Projection optics and projectors
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- SEIKO EPSON CORP
- Filing Date
- 2022-11-25
- Publication Date
- 2026-08-04
Smart Images
Figure 0007899699000001 
Figure 0007899699000002 
Figure 0007899699000003
Abstract
Description
Technical Field
[0001] The present invention relates to a projection optical system and a projector.
Background Art
[0002] A projector that enlarges a projection image displayed on an image display element and projects it onto a screen using a projection optical system is described in Patent Document 1. The projection optical system includes a refractive optical system and a reflective optical system in order from the reduction side to the enlargement side. The refractive optical system includes a plurality of refractive lenses. The reflective optical system includes a first reflective optical system, a second reflective optical system, and a third reflective optical system provided in order from the refractive optical system side on the optical path of the light beam emitted from the refractive optical system. The first reflective optical system includes a first reflective surface having a concave shape. The second reflective optical system includes a second reflective surface having a curved surface shape. The third reflective optical system includes a third reflective surface having a convex shape. The absolute value of the focal length of the third reflective optical system is larger than the absolute value of the focal length of the first reflective optical system. The projection distance of the projection optical system in the same document is about 372 mm at the shortest.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] There is a need for a projection optical system with a shorter projection distance.
[0005] To solve the above problems, the projection optical system of the present invention comprises a first optical system consisting of a plurality of lenses and a second optical system, arranged in order from the reduction side to the enlargement side, wherein the first optical system has positive power, and the second optical system has a first reflective optical system, a second reflective optical system, and a third reflective optical system, arranged in order from the first optical system on the optical path of the light rays emitted from the first optical system, wherein the first reflective optical system has a first reflective surface having a concave aspherical shape, the second reflective optical system has a second reflective surface having a concave or planar shape, and the third reflective optical system has a third reflective surface having a convex aspherical shape, and when the focal length of the first reflective optical system is f1, the focal length of the second reflective optical system is f2, and the focal length of the third reflective optical system is f3, the following condition (1) is satisfied. |f2|>|f1|>|f3|···(1)
[0006] Next, the projector of the present invention comprises the above-mentioned projection optical system and the image forming element that forms the projected image on the reduction-side conjugate surface of the projection optical system. Department It is characterized by having the following: [Brief explanation of the drawing]
[0007] [Figure 1] This figure shows a schematic configuration of a projector equipped with the projection optical system of the present invention. [Figure 2] This is a ray diagram of a projection optical system. [Figure 3] This is a ray diagram of the projection optical system of Example 1. [Figure 4] This figure shows the MTF on the magnified side of the projection optical system in Example 1. [Figure 5] This is a ray diagram of the projection optical system of Example 2. [Figure 6] This figure shows the MTF on the magnified side of the projection optical system in Example 2. [Figure 7] This is a ray diagram of the projection optical system of Example 3. [Figure 8] This figure shows the MTF on the magnified side of the projection optical system in Example 3. [Modes for carrying out the invention]
[0008] An optical system and a projector according to an embodiment of the present invention will be described below with reference to the drawings.
[0009] (projector) Figure 1 is a schematic diagram of a projector equipped with the projection optical system 3 of the present invention. As shown in Figure 1, the projector 1 comprises an image forming unit 2 that generates a projection image to be projected onto a screen S, a projection 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.
[0010] (Image forming unit and control unit) The image forming unit 2 comprises a light source 10, a first integrator lens 11, a second integrator lens 12, a polarization conversion element 13, and a superimposed lens 14. The light source 10 is composed of, for example, an ultra-high pressure mercury lamp, a solid-state light source, etc. 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 divides the light beam from the light source 10 into multiple 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.
[0011] The polarization conversion element 13 converts the light from the second integrator lens 12 into a predetermined linearly polarized light. The superimposing lens 14 superimposes the images of each lens element of the first integrator lens 11 onto the display areas of the liquid crystal panels 18R, 18G, and 18B, which will be described later, via the second integrator lens 12.
[0012] The image forming unit 2 also includes a first dichroic mirror 15, a reflective mirror 16, a field lens 17R, and a liquid crystal panel 18R. The first dichroic mirror 15 reflects red light, which is part of the light rays incident from the superimposed lens 14, and transmits green light and blue light, which are also parts of the light rays incident from the superimposed lens 14. The red light reflected by the first dichroic mirror 15 passes through the reflective mirror 16 and the field lens 17R and enters the liquid crystal panel 18R. The liquid crystal panel 18R is an image forming element. The liquid crystal panel 18R modulates the red light according to the image signal to form a red projected image.
[0013] Furthermore, the image forming unit 2 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 rays from the first dichroic mirror 15, and transmits B light, which is a portion of the light rays 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 an image forming element. The liquid crystal panel 18G modulates the G light according to the image signal to form a green projected image.
[0014] The image forming unit 2 also includes a relay lens 22, a reflective mirror 23, a relay lens 24, a reflective 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 reflective mirror 23, the relay lens 24, the reflective mirror 25, and the field lens 17B before entering the liquid crystal panel 18B. The liquid crystal panel 18B is an image forming element. The liquid crystal panel 18B modulates the B light according to the image signal to form a blue projected image.
[0015] The liquid crystal panels 18R, 18G, and 18B surround the cross-dichroic prism 19 from three directions. The cross-dichroic prism 19 is a prism for photosynthesis and generates a projected image by synthesizing the lights modulated by each of the liquid crystal panels 18R, 18G, and 18B.
[0016] The projection optical system 3 enlarges and projects the projected image synthesized by the cross-dichroic prism 19 onto the screen S.
[0017] The control unit 4 includes an image processing unit 6 to which an external image signal such as a video signal is input, and a display driving unit 7 that drives the liquid crystal panel 18R, the liquid crystal panel 18G, and the liquid crystal panel 18B based on the image signal output from the image processing unit 6. <Here, for convenience, the three mutually orthogonal axes will be referred to as the X-axis, Y-axis, and Z-axis in the following explanation. The direction along the first optical axis N of the projection optical system 3 will be defined as the Z-axis direction. In the Z-axis direction, the side opposite to the side where the liquid crystal panel 18 is located will be defined as the first direction Z1, and the side where the liquid crystal panel 18 is located will be defined as the second direction Z2. The Y-axis extends along the screen S. The Y-axis direction is vertical, with one side of the Y-axis direction being defined as upward Y1 and the other side as downward Y2. The X-axis extends in the width direction of the screen.
[0021] Below, we will describe three examples of the configuration of the projection optical system 3 installed in the projector 1. [Example 1] Figure 3 is a ray diagram of the projection optical system 3A of Embodiment 1. As shown in Figure 3, the projection optical system 3A consists of a first optical system 31 and a second optical system 32, arranged in order from the reduction side to the enlargement side. The first optical axis N of the first optical system 31 and the second optical axis M of the second optical system 32 coincide.
[0022] The first optical system 31 is a refractive optical system with positive power. The first optical system 31 consists of multiple lenses. Specifically, the first optical system 31 consists of 10 lenses L1 to L10. Lenses L1 to L10 are arranged in this order from the reduction side to the magnification side. An aperture 51 is positioned between lens L4 and lens L5.
[0023] Lens L1 has positive power. Lens L1 is a meniscus lens. Lens L1 has a concave shape on the reducing side and a convex shape on the expanding side. Lens L2 has positive power. Lens L2 is a meniscus lens. Lens L2 has a convex shape on the reducing side and a concave shape on the expanding side.
[0024] Lens L3 has negative power. Lens L3 has a convex shape on the reducing side and a concave shape on the expanding side. Lens L4 has negative power. Lens L4 has convex shapes on both the reducing and expanding sides. Lenses L3 and L4 are joined together to form a cemented lens L21.
[0025] Lens L5 has positive power. Lens L5 has convex shapes on its retraction and magnification surfaces. Lens L6 has negative power. Lens L6 has concave shapes on its retraction and magnification surfaces. Lens L7 has positive power. Lens L7 has convex shapes on its retraction and magnification surfaces. Lens L8 has negative power. Lens L8 is a meniscus lens. Lens L8 has a concave shape on its retraction surface and a convex shape on its magnification surface.
[0026] Lens L9 (second lens) has positive power. Lens L9 is a meniscus lens. Lens L9 has a convex shape on the reducing side and a concave shape on the expanding side. Lens L9 comprises a first portion 41 on one side with respect to the first optical axis N and a second portion 42 on the other side. The first portion 41 is a light-transmitting portion that functions as part of the first optical system 31. More specifically, the first portion 41 is a light-transmitting portion that functions as a refractive lens of the first optical system 31. The second portion 42 is a reflective portion that functions as the second reflective surface 340, which will be described later.
[0027] Lens L10 (first lens) has positive power. Lens L10 is a meniscus lens. Lens L10 has a concave shape on the reducing side and a convex shape on the expanding side. All of the lenses L1 to L10 that constitute the first optical system 31 have a shape that is rotationally symmetric with respect to the first optical axis N of the first optical system 31 as the axis of rotation.
[0028] The second optical system 32 has a first reflective optical system 33, a second reflective optical system 34, and a third reflective optical system 35 in order from the first optical system 31, along the optical path of the light rays emitted from the first optical system 31. Here, the lens L10 is positioned in the first direction Z1 between the first reflective optical system 33 and the second reflective optical system 34, and between the second reflective optical system 34 and the third reflective optical system 35.
[0029] The first reflective optical system 33 is positioned on the magnified side of the first optical system 31. The first reflective optical system 33 is located downward Y2 with respect to the second optical axis M. The first reflective optical system 33 has a first reflective surface 330 which has a concave shape. The first reflective surface 330 has an aspherical shape.
[0030] The second reflective optical system 34 is positioned on the optical path, on the magnifying side of the first reflective optical system 33. The second reflective optical system 34 is located above Y1 with respect to the second optical axis M. The second reflective optical system 34 has a second reflective surface 340 with a concave shape. The second reflective surface 340 is provided on the magnifying side lens surface 420 of the second portion 42 of the lens L9. The second reflective surface 340 is formed by a reflective coating layer provided on the magnifying side lens surface 420 of the second portion 42.
[0031] The third reflective optical system 35 is positioned on the optical path, on the enlarged side of the second reflective optical system 34. The third reflective optical system 35 is located above Y1 with respect to the second optical axis M. The third reflective optical system 35 has a third reflective surface 350 which has a convex shape. The third reflective surface 350 has an aspherical shape.
[0032] The first reflective surface 330, the second reflective surface 340, and the third reflective surface 350 constituting the second optical system 32 have a shape that is rotationally symmetric with respect to the second optical axis M of the second optical system 32 as the axis of rotation.
[0033] Here, the liquid crystal panel 18 forms a projected image within an image-forming surface perpendicular to the first optical axis N of the first optical system 31. The liquid crystal panel 18 is positioned offset upward Y1 with respect to the first optical axis N of the first optical system 31. Light rays from the liquid crystal panel 18 pass through the first optical system 31 and then the second optical system 32 in that order. Between the first optical system 31 and the second optical system 32, the light rays pass downward Y2 of the first optical axis N and head towards the first reflective surface 330 of the second optical system 32.
[0034] Light rays that reach the first reflective surface 330 are reflected across the first optical axis N upward Y1 and toward the second direction Z2 and upward Y1. Light rays reflected by the first reflective surface 330 pass through the lens L10 and reach the second reflective surface 340. Light rays that reach the second reflective surface 340 are reflected toward the first direction Z1 and upward Y1. Light rays reflected by the second reflective surface 340 pass through the lens L10 and reach the third reflective surface 350. Light rays that reach the third reflective surface 350 are reflected toward the second direction Z2 and upward Y1. Light rays reflected by the third reflective surface 350 are amplified by the third reflective surface 350 and reach the screen S.
[0035] Assuming that the F-number of the projection optical system 3A is FNo and the maximum half-angle of view of the entire lens system is ω, the data for the projection optical system 3A of Example 1 is as follows.
[0036] Fno 1.431 ω 80.143°
[0037] The lens data for projection optical system 3A is as follows. The surface numbers are assigned sequentially from the reduction side to the enlargement side. The symbols are those for the liquid crystal panel, dichroic prism, lens, first reflecting surface, second reflecting surface, third reflecting surface, and screen. R is the radius of curvature. D is the axial spacing. nd is the refractive index. νd is the Abbe number. Y is the effective radius. The units for R, D, and Y are mm.
[0038] Code plane number RD nd vd Mode Y 18 0 0.00000 3.000000 Refraction 19 1 0.00000 25.750000 1.516330 64.14 Refraction 11.623 2 0.00000 3.306682 Refraction 17.017 L01 3 -528.38781 6.000000 1.986125 16.48 Refraction 18.000 4 -53.59618 0.100000 Refraction 18.528 L02 5 36.16025 6.593978 1.913041 28.20 Refraction 18.724 6 102.64785 11.898469 Refraction 17.948 L03 7 360.09349 2.303687 1.986125 16.48 Refraction 14.285 L04 8 23.69596 10.970660 1.486555 77.12 Refraction 13.162 9 -43.41655 31.906933 Refraction 13.000 51,L05 10 39.61222 7.000000 1.611109 57.56 Refraction 13.000 11 -110.42307 14.196605 Refraction 13.255 L06 12 -107.62425 3.384629 1.917513 26.94 Refraction 13.659 13 52.74696 4.002725 Refraction 14.130 L07 14 59.79382 6.739074 1.797855 19.51 Refraction 16.172 15 -64.89773 4.086216 Refraction 16.409 L08 16 -29.85440 6.547540 1.938332 22.41 Refraction 16.368 17 -50.82914 72.919770 Refraction 18.646 L09 18 275.26448 8.000000 1.849076 37.72 Refraction 33.805 19 1396.48188 38.982077 Refraction 34.085 L10 20 -448.48764 19.000000 1.637611 55.29 Refraction 42.321 21 -187.55816 25.392163 Refraction 45.024 330 22* -64.43464 -25.392163 Reflection 47.385 L10 23 -187.55816 -19.000000 1.637611 55.29 Refraction 36.208 24 -448.48764 -38.982077 Refraction 28.586 340 25 1396.48188 38.982077 Reflection 26.127 L10 26 -448.48764 19.000000 1.637611 55.29 Refraction 57.938 27 -187.55816 49.210956 Refraction 64.005 350 28* 53.46671 -155.000000 Reflection 142.233 S 29 0.00000 0.000000 Refraction 1330.358
[0039] The aspherical coefficients are as follows:
[0040] Page numbers 22 28 Conic constant: 1.051849E-01 -4.789571E+00 The coefficient of the fourth order is 2.049492E-06 -2.943985E-08 Coefficient of the 6th order: -4.12751E-10 1.922612E-12 The coefficient of the 8th order is 2.052322E-13 -8.387132E-17 The coefficient of the 10th order is -5.492764E-17, which equates to 2.160308E-21. The coefficient of the 12th degree is 8.652296E-21 -2.42962E-26
[0041] When the focal length of the first reflective surface 330 of the first reflective optical system 33 is f1, the focal length of the second reflective surface 340 of the second reflective optical system 34 is f2, and the focal length of the third reflective surface 350 of the third reflective optical system 35 is f3, the data for the projection optical system 3A of Example 1 is as follows.
[0042] f1 32.217mm f2 698.241mm f3 -26.733mm
[0043] The projection distance of the projection optical system 3A in Example 1 is as follows:
[0044] Projection distance: 155,000 mm
[0045] In this example, the projection optical system 3A satisfies the following condition (1) when the focal length of the first reflective optical system is f1, the focal length of the second reflective optical system is f2, and the focal length of the third reflective optical system is f3. |f2|>|f1|>|f3|···(1)
[0046] In this example, |f1| 32.217mm |f2| 698.241mm |f3| 26.733mm Therefore, the projection optical system 3A in this example satisfies condition (1).
[0047] (Effects and Benefits) The projection optical system 3A in this example satisfies condition (1), thus allowing for a shorter projection distance. Specifically, by making the absolute value of the focal length f3 of the third reflective surface 350 smaller than the absolute value of the focal length f1 of the first reflective surface 330 and the absolute value of the focal length f2 of the second reflective surface 340, the field of view of the light rays reflected by the third reflective surface 350 can be greatly widened. This allows for a shorter projection distance for the projection optical system 3A.
[0048] Furthermore, by making the absolute value of the focal length f2 of the second reflective surface 340 greater than the absolute value of the focal length f1 of the first reflective surface 330, it becomes easier to widen the angle of light rays reflected by the second reflective surface 340. This makes it easier for the third reflective surface 350 to widen the reflection angle of light rays reflected by the third reflective surface 350 and directed toward the screen S. If the absolute value of the focal length f2 of the second reflective surface 340 is made smaller than the absolute value of the focal length f1 of the first reflective surface 330, the angle of light rays reflected by the second reflective surface 340 will decrease, making it difficult for the third reflective surface 350 to widen the field of view of light rays reflected by the third reflective surface 350 and directed toward the screen S. Consequently, if the absolute value of the focal length f2 of the second reflective surface 340 is made smaller than the absolute value of the focal length f1 of the first reflective surface 330, the projection optical system 3A will produce a smaller magnified image projected onto the screen S at the same projection distance, which is undesirable compared to the case where the absolute value of the focal length f2 of the second reflective surface 340 is made larger than the absolute value of the focal length f1 of the first reflective surface 330.
[0049] Furthermore, by making the absolute value of the focal length f2 of the second reflecting surface 340 greater than the absolute value of the focal length f1 of the first reflecting surface 330 and the absolute value of the focal length f3 of the third reflecting surface 350, that is, by weakening the power, the positive power of the first reflecting surface 330 and the negative power of the third reflecting surface 350 can be set in a balanced manner. This allows for balanced correction of various aberrations.
[0050] Here, as a comparative example, we will examine Example 6 of the prior art document, Japanese Patent Application Publication No. 2017-40849. The focal length f1 of the first reflective optical system, the focal length f2 of the second reflective optical system, the focal length f3 of the third reflective optical system, the absolute value of the focal length f1 of the first reflective optical system, the absolute value of the focal length f2 of the second reflective optical system, the absolute value of the focal length f3 of the third reflective optical system, the projection distance, and the maximum half-angle of view ω of the entire lens system are as follows.
[0051] f1 29.281mm f2 102.500mm f3 - 41.225mm |f1| 29.281mm |f2| 102.500mm |f3| 41.225mm Projection distance: 371.837 mm ω 70.2°
[0052] Therefore, since the comparative projection optical system does not satisfy condition (1), the projection distance of the comparative projection optical system is greater than that of the projection optical system 3A in the present example. In addition, the maximum half-angle of view of the comparative projection optical system is smaller than that of the projection optical system 3A in the present example.
[0053] In this example, the maximum effective radius of the third reflective surface 350 is less than 150 mm. If the maximum effective radius of the third reflective surface 350 is 150 mm or more, distortion and deflection are more likely to occur in the third reflective surface 350 during manufacturing, making it difficult to achieve high processing accuracy for the third reflective surface 350. Therefore, in this example, since the maximum effective radius of the third reflective surface 350 is less than 150 mm, high processing accuracy for the third reflective surface 350 can be achieved. This makes the magnified image projected onto the screen S by the projection optical system 3A clearer.
[0054] In this example, the multiple lenses include a positive-power lens L10 positioned on the magnification side. Lens L10 is positioned between the first reflective surface 330 and the second reflective surface 340 in a first direction Z1 along the first optical axis N of the first optical system 31. Light rays reflected by the first reflective surface 330 pass through lens L10 and reach the second reflective surface 340. As a result, the spread and angle of the light rays reflected by the first reflective surface 330 can be controlled by lens L10, thereby reducing the on-axis distance between the first reflective surface 330 and the second reflective surface 340. Furthermore, lens L10 can effectively correct various aberrations of the light rays reflected by the first reflective surface 330.
[0055] In this example, lens L10 is positioned between the second reflective surface 340 and the third reflective surface 350 in the first direction Z1. Light rays reflected by the second reflective surface 340 pass through lens L10 and reach the third reflective surface 350. As a result, the spread and angle of the light rays reflected by the second reflective surface 340 can be controlled by lens L10, thereby reducing the on-axis distance between the second reflective surface 340 and the third reflective surface 350. Furthermore, lens L10 can effectively correct various aberrations of the light rays reflected by the second reflective surface 340.
[0056] The multiple lenses include a lens L9 positioned on the reduction side relative to lens L10. Lens L9 has a first portion 41 on one side with respect to the first optical axis N and a second portion 42 on the other side. The first portion 41 is a light-transmitting portion that functions as a refractive lens of the first optical system. The second portion 42 is a reflective portion that functions as a second reflective surface 340. Therefore, since lens L9 serves both as a refractive lens and as a second reflective surface 340, the number of optical components can be reduced and the configuration of the projection optical system 3A can be simplified.
[0057] In this example, the first reflective surface 330 has a concave, aspherical shape. The third reflective surface 350 has a convex, aspherical shape. Here, since the first reflective surface 330 and the third reflective surface 350 have more power than the second reflective surface 340, the light rays reflected by the first reflective surface 330 and the third reflective surface 350 are more prone to various aberrations compared to the light rays reflected by the second reflective surface 340. Therefore, since the first reflective surface 330 and the third reflective surface 350 have aspherical shapes, the various aberrations generated in the projection optical system 3A can be corrected well.
[0058] In this example, the multiple lenses L1 to L10 have a rotationally symmetric shape with respect to the first optical axis N. Therefore, the manufacturing of each lens in the first optical system 31 is facilitated. Furthermore, it becomes easier to precisely position each lens in the first optical system 31.
[0059] In this example, the first reflective surface 330, the second reflective surface 340, and the third reflective surface 350 have a shape that is rotationally symmetric with respect to the second optical axis M. Therefore, the manufacturing of each reflective surface of the second optical system 32 becomes easier. Furthermore, it becomes easier to precisely position each reflective surface of the second optical system 32.
[0060] In this example, the first optical axis N and the second optical axis M coincide. Therefore, it becomes easy to precisely position the first optical system 31 and the second optical system 32.
[0061] Figure 4 shows the MTF of the projection optical system 3A on the magnified side. In Figure 4, the horizontal axis represents spatial frequency, and the vertical axis represents the contrast reproduction ratio. As shown in Figure 4, the projection optical system 3A in this example has high resolution.
[0062] [Example 2] Figure 5 is a ray diagram of the projection optical system 3B of Example 2. As shown in Figure 5, the projection optical system 3B consists of a first optical system 31 and a second optical system 32, in order from the reduction side to the enlargement side. The first optical axis N of the first optical system 31 and the second optical axis M of the second optical system 32 coincide.
[0063] The first optical system 31 is a refractive optical system with positive power. The first optical system 31 consists of multiple lenses. Specifically, the first optical system 31 consists of 10 lenses L1 to L10. Lenses L1 to L10 are arranged in this order from the reduction side to the magnification side. An aperture 51 is positioned between lens L4 and lens L5.
[0064] Lens L1 has positive power. Lens L1 is a meniscus lens. Lens L1 has a concave shape on the reducing side and a convex shape on the expanding side. Lens L2 has positive power. Lens L2 is a meniscus lens. Lens L2 has a convex shape on the reducing side and a concave shape on the expanding side.
[0065] Lens L3 has negative power. Lens L3 has a convex shape on the reducing side and a concave shape on the expanding side. Lens L4 has negative power. Lens L4 has convex shapes on both the reducing and expanding sides. Lenses L3 and L4 are joined together to form a cemented lens L21.
[0066] Lens L5 has positive power. Lens L5 has a convex shape on its reducing and magnifying surfaces. Lens L6 has negative power. Lens L6 has a concave shape on its reducing and magnifying surfaces. Lens L7 has positive power. Lens L7 has a convex shape on its reducing and magnifying surfaces.
[0067] Lens L8 has negative power. Lens L8 is a meniscus lens. Lens L8 has a concave shape on the reducing side and a convex shape on the expanding side. Lens L9 (second lens) has positive power. Lens L9 is a meniscus lens. Lens L9 has a concave shape on the reducing side and a convex shape on the expanding side.
[0068] Lens L10 (first lens) has positive power. Lens L10 is a meniscus lens. Lens L10 has a concave shape on the reducing side and a convex shape on the expanding side. All of the lenses L1 to L10 that constitute the first optical system 31 have a shape that is rotationally symmetric with respect to the first optical axis N of the first optical system 31 as the axis of rotation.
[0069] The second optical system 32 has a first reflective optical system 33, a second reflective optical system 34, and a third reflective optical system 35 in order from the first optical system 31, along the optical path of the light rays emitted from the first optical system 31. Here, the lens L10 is positioned in the first direction Z1 between the first reflective optical system 33 and the second reflective optical system 34, and between the second reflective optical system 34 and the third reflective optical system 35.
[0070] The first reflective optical system 33 is positioned on the magnified side of the first optical system 31. The first reflective optical system 33 is located downward Y2 with respect to the second optical axis M. The first reflective optical system 33 has a first reflective surface 330 which has a concave shape. The first reflective surface 330 has an aspherical shape.
[0071] The second reflective optical system 34 is positioned on the optical path, on the magnified side of the first reflective optical system 33. The second reflective optical system 34 is located above Y1 with respect to the second optical axis M. The second reflective optical system 34 has a second reflective surface 340 with a planar shape. The second reflective surface 340 is positioned between lens L9 and lens L10 in the first direction Z1.
[0072] The third reflective optical system 35 is positioned on the optical path, on the enlarged side of the second reflective optical system 34. The third reflective optical system 35 is located above Y1 with respect to the second optical axis M. The third reflective optical system 35 has a third reflective surface 350 which has a convex shape. The third reflective surface 350 has an aspherical shape.
[0073] The first reflective surface 330, the second reflective surface 340, and the third reflective surface 350 constituting the second optical system 32 have a shape that is rotationally symmetric with respect to the second optical axis M of the second optical system 32 as the axis of rotation.
[0074] Light rays from the liquid crystal panel 18 pass through the first optical system 31 and the second optical system 32 in that order. Between the first optical system 31 and the second optical system 32, the light rays pass below Y2 of the first optical axis N and head towards the first reflective surface 330 of the second optical system 32.
[0075] Light rays that reach the first reflective surface 330 are reflected across the first optical axis N upward Y1 and toward the second direction Z2 and upward Y1. Light rays reflected by the first reflective surface 330 pass through the lens L10 and reach the second reflective surface 340. Light rays that reach the second reflective surface 340 are reflected toward the first direction Z1 and upward Y1. Light rays reflected by the second reflective surface 340 pass through the lens L10 and reach the third reflective surface 350. Light rays that reach the third reflective surface 350 are reflected toward the second direction Z2 and upward Y1. Light rays reflected by the third reflective surface 350 are amplified by the third reflective surface 350 and reach the screen S.
[0076] Assuming that the F-number of the projection optical system 3B is FNo and the maximum half-angle of view of the entire lens system is ω, the data for the projection optical system 3B of Example 2 is as follows.
[0077] Fno 1.429 ω 80.182°
[0078] The lens data for projection optical system 3B is as follows. The surface numbers are assigned sequentially from the reduction side to the enlargement side. The symbols are those for the liquid crystal panel, dichroic prism, lens, first reflecting surface, second reflecting surface, third reflecting surface, and screen. R is the radius of curvature. D is the axial spacing. nd is the refractive index. νd is the Abbe number. Y is the effective radius. The units for R, D, and Y are mm.
[0079] Code plane number RD nd vd Mode Y 18 0 0.00000 3.000000 Refraction 19 1 0.00000 25.750000 1.516330 64.14 Refraction 11.623 2 0.00000 3.648092 Refraction 17.017 L01 3 -250.28858 6.000000 1.986125 16.48 Refraction 18.000 4 -49.21333 0.100000 Refraction 18.588 L02 5 33.51972 8.000000 1.927010 24.64 Refraction 18.513 6 86.85688 9.357735 Refraction 17.288 L03 7 434.14453 2.126957 1.986125 16.48 Refraction 14.319 L04 8 22.97156 11.390743 1.459223 85.62 Refraction 13.131 9 -38.15519 27.987780 Refraction 13.000 51,L05 10 39.00070 7.000000 1.673378 52.73 Refraction 13.000 11 -113.64727 15.328936 Refraction 13.202 L06 12 -54.49192 4.372790 1.930507 23.90 Refraction 13.281 13 58.30287 4.000000 Refraction 14.243 L07 14 79.10658 7.000000 1.843691 18.54 Refraction 16.577 15 -52.92728 4.530482 Refraction 16.976 L08 16 -27.26682 7.589622 1.986125 16.48 Refraction 17.000 17 -39.01552 64.695899 Refraction 20.038 L09 18 -118.25109 8.000000 1.903700 31.30 Refraction 32.090 19 -94.77445 37.635425 Refraction 33.538 L10 20 -442.36880 19.000000 1.804198 46.50 Refraction 42.522 21 -188.49008 30.169182 Refraction 45.241 330 22* -65.57949 -30.169182 Reflection 47.982 L10 23 -188.49008 -19.000000 1.804198 46.50 Refraction 33.939 24 -442.36880 -35.635425 Refraction 26.789 340 25 0.00000 35.635425 Reflection 26.903 L10 26 -442.36880 19.000000 1.804198 46.50 Refraction 58.075 27 -188.49008 51.551139 Refraction 63.986 350 28* 52.78429 -155.000000 Reflection 144.673 S 29 0.00000 0.000000 Refraction 1330.167
[0080] The aspherical coefficients are as follows:
[0081] Page numbers 22 28 Conic constant 1.061689E-01 -4.787871E+00 The coefficient of the fourth order is 2.073994E-06 -2.904389E-08 Coefficient of the 6th order: -4.391544E-10 1.909389E-12 The coefficient of the 8th order is 1.949004E-13 -8.308591E-17 The coefficient of the 10th order is -4.812829E-17, which is 2.11295E-21. The coefficient of the 12th degree is 7.116146E-21 -2.328039E-26
[0082] When the focal length of the first reflective surface 330 of the first reflective optical system 33 is f1, the focal length of the second reflective surface 340 of the second reflective optical system 34 is f2, and the focal length of the third reflective surface 350 of the third reflective optical system 35 is f3, the data for the projection optical system 3B of Example 2 is as follows.
[0083] f1 32.790mm f2 ∞ mm f3 -26.392mm
[0084] The projection distance of the projection optical system 3B in Example 2 is as follows:
[0085] Projection distance: 155,000 mm
[0086] In this example, the projection optical system 3B satisfies the following condition (1) when the focal length of the first reflective optical system is f1, the focal length of the second reflective optical system is f2, and the focal length of the third reflective optical system is f3. |f2|>|f1|>|f3|···(1)
[0087] In this example, |f1| 32.790mm |f2| ∞ mm |f3| 26.392mm Therefore, the projection optical system 3B in this example satisfies condition (1).
[0088] (Effects and Benefits) In this example, the multiple lenses L1 to L10 include lens L9, which is positioned on the reduction side relative to lens L10. The second reflective surface 340 is positioned between lens L9 and lens L10 in the first direction Z1. Therefore, compared to the case where the second reflective surface 340 is provided on the magnification side lens surface of lens L9, the alignment of the second reflective surface 340 becomes easier when incorporating the projection optical system 3B into the projector 1. Furthermore, the second reflective surface 340 has a planar shape. Therefore, the manufacturing of the second reflective surface 340 becomes easier.
[0089] Since the projection optical system 3B in this example satisfies condition (1), it can obtain the same effects as the projection optical system 3A in Example 1. Figure 6 shows the MTF on the magnified side of the projection optical system 3B. As shown in Figure 6, the projection optical system 3B in this example has high resolution.
[0090] [Example 3] Figure 7 is a ray diagram of the projection optical system 3C of Embodiment 3. As shown in Figure 7, the projection optical system 3C consists of a first optical system 31 and a second optical system 32, in order from the reduction side to the enlargement side. The first optical axis N of the first optical system 31 and the second optical axis M of the second optical system 32 coincide.
[0091] The first optical system 31 is a refractive optical system with positive power. The first optical system 31 consists of multiple lenses. Specifically, the first optical system 31 consists of 10 lenses L1 to L10. Lenses L1 to L10 are arranged in this order from the reduction side to the magnification side. An aperture 51 is positioned between lens L4 and lens L5.
[0092] Lens L1 has positive power. Lens L1 is a meniscus lens. Lens L1 has a concave shape on the retracting side and a convex shape on the magnifying side. Lens L2 has positive power. Lens L2 has convex shapes on both the retracting and magnifying sides.
[0093] Lens L3 has negative power. Lens L3 has a concave shape on its reducing and expanding surfaces. Lens L4 has positive power. Lens L4 has a convex shape on its reducing and expanding surfaces. Lenses L3 and L4 are joined together to form a cemented lens L21.
[0094] Lens L5 has positive power. Lens L5 has convex shapes on its retraction and magnification surfaces. Lens L6 has negative power. Lens L6 has a concave shape on its retraction surface and a convex shape on its magnification surface. Lens L7 has positive power. Lens L7 has convex shapes on its retraction and magnification surfaces. Lens L8 has negative power. Lens L8 is a meniscus lens. Lens L8 has a concave shape on its retraction surface and a convex shape on its magnification surface.
[0095] Lens L9 (second lens) has positive power. Lens L9 is a meniscus lens. Lens L9 has a convex shape on the reducing side and a concave shape on the expanding side. Lens L9 has an aspherical shape on the expanding side. Lens L9 comprises a first portion 41 on one side with respect to the first optical axis N and a second portion 42 on the other side. The first portion 41 is a light-transmitting portion that functions as part of the first optical system 31. More specifically, the first portion 41 is a light-transmitting portion that functions as a refractive lens of the first optical system 31. The second portion 42 is a reflective portion that functions as the second reflective surface 340.
[0096] Lens L10 (first lens) has positive power. Lens L10 is a meniscus lens. Lens L10 has a concave shape on the reducing side and a convex shape on the expanding side. All of the lenses L1 to L10 that constitute the first optical system 31 have a shape that is rotationally symmetric with respect to the first optical axis N of the first optical system 31 as the axis of rotation.
[0097] The second optical system 32 has a first reflective optical system 33, a second reflective optical system 34, and a third reflective optical system 35 in order from the first optical system 31, along the optical path of the light rays emitted from the first optical system 31. Here, the lens L10 is positioned in the first direction Z1 between the first reflective optical system 33 and the second reflective optical system 34, and between the second reflective optical system 34 and the third reflective optical system 35.
[0098] The first reflective optical system 33 is positioned on the magnified side of the first optical system 31. The first reflective optical system 33 is located downward Y2 with respect to the second optical axis M. The first reflective optical system 33 has a first reflective surface 330 which has a concave shape. The first reflective surface 330 has an aspherical shape.
[0099] The second reflective optical system 34 is positioned on the optical path, on the magnifying side of the first reflective optical system 33. The second reflective optical system 34 is located above Y1 with respect to the second optical axis M. The second reflective optical system 34 has a second reflective surface 340 having a concave shape. The second reflective surface 340 is provided on the magnifying side lens surface 420 of the second portion 42 of the lens L9. Therefore, the second reflective surface 340 has an aspherical shape. The second reflective surface 340 is formed by a reflective coating layer provided on the magnifying side lens surface 420 of the second portion 42.
[0100] The third reflective optical system 35 is positioned on the optical path, on the enlarged side of the second reflective optical system 34. The third reflective optical system 35 is located above Y1 with respect to the second optical axis M. The third reflective optical system 35 has a third reflective surface 350 which has a convex shape. The third reflective surface 350 has an aspherical shape.
[0101] The first reflective surface 330, the second reflective surface 340, and the third reflective surface 350 constituting the second optical system 32 have a shape that is rotationally symmetric with respect to the second optical axis M of the second optical system 32 as the axis of rotation.
[0102] Light rays from the liquid crystal panel 18 pass through the first optical system 31 and the second optical system 32 in that order. Between the first optical system 31 and the second optical system 32, the light rays pass below Y2 of the first optical axis N and head towards the first reflective surface 330 of the second optical system 32.
[0103] Light rays that reach the first reflective surface 330 are reflected across the first optical axis N upward Y1 and toward the second direction Z2 and upward Y1. Light rays reflected by the first reflective surface 330 pass through the lens L10 and reach the second reflective surface 340. Light rays that reach the second reflective surface 340 are reflected toward the first direction Z1 and upward Y1. Light rays reflected by the second reflective surface 340 pass through the lens L10 and reach the third reflective surface 350. Light rays that reach the third reflective surface 350 are reflected toward the second direction Z2 and upward Y1. Light rays reflected by the third reflective surface 350 are amplified by the third reflective surface 350 and reach the screen S.
[0104] Assuming that the F-number of the projection optical system 3C is FNo and the maximum half-angle of view of the entire lens system is ω, the data for the projection optical system 3C of Example 3 is as follows.
[0105] Fno 1.433 ω 80.457°
[0106] The lens data for projection optical system 3C is as follows. The surface numbers are assigned sequentially from the reduction side to the enlargement side. The symbols are those for the liquid crystal panel, dichroic prism, lens, first reflecting surface, second reflecting surface, third reflecting surface, and screen. R is the radius of curvature. D is the axial spacing. nd is the refractive index. νd is the Abbe number. Y is the effective radius. The units for R, D, and Y are mm.
[0107] Code plane number RD nd vd Mode Y 18 0 0.00000 3.000000 Refraction 19 1 0.00000 25.750000 1.516330 64.14 Refraction 11.623 2 0.00000 5.500921 Refraction 17.017 L01 3 -66.02661 6.000000 1.903658 31.32 Refraction 18.000 4 -35.31143 0.100000 Refraction 18.985 L02 5 42.65748 8.000000 1.969346 18.11 Refraction 19.852 6 -1169.06825 13.341182 Refraction 19.225 L03 7 -63.97830 2.000000 1.986125 16.48 Refraction 13.489 L04 8 33.87145 10.217155 1.472590 81.12 Refraction 12.901 9 -33.17772 18.422090 Refraction 13.000 51,L05 10 39.23909 7.000000 1.438022 94.60 Refraction 13.000 11 -117.65820 32.866322 Refraction 13.532 L06 12 -28.56052 6.702939 1.882780 33.40 Refraction 17.426 13 -47.97692 14.148390 Refraction 20.704 L07 14 129.72400 7.000000 1.982136 16.81 Refraction 28.569 15 -362.02294 9.107801 Refraction 28.703 L08 16 -55.17402 6.921911 1.986125 16.48 Refraction 28.746 17 -71.36157 67.992188 Refraction 31.120 L09 18 289.04180 8.000000 1.986125 16.48 Refraction 41.451 19* 461.29891 20.572641 Refraction 41.403 L10 20 -241.32846 19.000000 1.448364 89.89 Refraction 41.926 21 -135.63243 60.926881 Refraction 43.245 330 22* -64.15676 -60.926881 Reflection 48.611 L10 23 -135.63243 -19.000000 1.448364 89.89 Refraction 19.080 24 -241.32846 -20.572641 Refraction 26.092 340 25* 461.29891 20.572641 Reflection 42.654 L10 26 -241.32846 19.000000 1.448364 89.89 Refraction 53.351 27 -135.63243 48.356460 Refraction 59.878 350 28* 53.00842 -155.000000 Reflection 138.968 S 29 0.00000 0.000000 Refraction 1330.080
[0108] The aspherical coefficients are as follows:
[0109] Page numbers 19 22 25 28 Conic constant 6.166722E+01 3.383186E-02 6.166722E+01 -4.559562E+00 The coefficient of the fourth order is -3.115222E-07 1.809685E-06 -3.115222E-07 -3.095255E-08 Coefficient of the 6th order: 5.312844E-11 -3.658264E-10 5.312844E-11 1.835285E-12 8th order coefficient -1.756324E-14 2.037076E-13 -1.756324E-14 -7.421759E-17 The coefficient of the 10th order is -5.418827E-17, which equates to 1.78666E-21. The coefficient of the 12th degree is 7.93418E-21 -1.910778E-26
[0110] When the focal length of the first reflective surface 330 of the first reflective optical system 33 is f1, the focal length of the second reflective surface 340 of the second reflective optical system 34 is f2, and the focal length of the third reflective surface 350 of the third reflective optical system 35 is f3, the data for the projection optical system 3C of Example 3 is as follows.
[0111] f1 32.078mm f2 230.649mm f3 -26.504mm
[0112] The projection distance of the projection optical system 3C in Example 3 is as follows:
[0113] Projection distance: 155,000 mm
[0114] In this example, the projection optical system 3C satisfies the following condition (1) when the focal length of the first reflective optical system is f1, the focal length of the second reflective optical system is f2, and the focal length of the third reflective optical system is f3. |f2|>|f1|>|f3|···(1)
[0115] In this example, |f1| 32.078mm |f2| 230.649mm |f3| 26.504mm Therefore, the projection optical system 3C in this example satisfies condition (1).
[0116] (Effects and Benefits) In this example, the second reflective surface 340 has an aspherical shape. Therefore, aberrations occurring in the projection optical system 3C can be corrected more effectively.
[0117] Since the projection optical system 3C in this example satisfies condition (1), it can obtain the same effects as the projection optical system 3A in Example 1. Figure 8 shows the MTF on the magnified side of the projection optical system 3C. As shown in Figure 8, the projection optical system 3C in this example has high resolution.
[0118] [Other examples] In the above embodiment, the first reflective surface 330 and the third reflective surface 350 were described as separate components, but a single component may comprise both the first reflective surface 330 and the third reflective surface 350.
[0119] [Summary of this disclosure] A summary of this disclosure is provided below.
[0120] (Note 1) It comprises a first optical system consisting of multiple lenses, and a second optical system, arranged in order from the reduction side to the magnification side. The 1st optical system has positive power, The second optical system has a first reflective optical system, a second reflective optical system, and a third reflective optical system in order from the first optical system, along the optical path of the light rays emitted from the first optical system. The first reflective optical system has a first reflective surface having a concave, aspherical shape, The second reflective optical system has a second reflective surface having a concave or planar shape, The third reflective optical system has a third reflective surface having a convex, aspherical shape, A projection optical system characterized in that, when the focal length of the first reflective optical system is f1, the focal length of the second reflective optical system is f2, and the focal length of the third reflective optical system is f3, the following condition (1) is satisfied. |f2|>|f1|>|f3|···(1)
[0121] As a result, the projection optical system 3 satisfies condition (1), and the projection distance can be shortened. That is, by making the absolute value of the focal length f3 of the third reflecting surface smaller than the absolute value of the focal length f1 of the first reflecting surface and the absolute value of the focal length f2 of the second reflecting surface 340, the reflection angle of light rays at the third reflecting surface can be increased, and thus the projection distance of the projection optical system can be shortened.
[0122] (Note 2) The projection optical system according to Appendix 1, characterized in that the maximum effective radius of the third reflective surface is less than 150 mm.
[0123] This allows for higher machining precision of the third reflective surface. As a result, the magnified image projected onto the screen by the projection optical system can be made clearer.
[0124] (Note 3) The plurality of lenses include a first lens having positive power that is positioned on the magnification side, The first lens is positioned between the first reflective optical system and the second reflective optical system in a first direction along the first optical axis of the first optical system. The projection optical system according to Appendix 1 or 2, characterized in that the light rays reflected by the first reflective optical system pass through the first lens and reach the second reflective optical system.
[0125] As a result, the first lens can control the spread and angle of the light rays reflected by the first reflecting surface, thereby reducing the on-axis distance between the first and second reflecting surfaces. Furthermore, the first lens can effectively correct various aberrations of the light rays reflected by the first reflecting surface.
[0126] (Note 4) The first lens is positioned between the second reflective optical system and the third reflective optical system in the first direction. The projection optical system according to Appendix 3, characterized in that the light rays reflected by the second reflective optical system pass through the first lens and reach the third reflective optical system.
[0127] As a result, the first lens can control the spread and angle of the light rays reflected by the second reflecting surface, thereby reducing the on-axis distance between the second and third reflecting surfaces. Furthermore, the first lens can effectively correct various aberrations of the light rays reflected by the second reflecting surface.
[0128] (Note 5) The plurality of lenses include a second lens positioned on the reduction side relative to the first lens, The second lens has a first portion on one side with respect to the first optical axis and a second portion on the other side. The first part is a light-transmitting portion that functions as part of the first optical system, The projection optical system according to appendix 3 or 4, characterized in that the second part is a reflective portion that functions as the second reflective surface.
[0129] As a result, the second lens serves both as a refractive lens and a second reflective surface, which reduces the number of optical components and simplifies the configuration of the projection optical system 3.
[0130] (Note 6) The plurality of lenses include a second lens positioned on the reduction side relative to the first lens, The projection optical system according to appendix 3 or 4, characterized in that the second reflective surface is positioned between the first lens and the second lens in the first direction.
[0131] Therefore, compared to the case where the second reflective surface is provided on the second lens, aligning the second reflective surface becomes easier when placing it in the projection optical system.
[0132] (Note 7) The projection optical system according to any one of the appendices 3 to 6, characterized in that the plurality of lenses have a shape that is rotationally symmetric with respect to the first optical axis.
[0133] This makes it easier to manufacture each lens in the first optical system. It also makes it easier to precisely position each lens in the first optical system.
[0134] (Note 8) The projection optical system according to Appendix 7, characterized in that the first reflective surface, the second reflective surface, and the third reflective surface have a shape that is rotationally symmetric with respect to the second optical axis of the second optical system as the axis of rotation.
[0135] This facilitates the manufacturing of each reflective surface in the second optical system. Furthermore, it makes it easier to precisely position each reflective surface in the second optical system.
[0136] (Note 9) The projection optical system according to Appendix 8, characterized in that the first optical axis and the second optical axis coincide.
[0137] This makes it easier to precisely position the first and second optical systems.
[0138] (Note 10) A projection optical system described in any one of the appendices 1 to 9, An image forming unit that forms a projected image on the reduction-side imaging plane of the projection optical system, A projector characterized by having the following features. [Explanation of symbols]
[0139] 1…Projector, 2…Image forming unit, 3·3A·3B·3C…Projection optical system, 4…Control unit, 6…Image processing unit, 7…Display drive unit, 10…Light source, 11…Integrator lens, 12…Integrator lens, 13…Polarization conversion element, 14…Superimposed lens, 15…Dichroic mirror, 16…Reflective mirror, 17R…Field lens, 17G…Field lens, 17B…Field lens, 18(18B·18R·18G)…Liquid crystal panel, 19…Cross dichroic prism 21...Dichroic mirror, 22...Relay lens, 23...Reflective mirror, 24...Relay lens, 25...Reflective mirror, 31...First optical system, 32...Second optical system, 33...First reflecting optical system, 34...Second reflecting optical system, 35...Third reflecting optical system, 41...First part, 42...Second part, 51...Aperture diaphragm, 330...First reflecting surface, 340...Second reflecting surface, 350...Third reflecting surface, 420...Magnifying lens surface, L1~L10...Lenses, L21...Cemented lens, N...First optical axis, M...Second optical axis, S...Screen.
Claims
1. It comprises a first optical system consisting of multiple lenses, and a second optical system, arranged in order from the reduction side to the magnification side. The XL1 optical system has positive power, The plurality of lenses include a first lens having positive power that is positioned on the magnification side, The second optical system has, in order from the first optical system, a first reflective optical system, a second reflective optical system, and a third reflective optical system on the optical path of the light rays emitted from the first optical system. The first lens is positioned between the first reflective optical system and the second reflective optical system in a first direction along the first optical axis of the first optical system. The light rays reflected by the first reflective optical system pass through the first lens and reach the second reflective optical system. The first reflective optical system has a first reflective surface having a concave, aspherical shape, The second reflective optical system has a second reflective surface having a concave or planar shape, The third reflective optical system has a third reflective surface having a convex, aspherical shape, A projection optical system characterized in that, when the focal length of the first reflective optical system is f1, the focal length of the second reflective optical system is f2, and the focal length of the third reflective optical system is f3, the following condition (1) is satisfied. |f2|>|f1|>|f3|...(1)
2. The projection optical system according to claim 1, characterized in that the maximum effective radius of the third reflective surface is less than 150 mm.
3. The first lens is positioned between the second reflective optical system and the third reflective optical system in the first direction. The projection optical system according to claim 1, characterized in that the light rays reflected by the second reflective optical system pass through the first lens and reach the third reflective optical system.
4. The plurality of lenses include a second lens positioned on the reduction side relative to the first lens, The second lens has a first portion on one side with respect to the first optical axis and a second portion on the other side. The first part is a light-transmitting portion that functions as part of the first optical system, The projection optical system according to claim 1, characterized in that the second part is a reflective portion that functions as the second reflective surface.
5. The plurality of lenses include a second lens positioned on the reduction side relative to the first lens, The projection optical system according to claim 1, characterized in that the second reflective surface is arranged between the first lens and the second lens in the first direction.
6. The projection optical system according to claim 1, characterized in that the plurality of lenses have a shape that is rotationally symmetric with respect to the first optical axis as the axis of rotation.
7. The projection optical system according to claim 6, characterized in that the first reflective surface, the second reflective surface, and the third reflective surface have a shape that is rotationally symmetric with respect to the second optical axis of the second optical system as the axis of rotation.
8. The projection optical system according to claim 7, characterized in that the first optical axis and the second optical axis coincide.
9. A projection optical system according to any one of claims 1 to 8, An image forming unit that forms a projected image on the reduction-side imaging plane of the projection optical system, A projector characterized by having the following features.