Optical system and projector

Abstract

To provide an optical system that can make a brighter periphery of an enlarged image to be projected.SOLUTION: An optical system comprises a first optical element. The first optical element has a first transmission surface, a first reflection surface that is located on a reduction side of the first transmission surface, and a second transmission surface that is located on a reduction side of the first reflection surface. The first transmission surface has power. A light beam passing through between the first transmission surface and the first reflection surface includes peripheral light that is inclined in a direction separating from an enlargement-side conjugate surface as approaching the first transmission surface. Between the first transmission surface and the enlargement-side conjugate surface, the peripheral light is inclined in a direction approaching the enlargement-side conjugate surface as separating from the first transmission surface.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] A projection optical system including an optical element having an exit surface, a reflecting surface, and an entrance surface is described in Patent Document 1. In the projection optical system described in Patent Document 1, the entrance surface of the optical element coincides with the reduction-side conjugate surface. Therefore, when such a projection optical system is installed in a projector, a spatial modulator such as a liquid crystal panel is installed on the entrance surface of the optical element. The exit surface of the optical element is a convex spherical surface that protrudes toward the magnification-side conjugate surface and faces a screen installed on the magnification-side conjugate surface. The reflecting surface of the optical element is located on the opposite side of the exit surface and the entrance surface from the magnification-side conjugate surface in the optical axis direction of the projection optical system. The reflecting surface has a concave shape that is recessed in the direction away from the magnification-side conjugate surface in the optical axis direction.

[0003] The optical element in this document is formed by bonding a first optical element and a second optical element arranged in the optical axis direction. The first optical element has an exit surface, and the second optical element has an entrance surface and a reflecting surface. The area of ​​the first optical element facing the screen is the exit surface. The area of ​​the second optical element facing away from the screen is formed with a reflective film. This reflective film constitutes the reflecting surface. Within the optical element, projected light traveling from the reflecting surface toward the exit surface passes through the bonding surface where the first optical element and the second optical element are bonded. The bonding surface is arranged perpendicular to the optical axis.

[0004] An aperture stop is provided at the cemented surface. Projection light that enters the entrance surface of the optical element from the spatial modulator side and is reflected by the reflection surface passes through the aperture stop, emerges from the exit surface, and reaches the screen. As the projection light passes through the aperture stop, a portion of the projection light is blocked by the light-blocking portion of the aperture stop. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-156714 Summary of the Invention [Problem to be solved by the invention]

[0006] The projection optical system of Patent Document 1 has an aperture stop in the optical element, so the peripheral light beam of the projection light is thinner than the light beam near the center, which results in a dark periphery of the enlarged image projected onto the screen.

[0007] Increasing the aperture diameter of the aperture diaphragm makes it possible to ensure sufficient light around the periphery of the enlarged image. However, if the aperture diameter of the aperture diaphragm is made too large, the projection light will extend beyond the area of ​​the first optical element facing the screen, preventing the peripheral light of the projection light from reaching the screen. Therefore, even if the aperture diameter of the aperture diaphragm is made large, there is a limit to how much light can be ensured around the periphery of the enlarged image. [Means for solving the problem]

[0008] In order to solve the above problems, the optical system of the present invention includes a first optical element. The first optical element has a first transmitting surface, a first reflecting surface located on the reduction side of the first transmitting surface, and a second transmitting surface located on the reduction side of the first reflecting surface. The first transmitting surface has power. Light passing between the first transmitting surface and the first reflecting surface includes peripheral light that is inclined in a direction away from the magnification-side conjugate surface as it approaches the first transmitting surface. Between the first transmitting surface and the magnification-side conjugate surface, the peripheral light is inclined in a direction approaching the magnification-side conjugate surface as it moves away from the first transmitting surface.

[0009] Another aspect of the present invention provides an optical system comprising a first optical element and a lens disposed on the magnification side of the first optical system. The first optical element has a first transmitting surface, a first reflecting surface located on the reduction side of the first transmitting surface, and a second transmitting surface located on the reduction side of the first reflecting surface. The first transmitting surface has power. A line passing between the first transmitting surface and the first reflecting surface includes peripheral light that inclines in a direction away from the magnification-side conjugate plane as it approaches the first transmitting surface. Between the first transmitting surface and the lens, the peripheral light inclines in a direction away from the magnification-side conjugate plane as it moves away from the first transmitting surface, and between the lens and the magnification-side conjugate plane, the peripheral light inclines in a direction approaching the magnification-side conjugate plane as it moves away from the lens. Another aspect of the optical system of the present invention is an optical system including a first optical element and a lens arranged on the magnification side of the first optical element, wherein the first optical element has a first transmitting surface, a first reflecting surface having an aspherical shape located on the reduction side of the first transmitting surface, and a second transmitting surface having an aspherical shape located on the reduction side of the first reflecting surface, wherein the first transmitting surface has power, and light passing between the first transmitting surface and the first reflecting surface comprises peripheral light that inclines in a direction away from the magnification side conjugate surface as it approaches the first transmitting surface, and the peripheral light inclines in a direction away from the magnification side conjugate surface as it moves away from the first transmitting surface between the first transmitting surface and the lens, and inclines in a direction approaching the magnification side conjugate surface as it moves away from the lens, between the lens and the magnification side conjugate surface.

[0010] Next, a projector of the present invention includes a light modulation element disposed on the reduction-side conjugate plane and modulating light emitted from a light source, and the above-described optical system that projects the light modulated by the light modulation element. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a projector including an optical system according to an embodiment of the present invention. [Figure 2] 1 is a ray diagram schematically illustrating the entire optical system of Example 1. FIG. [Figure 3] FIG. 2 is a ray diagram of the optical system of the first embodiment. [Figure 4] FIG. 3 is a ray diagram of the first optical system of the first embodiment. [Figure 5] FIG. 4 is a diagram showing the MTF on the enlargement side of the optical system of Example 1. [Figure 6] 1 is a spot diagram of the optical system of Example 1. [Figure 7] FIG. 10 is a ray diagram schematically illustrating the entire optical system of Example 2. [Figure 8] FIG. 10 is a ray diagram of the optical system of Example 2. [Figure 9] FIG. 10 is a ray diagram of the first optical system of Example 2. [Figure 10]FIG. 10 is a diagram showing the MTF on the enlargement side of the optical system of Example 2. [Figure 11] 10 is a spot diagram of the optical system of Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0012] An optical system and a projector according to an embodiment of the invention will be described below with reference to the drawings.

[0013] (projector) 1 is a diagram showing a schematic configuration of a projector equipped with an optical system 3 of the present invention. As shown in Fig. 1, the projector 1 is equipped with an image forming unit 2 that generates a projection image to be projected onto a screen S, an optical system 3 that enlarges the projection image and projects the enlarged image onto the screen S, and a control unit 4 that controls the operation of the image forming unit 2.

[0014] (Image forming unit and control unit) The image forming unit 2 includes a light source 10, a first integrator lens 11, a second integrator lens 12, a polarization conversion element 13, and a superimposing lens 14. The light source 10 is, for example, an ultra-high pressure mercury lamp, a solid-state light source, or the like. The first integrator lens 11 and the second integrator lens 12 each have a plurality of lens elements arranged in an array. The first integrator lens 11 splits the light beam from the light source 10 into a plurality of beams. Each lens element of the first integrator lens 11 focuses the light beam from the light source 10 near each lens element of the second integrator lens 12.

[0015] Polarization conversion element 13 converts the light from second integrator lens 12 into predetermined linearly polarized light. Superimposing lens 14 superimposes the images of each lens element of first integrator lens 11 via second integrator lens 12 onto the display areas of liquid crystal panels 18R, 18G, and 18B, which will be described later.

[0016] The image forming unit 2 also includes a first dichroic mirror 15, a reflecting mirror 16, a field lens 17R, and a liquid crystal panel 18R. The first dichroic mirror 15 reflects R light, which is a portion of the light incident from the superimposing lens 14, and transmits G light and B light, which are also portions of the light incident from the superimposing lens 14. The R light reflected by the first dichroic mirror 15 passes through the reflecting mirror 16 and the field lens 17R and is incident on the liquid crystal panel 18R. The liquid crystal panel 18R is a light modulation element. The liquid crystal panel 18R modulates the R light in accordance with an image signal to form a red projection image.

[0017] The image forming unit 2 further includes a second dichroic mirror 21, a field lens 17G, and a liquid crystal panel 18G. The second dichroic mirror 21 reflects G light, which is a portion of the light from the first dichroic mirror 15, and transmits B light, which is a portion of the light from the first dichroic mirror 15. The G light reflected by the second dichroic mirror 21 passes through the field lens 17G and enters the liquid crystal panel 18G. The liquid crystal panel 18G is a light modulation element. The liquid crystal panel 18G forms a green projection image by modulating the G light in accordance with an image signal.

[0018] The image forming unit 2 also includes a relay lens 22, a reflecting mirror 23, a relay lens 24, a reflecting mirror 25, a field lens 17B, a liquid crystal panel 18B, and a cross dichroic prism 19. The B light transmitted through the second dichroic mirror 21 passes through the relay lens 22, the reflecting mirror 23, the relay lens 24, the reflecting mirror 25, and the field lens 17B, and is incident on the liquid crystal panel 18B. The liquid crystal panel 18B is a light modulation element. The liquid crystal panel 18B forms a blue projection image by modulating the B light in accordance with an image signal.

[0019] Liquid crystal panels 18R, 18G, and 18B surround cross dichroic prism 19 on three sides. Cross dichroic prism 19 is a prism for light synthesis, and generates a projection image by synthesizing the light modulated by each of liquid crystal panels 18R, 18G, and 18B.

[0020] The optical system 3 projects the projection image synthesized by the cross dichroic prism 19 onto the screen S in an enlarged scale.

[0021] The control unit 4 includes an image processing unit 6 to which external image signals such as video signals are input, and a display driving unit 7 that drives the liquid crystal panels 18R, 18G, and 18B based on the image signals output from the image processing unit 6.

[0022] Image processing unit 6 converts an image signal input from an external device into an image signal including the gradation of each color. Display drive unit 7 operates liquid crystal panels 18R, 18G, and 18B based on the projection image signals of each color output from image processing unit 6. As a result, image processing unit 6 displays a projection image corresponding to the image signal on liquid crystal panels 18R, 18G, and 18B.

[0023] Example 1 Fig. 2 is a ray diagram schematically illustrating the entire optical system of Example 1. Fig. 3 is a ray diagram for optical system 3A of Example 1. Fig. 4 is a ray diagram for the first optical system of Example 1. As shown in Figs. 2 and 3, a liquid crystal panel 18 is disposed on the reduction-side conjugate plane of optical system 3.

[0024] For convenience, in the following description, three mutually perpendicular axes are referred to as the X-axis, Y-axis, and Z-axis. The width direction of the screen S, which is the magnification-side conjugate plane, is referred to as the X-axis direction, the vertical direction of the screen S as the Y-axis direction, and the direction perpendicular to the screen S as the Z-axis direction. In the Y-axis direction, the direction above the screen S is referred to as the Y1 direction, and the direction below the screen S as the Y2 direction. In the Z-axis direction, the side where the screen S is located is referred to as the Z1 direction, and the opposite side is referred to as the Z2 direction.

[0025] As shown in FIG. 2, the optical system 3A of this example has, in order from the enlargement side to the reduction side, a first optical system 31 and a second optical system 32. The first optical system 31 is a reflective optical system. The optical axis M of the first optical system 31 extends along the Z-axis direction. That is, the optical axis M of the first optical system 31 is perpendicular to the screen S. The second optical system 32 is a refractive optical system. The optical axis N of the second optical system 32 extends along the Y-axis direction. The screen S is located in the Z1 direction of the optical axis N.

[0026] As shown in FIGS. 3 and 4 , the first optical system 31 includes a first optical element 33 and a second optical element 34. The first optical element 33 and the second optical element 34 are arranged in this order from the enlargement side to the reduction side. The optical axis of the first optical element 33 and the optical axis of the third transmitting surface 51 of the second optical element 34 are substantially parallel to each other and extend along the Z-axis direction. In this example, the optical axis of the first optical element 33 and the optical axis of the third transmitting surface 51 of the second optical element 34 coincide with each other. In other words, the optical axis M of the first optical system 31 is the optical axis of the first optical element 33 and the optical axis of the third transmitting surface 51 of the second optical element 34.

[0027] The first optical element 33 consists of one optical element. The first optical element 33 is located in the Z2 direction of the second optical element 34. The first optical element 33 has a first transmitting surface 41, a first reflecting surface 42 located on the reduction side of the first transmitting surface 41, and a second transmitting surface 43 located on the reduction side of the first reflecting surface 42.

[0028] The first transmitting surface 41 has a convex shape facing the Y1 direction. A first optical axis of the first transmitting surface 41 coincides with the optical axis M of the first optical system 31. The first transmitting surface 41 has a shape that is rotationally symmetric about the first optical axis of the first transmitting surface 41. The first transmitting surface 41 has positive power. The first reflecting surface 42 is located in the Y2 direction of the first transmitting surface 41. The first reflecting surface 42 has a concave shape that is recessed in the Z2 direction. A second optical axis of the first reflecting surface 42 coincides with the optical axis M of the first optical system 31. The first reflecting surface 42 has a shape that is rotationally symmetric about the second optical axis of the first reflecting surface 42. The first reflecting surface 42 has negative power. The first reflecting surface 42 is formed by providing a reflective coating layer on the outer surface of the first optical element 33 in the Z2 direction. A third optical axis of the second transmitting surface 43 coincides with the optical axis M of the first optical system 31. The second transmitting surface 43 has a shape that is rotationally symmetric about the third optical axis of the second transmitting surface 43. The second transmitting surface 43 has negative power. The first reflecting surface 42 and the second transmitting surface 43 have aspherical shapes.

[0029] The second optical element 34 is composed of a single optical element. The second optical element 34 includes a third transmitting surface 51, a second reflecting surface 52 located on the reduction side of the third transmitting surface 51, and a fourth transmitting surface 53 located on the reduction side of the second reflecting surface 52. The third transmitting surface 51 faces the second transmitting surface 43 in the Z-axis direction. The third transmitting surface 51 has a convex shape facing the Z2 direction. The optical axis of the third transmitting surface 51 coincides with the optical axis M of the first optical system 31. The third transmitting surface 51 has a shape that is rotationally symmetrical about the optical axis of the third transmitting surface 51. The third transmitting surface 51 has negative power. The second reflecting surface 52 is a flat mirror with no power. The second reflecting surface 52 is inclined 45° with respect to the Y-axis and Z-axis. The second reflecting surface 52 bends the optical path by 90° between the third transmitting surface 51 and the fourth transmitting surface 53. The second reflecting surface 52 is formed by providing a reflective coating layer on the outer surface of the second optical element 34 in the Z1 direction. The fourth transmitting surface 53 faces the Y2 direction and faces the lens L12. The angle between the optical axis of the fourth transmitting surface 53 and the optical axis of the third transmitting surface 51 is 90°. That is, the angle between the optical axis of the fourth transmitting surface 53 and the optical axis M of the first optical element 33 is 90°. The optical axis of the fourth transmitting surface 53 coincides with the optical axis N of the second optical system 32. The fourth transmitting surface 53 has a shape that is rotationally symmetric about the optical axis of the fourth transmitting surface 53. The fourth transmitting surface 53 has positive power. The third transmitting surface 51 and the fourth transmitting surface 53 have aspherical shapes.

[0030] As shown in Fig. 3, the second optical system 32 includes 12 lenses L1 to L12. The lenses L1 to L12 are arranged in this order from the reduction side to the enlargement side. The lenses L2, L7, and L12 are aspherical lenses with aspherical shapes on both sides. Each lens in the first optical system 31 has a rotationally symmetric surface centered on the optical axis N.

[0031] As shown in FIG. 3, the liquid crystal panel 18, which is disposed on the reduction-side conjugate plane of the optical system 3A, forms a projected image on the Z2 side of the optical axis N. The angle θ1 formed between the optical axis M of the first optical element 33 and the optical axis N of the second optical system 32 is 90° or less. In this example, the angle θ1 is 90°. Therefore, after passing through the second optical system 32, light from the liquid crystal panel 18 side is bent 90° by the second reflecting surface 52 of the second optical element 34 and heads in the Z2 direction. The light headed in the Z2 direction is bent back in the Z1 and Y1 directions by the first reflecting surface 42 of the first optical element 33 and reaches the screen S.

[0032] 3, the optical system 3A forms an intermediate image 30 between the reduction-side conjugate surface and the magnification-side conjugate surface, the intermediate image 30 being conjugate to the reduction-side conjugate surface and the magnification-side conjugate surface. In this example, the intermediate image 30 is formed between the first reflecting surface 42 of the first optical element 33 and the second reflecting surface 52 of the second optical element 34.

[0033] 4, the light traveling between the first transmitting surface 41 and the first reflecting surface 42 includes peripheral light L that is inclined in a direction away from the screen S, which is the magnification-side conjugate surface, as it approaches the first transmitting surface 41. Between the first transmitting surface 41 and the screen S, the peripheral light L is inclined in a direction approaching the screen S as it moves away from the first transmitting surface 41. In addition, an imaginary line Q connecting the maximum effective point P of the peripheral light L on the first transmitting surface 41 and the center of curvature of the first transmitting surface 41 intersects with the first optical axis at an angle θ2 of 90° or more.

[0034] The lens data for optical system 3A is as follows. Surface numbers are assigned in order from the magnification side to the reduction side. The symbols refer to the liquid crystal panel, dichroic prism, lens, and screen. Data for surface numbers that do not correspond to the liquid crystal panel, dichroic prism, lens, and screen are dummy data. Surfaces with an * next to the surface number are aspheric. R is the radius of curvature. D is the on-axis surface spacing. nd is the refractive index. νd is the Abbe number. Y is the aperture radius. The units of R, D, and Y are mm. The lens data in this example was designed using CODE V by Synopsys.

[0035] Sign Surface No. RD nd vd Mode Y 18 0 0.00000 22.000000 Refraction 19 1 0.00000 37.300000 1.516800 64.17 Refraction 18.4130 2 0.00000 0.409841 Refraction 22.0000 L1 3 -590.67796 10.000000 1.601496 58.49 Refraction 22.0000 4 -42.72242 3.000000 Refraction 22.4270 L2 *5 -31.66863 2.000000 2.001100 28.26 Refraction 21.9910 *6 -61.15100 0.500000 Refraction 23.5070 L3 7 144.21520 2.000000 2.001000 29.13 Refraction 25.6220 8 122.54476 0.500000 Refraction 25.8240 L4 9 90.65158 7.654132 1.505040 72.69 Refraction 26.5750 10 654.66116 0.500000 Refraction 27.2070 L5 11 112.22630 2.000000 1.879323 36.94 Refraction 28.0900 12 76.00335 1.535871 Refraction 28.1060 L6 13 92.61405 20.000000 1.480772 78.39 Refraction 28.3600 14 -46.55932 80.000000 Refraction 29.1400 O 15 0.00000 78.806011 Refraction 17.0000 L7 *16 68.28008 7.570544 1.509398 56.47 Refraction 40.0000 *17 94.93422 71.132325 Refraction 34.5630 L8 18 -1518.99365 19.999983 2.002500 19.32 Refraction 43.9240 19 -155.81886 17.456943 Refraction 45.2540 L9 20 71.47955 30.000000 1.529865 45.90 Refraction 40.9460 21 -121.50056 1.883188 Refraction 37.5510 L10 22 -101.70642 2.000000 2.002700 19.32 Refraction 36.5880 23 82.52373 31.678777 Refraction 34.9860 L11 24 -105.69324 4.989296 1.437001 95.10 Refraction 39.9880 25 -89.28078 17.118289 Refraction 40.9730 L12 *26 -23.55002 8.000000 1.509398 56.47 Refraction 48.0000 *27 -165.75191 43.658778 Refraction 47.5050 34 *28 -100.00000 72.000000 1.509398 56.47 Refraction 57.2550 29 0.00000 -15.000000 1.509398 56.47 Reflection 81.6940 *30 2014.46301 -3.472339 Refraction 63.3480 33 *31 -138.80012 -64.000000 1.509398 56.47 Refraction 62.0000 *32 33.36242 0.000000 1.509398 56.47 Reflection 69.4220 33 -80.00000 0.000000 Refraction 41.5690 34 0.00000 0.000000 Refraction 1773.6130 S 35 0.00000 0.000000 Refraction 1773.6130

[0036] The aspherical coefficients are as follows:

[0037] Face number 5 6 16 17 Conic constant -1E+00 -1E+00 -1E+00 -1E+00 4th order coefficient 3.694405E-06 7.654845E-06 2.143317E-06 2.748365E-06 6th order coefficient -8.028217E-09 -6.949011E-09 1.366512E-09 1.549676E-09 8th order coefficient 6.506012E-12 8.188262E-12 -1.450751E-13 1.723083E-13 10th order coefficient -1.527956E-15 -2.860017E-15 1.382604E-16 1.058483E-16

[0038] Face number 26 27 28 30 Conic constant -1.133807E+00 -5.958633E+01 -1.074643E+01 -1.115037E+43 4th order coefficient 4.559836E-06 -4.700304E-06 2.368596E-06 -2.160545E-06 6th order coefficient -3.539447E-09 1.031617E-09 -7.978636E-10 1.808458E-09 8th order coefficient 1.671317E-12 -2.69451E-13 1.397035E-13 -3.726332E-13 10th order coefficient -2.300276E-16 5.580673E-17 -9.252121E-18 2.502569E-17

[0039] Face number 31 32 Conic constant -4.86632E+01 -1.098222E+00 4th order coefficient -2.274983E-06 -1.57618E-06 6th order coefficient 7.397958E-10 1.305372E-10 8th order coefficient 8.793892E-15 2.869818E-14 10th order coefficient -1.526278E-18 -3.836358E-18

[0040] The ray coordinates at the object plane are:

[0041] Ray number X coordinate Y coordinate 1 0 -1.38 2 0 -4.83 3 0 -8.28 4 0 -11.73 5 0 -15.18

[0042] In this example, the surface numbers 29, 33, and 34 are decentered surfaces. The parameters of the decentered surfaces are as follows:

[0043] Face number 29 Eccentricity type: Decenter and bend Parameter X 0.0000 Parameter Y 0.0000 Parameter Z 0.0000 Parameter α 45.0000

[0044] Face number 33 Eccentricity Type Global Coordinates Global Reference Plane 32 Parameter X 0.0000 Parameter Y -80.0000 Parameter Z 44.6790 Parameter α -90.0000

[0045] Face number 34 Eccentricity Type Global Coordinates Global Reference Plane 32 Parameter X 0.0000 Parameter Y 0.0000 Parameter Z 201.0000 Parameter α 0.0000

[0046] (Action and effect) In the optical system 3A of this example, the first optical element 33 located closest to the magnification side has a first transmitting surface 41, a first reflecting surface 42 located on the reduction side of the first transmitting surface 41, and a second transmitting surface 43 located on the reduction side of the first reflecting surface 42. The first transmitting surface 41 has power. In addition, in the optical system 3A of this example, light passing between the first transmitting surface 41 and the first reflecting surface 42 is provided with peripheral light L that is inclined in a direction away from the screen S, which is the magnification-side conjugate surface, as it approaches the first transmitting surface 41. Between the first transmitting surface 41 and the screen S, the peripheral light L is inclined in a direction approaching the screen S as it moves away from the first transmitting surface 41.

[0047] According to this example, within the first optical element 33, light traveling from the first reflecting surface 42 to the first transmitting surface 41 includes peripheral light L that is inclined in a direction away from the screen S as it approaches the first transmitting surface 41. Therefore, when light incident on the first optical element 33 from the reduction-side second transmitting surface 43 is turned back by the first reflecting surface 42 and travels toward the first transmitting surface 41, the peripheral light L of the light travels in a direction away from the screen S. If the peripheral light L does not reach the screen S, a problem occurs in which the periphery of the enlarged image projected onto the screen S becomes dark. In contrast, in this example, the first transmitting surface 41 has power. As a result, between the first transmitting surface 41 and the screen S, the peripheral light L is inclined in a direction approaching the screen S as it travels away from the first transmitting surface 41. In other words, the peripheral light L, which is turned back by the first reflecting surface 42 and travels within the first optical element 33 in a direction away from the screen S, travels toward the screen S via the first transmitting surface 41. Therefore, the amount of light around the periphery of the enlarged image projected onto the screen S can be ensured.

[0048] In this example, the first transmitting surface 41 has a convex shape that is rotationally symmetric about the first optical axis. When a virtual line Q is defined that connects the maximum effective point P of the peripheral light L on the first transmitting surface 41 with the center of curvature of the first transmitting surface 41, the virtual line Q intersects with the first optical axis at an angle θ of 90° or more. Therefore, in the optical system 3A of this example, even if the peripheral light L of the light reflected by the first reflecting surface 42 reaches an area of ​​the first transmitting surface 41 that does not directly face the screen S, the peripheral light L can be made to reach the screen. This makes it easy to ensure the amount of light around the enlarged image projected on the screen S.

[0049] In this example, the second optical axis of the first reflecting surface 42 and the third optical axis of the second transmitting surface 43 coincide with the first optical axis. In this way, the first optical element 33 can be easily manufactured.

[0050] In this example, the first reflecting surface 42 and the second transmitting surface 43 have aspherical shapes, which makes it easier to correct various aberrations.

[0051] Next, the optical system 3A of this example includes a second optical element 34 arranged on the reduction side of the first optical element 33, and a second optical system 32 (refractive optical system) arranged on the reduction side of the second optical element 34. The second optical element 34 has a third transmitting surface 51, a second reflecting surface 52 located on the reduction side of the third transmitting surface, and a fourth transmitting surface 53 located on the reduction side of the second reflecting surface 52. The second transmitting surface 43 of the first optical element 33 and the third transmitting surface 51 of the second optical element 34 face each other, and light from the reduction-side conjugate surface is incident on the second transmitting surface via the second optical system 32 and the second optical element 34.

[0052] Furthermore, in this example, the angle θ1 between the optical axis M of the first optical element 33 and the optical axis N of the second optical system 32 is 90° or less. This allows the optical elements arranged on the reduction side of the second optical element 34 to be arranged parallel to the enlargement-side image forming surface or in a direction away from the enlargement-side image forming surface. This prevents the optical elements arranged on the enlargement side of the second optical element 34 from interfering with the enlargement-side image forming surface. This makes it possible to install the optical system in a position close to the screen S.

[0053] Fig. 5 is a diagram showing the MTF on the enlargement side of the optical system 3A. The horizontal axis of Fig. 5 represents spatial frequency, and the vertical axis represents contrast reproduction ratio. As shown in Fig. 5, the optical system 3A of this example has high resolution.

[0054] Fig. 6 is a spot diagram of the optical system 3 A. As shown in Fig. 6, in this example, the spot variation is suppressed.

[0055] Example 2 Fig. 7 is a ray diagram schematically illustrating the entire optical system of Example 2. Fig. 8 is a ray diagram for optical system 3B of Example 2. Fig. 9 is a ray diagram for the first optical system of Example 2. As shown in Figs. 7 and 8, a liquid crystal panel 18 is disposed on the reduction-side conjugate surface of optical system 3.

[0056] As shown in FIG. 6, the optical system 3B of this example has, in order from the enlargement side to the reduction side, a first optical system 31 and a second optical system 32. The first optical system 31 is a reflective optical system. The optical axis M of the first optical system 31 extends along the Z-axis direction. That is, the optical axis M of the first optical system 31 is perpendicular to the screen S. The second optical system 32 is a refractive optical system. The optical axis N of the second optical system 32 extends along the Y-axis direction. The screen S is located in the Z1 direction of the optical axis N.

[0057] As shown in FIGS. 7 and 8 , the first optical system 31 includes a lens 35, a first optical element 33, and a second optical element 34. The lens 35, the first optical element 33, and the second optical element 34 are arranged in this order from the magnification side to the reduction side. The optical axis of the first optical element 33 and the optical axis of the third transmitting surface 51 of the second optical element 34 are substantially parallel to each other and extend along the Z-axis direction. In this example, the optical axis of the first optical element 33 and the optical axis of the third transmitting surface 51 of the second optical element 34 coincide with each other. Furthermore, the optical axis of the first optical element 33 and the fourth optical axis of the lens 35 coincide with each other. In other words, the optical axis M of the first optical system 31 is the optical axis of the first optical element 33, the optical axis of the third transmitting surface 51 of the second optical element 34, and the fourth optical axis of the lens 35.

[0058] The lens 35 is located in the Y1 direction of the first optical element 33. The lens 35 has positive power. The lens 35 has a first lens surface 61 facing the magnification side and a second lens surface 62 facing the reduction side. The first lens surface 61 has a convex shape. The first lens surface 61 has an aspherical shape. The second lens surface 62 has a concave shape. The second lens surface 62 has an aspherical shape. The first lens surface 61 and the second lens surface 62 both have shapes that are rotationally symmetric about the fourth optical axis of the lens 35.

[0059] The first optical element 33 consists of one optical element. The first optical element 33 is located in the Z2 direction of the second optical element 34. The first optical element 33 has a first transmitting surface 41, a first reflecting surface 42 located on the reduction side of the first transmitting surface 41, and a second transmitting surface 43 located on the reduction side of the first reflecting surface 42.

[0060] The first transmitting surface 41 has a convex shape facing the Y1 direction. A first optical axis of the first transmitting surface 41 coincides with the optical axis M of the first optical system 31. The first transmitting surface 41 has a shape that is rotationally symmetric about the first optical axis of the first transmitting surface 41. The first transmitting surface 41 has positive power. The first reflecting surface 42 is located in the Y2 direction of the first transmitting surface 41. The first reflecting surface 42 has a concave shape that is recessed in the Z2 direction. A second optical axis of the first reflecting surface 42 coincides with the optical axis M of the first optical system 31. The first reflecting surface 42 has a shape that is rotationally symmetric about the second optical axis of the first reflecting surface 42. The first reflecting surface 42 has negative power. The first reflecting surface 42 is formed by providing a reflective coating layer on the outer surface of the first optical element 33 in the Z2 direction. A third optical axis of the second transmitting surface 43 coincides with the optical axis M of the first optical system 31. The second transmitting surface 43 has a shape that is rotationally symmetric about the third optical axis of the second transmitting surface 43. The second transmitting surface 43 has negative power. The first reflecting surface 42 and the second transmitting surface 43 have aspherical shapes.

[0061] The second optical element 34 is composed of a single optical element. The second optical element 34 includes a third transmitting surface 51, a second reflecting surface 52 located on the reduction side of the third transmitting surface 51, and a fourth transmitting surface 53 located on the reduction side of the second reflecting surface 52. The third transmitting surface 51 faces the second transmitting surface 43 in the Z-axis direction. The third transmitting surface 51 has a convex shape facing the Z2 direction. The optical axis of the third transmitting surface 51 coincides with the optical axis M of the first optical system 31. The third transmitting surface 51 has a shape that is rotationally symmetrical about the optical axis of the third transmitting surface 51. The third transmitting surface 51 has negative power. The second reflecting surface 52 is a flat mirror with no power. The second reflecting surface 52 is inclined 45° with respect to the Y-axis and Z-axis. The second reflecting surface 52 bends the optical path by 90° between the third transmitting surface 51 and the fourth transmitting surface 53. The second reflecting surface 52 is formed by providing a reflective coating layer on the outer surface of the second optical element 34 in the Z1 direction. The fourth transmitting surface 53 faces the Y2 direction and faces the lens L12. The angle between the optical axis of the fourth transmitting surface 53 and the optical axis of the third transmitting surface 51 is 90°. That is, the angle between the optical axis of the fourth transmitting surface 53 and the optical axis M of the first optical element 33 is 90°. The optical axis of the fourth transmitting surface 53 coincides with the optical axis N of the second optical system 32. The fourth transmitting surface 53 has a shape that is rotationally symmetric about the optical axis of the fourth transmitting surface 53. The fourth transmitting surface 53 has positive power. The third transmitting surface 51 and the fourth transmitting surface 53 have aspherical shapes.

[0062] As shown in Fig. 8, the second optical system 32 includes 12 lenses L1 to L12. The lenses L1 to L12 are arranged in this order from the reduction side to the enlargement side. The lenses L2, L7, and L12 are aspherical lenses with aspherical shapes on both sides. Each lens in the first optical system 31 has a rotationally symmetric surface centered on the optical axis N.

[0063] As shown in FIG. 8, the liquid crystal panel 18, which is disposed on the reduction-side conjugate plane of the optical system 3A, forms a projected image on the Z2 side of the optical axis N. The angle θ1 formed between the optical axis M of the first optical element 33 and the optical axis N of the second optical system 32 is 90° or less. In this example, the angle θ1 is 90°. Therefore, after passing through the second optical system 32, light from the liquid crystal panel 18 side is bent 90° by the second reflecting surface 52 of the second optical element 34 and heads in the Z2 direction. The light headed in the Z2 direction is bent back in the Z1 and Y1 directions by the first reflecting surface 42 of the first optical element 33 and reaches the screen S.

[0064] 8, the optical system 3A forms an intermediate image 30 between the reduction-side conjugate surface and the magnification-side conjugate surface, the intermediate image 30 being conjugate to the reduction-side conjugate surface and the magnification-side conjugate surface. In this example, the intermediate image 30 is formed between the first reflecting surface 42 of the first optical element 33 and the second reflecting surface 52 of the second optical element 34.

[0065] 9, light traveling between the first transmitting surface 41 and the first reflecting surface 42 includes peripheral light L that inclines in a direction away from the screen S, which is the magnification-side conjugate plane, as it approaches the first transmitting surface 41. Between the first transmitting surface 41 and the lens 35, the peripheral light L inclines in a direction away from the screen S as it moves away from the first transmitting surface 41. Furthermore, between the lens 35 and the screen S, the peripheral light L inclines in a direction approaching the screen S as it moves away from the lens 35. Furthermore, an imaginary line Q connecting a maximum effective point P of the peripheral light L on the first transmitting surface 41 and the center of curvature of the first transmitting surface 41 intersects with the first optical axis at an angle θ2 of 90° or more.

[0066] The lens data for optical system 3B is as follows. Surface numbers are assigned in order from the magnification side to the reduction side. The symbols refer to the liquid crystal panel, dichroic prism, lens, and screen. Data for surface numbers that do not correspond to the liquid crystal panel, dichroic prism, lens, and screen are dummy data. Surfaces with an * next to the surface number are aspheric. R is the radius of curvature. D is the on-axis surface spacing. nd is the refractive index. νd is the Abbe number. Y is the aperture radius. The units of R, D, and Y are mm. The lens data in this example was designed using CODE V by Synopsys.

[0067] Sign Surface No. RD nd vd Mode Y 18 0 0.00000 22.000000 Refraction 19 1 0.00000 37.300000 1.516800 64.17 Refraction 20.3480 2 0.00000 0.762700 Refraction 22.1060 L1 3 157.73710 10.000000 1.994904 27.96 Refraction 22.2740 4 -59.76320 4.440906 Refraction 22.1250 L2 5 -47.37529 10.000000 2.050800 26.94 Refraction 19.2330 6 -103.89113 7.276867 Refraction 19.2740 L3 7 -35.49424 3.259752 1.937229 32.32 Refraction 18.4950 8 -63.50302 3.002572 Refraction 19.5370 L4 9 103.13388 8.732663 1.658725 41.40 Refraction 20.1430 10 -94.40586 0.500000 Refraction 19.9850 L5 11 89.94729 2.000000 2.050800 26.94 Refraction 19.0060 12 37.49030 0.500000 Refraction 18.0290 L6 13 36.86363 20.000000 1.446156 80.88 Refraction 18.1140 14 -69.65825 30.000000 Refraction 17.0000 O 15 0.00000 134.972004 Refraction 14.4000 L7 16 105.41092 13.783413 1.469124 82.22 Refraction 40.0000 17 1094.72746 3.834971 Refraction 39.0280 L8 18 137.23940 11.351333 1.986125 16.48 Refraction 39.2540 19 -228.96975 12.674715 Refraction 38.9460 L9 20 -90.50307 17.528035 1.869148 18.09 Refraction 34.1820 21 -301.24837 8.314561 Refraction 33.5580 L10 22 -97.26184 2.000000 1.986125 16.48 Refraction 32.8700 23 137.98515 2.000000 Refraction 34.1190 L11 24 70.50560 10.000000 1.455365 87.06 Refraction 39.7670 25 157.41492 79.583464 Refraction 39.9520 L12 *26 -27.57550 8.000000 1.509186 56.32 Refraction 48.0000 *27 -47.11522 9.521845 Refraction 51.6580 34 *28 -140.46983 72.000000 1.509186 56.32 Refraction 64.8350 29 0.00000 -15.000000 1.509186 56.32 Reflection 91.6220 *30 230.59254 -3.000000 Refraction 63.7000 33 *31 -54.82491 -64.000000 1.509186 56.32 Refraction 54.3140 *32 20.67261 0.000000 1.509186 56.32 Reflection 51.1060 33 -44.00000 0.000000 Refraction 21.6820 35 *34 -131.10106 20.000000 1.509186 56.32 Refraction 117.8940 *35 -100.00000 0.000000 Refraction 120.9940 36 0.00000 0.000000 Refraction 2186.7700 S 37 0.00000 0.000000 Refraction 2186.7700

[0068] The aspherical coefficients are as follows:

[0069] Face number 26 27 28 30 Conic constant -7.983351E-01 -7.935454E-01 -5.694192E+01 7.416526E-01 4th order coefficient 1.571127E-06 -2.932391E-06 8.694656E-07 -5.656628E-07 6th order coefficient -5.227067E-10 7.948796E-10 -1.45704E-10 7.550079E-10 8th order coefficient 4.752561E-13 -2.731021E-13 3.119986E-14 -2.009279E-13 10th order coefficient -3.805627E-17 7.607665E-17 -2.61777E-18 1.677154E-17

[0070] Face number 31 32 34 35 Conic constant -1.386817E+02 -1.637304E+00 -4.949426E-01 -4.448864E-01 4th order coefficient -4.815839E-06 -1.617638E-06 2.724492E-08 3.262084E-07 6th order coefficient 5.544913E-10 2.867275E-10 -1.631719E-12 -2.720302E-11 8th order coefficient 5.021641E-13 5.726965E-14 2.587226E-16 1.045415E-15 10th order coefficient -1.123307E-16 -2.044994E-17 -9.382203E-21 -5.756513E-21

[0071] The ray coordinates at the object plane are:

[0072] Ray number X coordinate Y coordinate 1 0 -1.38 2 0 -4.86 3 0 -8.34 4 0 -11.81 5 0 -15.29 6 0 -18.77

[0073] In this example, the surface numbers 29, 33, 34, and 36 are decentered surfaces. The parameters of the decentered surfaces are as follows:

[0074] Face number 29 Eccentricity type: Decenter and bend Parameter X 0.0000 Parameter Y 0.0000 Parameter Z 0.0000 Parameter α 45.0000

[0075] Face number 33 Eccentricity Type Global Coordinates Global Reference Plane 32 Parameter X 0.0000 Parameter Y -44.0000 Parameter Z 24.0000 Parameter α -90.0000

[0076] Face number 34 Eccentricity Type Global Coordinates Global Reference Plane 32 Parameter X 0.0000 Parameter Y 0.0000 Parameter Z 55.0000 Parameter α 0.0000

[0077] Face number 36 Eccentricity Type Global Coordinates Global Reference Plane 32 Parameter X 0.0000 Parameter Y 0.0000 Parameter Z 201.0000 Parameter α 0.0000

[0078] (Action and effect) The optical system 3B of this example includes a first optical element 33 and a lens 35 arranged on the enlargement side of the first optical element 33. The first optical element 33 includes a first transmitting surface 41, a first reflecting surface 42 located on the reduction side of the first transmitting surface 41, and a second transmitting surface 43 located on the reduction side of the first reflecting surface 42. The first transmitting surface 41 has power. In addition, in the optical system 3B of this example, light passing between the first transmitting surface 41 and the first reflecting surface 42 includes ambient light L that inclines in a direction away from the screen S as it approaches the first transmitting surface 41. Between the first transmitting surface 41 and the lens 35, the ambient light L inclines in a direction away from the screen S as it moves away from the first transmitting surface 41. In addition, between the lens 35 and the screen S, the ambient light L inclines in a direction approaching the screen S as it moves away from the lens 35.

[0079] According to this example, within the first optical element 33, light traveling from the first reflecting surface 42 to the first transmitting surface 41 includes peripheral light L that inclines in a direction away from the screen S as it approaches the first transmitting surface 41. Furthermore, between the first transmitting surface 41 and the lens 35, the peripheral light L inclines in a direction away from the screen S as it moves away from the first transmitting surface 41. Therefore, when light incident on the first optical element 33 from the reduction-side second transmitting surface 43 is turned back by the first reflecting surface 42 and travels toward the first transmitting surface 41, the peripheral light L also travels in a direction away from the screen S. Furthermore, when the peripheral light L travels from the first transmitting surface 41 to the lens 35, it also travels in a direction away from the screen S. Here, if the peripheral light L does not reach the screen S, a problem occurs in which the periphery of the enlarged image projected on the screen S becomes dark. In contrast, in this example, between the lens 35 and the screen S, the peripheral light L inclines in a direction toward the screen S as it moves away from the lens 35. That is, the peripheral light L that passes through the first optical element 33 and travels away from the screen S travels toward the screen S via the lens 35. Therefore, the amount of light around the periphery of the enlarged image projected onto the screen S can be ensured.

[0080] Furthermore, since the projected light is controlled by the lens 35 arranged on the magnification side of the first optical element 33, the projected light can be controlled at a position closer to the screen S compared to the first embodiment. This makes it possible to improve the optical performance of the ambient light L.

[0081] In this example, the first transmitting surface 41 has a convex shape that is rotationally symmetric about the first optical axis. When a virtual line Q is defined that connects the maximum effective point P of the peripheral light L on the first transmitting surface 41 with the center of curvature of the first transmitting surface 41, the virtual line Q intersects with the first optical axis at an angle θ of 90° or more. Therefore, in the optical system 3B of this example, even if the peripheral light L of the light reflected by the first reflecting surface 42 reaches an area of ​​the first transmitting surface 41 that does not directly face the screen S, the peripheral light L can be made to reach the screen. This makes it easy to ensure the amount of light around the enlarged image projected on the screen S.

[0082] In this example, the second optical axis of the first reflecting surface and the third optical axis of the second transmitting surface coincide with the first optical axis, which makes it easier to manufacture the first optical element.

[0083] In this example, the fourth optical axis of the lens 35 coincides with the first optical axis, which allows the first optical element 33 and the lens 35 to be positioned with higher precision than when these optical axes do not coincide.

[0084] In this example, the lens 35 has an aspherical shape, so it is easier to correct aberrations.

[0085] In this example, the first reflecting surface 42 and the second transmitting surface 43 have aspherical shapes, which makes it easier to correct various aberrations.

[0086] Next, the optical system 3B of this example includes a second optical element 34 arranged on the reduction side of the first optical element 33, and a second optical system 32 (refractive optical system) arranged on the reduction side of the second optical element 34. The second optical element 34 has a third transmitting surface 51, a second reflecting surface 52 located on the reduction side of the third transmitting surface, and a fourth transmitting surface 53 located on the reduction side of the second reflecting surface 52. The second transmitting surface 43 of the first optical element 33 and the third transmitting surface 51 of the second optical element 34 face each other, and light from the reduction-side conjugate surface is incident on the second transmitting surface via the second optical system 32 and the second optical element 34.

[0087] Furthermore, in this example, the angle θ1 between the optical axis M of the first optical element 33 and the optical axis N of the second optical system 32 is 90° or less. This allows the optical elements arranged on the reduction side of the second optical element 34 to be arranged parallel to the enlargement-side image forming surface or in a direction away from the enlargement-side image forming surface. This prevents the optical elements arranged on the enlargement side of the second optical element 34 from interfering with the enlargement-side image forming surface. This makes it possible to install the optical system in a position close to the screen S.

[0088] Fig. 10 is a diagram showing the MTF on the enlargement side of the optical system 3B. The horizontal axis of Fig. 10 represents spatial frequency, and the vertical axis represents contrast reproduction ratio. As shown in Fig. 10, the optical system 3B of this example has high resolution.

[0089] Fig. 11 is a spot diagram of the optical system 3B. As shown in Fig. 11, in this example, the spot variation is suppressed.

[0090] (Other embodiments) The optical system 3 of this example can be used as an imaging lens. In this case, an imaging element is disposed on the reduction-side conjugate plane of the optical system 3. [Explanation of symbols]

[0091] 1...projector, 2...image forming unit, 3, 3A, 3B...optical system, 4...control unit, 6...image processing unit, 7...display driving unit, 10...light source, 11...integrator lens, 12...integrator lens, 13...polarization conversion element, 14...superimposing lens, 15...dichroic mirror, 16...reflection mirror, 17R...field lens, 17G...field lens, 17B...field lens, 18 (18B, 18R, 18G)...liquid crystal panel, 19...cross dichroic prism, 21...dichroic LEIC mirror, 22... relay lens, 23... reflecting mirror, 24... relay lens, 25... reflecting mirror, 30... intermediate image, 31... first optical system, 32... second optical system, 33... first optical element, 34... second optical element, 35... lens, 41... first transmitting surface, 42... first reflecting surface, 43... second transmitting surface, 51... third transmitting surface, 52... second reflecting surface, 53... fourth transmitting surface, 61... first lens surface, 62... second lens surface, L1 to L12... lens, N... optical axis, M... optical axis, P... maximum effective point, Q... virtual line, S... screen.

Claims

1. An optical system comprising a first optical element and a lens disposed on a magnification side of the first optical element, the first optical element has a first transmitting surface, a first reflecting surface having an aspherical shape and located on the reduction side of the first transmitting surface, and a second transmitting surface having an aspherical shape and located on the reduction side of the first reflecting surface, the first transmitting surface has a power; the light passing between the first transmitting surface and the first reflecting surface includes a peripheral ray that is inclined in a direction away from the magnification-side conjugate surface as it approaches the first transmitting surface, the peripheral light is inclined, between the first transmitting surface and the lens, in a direction moving away from the magnification-side conjugate surface as the peripheral light moves away from the first transmitting surface, and, between the lens and the magnification-side conjugate surface, in a direction moving closer to the magnification-side conjugate surface as the peripheral light moves away from the lens.

2. the first transmitting surface has a convex shape that is rotationally symmetric about the first optical axis; 2. The optical system according to claim 1, wherein when a virtual line connecting a maximum effective point of the peripheral light on the first transmitting surface and a center of curvature of the first transmitting surface is defined, an angle formed between the virtual line and the first optical axis on the second transmitting surface side is 90° or more when viewed from the enlarged side of the first optical element.

3. 3. The optical system according to claim 2, wherein a second optical axis of said first reflecting surface and a third optical axis of said second transmitting surface coincide with said first optical axis.

4. 4. The optical system according to claim 2, wherein a fourth optical axis of the lens coincides with the first optical axis.

5. 5. The optical system according to claim 3, wherein the first optical axis is perpendicular to the magnification-side conjugate surface.

6. a second optical element disposed on the reduction side of the first optical element; a refractive optical system disposed on the reduction side of the second optical element, the second optical element has a third transmitting surface, a second reflecting surface located on the reduction side of the third transmitting surface, and a fourth transmitting surface located on the reduction side of the second reflecting surface, the second transmitting surface and the third transmitting surface are opposed to each other, 6. The optical system according to claim 2, wherein light from the reduction-side conjugate surface is incident on the second transmitting surface via the refractive optical system and the second optical element.

7. 7. The optical system according to claim 6, wherein an angle between the first optical axis and an optical axis of the refractive optical system is 90 degrees or less when viewed from the refractive optical system and the first reflecting surface side.

8. a light modulation element disposed on the reduction-side conjugate plane and modulating light emitted from a light source; an optical system according to claim 6 or 7, which projects light modulated by the light modulation element; A projector comprising:

Images