Projection optical system and projector

Abstract

To provide a short focus projection optical system that can be reduced in a size compared with prior ones.SOLUTION: A projection optical system comprises a first optical system and a second optical system in an order from a reduction side toward an enlargement side. The second optical system includes an optical element having a concave reflection surface and a first lens having negative power in an order from the reduction side toward the enlargement side. When an axial surface interval from an image forming element to the reflection surface is defined as OAL, a first distance from an optical axis to a maximum image height of the image forming element as imy, a maximum radius of the first lens as LL, a throw ratio obtained by dividing a projection distance by a second distance from the optical axis to the maximum image height of an enlarged image as TR, and the number of apertures in the image forming element as NA, both following conditional expressions (1) and (2) are satisfied. (1) TR≤0.3; (2) 35≤(OAL / imy)×(LL / imy)×TR×(1 / NA)≤60.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Patent Document 1 describes a projector that uses a projection optical system to enlarge a projection image displayed on an image display element and projects it onto a screen. The projection optical system comprises, in order from the reduction side to the enlargement side, a first refractive optical system, a reflective optical system, and a second refractive optical system. The first refractive optical system comprises multiple refractive lenses. The reflective optical system has a concave mirror and reflects light rays from the first refractive optical system toward the image display element in a direction intersecting the optical axis of the first refractive optical system. The second refractive optical system consists of a single refractive lens. The reflective lens is the enlargement-side lens located closest to the enlargement side in the projection optical system. Light rays from the concave mirror enter the enlargement-side lens in a direction intersecting the optical axis of the enlargement-side lens.

[0003] Among the examples of the projection optical system disclosed in Patent Document 1, the projection optical system with the shortest throw distance is 257.6 mm. The effective radius of the magnification-side lens of this projection optical system is 79.7 mm. The throw ratio of this projection optical system is 0.154. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-34690 Summary of the Invention [Problem to be solved by the invention]

[0005] The smaller the throw ratio of a projector's projection optical system, the shorter the throw distance when projecting an enlarged image of a given size. Therefore, the projection optical system installed in projectors used indoors and elsewhere requires a short-focus projection optical system with a throw ratio of 0.3 or less.

[0006] However, shortening the focal length of the projection optical system tends to increase aberrations on the magnification side. Therefore, it is necessary to increase the effective radius of the magnification-side lens, through which the light rays from the concave mirror pass obliquely, and correct the light rays for each image height in the magnification-side lens. However, if the magnification-side lens is enlarged to ensure the effective radius, the magnification-side lens will protrude more radially from the first optical axis of the first refractive optical system, making the entire projection optical system thicker. This hinders the miniaturization of projectors incorporating the projection optical system. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the projection optical system of the present invention includes an image pickup device arranged on a reduction-side conjugate plane. Projection optics for enlarging the projected image formed by the forming element and projecting the enlarged image onto the enlargement-side conjugate plane the optical system includes, in order from the reduction side to the enlargement side, a first optical system and a second optical system, The first optical system includes a diaphragm, and the second optical system includes, in order from the reduction side to the enlargement side, The optical element has a concave reflecting surface, and a first lens has a negative power, Between the optical system and the second optical system, a center conjugate to the reduction-side conjugate surface and the enlargement-side conjugate surface is provided. An intermediate image is formed, and the reduction side of the first optical system is telecentric, and the image forming The on-axis surface distance from the element to the reflecting surface is defined as OAL, and the maximum image of the image forming element is defined as The first distance to the target is defined as imy, the maximum radius of the first lens is defined as LL, and the projection distance is defined as The throw ratio, which is calculated by dividing the maximum image height of the enlarged image by a second distance from the optical axis, is defined as TR. If the numerical aperture of the image forming element is NA, the following conditional expressions (1) and (2) must both be satisfied: It is characterized by: TR≦0.3 (1) 35≦(OAL / imy)×(LL / imy)×TR×(1 / NA)≦60 (2) The projection optical system of the present invention also includes a projection image formed by an image forming element disposed on the reduction-side conjugate plane. In a projection optical system for enlarging an image and projecting the enlarged image onto an enlargement-side conjugate plane, The first optical system includes a first optical system and a second optical system, in that order toward the enlargement side. The first optical system includes a diaphragm. The second optical system has a concave reflecting surface in order from the reduction side to the enlargement side. an optical element; and a first lens having negative power, wherein the first optical system and the second optical system An intermediate image conjugate with the reduction-side conjugate surface and the enlargement-side conjugate surface is formed between the The reduction side of the optical system is telecentric, and the distance from the image forming element to the reflecting surface is The on-axis surface distance is OAL, and the first distance from the optical axis to the maximum image height of the image forming element is im y, the maximum radius of the first lens is LL, and the projection distance from the optical axis to the maximum point of the enlarged image is 1 / 2. The throw ratio divided by the second distance to the large image height is TR, and the numerical aperture of the image forming element is N If A satisfies both of the following conditional expressions (1) and (2), TR≦0.3 (1) 35≦(OAL / imy)×(LL / imy)×TR×(1 / NA)≦60 (2) The second lens arranged on the most enlarged side in the first optical system is separate from the first lens. the second lens is formed on the body, and the second lens is disposed between the reflecting surface and the first lens in the optical axis direction. and The projection optical system of the present invention also includes a projection image formed by an image forming element disposed on the reduction-side conjugate plane. In a projection optical system for enlarging an image and projecting the enlarged image onto an enlargement-side conjugate plane, The first optical system includes a first optical system and a second optical system, in that order toward the enlargement side. The first optical system includes a diaphragm. The second optical system has a concave reflecting surface in order from the reduction side to the enlargement side. an optical element; and a first lens having negative power, wherein the first optical system and the second optical system An intermediate image conjugate with the reduction-side conjugate surface and the enlargement-side conjugate surface is formed between the The reduction side of the optical system is telecentric, and the distance from the image forming element to the reflecting surface is The on-axis surface distance is OAL, and the first distance from the optical axis to the maximum image height of the image forming element is im y, the maximum radius of the first lens is LL, and the projection distance from the optical axis to the maximum point of the enlarged image is 1 / 2. The throw ratio divided by the second distance to the large image height is TR, and the numerical aperture of the image forming element is N If A satisfies both of the following conditional expressions (1) and (2), TR≦0.3 (1) 35≦(OAL / imy)×(LL / imy)×TR×(1 / NA)≦60 (2) the first optical system includes a cemented lens on the enlargement side of the diaphragm, Academic.

[0008] Next, a projector of the present invention is characterized by comprising the above-described projection optical system and the image forming element that forms a projected image on the reduction-side conjugate plane of the projection optical system. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a projector including a projection optical system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a ray diagram of the projection optical system of the first embodiment. [Figure 3] 4 is a diagram showing lateral aberration at a reference distance of the projection optical system of Example 1. FIG. [Figure 4] 4A and 4B are diagrams illustrating spherical aberration, astigmatism, and distortion at a reference distance of the projection optical system of Example 1. [Figure 5] 4A and 4B are diagrams illustrating spherical aberration, astigmatism, and distortion at a short distance in the projection optical system of Example 1. [Figure 6] 4A and 4B are diagrams illustrating spherical aberration, astigmatism, and distortion at a long distance in the projection optical system of Example 1. [Figure 7] FIG. 10 is a ray diagram of the projection optical system of the second embodiment. [Figure 8] 10 is a diagram showing lateral aberration at a reference distance of the projection optical system of Example 2. FIG. [Figure 9] 10A and 10B are diagrams illustrating spherical aberration, astigmatism, and distortion at a reference distance of the projection optical system of Example 2. [Figure 10] 10A and 10B are diagrams illustrating spherical aberration, astigmatism, and distortion at a short distance in the projection optical system of Example 2. [Figure 11] 10A and 10B are diagrams illustrating spherical aberration, astigmatism, and distortion at a long distance in the projection optical system of Example 2. [Figure 12] FIG. 10 is a ray diagram of the projection optical system of the third embodiment. [Figure 13] 10 is a diagram showing lateral aberration at a reference distance of the projection optical system of Example 3. FIG. [Figure 14] 10A and 10B are diagrams illustrating spherical aberration, astigmatism, and distortion at a reference distance of the projection optical system of Example 3. [Figure 15] 10A and 10B are diagrams illustrating spherical aberration, astigmatism, and distortion at a short distance in the projection optical system of Example 3. [Figure 16] 10A and 10B are diagrams illustrating spherical aberration, astigmatism, and distortion at a long distance in the projection optical system of Example 3. FIG. [Figure 17] FIG. 10 is a ray diagram of the projection optical system of the fourth embodiment. [Figure 18] 10 is a diagram showing lateral aberration at a reference distance of the projection optical system of Example 4. FIG. [Figure 19] 10A and 10B are diagrams illustrating spherical aberration, astigmatism, and distortion at a reference distance of the projection optical system of Example 4. [Figure 20] 10A and 10B are diagrams illustrating spherical aberration, astigmatism, and distortion at a short distance in the projection optical system of Example 4. [Figure 21] 10A and 10B are diagrams illustrating spherical aberration, astigmatism, and distortion at a long distance in the projection optical system of Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0010] An optical system and a projector according to an embodiment of the invention will be described below with reference to the drawings.

[0011] (projector) 1 is a diagram showing a schematic configuration of a projector equipped with a projection optical system 3 of the present invention. As shown in Fig. 1, the projector 1 includes 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.

[0012] (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.

[0013] 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.

[0014] The image forming unit 2 includes a first dichroic mirror 15, a reflecting mirror 16, a field The first dichroic mirror 15 includes a lens 17R and a liquid crystal panel 18R. The R light, which is a part of the light beam incident from the superimposing lens 14, is reflected and reflected from the superimposing lens 14. The first dichroic mirror 15 transmits the G and B light, which are part of the light beam that has been reflected. The R light is reflected by the reflecting mirror 16 and the field lens 17R and then reflected by the liquid crystal panel 18. The liquid crystal panel 18R is Image formation The liquid crystal panel 18R converts the R light into an image. A red projection image is formed by modulating the light according to the signal.

[0015] 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 part of the light beam from the first dichroic mirror 15, and transmits B light, which is a part of the light beam 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 forms a green projection image by modulating the G light in accordance with an image signal.

[0016] The image forming unit 2 includes a relay lens 22, a reflecting mirror 23, a relay lens 24, and a reflecting mirror 25. Laser 25, field lens 17B, LCD panel 18B and cross dichroic filter The B light transmitted through the second dichroic mirror 21 is reflected by the relay lens 22. , a reflecting mirror 23, a relay lens 24, a reflecting mirror 25, and a field lens 17B. The light then passes through the liquid crystal panel 18B and enters the liquid crystal panel 18B. Image formation It is a liquid crystal panel. The panel 18B modulates the B light in accordance with an image signal to form a blue projection image.

[0017] 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.

[0018] The projection optical system 3 projects the projection image synthesized by the cross dichroic prism 19 onto the screen S in an enlarged scale.

[0019] 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.

[0020] 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.

[0021] (Projection optical system) Next, we will explain the projection optical system 3. As shown in Fig. 1, a screen S is disposed at the enlargement-side conjugate plane of the projection optical system 3. Liquid crystal panels 18R, 18G, and 18B are disposed at the reduction-side conjugate plane of the projection optical system 3.

[0022] In the following, examples 1 to 4 will be described as configuration examples of the projection optical system 3 mounted on the projector 1.

[0023] Example 1 2 is a ray diagram of the projection optical system 3A of Example 1. In the ray diagrams of the projection optical systems 3 of Examples 1 to 4, the liquid crystal panel 18R, the liquid crystal panel 18G, and the liquid crystal panel 18B are represented as the liquid crystal panel 18. As shown in FIG. 2, the projection optical system 3A of this example is made up of, in order from the reduction side to the enlargement side, a first optical system 31 and a second optical system 32. The second optical system 32 is disposed on the optical axis N of the first optical system 31.

[0024] For convenience, in the following description, three mutually perpendicular axes are referred to as the X-axis, Y-axis, and Z-axis. The Z-axis coincides with the optical axis N of the first optical system 31. The Z-axis direction is a direction along the optical axis N. In the Z-axis direction, the side where the first optical system 31 is located is referred to as the first direction Z1, and the side where the second optical system 32 is located is referred to as the second direction Z2. The Y-axis extends along the screen S. The Y-axis direction is a vertical direction, with one side in the Y-axis direction referred to as the upper direction Y1 and the other side referred to as the lower direction Y2. The X-axis extends in the width direction of the screen.

[0025] The first optical system 31 is a refractive optical system. The first optical system 31 is made up of 17 lenses L1 to L17. The lenses L1 to L17 are arranged in this order from the reduction side to the enlargement side. A diaphragm 51 is arranged between the lenses L7 and L8.

[0026] Lens L6 has aspherical surfaces on both sides. Lens L9 has aspherical surfaces on both sides. Lens L16 (third lens) has aspherical surfaces on both sides. Lens L17 (second lens) has aspherical surfaces on both sides. Lenses L2 and L3 are cemented together to form a cemented lens L21. Lenses L4 and L5 are cemented together to form a cemented lens L22. Lenses L11 and L12 are cemented together to form a cemented lens L23. Lenses L14 and L15 are cemented together to form a cemented lens L24.

[0027] The second optical system 32 includes an optical element 33 and a first lens 34. The optical element 33 and the first lens 34 are arranged in this order from the reduction side to the enlargement side. The optical element 33 includes a reflective surface 40 facing the reduction side. The reflective surface 40 has a concave shape recessed in the second direction Z2. The reflective surface 40 has an aspherical shape. As shown in FIG. 2, the reflective surface 40 is located below the optical axis N at Y2. The reflective surface 40 is formed by providing a reflective coating layer (reflective layer) on the outer surface of the optical element 33 in the first direction Z1. The reflective surface 40 reflects light on the surface of the optical element 33 in the Z1 direction.

[0028] The first lens 34 is positioned in the first direction Z1 from the optical element 33 and is disposed above the optical axis N at a position Y1. The first lens 34 has negative power. The first lens 34 has a convex shape on the magnification side and a concave shape on the reduction side. The first lens 34 has aspherical shapes on both sides.

[0029] Here, the liquid crystal panel 18 of the image forming unit 2 is disposed on a reduction-side conjugate plane of the projection optical system 3A. The screen S is disposed on an enlargement-side conjugate plane of the projection optical system 3A.

[0030] The liquid crystal panel 18 forms a projected image in an image forming plane perpendicular to the optical axis N of the first optical system 31. The liquid crystal panel 18 is disposed at a position offset upward Y1 with respect to the optical axis N of the first optical system 31. Therefore, the projected image is formed at a position offset upward Y1 with respect to the optical axis N.

[0031] Light rays from the liquid crystal panel 18 pass through the first optical system 31 and the second optical system 32 in this order. Between the first optical system 31 and the second optical system 32, the light rays pass below Y2 on the optical axis N. As a result, the light rays pass through the second optical system 32 toward the reflective surface 40. The light rays that reach the reflective surface 40 are reflected in the first direction Z1 and upward Y1. The light rays that are reflected by the reflective surface 40 cross the optical axis N upward Y1 toward the first lens 34. The light rays that pass through the first lens 34 are expanded by the first lens 34 and reach the screen S.

[0032] Here, the lens L17 of the first optical system 31 is disposed between the reflecting surface 40 and the first lens 34 in the direction of the optical axis N. The intermediate image 30 is formed between the lens L17 and the reflecting surface 40.

[0033] The projection optical system 3A is telecentric on the reduction side of the first optical system 31. Telecentricity means that the central ray of each light beam passing between the first optical system 31 and the liquid crystal panel 18 arranged on the reduction-side conjugate plane is parallel to the optical axis or approximately parallel to the optical axis.

[0034] Here, the projection optical system 3A can change the projection distance. When the projection distance is changed, focusing is performed by moving the eight lenses L10 to L17 of the first optical system 31 along the optical axis N. During focusing, the lenses L10, L11, and L12 are moved together. Furthermore, during focusing, the lenses L13, L14, and L15 are moved together.

[0035] The numerical aperture of the liquid crystal panel 18 is NA, the first distance from the optical axis N to the maximum image height of the liquid crystal panel 18 is imy, the second distance from the optical axis N to the maximum image height of the enlarged image projected onto the screen S is scy, the projection distance which is the distance from the first lens 34 to the screen S is PD, the projection magnification obtained by dividing the second distance by the first distance is M, the throw ratio obtained by dividing the projection distance by the second distance is TR, the axial surface distance from the liquid crystal panel 18 to the reflective surface 40 is OAL, and the maximum radius of the first lens 34 is LL. The data of the projection optical system 3A is as follows:

[0036] NA 0.3125 imy 11.7mm scy 1463mm PD 283.1mm M 125 TR 0.194 OAL 203mm LL 47.8mm

[0037] The lens data for the projection optical system 3A is as follows. Surface numbers are assigned in order from the reduction side to the enlargement side. The symbols refer to the LCD panel, dichroic prism, lens, optical element, first lens, and screen. Data for surface numbers that do not correspond to the LCD panel, dichroic prism, lens, optical element, first lens, and screen is dummy data. R is the radius of curvature. D is the on-axis surface spacing. C is the aperture radius, and twice the aperture radius is the diameter of the lens surface. R, D, and C are in mm.

[0038] Symbol Surface number Shape RD Glass material Refraction / Reflection C 18 0 Sphere Infinity 9.5000 Refraction 0.0000 19 1 Sphere Infinity 25.9100 SBSL7_OHARA Refraction 13.0371 2 Sphere Infinity 0.0000 Refraction 15.4259 L1 3 sphere 23.6460 8.4106 SFPL51_OHARA Refraction 16.3497 4 sphere -163.6273 0.1000 Refraction 16.1238 L2 5 sphere 24.1479 5.7206 SFSL5_OHARA refraction 14.0000 L3 6 sphere 113.0998 1.0000 STIH6_OHARA Refraction 13.1404 7 sphere 34.7820 0.1000 refraction 12.2395 L4 8 sphere 19.4148 7.7264 SBSL7_OHARA Refraction 11.6173 L5 9 ball -25.1932 0.9500 TAFD25_HOYA Refractive index 10.9949 10 sphere 25.2418 0.2000 refraction 10.0083 L6 11 Aspheric 16.8372 4.4033 LBAL35_OHARA Refraction 10.1020 12 Aspheric 40.5023 1.0000 Refractive 9.1836 L7 13 Sphere 19.4289 2.3917 SFSL5_OHARA Refraction 9.1301 14 Sphere 32.7745 4.0203 Refraction 8.8594 51 15 Sphere Infinity 0.1043 Refraction 8.3951 L8 16 sphere 101.2882 3.7504 STIH53_OHARA Refraction 8.5137 17 Sphere -22.7544 0.1000 Refraction 8.6718 L9 18 Aspheric -21.2771 6.0000 LLAM60_OHARA Refractive 8.6423 19 Aspheric 103.2802 Variable Spacing 1 Refractive 9.5014 L10 20 Sphere 22.9132 2.0346 STIM22_OHARA Refraction 10.9384 21 Sphere 26.8895 14.2089 Refraction 10.9386 L11 22 sphere 57.1566 5.3002 STIM2_OHARA refraction 16.5000 L12 23 Sphere -129.3659 1.0000 STIH6_OHARA Refraction 16.7439 24 spheres 677.5558 variable spacing 2 refraction 17.0582 L13 25 sphere 47.4289 9.6511 STIM22_OHARA refraction 18.3999 26 Sphere -46.5818 0.1000 Refraction 18.3651 L14 27 Sphere -67.5767 8.1053 STIL25_OHARA Refraction 17.8500 L15 28 sphere -21.6948 1.0000 STIH6_OHARA Refraction 17.7177 29 Sphere 170.7327 Variable Spacing 3 Refraction 18.7445 L16 30 Aspheric -24.7550 3.0000 'Z-E48R' Refraction 18.8159 31 Aspheric 101.4895 Variable Spacing 4 Refractive 21.3950 L17 32 Aspheric 257.2804 8.0000 'Z-E48R' Refractive 25.6568 33 Aspheric 63.8637 Variable Spacing 5 Refractive 28.1976 40 34 Aspheric -28.5800 -50.8918 Reflection 41.2214 34 35 Aspheric 59.7480 -7.0000 'Z-E48R' Refractive 37.2465 36 Aspheric 67.7207 Variable Spacing 6 Refractive 47.7801 S 37 Sphere Infinity 0.0000 Refraction 1985.1150

[0039] Here, the projection optical system 3A of this example can change the projection distance between a reference distance, a short distance shorter than the reference distance, and a long distance longer than the reference distance. When the projection distance is changed, focusing is performed by moving the eight lenses L10 to L17 of the first optical system 31 along the optical axis N. Note that when focusing is performed to change the projection distance from a short distance to a long distance, the lenses L10, L11, and L12 move toward the enlargement side along the optical axis N. When focusing is performed in the same way, the lenses L13, L14, and L15 move toward the enlargement side along the optical axis N. When focusing is performed in the same way, the lens L16 moves toward the enlargement side along the optical axis N. When focusing is performed in the same way, the lens L17 moves toward the reduction side along the optical axis N.

[0040] Variable distance 1, variable distance 2, variable distance 3, variable distance 4, variable distance 5, and variable distance 6 at each projection distance when focusing are shown below. Variable distance 1 is the axial surface distance between lens L9 and lens L10. Variable distance 2 is the axial surface distance between lens L12 and lens L13. Variable distance 3 is the axial surface distance between lens L15 and lens L16. Variable distance 4 is the axial surface distance between lens L16 and lens L17. Variable distance 5 is the axial surface distance between lens L17 and reflecting surface 40. Variable distance 6 is the projection distance.

[0041] Reference distance Near distance Far distance Variable Interval 1 1.1069 0.8768 1.2979 Variable Interval 2 0.8042 0.1000 1.4634 Variable Interval 3 6.2530 6.4325 6.0906 Variable Interval 4 20.9176 21.6588 20.1541 Variable Interval 5 39.8875 39.8713 39.9334 Variable Interval 6 -283.0000 -217.0000 -401.0000

[0042] The aspherical coefficients are as follows:

[0043] Face number S11 S12 S18 S19 Radius of curvature (R) 16.8372 40.5023 -21.2771 103.2802 コーニックfixed number (K) 8.76367E-01 1.40552E+01 -1 -90 4 times -2.95336E-06 8.91728E-05 4.09548E-05 7.14087E-05 6 times 5.97014E-08 2.72315E-07 -4.12331E-07 -3.41490E-07 8 times 7.38171E-11 -7.34670E-10 1.32697E-09 1.10129E-09 10 times 1.42398E-11

[0044] Face number S30 S31 S32 S33 Radius of curvature (R) -24.7550 101.4895 257.2804 63.8637 コーニックfixed number (K) 0 0 90 0.00000E+00 4 times 9.42799E-05 1.68772E-05 -4.34174E-05 -6.79148E-05 6 times -3.84902E-07 -1.78130E-07 1.23752E-07 1.63921E-07 8 times 8.80106E-10 3.67946E-10 -2.74764E-10 -2.83439E-10 10 times -8.42504E-13 -3.17825E-13 3.77647E-13 2.91903E-13 12 times -2.03100E-16 -1.17046E-16 14 times 6.56482E-22

[0045] Face number S34 S35 S36 Curvature radius (R) -28.5800 59.7480 67.72067982 コーニックfixed number (K) -1.00000E+00 2.18390E-01 -0.004229729 Quaternary 3.62586E-06 2.99552E-05 1.47026E-05 6th order -6.05961E-09 -9.57606E-08 -3.80264E-08 8th order 7.45065E-12 1.64656E-10 4.62847E-11 10th order -5.45419E-15 -1.61839E-13 -3.18524E-14 12th order 2.08318E-18 9.28635E-17 1.29283E-17 14th -3.40484E-22 -2.85578E-20 -2.89715E-21 16th order 3.61610E-24 2.80551E-25

[0046] Here, the projection optical system 3A of this example has OAL as the axial surface distance from the liquid crystal panel 18 to the reflecting surface 40, imy as the first distance from the optical axis N to the maximum image height of the liquid crystal panel 18, LL as the maximum radius of the first lens 34, TR as the throw ratio obtained by dividing the projection distance by the second distance from the optical axis N to the maximum image height of the enlarged image projected on the screen S, and NA as the numerical aperture of the liquid crystal panel 18, and satisfies all of the following conditional expressions (1) and (2): TR≦0.3 (1) 35≦(OAL / imy)×(LL / imy)×TR×(1 / NA)≦60 (2)

[0047] Even more preferably, the following conditional expressions (1) and (2') are both satisfied. TR≦0.3 (1) 35≦(OAL / imy)×(LL / imy)×TR×(1 / NA)≦53 (2')

[0048] In this example, OAL 203mm imy 11.7mm LL 47.8mm TR 0.194 NA 0.3125 Therefore, TR=0.194, which satisfies conditional expression (1). (OAL / imy)×(LL / imy)×TR×(1 / NA)=44, which satisfies conditional expression (2).

[0049] (Action and effect) The projection optical system 3A of this example enlarges a projection image formed by a liquid crystal panel 18 arranged on the reduction-side conjugate plane and projects the enlarged image on the enlargement-side conjugate plane. The projection optical system 3A of this example comprises, in order from the reduction side to the enlargement side, a first optical system 31 and a second optical system 32. The first optical system 31 comprises a diaphragm 51. The second optical system 32 comprises, in order from the reduction side to the enlargement side, an optical element 33 having a concave reflecting surface 40 and a first lens 34 having negative power. An intermediate image 30 conjugate to the reduction-side conjugate plane and the enlargement-side conjugate plane is formed between the first optical system 31 and the second optical system 32. The reduction side of the first optical system 31 is telecentric.

[0050] Furthermore, in the projection optical system 3A of this example, the axial surface distance from the liquid crystal panel 18 to the reflective surface 40 is OAL, the first distance from the optical axis N to the maximum image height of the liquid crystal panel 18 is imy, the maximum radius of the first lens 34 is LL, the throw ratio obtained by dividing the projection distance by the second distance from the optical axis N to the maximum image height of the enlarged image projected on the screen S is TR, and the numerical aperture of the liquid crystal panel 18 is NA, and the projection optical system 3A satisfies all of the following conditional expressions (1) and (2): TR≦0.3 (1) 35≦(OAL / imy)×(LL / imy)×TR×(1 / NA)≦60 (2)

[0051] The projection optical system 3A of this example satisfies conditional expression (1). Therefore, the projection optical system 3 is made short-focus. However, when the projection optical system is made short-focus, aberrations that occur on the magnification side tend to increase. Therefore, it is necessary to increase the effective radius of the magnification-side lens, through which the light rays from the concave mirror pass obliquely, and to correct the light rays for each image height in the magnification-side lens. However, if the magnification-side lens is made larger to ensure the effective radius, the amount by which the magnification-side lens protrudes radially from the first optical axis of the first refractive optical system increases, and the entire projection optical system becomes thicker.

[0052] In response to this problem, Throw The optical system 3A satisfies the conditional expression (2). By suppressing the amount of radial protrusion of the first lens 34 from the optical axis N, the projection optical system Since the overall thickness can be prevented from increasing, the projector equipped with the 3A projection optical system can be made smaller. In addition, the amount of protrusion of the first lens 34 from the optical axis N in the radial direction can be reduced. While maintaining the above, the first lens 34 can ensure an effective diameter capable of correcting the light beam for each image height. That is, when the conditional expression (2) is below the lower limit, the liquid crystal panel 18 The on-axis surface distance to the reflecting surface 40 and the lens diameter of the first lens 34 become too small. It becomes difficult to correct the light rays for each image height, and it becomes difficult to ensure the resolution performance of the projection optical system 3A. Furthermore, even if a lens with sufficient resolution is designed, it will be difficult to manufacture. Since high forming accuracy is required at the time of molding, there is a problem that mass production is not high. If the limit is exceeded, the on-axis surface distance from the liquid crystal panel 18 to the reflecting surface 40 and the The lens diameter becomes excessively large. In other words, the first lens 34 protrudes radially from the optical axis N. The projection amount becomes larger, so the entire projection optical system becomes thicker. Projectors are getting bigger.

[0053] Here, as a comparative example, Example 3 of Japanese Patent Application Laid-Open No. 2020-34690, a prior art document, will be considered. The projection optical system of the comparative example comprises, in order from the reduction side to the enlargement side, a first refractive optical system, a reflective optical system, and a second refractive optical system. The first refractive optical system comprises multiple refractive lenses. The reflective optical system has a concave mirror and reflects light rays from the first refractive optical system in a direction intersecting the optical axis of the first refractive optical system toward the image display element. The second refractive optical system consists of a single refractive lens. The reflective lens is the enlargement-side lens located closest to the enlargement side in the projection optical system. Light rays from the concave mirror enter the enlargement-side lens in a direction intersecting the optical axis of the enlargement-side lens. Data for the comparative example are as follows:

[0054] OAL 256mm imy 13.2mm LL 79.7mm TR 0.154 NA 0.25

[0055] In the comparative example, TR = 0.154. Therefore, the projection optical system of the comparative example satisfies conditional expression (1). However, in the comparative example, (OAL / imy) × (LL / imy) × TR × (1 / NA) = 72. Therefore, the projection optical system of the comparative example does not satisfy conditional expression (2). Therefore, when the throw ratio is the same, the lens diameter of the enlargement-side lens of the projection optical system of the comparative example is larger than the effective radius of the first lens of the projection optical system 3A of this example. In other words, the entire projection optical system of the comparative example is thicker than the entire projection optical system 3A of this example.

[0056] In the projection optical system 3A of this example, the reflecting surface 40 has a reflective coating layer (reflective layer) on its surface. Here, in a configuration in which the reflecting surface is provided inside the optical element 33, the shape accuracy of the enlargement-side lens surface on which the reflecting surface is provided depends on the shape accuracy of the optical element 33. In other words, to improve the shape accuracy of the enlargement-side lens surface, it is necessary to also improve the shape accuracy of the reduction-side lens surface. In contrast, since the reflecting surface 40 of the projection optical system 3A of this example is provided on the outer surface of the optical element 33, it is only necessary to improve the shape accuracy of the outer surface of the optical element 33. Therefore, it is easier to improve the shape accuracy of the reflecting surface of the reflecting surface 40 of this example compared to a configuration in which the reflecting surface is provided inside the optical element 33.

[0057] Furthermore, in a configuration in which the reflective surface is provided inside the optical element 33, the reflective surface is formed by forming a reflective coating layer on the magnification-side lens surface of the optical element 33 after molding the optical element 33. In this case, a support film layer must be provided between the reflective coating layer and the magnification-side lens surface. Providing the support film layer makes the reflective coating layer less likely to peel off from the magnification-side lens surface, but the presence of the support film layer makes the optical performance of the reflective surface more likely to deteriorate, leading to variations in the optical performance of the reflective surface during manufacturing. In contrast, in the projection optical system 3A of this example, the support film layer is provided on the side opposite the reflective surface side of the reflective coating layer, making the optical performance of the reflective surface 40 less likely to deteriorate. This makes it easier to stabilize the optical performance of the reflective surface 40 during manufacturing.

[0058] In the projection optical system 3A of this example, the lens L17 (second lens) located on the most enlarged side of the first optical system 31 is formed separately from the first lens 34. The lens L17 is located between the reflecting surface 40 and the first lens 34 in the direction of the optical axis N. That is, the lens L17 located on the most enlarged side of the first optical system 31 is located inside the second optical system 32 in the direction of the optical axis N, so the distance between the lens L17 and the reflecting surface 40 is short. This shortens the on-axis surface spacing from the liquid crystal panel 18 to the reflecting surface 40, thereby enabling the projection optical system 3A to be made more compact. Furthermore, the intermediate image 30 is formed between the lens L17 of the first optical system 31 and the reflecting surface 40 of the second optical system 32. Therefore, if the distance between the lens L17 and the reflecting surface 40 is short, it becomes easier to correct various aberrations of the intermediate image 30 at each image height.

[0059] The first optical system 31 also includes a lens L17 (second lens) and a lens L16 (third lens) located adjacent to the reduction side of the lens L17. The lenses L16 and L17 have aspherical shapes. The projection optical system 3A of this example focuses by moving the lenses L16 and L17 toward the enlargement side along the optical axis N to change the projection distance from a short distance to a long distance. Therefore, the projection optical system 3A moves the lenses L16 and L17, which correct various aberrations for each image height, along the optical axis N, thereby suppressing the occurrence of various aberrations during focusing. In addition, in a configuration in which focusing is performed by moving a non-aspherical lens along the optical axis N, a separate aspherical lens is required to correct various aberrations. However, in this example, the lenses L16 and L17, which move during focusing, have aspherical shapes, allowing the entire projection optical system to be compact.

[0060] Furthermore, the first optical system 31 includes a cemented lens L23 and a cemented lens L24 on the enlargement side of the diaphragm 51. Therefore, chromatic aberration can be corrected well.

[0061] FIG. 3 is a diagram showing lateral aberration of the projection optical system 3A at a reference distance. FIG. 4 is a diagram showing spherical aberration, astigmatism, and distortion of the projection optical system 3A at a reference distance. FIG. 5 is a diagram showing spherical aberration, astigmatism, and distortion of the projection optical system 3A at a close distance. FIG. 6 is a diagram showing spherical aberration, astigmatism, and distortion of the projection optical system 3A at a long distance. As shown in FIGS. 3 to 6, the projection optical system 3A of this example suppresses various aberrations in the magnified image.

[0062] Example 2 7 is a ray diagram of a projection optical system 3B of Example 2. As shown in Fig. 7, the projection optical system 3B of this example is made up of, in order from the reduction side to the enlargement side, a first optical system 31 and a second optical system 32. The second optical system 32 is disposed on the optical axis N of the first optical system 31.

[0063] The first optical system 31 is a refractive optical system. The first optical system 31 is made up of 16 lenses L1 to L16. The lenses L1 to L16 are arranged in this order from the reduction side to the enlargement side. A diaphragm 51 is arranged between the lenses L7 and L8.

[0064] Lens L6 has aspherical surfaces on both sides. Lens L9 has aspherical surfaces on both sides. Lens L15 (third lens) has aspherical surfaces on both sides. Lens L16 (second lens) has aspherical surfaces on both sides. Lenses L2 and L3 are cemented together to form cemented lens L21. Lenses L4 and L5 are cemented together to form cemented lens L22. Lenses L10 and L11 are cemented together to form cemented lens L23. Lenses L13 and L14 are cemented together to form cemented lens L24.

[0065] The second optical system 32 includes an optical element 33 and a first lens 34. The optical element 33 and the first lens 34 are arranged in this order from the reduction side to the enlargement side. The optical element 33 includes a reflective surface 40 facing the reduction side. The reflective surface 40 has a concave shape recessed in the second direction Z2. The reflective surface 40 has an aspherical shape. As shown in FIG. 7, the reflective surface 40 is located below the optical axis N at Y2. The reflective surface 40 is formed by providing a reflective coating layer (reflective layer) on the outer surface of the optical element 33 in the first direction Z1. The reflective surface 40 reflects light on the surface of the optical element 33 in the Z1 direction.

[0066] The first lens 34 is positioned in the first direction Z1 from the optical element 33 and is disposed above the optical axis N at a position Y1. The first lens 34 has negative power. The first lens 34 has a convex shape on the magnification side and a concave shape on the reduction side. The first lens 34 has aspherical shapes on both sides.

[0067] Here, the liquid crystal panel 18 of the image forming unit 2 is disposed on a reduction-side conjugate plane of the projection optical system 3B. The screen S is disposed on an enlargement-side conjugate plane of the projection optical system 3B.

[0068] The liquid crystal panel 18 forms a projected image in an image forming plane perpendicular to the optical axis N of the first optical system 31. The liquid crystal panel 18 is disposed at a position offset upward Y1 with respect to the optical axis N of the first optical system 31. Therefore, the projected image is formed at a position offset upward Y1 with respect to the optical axis N.

[0069] Light rays from the liquid crystal panel 18 pass through the first optical system 31 and the second optical system 32 in this order. Between the first optical system 31 and the second optical system 32, the light rays pass below Y2 on the optical axis N. As a result, the light rays pass through the second optical system 32 toward the reflective surface 40. The light rays that reach the reflective surface 40 are reflected in the first direction Z1 and upward Y1. The light rays that are reflected by the reflective surface 40 cross the optical axis N upward Y1 toward the first lens 34. The light rays that pass through the first lens 34 are expanded by the first lens 34 and reach the screen S.

[0070] Here, the lens L16 of the first optical system 31 is disposed between the reflecting surface 40 and the first lens 34 in the direction of the optical axis N. The intermediate image 30 is formed between the lens L16 and the reflecting surface 40.

[0071] In the projection optical system 3B, the reduction side from the first optical system 31 is telecentric.

[0072] Here, the projection optical system 3B can change the projection distance. When the projection distance is changed, 1 optical system 31 7 Pieces Re Lenses L10 to L16 are moved along the optical axis N for focusing. During focusing, the lenses L12, L13, and L14 are integrated. Move it to.

[0073] The numerical aperture of the liquid crystal panel 18 is NA, the first distance from the optical axis N to the maximum image height of the liquid crystal panel 18 is imy, the second distance from the optical axis N to the maximum image height of the enlarged image projected onto the screen S is scy, the projection distance which is the distance from the first lens 34 to the screen S is PD, the projection magnification obtained by dividing the second distance by the first distance is M, the throw ratio obtained by dividing the projection distance by the second distance is TR, the axial surface distance from the liquid crystal panel 18 to the reflective surface 40 is OAL, and the maximum radius of the first lens 34 is LL. The data of the projection optical system 3B is as follows:

[0074] NA 0.2778 imy 11.8mm scy 1462mm PD 288.6mm M 124 TR 0.197 OAL 189mm LL 36.5mm

[0075] The lens data for the projection optical system 3B is as follows. Surface numbers are assigned in order from the reduction side to the enlargement side. The symbols refer to the liquid crystal panel, dichroic prism, lens, optical element, first lens, and screen. Data for surface numbers that do not correspond to the liquid crystal panel, dichroic prism, lens, optical element, first lens, and screen is dummy data. R is the radius of curvature. D is the on-axis surface spacing. C is the aperture radius, and twice the aperture radius is the diameter of the lens surface. R, D, and C are in mm.

[0076] Symbol Surface number Shape RD Glass material Refraction / Reflection C 18 0 Sphere Infinity 9.5000 Refraction 0.0000 19 1 Sphere Infinity 25.9100 SBSL7_OHARA Refraction 12.8706 2 sphere infinity 0.0000 refraction 14.7871 L1 3 sphere 23.3077 7.9094 SFPL51_OHARA Refraction 15.4467 4 sphere -127.0559 0.1000 Refraction 15.2079 L2 5 sphere 21.0056 5.4283 SFPL51_OHARA Refraction 13.0000 L3 6 sphere 44.2633 1.2142 STIH6_OHARA Refraction 11.8639 7 sphere 26.7444 0.1000 refraction 11.0399 L4 8 sphere 17.2046 7.4036 SFPL51_OHARA Refraction 10.5313 L5 9 ball -23.7897 0.7500 TAFD25_HOYA Refractive index 9.6431 10 spheres 20.7471 0.2000 Refraction 8.5696 L6 11 Aspheric 14.2713 4.2460 LBAL35_OHARA Refraction 8.6504 12 Aspheric 32.7925 1.0000 Refractive 7.7784 L7 13 Sphere 16.4731 2.7568 SFSL5_OHARA Refraction 7.6827 14 Sphere 23.3002 2.7433 Refraction 7.2371 51 15 Sphere Infinity 0.1000 Refraction 6.9632 L8 16 Sphere 55.5146 3.5141 STIH53_OHARA Refraction 7.2124 17 Sphere -20.4634 0.1000 Refraction 7.4622 L9 18 Aspheric -18.8417 4.8490 LLAM60_OHARA Refractive 7.4571 19 Aspheric 138.4003 Variable Spacing 1 Refractive 8.3506 L10 20 Sphere 77.9934 3.2176 STIL25_OHARA Refraction 13.5492 L11 21 sphere -238.3916 1.0000 STIH6_OHARA refraction 13.7984 22 Sphere 422.0121 Variable Spacing 2 Refraction 14.0280 L12 23 Sphere 35.5651 10.2093 STIM22_OHARA Refraction 15.5000 24 sphere -34.9646 0.7658 Refraction 15.5950 L13 25 sphere -38.6490 5.7518 STIL25_OHARA refraction 15.1870 L14 26 Sphere -19.2778 1.0000 STIH6_OHARA Refraction 15.1633 27 Sphere 431.4628 Variable Spacing 3 Refraction 16.3418 L15 28 Aspheric -22.5593 3.0000 'Z-E48R' Refractive 16.5057 29 Aspheric 111.9646 Variable Spacing 4 Refractive 18.7911 L16 30 Aspheric 245.8978 8.0000 'Z-E48R' Refraction 24.6934 31 Aspheric 58.0779 Variable Spacing 5 Refractive 26.5408 40 32 Aspheric -28.3812 -46.6942 Reflection 39.1428 34 33 Aspheric 33.3357 -7.0000 'Z-E48R' Refractive 27.0468 34 Aspheric 30.6616 Variable Spacing 6 Refractive 36.2389 S 35 Sphere Infinity 0.0000 Refraction 2001.4151

[0077] Here, the projection optical system 3B of this example can change the projection distance between a reference distance, a short distance shorter than the reference distance, and a long distance longer than the reference distance. When the projection distance is changed, focusing is performed by moving the seven lenses L10 to L16 of the first optical system 31 along the optical axis N. Note that when focusing is performed to change the projection distance from a short distance to a long distance, the lenses L10 and L11 move toward the reduction side along the optical axis N. When focusing is performed in the same way, the lenses L12, L13, and L14 move toward the enlargement side along the optical axis N. When focusing is performed in the same way, the lens L15 moves toward the enlargement side along the optical axis N. When focusing is performed in the same way, the lens L16 moves toward the enlargement side along the optical axis N.

[0078] Variable distance 1, variable distance 2, variable distance 3, variable distance 4, variable distance 5, and variable distance 6 at each projection distance when focusing are shown below. Variable distance 1 is the axial surface distance between lens L9 and lens L10. Variable distance 2 is the axial surface distance between lens L11 and lens L12. Variable distance 3 is the axial surface distance between lens L14 and lens L15. Variable distance 4 is the axial surface distance between lens L15 and lens L16. Variable distance 5 is the axial surface distance between lens L16 and reflecting surface 40. Variable distance 6 is the projection distance.

[0079] Reference distance Near distance Far distance Variable Interval 1 12.1167 13.2136 11.8202 Variable Interval 2 1.8056 0.1000 2.7521 Variable Interval 3 5.1195 5.3664 4.9687 Variable Interval 4 20.8516 21.2210 20.3846 Variable Interval 5 38.8253 38.8412 38.8165 Variable Interval 6 -287.0000 -224.0000 -403.0000

[0080] The aspherical coefficients are as follows:

[0081] Surface number S11 S12 S18 S19 Radius of curvature (R) 14.2713 32.7925 -18.8417 138.4003 Conic constant (K) 8.61373E-01 1.26960E+01 -1 -90 4th -1.78411E-05 1.08502E-04 6.36736E-05 9.09981E-05 6th order 1.92270E-08 3.62039E-07 -9.07712E-07 -7.42228E-07 8th order 8.84500E-11 -2.22710E-09 3.81595E-09 3.02545E-09 10th order 4.90294E-11

[0082] Face number S28 S29 S30 S31 Radius of curvature (R) -22.5593 111.9646 245.8978 58.0779 Conic constant (K) 0 0 90 0.00000E+00 4th 1.20307E-04 1.83761E-05 -5.27611E-05 -8.10795E-05 6th -6.19796E-07 -2.79021E-07 1.51125E-07 2.09269E-07 8th order 1.66495E-09 6.93645E-10 -3.07259E-10 -3.89250E-10 10th order -1.73986E-12 -6.65573E-13 4.39273E-13 4.46405E-13 12th -2.61547E-16 -1.98979E-16 14th order 6.56482E-22

[0083] Face number S32 S33 S34 Radius of curvature (R) -28.3812 33.3357 30.66161366 Conic constant (K) -1.00000E+00 -5.39402E-01 -0.60807081 Quaternary 3.57234E-06 1.50335E-04 4.29399E-05 6th -6.79154E-09 -9.61493E-07 -2.02768E-07 8th order 9.60704E-12 3.12494E-09 3.95931E-10 10th order -7.92734E-15 -5.89295E-12 -4.31475E-13 12th order 3.36716E-18 6.57780E-15 2.74639E-16 14th -6.07598E-22 -4.02279E-18 -9.56386E-20 16th order 1.04005E-21 1.41923E-23

[0084] Here, the projection optical system 3B of this example has an axial surface distance from the liquid crystal panel 18 to the reflecting surface 40 as OAL, a first distance from the optical axis N to the maximum image height of the liquid crystal panel 18 as imy, a maximum radius of the first lens 34 as LL, a throw ratio obtained by dividing the projection distance by a second distance from the optical axis N to the maximum image height of the enlarged image projected on the screen S as TR, and a numerical aperture of the liquid crystal panel 18 as NA, and satisfies all of the following conditional expressions (1) and (2): TR≦0.3 (1) 35≦(OAL / imy)×(LL / imy)×TR×(1 / NA)≦60 (2)

[0085] Even more preferably, the following conditional expressions (1) and (2') are both satisfied. TR≦0.3 (1) 35≦(OAL / imy)×(LL / imy)×TR×(1 / NA)≦53 (2')

[0086] In this example, OAL 189mm imy 11.8mm LL 36.5mm TR 0.197 NA 0.2778 Therefore, TR=0.197, which satisfies conditional expression (1). (OAL / imy)×(LL / imy)×TR×(1 / NA)=35, which satisfies conditional expression (2).

[0087] (Action and effect)

[0088] In the projection optical system 3B of this example, a reflective coating layer (reflective layer) is provided on the surface of the reflective surface 40. Therefore, the projection optical system 3B of this example can obtain the same effects as those of the first embodiment.

[0089] In the projection optical system 3B of this example, the lens L16 (second lens) arranged on the most enlargement side in the first optical system 31 is formed separately from the first lens 34. The lens L16 is arranged between the reflecting surface 40 and the first lens 34 in the direction of the optical axis N. In other words, the lens L16 arranged on the most enlargement side in the first optical system 31 is arranged inside the second optical system 32 in the direction of the optical axis N, so the distance between the lens L16 and the reflecting surface 40 is short. Therefore, the projection optical system 3B of this example can obtain the same effects as those in the first embodiment.

[0090] The first optical system 31 also includes a lens L16 (second lens) and a lens L15 (third lens) located adjacent to the reduction side of the lens L16. The lenses L15 and L16 have aspherical surfaces. The projection optical system 3B of this example focuses by moving the lenses L15 and L16 toward the magnification side along the optical axis N, thereby changing the projection distance from a short distance to a long distance. Therefore, the projection optical system 3B moves the lenses L15 and L16, which correct aberrations for each image height, along the optical axis N, thereby suppressing the occurrence of aberrations during focusing. In a configuration in which focusing is performed by moving a non-aspherical lens along the optical axis N, a separate aspherical lens is required to correct the aberrations. However, in this example, the lenses L15 and L16, which move during focusing, have aspherical surfaces, allowing the entire projection optical system to be compact.

[0091] Furthermore, the first optical system 31 includes a cemented lens L23 and a cemented lens L24 on the enlargement side of the diaphragm 51. Therefore, chromatic aberration can be corrected well.

[0092] Here, the projection optical system 3B of this example satisfies the conditional expressions (1) and (2), and therefore the projection optical system of the first embodiment The same effect as that of the optical system 3A can be obtained. 9 is a diagram showing the spherical aberration and the lateral aberration of the projection optical system 3B at the reference distance. 10 is a diagram showing astigmatism and distortion of the projection optical system 3B at a short distance. 11 is a diagram showing spherical aberration, astigmatism, and distortion. 8 to 11 are diagrams showing spherical aberration, astigmatism, and distortion in relation to distance. As shown in the figure, the projection optical system 3 of this example B In this case, various aberrations in the magnified image are suppressed.

[0093] Example 3 12 is a ray diagram of a projection optical system 3C of Example 3. As shown in Fig. 12, the projection optical system 3C of this example is made up of, in order from the reduction side to the enlargement side, a first optical system 31 and a second optical system 32. The second optical system 32 is disposed on the optical axis N of the first optical system 31.

[0094] The first optical system 31 is a refractive optical system. The first optical system 31 is made up of thirteen lenses L1 to L13. The lenses L1 to L13 are arranged in this order from the reduction side to the enlargement side. A diaphragm 51 is arranged between the lenses L6 and L7.

[0095] Lens L5 has aspherical surfaces on both sides. Lens L8 has aspherical surfaces on both sides. Lens L12 (third lens) has aspherical surfaces on both sides. Lens L13 (second lens) has aspherical surfaces on both sides. Lenses L3 and L4 are cemented together to form cemented lens L21. Lenses L10 and L11 are cemented together to form cemented lens L22.

[0096] The second optical system 32 includes an optical element 33 and a first lens 34. The optical element 33 and the first lens 34 are arranged in this order from the reduction side to the enlargement side. The optical element 33 includes a reflective surface 40 facing the reduction side. The reflective surface 40 has a concave shape recessed in the second direction Z2. The reflective surface 40 has an aspherical shape. As shown in FIG. 12, the reflective surface 40 is located below the optical axis N at Y2. The reflective surface 40 is formed by providing a reflective coating layer (reflective layer) on the outer surface of the optical element 33 in the first direction Z1. The reflective surface 40 reflects light on the surface of the optical element 33 in the Z1 direction.

[0097] The first lens 34 is positioned in the first direction Z1 from the optical element 33 and is disposed above the optical axis N at a position Y1. The first lens 34 has negative power. The first lens 34 has a convex shape on the magnification side and a concave shape on the reduction side. The first lens 34 has aspherical shapes on both sides.

[0098] Here, the liquid crystal panel 18 of the image forming unit 2 is disposed on a reduction-side conjugate plane of the projection optical system 3C. The screen S is disposed on an enlargement-side conjugate plane of the projection optical system 3C.

[0099] The liquid crystal panel 18 forms a projected image in an image forming plane perpendicular to the optical axis N of the first optical system 31. The liquid crystal panel 18 is disposed at a position offset upward Y1 with respect to the optical axis N of the first optical system 31. Therefore, the projected image is formed at a position offset upward Y1 with respect to the optical axis N.

[0100] Light rays from the liquid crystal panel 18 pass through the first optical system 31 and the second optical system 32 in this order. Between the first optical system 31 and the second optical system 32, the light rays pass below Y2 on the optical axis N. As a result, the light rays pass through the second optical system 32 toward the reflective surface 40. The light rays that reach the reflective surface 40 are reflected in the first direction Z1 and upward Y1. The light rays that are reflected by the reflective surface 40 cross the optical axis N upward Y1 toward the first lens 34. The light rays that pass through the first lens 34 are expanded by the first lens 34 and reach the screen S.

[0101] Here, the lens L13 of the first optical system 31 is disposed between the reflecting surface 40 and the first lens 34 in the direction of the optical axis N. The intermediate image 30 is formed between the lens L13 and the reflecting surface 40.

[0102] In the projection optical system 3C, the reduction side from the first optical system 31 is telecentric.

[0103] Here, the projection distance of the projection optical system 3C can be changed. When the projection distance is changed, focusing is performed by moving the four lenses L9 to L12 of the first optical system 31 along the optical axis N. During focusing, the lenses L10 and L11 are moved together.

[0104] The numerical aperture of the liquid crystal panel 18 is NA, the first distance from the optical axis N to the maximum image height of the liquid crystal panel 18 is imy, the second distance from the optical axis N to the maximum image height of the enlarged image projected onto the screen S is scy, the projection distance which is the distance from the first lens 34 to the screen S is PD, the projection magnification obtained by dividing the second distance by the first distance is M, the throw ratio obtained by dividing the projection distance by the second distance is TR, the axial surface distance from the liquid crystal panel 18 to the reflective surface 40 is OAL, and the maximum radius of the first lens 34 is LL. The data of the projection optical system 3C is as follows:

[0105] NA 0.2084 imy 11.7mm scy 1462mm PD 378.0mm M 125 TR 0.259 OAL 172mm LL 37.8mm

[0106] The lens data for the projection optical system 3C is as follows. Surface numbers are assigned in order from the reduction side to the enlargement side. The symbols refer to the LCD panel, dichroic prism, lens, optical element, first lens, and screen. Data for surface numbers that do not correspond to the LCD panel, dichroic prism, lens, optical element, first lens, and screen is dummy data. R is the radius of curvature. D is the on-axis surface spacing. C is the aperture radius, and twice the aperture radius is the diameter of the lens surface. R, D, and C are in mm.

[0107] Symbol Surface number Shape RD Glass material Refraction / Reflection C 18 0 Sphere Infinity 5.1000 Refraction 0.0000 19 1 Sphere Infinity 23.9250 SBSL7_OHARA Refraction 12.0558 2 Sphere Infinity 0.0000 Refraction 13.1538 L1 3 sphere 25.3616 5.2165 SFPL51_OHARA Refraction 13.4219 4 sphere -160.4483 0.1000 Refraction 13.2933 L2 5 sphere 20.5113 4.3359 SFSL5_OHARA Refraction 12.0000 6 sphere 132.0437 0.0000 Refraction 11.5962 7 Sphere Infinity 0.1000 Refraction 11.9120 L3 8 sphere 20.3053 7.3344 SBSL7_OHARA Refraction 10.1626 L4 9 sphere -23.1488 0.6000 TAFD25_HOYA Refraction 8.3549 10 sphere 13.5441 0.2000 refraction 7.2414 L5 11 Aspheric 10.7115 2.4947 LBAL35_OHARA Refractive 7.2839 12 Aspheric 21.0609 8.3786 Refractive 6.9453 L6 13 Sphere 34.9176 3.6553 SFSL5_OHARA Refraction 6.3040 14 sphere -16.1488 0.0364 refraction 6.0810 51 15 Sphere Infinity 0.1000 Refraction 5.5409 L7 16 sphere -371.7544 2.2081 STIH53_OHARA Refraction 5.5362 17 Sphere -27.0329 0.1512 Refraction 5.4751 L8 18 Aspheric -23.1991 2.3150 LLAM60_OHARA Refractive 5.4355 19 Aspheric 89.7692 Variable Spacing 1 Refractive 5.5698 L9 20 sphere -64.9866 5.7941 STIM22_OHARA refraction 15.7747 21 Sphere -27.0076 Variable Spacing 2 Refraction 16.5319 L10 22 Sphere 43.6185 10.6351 STIL25_OHARA Refraction 17.8154 L11 23 Sphere -30.6037 1.0000 STIH6_OHARA Refraction 17.7153 24 sphere 66.9444 variable spacing 3 refraction 17.8736 L12 25 Aspheric -49.3948 6.5927 'Z-E48R' Refractive 19.0969 26 Aspheric 33.1964 Variable Spacing 4 Refractive 18.5842 L13 27 Aspheric 198.8399 5.0000 'Z-E48R' Refractive 18.7753 28 Aspheric 41.3371 35.9841 Refractive 19.8477 40 29 Aspheric -28.5883 -41.4150 Reflection 29.2645 34 30 Aspheric 38.8043 -5.0000 'Z-E48R' Refractive 27.5293 31 Aspheric 39.6045 Variable Spacing 5 Refractive 36.7982 S 32 Sphere Infinity 0.0000 Refraction 1983.0341

[0108] Here, the projection optical system 3C of this example can change the projection distance between a reference distance, a short distance shorter than the reference distance, and a long distance longer than the reference distance. When the projection distance is changed, focusing is performed by moving the four lenses L9 to L12 of the first optical system 31 along the optical axis N. When focusing is performed to change the projection distance from a short distance to a long distance, the lens L9 moves toward the enlargement side along the optical axis N. When focusing is performed in the same way, the lenses L10 and L11 move toward the enlargement side along the optical axis N. When focusing is performed in the same way, the lens L12 moves toward the enlargement side along the optical axis N. In the projection optical system 3C of this example, the lens L13 is fixed.

[0109] Variable distance 1, variable distance 2, variable distance 3, variable distance 4, and variable distance 5 at each projection distance when focusing are shown below. Variable distance 1 is the axial surface distance between lens L8 and lens L9. Variable distance 2 is the axial surface distance between lens L9 and lens L10. Variable distance 3 is the axial surface distance between lens L11 and lens L12. Variable distance 4 is the axial surface distance between lens L12 and lens L13. Variable distance 5 is the projection distance.

[0110] Reference distance Near distance Far distance Variable Interval 1 27.7058 27.3443 27.9475 Variable Interval 2 0.2085 0.0000 0.4035 Variable Interval 3 5.0259 5.2821 4.8227 Variable Interval 4 8.2762 8.5655 8.0181 Variable Interval 5 -379.0000 -297.0000 -524.0000

[0111] The aspherical coefficients are as follows:

[0112] Surface number S11 S12 S18 S19 Radius of curvature (R) 10.7115 21.0609 -23.1991 89.7692 Conic constant (K) 2.69624E-01 4.78408E+00 -1 -90 4th -7.67687E-05 5.05163E-05 1.47441E-04 2.11126E-04 6th -5.77986E-07 -3.02482E-07 -2.37490E-06 -2.24828E-06 8th -4.01080E-09 -4.23268E-09 1.45245E-08 1.46576E-08 10th order 5.29887E-11

[0113] Face number S25 S26 S27 S28 Curvature radius (R) -49.3948 33.1964 198.8399 41.3371 コーニックfixed number (K) 0 0 90 0.00000E+00 4 times 6.80021E-05 -4.70087E-05 -6.65376E-05 -1.21300E-04 6 times -9.65755E-08 1.44566E-07 -7.25627E-09 4.65229E-07 8 times 7.76122E-11 -3.72543E-10 6.19846E-10 -1.09606E-09 10 times 2.18093E-14 4.76925E-13 -1.08500E-12 1.26985E-12 12 times 3.76822E-16 2.28175E-16 14 times -1.41383E-18

[0114] Face number S29 S30 S31 Curvature radius (R) -28.5883 38.8043 39.60445722 コーニックfixed number (K) -1.00000E+00 4.72790E-01 -0.611371609 4 times 3.91548E-06 -1.70359E-05 -2.40495E-05 6 times -1.20322E-08 8.73558E-08 5.12452E-08 8 times 2.02386E-11 -2.61450E-10 -6.11798E-11 10 times -2.19615E-14 5.37788E-13 4.72800E-14 12 times 1.28670E-17 -6.50975E-16 -2.21909E-17 14 times -3.20304E-21 4.05800E-19 5.45183E-21 16 times -9.14385E-23 -3.94213E-25

[0115] Here, the projection optical system 3C of this example has an axial surface distance from the liquid crystal panel 18 to the reflecting surface 40 as OAL, a first distance from the optical axis N to the maximum image height of the liquid crystal panel 18 as imy, a maximum radius of the first lens 34 as LL, a throw ratio obtained by dividing the projection distance by a second distance from the optical axis N to the maximum image height of the enlarged image projected on the screen S as TR, and a numerical aperture of the liquid crystal panel 18 as NA, and satisfies all of the following conditional expressions (1) and (2): TR≦0.3 (1) 35≦(OAL / imy)×(LL / imy)×TR×(1 / NA)≦60 (2)

[0116] In this example, OAL 172mm imy 11.7mm LL 37.8mm TR 0.259 NA 0.2084 Therefore, TR=0.259, which satisfies conditional expression (1). (OAL / imy)×(LL / imy)×TR×(1 / NA)=59, which satisfies conditional expression (2).

[0117] (Action and effect)

[0118] In the projection optical system 3C of this example, a reflective coating layer (reflective layer) is provided on the surface of the reflective surface 40. Therefore, the projection optical system 3C of this example can obtain the same effects as those of the first embodiment.

[0119] In the projection optical system 3C of this example, the lens L13 (second lens) arranged on the most enlargement side in the first optical system 31 is formed separately from the first lens 34. The lens L13 is arranged between the reflecting surface 40 and the first lens 34 in the direction of the optical axis N. In other words, the lens L13 arranged on the most enlargement side in the first optical system 31 is arranged inside the second optical system 32 in the direction of the optical axis N, so the distance between the lens L13 and the reflecting surface 40 is short. Therefore, the projection optical system 3C of this example can obtain the same effects as those of the first embodiment.

[0120] In the projection optical system 3C of this example, the first optical system 31 includes a lens L13 (second lens) and a lens L12 (third lens) located adjacent to the reduction side of the lens L13. The lenses L12 and L13 have aspherical shapes. The projection optical system 3C of this example focuses by moving the lens L12 toward the enlargement side along the optical axis N to change the projection distance from a short distance to a long distance. Therefore, the projection optical system 3C moves the lens L12, which corrects various aberrations for each image height, along the optical axis N, thereby suppressing the occurrence of various aberrations during focusing. Furthermore, in a configuration in which focusing is performed by moving a non-aspherical lens along the optical axis N, a separate aspherical lens is required to correct various aberrations. However, in this example, the lens L12, which moves during focusing, has an aspherical shape, allowing the entire projection optical system to be made smaller.

[0121] Furthermore, lens L13 is fixed in the direction of optical axis N. Here, lens L13, which is the second lens, is disposed between reflecting surface 40 and first lens 34. Therefore, when focusing is performed by moving lens L13 in the direction of optical axis N, the mechanism for moving lens L13 becomes complicated, which increases manufacturing costs. Therefore, compared to projection optical system 3A of Example 1 in which lens L17, which is the second lens, moves in the direction of optical axis N, projection optical system 3C of this example can reduce manufacturing costs.

[0122] Furthermore, the first optical system 31 includes a cemented lens L22 on the enlargement side of the diaphragm 51. Therefore, chromatic aberration can be corrected well.

[0123] Here, the projection optical system 3C of this example satisfies the conditional expressions (1) and (2), and therefore the projection optical system of the first embodiment The same effects as those of the optical system 3A can be obtained. 14 is a diagram showing the lateral aberration at the reference distance of the projection optical system 3C. 15 is a diagram showing the aberration, astigmatism, and distortion of the projection optical system 3C at a short distance. 16 is a diagram showing spherical aberration, astigmatism, and distortion in the projection optical system 3C. 13 to 14 are diagrams showing spherical aberration, astigmatism, and distortion at a long distance. As shown in FIG. 6, the projection optical system 3 C In this case, various aberrations in the magnified image are suppressed.

[0124] Example 4 17 is a ray diagram of the projection optical system 3D of Example 4. As shown in Fig. 17, the projection optical system 3D of this example is made up of, in order from the reduction side to the enlargement side, a first optical system 31 and a second optical system 32. The second optical system 32 is disposed on the optical axis N of the first optical system 31.

[0125] The first optical system 31 is a refractive optical system. The first optical system 31 is made up of thirteen lenses L1 to L13. The lenses L1 to L13 are arranged in this order from the reduction side to the enlargement side. A diaphragm 51 is arranged between the lenses L6 and L7.

[0126] Lens L5 has aspherical surfaces on both sides. Lens L8 has aspherical surfaces on both sides. Lens L12 (third lens) has aspherical surfaces on both sides. Lens L13 (second lens) has aspherical surfaces on both sides. Lenses L3 and L4 are cemented together to form cemented lens L21. Lenses L10 and L11 are cemented together to form cemented lens L22.

[0127] The second optical system 32 includes an optical element 33 and a first lens 34. The optical element 33 and the first lens 34 are arranged in this order from the reduction side to the magnification side. The optical element 33 includes a first surface 36 facing the reduction side and a second surface 37 facing the opposite side from the first surface 36. The optical element 33 also includes a reflective coating layer on the second surface 37. The first surface 36 has a concave shape. The second surface 37 has a convex shape. Here, the optical element 33 includes, in order from the reduction side to the magnification side, a first transmitting surface 41, a reflecting surface 42, and a second transmitting surface 43. The first transmitting surface 41 is provided on the first surface 36. The first transmitting surface 41 has a concave shape. The reflecting surface 42 is a reflective coating layer and has a concave shape to which the surface shape of the second surface 37 is transferred. The reflecting surface 42 reflects light within the optical element 33. The second transmitting surface 43 is provided on the first surface 36. The second transmitting surface 43 has a concave shape. The first transmitting surface 41, the reflecting surface 42, and the second transmitting surface 43 have aspheric shapes. As shown in FIG. 17 , the first transmitting surface 41, the reflecting surface 42, and the second transmitting surface 43 are located below the optical axis N at a position Y2.

[0128] The first lens 34 is positioned in the first direction Z1 from the optical element 33 and is disposed above the optical axis N at a position Y1. The first lens 34 has negative power. The first lens 34 has a convex shape on the magnification side and a concave shape on the reduction side. The first lens 34 has aspherical shapes on both sides.

[0129] Here, the liquid crystal panel 18 of the image forming unit 2 is disposed on a reduction-side conjugate plane of the projection optical system 3D. The screen S is disposed on an enlargement-side conjugate plane of the projection optical system 3D.

[0130] The liquid crystal panel 18 forms a projected image in an image forming plane perpendicular to the optical axis N of the first optical system 31. The liquid crystal panel 18 is disposed at a position offset upward Y1 with respect to the optical axis N of the first optical system 31. Therefore, the projected image is formed at a position offset upward Y1 with respect to the optical axis N.

[0131] The liquid crystal panel 18 forms a projected image in an image forming plane perpendicular to the optical axis N of the first optical system 31. The liquid crystal panel 18 is disposed at a position offset upward Y1 with respect to the optical axis N of the first optical system 31. Therefore, the projected image is formed at a position offset upward Y1 with respect to the optical axis N.

[0132] A light ray from the liquid crystal panel 18 passes through the first optical system 31 and the second optical system 32 in this order. Between the first optical system 31 and the second optical system 32, the light ray passes below Y2 on the optical axis N. As a result, the light ray is incident on the first transmitting surface 41 of the optical element 33 that constitutes the second optical system 32.

[0133] A light ray that enters the optical element 33 through the first transmitting surface 41 travels toward the reflecting surface 42. The light ray that reaches the reflecting surface 42 is bent back toward the first direction Z1 and upward Y1. The light ray that is bent back by the reflecting surface 42 travels toward the second transmitting surface 43. The light ray that exits the second transmitting surface 43 crosses the optical axis N upward Y1 and travels toward the first lens 34. The light ray that passes through the first lens 34 is expanded by the first lens 34 and reaches the screen S.

[0134] Here, the lens L13 of the first optical system 31 has a reflecting surface 4 2 and the first The intermediate image 30 is formed between the lens L13 and the reflecting surface 4. 2 Between It is done.

[0135] In the projection optical system 3D, the reduction side from the first optical system 31 is telecentric.

[0136] Here, the projection optical system 3D can change the projection distance. When the projection distance is changed, the four lenses L9 to L12 of the first optical system 31 are moved along the optical axis N to perform focusing.

[0137] The numerical aperture of the liquid crystal panel 18 is NA, and the first distance from the optical axis N to the maximum image height of the liquid crystal panel 18 is The distance is imy, and the second distance is the maximum image height of the enlarged image projected on the screen S from the optical axis N. The distance from the first lens 34 to the screen S is defined as scy, and the projection distance from the first lens 34 to the screen S is defined as PD. The projection magnification obtained by dividing the second distance by the first distance is M, and the throw distance obtained by dividing the projection distance by the second distance is Let the value be TR, and the value from the LCD panel 18 to the reflective surface 4 2 The on-axis distance from the first lens to the second lens is called the OAL. The maximum radius of the lens 34 is LL, and the data of the projection optical system 3D is as follows:

[0138] NA 0.25 imy 11.7mm scy 1463mm PD 376.0mm M 125 TR 0.257 OAL 175mm LL 40.0mm

[0139] The lens data for the 3D projection optical system is as follows. Surface numbers are assigned in order from the reduction side to the enlargement side. The symbols refer to the LCD panel, dichroic prism, lens, optical element, first lens, and screen. Data for surface numbers that do not correspond to the LCD panel, dichroic prism, lens, optical element, first lens, and screen is dummy data. R is the radius of curvature. D is the on-axis surface spacing. C is the aperture radius, and twice the aperture radius is the diameter of the lens surface. R, D, and C are in mm.

[0140] Symbol Surface number Shape RD Glass material Refraction / Reflection C 18 0 Sphere Infinity 5.1000 Refraction 0.0000 19 1 Sphere Infinity 23.9250 SBSL7_OHARA Refraction 12.2082 2 Sphere Infinity 0.0000 Refraction 13.7743 L1 3 sphere 20.7308 7.6535 SFPL51_OHARA Refraction 14.3491 4 sphere -160.5725 0.1403 Refraction 14.0489 L2 5 sphere 19.8009 3.4530 SFSL5_OHARA Refraction 12.0000 6 sphere 42.1883 0.0000 Refraction 11.4760 7 Sphere Infinity 0.1846 Refraction 12.5433 L3 8 sphere 26.7793 5.8661 SBSL7_OHARA Refraction 10.8722 L4 9 sphere -23.4816 0.7000 TAFD25_HOYA Refraction 10.1298 10 spheres 23.8348 0.2000 refraction 8.9729 L5 11 Aspheric 14.1866 3.5452 LBAL35_OHARA Refractive 8.8797 12 Aspheric 23.2921 8.5134 Refractive 8.1796 L6 13 Sphere 33.2276 4.4787 SFSL5_OHARA Refraction 7.8479 14 sphere -16.5041 0.0000 refraction 7.6677 51 15 Sphere Infinity 0.1000 Refraction 6.6414 L7 16 sphere 846.5448 2.2054 STIH53_OHARA refraction 6.6229 17 Sphere -40.4470 0.2313 Refraction 6.4863 L8 18 Aspheric -25.5044 3.6042 LLAM60_OHARA Refractive 6.4792 19 Aspheric 59.3482 Variable Spacing 1 Refractive 6.1272 L9 20 sphere -437.3885 6.0000 STIM22_OHARA refraction 17.0050 21 Sphere -37.6532 Variable Spacing 2 Refraction 17.5773 L10 22 Sphere 31.8187 11.5532 STIL25_OHARA Refraction 19.3821 L11 23 sphere -47.9275 1.3832 STIH6_OHARA refraction 19.2050 24 Sphere 49.3856 Variable Spacing 3 Refraction 18.3019 L12 25 Aspheric -177.2317 2.0000 'Z-E48R' Refractive 18.4483 26 Aspheric 22.7112 Variable Spacing 4 Refractive 17.9293 L13 27 Aspheric 179.6432 5.0000 'Z-E48R' Refractive 19.9221 28 Aspheric 27.1594 35.4677 Refractive 19.7715 41 29 Aspheric -32.3930 3.0000 'Z-E48R' Refractive 30.0301 42 30 Aspheric -30.4878 -3.0000 'Z-E48R' Reflection 30.7470 43 31 Aspheric -32.3930 -41.1512 Refractive 29.6535 34 32 Aspheric 39.4467 -5.0000 'Z-E48R' Refractive 35.7473 33 Aspheric 38.8749 Variable Spacing 5 Refractive 39.9951 S 34 Sphere Infinity 0.0000 Refraction 1984.0193

[0141] Here, the projection optical system 3D of this example can change the projection distance between a reference distance, a short distance shorter than the reference distance, and a long distance longer than the reference distance. When the projection distance is changed, focusing is performed by moving the four lenses L9 to L12 of the first optical system 31 along the optical axis N. When focusing is performed so that the projection distance changes from a short distance to a long distance, the lens L9 moves toward the reduction side along the optical axis N. When focusing is performed in the same way, the lenses L10 and L11 move toward the enlargement side along the optical axis N. When focusing is performed in the same way, the lens L12 moves toward the enlargement side along the optical axis N. In the projection optical system 3D of this example, the lens L13 is fixed.

[0142] Variable distance 1, variable distance 2, variable distance 3, variable distance 4, and variable distance 5 at each projection distance when focusing are shown below. Variable distance 1 is the axial surface distance between lens L8 and lens L9. Variable distance 2 is the axial surface distance between lens L9 and lens L10. Variable distance 3 is the axial surface distance between lens L11 and lens L12. Variable distance 4 is the axial surface distance between lens L12 and lens L13. Variable distance 5 is the projection distance.

[0143] Reference distance Near distance Far distance Variable Interval 1 26.8792 27.0101 26.6608 Variable Interval 2 1.4097 0.7506 2.2492 Variable Interval 3 2.1500 2.6303 1.5624 Variable Interval 4 10.4814 10.5279 10.4465 Variable Interval 5 -376.0000 -295.0000 -519.0000

[0144] The aspherical coefficients are as follows:

[0145] Surface number S11 S12 S18 S19 Radius of curvature (R) 14.1866 23.2921 -25.5044 59.3482 Conic constant (K) 0.52162588 4.313809097 -1 -90 4th -2.90353E-05 1.01864E-04 9.38265E-05 1.86743E-04 6th -2.33563E-07 -3.97479E-08 -1.24711E-06 -1.68413E-06 8th order -7.08031E-09 -1.14146E-08 5.72359E-09 9.15280E-09 10th order 2.69207E-11

[0146] Face number S25 S26 S27 S28 Radius of curvature (R) -177.2317 22.7112 179.6432 27.1594 コーニックfixed number (K) 0 0 89.447202 0.000000 4 times 7.96862E-05 -2.58626E-08 -6.20694E-05 -1.51197E-04 6 times -3.07379E-07 -1.92895E-07 4.44832E-07 9.77046E-07 8 times 6.58543E-10 2.75182E-10 -2.36330E-09 -4.47460E-09 10 times -4.83689E-13 -1.73130E-15 5.49541E-12 1.16337E-11 12 times -4.88375E-15 -1.62518E-14 14 times 9.38335E-18

[0147] Face number S29,S31 S30 S32 S33 Curvature radius (R) -32.3930 -30.4878 39.4467 38.8749 コーニックfixed number (K) -1.026766 -1.000000 -0.081546 -0.618360 4 times 9.61441E-06 5.12974E-06 -1.83922E-05 -1.83960E-05 6 times -4.77776E-08 -1.81978E-08 8.40433E-08 3.72462E-08 8 times 1.03751E-10 2.96797E-11 -1.91747E-10 -5.13686E-11 10 times -1.17673E-13 -2.63402E-14 2.17884E-13 5.06109E-14 12 times 6.81981E-17 1.12362E-17 -5.07382E-17 -3.06209E-17 14 times -1.55320E-20 -1.48819E-21 -7.93912E-20 1.04462E-20 16th order 4.02973E-23 -1.62167E-24

[0148] Here, the projection optical system 3D of this example has a structure in which light is projected from the liquid crystal panel 18 to the reflecting surface 4 2 The axial spacing up to OAL, a first distance from the optical axis N to the maximum image height of the liquid crystal panel 18 is imy, and the first level The maximum radius of the lens 34 is LL, and the projection distance is the distance from the optical axis N to the screen S. The throw ratio divided by the second distance to the maximum image height is TR, and the numerical aperture of the liquid crystal panel 18 is N A satisfies the following conditional expressions (1) and (2). TR≦0.3 (1) 35≦(OAL / imy)×(LL / imy)×TR×(1 / NA)≦60 (2)

[0149] Even more preferably, the following conditional expressions (1) and (2') are both satisfied. TR≦0.3 (1) 35≦(OAL / imy)×(LL / imy)×TR×(1 / NA)≦53 (2')

[0150] In this example, OAL 175mm imy 11.7mm LL 40.0mm TR 0.257 NA 0.25 Therefore, TR=0.257, which satisfies conditional expression (1). (OAL / imy)×(LL / imy)×TR×(1 / NA)=53, which satisfies conditional expression (2).

[0151] (Action and effect)

[0152] In the projection optical system 3D of this example, the lens arranged on the most enlarged side in the first optical system 31 The lens L13 (second lens) is formed separately from the first lens 34. , in the direction of the optical axis N, the reflecting surface 4 2 and the first lens 34. The lens L13 arranged on the most enlarged side in the first optical system 31 is Since the lens L13 is disposed inside the second optical system 32, the distance between the lens L13 and the reflecting surface 40 is short. Therefore, the projection optical system 3D of this example can obtain the same effects as those of the first embodiment.

[0153] In the projection optical system 3D of this example, the first optical system 31 includes a lens L13 (second lens) and a lens L12 (third lens) disposed adjacent to the reduction side of the lens L13. The lenses L12 and L13 have aspherical shapes. The projection optical system 3D of this example focuses by moving the lens L12 toward the enlargement side along the optical axis N to change the projection distance from a short distance to a long distance. Therefore, the projection optical system 3D moves the lens L12, which corrects various aberrations for each image height, along the optical axis N, thereby suppressing the occurrence of various aberrations during focusing. Furthermore, in a configuration in which focusing is performed by moving a non-aspherical lens along the optical axis N, a separate aspherical lens is required to correct various aberrations. However, in this example, the lens L12, which moves during focusing, has an aspherical shape, allowing the entire projection optical system to be made smaller.

[0154] The lens L13 is fixed in the direction of the optical axis N. The lens L13 has four reflecting surfaces. 2 and the first lens 34, so that the lens L When focusing is performed by moving lens L13 in the direction of optical axis N, lens L13 is moved. Therefore, the second lens element, lens L17, is Compared to the projection optical system 3A of the first embodiment, which moves in the direction of the optical axis N, the projection optical system 3D of this embodiment This can reduce manufacturing costs.

[0155] Furthermore, the first optical system 31 includes a cemented lens L22 on the enlargement side of the diaphragm 51. Therefore, chromatic aberration can be corrected well.

[0156] Here, the projection optical system 3D of this example satisfies the conditional expressions (1) and (2), and therefore the projection optical system of Example 1 The same effects as those of the optical system 3A can be obtained. 19 is a diagram showing the lateral aberration at the reference distance of the projection optical system 3D. 20 is a diagram showing the aberration, astigmatism, and distortion of the projection optical system 3D at a short distance. 21 is a diagram showing spherical aberration, astigmatism, and distortion in a 3D projection optical system. 18 to 2 are diagrams showing spherical aberration, astigmatism, and distortion at a long distance. As shown in FIG. 1, the projection optical system 3 D In this case, various aberrations in the magnified image are suppressed. [Explanation of symbols]

[0157] 1...projector, 2...image forming unit, 3, 3A, 3B, 3C, 3D...projection 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, 1 9...cross dichroic prism, 21...dichroic 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...optical element, 34...first lens, 36...first surface, 37...second surface, 40...reflecting surface, 41...first transmitting surface, 42...reflecting surface, 43...second transmitting surface, 51...aperture, L1 to L17...lenses, L21 to L24...cemented lenses, N...optical axis, S...screen.

Claims

1. The image formed by the image forming element arranged on the reduction side conjugate plane is enlarged and projected onto the enlargement side conjugate plane. In a projection optical system for projecting a magnified image, The optical system includes, in order from the reduction side to the enlargement side, a first optical system and a second optical system, the first optical system includes a diaphragm; The second optical system includes optical elements having concave reflecting surfaces arranged in order from the reduction side to the enlargement side. a first lens having a negative power, The reduction-side conjugate surface and the enlargement-side conjugate surface are disposed between the first optical system and the second optical system. An intermediate image conjugate to The reduction side of the first optical system is telecentric, The axial distance from the image forming element to the reflecting surface is defined as OAL, and the distance from the optical axis to the image forming element is defined as OAL. a first distance to a maximum image height of the component element is defined as imy, a maximum radius of the first lens is defined as LL, The throw ratio obtained by dividing the projection distance by a second distance from the optical axis to the maximum image height of the enlarged image is T When R is the numerical aperture of the image forming element and NA is the numerical aperture of the image forming element, the following conditional expressions (1) and (2) are satisfied: All fulfilled, TR≦0.3 (1) 35≦(OAL / imy)×(LL / imy)×TR×(1 / NA)≦60 (2) The second lens arranged on the most enlarged side in the first optical system is separate from the first lens. formed in the body, The second lens is disposed between the reflecting surface and the first lens in the optical axis direction. A projection optical system characterized by:

2. The projection optical system according to claim 1 , wherein the reflecting surface has a reflecting layer on its surface.

3. The first optical system includes the second lens and a third lens arranged adjacent to the reduction side of the second lens. a lens; the second lens and the third lens have aspherical shapes; By moving the third lens toward the enlargement side in the optical axis direction, the projection distance becomes 3. The method according to claim 1, wherein focusing is performed from a short distance to a long distance. The projection optical system according to claim 1.

4. 4. The optical system according to claim 3, wherein the second lens is fixed in the optical axis direction. The projection optical system described herein.

5. 4. The first optical system includes a cemented lens on the enlargement side of the aperture stop.

5. The projection optical system according to any one of 1 to 4.

6. A projected image formed by an image forming element arranged on a reduction side conjugate plane is enlarged and projected onto an enlargement side conjugate plane. In a projection optical system for projecting a magnified image, The optical system includes, in order from the reduction side to the enlargement side, a first optical system and a second optical system, the first optical system includes a diaphragm; The second optical system includes optical elements having concave reflecting surfaces arranged in order from the reduction side to the enlargement side. a first lens having a negative power, The reduction-side conjugate surface and the enlargement-side conjugate surface are disposed between the first optical system and the second optical system. An intermediate image conjugate to The reduction side of the first optical system is telecentric, The axial distance from the image forming element to the reflecting surface is defined as OAL, and the distance from the optical axis to the image forming element is defined as OAL. a first distance to a maximum image height of the component element is defined as imy, a maximum radius of the first lens is defined as LL, The throw ratio obtained by dividing the projection distance by a second distance from the optical axis to the maximum image height of the enlarged image is T When R is the numerical aperture of the image forming element and NA is the numerical aperture of the image forming element, the following conditional expressions (1) and (2) are satisfied: All fulfilled, TR≦0.3 (1) 35≦(OAL / imy)×(LL / imy)×TR×(1 / NA)≦60 (2) the first optical system includes a cemented lens on the enlargement side of the diaphragm, Academic.

7. A projection optical system according to any one of claims 1 to 6; the image forming element that forms a projected image on the reduction-side conjugate plane of the projection optical system; A projector comprising:

Images