Relay optical system and projector

Abstract

To provide a compact relay optical system with excellent optical characteristics.SOLUTION: A relay optical system couples an enlargement side imaging plane to a reduction side imaging plane obtained by reducing the enlargement side imaging plane. The relay optical system comprises a first lens group composed of a plurality of lenses and having positive power, a second lens group including a diaphragm and at least one negative lens and having negative power, and a third lens group composed of a plurality of lenses and having positive power, in order in which a beam passes from an enlargement side toward a reduction side. The number of lenses in the first lens group and the number of lenses in the third lens group are equal. An arrangement of the respective lens power of the plurality of lenses of the first lens group, which are arranged from the enlargement side toward the reduction side, is the same as an arrangement of each lens power of the plurality of lenses of the third lens group, which are arranged from the reduction side toward the enlargement side. The enlargement side and the reduction side of the relay optical system are telecentric, respectively.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a relay optical system and a projector. [Background technology]

[0002] An optical system connecting an enlarged-side image forming surface and a reduced-side image forming surface obtained by changing the magnification of the enlarged-side image forming surface is described in Patent Document 1. The first projection optical unit in this document is an optical system that is telecentric on both sides and connects a primary image forming surface and an object surface obtained by reducing the primary image forming surface. The first projection optical unit includes a first lens group having a positive power, a second lens group having a negative power, and a third lens group having a positive power. The first lens group is composed of four lenses. The second lens group is composed of an aperture stop and five lenses. The third lens group is composed of three lenses. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-330410 A Summary of the Invention [Problem to be solved by the invention]

[0004] The optical system of Patent Document 1 has a problem in that if an attempt is made to improve the optical characteristics, the overall lens length becomes longer. [Means for solving the problem]

[0005] In order to solve the above problem, the relay optical system of the present invention is a relay optical system that connects a magnification-side image forming surface and a reduction-side image forming surface that is a reduction of the magnification-side image forming surface, and comprises, in order of passage of a light ray from the magnification side to the reduction side, a first lens group having positive power composed of multiple lenses, a second lens group having negative power including an aperture and at least one negative lens, and a third lens group having positive power composed of multiple lenses, wherein the number of lenses in the first lens group and the number of lenses in the third lens group are the same, an arrangement of the lens powers of the multiple lenses in the first lens group arranged from the magnification side to the reduction side is the same as an arrangement of the lens powers of the multiple lenses in the third lens group arranged from the reduction side to the magnification, and the magnification side and the reduction side are each telecentric.

[0006] The projector of the present invention is a projector including the relay optical system described above, the projector including: a light source; a separation optical system that separates white light emitted from the light source into a first color light in a first wavelength band including blue light and another color light in a wavelength band longer than the first color light; a first light modulation element that modulates the first color light separated by the separation optical system; a second light modulation element that modulates the other color light separated by the separation optical system; the relay optical system, in which the first light modulation element is disposed on the enlargement-side image forming plane, reduces a beam width of the first color light modulated by the first light modulation element on the reduction-side image forming plane; and a combined light obtained by combining the first color light whose beam width has been reduced by the relay optical system and the other color light modulated by the second light modulation element. the effective area of ​​the first light modulation element is larger than the effective area of ​​the second light modulation element; the relay optical system comprises a first plane mirror arranged between the enlargement side image forming surface and the first lens group, and a second plane mirror arranged between the third lens group and the reduction side image forming surface, the first plane mirror and the second plane mirror each bending a light ray, the optical axis of the enlargement side image forming surface is parallel to the optical axis of the reduction side image forming surface, and the incident direction of the first color light entering the enlargement side image forming surface is opposite to the exit direction of the first color light exiting from the reduction side image forming surface.

[0007] The projector of the present invention is a projector including the relay optical system described above, comprising: a light source; a separation optical system that separates white light emitted from the light source into a first color light in a first wavelength band including blue light and another color light in a wavelength band longer than the first color light; a first light modulation element that modulates the first color light separated by the separation optical system; a second light modulation element that modulates the other color light separated by the separation optical system; the first light modulation element is disposed on the enlargement-side image forming plane, the relay optical system that reduces, on the reduction-side image forming plane, a light beam width of the first color light modulated by the first light modulation element; and a combination of the first color light whose light beam width has been reduced by the relay optical system and the other color light modulated by the second light modulation element. the effective area of ​​the first light modulation element is larger than the effective area of ​​the second light modulation element; the relay optical system comprises a first plane mirror arranged between the enlargement-side image forming surface and the first lens group, and a second plane mirror arranged inside the first lens group, the first plane mirror and the second plane mirror each refracting a light ray, the optical axis of the enlargement-side image forming surface is parallel to the optical axis of the reduction-side image forming surface, and the incident direction of the first color light incident on the enlargement-side image forming surface is opposite to the exit direction of the first color light exiting from the reduction-side image forming surface. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of a main part of a projector that uses the relay optical system of the first embodiment. [Diagram 2] 4 is a diagram showing the MTF on the reduction side of the relay optical system of the first embodiment. FIG. [Diagram 3] FIG. 13 is a diagram showing the MTF on the reduction side of the relay optical system of the comparative example. [Figure 4] 11 is a schematic diagram of a main part of a projector that uses a relay optical system according to a second embodiment. [Diagram 5] 13 is a diagram showing the MTF on the reduction side of a relay optical system 6A according to the second embodiment. FIG. [Figure 6]FIG. 11 is a schematic diagram of a main part of a projector that uses a relay optical system according to a third embodiment. [Figure 7] FIG. 11 is a diagram showing the MTF on the reduction side of the relay optical system of the third embodiment. [Figure 8] FIG. 11 is a ray diagram of a relay optical system according to a fourth embodiment. [Figure 9] FIG. 13 is a diagram showing the MTF on the reduction side of the relay optical system of the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A relay optical system and a projector according to an embodiment of the invention will be described below with reference to the drawings.

[0010] [Embodiment 1] Fig. 1 is a schematic diagram of a main part of a projector 100 using a relay optical system 6 of embodiment 1. As shown in Fig. 1, the projector 100 includes a light source 1, an illumination optical system 2 that uniformizes the light emitted from the light source 1, a separation optical system 3 that separates the light emitted from the illumination optical system 2 into each color light, a plurality of light modulation elements 7 that modulate each color light separated by the separation optical system 3 to form a projection image, a reflection mirror 11, a relay optical system 6 that reduces the luminous flux width of the color light modulated by one of the plurality of light modulation elements 7, a color synthesis prism 8 that outputs a synthetic light obtained by synthesizing each color light modulated by the light modulation element 7, a projection optical system 9 that projects the synthetic light output from the color synthesis prism 8, and a control unit 10 that controls the light modulation element 7.

[0011] For convenience, in the following description, the three mutually orthogonal axes are referred to as the X-axis, Y-axis, and Z-axis. The direction along the first optical axis N of the separation optical system 3 is referred to as the X-axis direction. In the X-axis direction, the direction in which the output light from the illumination optical system 2 is output is referred to as the first direction X1, and the opposite direction is referred to as the second direction X2. In the Y-axis direction, the direction in which the combined light is output from the color combining prism 8 is referred to as the third direction Y1, and the opposite direction is referred to as the fourth direction Y2.

[0012] The light source 1 is, for example, an extra-high pressure mercury lamp, a solid-state light source, etc. In this embodiment, the light source 1 emits white light as the emitted light LD.

[0013] The illumination optical system 2 includes a multi-lens 21, a polarizing beam splitter 22, a multi-lens 23, and a relay lens 24. The multi-lens 21 splits the output light LD from the light source 1 into multiple light beams. The polarizing beam splitter 22 converts the polarization direction of the output light LD output from the multi-lens 21. The multi-lens 23 focuses the output light LD output from the polarizing beam splitter 22 in the vicinity of the relay lens 24. The relay lens 24 magnifies the output light LD incident from the multi-lens 23 and outputs it toward the separation optical system 3.

[0014] The separation optical system 3 includes, in order in the first direction X1, a first dichroic mirror 31 and a second dichroic mirror 32. The first dichroic mirror 31 and the second dichroic mirror 32 are disposed along a first optical axis N of the separation optical system 3. The optical axis of the output light LD from the illumination optical system 2 coincides with the first optical axis N.

[0015] The first dichroic mirror 31 separates the output light LD into a first color light LB and another color light LC. The first dichroic mirror 31 reflects the first color light LB in a fourth direction Y2 and transmits the other color light LC in a first direction X1. The second dichroic mirror 32 separates the other color light LC into a second color light LG and a third color light LR. The second dichroic mirror 32 reflects the third color light LR in a third direction Y1 and transmits the second color light LG in a first direction X1. In this embodiment, the first color light LB is a first wavelength band including blue light. The second color light LG is a second wavelength band including green. The third color light LR is a third wavelength band including red. The first wavelength band is, for example, 420 nm to 500 nm. The second wavelength band is, for example, 500 nm to 600 nm. The third wavelength band is, for example, 600 nm to 680 nm. The wavelength band of the other color light LC is, for example, 500 nm to 680 nm.

[0016] Here, a reflecting mirror 14 is disposed in the third direction Y1 of the second dichroic mirror 32, which reflects the third color light LR separated by the second dichroic mirror 32 in the first direction X1. A reflecting mirror 15 is disposed in the first direction X1 of the second dichroic mirror 32, which reflects the second color light LG separated by the second dichroic mirror 32 in the third direction Y1. Lenses 12 are disposed between the second dichroic mirror 32 and the reflecting mirror 14, and between the second dichroic mirror 32 and the reflecting mirror 15. Lenses 13 are disposed in the first direction X1 of the reflecting mirror 14 and in the third direction Y1 of the reflecting mirror 15. The lenses 12 and 13 focus the second color light LG and the third color light LR separated by the separation optical system 3 near the light modulation element 7.

[0017] The reflecting mirror 11 is disposed in the fourth direction Y2 of the first dichroic mirror 31. The reflecting mirror 11 reflects the first color light LB separated by the first dichroic mirror 31 in the first direction X1. Here, the projector 100 includes a relay lens 19 between the reflecting mirror 11 and the first dichroic mirror 31. The relay lens 19 adjusts the imaging position of the first color light LB so that the first color light LB from the first dichroic mirror 31 is uniformly irradiated onto the first light modulation element 71. In this embodiment, the relay lens 19 is made up of one lens. Note that the relay lens 19 may be made up of a plurality of lenses.

[0018] The light modulation element 7 is a liquid crystal panel. The light modulation element 7 includes a first light modulation element 71 that modulates the first color light LB, a third light modulation element 72 that modulates the second color light LG, and a fourth light modulation element 73 that modulates the third color light LR. The first light modulation element 71, the third light modulation element 72, and the fourth light modulation element 73 each include an incident side polarizing plate 75 and an exit side polarizing plate 76. The third light modulation element 72 and the fourth light modulation element 73 correspond to the "second light modulation element" of the present invention.

[0019] The first light modulation element 71 is disposed in the first direction X1 of the first dichroic mirror 31. The optical axis N1 of the first light modulation element 71 extends in the direction along the X-axis. The optical axis N1 of the first light modulation element 71 is parallel to the first optical axis N of the separation optical system 3.

[0020] The third light modulation element 72 is disposed at a position facing the second surface 82 of the color synthesis prism 8. The fourth light modulation element 73 is disposed at a position facing the third surface 83 of the color synthesis prism 8.

[0021] The effective area of ​​the first light modulation element 71 is larger than the effective area of ​​the third light modulation element 72 and the fourth light modulation element 73. Here, the effective area refers to the area of ​​the effective display area of ​​the light modulation element. In this embodiment, the first light modulation element 71 is a liquid crystal panel having an effective display area with a diagonal dimension of 1.03 inches, and the third light modulation element 72 and the fourth light modulation element 73 are liquid crystal panels having an effective display area with a diagonal dimension of 0.67 inches.

[0022] The relay optical system 6 connects the enlargement-side image forming surface 60A and the reduction-side image forming surface 60B obtained by reducing the enlargement-side image forming surface 60A. The first light modulation element 71 is disposed on the enlargement-side image forming surface 60A, and the relay optical system 6 reduces the light beam width of the first color light LB modulated by the first light modulation element 71 on the reduction-side image forming surface 60B. That is, the relay optical system 6 is an optical system that changes magnification. In this embodiment, the relay optical system 6 reduces the light beam width of the first color light LB modulated by the first light modulation element 71 from 1.03 inches to 0.67 inches on the reduction-side image forming surface 60B. The optical axis N1 of the first light modulation element 71 and the optical axis M1 of the enlargement-side image forming surface 60A coincide with each other. The reduction-side image forming surface 60B is disposed at a position facing the first surface 81 of the color synthesis prism 8. The air-equivalent distance between the reduction-side image forming surface 60B and the first surface 81 of the color combining prism 8 is the same as the air-equivalent distance between the third light modulation element 72 and the second surface 82 of the color combining prism 8. In addition, the air-equivalent distance between the reduction-side image forming surface 60B and the first surface 81 of the color combining prism 8 is the same as the air-equivalent distance between the fourth light modulation element 73 and the third surface 83 of the color combining prism 8.

[0023] Here, the projector 100 has a polarizing plate 5 disposed between the reduction-side imaging surface 60B and the first surface 81. The polarizing plate 5 and the exit-side polarizing plate 76 of the first light modulation element 71 transmit linearly polarized components in the same direction among the polarized components contained in the first color light LB. That is, when the exit-side polarizing plate 76 of the first light modulation element 71 transmits the S-polarized light of the first color light LB, the polarizing plate 5 transmits the S-polarized light, and when the exit-side polarizing plate 76 of the first light modulation element 71 transmits the P-polarized light of the first color light LB, the polarizing plate 5 transmits the P-polarized light.

[0024] The color synthesis prism 8 has a first surface 81 on which the first colored light LB is incident, a second surface 82 on which the second colored light LG is incident, a third surface 83 on which the third colored light LR is incident, and a fourth surface 84 from which the synthesized light LE is emitted. The first surface 81 and the third surface 83 face each other in the X-axis direction. The second surface 82 and the fourth surface face each other in the Y-axis direction. The color synthesis prism 8 emits synthesized light LE, which is obtained by combining the first colored light LB, the light flux width of which has been reduced by the relay optical system 6, the second colored light LG modulated by the third light modulation element 72, and the third colored light LR modulated by the fourth light modulation element 73, from the fourth surface 84 in the third direction Y1. Here, the beam width of the first color light LB incident on the first surface 81 of the color synthesis prism 8 is the same as the beam width of the second color light LG incident on the second surface 82 of the color synthesis prism 8 and the beam width of the third color light LR incident on the third surface 83 of the color synthesis prism 8.

[0025] The projection optical system 9 projects the combined light LE emitted from the color combining prism 8 onto a screen. The projection optical system 9 includes a plurality of lenses. The control unit 10 operates the light modulation element 7 based on an external image signal such as a video signal.

[0026] (Details of the relay optical system) 1, the relay optical system 6 includes, in order of passage of a light ray from the enlargement side to the reduction side, a first lens group G1 having positive power and made up of multiple lenses, a second lens group G2 having negative power including a diaphragm 65 and at least one negative lens, and a third lens group G3 having positive power and made up of multiple lenses. The first lens group G1, the second lens group G2, and the third lens group G3 are disposed along a second optical axis M of the relay optical system 6.

[0027] The first lens group G1 is composed of four lenses L1 to L4. L1 to L4 are arranged in this order from the enlargement side to the reduction side. Lens L1 has positive power. Lens L1 has convex shapes on the enlargement side and reduction side surfaces. Lens L2 has positive power. Lens L2 has a convex shape on the enlargement side surface and a concave shape on the reduction side surface. Lens L3 has positive power. Lens L3 has a convex shape on the enlargement side surface and a concave shape on the reduction side surface. Lens L4 has negative power. Lens L4 has a convex shape on the enlargement side surface and a concave shape on the reduction side surface. Lens L3 and lens L4 are cemented together to form a cemented lens L21.

[0028] The second lens group G2 is composed of two lenses L5-L6 and an aperture 65. The lenses L5, L6, and the aperture 65 are arranged in this order from the enlargement side to the reduction side. The lens L5 has positive power. The lens L5 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. The lens L5 has aspheric shapes on the enlargement side and reduction side surfaces. The lens L6 (negative lens) has negative power. The lens L6 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. The lens L6 has aspheric shapes on the enlargement side and reduction side surfaces. Here, among the lenses of the first lens group G1, the second lens group G2, and the third lens group G3, the effective radius of the lens L6 is the smallest.

[0029] The third lens group G3 is composed of four lenses, lens L7 to lens L10. Lenses L7 to L10 are arranged in this order from the enlargement side to the reduction side. Lens L7 has negative power. Lens L7 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. Lens L8 has positive power. Lens L8 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. Lens L9 has positive power. Lens L9 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. Lens L10 has positive power. Lens L10 has a convex shape on the enlargement side surface and a concave shape on the reduction side surface. Lenses L7 and L8 are cemented together to form cemented lens L22.

[0030] The number of lenses in the first lens group G1 and the number of lenses in the third lens group G3 are the same, four. The arrangement of the lens powers of the lenses L1 to L4 in the first lens group G1 arranged from the enlargement side to the reduction side is the same as the arrangement of the lens powers of the lenses L10 to L7 in the third lens group G3 arranged from the reduction side to the enlargement side. Specifically, the arrangement of the lens powers of the lenses L1 to L4 in the first lens group G1 is positive, positive, positive, negative, from the enlargement side to the reduction side. The arrangement of the lens powers of the lenses L10 to L7 in the third lens group G3 is positive, positive, positive, negative, from the reduction side to the enlargement side.

[0031] The relay optical system 6 includes a first plane mirror 66 disposed between the enlargement-side image forming surface 60A and the first lens group G1, and a second plane mirror 67 disposed between the third lens group G3 and the reduction-side image forming surface 60B. The first plane mirror 66 has a planar shape. The first plane mirror 66 is disposed in the fourth direction Y2 of the first lens group G1. The second plane mirror 67 has a planar shape. The second plane mirror 67 is disposed in the third direction Y1 of the third lens group G3. The first plane mirror 66 and the second plane mirror 67 each bend a light beam by 90°.

[0032] The first color light LB modulated by the first light modulation element 71 travels in the first direction X1. The first color light LB that reaches the first plane mirror 66 from the first light modulation element 71 is reflected by the first plane mirror 66 in the third direction Y1. The first color light LB reflected by the first plane mirror 66 passes through the first lens group G1, the second lens group G2, and the third lens group G3, and reaches the second plane mirror 67. The first color light LB that reaches the second plane mirror 67 is reflected by the second plane mirror 67 in the second direction X2. The first color light LB reflected by the second plane mirror 67 reaches the reduction-side imaging surface 60B.

[0033] The optical axis M1 of the enlargement-side imaging surface 60A and the optical axis M2 of the reduction-side imaging surface 60B are parallel. The incident direction of the first color light LB incident on the enlargement-side imaging surface 60A is a first direction X1. The exit direction of the first color light LB exiting from the reduction-side imaging surface 60B is a second direction X2. In other words, the incident direction of the first color light LB incident on the enlargement-side imaging surface 60A is opposite to the exit direction of the first color light LB exiting from the reduction-side imaging surface 60B.

[0034] The enlargement-side image forming surface 60A and the reduction-side image forming surface 60B are located in the first direction X1 on the same side with respect to the first surface 81 of the color synthesis prism 8. In other words, the first light modulation element 71 and the reduction-side image forming surface 60B are located in the first direction X1 on the same side with respect to the first surface 81 of the color synthesis prism 8.

[0035] The enlargement side and reduction side of the relay optical system 6 are telecentric. The enlargement side of the relay optical system 6 is telecentric when the central ray of each light beam passing between the first lens group G1 and the enlargement side image forming surface 60A is parallel to the optical axis M1 or approximately parallel to the optical axis M1. The reduction side of the relay optical system 6 is telecentric when the central ray of each light beam passing between the third lens group G3 and the reduction side image forming surface 60B is parallel to the optical axis M2 or approximately parallel to the optical axis M2. In this embodiment, the angle between the central ray of each light beam and the optical axes M1 and M2 is within ±5.2°.

[0036] If the maximum image height on the reduction-side image plane 60B of the relay optical system 6 is Yb, the total length of the relay optical system 6 is TL, the lens length of the relay optical system 6 is LA, the F-number on the reduction side of the relay optical system 6 is Fn, and the magnification of the relay optical system 6 is E, the data of the relay optical system 6 is as follows.

[0037] Yb 8.499mm Length 149.613mm LA 58.000mm Fn 1.56 E 1.53

[0038] The lens data of the relay optical system 6 is as follows. Surface numbers are assigned in order from the magnification side to the reduction side. The symbols are those of the magnification side image forming surface, the first plane mirror, the lens, the second plane mirror and the reduction side image forming surface. The "*" next to the lens surface number indicates that the shape is aspheric. R is the radius of curvature. D is the axial surface spacing. Y is the effective radius. The units of R, D and Y are mm.

[0039] Code Surface number RD Glass material Refraction / Reflection Y 60A 0 0.00000 31.580246 Refraction 13.0186 66 1 0.00000 -19.000000 Reflection 26.3350 L1 2 -162.37680 -5.201359 FDS90_HOYA Refraction 19.1260 3 84.32601 -0.100000 Refraction 19.1500 L2 4 -35.44181 -5.352889 TAFD5F_HOYA Refraction 17.8110 5 -116.32346 -0.100000 Refraction 17.1550 L3 6 -19.11042 -7.518746 LAC14_HOYA Refraction 14.2080 L4 7 -124.60481 -1.700000 FDS90_HOYA Refraction 12.7950 8 -10.75908 -7.171088 Refraction 8.8980 L5 *9 14.30563 -2.069460 MFCD1_HOYA Refraction 8.8520 *10 12.99599 -0.600000 Refraction 8.9860 L6 *11 11.66571 -0.839981 MCFDS91050_HOYA Refraction 8.5710 *12 18.19224 -0.100000 Refraction 8.8900 65 13 0.00000 -6.930074 Refraction 9.1000 L7 14 28.86896 -6.473631 TAC8_HOYA Refraction 12.5060 L8 15 16.10000 -1.700000 FDS90_HOYA Refraction 13.6680 16 22.67072 -0.100000 Refraction 15.7660 L9 17 35.65690 -6.961152 TAC8_HOYA Refraction 16.9490 18 21.45000 -0.100000 Refraction 17.8570 L10 19 -43.75576 ​​-4.981621 TAC8_HOYA Refraction 18.2240 20 -236.70294 -19.532922 Refraction 17.9300 67 21 0.00000 21.500000 Reflection 24.6370 60B 22 0.00000 0.000000 Refraction 8.4990

[0040] Face number 9 10 11 12 Conic constant 5.053678E-03 -2.860697E+00 -3.230191E-01 -6.97551E+00 4th order coefficient -3.06104E-04 -1.7453E-04 -3.34083E-04 -1.53851E-04 6th order coefficient 2.5211E-06 4.6784E-06 3.1088E-06 -8.54971E-08 8th order coefficient -1.24701E-08 -2.93731E-08 -1.56141E-08 9.73958E-09 10th order coefficient 9.8277E-11 1.02513E-10 5.06999E-11 -4.04748E-11

[0041] When the maximum image height at the enlargement-side image forming surface 60A and the reduction-side image forming surface 60B is 1, the angle of the central ray of each light beam at the enlargement-side image forming surface 60A relative to the optical axis M1, and the angle of the central ray of each light beam at the reduction-side image forming surface 60B relative to the optical axis M2 are as follows:

[0042] Image height Magnification side image plane Reduction side image plane 1 4.754 5.198 0.9 4.419 4.722 0.85 4.225 4.481 0.75 3.803 3.989 0.5 2.619 2.706 0 0.000 0.000

[0043] Here, in the relay optical system 6 of this embodiment, if the largest air spacing is L1, the effective diameter of the smaller of the two imaging surfaces, the lens and the enlargement-side image surface or the reduction-side image surface adjacent to the largest air spacing, is D1, the second largest air spacing is L2, and the effective diameter of the smaller of the two imaging surfaces, the lens and the enlargement-side image surface or the reduction-side image surface adjacent to the second largest air spacing, is D2, the following conditional formula is satisfied. D1 <L1 (1) D2 <L2 (2)

[0044] In this embodiment, the largest air gap L1 is provided between the enlargement-side imaging surface 60A and the lens L1. The effective diameter D1 is the effective diameter of the enlargement-side imaging surface 60A adjacent to the largest air gap L1. The second largest air gap L2 is provided between the lens L10 and the reduction-side imaging surface 60B. The effective diameter D2 is the effective diameter of the reduction-side imaging surface 60B adjacent to the second largest air gap L2. The specific numerical values ​​are as follows.

[0045] D1 26.0372mm L1 50.5802mm D2 16.998mm L2 41.0329mm Therefore, the relay optical system 6 of this embodiment satisfies the conditional expressions (1) and (2).

[0046] (Action and effect) The relay optical system 6 of this embodiment connects the enlargement side image forming surface 60A and the reduction side image forming surface 60B obtained by reducing the enlargement side image forming surface 60A. The relay optical system 6 includes, in the order of light passing from the enlargement side to the reduction side, a first lens group G1 having positive power and composed of multiple lenses, a second lens group G2 having negative power including an aperture 65 and lenses L5 and L6 which are negative lenses, and a third lens group G3 having positive power and composed of multiple lenses. The number of lenses in the first lens group G1 and the number of lenses in the third lens group G3 are the same, 4. The arrangement of the lens powers of the lenses L1 to L4 of the first lens group G1 arranged from the enlargement side to the reduction side is the same as the arrangement of the lens powers of the lenses L10 to L7 of the third lens group G3 arranged from the reduction side to the enlargement, and is positive, positive, positive, and negative. The enlargement side of the first lens group G1 and the reduction side of the third lens group G3 are each telecentric.

[0047] In this embodiment, the lens configuration of the first lens group G1 arranged from the enlargement side to the reduction side and the lens configuration of the third lens group G3 arranged from the reduction side to the enlargement side are symmetrical, so that the various aberrations occurring in the first lens group G1 can be cancelled by the various aberrations occurring in the third lens group G3, thereby improving the optical performance of the relay optical system 6.

[0048] Since the relay optical system 6 in this embodiment is telecentric on both sides, the installation precision required when incorporating the relay optical system 6 into the projector 100 is not as strict as when both sides of the relay optical system 6 are not telecentric, and the arrangement is easier.

[0049] In this embodiment, the first lens group G1 has, in order from the enlargement side to the reduction side, two positive lenses L1-L2 and a cemented lens L21, and the third lens group G3 has, in order from the reduction side to the enlargement side, two positive lenses L10-L9 and a cemented lens L22. Since the first lens group G1 and the third lens group G3 each have a cemented lens, the chromatic aberration of magnification generated in the first lens group G1 can be more effectively canceled by the third lens group G3. Also, since the first lens group G1 and the third lens group G3 each have two positive lenses, the overall length of the relay optical system 6 can be shortened.

[0050] In this embodiment, the lens L6, which has the smallest effective diameter among the lenses in the first lens group G1, the second lens group G2, and the third lens group G3, has an aspheric shape. Here, the lens L6 is adjacent to the aperture 65, and all light rays pass through the lens L6 in a divergent state. Therefore, if the lens L6 has an aspheric shape, various aberrations can be improved favorably for all image heights, and the optical performance of the relay optical system 6 can be improved.

[0051] In the relay optical system 6, if the largest air spacing is L1, the effective diameter of the smaller one of the lens and one of the enlargement-side image forming surfaces adjacent to the largest air spacing is D1, the second largest air spacing is L2, and the effective diameter of the smaller one of the lens and the enlargement-side image forming surface and the reduction-side image forming surface adjacent to the second largest air spacing is D2, the following conditional formula is satisfied. D1 <L1 (1) D2 <L2 (2)

[0052] In this embodiment, the relay optical system 6 satisfies the conditional expressions (1) and (2), so that the relay optical system 6 can easily change the optical path to any angle at the largest air gap L1 and the second largest air gap L2. This improves the degree of freedom in the layout of the relay optical system 6. In addition, since the largest air gap L1 is larger than the effective diameter D1 of the enlargement-side image forming surface 60A, it is easy to control the light beam even if the refraction angle of the lens L1 adjacent to the largest air gap L1 is not large. Since the second largest air gap L2 is larger than the effective diameter D2 of the reduction-side image forming surface 60B, it is easy to control the light beam even if the refraction angle of the lens L10 adjacent to the second largest air gap L2 is not large.

[0053] The relay optical system 6 of this embodiment includes a first plane mirror 66 arranged at the largest air gap, and a second plane mirror 67 arranged at the second largest air gap. The largest air gap is provided between the enlargement-side image forming surface 60A and the first lens group G1. The second largest air gap is provided between the third lens group G3 and the reduction-side image forming surface 60B. Therefore, it is easy to arrange the first plane mirror 66 and the second plane mirror 67 in the relay optical system 6.

[0054] In this embodiment, the first plane mirror 66 and the second plane mirror 67 each refract light rays. The optical axis M1 of the enlargement-side image forming surface 60A and the optical axis M2 of the reduction-side image forming surface 60B are parallel to each other. The incident direction of the light rays entering the enlargement-side image forming surface 60A is opposite to the incident direction of the light rays entering the reduction-side image forming surface 60B. Therefore, the relay optical system 6 can efficiently bend the optical path by 180°.

[0055] The projector 100 of this embodiment includes a light source 1, a separation optical system 3 that separates the output light LD emitted from the light source 1 into a first color light LB in a first wavelength band including blue light and other color light in a wavelength band longer than the first color light LB, a first light modulation element 71 that modulates the first color light LB separated by the separation optical system 3, a second light modulation element that modulates the other color light separated by the separation optical system 3, a relay optical system 6 in which the first light modulation element 71 is disposed on an enlargement-side image forming surface 60A and that reduces the luminous flux width of the first color light LB modulated by the first light modulation element 71 on a reduction-side image forming surface 60B, a color synthesis prism 8 that emits synthesized light LE obtained by synthesizing the first color light LB whose luminous flux width has been reduced by the relay optical system 6 and the other color light modulated by the second light modulation element, and a projection optical system 9 that projects the synthesized light LE emitted from the color synthesis prism 8. The effective area of ​​the first light modulation element 71 is larger than the effective area of ​​the second light modulation element. The optical axis N1 of the first light modulation element 71 is parallel to the optical axis M1 of the enlargement-side image forming surface 60A.

[0056] According to this embodiment, the projector 100 uses the relay optical system 6 of this embodiment, and therefore it is possible to provide the projector 100 with improved optical performance.

[0057] According to this embodiment, since the effective area of ​​the first light modulation element 71 is larger than that of the second light modulation element, the illuminance irradiated on the first light modulation element 71 can be made smaller than that on the second light modulation element. This makes it possible to prevent the liquid crystal of the first light modulation element 71 from being deteriorated by light even if the light source 1 is made brighter.

[0058] In addition, since the relay optical system 6 can reduce the beam width of the first color light LB modulated by the first light modulation element 71 at the reduction-side imaging surface 60B, the beam widths of each color light incident on the color synthesis prism 8 can be made the same size even if the effective area of ​​the first light modulation element 71 is larger than the effective area of ​​the third light modulation element 72.

[0059] In addition, the relay optical system 6 bends the first color light LB incident on the enlargement-side imaging surface 60A by 180 degrees and emits the first color light LB from the reduction-side imaging surface 60B, so the entire projector can be made more compact than when the relay optical system 6 does not bend the first color light LB.

[0060] Fig. 2 is a diagram showing the MTF on the reduction side of the relay optical system 6 of the embodiment 1. The horizontal axis of Fig. 2 is the spatial frequency, and the vertical axis is the contrast reproduction ratio. The wavelengths in Fig. 2 are 450 nm, 460 nm, and 470 nm. As shown in Fig. 2, the relay optical system 6 of this embodiment has high resolution.

[0061] Here, as a comparative example, Example 3 of Japanese Patent Application Laid-Open No. 2006-330410, which is a prior art document, will be considered. The relay optical system of the comparative example is telecentric on both sides and connects an enlargement-side image forming surface with a reduction-side image forming surface obtained by reducing the enlargement-side image forming surface. The relay optical system of the comparative example includes a first lens group having positive power, a second lens group having negative power, and a third lens group having positive power. The first lens group of the comparative example is composed of four lenses. The second lens group of the comparative example is composed of an aperture stop and five lenses. The third lens group of the comparative example is composed of three lenses.

[0062] If the maximum image height on the reduction-side image plane of the relay optical system of the comparative example is Yb0, the total length of the relay optical system of the comparative example is TL0, the lens length of the relay optical system of the comparative example is LA0, the F-number on the reduction side of the relay optical system of the comparative example is Fn0, and the magnification of the relay optical system of the comparative example is E0, then the data of the relay optical system of the comparative example is as follows: Note that the lens data of the relay optical system of the comparative example is the same as Example 3 of JP2006-330410A, and will not be described here.

[0063] Yb0 8.499mm TL0 229.353mm LA0 199.512mm Fn0 2.46 E0 3.00

[0064] When the maximum image height Yb0 of the reduction-side image forming surface of the relay optical system of the comparative example is set to the same specifications as the maximum image height Yb of the reduction-side image forming surface of the relay optical system 6 of this embodiment, the relay optical system of the comparative example has a longer overall length and a longer lens length than the relay optical system 6 of this embodiment. In other words, the relay optical system 6 of this embodiment is more compact than the relay optical system of the comparative example.

[0065] Fig. 3 is a diagram showing the MTF on the reduction side of the relay optical system of the comparative example. The horizontal axis of Fig. 3 is the spatial frequency, and the vertical axis is the contrast reproduction ratio. The wavelengths in Fig. 3 are 450 nm, 460 nm, and 470 nm. Comparing Fig. 2 with Fig. 3, it can be seen that the first lens group G1 and the third lens group G3 of the comparative example have different numbers of lenses and are not symmetrical in lens configuration, so that the resolution of the relay optical system of the comparative example is inferior to the resolution of the relay optical system 6 of the present embodiment. In other words, it can be seen that the relay optical system 6 of the present embodiment is more compact than the relay optical system of the comparative example and has higher optical performance.

[0066] [Embodiment 2] 4 is a schematic diagram of a main part of a projector 100A using a relay optical system 6A of embodiment 2. Lens data of the relay optical system 6A of embodiment 2 is different from that of the relay optical system 6 of embodiment 1. Therefore, in embodiment 2, the same components as those in embodiment 1 are denoted by the same reference numerals, and descriptions thereof may be omitted.

[0067] (Details of the relay optical system) 4, the relay optical system 6A of this embodiment includes, in order of passage of light rays from the enlargement side to the reduction side, a first lens group G1 having positive power and made up of multiple lenses, a second lens group G2 having negative power including an aperture 65 and at least one negative lens, and a third lens group G3 having positive power and made up of multiple lenses. The first lens group G1, the second lens group G2, and the third lens group G3 are arranged along a second optical axis M of the relay optical system 6A.

[0068] The first lens group G1 consists of four lenses L1 to L4. L1 to L4 are arranged in this order from the enlargement side to the reduction side. Lens L1 has positive power. Lens L1 has convex shapes on the enlargement side and reduction side surfaces. Lens L2 has positive power. Lens L2 has a convex shape on the enlargement side surface and a concave shape on the reduction side surface. Lens L3 has positive power. Lens L3 has convex shapes on the enlargement side and reduction side surfaces. Lens L4 has negative power. Lens L4 has concave shapes on the enlargement side and reduction side surfaces. Lens L3 and lens L4 are cemented together to form cemented lens L21.

[0069] The second lens group G2 is composed of two lenses L5-L6 and an aperture 65. The lenses L5, L6 and the aperture 65 are arranged in this order from the enlargement side to the reduction side. The lens L5 has positive power. The lens L5 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. The lens L5 has aspheric shapes on the enlargement side and the reduction side surfaces. The lens L6 (negative lens) has negative power. The lens L6 has a concave shape on the enlargement side and the reduction side surfaces. The lens L6 has aspheric shapes on the enlargement side and the reduction side surfaces. Here, among the lenses of the first lens group G1, the second lens group G2 and the third lens group G3, the effective radius of the lens L6 is the smallest.

[0070] The third lens group G3 is composed of four lenses, lens L7 to lens L10. Lenses L7 to L10 are arranged in this order from the enlargement side to the reduction side. Lens L7 has negative power. Lens L7 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. Lens L8 has positive power. Lens L8 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. Lens L9 has positive power. Lens L9 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. Lens L10 has positive power. Lens L10 has convex shapes on the enlargement side and reduction side surfaces. Lenses L7 and L8 are cemented together to form cemented lens L22.

[0071] The number of lenses in the first lens group G1 and the number of lenses in the third lens group G3 are the same, four. The arrangement of the lens powers of the lenses L1 to L4 in the first lens group G1 arranged from the enlargement side to the reduction side is the same as the arrangement of the lens powers of the lenses L10 to L7 in the third lens group G3 arranged from the reduction side to the enlargement side. Specifically, the arrangement of the lens powers of the lenses L1 to L4 in the first lens group G1 is positive, positive, positive, negative, from the enlargement side to the reduction side. The arrangement of the lens powers of the lenses L10 to L7 in the third lens group G3 is positive, positive, positive, negative, from the reduction side to the enlargement side.

[0072] The relay optical system 6A includes a first plane mirror 66 arranged between the enlargement-side image plane 60A and the first lens group G1, and a second plane mirror 67 arranged between the third lens group G3 and the reduction-side image plane 60B.

[0073] The first color light LB modulated by the first light modulation element 71 travels in the first direction X1. The first color light LB that reaches the first plane mirror 66 from the first light modulation element 71 is reflected by the first plane mirror 66 in the third direction Y1. The first color light LB reflected by the first plane mirror 66 passes through the first lens group G1, the second lens group G2, and the third lens group G3, and reaches the second plane mirror 67. The first color light LB that reaches the second plane mirror 67 is reflected by the second plane mirror 67 in the second direction X2. The first color light LB reflected by the second plane mirror 67 reaches the reduction-side imaging surface 60B.

[0074] The optical axis M1 of the enlargement-side imaging surface 60A and the optical axis M2 of the reduction-side imaging surface 60B are parallel to each other. The incident direction of the first color light LB incident on the enlargement-side imaging surface 60A is opposite to the exit direction of the first color light LB exiting from the reduction-side imaging surface 60B.

[0075] The enlargement side and reduction side of the relay optical system 6A are telecentric. In this embodiment, the angle between the central ray of each light beam and the optical axis M1, M2 is within ±2°.

[0076] If the maximum image height on the reduction-side image plane 60B of the relay optical system 6A is Yb, the total length of the relay optical system 6A is TL, the lens length of the relay optical system 6A is LA, the F-number on the reduction side of the relay optical system 6A is Fn, and the magnification of the relay optical system 6A is E, the data of the relay optical system 6A is as follows.

[0077] Yb 8.499mm Length 157.655mm LA 58.000mm Fn 1.56 E 1.53

[0078] The lens data of the relay optical system 6A is as follows. Surface numbers are assigned in order from the magnification side to the reduction side. The symbols are those of the magnification side image forming surface, the first plane mirror, the lens, the second plane mirror, and the reduction side image forming surface. The "*" next to the lens surface number indicates that the shape is aspheric. R is the radius of curvature. D is the axial surface spacing. Y is the effective radius. The units of R, D, and Y are mm.

[0079] Code Surface number RD Glass material Refraction / Reflection Y 60A 0 0.00000 28.154788 Refraction 13.0186 66 1 0.00000 -18.500000 Reflection 27.8830 L1 2 -107.63712 -6.485840 FDS90_HOYA Refraction 20.3360 3 85.68986 -0.100000 Refraction 20.3200 L2 4 -29.56915 -7.016961 NBFD10_HOYA Refraction 18.1800 5 -115.35450 -0.100000 Refraction 17.2140 L3 6 -20.48438 -8.554328 BACD5_HOYA Refraction 13.7230 L4 7 61.37167 -1.300000 FDS90_HOYA Refraction 11.8820 8 -9.70000 -6.628532 Refraction 7.9460 L5 *9 458.39535 -3.324156 BSC7_HOYA Refraction 7.8010 *10 31.39990 -0.500000 Refraction 7.6000 L6 *11 29.45725 -0.805000 FDS90_HOYA Refraction 7.2970 *12 -114.50403 -0.319784 Refraction 7.3000 65 13 0.00000 -8.897059 Refraction 7.3000 L7 14 37.01021 -8.953012 TAC8_HOYA Refraction 13.0850 L8 15 17.80000 -1.750000 FDS90_HOYA Refraction 15.0450 16 23.69118 -0.100000 Refraction 17.0080 L9 17 40.40714 -6.305598 TAC8_HOYA Refraction 18.3270 18 25.42241 -0.100000 Refraction 19.2350 L10 19 -47.93663 -6.759729 TAC8_HOYA Refraction 20.3860 20 1012.76142 -20.000000 Refraction 20.0880 67 21 0.00000 23.000000 Reflection 27.8550 60B 22 0.00000 0.000000 Refraction 8.4910

[0080] Face number 9 10 11 12 Conic constant -1.243444E-02 -1.264546E+01 7.140675E+00 -2.515701E+01 4th order coefficient -4.15449E-05 3.10839E-04 1.04584E-04 -6.4658E-05 6th order coefficient -5.46074E-07 -3.62938E-06 -1.29098E-06 7.36208E-07 8th order coefficient 2.88462E-09 1.21847E-08 -2.16956E-10 -2.45258E-09 10th order coefficient -1.32879E-10 1.06056E-10 1.38152E-10 0

[0081] When the maximum image height at the enlargement-side image forming surface 60A and the reduction-side image forming surface 60B is 1, the angle of the central ray of each light beam at the enlargement-side image forming surface 60A relative to the optical axis M1, and the angle of the central ray of each light beam at the reduction-side image forming surface 60B relative to the optical axis M2 are as follows:

[0082] Image height Magnification side image plane Reduction side image plane 1 1.998 1.972 0.9 1.928 1.990 0.85 1.875 1.965 0.75 1.736 1.863 0.5 1.255 1.394 0 0.000 0.000

[0083] Here, in the relay optical system 6A of this embodiment, if the largest air spacing is L1, the smaller effective diameter of the lens and one of the enlargement-side image forming surfaces adjacent to the largest air spacing is D1, the second largest air spacing is L2, and the smaller effective diameter of the lens and the other of the enlargement-side image forming surface and the reduction-side image forming surface adjacent to the second largest air spacing is D2, the following conditional formula is satisfied. D1 <L1 (1) D2 <L2 (2)

[0084] In this embodiment, the largest air gap L1 is provided between the enlargement-side imaging surface 60A and the lens L1. The effective diameter D1 is the effective diameter of the enlargement-side imaging surface 60A adjacent to the largest air gap L1. The second largest air gap L2 is provided between the lens L10 and the reduction-side imaging surface 60B. The effective diameter D2 is the effective diameter of the reduction-side imaging surface 60B adjacent to the second largest air gap L2. The specific numerical values ​​are as follows.

[0085] D1 26.0372mm L1 46.6548mm D2 16.9820mm L2 43.0000mm Therefore, the relay optical system 6A of this embodiment satisfies the conditional expressions (1) and (2).

[0086] (Action and effect) The relay optical system 6A of the second embodiment can obtain the same effects as those of the first embodiment. Fig. 5 is a diagram showing the MTF on the reduction side of the relay optical system 6A of the second embodiment. Comparing Fig. 5 with Fig. 3, it can be seen that the relay optical system 6A of this embodiment has higher resolution than the relay optical system of the comparative example, and therefore has higher optical performance.

[0087] [Embodiment 3] 6 is a schematic diagram of a main part of a projector 100B using a relay optical system 6B of embodiment 3. The configuration and lens data of the relay optical system 6B of embodiment 3 are different from those of the relay optical system 6 of embodiment 1. Also, the configuration of the separation optical system 3 of the projector 100B of embodiment 3 is different from that of the separation optical system 3 of the projector 100 of embodiment 1. Therefore, in embodiment 3, the same configurations as those of embodiment 1 may be assigned the same reference numerals and descriptions thereof may be omitted.

[0088] As shown in FIG. 6, the separation optical system 3 includes, in order in the first direction X1, a second dichroic mirror 32, a first dichroic mirror 31, and an extension optical system 30. The second dichroic mirror 32, the first dichroic mirror 31, and the extension optical system 30 are arranged along a first optical axis N of the separation optical system 3. The second dichroic mirror 32 separates the output light LD into a third color light LR and a mixed light LC. The second dichroic mirror 32 reflects the third color light LR in the third direction Y1 and transmits the mixed light LC in the first direction X1. The first dichroic mirror 31 separates the mixed light LC into a first color light LB and a second color light LG (another color light). The first dichroic mirror 31 reflects the second color light LG in the third direction Y1 and transmits the first color light LB in the first direction X1. In this embodiment, the first colored light LB is a first wavelength band including blue light. The second colored light LG is a second wavelength band including green. The third colored light LR is a third wavelength band including red. The first wavelength band is, for example, 420 nm to 500 nm. The second wavelength band is, for example, 500 nm to 600 nm. The third wavelength band is, for example, 600 nm to 680 nm. The wavelength band of the mixed light LC is, for example, 420 nm to 600 nm.

[0089] The extension optical system 30 extends the optical path of the separation optical system 3 in a first direction X1. The extension optical system 30 includes a plurality of lenses 36. The plurality of lenses 36 are arranged along a first optical axis N of the separation optical system 3. The extension optical system 30 is arranged between the first dichroic mirror 31 and the first light modulation element 71.

[0090] Here, a reflecting mirror 14 that reflects the third color light LR separated by the second dichroic mirror 32 toward the first direction X1 is disposed in the third direction Y1 of the second dichroic mirror 32. Lenses 12 are disposed between the second dichroic mirror 32 and the reflecting mirror 14, and between the second dichroic mirror 32 and the first dichroic mirror 31. Lenses 13 are disposed in the first direction X1 of the reflecting mirror 14 and in the third direction Y1 of the first dichroic mirror 31. The lenses 12 and 13 focus the second color light LG and the third color light LR separated by the separation optical system 3 near the light modulation element 7.

[0091] The first light modulation element 71 is disposed on the first optical axis N in the first direction X1 of the extension optical system 30. That is, the optical axis N1 of the first light modulation element 71 and the first optical axis N coincide with each other. The third light modulation element 72 is disposed at a position facing the second surface 82 of the color synthesis prism 8. The fourth light modulation element 73 is disposed at a position facing the third surface 83 of the color synthesis prism 8.

[0092] The effective area of ​​the first light modulation element 71 is larger than the effective area of ​​the third light modulation element 72 and the fourth light modulation element 73. In this embodiment, the first light modulation element 71 is a 1.03-inch liquid crystal panel, and the third light modulation element 72 and the fourth light modulation element 73 are 0.67-inch liquid crystal panels.

[0093] The relay optical system 6B connects the enlargement-side image forming surface 60A and the reduction-side image forming surface 60B obtained by reducing the enlargement-side image forming surface 60A. The first light modulation element 71 is disposed on the enlargement-side image forming surface 60A, and the relay optical system 6 reduces the beam width of the first color light LB modulated by the first light modulation element 71 on the reduction-side image forming surface 60B. In this embodiment, the relay optical system 6B reduces the beam width of the first color light LB modulated by the first light modulation element 71 from 1.03 inches to 0.67 inches on the reduction-side image forming surface 60B. The optical axis N1 of the first light modulation element 71 and the optical axis M1 of the enlargement-side image forming surface 60A coincide with each other. The reduction-side image forming surface 60B is disposed at a position facing the first surface 81 of the color synthesis prism 8.

[0094] Here, the projector 100B has a polarizing plate 5 disposed between the reduction-side imaging surface 60B and the first surface 81. The polarizing plate 5 and the output-side polarizing plate 76 of the first light modulation element 71 transmit linearly polarized components in the same direction among the polarized components contained in the first color light LB.

[0095] (Details of the relay optical system) As shown in Fig. 6, the relay optical system 6B includes, in order from the enlargement side to the reduction side, a first lens group G1 made up of multiple lenses and having positive power, a second lens group G2 having one or two lenses, at least one of which is a negative lens and having negative power, and a third lens group G3 made up of multiple lenses and having positive power. The relay optical system 6B includes a diaphragm 65 between the second lens group G2 and the third lens group G3. The first lens group G1, the second lens group G2, and the third lens group G3 are arranged along a second optical axis M of the relay optical system 6B.

[0096] The first lens group G1 is composed of four lenses L1 to L4. L1 to L4 are arranged in this order from the enlargement side to the reduction side. Lens L1 has positive power. Lens L1 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. Lens L2 has positive power. Lens L2 has convex shapes on the enlargement side and reduction side surfaces. Lens L3 has positive power. Lens L3 has a convex shape on the enlargement side surface and a concave shape on the reduction side surface. Lens L4 has negative power. Lens L4 has concave shapes on the enlargement side and reduction side surfaces. Lens L3 and lens L4 are cemented together to form cemented lens L21.

[0097] The second lens group G2 is composed of two lenses L5-L6 and an aperture 65. The lenses L5, L6, and the aperture 65 are arranged in this order from the enlargement side to the reduction side. The lens L5 has positive power. The lens L5 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. The lens L5 has aspheric shapes on the enlargement side and reduction side surfaces. The lens L6 (negative lens) has negative power. The lens L6 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. The lens L6 has aspheric shapes on the enlargement side and reduction side surfaces. Here, among the lenses of the first lens group G1, the second lens group G2, and the third lens group G3, the effective radius of the lens L6 is the smallest.

[0098] The third lens group G3 is composed of four lenses, lens L7 to lens L10. Lenses L7 to L10 are arranged in this order from the enlargement side to the reduction side. Lens L7 has negative power. Lens L7 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. Lens L8 has positive power. Lens L8 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. Lens L9 has positive power. Lens L9 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. Lens L10 has positive power. Lens L10 has a convex shape on the enlargement side surface and a concave shape on the reduction side surface. Lenses L7 and L8 are cemented together to form cemented lens L22.

[0099] The lens L1 is disposed on a portion M4 extending in the Y-axis direction of the second optical axis M. The lenses L2 to L10 are disposed on a portion M3 extending in the X-axis direction of the second optical axis M.

[0100] The number of lenses in the first lens group G1 and the number of lenses in the third lens group G3 are the same, four. The arrangement of the lens powers of the lenses L1 to L4 in the first lens group G1 arranged from the enlargement side to the reduction side is the same as the arrangement of the lens powers of the lenses L10 to L7 in the third lens group G3 arranged from the reduction side to the enlargement side. Specifically, the arrangement of the lens powers of the lenses L1 to L4 in the first lens group G1 is positive, positive, positive, negative, from the enlargement side to the reduction side. The arrangement of the lens powers of the lenses L10 to L7 in the third lens group G3 is positive, positive, positive, negative, from the reduction side to the enlargement side.

[0101] The relay optical system 6 includes a first plane mirror 66 disposed between the magnification-side image plane 60A and the first lens group G1, and a second plane mirror 67 disposed inside the first lens group G1 and between the lenses L1 and L2. The first plane mirror 66 has a planar shape. The first plane mirror 66 is disposed in the fourth direction Y2 of the lens L1. The second plane mirror 67 has a planar shape. The second plane mirror 67 is disposed in the third direction Y1 of the lens L2. The first plane mirror 66 and the second plane mirror 67 each bend a light beam by 90°.

[0102] The first colored light LB modulated by the first light modulation element 71 travels in the first direction X1. The first colored light LB that reaches the first plane mirror 66 from the first light modulation element 71 is reflected by the first plane mirror 66 in the third direction Y1. The first colored light LB reflected by the first plane mirror 66 passes through the lens L1 and reaches the second plane mirror 67. The first colored light LB that reaches the second plane mirror 67 is reflected by the second plane mirror 67 in the second direction X2. The first colored light LB reflected by the second plane mirror 67 passes through the lenses L2 to L10 and reaches the reduction-side imaging surface 60B.

[0103] The optical axis M1 of the enlargement-side imaging surface 60A and the optical axis M2 of the reduction-side imaging surface 60B are parallel. The incident direction of the first color light LB incident on the enlargement-side imaging surface 60A is a first direction X1. The exit direction of the first color light LB exiting from the reduction-side imaging surface 60B is a second direction X2. In other words, the incident direction of the first color light LB incident on the enlargement-side imaging surface 60A is opposite to the exit direction of the first color light LB exiting from the reduction-side imaging surface 60B.

[0104] The enlargement-side image forming surface 60A and the reduction-side image forming surface 60B are located in the first direction X1 on the same side with respect to the first surface 81 of the color synthesis prism 8. In other words, the first light modulation element 71 and the reduction-side image forming surface 60B are located in the first direction X1 on the same side with respect to the first surface 81 of the color synthesis prism 8.

[0105] The enlargement side and reduction side of the relay optical system 6B are telecentric. In this embodiment, the angle between the central ray of each light beam and the optical axis M1, M2 is within ±2°.

[0106] The first optical axis N of the separation optical system 3 and at least a portion M3 of the second optical axis M of the relay optical system 6B are parallel to each other. The portion M3 of the second optical axis M is perpendicular to the first surface 81 of the color synthesis prism 8 onto which the first color light LB is incident. When viewed from the Y-axis direction orthogonal to the first optical axis N and the portion M3 of the second optical axis M, the extension optical system 30 overlaps with the relay optical system 6B.

[0107] If the maximum image height on the reduction-side image plane 60B of the relay optical system 6B is Yb, the total length of the relay optical system 6B is TL, the lens length of the relay optical system 6B is LA, the F-number on the reduction side of the relay optical system 6B is Fn, and the magnification of the relay optical system 6B is E, the data of the relay optical system 6B is as follows.

[0108] Yb 8.499mm Length 195.549mm LA 117.711mm Fn 1.53 E 1.53

[0109] The lens data of the relay optical system 6B is as follows. Surface numbers are assigned in order from the magnification side to the reduction side. The symbols are those of the magnification side image forming surface, the first plane mirror, the lens, the second plane mirror, and the reduction side image forming surface. The "*" next to the lens surface number indicates that the surface is aspheric. R is the radius of curvature. D is the axial surface spacing. Y is the effective radius. The units of R, D, and Y are mm.

[0110] Code Surface number RD Glass material Refraction / Reflection Y 60A 0 0.00000 26.831800 Refraction 13.0186 66 1 0.00000 -22.168200 Reflection 28.9460 L1 2 160.00000 -4.049038 NBFD10_HOYA Refraction 21.0620 3 70.13655 -22.000000 Refraction 21.3930 67 4 0.00000 22.500000 Reflection 31.8450 L2 5 74.51888 7.645917 TAFD5F_HOYA Refraction 22.7520 6 -127.66049 0.100000 Refraction 22.4810 L3 7 23.12883 11.320403 TAFD5F_HOYA Refraction 17.8530 L4 8 7100.87695 1.900000 FD60W_HOYA Refraction 15.7020 9 14.01950 4.019656 Refraction 10.6400 L5 *10 25.85743 1.405542 MTAFD51_HOYA Refraction 10.5960 *11 82.03475 0.600000 Refraction 10.3320 L6 *12 60.86701 0.805000 MCFD80_HOYA Refraction 10.1320 *13 14.80852 2.391067 Refraction 9.6110 65 14 0.00000 3.541583 Refraction 9.6000 L7 15 -26.07564 7.416302 TAFD5F_HOYA Refraction 10.0960 L8 16 -13.40000 1.900000 FDS90_HOYA Refraction 11.3050 17 -21.43281 12.801483 Refraction 12.8030 L9 18 -21.82517 8.261107 NBFD13_HOYA Refraction 14.2000 19 -23.57697 0.100000 Refraction 16.9120 L10 20 36.85821 4.954069 TAFD5F_HOYA Refraction 17.1140 21 132.73720 28.837816 Refraction 16.7120 60B 22 0.00000 0.000000 Refraction 8.4970

[0111] Face number 10 11 12 13 Conic constant -1.258405E+00 3.594804E+01 2.323815E+01 1.236475E-01 4th order coefficient -9.420159E-05 -1.503907E-04 Sixth order coefficient 2.234791E-09 0 8th order coefficient 0 0 10th order coefficient 0 0

[0112] When the maximum image height at the enlargement-side image forming surface 60A and the reduction-side image forming surface 60B is 1, the angle of the central ray of each light beam at the enlargement-side image forming surface 60A relative to the optical axis M1, and the angle of the central ray of each light beam at the reduction-side image forming surface 60B relative to the optical axis M2 are as follows:

[0113] Image height Magnification side image plane Reduction side image plane 1 1.661 1.927 0.9 1.606 1.834 0.85 1.563 1.773 0.75 1.452 1.628 0.5 1.057 1.162 0 0.000 0.000

[0114] Here, in the relay optical system 6B of this embodiment, if the largest air spacing is L1, the effective diameter of the smaller of the two imaging surfaces, the lens and the enlargement-side image surface or the reduction-side image surface adjacent to the largest air spacing, is D1, the second largest air spacing is L2, and the effective diameter of the smaller of the two imaging surfaces, the lens and the enlargement-side image surface or the reduction-side image surface adjacent to the second largest air spacing, is D2, the following conditional formula is satisfied. D1 <L1 (1) D2 <L2 (2)

[0115] In this embodiment, the largest air gap L1 is provided between the magnification-side imaging surface 60A and the lens L1. The effective diameter D1 is the effective diameter of the magnification-side imaging surface 60A adjacent to the largest air gap L1. The second largest air gap L2 is provided between the lens L1 and the lens L2. The effective diameter D2 is the effective diameter of the lens L1 adjacent to the second largest air gap L2. The specific numerical values ​​are as follows:

[0116] D1 26.0372mm L1 49.0000mm D2 42.7840mm L2 44.5000mm Therefore, the relay optical system 6B of this embodiment satisfies the conditional expressions (1) and (2).

[0117] (Action and effect) The relay optical system 6B of the embodiment 3 can obtain the same effects as those of the embodiment 1. Fig. 7 is a diagram showing the MTF on the reduction side of the relay optical system 6B of the embodiment 3. Comparing Fig. 7 with Fig. 3, it can be seen that the relay optical system 6B of this embodiment has higher resolution than the relay optical system of the comparative example, and therefore has higher optical performance.

[0118] [Embodiment 4] FIG. 8 is a ray diagram of the relay optical system 6C of the fourth embodiment. As shown in FIG. 8, the relay optical system 6C connects the enlargement-side image forming surface 60A and the reduction-side image forming surface 60B obtained by reducing the enlargement-side image forming surface 60A. The relay optical system 6 includes, in the order of light passing from the enlargement side to the reduction side, a first lens group G1 having a positive power and composed of a plurality of lenses, a second lens group G2 having a negative power and composed of an aperture 65 and one negative lens, and a third lens group G3 having a positive power and composed of a plurality of lenses. The first lens group G1, the second lens group G2, and the third lens group G3 are arranged along the second optical axis M of the relay optical system 6. In this embodiment, the optical axis M1 of the enlargement-side image forming surface 60A and the optical axis M2 of the reduction-side image forming surface 60B are linearly aligned with the second optical axis M of the relay optical system 6.

[0119] The first lens group G1 consists of four lenses L1 to L4. L1 to L4 are arranged in this order from the enlargement side to the reduction side. Lens L1 has positive power. Lens L1 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. Lens L2 has positive power. Lens L2 has convex shapes on the enlargement side and reduction side surfaces. Lens L3 has positive power. Lens L3 has convex shapes on the enlargement side and reduction side surfaces. Lens L4 has negative power. Lens L4 has concave shapes on the enlargement side and reduction side surfaces. Lens L3 and lens L4 are cemented together to form cemented lens L21.

[0120] The second lens group G2 is composed of one lens L5 and an aperture 65. The lens L5 and the aperture 65 are arranged in this order from the enlargement side to the reduction side. The lens L5 (negative lens) has negative power. The lens L5 has a convex shape on the enlargement side surface and a concave shape on the reduction side surface. The lens L5 has aspheric shapes on the enlargement side and reduction side surfaces. Here, among the lenses of the first lens group G1, the second lens group G2, and the third lens group G3, the effective radius of the lens L5 is the smallest.

[0121] The third lens group G3 is composed of four lenses, lens L6 to lens L9. Lenses L6 to L9 are arranged in this order from the enlargement side to the reduction side. Lens L6 has negative power. Lens L7 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. Lens L7 has positive power. Lens L7 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. Lens L8 has positive power. Lens L8 has a concave shape on the enlargement side surface and a convex shape on the reduction side surface. Lens L9 has positive power. Lens L9 has convex shapes on the enlargement side and reduction side surfaces. Lenses L6 and L7 are cemented together to form cemented lens L22.

[0122] The number of lenses in the first lens group G1 and the number of lenses in the third lens group G3 are the same, four. The arrangement of the lens powers of the lenses L1 to L4 in the first lens group G1 arranged from the enlargement side to the reduction side is the same as the arrangement of the lens powers of the lenses L9 to L6 in the third lens group G3 arranged from the reduction side to the enlargement side. Specifically, the arrangement of the lens powers of the lenses L1 to L4 in the first lens group G1 is positive, positive, positive, negative, from the enlargement side to the reduction side. The arrangement of the lens powers of the lenses L9 to L6 in the third lens group G3 is positive, positive, positive, negative, from the reduction side to the enlargement side.

[0123] The enlargement side and reduction side of the relay optical system 6C are telecentric. In this embodiment, the angle between the central ray of each light beam and the optical axis M1, M2 is within ±2°.

[0124] If the maximum image height on the reduction-side image plane 60B of the relay optical system 6C is Yb, the total length of the relay optical system 6C is TL, the lens length of the relay optical system 6C is LA, the F-number on the reduction side of the relay optical system 6C is Fn, and the magnification of the relay optical system 6C is E, the data of the relay optical system 6C is as follows.

[0125] Yb 8.499mm Length 168.000mm LA 81.787mm Fn 1.64 E 1.53

[0126] The lens data of relay optical system 6C is as follows. Surface numbers are assigned in order from the magnification side to the reduction side. The symbols indicate the magnification side image forming surface, lens, and reduction side image forming surface. An "*" next to the lens surface number indicates that the surface is aspheric. R is the radius of curvature. D is the axial surface spacing. Y is the effective radius. R, D, and Y are in mm.

[0127] Code Surface number RD Glass material Refraction / Reflection Y 60A 0 0.00000 45.212882 Refraction 13.0186 L1 1 -184.09700 4.100000 FDS90_HOYA Refraction 19.9480 2 -62.88502 10.166130 Refraction 20.2050 L2 3 42.01633 6.879150 TAFD5F_HOYA Refraction 19.6120 4 -2625.89736 0.370342 Refraction 19.1210 L3 5 22.31374 9.520045 LAC14_HOYA Refraction 15.6100 L4 6 -149.53242 1.500000 FF8_HOYA Refraction 13.8930 7 12.46324 8.511899 Refraction 9.6350 L5 *8 48.67992 3.652066 BSC7_HOYA Refraction 8.4880 *9 15.14022 1.597311 Refraction 7.9300 65 10 0.00000 7.267946 Refraction 7.6000 L6 11 -45.52784 11.124290 TAC8_HOYA Refraction 12.0110 L7 12 -17.50000 1.500000 FDS90_HOYA Refraction 14.5630 13 -36.45624 0.100000 Refraction 17.3600 L8 14 -58.12613 7.525796 TAC8_HOYA Refraction 18.2860 15 -25.29455 1.736639 Refraction 19.1190 L9 16 54.32842 6.235505 TAFD5F_HOYA Refraction 20.3670 17 -598.53650 41.000000 Refraction 20.1000 60B 18 0.00000 0.000000 Refraction 8.4940

[0128] Face number 8 9 Conic constant -4.328137E+00 -3.211675E+00 4th order coefficient -1.372099E-04 -3.533897E-05 6th order coefficient 1.782276E-07 -7.351476E-09 8th order coefficient -1.071556E-09 4.050635E-10 10th order coefficient -8.726952E-13 0

[0129] When the maximum image height at the enlargement-side image forming surface 60A and the reduction-side image forming surface 60B is 1, the angle of the central ray of each light beam at the enlargement-side image forming surface 60A relative to the optical axis M1, and the angle of the central ray of each light beam at the reduction-side image forming surface 60B relative to the optical axis M2 are as follows:

[0130] Image height Magnification side image plane Reduction side image plane 1 1.698 1.915 0.9 1.658 1.889 0.85 1.618 1.852 0.75 1.509 1.740 0.5 1.101 1.288 0 0.000 0.000

[0131] Here, in the relay optical system 6C of this embodiment, if the largest air spacing is L1, the effective diameter of the smaller of the two imaging surfaces, the lens and the enlargement-side image surface or the reduction-side image surface adjacent to the largest air spacing, is D1, the second largest air spacing is L2, and the effective diameter of the smaller of the two imaging surfaces, the lens and the enlargement-side image surface or the reduction-side image surface adjacent to the second largest air spacing, is D2, the following conditional formula is satisfied. D1 <L1 (1) D2 <L2 (2)

[0132] In this embodiment, the largest air gap L1 is provided between the enlargement-side imaging surface 60A and the lens L1. The effective diameter D1 is the effective diameter of the enlargement-side imaging surface 60A adjacent to the largest air gap L1. The second largest air gap L2 is provided between the lens L9 and the reduction-side imaging surface 60B. The effective diameter D2 is the effective diameter of the reduction-side imaging surface 60B adjacent to the second largest air gap L2. The specific numerical values ​​are as follows.

[0133] D1 26.0372mm L1 45.2129mm D2 16.9980mm L2 41.0000mm Therefore, the relay optical system 6C of this embodiment satisfies the conditional expressions (1) and (2).

[0134] (Action and effect) In this embodiment, the second lens group G2 is composed of an aperture 65 and one negative lens L5. Even with this configuration, the relay optical system 6C of the fourth embodiment can achieve the same effects as those of the first embodiment. FIG. 9 is a diagram showing the MTF on the reduction side of the relay optical system 6C of the fourth embodiment. Comparing FIG. 9 with FIG. 3, it can be seen that the relay optical system 6C of this embodiment has higher resolution than the relay optical system of the comparative example, and therefore has higher optical performance. Note that the relay optical system 6C of this embodiment may include a first plane mirror 66 and a second plane mirror 67, as in the first embodiment.

[0135] (Other Examples) In the third embodiment, the second lens group G2 is composed of the aperture 65 and the negative lens L5, which is a single lens, but the single negative lens is not limited to a single lens. The single negative lens may be a cemented lens having negative power and formed by cementing a plurality of lenses together. In this way, the chromatic aberration of magnification of the relay optical system 6 can be suppressed by the single cemented lens.

[0136] The relay optical system 6 of the above embodiment is not limited to being used in a projector, but can be used in devices such as an exposure machine or a stepper that uses an optical system that connects an enlargement-side image forming surface and a reduction-side image forming surface that is a reduction of the enlargement-side image forming surface.

[0137] [Summary of this disclosure] The following is a summary of this disclosure.

[0138] (Appendix 1) In a relay optical system that connects a magnification-side image-forming surface and a reduction-side image-forming surface that is a reduced version of the magnification-side image-forming surface, the first lens group having positive power and composed of a plurality of lenses, a second lens group having negative power including a diaphragm and at least one negative lens, and a third lens group having positive power and composed of a plurality of lenses, in that order of passage of a light ray from the enlargement side to the reduction side; the number of lenses in the first lens group is the same as the number of lenses in the third lens group, an arrangement of the lens powers of the plurality of lenses in the first lens group arranged from the enlargement side to the reduction side is the same as an arrangement of the lens powers of the plurality of lenses in the third lens group arranged from the reduction side to the enlargement, A relay optical system, wherein the enlargement side and the reduction side are each telecentric.

[0139] As a result, the lens configuration of the first lens group arranged from the enlargement side to the reduction side and the lens configuration of the third lens group arranged from the reduction side to the enlargement are symmetrical, so that various aberrations occurring in the first lens group can be cancelled by the third lens group. As a result, the optical performance of the relay optical system can be improved. In addition, since both sides of the relay optical system are telecentric, the installation accuracy required when incorporating the relay optical system into an apparatus is not as strict as in a relay optical system in which both sides are not telecentric, and the arrangement is easy.

[0140] (Appendix 2) the first lens group includes, in order from the enlargement side to the reduction side, two positive lenses and a cemented lens, 2. The relay optical system according to claim 1, wherein the third lens group has, in order from the reduction side to the enlargement side, two positive lenses and a cemented lens.

[0141] As a result, since the first lens group and the third lens group each have a cemented lens, the lateral chromatic aberration occurring in the first lens group can be effectively cancelled by the third lens group. Also, since the first lens group and the third lens group each have two positive lenses, the overall length of the relay optical system can be shortened.

[0142] (Appendix 3) 3. The relay optical system described in claim 1 or 2, wherein the lens having the smallest effective diameter among the lenses in the first lens group, the second lens group, and the third lens group has an aspheric shape.

[0143] In this case, in the lens with the smallest effective diameter, all light rays pass through the lens in a spread state. Therefore, if the lens with the smallest effective diameter has an aspheric shape, various aberrations can be effectively improved for all image heights. This makes it possible to improve the optical performance of the relay optical system.

[0144] (Appendix 4) 4. The relay optical system according to claim 1, wherein the second lens group includes the diaphragm and one of the negative lenses.

[0145] (Appendix 5) The relay optical system described in any one of Appendix 1 to 4, characterized in that, in the relay optical system, when the largest air spacing is L1, the effective diameter of the smaller of the two image forming surfaces, between the lens and one of the enlargement-side image forming surface and the reduction-side image forming surface adjacent to the largest air spacing, is D1, the second largest air spacing is L2, and the effective diameter of the smaller of the two image forming surfaces, between the lens and the other of the enlargement-side image forming surface and the reduction-side image forming surface adjacent to the second largest air spacing, is D2, the following conditional formula is satisfied: D1 <L1 D2 <L2

[0146] This makes it easy to change the optical path to any angle at the largest and second largest air gaps, improving the degree of freedom in the layout of the relay optical system. Also, it becomes easy to control the light beam without having to set a large refraction angle for the lenses adjacent to the largest and second largest air gaps.

[0147] (Appendix 6) The relay optical system described in any one of Appendix 1 to 4, characterized in that, in the relay optical system, when the largest air spacing is L1, the effective diameter of the lens adjacent to the largest air spacing and one of the enlargement-side image forming surface and the reduction-side image forming surface, which has a smaller effective diameter, is D1, the second largest air spacing is L2, and the effective diameter of the two lenses adjacent to the second largest air spacing, which has a smaller effective diameter, is D2, the following conditional formula is satisfied: D1 <L1 D2 <L2

[0148] This makes it easy to change the optical path to any angle at the largest and second largest air gaps, improving the degree of freedom in the layout of the relay optical system. Also, it becomes easy to control the light beam without having to set a large refraction angle for the lenses adjacent to the largest and second largest air gaps.

[0149] (Appendix 7) a first plane mirror disposed at the largest air gap and a second plane mirror disposed at the second largest air gap; the largest air gap is provided between the enlargement-side image-forming surface and the first lens group, 6. The relay optical system according to claim 5, wherein the second largest air gap is provided between the third lens group and the reduction-side image plane.

[0150] This makes it easy to arrange the first plane mirror and the second plane mirror in the relay optical system.

[0151] (Appendix 8) a first plane mirror disposed at the largest air gap and a second plane mirror disposed at the second largest air gap; the largest air gap is provided between the enlargement-side image-forming surface and the first lens group, 7. The relay optical system according to claim 6, wherein the second largest air gap is provided inside the first lens group.

[0152] This makes it easy to arrange the first plane mirror and the second plane mirror in the relay optical system.

[0153] (Appendix 9) the first plane mirror and the second plane mirror each refract a light beam; the optical axis of the enlargement-side image-forming surface and the optical axis of the reduction-side image-forming surface are parallel to each other; 9. The relay optical system according to claim 7 or 8, wherein the direction of incidence of a light ray incident on the enlargement-side image-forming surface is opposite to the direction of incidence of a light ray incident on the reduction-side image-forming surface.

[0154] This allows the relay optical system to efficiently bend the optical path by 180 degrees.

[0155] (Appendix 10) A projector including a relay optical system according to any one of claims 1 to 6, A light source; a separation optical system that separates the white light emitted from the light source into a first color light in a first wavelength band including blue light and another color light in a wavelength band longer than that of the first color light; a first light modulation element that modulates the first color light separated by the separation optical system; a second light modulation element that modulates the other color light separated by the separation optical system; the relay optical system, in which the first light modulation element is disposed on the enlargement-side image forming plane and the light beam width of the first color light modulated by the first light modulation element is reduced on the reduction-side image forming plane; a color combining prism that outputs a combined light obtained by combining the first color light whose luminous flux width has been reduced by the relay optical system and the other color light modulated by the second light modulation element; a projection optical system that projects the combined light emitted from the color combining prism; having an effective area of ​​the first light modulation element is larger than an effective area of ​​the second light modulation element; the relay optical system includes a first plane mirror disposed between the enlargement-side image-forming surface and the first lens group, and a second plane mirror disposed between the third lens group and the reduction-side image-forming surface, the first plane mirror and the second plane mirror each refract a light beam; the optical axis of the enlargement-side image-forming surface is parallel to the optical axis of the reduction-side image-forming surface, A projector, characterized in that an incident direction of the first color light that is incident on the enlargement-side image forming surface is a direction opposite to an exit direction of the first color light that is exited from the reduction-side image forming surface.

[0156] This makes it possible to place a relay optical system in the projector that bends the optical path by 180 degrees.

[0157] (Appendix 11) A projector including a relay optical system according to any one of claims 1 to 6, A light source; a separation optical system that separates the white light emitted from the light source into a first color light in a first wavelength band including blue light and another color light in a wavelength band longer than that of the first color light; a first light modulation element that modulates the first color light separated by the separation optical system; a second light modulation element that modulates the other color light separated by the separation optical system; the relay optical system, in which the first light modulation element is disposed on the enlargement-side image forming plane and the light beam width of the first color light modulated by the first light modulation element is reduced on the reduction-side image forming plane; a color combining prism that outputs a combined light obtained by combining the first color light whose luminous flux width has been reduced by the relay optical system and the other color light modulated by the second light modulation element; a projection optical system that projects the combined light emitted from the color combining prism; having an effective area of ​​the first light modulation element is larger than an effective area of ​​the second light modulation element; the relay optical system includes a first plane mirror disposed between the magnification-side image-forming surface and the first lens group, and a second plane mirror disposed inside the first lens group, the first plane mirror and the second plane mirror each refract a light beam; the optical axis of the enlargement-side image-forming surface is parallel to the optical axis of the reduction-side image-forming surface, A projector, characterized in that an incident direction of the first color light that is incident on the enlargement-side image forming surface is a direction opposite to an exit direction of the first color light that is exited from the reduction-side image forming surface.

[0158] This makes it possible to place a relay optical system in the projector that bends the optical path by 180 degrees. [Explanation of symbols]

[0159] 1...light source, 2...illumination optical system, 3...separation optical system, 5...polarizing plate, 6, 6A, 6B, 6C...relay optical system, 7...light modulation element, 8...color synthesis prism, 9...projection optical system, 10...control unit, 11...reflecting mirror, 12...lens, 13...lens, 14...reflecting mirror, 15...reflecting mirror, 16...reflecting mirror, 17...reflecting mirror, 19...relay lens, 21...multi-lens, 22...polarizing beam splitter, 23...multi-lens, 24...relay lens, 31...first dichroic mirror, 32...second dichroic mirror, 60...reflecting surface, 60A...magnification side image forming surface, 60B...reduction side image forming surface, 65...diaphragm, 66...first reflector a first reflecting mirror, 67...second reflecting mirror, 71...first light modulation element, 72...third light modulation element, 73...fourth light modulation element, 75...entrance-side polarizing plate, 76...exiting-side polarizing plate, 81...first surface, 82...second surface, 83...third surface, 84...fourth surface, 100, 100A, 100B...projector, G1...first lens group, G2...second lens group, G3...third lens group, L1 to L10...lenses, L21, L22...cemented lenses, LD...exiting light, LE...combined light, LB...first color light, LG...second color light, LR...third color light, LC...other color light, N...first optical axis, M...second optical axis, M1...optical axis of enlargement-side image forming surface, M2...optical axis of reduction-side image forming surface.

Claims

1. In a relay optical system that connects a magnification-side image-forming surface and a reduction-side image-forming surface that is a reduced version of the magnification-side image-forming surface, the optical system includes, in order of passage of a light ray from the enlargement side to the reduction side, a first lens group having positive power and composed of a plurality of lenses, a second lens group having negative power including a diaphragm and at least one negative lens, and a third lens group having positive power and composed of a plurality of lenses; the number of lenses in the first lens group is the same as the number of lenses in the third lens group, an arrangement of the lens powers of the plurality of lenses in the first lens group arranged from the enlargement side to the reduction side is the same as an arrangement of the lens powers of the plurality of lenses in the third lens group arranged from the reduction side to the enlargement, A relay optical system, wherein the enlargement side and the reduction side are each telecentric.

2. the first lens group includes, in order from the enlargement side to the reduction side, two positive lenses and a cemented lens, 2. The relay optical system according to claim 1, wherein the third lens group comprises, in order from the reduction side to the enlargement side, two positive lenses and a cemented lens.

3. 3. The relay optical system according to claim 1, wherein the lens having the smallest effective diameter among the lenses in the first lens group, the second lens group, and the third lens group has an aspheric shape.

4. 2. The relay optical system according to claim 1, wherein the second lens group comprises the diaphragm and one of the negative lenses.

5. The relay optical system according to claim 1, characterized in that, in the relay optical system, when the largest air spacing is L1, the effective diameter of the smaller of the two image forming surfaces, between the lens and one of the enlargement-side image forming surface and the reduction-side image forming surface adjacent to the largest air spacing, is D1, the second largest air spacing is L2, and the effective diameter of the smaller of the two image forming surfaces, between the lens and the other of the enlargement-side image forming surface and the reduction-side image forming surface adjacent to the second largest air spacing, is D2, the following conditional expression is satisfied. D1<L1 D2<L2

6. The relay optical system according to claim 1, characterized in that, in the relay optical system, when the largest air spacing is L1, the effective diameter of the lens adjacent to the largest air spacing and one of the enlargement-side image forming surface and the reduction-side image forming surface, which has a smaller effective diameter, is D1, the second largest air spacing is L2, and the effective diameter of the two lenses adjacent to the second largest air spacing, which has a smaller effective diameter, is D2, the following conditional expression is satisfied. D1<L1 D2<L2

7. a first plane mirror disposed at the largest air gap and a second plane mirror disposed at the second largest air gap; the largest air gap is provided between the enlargement-side image-forming surface and the first lens group, 6. The relay optical system according to claim 5, wherein the second largest air gap is provided between the third lens group and the reduction-side image-forming surface.

8. a first plane mirror disposed at the largest air gap and a second plane mirror disposed at the second largest air gap; the largest air gap is provided between the enlargement-side image-forming surface and the first lens group, 7. The relay optical system according to claim 6, wherein the second largest air gap is provided inside the first lens group.

9. the first plane mirror and the second plane mirror each refract a light beam; the optical axis of the enlargement-side image-forming surface and the optical axis of the reduction-side image-forming surface are parallel to each other; 9. The relay optical system according to claim 7, wherein the direction of incidence of a light ray incident on said enlargement-side image-forming surface is opposite to the direction of incidence of a light ray incident on said reduction-side image-forming surface.

10. A projector comprising the relay optical system according to claim 1 , A light source; a separation optical system that separates the white light emitted from the light source into a first color light in a first wavelength band including blue light and another color light in a wavelength band longer than that of the first color light; a first light modulation element that modulates the first color light separated by the separation optical system; a second light modulation element that modulates the other color light separated by the separation optical system; the relay optical system, in which the first light modulation element is disposed on the enlargement-side image forming plane and the light beam width of the first color light modulated by the first light modulation element is reduced on the reduction-side image forming plane; a color combining prism that outputs a combined light obtained by combining the first color light whose luminous flux width has been reduced by the relay optical system and the other color light modulated by the second light modulation element; a projection optical system that projects the combined light emitted from the color combining prism; having an effective area of ​​the first light modulation element is larger than an effective area of ​​the second light modulation element; the relay optical system includes a first plane mirror disposed between the enlargement-side image-forming surface and the first lens group, and a second plane mirror disposed between the third lens group and the reduction-side image-forming surface, the first plane mirror and the second plane mirror each refract a light beam; the optical axis of the enlargement-side image-forming surface is parallel to the optical axis of the reduction-side image-forming surface, a direction in which the first color light enters the enlargement-side image forming surface and a direction in which the first color light exits the reduction-side image forming surface are opposite to each other;

11. A projector comprising the relay optical system according to claim 1 , A light source; a separation optical system that separates the white light emitted from the light source into a first color light in a first wavelength band including blue light and another color light in a wavelength band longer than that of the first color light; a first light modulation element that modulates the first color light separated by the separation optical system; a second light modulation element that modulates the other color light separated by the separation optical system; the relay optical system, in which the first light modulation element is disposed on the enlargement-side image forming plane and the light beam width of the first color light modulated by the first light modulation element is reduced on the reduction-side image forming plane; a color combining prism that outputs a combined light obtained by combining the first color light whose luminous flux width has been reduced by the relay optical system and the other color light modulated by the second light modulation element; a projection optical system that projects the combined light emitted from the color combining prism; having an effective area of ​​the first light modulation element is larger than an effective area of ​​the second light modulation element; the relay optical system includes a first plane mirror disposed between the enlargement-side image-forming surface and the first lens group, and a second plane mirror disposed inside the first lens group, the first plane mirror and the second plane mirror each refract a light beam; the optical axis of the enlargement-side image-forming surface is parallel to the optical axis of the reduction-side image-forming surface, a direction in which the first color light enters the enlargement-side image forming surface and a direction in which the first color light exits the reduction-side image forming surface are opposite to each other;

Images