism 11 from the optical surface 11b or the optical surface 11c of the first prism 11, light rays that are incident on the optical surface 11a at an incident angle greater than the critical angle are totally reflected by the optical surface 11a. Then, depending on the triangular shape of the first prism 11, the reflected light is sent from the same optical surface 11b or the optical surface 11c, or the other optical surface 11c or the optical surface of the first prism 11 excluding the optical surface 11a. The light is emitted from the surface 11b.

  Similarly, of the light rays that enter the second prism 12 from the optical surface 12b or the optical surface 12c of the second prism 12, light rays that enter the optical surface 12a at an incident angle less than the critical angle are formed on the optical surface 12a. The antireflection film 14 prevents reflection, transmits the optical surface 12a and the antireflection film 14, and transmits the transmitted light from the optical surface 11a of the first prism 11 through the air gap 13 to the optical surface 11a. The reflection is prevented by the antireflection film 14 formed on the first prism 11 and is incident on the first prism 11, and is emitted from the optical surface 11 b or the optical surface 11 c of the first prism 11 according to the triangular shape of the first prism 11.

  Of the light rays that enter the second prism 12 from the optical surface 12b or the optical surface 12c of the second prism 12, light rays that enter the optical surface 12a at an incident angle greater than the critical angle are totally reflected by the optical surface 12a. Then, depending on the triangular shape of the second prism 12, the reflected light is transmitted from the same optical surface 12b or the optical surface 12c, or the other optical surface 12c or the optical surface of the second prism 12 excluding the optical surface 12a. The light is emitted from the surface 12b.

  FIG. 2 shows the reflectance characteristics in the visible light region in the total reflection prism 10 according to the present embodiment. In the total reflection prism 10 in this case, the first prism 11 and the second prism 12 are made of glass having a refractive index of 1.65, and the optical surface 11a of the first prism 11 and the optical surface 12a of the second prism 12 are arranged on the optical surface 12a. Each of the antireflection films 14 formed is composed of the nine dielectric multilayer films shown in Table 1 above.

  According to the present embodiment, as is clear from the comparison with the reflectance characteristics of the conventional TIR prism shown in FIG. 6, at an incident angle greater than the critical angle, as in the conventional case, P-polarized light (solid line) and S A reflectance of almost 100% is obtained for both polarized light (dashed line). In addition, at an incident angle less than the critical angle, the antireflection film 14 formed on the optical surface 11a of the first prism 11 and the optical surface 12a of the second prism 12, respectively, has both P-polarized light and S-polarized light having a reflectance higher than that of the prior art. And the transmittance characteristics of transmitted light are improved. Therefore, it is possible to reduce a light amount loss when transmitting light.

  Strictly speaking, for P-polarized light, there has conventionally been a Brewster angle where the reflectivity is 0 around 32 degrees, and in this embodiment, the Brewster angle is around 22 degrees. Existing. For this reason, in the case of the present embodiment, the reflectance of P-polarized light at an incident angle near 30 degrees is slightly higher than the conventional one, but the reflectance is lowered at an incident angle of 30 degrees or less. Therefore, the total reflectivity combined with S-polarized light at an incident angle less than the critical angle is sufficiently lower than that of a conventional TIR prism having no antireflection film.

(Second Embodiment)
FIG. 3 is a diagram showing a schematic configuration of a projection apparatus according to the second embodiment of the present invention. This projection apparatus uses the total reflection prism 10 shown in FIG. 1, and the illumination light from the light source 21 passes through the integrator element 22 and the illumination lens 23, and the optical surface 11 b of the first prism 11 of the total reflection prism 10. Is incident on the optical surface 11a at an incident angle less than the critical angle, and is transmitted through the antireflection film 14 formed on the optical surface 11a.

  The illumination light transmitted through the first prism 11 enters the second prism 12 through the air gap 13 and from the optical surface 12a of the second prism 12 through the antireflection film 14 formed on the optical surface 12a. The illumination light emitted from the optical surface 12 b is incident on the DMD 25.

  The DMD 25 spatially modulates incident illumination light by reflecting it in a predetermined direction according to a display image, and the spatially modulated projection light (ON light of the DMD 25) is optically applied to the second prism 12 of the total reflection prism 10. The light is incident on the optical surface 12a from the surface 12b at an incident angle greater than the critical angle, totally reflected by the optical surface 12a, and the totally reflected projection light is emitted from the optical surface 12c of the second prism 12 to the screen 26. Projection display.

  Here, the incident angle of the illumination light with respect to the optical surface 11a of the first prism 11 constituting the total reflection prism 10 and the incident angle of the projection light with respect to the optical surface 12a of the second prism 12 are the incident angle of the illumination light and the projection. Although the total reflection prism 10 and the DMD 25 can be arranged so that the critical angle is located in the middle of the incident angle of light, in the present embodiment, the incident angle of illumination light to be transmitted is determined by the reflectance. Is set so as to shift away from the critical angle so that is substantially minimized. That is, when the total reflection prism 10 has the reflectance characteristic shown in FIG. 2, the reflectance of the P-polarized light is almost 0 and the overall reflectance is minimized, and the illumination light is about 22 degrees. The incident angle is set, and accordingly, the incident angle of the projection light is set to be greater than the critical angle and shifted to the critical angle side.

  In the case of projecting a color image, the light source 21 is configured using a known lamp that emits white light, such as a high-pressure mercury lamp or a xenon lamp, and the white light from the light source 21 is rotated by a rotating color filter. In this case, the image data is sequentially separated into RGB, and in synchronization with the color separation of the illumination light, the corresponding color image signal is supplied to the DMD 25, and the color image is projected and displayed in the surface sequential order. Alternatively, the light source 21 is configured using, for example, an R, G, B three-color LED or a three-color laser, and each color is sequentially emitted, and an image signal of a corresponding color is sent to the DMD 25 in synchronization with the emission. It is also possible to project and display a color image in a surface sequential manner. Alternatively, it is also possible to irradiate the DMD 25 with white illumination light and provide RGB color filters in pixel units in front of the DMD 25 (input / exit surface) to simultaneously project and display a color image.

  According to the present embodiment, the total reflection prism 10 having the antireflection film 14 shown in FIG. 1 is used, and the illumination light from the light source 21 is guided through the total reflection prism 10 to the DMD 25 and projected from the DMD 25. Since the light is totally reflected by the total reflection prism 10 and projected and displayed on the screen 26, the light amount loss of the illumination light incident on the DMD 25 can be reduced. Therefore, since the light utilization efficiency can be improved, it is not necessary to increase the size of the light source 21, and the apparatus can be reduced in size and cost. Moreover, in the present embodiment, the incident angle of the illumination light with respect to the optical surface 11a of the total reflection prism 10 is set so as to be shifted to an angle at which the reflectivity is substantially minimized, so that the light quantity loss of the illumination light can be more effectively reduced. It becomes possible to suppress to.

(Third embodiment)
FIG. 4 is a diagram showing a schematic configuration of a projection apparatus according to the third embodiment of the present invention. This projection apparatus is obtained by reversing the arrangement of an illumination system having a light source 21, an integrator element 22 and an illumination lens 23 and a projection system having a screen 26 in the projection apparatus shown in FIG.

  That is, in the projection apparatus shown in FIG. 4, the illumination light from the light source 21 is incident on the optical surface 12a from the optical surface 12c of the second prism 12 of the total reflection prism 10 through the integrator element 22 and the illumination lens 23 at a critical angle or more. The light is incident at an angle and totally reflected by the optical surface 12a. The totally reflected illumination light is emitted from the optical surface 12b and is incident on the DMD 25.

  The projection light modulated by the DMD 25 is incident on the optical surface 12a from the optical surface 12b of the second prism 12 at an incident angle less than the critical angle, and is transmitted through the antireflection film 14 formed on the optical surface 12a. Let The projection light transmitted through the optical surface 12a is incident on the first prism 11 through the air gap 13 and from the optical surface 11a of the first prism 11 through the antireflection film 14 formed on the optical surface 11a. The projection light emitted from the optical surface 11 b and projected from the optical surface 11 b is projected and displayed on the screen 26.

  In the configuration shown in FIG. 4, the incident angle of the illumination light and the incident angle of the projection light with respect to the optical surface 12 a of the second prism 12 of the total reflection prism 10 are the difference between the incident angle of the illumination light and the incident angle of the projection light. Although the total reflection prism 10 and the DMD 25 can be arranged so that the critical angle is located in the middle, in the present embodiment, the incident angle of the projection light to be transmitted is set so that the reflectance is substantially minimized. And set in a direction away from the critical angle. That is, when the total reflection prism 10 has the reflectance characteristics shown in FIG. 2, the reflectance of the P-polarized light is almost 0 and the overall reflectance is minimum, and the projected light is about 22 degrees. The incident angle is set, and accordingly, the incident angle of the illumination light is set to be greater than the critical angle and shifted to the critical angle side. Other configurations and operations are the same as those of the second embodiment.

  Therefore, according to the present embodiment, it is possible to reduce the light amount loss when the projection light from the DMD 25 passes through the total reflection prism 10 and to improve the light use efficiency. Similarly to the case, it is not necessary to increase the size of the light source 21, and the apparatus can be reduced in size and cost. In addition, in the present embodiment, the incident angle of the projection light with respect to the optical surface 12a of the total reflection prism 10 is set so as to be shifted to an angle at which the reflectivity is almost the minimum, so that the light quantity loss of the projection light is more effectively reduced. It becomes possible to suppress to.

  In addition, this invention is not limited only to the said embodiment, Many deformation | transformation or a change is possible. For example, in the above embodiment, the optical surface 11a of the first prism 11 of the total reflection prism 10 and the optical surface 12a of the second prism 12 are opposed in parallel via the air gap 13, but the total reflection prism If the incident angles of the light beam that passes through 10 with respect to the optical surface 11a and the optical surface 12a are less than the critical angle, it is not always necessary to oppose them in parallel.

  Further, in the above embodiment, the antireflection film 14 is formed on both the optical surface 11a of the first prism 11 and the optical surface 12a of the second prism 12 facing the total reflection prism 10, but the optical surface 11a or It is also possible to form a total reflection prism by forming the antireflection film 14 only on one of the optical surfaces 12a. Even in this case, the reflectance of transmitted light can be reduced as compared with a TIR prism having no conventional antireflection film. Therefore, when applied to a projection apparatus, the light source can be reduced in size, and as a result, the apparatus can be reduced in size and cost.

  Furthermore, the first prism and the second prism constituting the total reflection prism can be formed into an arbitrary triangular shape, and if one surface of the first prism and one surface of the second prism face each other through an air gap, Not only the triangular prism shape but also any polygonal shape can be used according to the arrangement of the illumination system and the projection system.

  In the second embodiment and the third embodiment, the DMD is used as the reflective spatial light modulation element. However, the projection apparatus may be configured using LCOS. Further, the projection apparatus is not limited to a single plate type using a single spatial light modulation element, but may be configured as a two plate type using two spatial light modulation elements or a three plate type using three spatial light modulation elements. .

It is a figure which shows typically the structure of the total reflection prism which concerns on 1st Embodiment of this invention. It is a figure which shows the reflectance characteristic in the visible light area | region in the total reflection prism shown in FIG. It is a figure which shows schematic structure of the projection apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows schematic structure of the projection apparatus which concerns on 3rd Embodiment of this invention. It is a figure which shows schematic structure of the conventional projector. It is a figure which shows the reflectance characteristic in the visible light area | region in the conventional TIR prism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Total reflection prism 11 1st prism 11a Optical surface (1st optical surface)
11b, 11c Optical surface 12 Second prism 12a Optical surface (second optical surface)
12b, 12c Optical surface 13 Air gap 14 Antireflection film 21 Light source 22 Integrator element 23 Illumination lens 25 DMD
26 screens

Claims (7)

The first optical surface of the first prism and the second optical surface of the second prism are opposed to each other via an air gap, and the first prism and the second prism are arranged, and the first optical surface and Each of the second optical surfaces acts as a total reflection surface or a transmission surface according to the incident angle of the light beam in the corresponding first prism and second prism, and the total reflection light corresponds to the corresponding first prism. The first prism or the second prism emits light, and the transmitted light of the first optical surface enters the second prism from the second optical surface through the air gap, and is emitted from the second prism. The transmitted light of the second optical surface is incident on the first prism from the first optical surface through the air gap, and is emitted from the first prism.
A total reflection prism, wherein an antireflection film is provided on at least one of the first optical surface and the second optical surface.   The total reflection prism according to claim 1, wherein the antireflection film is provided on both the first optical surface and the second optical surface. A light source that emits illumination light;
The first optical surface of the first prism and the second optical surface of the second prism are opposed to each other through an air gap, and the first prism and the second prism are arranged. A total reflection prism provided with an antireflection film on at least one of the second optical surfaces;
A reflective spatial light modulation element that spatially modulates illumination light from the light source according to a display image and reflects it as projection light in a direction different from the incident light direction;
Illumination light from the light source is incident on the first prism, is incident on the first optical surface at an incident angle less than a critical angle, and illumination light transmitted through the first optical surface is the first optical surface. Alternatively, illumination light emitted from the second prism is incident on the second prism through the antireflection film provided on at least one of the second optical surfaces and the air gap, and is incident on the second prism. Led to the light modulator,
Projection light from the spatial light modulation element is incident on the second prism, is incident on the second optical surface at an incident angle greater than a critical angle, is totally reflected by the second optical surface, and is reflected on the second prism. A projection apparatus configured to project projection light emitted from a projector.   The projection apparatus according to claim 3, wherein the incident angle of the illumination light with respect to the first optical surface is set to an angle at which the reflectance of the illumination light on the first optical surface is substantially minimum. A light source that emits illumination light;
The first optical surface of the first prism and the second optical surface of the second prism are opposed to each other through an air gap, and the first prism and the second prism are arranged. A total reflection prism provided with an antireflection film on at least one of the second optical surfaces;
A reflective spatial light modulation element that spatially modulates illumination light from the light source according to a display image and reflects it as projection light in a direction different from the incident light direction;
Illumination light from the light source is incident on the second prism and incident on the second optical surface at an incident angle greater than or equal to a critical angle, and illumination light totally reflected by the second optical surface is converted into the second optical surface. Emitted from the prism and led to the spatial light modulator,
Projection light from the spatial light modulation element is incident on the second prism, is incident on the second optical surface at an incident angle less than a critical angle, and is projected through the second optical surface. Projected light that is incident on the first prism from the first optical surface via the antireflection film and the air gap provided on at least one of the first optical surface and the second optical surface and is emitted from the first prism A projection apparatus configured to project   The projection apparatus according to claim 5, wherein the incident angle of the projection light with respect to the second optical surface is set to an angle at which the reflectance of the projection light on the second optical surface is substantially minimum.   The projection apparatus according to claim 3, wherein the antireflection film is provided on both the first optical surface and the second optical surface of the total reflection prism.

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