Imaging optical system, projection display device, and image capturing device

Abstract

To provide an imaging optical system having an optical window capable of preventing intrusion of dust and the like, and to provide a projection display device having such an imaging optical system, and an image capturing device having such an imaging optical system.SOLUTION: An imaging optical system capable of forming a magnified image of an image formed on a reduction-side imaging plane onto a magnification-side imaging plane is provided, the imaging optical system comprising an optical window, a reflective optical system, and a refractive optical system comprising multiple lenses, arranged in order from the magnification side to the reduction side along an optical path, and being configured to form at least two intermediate images. The reflective optical system comprises, in order from the magnification side to the reduction side along the optical path, a first reflective surface having positive power, a second reflective surface having power, and a third reflective surface having positive power. The center of the magnified image is offset from an optical axis of the refractive optical system in a direction perpendicular to the optical axis. The imaging optical system satisfies predefined conditional expressions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology of the present disclosure relates to an imaging optical system, a projection display device, and an imaging device. [Background technology]

[0002] The following Patent Documents 1 and 2 describe imaging optical systems that can be used in projection display devices, imaging devices, and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-024359 [Patent Document 2] Japanese Patent Publication No. 2020-086174 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a compact imaging optical system that includes an optical window that can prevent the intrusion of dust and the like, a projection display device that includes this imaging optical system, and an imaging device that includes this imaging optical system. [Means for solving the problem]

[0005] A first aspect of the present disclosure is an imaging optical system capable of forming an enlarged image on an enlargement-side image forming surface by enlarging an image on a reduction-side image forming surface, the imaging optical system comprising, in order along an optical path from the enlargement side to the reduction side, an optical window, a reflective optical system, and a refractive optical system including a plurality of lenses, the reflective optical system including, in order along the optical path from the enlargement side to the reduction side, a first reflecting surface having positive power, a second reflecting surface having power, and a third reflecting surface having positive power, a first intermediate image is formed on the optical path on the reduction side from the third reflecting surface and at a position conjugate with the image, a second intermediate image is formed within the reflective optical system and at a position conjugate with the first intermediate image, a magnified image is formed on the optical path on the enlargement side from the optical window and at a position conjugate with the second intermediate image, the center of the magnified image is at a position shifted in a direction perpendicular to the optical axis of the refractive optical system, 40°<|α|<85° (1) 0°<|θc|<35° (2) Here, the chief ray that is incident on the center of the magnified image when the amount of shift is at its maximum is defined as the central chief ray, the angle of incidence of the central chief ray on the magnification-side image-forming surface is defined as α, and the angle of incidence of the central chief ray on the optical window is defined as θc.

[0006] A second aspect of the present disclosure is an imaging optical system according to the first aspect, in which, when the maximum half angle of view on the enlargement side is ω, 65°<ω<90° (3) Conditional expression (3) expressed as follows is satisfied.

[0007] A third aspect of the present disclosure is an imaging optical system according to the first aspect, wherein the intersection of the central chief ray and the enlargement-side surface of the optical window is located closer to the third reflecting surface than the entire second reflecting surface in the direction of the optical axis.

[0008] A fourth aspect of the present disclosure is an imaging optical system according to the first aspect, wherein the entire optical window is located closer to the third reflecting surface than the point of the refractive optical system that is located on the most magnifying side in the direction of the optical axis.

[0009] A fifth aspect of the present disclosure is an imaging optical system according to the first aspect, in which, when the distance between the optical axis and a point on the optical window closest to the optical axis is hWmin and the radius of the lens on the most enlargement side of the refractive optical system is ra, 0.9 <hWmin / ra<3 (4) Conditional expression (4) expressed as follows is satisfied.

[0010] A sixth aspect of the present disclosure is an imaging optical system according to the first aspect, wherein the optical window is a flat plate, and the distance between the optical axis and a point on the optical window that is closest to the optical axis among points located closest to the reflective optical system in the direction of the optical axis is defined as hWR, and the distance between the optical axis and a point within the effective area of ​​the third reflecting surface that is farthest from the optical axis is defined as hM3, 0.5 <hWR / hM3<3 (5) Conditional expression (5) expressed as follows is satisfied.

[0011] A seventh aspect of the present disclosure is the imaging optical system of the first aspect, wherein, when the optical window is a flat plate and the inclination angle of the optical window with respect to a plane perpendicular to the optical axis is θwin, 30°<θwin<85° (6) Conditional expression (6) expressed as follows is satisfied.

[0012] An eighth aspect of the present disclosure relates to an imaging optical system according to the first aspect, wherein the optical window is a flat plate, the distance between the center of the image and the optical axis is Δs, the length of the short side of the image is ImS, the minimum value of V defined by V=Δs / ImS is Vmin, the length of the long side of the rectangle circumscribing the optical window is WL, the distance in the optical axis direction from the first reflecting surface to the enlarged image is Dsc, the length of the long side of the enlarged image is PrL, and the length of the long side of the image is ImL: 0<(Vmin-0.5)×WL×(Dsc / PrL) / ImL<1.2 (7) Conditional expression (7) expressed as follows is satisfied.

[0013] A ninth aspect of the present disclosure is the imaging optical system of the first aspect, wherein the optical window is a flat plate, and the length of the long side of a rectangle circumscribing the optical window is WL and the length of the short side of the rectangle is WS, 2 <WL / WS<10 (8) Conditional expression (8) expressed as follows is satisfied.

[0014] A tenth aspect of the present disclosure is directed to an imaging optical system according to the first aspect, wherein the optical window is a flat plate, the distance between the center of the image and the optical axis is Δs, the length of the short side of the image is ImS, the minimum value of V defined by V=Δs / ImS is Vmin, the length of the long side of a rectangle circumscribing the optical window is WL, and the length of the short side of the rectangle is WS, 0.5<(Vmin-0.5)×WL / WS<1.5 (9) Conditional expression (9) expressed as follows is satisfied.

[0015] An eleventh aspect of the present disclosure is the imaging optical system of the first aspect, wherein the optical window has a curvature in the direction of the long side of the image.

[0016] A twelfth aspect of the present disclosure provides an imaging optical system according to the eleventh aspect, wherein, when the length of the long side of a rectangle circumscribing the optical window is WpL and the length of the short side of the projection onto a plane perpendicular to the direction from the center of curvature toward the origin used in the equation defining the curved surface of the optical window is WpS, 1 <WpL / WpS<3 (10) Condition (10) expressed by the following expression is satisfied.

[0017] A thirteenth aspect of the present disclosure is the imaging optical system of the eleventh aspect, wherein the optical window is a cylindrical lens.

[0018] A fourteenth aspect of the present disclosure provides an imaging optical system according to the thirteenth aspect, wherein the surface of the optical window on the reduction side is a cylindrical surface, and when the length of the long side of a projection of a rectangle circumscribing the optical window onto a plane perpendicular to the direction from the center of curvature toward the origin used in the equation defining the curved surface of the optical window is WpL, and the radius of curvature of the cylindrical surface in a direction perpendicular to the generatrix of the cylindrical surface is Rcy, 1 <WpL / Rcy<2 (11) Condition (11) expressed by the following expression is satisfied.

[0019] A fifteenth aspect of the present disclosure is an imaging optical system according to the thirteenth aspect, wherein, in the imaging optical system according to the thirteenth aspect, the surface on the reduction side of the optical window is a cylindrical surface, and when a combined focal length of the reflective optical system and the refractive optical system is fRL and a radius of curvature of the cylindrical surface in a direction perpendicular to the generating line of the cylindrical surface is Rcy, 0 <fRL / Rcy<0.1 (12) Condition (12) expressed by the following expression is satisfied.

[0020] A sixteenth aspect of the present disclosure is the imaging optical system of the eleventh aspect, wherein the optical window has a toric shape.

[0021] A seventeenth aspect of the present disclosure is the imaging optical system of the eleventh aspect, wherein the surface of the optical window on the enlargement side and the surface of the optical window on the reduction side are spherical.

[0022] An eighteenth aspect of the present disclosure is the imaging optical system of the eleventh aspect, wherein the optical window has an aspherical shape.

[0023] A nineteenth aspect of the present disclosure is a projection display device including the imaging optical system according to any one of the first to eighteenth aspects.

[0024] A twentieth aspect of the present disclosure is an imaging device including the imaging optical system according to any one of the first to eighteenth aspects.

[0025] In this specification, the terms "consisting of" and "consisting of" are intended to mean that, in addition to the listed components, other optical elements than lenses, such as lenses with substantially no power, apertures, masks, filters, cover glasses, flat mirrors, and prisms, as well as mechanical parts such as lens flanges, lens barrels, image sensors, and image stabilization mechanisms, may also be included.

[0026] Unless otherwise specified, the sign of the power and the surface shape of an optical member including an aspherical surface are considered in the paraxial region. [Effects of the Invention]

[0027] According to the present disclosure, it is possible to provide a compact imaging optical system equipped with an optical window capable of preventing the intrusion of dust and the like, a projection display device equipped with this imaging optical system, and an imaging device equipped with this imaging optical system. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a cross-sectional view showing the configuration of an imaging optical system according to an embodiment and a light beam, which corresponds to the imaging optical system of Example 1. FIG. [Figure 2] 1 is a diagram illustrating a projection display device according to an embodiment in use; [Figure 3] 2 is a cross-sectional view showing the positional relationship between an imaging optical system, a display surface, a magnified image, etc. FIG. [Figure 4] FIG. 2 is a diagram illustrating the positional relationship between the optical axis and the center of an image. [Figure 5] FIG. 10 is a diagram for explaining symbols in a conditional expression. [Figure 6] FIG. 10 is a diagram for explaining symbols in a conditional expression. [Figure 7] FIG. 1 is a schematic diagram illustrating the configuration of an imaging optical system including a rectangular, flat optical window. [Figure 8A] 1A and 1B are diagrams illustrating an example of a light beam cross section and an optical window. [Figure 8B] FIG. 8B shows a rectangle circumscribing the optical window of FIG. 8A. [Figure 9] FIG. 1 is a schematic diagram illustrating the configuration of an imaging optical system including an optical window having a curvature. [Figure 10] FIG. 10 is a diagram showing the projection of a rectangle circumscribing an optical window. [Figure 11] 1A and 1B are diagrams illustrating an example of a light beam cross section and an optical window. [Figure 12A] 1A and 1B are diagrams illustrating an example of a light beam cross section and an optical window. [Figure 12B] FIG. 12B shows a rectangle circumscribing the optical window of FIG. 12A. [Figure 13A] 1A and 1B are diagrams illustrating an example of a light beam cross section and an optical window. [Figure 13B] FIG. 13B is a diagram showing a rectangle circumscribing the optical window of FIG. 13A. [Figure 14]10 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a second embodiment. [Figure 15] 10 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a third embodiment. [Figure 16] 10 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a fourth embodiment. [Figure 17] FIG. 10 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a fifth embodiment. [Figure 18] FIG. 10 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a sixth embodiment. [Figure 19] FIG. 10 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a seventh embodiment. [Figure 20] FIG. 13 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to an eighth embodiment. [Figure 21] FIG. 13 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a ninth embodiment. [Figure 22] FIG. 20 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a tenth embodiment. [Figure 23] FIG. 20 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to an eleventh embodiment. [Figure 24] FIG. 22 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a twelfth embodiment. [Figure 25] FIG. 22 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a thirteenth embodiment. [Figure 26] FIG. 20 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a fourteenth embodiment. [Figure 27] FIG. 20 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a fifteenth embodiment. [Figure 28] FIG. 23 is a cross-sectional view showing the configuration of a modified example in which the imaging optical system of Example 15 is housed inside a housing. [Figure 29] 1 is a schematic configuration diagram of a projection display device according to an embodiment. [Figure 30] FIG. 10 is a schematic configuration diagram of a projection display device according to another embodiment. [Figure 31] FIG. 10 is a schematic configuration diagram of a projection display device according to yet another embodiment. [Figure 32] FIG. 10 is a schematic configuration diagram of a projection display device according to yet another embodiment. [Figure 33] 1 is a perspective view of the front side of an imaging device according to an embodiment. [Figure 34] FIG. 34 is a perspective view of the rear side of the imaging device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, embodiments of the technology of the present disclosure will be described with reference to the drawings.

[0030] 1 shows a cross-sectional view of a configuration and a light beam in a cross section including an optical axis AX of an imaging optical system 1 according to an embodiment of the present disclosure. The configuration example shown in FIG. 1 corresponds to Example 1, which will be described later.

[0031] In the following description, the direction of the optical axis AX of the imaging optical system 1 is referred to as the Z-axis direction, the direction perpendicular to the Z-axis direction and corresponding to the up-down direction in Fig. 1 is referred to as the Y-axis direction, and the direction perpendicular to both the Z-axis direction and the Y-axis direction is referred to as the X-axis direction. The X-axis direction is perpendicular to the plane of the paper in Fig. 1. Regarding the Y-axis direction, the upward direction in Fig. 1 is referred to as the +Y-axis direction, and the downward direction is referred to as the -Y-axis direction.

[0032] The imaging optical system 1 can be mounted in a projection display device as a projection optical system in which a display element is arranged on the reduction-side imaging plane, or can be mounted in a digital camera or the like as an imaging optical system in which an imaging element is arranged on the reduction-side imaging plane. The following description will be given assuming that the imaging optical system 1 is used as a projection optical system.

[0033] Fig. 2 shows a schematic diagram of a projection display device 3 according to an embodiment of the disclosed technology in use. The projection display device 3 includes an imaging optical system 1 and a display element 2 serving as a light valve. In Fig. 2, the imaging optical system 1 and the display element 2 are shown conceptually.

[0034] The display element 2 is an element that outputs an optical image, and this optical image is displayed as an image on a display surface 2a of the display element 2. As the display element 2, for example, a liquid crystal display element or an image display element such as a DMD (Digital Micromirror Device: registered trademark) can be used.

[0035] The imaging optical system 1 enlarges the image on the display surface 2a and forms the enlarged image 6 as a projected image on the screen Scr. The image displayed by the display element 2 and the enlarged image 6 are in an optically conjugate relationship. Optically, the image displayed by the display element 2 can be considered a reduction-side conjugate image, and the enlarged image 6 can be considered an enlargement-side conjugate image. The display surface 2a and the screen Scr are in optically conjugate positions. The display surface 2a is an example of a "reduction-side image forming surface" in the present disclosure, and the screen Scr is an example of a "enlargement-side image forming surface" in the present disclosure.

[0036] In this specification, the term "screen" refers to an object onto which the projection image formed by the imaging optical system 1 is projected. The screen may be, for example, a dedicated screen, or the wall, floor, or ceiling of a room, or the exterior wall of a building.

[0037] In Figure 2, the magnified image 6 is labeled with a point 6a at the top corner, a center 6c, and a point 6b at the bottom that is located directly below the center 6c. Figure 1 shows three light beams: a light beam LFa at the maximum angle of view, a light beam LFc at the intermediate angle of view, and a light beam LFb at the minimum angle of view. As shown in Figure 3, in the magnified image 6, the light beam LFa is focused at point 6a, the light beam LFc is focused at the center 6c, and the light beam LFb is focused at point 6b. Figure 3 shows the configuration of the imaging optical system 1, display surface 2a, magnified image 6, and screen Scr in a cross section including the optical axis AX.

[0038] The imaging optical system 1 in FIG. 1 is composed of, in order from the enlargement side to the reduction side along the optical path, an optical window W, a reflective optical system GR, and a refractive optical system GL including a plurality of lenses.

[0039] In this specification, the "enlargement side" refers to the side of the screen Scr on the optical path, and the "reduction side" refers to the side of the display surface 2a on the optical path. In this specification, the "enlargement side" and "reduction side" are determined along the optical path. For example, in an imaging optical system that forms a folded optical path, "reflective surface A is on the enlargement side of reflective surface B" has the same meaning as "reflective surface A is on the optical path on the enlargement side of reflective surface B." In an imaging optical system that forms a folded optical path, "the side closest to the enlargement side" refers to the side closest to the screen Scr in terms of order on the optical path, and does not mean that the side closest in distance is closest to the screen Scr. In the following, to avoid redundant explanation, "in order along the optical path from the enlargement side to the reduction side" may be expressed as "in order from the enlargement side to the reduction side."

[0040] The reflective optical system GR includes, in order along the optical path from the enlargement side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having power, and a third reflecting surface R3 having positive power.

[0041] Since the reflecting surface itself does not generate chromatic aberration, by arranging three reflecting surfaces on the magnification side of the imaging optical system 1, it is possible to reduce the generation of chromatic aberration throughout the optical system. In addition, since the optical path with three reflections makes it easy to ensure the optical path length, it is possible to configure a compact system despite having a wide angle, and furthermore, it is possible to reduce the power of each optical element. As a result, it is possible to reduce the burden of aberration correction, etc., of the refractive optical system GL, and therefore it is possible to reduce the number of lenses in the refractive optical system GL, contributing to size reduction.

[0042] The first reflecting surface R1 and the third reflecting surface R3 may be formed from the same material and configured to have the same surface shape. In this case, the time and labor required for the relative alignment of each reflecting surface during manufacturing can be reduced, contributing to cost reduction. In addition, performance degradation due to the relative misalignment of each reflecting surface during manufacturing can be suppressed, which is advantageous for ensuring performance.

[0043] Note that "formed on the same member and having the same surface shape" refers to a continuous surface having a shape formed based on the same design data. "The same design data" means that in the case of a spherical shape, the radius of curvature is the same, in the case of an aspherical shape, the aspherical formula and aspherical coefficients are the same, and in the case of a free-form surface shape, the free-form surface formula and free-form surface coefficients are the same.

[0044] As an example, the first reflecting surface R1, the second reflecting surface R2, and the third reflecting surface R3 in FIG. 1 are made up of mirror surfaces. As an example, the refractive optical system GL in FIG. 1 is made up of, in order from the magnification side to the reduction side, lenses L1 to L8, an aperture stop St, and lenses L9 to L14. The aperture stop St shown in FIG. 1 does not indicate its size or shape, but its position in the optical axis direction. As an example, the refractive optical system GL and the reflective optical system GR in FIG. 1 share a common optical axis AX. Such a coaxial system configuration is easier to assemble than a non-coaxial system configuration. Note that if the optical surfaces of the optical components have an axis of rotational symmetry, that axis of rotational symmetry corresponds to the optical axis AX.

[0045] FIG. 1 shows an example in which an optical member PP and a display surface 2a of a display element 2 are arranged on the reduction side of the imaging optical system 1. The optical member PP is a member that is assumed to be a filter, a cover glass, a color synthesis prism, etc. The optical member PP is a member that does not have power, and a configuration in which the optical member PP is omitted is also possible. The optical member PP is not shown in FIG. 2.

[0046] In the imaging optical system 1 of Figure 1, a light beam traveling from the display surface 2a toward the enlargement side passes through the optical member PP and the refractive optical system GL, and then forms a first intermediate image M1. The light beam then enters the third reflecting surface R3, is reflected by the third reflecting surface R3, and then enters the second reflecting surface R2, is reflected by the second reflecting surface R2, and forms a second intermediate image M2. The light beam then enters the first reflecting surface R1, is reflected by the first reflecting surface R1, passes through the optical window W, and forms a projected image on the screen Scr (not shown in Figure 1).

[0047] The imaging optical system 1 has a folded optical path that reflects the light beam three times, resulting in a concentrated light beam, as shown in Figure 1. For example, if we imagine a plane perpendicular to the optical axis AX that passes through the first intermediate image M1, the light beam will pass through this plane four times. If dust or other particles get into this optical path, the intense light may hit the dust or other particles, causing problems. Therefore, the imaging optical system 1 is configured so that an optical window W is located on the most magnification side.

[0048] The optical window W is made of a refractive material that is translucent. Translucency refers to, for example, a transmittance of 80% or more for the wavelength of the light beam. The optical window W is different from a simple opening that is open to the outside. By placing a refractive material that functions as a window on the most magnified side of the imaging optical system 1, it is possible to prevent the intrusion of dust and other foreign matter from the outside. Note that the area of ​​the "optical window" intended in this disclosure is an area that allows light to pass through, and does not include mechanical parts such as a window frame.

[0049] As an example, the optical window W in the example of Fig. 1 is a flat plate with a rectangular outer shape. However, the optical window of the present disclosure is not limited to the example of Fig. 1 and can take various forms. The detailed configuration of the optical window of the present disclosure will be described in detail later.

[0050] In the imaging optical system 1, at least two intermediate images, a first intermediate image M1 and a second intermediate image M2, are formed as images conjugate to the image displayed on the display surface 2a. By forming intermediate images, the focal length of the imaging optical system 1 can be shortened, making it suitable for a wide angle. Furthermore, forming at least two intermediate images is advantageous for realizing an ultra-wide angle optical system. In FIG. 1, the first intermediate image M1 and the second intermediate image M2 are conceptually indicated by thick dashed lines. The shapes of the first intermediate image M1 and the second intermediate image M2 shown in FIG. 1 are not necessarily accurate.

[0051] The first intermediate image M1 is formed on the optical path on the reduction side of the third reflecting surface R3, at a position conjugate with the reduction-side image formation surface. Preferably, the first intermediate image M1 is formed on the optical path between the third reflecting surface R3 and the refractive optical system GL. In this way, if the first intermediate image M1 is not formed within the refractive optical system GL, scratches on the lens and / or dust can be prevented from being projected, which is advantageous for forming a good projected image.

[0052] The second intermediate image M2 is formed within the reflective optical system GR at a position conjugate with the first intermediate image M1. The magnified image 6 is formed at a position conjugate with the second intermediate image M2. "Within the reflective optical system GR" means within the optical path from the surface of the reflective optical system GR on the most enlargement side to the surface of the reflective optical system GR on the most reduction side. Forming the second intermediate image M2 within the reflective optical system GR helps prevent scratches and / or dust from being projected on the lens, which is advantageous for forming a good projected image.

[0053] The second intermediate image M2 is preferably formed on the optical path between the first reflecting surface R1 and the second reflecting surface R2, which is advantageous for forming a good projected image because it is possible to prevent scratches and / or dust on the reflecting surface from being projected.

[0054] It is preferable that the intermediate images formed on the magnification side of the refractive optical system GL are only two, the first intermediate image M1 and the second intermediate image M2. In this case, it is advantageous to configure a compact optical system while realizing a wide-angle optical system. Furthermore, for the sake of compactness, the imaging optical system 1 may be configured to form only two intermediate images, the first intermediate image M1 and the second intermediate image M2.

[0055] A configuration may be adopted in which no refractive member is disposed in the optical path between the first reflecting surface R1 and the second reflecting surface R2. If a refractive member is disposed in the optical path between the first reflecting surface R1 and the second reflecting surface R2, a problem occurs in which scratches and / or dust on the refractive member may be projected. However, by not disposing a refractive member, this problem can be avoided. This also contributes to simplifying the device configuration. For similar reasons, a configuration may be adopted in which no refractive member is disposed in the optical path between the second reflecting surface R2 and the third reflecting surface R3.

[0056] In this example, the center of the image displayed on the display surface 2a is not located on the optical axis AX, but is shifted from the optical axis AX in the -Y-axis direction, which is perpendicular to the optical axis AX. Figure 4 shows the schematic positional relationship between the optical axis AX on the image circle IC on the reduction side of the imaging optical system 1 and the image 4 displayed on the display surface 2a. In this example, the long side direction of the image 4 is the X-axis direction, and the short side direction is the Y-axis direction. Hereinafter, the amount of shift, i.e., the distance between the center 4c of the image 4 and the optical axis AX, will be referred to as the shift amount Δs. For example, if the imaging optical system 1 and the display element 2 are configured to be relatively movable in the direction perpendicular to the optical axis AX, the shift amount Δs will be variable.

[0057] When the center 4c of the image 4 is shifted in the -Y-axis direction from the optical axis AX, the center 6c of the magnified image 6 projected onto the screen Scr is also not located on the optical axis AX of the imaging optical system 1, but is shifted in the +Y-axis direction, which is perpendicular to the optical axis AX, as shown in Figure 3. This configuration makes it possible to position the magnified image 6 above the imaging optical system 1. This is effective, for example, when the projection display device 3 is placed on the floor and it is desired to project the image onto a screen or the like that is above the floor.

[0058] The center of the image displayed on the display surface 2a is the intersection of the diagonals of the rectangle if the image is rectangular, the center of the circle if the image is circular, and the intersection of the diagonals of the trapezoid if the image is trapezoidal. Similarly, the center of the enlarged image that is the projected image is the intersection of the diagonals of the rectangle if the enlarged image is rectangular, the center of the circle if the enlarged image is circular, and the intersection of the diagonals of the trapezoid if the enlarged image is trapezoidal.

[0059] Hereinafter, the chief ray that is incident on the center 6c of the magnified image 6 when the shift amount Δs is at its maximum will be referred to as the central chief ray Cray. The central chief ray Cray is a ray contained in the light beam LFc. As an example, the central chief ray Cray is shown in FIGS. 3 and 5. FIG. 5 shows the configuration of the imaging optical system 1 of FIG. 1 in a cross section including the optical axis AX. In FIG. 5, some reference numerals are omitted compared to FIG. 1.

[0060] 5, it is preferable that the intersection P1 between the central chief ray Cray and the enlargement-side surface of the optical window W be located closer to the third reflecting surface R3 than the entire second reflecting surface R2 in the direction of the optical axis AX, which is advantageous for making the optical window W smaller.

[0061] Furthermore, to reduce the size of the optical window W, it is preferable that the entire optical window W be located closer to the third reflecting surface R3 than point P2, which is located on the most magnified side of the refractive optical system GL, in the direction of the optical axis AX, as shown in FIG. 6. FIG. 6 shows the configuration of the imaging optical system 1 of FIG. 1 in a cross section including the optical axis AX. For ease of understanding, some reference numerals and light beams have been omitted from FIG. 6 compared to FIG. 1. In the example of FIG. 6, the most magnified surface of the refractive optical system GL is a convex surface, and therefore the vertex of this convex surface (a point on the optical axis AX of the convex surface) is point P2. However, if the most magnified surface of the refractive optical system GL is a concave surface, point P2 located on the most magnified side of the refractive optical system GL may be a point on the periphery of the concave surface rather than a point on the optical axis AX.

[0062] Next, preferred and possible configurations regarding the conditional expressions of the imaging optical system of the present disclosure will be described. Hereinafter, to avoid redundant explanation, the "imaging optical system of the present disclosure" may be referred to simply as the "imaging optical system." Furthermore, in the following explanation of the conditional expressions, the same symbols are used for elements with the same definitions, and redundant explanations of the symbols will be omitted to avoid redundant explanation.

[0063] If the angle of incidence of the central chief ray Cray on the magnification-side image forming surface is α, it is preferable that the imaging optical system satisfy the following conditional expression (1). In this example, the screen Scr corresponds to the magnification-side image forming surface. As an example, the above-mentioned angle of incidence α is shown in FIG. 3. In FIG. 3, the plane perpendicular to the screen Scr is indicated by a dashed line. In this example, the angle of incidence α is the angle formed between the central chief ray Cray and the plane perpendicular to the magnification-side image forming surface. Ensuring that the corresponding value of conditional expression (1) is not equal to or smaller than the lower limit is advantageous for widening the angle of the imaging optical system. Ensuring that the corresponding value of conditional expression (1) is not equal to or larger than the upper limit is advantageous for projecting an image on a flat surface without distortion. 40°<|α|<85° (1)

[0064] To obtain better characteristics, the lower limit of conditional expression (1) should preferably be set to 50°, and more preferably to 60°. To obtain even better characteristics, the upper limit of conditional expression (1) should preferably be set to 80°.

[0065] If the angle of incidence of the central chief ray Cray on the optical window W is θc, it is preferable that the imaging optical system satisfy the following conditional expression (2). As an example, the above-mentioned angle of incidence θc is shown in FIG. 5. In FIG. 5, the plane perpendicular to the optical window W is indicated by a dashed line. The lower limit of conditional expression (2) is 0°<|θc| because |θc| is an absolute value. By ensuring that the corresponding value of conditional expression (2) is not greater than the upper limit, it is possible to prevent the optical window W from becoming larger, and in particular, to prevent the optical window W from becoming longer in the short side direction. 0°<|θc|<35° (2)

[0066] In order to obtain better characteristics, the upper limit of conditional expression (2) should more preferably be set to 30°, and even more preferably to 25°.

[0067] If the maximum half angle of view on the enlargement side is ω, it is preferable that the imaging optical system satisfy the following conditional expression (3). ω is the largest angle between the optical axis AX and the chief ray traveling from the surface of the imaging optical system closest to the enlargement side toward the enlargement-side image plane. In this example, ω corresponds to the angle between the optical axis AX and the chief ray of the light beam LFa. As an example, FIG. 5 shows the above maximum half angle of view ω. By ensuring that the value corresponding to conditional expression (3) is not equal to or smaller than the lower limit, a wide-angle optical system can be realized. By ensuring that the value corresponding to conditional expression (3) is not equal to or larger than the upper limit, light blocking due to relatively fine irregularities on the wall surface of the screen Scr can be suppressed. 65°<ω<90° (3)

[0068] In order to obtain better characteristics, the lower limit of conditional expression (3) should more preferably be set to 70°, and even more preferably to 75°.

[0069] It is preferable that the imaging optical system satisfy the following conditional expression (4). Here, hWmin is the distance between the optical axis AX and the point on the optical window W closest to the optical axis AX. ra is the radius of the lens on the magnification side of the refractive optical system GL. As an example, FIG. 6 shows the above distance hWmin and radius ra. Note that if the outer shape of the lens is non-circular, ra is the maximum lens radius. By ensuring that the corresponding value of conditional expression (4) is not equal to or less than the lower limit, it is easy to prevent interference between the optical window W and the refractive optical system GL. By ensuring that the corresponding value of conditional expression (4) is not equal to or greater than the upper limit, it is advantageous for reducing the size of the optical window W. 0.9 <hWmin / ra<3 (4)

[0070] In order to obtain better characteristics, it is more preferable that the lower limit of conditional expression (4) be set to 1. In order to obtain better characteristics, it is more preferable that the upper limit of conditional expression (4) be set to 2.7, and even more preferable that it be set to 2.5.

[0071] The optical window of the present disclosure may be configured as a flat plate, which is advantageous in that it is easy to manufacture and reduces costs.

[0072] When the optical window is a flat plate, it is preferable that the imaging optical system satisfy the following conditional expression (5). Here, hWR is the distance between the optical axis AX and the point closest to the optical axis AX among the points on the optical window closest to the reflective optical system GR in the direction of the optical axis AX. hM3 is the distance between the optical axis AX and the point farthest from the optical axis AX among the points within the effective area of ​​the third reflecting surface R3. The "effective area" here refers to a mirror surface having a reflectivity of 80% or higher for the wavelength of the light beam. As an example, Figure 6 shows the distances hWR and hM3. By ensuring that the value corresponding to conditional expression (5) is not less than the lower limit, it is easy to prevent interference between the light beam traveling toward the third reflecting surface R3 and the optical window W. By ensuring that the value corresponding to conditional expression (5) is not less than the upper limit, it is advantageous for reducing the size of the optical window W. 0.5 <hWR / hM3<3 (5)

[0073] To obtain even better characteristics, the lower limit of conditional expression (5) should preferably be set to 0.7, and the upper limit of conditional expression (5) should preferably be set to 2, and even more preferably to 1.5.

[0074] When the optical window is a flat plate, it is preferable that the imaging optical system satisfy the following conditional expression (6). Here, the inclination angle of the optical window with respect to a plane perpendicular to the optical axis AX is θwin. As an example, the inclination angle θwin is shown in FIG. 6. In FIG. 6, the plane perpendicular to the optical axis AX is indicated by a dashed line. By ensuring that the value corresponding to conditional expression (6) is not less than the lower limit, it becomes easy to reduce the size of the optical window W while maintaining a configuration that can accommodate light beams with a wide angle of view. By ensuring that the value corresponding to conditional expression (6) is not more than the upper limit, it becomes easy to reduce the size of the optical window W while maintaining a configuration that can accommodate light beams with a narrow angle of view. 30°<θwin<85° (6)

[0075] In order to obtain better characteristics, the lower limit of conditional expression (6) should preferably be set to 40°, and more preferably to 50°.In order to obtain better characteristics, the upper limit of conditional expression (6) should preferably be set to 82°, and even more preferably to 80°.

[0076] When the optical window is flat, it is preferable that the imaging optical system satisfy the following conditional expression (7). Here, the shift amount, which is the distance between the center 4c of the image 4 and the optical axis AX, is Δs. The length of the short side of the image 4 is ImS. The minimum value of V, defined as V = Δs / ImS, is Vmin. The length of the long side of the rectangle circumscribing the optical window is WL. The distance from the first reflecting surface R1 to the magnified image 6 in the direction of the optical axis AX is Dsc. The length of the long side of the magnified image 6 is PrL. The length of the long side of the image 4 is ImL. As described above, for example, if the imaging optical system 1 and the display element 2 are configured to be relatively movable in a direction perpendicular to the optical axis AX, the shift amount Δs is variable, and therefore V is also variable. Vmin is the minimum value that V can take. Satisfying conditional expression (7) is advantageous for reducing the size of the optical window. 0<(Vmin-0.5)×WL×(Dsc / PrL) / ImL<1.2 (7)

[0077] In order to obtain better characteristics, it is more preferable to set the upper limit of conditional expression (7) to 1, and even more preferable to set it to 0.8.

[0078] If the optical window is rectangular, the length of the long side of the rectangle is WL. If the image displayed on the display surface 2a is not rectangular, the length of the short side of the rectangle circumscribing the image is ImS, and the length of the long side is ImL. If the enlarged image projected onto the screen is not rectangular, the length of the long side of the rectangle circumscribing the enlarged image is PrL.

[0079] As an example, the shift amount Δs, the length ImS, and the length ImL are shown in Fig. 4. As an example, the distance Dsc is shown in Fig. 3, the length PrL is shown in Fig. 2, and the length WL is shown in Fig. 7.

[0080] 7 shows a schematic configuration diagram of the imaging optical system, optical member PP, and display element 2 of FIG. 1 when viewed from above to below in FIG. 1 in the normal direction of the optical window W. FIG. 7 shows only a schematic representation of the reflective optical system GR, refractive optical system GL, optical member PP, and display element 2. The long side of the optical window W in FIG. 7 is in the X-axis direction, which is the same as the long side of the image displayed by the display element 2. FIG. 7 also shows the length WL of the long side and the length WS of the short side of the optical window W.

[0081] In Figure 7, the beam cross section LF1, which is the cross section of the beam for imaging on the surface of the optical window W, is shown with diagonal lines. For ease of explanation, the cross section of the beam for imaging on the surface of the optical window will be referred to as the "beam cross section" below. The optical window W in Figure 7 is rectangular in size and includes the beam cross section LF1.

[0082] However, in the technology disclosed herein, the outer shape of the optical window is not limited to a rectangle and can be set arbitrarily. For example, the trapezoidal optical window W1 shown in FIG. 8A may be used for the light beam cross section LF1 of FIG. 7. The light beam cross section LF1 of FIG. 8A has the same shape as the light beam cross section LF1 of FIG. 7. FIG. 8B shows a rectangle RecW1 circumscribing the optical window W1 with a dashed line, and also shows the length WL of the long side and the length WS of the short side of the rectangle RecW1. Compared to the optical window W of FIG. 7, the optical window W1 of FIG. 8A is advantageous in terms of reducing the size and weight of the optical window and in terms of blocking stray light entering from the outside.

[0083] When the optical window is a flat plate, it is preferable that the imaging optical system satisfy the following conditional expression (8). Here, the length of the short side of the rectangle circumscribing the optical window is WS. Ensuring that the corresponding value of conditional expression (8) is not equal to or smaller than the lower limit thereof is advantageous for widening the angle of the imaging optical system. Ensuring that the corresponding value of conditional expression (8) is not equal to or larger than the upper limit thereof is advantageous for reducing the size of the optical window in the long side direction. 2 <WL / WS<10 (8)

[0084] In order to obtain better characteristics, the lower limit of conditional expression (8) should preferably be set to 3, and more preferably to 4. In order to obtain better characteristics, the upper limit of conditional expression (8) should preferably be set to 9, and even more preferably to 8.

[0085] When the optical window is a flat plate, it is preferable that the imaging optical system satisfy the following conditional expression (9): Ensuring that the corresponding value of conditional expression (9) is not equal to or smaller than the lower limit thereof is advantageous for widening the angle of the imaging optical system. Ensuring that the corresponding value of conditional expression (9) is not equal to or larger than the upper limit thereof is advantageous for reducing the size of the optical window in the long side direction. 0.5<(Vmin-0.5)×WL / WS<1.5 (9)

[0086] In order to obtain better characteristics, the lower limit of conditional expression (9) should preferably be set to 0.6, and more preferably to 0.7, and the upper limit of conditional expression (9) should preferably be set to 1.3, and even more preferably to 1.1.

[0087] The optical window of the present disclosure may be configured to have a curvature. Configuring the optical window to have a curvature can contribute to miniaturization of the optical window. For example, configuring the optical window to have a curvature in the long-side direction of the image displayed by the display element 2 can reduce the size of the optical window in the long-side direction. As an example, FIG. 9 shows a perspective view of the configuration of an imaging optical system using an optical window W5 having a curvature in the long-side direction of the image displayed by the display element 2. In FIG. 9, the long-side direction of the image is defined as the X direction. In FIG. 9, each component is shown schematically.

[0088] When the optical window has a curvature in the long-side direction of the image displayed by the display element 2, it is preferable that the imaging optical system satisfy the following conditional expression (10). Here, the length of the long side of a projection of a rectangle circumscribing the optical window onto a plane perpendicular to the direction from the center of curvature of the optical window toward the origin used in the expression defining the curved surface of the optical window is defined as WpL, and the length of the short side of this projection is defined as WpS. Note that when the enlargement-side surface and the reduction-side surface of the optical window have curvature, WpL and WpS are values ​​relating to the enlargement-side surface of the optical window. Ensuring that the corresponding value of conditional expression (10) is not equal to or less than the lower limit is advantageous for widening the angle of view of the imaging optical system. Ensuring that the corresponding value of conditional expression (10) is not equal to or greater than the upper limit is advantageous for reducing the size of the optical window in the long-side direction. 1 <WpL / WpS<3 (10)

[0089] In order to obtain better characteristics, the lower limit of conditional expression (10) should preferably be set to 1.2, and more preferably to 1.5.In order to obtain better characteristics, the upper limit of conditional expression (10) should preferably be set to 2.8, and even more preferably to 2.5.

[0090] As an example, Fig. 10 shows the optical window W5 having a curvature, the projection W5p, the length WpL, and the length WpS. In Fig. 10, the direction from the center of curvature of the optical window W5 to the origin used in the equation defining the curved surface of the optical window W5 is indicated by a two-dot chain line.

[0091] When the optical window has a curvature, the optical window may be configured to be a cylindrical lens. Although the effect of miniaturization is small when the optical window has a curvature in the short-side direction of the image, miniaturization can be effectively achieved by configuring the optical window to have a curvature in the long-side direction of the image. Furthermore, it is easier to fabricate a configuration with a curvature in only one of the short-side and long-side directions of the image than a configuration with a curvature in both the short-side and long-side directions. For these reasons, by forming the optical window into a cylindrical shape, miniaturization can be effectively achieved while ensuring mass productivity.

[0092] When the optical window is a cylindrical lens and the reduction-side surface of the optical window is a cylindrical surface, it is preferable that the imaging optical system satisfy the following conditional expression (11). Here, the radius of curvature of the cylindrical surface in a direction perpendicular to the generatrix of the cylindrical surface is defined as Rcy. The direction perpendicular to the generatrix of the cylindrical surface is the direction in which the curvature exists. The sign of Rcy is positive for a shape with a convex surface facing the enlargement side and negative for a shape with a convex surface facing the reduction side. Ensuring that the corresponding value of conditional expression (11) is not equal to or less than the lower limit thereof is advantageous for miniaturizing the optical window in the direction in which the curvature exists. Ensuring that the corresponding value of conditional expression (11) is not equal to or greater than the upper limit thereof allows for a suitable configuration as a cylindrical lens. 1 <WpL / Rcy<2 (11)

[0093] In order to obtain better characteristics, it is more preferable to set the lower limit of conditional expression (11) to 1.2, and even more preferable to set it to 1.5.

[0094] When the optical window is a cylindrical lens and the surface of the optical window on the reduction side is a cylindrical surface, it is preferable that the imaging optical system satisfy the following conditional expression (12). Here, fRL is the composite focal length of the reflective optical system GR and the refractive optical system GL included in the imaging optical system. Ensuring that the corresponding value of conditional expression (12) is not equal to or smaller than the lower limit thereof is advantageous for reducing the size of the optical window in the direction of curvature. Ensuring that the corresponding value of conditional expression (12) is not equal to or larger than the upper limit thereof is advantageous for reducing the size of the imaging optical system. 0 <fRL / Rcy<0.1 (12)

[0095] In order to obtain better characteristics, it is more preferable to set the upper limit of conditional expression (12) to 0.08, and even more preferable to set it to 0.06.

[0096] If the optical window has a curvature, the optical window may be configured to have a toric shape, which facilitates miniaturization in accordance with the aspect ratio of the image.

[0097] When the optical window has a curvature, the surface on the enlargement side and the surface on the reduction side of the optical window may be configured to be spherical. In this case, in addition to the effect of miniaturization, the optical window can also be provided with an aberration correction function. Furthermore, since it can be manufactured in the same way as a spherical lens, high costs can be suppressed.

[0098] When the optical window has a curvature, the optical window may be configured to have an aspherical shape, which not only provides the effect of miniaturization but also provides the effect of providing the optical window with a better aberration correction function.

[0099] When the optical window has a curvature, the light beam cross section also varies depending on the curvature. When the optical window has a curvature, the "light beam cross section" refers to the cross section of the light beam for imaging in the tangent plane of the optical window at the center position of the enlarged surface of the optical window. Examples of light beam cross sections and optical windows are schematically shown in Figures 11, 12A, 12B, 13A, and 13B.

[0100] Fig. 11 shows a light beam cross section LF2 and a rectangular optical window W2. In Fig. 11, the light beam cross section LF2 is shaded. The left-right direction in Fig. 11 is the X-axis direction, i.e., the direction of the long side of the image displayed by the display element. The light beam cross section LF2 is an example when a cylindrical optical window is used, for example.

[0101] The trapezoidal optical window W3 shown in Figure 12A may be used for the light beam cross section LF2 of Figure 11. The light beam cross section LF2 of Figure 12A has the same shape as the light beam cross section LF2 of Figure 11. Figure 12B shows a rectangle RecW3 circumscribing the optical window W3 with a dashed line, and also shows the length WL of the long side and the length WS of the short side of the rectangle RecW3. Compared to the optical window W2 of Figure 11, the optical window W3 of Figure 12A is advantageous in terms of reducing the size and weight of the optical window and in blocking stray light entering from the outside.

[0102] FIG. 13A shows a light beam cross section LF3 and an optical window W4 shaped like a portion of a substantially circular ring. In FIG. 13A, the light beam cross section LF3 is hatched. The left-right direction in FIG. 13A is the X-axis direction, i.e., the direction of the long side of the image displayed by the display element. The light beam cross section LF3 is an example of a case where an optical window with aspherical surfaces on the enlargement side and reduction side is used. In FIG. 13B, a rectangle RecW4 circumscribing the optical window W4 is shown by a dashed line, along with the length WL of the long side and the length WS of the short side of the rectangle RecW4.

[0103] Note that the symbols WL in Figures 7, 8B, 11, 12B, and 13B are intended to indicate the same concept and do not necessarily indicate that they have the same value. Similarly, the symbols WS in Figures 7, 8B, 11, 12B, and 13B are intended to indicate the same concept and do not necessarily indicate that they have the same value.

[0104] The above-described preferred and possible configurations, including those related to the conditional expressions, can be arbitrarily combined within a range that does not contradict each other, and it is preferable that they be selectively adopted as appropriate according to the required specifications. Various modifications are possible within a range that does not deviate from the gist of the technology of the present disclosure.

[0105] For example, in the technology of the present disclosure, the number of lenses and the number of reflective surfaces included in the imaging optical system may be different from the example shown in FIG. 1. The reflective optical system GR may be configured to include the above three reflective surfaces, or may include optical elements other than the above three reflective surfaces. The reflective surfaces are not limited to mirror surfaces and may be, for example, surfaces formed on the surfaces of lenses or prisms. The refractive optical system GL may include optical elements other than lenses. For example, the refractive optical system GL may include a plane mirror. The imaging optical system may include an optical path bending element that does not have the power to bend the optical path. For example, a plane mirror or a reflective surface of a prism may be used as the optical path bending element.

[0106] As an example, a preferred embodiment of the imaging optical system of the present disclosure is an imaging optical system 1 capable of forming an enlarged image 6 on an enlargement-side image forming surface by enlarging an image 4 on a reduction-side image forming surface, and the imaging optical system 1 comprises, in order from the enlargement side to the reduction side along the optical path, an optical window W, a reflective optical system GR, and a refractive optical system GL including a plurality of lenses, the reflective optical system GR including, in order from the enlargement side to the reduction side along the optical path, a first reflecting surface R1 having positive power, a second reflecting surface R2 having power, and a third reflecting surface R3 having positive power, and the optical path is further from the third reflecting surface R3 to the reduction side. A first intermediate image M1 is formed on the optical axis AX of the refractive optical system GL at a position conjugate with the image, a second intermediate image M2 is formed within the reflective optical system GR at a position conjugate with the first intermediate image M1, an enlarged image is formed on the optical path on the enlargement side of the optical window W at a position conjugate with the second intermediate image M2, and the center of the enlarged image is at a position shifted in a direction perpendicular to the optical axis AX with respect to the optical axis AX of the refractive optical system GL, and when the chief ray incident on the center of the enlarged image at the state where the amount of shift is maximum is defined as the central chief ray Cray, the above conditional expressions (1) and (2) are satisfied.

[0107] Next, examples of the imaging optical system of the present disclosure will be described with reference to the drawings. Note that the reference symbols assigned to the components of the imaging optical system in the cross-sectional views of each example are used independently for each example to avoid cluttering the explanation and drawings due to an increase in the number of digits in the reference symbols. Therefore, even if common reference symbols are assigned in drawings of different examples, this does not necessarily mean that the components have the same configuration.

[0108] [Example 1] The configuration of the imaging optical system of the first embodiment and a cross-sectional view of the light beam are shown in FIG. 1, and the illustration method and configuration are as described above, so some overlapping explanations will be omitted here.

[0109] The imaging optical system of Example 1 comprises, in order along the optical path from the enlargement side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the enlargement side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having positive power, and a third reflecting surface R3 having positive power. The first reflecting surface R1 and the third reflecting surface R3 are formed of the same member and have the same surface shape. The refractive optical system GL comprises, in order from the enlargement side to the reduction side, lenses L1 to L8, an aperture stop St, and lenses L9 to L14. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0110] Tables 1 to 4 show data on the imaging optical system of Example 1. Table 1 shows the configuration of each optical window W. Table 2 shows construction data for the reflective optical system GR, the refractive optical system GL, and the optical member PP. Table 3 shows specifications for the composite optical system formed by combining the reflective optical system GR and the refractive optical system GL. Table 4 shows the aspherical coefficients of each aspherical surface.

[0111] In Table 1, "center position" refers to the center position of the optical window W when the intersection of the first reflecting surface R1 and the optical axis AX is used as the reference. "Normal direction" refers to the normal direction at the center position of the optical window W. "Size" refers to the dimension when viewed from the normal direction of the optical window W. The X-axis direction is the long side direction. "Center thickness" refers to the center thickness in the normal direction. "Refractive index" refers to the refractive index for the d-line. "Abbe number" refers to the Abbe number based on the d-line. The wavelength of the d-line is 587.56 nm (nanometers).

[0112] The construction data table in Table 2 is written as follows. The Sn column shows the surface number, with the surface closest to the enlargement side designated as surface 1 and the numbers increasing by one as you move toward the reduction side. The R column shows the radius of curvature of each surface. The D column shows the surface distance on the optical axis AX between each surface and its adjacent surface on the reduction side. The Nd column shows the refractive index for the d-line of each component element. The νd column shows the Abbe number of each component element based on the d-line. The Nd column in the row corresponding to each reflective surface is marked "reflective surface."

[0113] In the construction data table, the sign of the radius of curvature of a surface that is convex on the enlargement side is positive, and the sign of the radius of curvature of a surface that is convex on the reduction side is negative. The column for the surface number corresponding to the aperture stop St lists the surface number and the term (St). The value in the bottom column of the D column in the table is the distance between the surface closest to the reduction side and display surface 2a.

[0114] Table 3 shows the focal length (f), the back focus (Bf) in air equivalent distance, the F-number (FNo.), and the maximum full angle of view (2ω) of the above composite optical system, based on the d-line. The [°] in the 2ω column indicates that the unit is degrees.

[0115] In the construction data, the surface numbers of aspherical surfaces are marked with an *, and the value of the paraxial radius of curvature is listed in the column for the radius of curvature of the aspherical surface. In Table 4, the Sn row shows the surface numbers of aspherical surfaces, and the KA and Am rows show the numerical values ​​of the aspherical coefficients for each aspherical surface. Note that m in Am is an integer of 3 or more, and varies depending on the surface. For example, for the first surface in Example 1, m = 3, 4, 5, ... 20. The numerical values ​​of the aspherical coefficients in Table 4, "E±n" (n: integer), are expressed as "×10 ±n KA and Am are aspherical coefficients in the aspherical formula given below. Zd=C×h 2 / {1+(1-KA×C 2 ×h 2 ) 1 / 2}+ΣAm×h m however, Zd: Aspheric depth (length of the perpendicular line drawn from a point on the aspheric surface at height h to a plane perpendicular to the optical axis AX where the vertex of the aspheric surface is in contact) h: Height (distance from the optical axis AX to the lens surface) C: Reciprocal of paraxial curvature radius KA, Am: aspherical coefficients In the aspherical formula, Σ means the summation over m.

[0116] In the data in each table, degrees are used as the unit of angle and mm (millimeters) as the unit of length, but since the optical system can be used with proportional enlargement or reduction, other appropriate units can also be used. Also, in each table below, values ​​are listed rounded to a certain number of decimal places.

[0117] [Table 1]

[0118] [Table 2]

[0119] [Table 3]

[0120] [Table 4]

[0121] The symbols, meanings, notation, and illustration methods for each data item in Example 1 above are basically the same in the following examples unless otherwise specified, and therefore will not be described again below. The X-axis, Y-axis, and Z-axis directions in the following examples are also the same as in Example 1. In all of the following examples, the optical window W has a rectangular shape when viewed from the normal direction of the optical window W, and the long side of the rectangle is in the X-axis direction. In the following examples that have a curvature-bearing optical window W, the tables showing the configuration of the optical window W list values ​​related to the surface of the enlarged side of the optical window W.

[0122] [Example 2] FIG. 14 shows a cross-sectional view of the configuration of the imaging optical system of Example 2 and the light beam. The imaging optical system of Example 2 comprises, in order along the optical path from the magnification side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the magnification side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having positive power, and a third reflecting surface R3 having positive power. The first reflecting surface R1 and the third reflecting surface R3 are formed of the same member and have the same surface shape. The refractive optical system GL comprises, in order from the magnification side to the reduction side, lenses L1 to L8, an aperture stop St, and lenses L9 to L14. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0123] Tables 5 to 8 show data for the imaging optical system of Example 2. Table 5 shows the configuration of the optical window W. Table 6 shows construction data for the reflective optical system GR, the refractive optical system GL, and the optical member PP. Table 7 shows specifications for the composite optical system formed by combining the reflective optical system GR and the refractive optical system GL. Table 8 shows the aspherical coefficients of each aspherical surface.

[0124] [Table 5]

[0125] [Table 6]

[0126] [Table 7]

[0127] [Table 8]

[0128] [Example 3] FIG. 15 shows a cross-sectional view of the configuration of the imaging optical system of Example 3 and the light beam. The imaging optical system of Example 3 comprises, in order along the optical path from the magnification side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the magnification side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having power, and a third reflecting surface R3 having positive power. The refractive optical system GL comprises, in order from the magnification side to the reduction side, lenses L1 to L7, an aperture stop St, and lenses L8 to L12. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0129] Tables 9 to 12 show data for the imaging optical system of Example 3. Table 9 shows the configuration of the optical window W. Table 10 shows construction data for the reflective optical system GR, the refractive optical system GL, and the optical member PP. Table 11 shows specifications for the composite optical system formed by combining the reflective optical system GR and the refractive optical system GL. Table 12 shows the aspherical coefficients of each aspherical surface.

[0130] [Table 9]

[0131] [Table 10]

[0132] [Table 11]

[0133] [Table 12]

[0134] [Example 4] FIG. 16 shows a cross-sectional view of the configuration of the imaging optical system of Example 4 and the light beam. The imaging optical system of Example 4 comprises, in order along the optical path from the magnification side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the magnification side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having power, and a third reflecting surface R3 having positive power. The refractive optical system GL comprises, in order from the magnification side to the reduction side, lenses L1 to L7, an aperture stop St, and lenses L8 to L12. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0135] Tables 13 to 16 show data for the imaging optical system of Example 4. Table 13 shows the configuration of the optical window W. Table 14 shows construction data for the reflective optical system GR, the refractive optical system GL, and the optical member PP. Table 15 shows specifications for the composite optical system formed by combining the reflective optical system GR and the refractive optical system GL. Table 16 shows the aspherical coefficients of each aspherical surface.

[0136] [Table 13]

[0137] [Table 14]

[0138] [Table 15]

[0139] [Table 16]

[0140] [Example 5] FIG. 17 shows a cross-sectional view of the configuration of the imaging optical system of Example 5 and the light beam. The imaging optical system of Example 5 comprises, in order along the optical path from the magnification side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the magnification side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having power, and a third reflecting surface R3 having positive power. The refractive optical system GL comprises, in order from the magnification side to the reduction side, lenses L1 to L6, an aperture stop St, and lenses L7 to L11. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0141] Tables 17 to 20 show data for the imaging optical system of Example 5. Table 17 shows the configuration of the optical window W. Table 18 shows construction data for the reflective optical system GR, the refractive optical system GL, and the optical member PP. Table 19 shows specifications for the composite optical system formed by combining the reflective optical system GR and the refractive optical system GL. Table 20 shows the aspherical coefficients of each aspherical surface.

[0142] [Table 17]

[0143] [Table 18]

[0144] [Table 19]

[0145] [Table 20]

[0146] [Example 6] FIG. 18 shows a cross-sectional view of the configuration of the imaging optical system of Example 6 and the light beam. The imaging optical system of Example 6 comprises, in order along the optical path from the magnification side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the magnification side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having power, and a third reflecting surface R3 having positive power. The refractive optical system GL comprises, in order from the magnification side to the reduction side, lenses L1 to L6, an aperture stop St, and lenses L7 to L11. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0147] Tables 21 to 24 show data for the imaging optical system of Example 6. Table 21 shows the configuration of each optical window W. Table 22 shows construction data for the reflective optical system GR, the refractive optical system GL, and the optical member PP. Table 23 shows specifications for the composite optical system formed by combining the reflective optical system GR and the refractive optical system GL. Table 24 shows the aspherical coefficients of each aspherical surface.

[0148] [Table 21]

[0149] [Table 22]

[0150] [Table 23]

[0151] [Table 24]

[0152] [Example 7] FIG. 19 shows a cross-sectional view of the configuration of the imaging optical system of Example 7 and the light beam. The imaging optical system of Example 7 comprises, in order along the optical path from the magnification side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the magnification side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having power, and a third reflecting surface R3 having positive power. The refractive optical system GL comprises, in order from the magnification side to the reduction side, lenses L1 to L6, an aperture stop St, and lenses L7 to L11. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0153] Tables 25 to 28 show data for the imaging optical system of Example 7. Table 25 lists the configuration of the optical window W. The "Origin of the Curved Surface Equation" in Table 25 is the origin used in the equation defining the curved surface of the optical window W, and Table 25 shows the position of this origin relative to the intersection of the first reflecting surface R1 and the optical axis AX. The "Long Side Direction" and "Short Side Direction" in the "Shape" column in Table 25 refer to the directions when viewing the optical window W from the normal direction of the optical window W. Table 26 lists construction data for the reflective optical system GR, the refractive optical system GL, and the optical member PP. Table 27 lists the specifications of the composite optical system combining the reflective optical system GR and the refractive optical system GL. Table 28 lists the aspherical coefficients of each aspheric surface.

[0154] [Table 25]

[0155] [Table 26]

[0156] [Table 27]

[0157] [Table 28]

[0158] [Example 8] FIG. 20 shows a cross-sectional view of the configuration of the imaging optical system of Example 8 and the light beam. The imaging optical system of Example 8 comprises, in order along the optical path from the magnification side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the magnification side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having power, and a third reflecting surface R3 having positive power. The refractive optical system GL comprises lenses L1 to L6, an aperture stop St, and lenses L7 to L12. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0159] Tables 29 to 32 show data for the imaging optical system of Example 8. Table 29 shows the configuration of each optical window W. Table 30 shows construction data for the reflective optical system GR, the refractive optical system GL, and the optical member PP. Table 31 shows specifications for the composite optical system formed by combining the reflective optical system GR and the refractive optical system GL. Table 32 shows the aspherical coefficients of each aspherical surface.

[0160] [Table 29]

[0161] [Table 30]

[0162] [Table 31]

[0163] [Table 32]

[0164] [Example 9] FIG. 21 shows a cross-sectional view of the configuration of the imaging optical system of Example 9 and the light beam. The imaging optical system of Example 9 comprises, in order along the optical path from the magnification side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the magnification side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having power, and a third reflecting surface R3 having positive power. The refractive optical system GL comprises, in order from the magnification side to the reduction side, lenses L1 to L6, an aperture stop St, and lenses L7 to L12. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0165] Tables 33 to 36 show data for the imaging optical system of Example 9. Table 33 shows the configuration of the optical window W. Table 34 shows construction data for the reflective optical system GR, the refractive optical system GL, and the optical member PP. Table 35 shows specifications for the composite optical system formed by combining the reflective optical system GR and the refractive optical system GL. Table 36 shows the aspherical coefficients of each aspherical surface.

[0166] [Table 33]

[0167] [Table 34]

[0168] [Table 35]

[0169] [Table 36]

[0170] [Example 10] FIG. 22 shows a cross-sectional view of the configuration of the imaging optical system of Example 10 and the light beam. The imaging optical system of Example 10 comprises, in order along the optical path from the magnification side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the magnification side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having power, and a third reflecting surface R3 having positive power. The refractive optical system GL comprises, in order from the magnification side to the reduction side, lenses L1 and L2, an aperture stop St, and lenses L3 to L6. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0171] Tables 37 to 40 show data for the imaging optical system of Example 10. Table 37 shows the configuration of the optical window W. Table 38 shows construction data for the reflective optical system GR, the refractive optical system GL, and the optical member PP. Table 39 shows specifications for the composite optical system formed by combining the reflective optical system GR and the refractive optical system GL. Table 40 shows the aspherical coefficients of each aspherical surface.

[0172] [Table 37]

[0173] [Table 38]

[0174] [Table 39]

[0175] [Table 40]

[0176] [Example 11] FIG. 23 shows a cross-sectional view of the configuration of the imaging optical system of Example 11 and the light beam. The imaging optical system of Example 11 comprises, in order along the optical path from the magnification side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the magnification side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having power, and a third reflecting surface R3 having positive power. The refractive optical system GL comprises, in order from the magnification side to the reduction side, lenses L1 to L2, an aperture stop St, and lenses L3 to L6. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0177] Tables 41 to 44 show data for the imaging optical system of Example 11. Table 41 shows the configuration of each optical window W. Table 42 shows construction data for the reflective optical system GR, the refractive optical system GL, and the optical member PP. Table 43 shows specifications for the composite optical system formed by combining the reflective optical system GR and the refractive optical system GL. Table 44 shows the aspherical coefficients of each aspherical surface.

[0178] [Table 41]

[0179] [Table 42]

[0180] [Table 43]

[0181] [Table 44]

[0182] [Example 12] FIG. 24 shows a cross-sectional view of the configuration and light beam of the imaging optical system of Example 12. The imaging optical system of Example 12 comprises, in order along the optical path from the magnification side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the magnification side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having positive power, and a third reflecting surface R3 having positive power. The first reflecting surface R1 and the third reflecting surface R3 are formed by the same member and have the same surface shape. The refractive optical system GL comprises, in order from the magnification side to the reduction side, lenses L1 and L2, an aperture stop St, and lenses L3 to L5. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0183] Tables 45 to 48 show data for the imaging optical system of Example 12. Table 45 shows the configuration of each optical window W. Table 46 shows construction data for the reflective optical system GR, the refractive optical system GL, and the optical member PP. Table 47 shows specifications for the composite optical system formed by combining the reflective optical system GR and the refractive optical system GL. Table 48 shows the aspherical coefficients of each aspherical surface.

[0184] [Table 45]

[0185] [Table 46]

[0186] [Table 47]

[0187] [Table 48]

[0188] [Example 13] FIG. 25 shows a cross-sectional view of the configuration and light beam of the imaging optical system of Example 13. The imaging optical system of Example 13 comprises, in order along the optical path from the magnification side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the magnification side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having positive power, and a third reflecting surface R3 having positive power. The first reflecting surface R1 and the third reflecting surface R3 are formed by the same member and have the same surface shape. The refractive optical system GL comprises, in order from the magnification side to the reduction side, lenses L1 and L2, an aperture stop St, and lenses L3 to L5. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0189] Tables 49 to 52 show data for the imaging optical system of Example 13. Table 49 shows the configuration of each optical window W. Table 50 shows construction data for the reflective optical system GR, the refractive optical system GL, and the optical member PP. Table 51 shows specifications for the composite optical system formed by combining the reflective optical system GR and the refractive optical system GL. Table 52 shows the aspherical coefficients of each aspherical surface.

[0190] [Table 49]

[0191] [Table 50]

[0192] [Table 51]

[0193] [Table 52]

[0194] [Example 14] FIG. 26 shows a cross-sectional view of the configuration and light beam of the imaging optical system of Example 14. The imaging optical system of Example 14 comprises, in order along the optical path from the magnification side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the magnification side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having positive power, and a third reflecting surface R3 having positive power. The first reflecting surface R1 and the third reflecting surface R3 are formed of the same member and have the same surface shape. The refractive optical system GL comprises, in order from the magnification side to the reduction side, lenses L1 to L5, an aperture stop St, and lenses L6 to L10. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0195] Tables 53 to 56 show data for the imaging optical system of Example 14. Table 53 lists the configuration of the optical window W. The "origin of the curved surface equation" in Table 53 is the origin used in the equation defining the curved surface of the optical window W, and Table 53 shows the position of this origin relative to the intersection of the first reflecting surface R1 and the optical axis AX. The "normal direction" in Table 53 indicates the normal direction to the center of curvature of the surface on the enlargement side of the optical window W. Table 54 lists construction data for the imaging optical system, including the optical window W, and the optical member PP. Table 55 lists specifications for the imaging optical system, including the optical window W. Table 56 lists the aspherical coefficients of each aspheric surface.

[0196] [Table 53]

[0197] [Table 54]

[0198] [Table 55]

[0199] [Table 56]

[0200] [Example 15] FIG. 27 shows a cross-sectional view of the configuration and light beam of the imaging optical system of Example 15. The imaging optical system of Example 15 comprises, in order along the optical path from the magnification side to the reduction side, an optical window W, a reflective optical system GR, and a refractive optical system GL. The reflective optical system GR comprises, in order along the optical path from the magnification side to the reduction side, a first reflecting surface R1 having positive power, a second reflecting surface R2 having positive power, and a third reflecting surface R3 having positive power. The first reflecting surface R1 and the third reflecting surface R3 are formed by the same member and have the same surface shape. The refractive optical system GL comprises, in order from the magnification side to the reduction side, lenses L1 to L7, an aperture stop St, and lenses L8 to L11. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3. A second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0201] Tables 57 to 60 show data for the imaging optical system of Example 15. Table 57 lists the configuration of the optical window W. The "origin of the curved surface equation" in Table 57 is the origin used in the equation defining the curved surface of the optical window W, and Table 57 shows the position of this origin relative to the intersection of the first reflecting surface R1 and the optical axis AX. The "normal direction" in Table 57 indicates the normal direction to the center of curvature of the magnification-side surface of the optical window W. Table 58 lists construction data for the imaging optical system, including the optical window W, and the optical member PP. Table 59 lists specifications for the imaging optical system, including the optical window W. Table 60 lists the aspherical coefficients of each aspheric surface.

[0202] [Table 57]

[0203] [Table 58]

[0204] [Table 59]

[0205] [Table 60]

[0206] [Variations] FIG. 28 shows a modified example in which the imaging optical system of the fifteenth embodiment shown in FIG.

[0207] Table 61 shows various data related to the image displayed on the display surface 2a in Examples 1 to 15. In all Examples, the long side direction is the X-axis direction, and the short side direction is the Y-axis direction. In Table 61, the "inch size" row shows the diagonal length of the image in inches. "ImL," "ImS," "Δs," and "V" are used in the above conditional expressions. "[mm]" indicates that the unit is millimeters. The "projection size" row shows the diagonal length of the projected enlarged image in inches. In Examples 1 to 4 and Examples 8 to 15, the relative positions of the imaging optical system 1 and the display element 2 are fixed, but in Examples 5 to 7, the imaging optical system 1 and the display element 2 are configured to be relatively movable in a direction perpendicular to the optical axis AX.

[0208] [Table 61] JPEG2025167290000063.jpg43145 JPEG2025167290000064.jpg44120

[0209] Tables 62 to 66 show the corresponding values ​​of conditional expressions (1) to (12) for the imaging optical systems of Examples 1 to 15. In Tables 62 to 66, the values ​​used in calculating the corresponding values ​​of conditional expressions (4), (5), (7), and (10) are shown below the corresponding values. All lengths shown in Tables 62 to 66 are in mm (millimeters). The corresponding values ​​of the Examples shown in Tables 62 to 66 may be used as the upper or lower limits of the conditional expressions to set preferred ranges for the conditional expressions.

[0210] [Table 62]

[0211] [Table 63]

[0212] [Table 64]

[0213] [Table 65]

[0214] [Table 66]

[0215] Next, a projection display device according to an embodiment of the present disclosure will be described. FIG. 29 is a schematic diagram illustrating the configuration of a projection display device according to an embodiment of the present disclosure. The projection display device 100 shown in FIG. 29 includes an imaging optical system 10 according to an embodiment of the present disclosure, a light source 15, and transmissive display elements 11a-11c as light valves that output optical images corresponding to the respective color lights. The projection display device 100 also includes dichroic mirrors 12 and 13 for color separation, a cross dichroic prism 14 for color synthesis, condenser lenses 16a-16c, and total reflection mirrors 18a-18c for deflecting the optical path. Note that FIG. 29 only illustrates the imaging optical system 10. An integrator is disposed between the light source 15 and the dichroic mirror 12, but is not shown in FIG. 29.

[0216] White light from light source 15 is separated into three colored light beams (green light, blue light, and red light) by dichroic mirrors 12 and 13, and then passes through condenser lenses 16a to 16c, where the colored light beams are incident on transmissive display elements 11a to 11c corresponding to the colored light beams and modulated there. After being color-synthesized by cross dichroic prism 14, the colored light beams are incident on imaging optical system 10. Imaging optical system 10 projects an optical image based on the modulated light by transmissive display elements 11a to 11c onto screen 105.

[0217] FIG. 30 is a schematic diagram of a projection display device according to another embodiment of the present disclosure. The projection display device 200 shown in FIG. 30 includes an imaging optical system 210 according to an embodiment of the present disclosure, a light source 215, and DMD (Digital Micromirror Device: registered trademark) elements 21a-21c as light valves that output optical images corresponding to the respective color lights. The projection display device 200 also includes TIR (Total Internal Reflection) prisms 24a-24c for color separation and color synthesis, and a polarization separation prism 25 that separates illumination light and projection light. Note that FIG. 30 only shows a schematic representation of the imaging optical system 210. An integrator is disposed between the light source 215 and the polarization separation prism 25, but is not shown in FIG. 30.

[0218] White light from light source 215 is reflected by a reflective surface inside polarization splitter prism 25, and then separated into three colored light beams (green light, blue light, and red light) by TIR prisms 24a-24c. Each separated colored light beam enters and is modulated by the corresponding DMD elements 21a-21c, travels again in the opposite direction through TIR prisms 24a-24c, and is color-synthesized. Then, it passes through polarization splitter prism 25 and enters imaging optical system 210. Imaging optical system 210 projects an optical image based on the modulated light by DMD elements 21a-21c onto screen 205.

[0219] Fig. 31 is a schematic diagram of a projection display device according to yet another embodiment of the present disclosure. The projection display device 300 shown in Fig. 31 includes an imaging optical system 310 according to an embodiment of the present disclosure, a light source 315, reflective display elements 31a-31c as light valves corresponding to the respective colors of light, dichroic mirrors 32 and 33 for color separation, a cross dichroic prism 34 for color synthesis, a total reflection mirror 38 for optical path deflection, and polarization separation prisms 35a-35c. Note that Fig. 31 only shows the imaging optical system 310 in a simplified manner. An integrator is disposed between the light source 315 and the dichroic mirror 32, but is not shown in Fig. 31.

[0220] White light from light source 315 is separated into three colored light beams (green light, blue light, and red light) by dichroic mirrors 32 and 33. Each separated colored light beam passes through polarization separation prisms 35a to 35c, enters and is modulated by reflective display elements 31a to 31c corresponding to the colored light beam, and is then color-synthesized by cross dichroic prism 34 before entering imaging optical system 310. Imaging optical system 310 projects an optical image based on the modulated light by reflective display elements 31a to 31c onto screen 305.

[0221] Fig. 32 is a schematic diagram of a projection display device according to yet another embodiment of the present disclosure. The projection display device 400 shown in Fig. 32 includes an imaging optical system 46 according to an embodiment of the present disclosure, a light source 41, and a DMD element 44 as a light valve that outputs an optical image corresponding to each color light. The projection display device 400 also includes a color wheel 42, a light-guiding optical system 43, and a TIR prism 45. Note that Fig. 32 shows the imaging optical system 46 only in a simplified manner.

[0222] Color wheel 42 has three color filters (green, blue, and red) arranged on its circumference, and as color wheel 42 rotates, the filters of each color are inserted sequentially into the optical path. White light from light source 41 is time-divided into three colored light beams (green light, blue light, and red light) by entering the rotating color wheel 42. After time division, each colored light beam passes through light-guiding optical system 43 and TIR prism 45, then enters DMD element 44 and is modulated, and passes through TIR prism 45 again before entering imaging optical system 46. Imaging optical system 46 projects an optical image based on the modulated light by DMD element 44 onto screen 405.

[0223] 33 and 34 are external views of a camera 800, which is an imaging device according to an embodiment of the present disclosure. Fig. 33 shows a perspective view of the camera 800 as seen from the front side, and Fig. 34 shows a perspective view of the camera 800 as seen from the rear side. The camera 800 is a so-called mirrorless digital camera, to which an interchangeable lens 820 can be removably attached. The interchangeable lens 820 is configured to include an imaging optical system 801 according to an embodiment of the present disclosure housed in a lens barrel.

[0224] Camera 800 includes camera body 831. A shutter button 832 and a power button 833 are provided on the top surface of camera body 831. An operation unit 834, an operation unit 835, and a display unit 836 are provided on the back surface of camera body 831. Display unit 836 displays a captured image and an image within the angle of view before capture.

[0225] A photographic opening through which light from the subject to be photographed enters is provided in the center of the front of camera body 831, and a mount 837 is provided at a position corresponding to the photographic opening, and interchangeable lens 820 is attached to camera body 831 via mount 837.

[0226] An imaging element 838 is provided within the camera body 831. The imaging element 838 outputs an imaging signal corresponding to the subject image formed by the interchangeable lens 820. For example, a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) is used as the imaging element 838. A signal processing circuit (not shown), a recording medium (not shown), and the like are provided within the camera body 831. The signal processing circuit processes the imaging signal output from the imaging element 838 to generate an image. The recording medium is for recording the generated image. With the camera 800, it is possible to take a still image or a video by pressing the shutter button 832, and the image data obtained by this shooting is recorded on the recording medium.

[0227] Although the technology of the present disclosure has been described above using embodiments and examples, the technology of the present disclosure is not limited to the above embodiments and examples and can be modified in various ways. The radius of curvature of each reflecting surface, as well as the radius of curvature, surface spacing, refractive index, Abbe number, aspherical coefficient, etc. of each lens are not limited to the values ​​shown in the above examples and may take other values.

[0228] Furthermore, the projection display device according to the technology of the present disclosure is not limited to the above configuration. For example, the optical members and light valves used for light beam separation or light beam combination can be modified in various ways. The light valve is not limited to a configuration in which light from a light source is spatially modulated by an image display element and output as an optical image based on image data, but may be a configuration in which light output from a self-luminous image display element itself is output as an optical image based on image data. Examples of self-luminous image display elements include image display elements in which light-emitting elements such as LEDs (Light Emitting Diodes) or OLEDs (Organic Light Emitting Diodes) are two-dimensionally arranged.

[0229] Furthermore, the imaging device according to the technology of the present disclosure is not limited to the above configuration, but can take various forms, such as cameras other than mirrorless cameras, film cameras, video cameras, security cameras, and cinema cameras.

[0230] The following additional notes are provided regarding the above embodiments and examples. [Appendix 1] An imaging optical system capable of forming an enlarged image on an enlargement-side imaging plane by enlarging an image on a reduction-side imaging plane, The optical system comprises, in order from the magnification side to the reduction side along the optical path, an optical window, a reflective optical system, and a refractive optical system including a plurality of lenses, the reflective optical system includes, in order from the enlargement side to the reduction side along the optical path, a first reflecting surface having positive power, a second reflecting surface having power, and a third reflecting surface having positive power; a first intermediate image is formed on the optical path on the reduction side of the third reflecting surface and at a position conjugate with the image; a second intermediate image is formed in the reflecting optical system at a position conjugate with the first intermediate image; the magnified image is formed on the optical path on the magnification side of the optical window and at a position conjugate with the second intermediate image, the center of the magnified image is at a position shifted in a direction perpendicular to the optical axis of the refractive optical system, a central principal ray is defined as a chief ray incident on the center of the magnified image when the amount of the shift is maximum; The angle of incidence of the central chief ray on the magnification-side image plane is α, When the angle of incidence of the central chief ray on the optical window is θc, 40°<|α|<85° (1) 0°<|θc|<35° (2) An imaging optical system that satisfies conditional expressions (1) and (2) expressed as follows: [Appendix 2] If the maximum half angle of view on the magnification side is ω, 65°<ω<90° (3) 10. The imaging optical system according to claim 1, which satisfies conditional expression (3) shown below. [Appendix 3] 3. The imaging optical system according to claim 1, wherein the intersection of the central chief ray and the enlargement-side surface of the optical window is located closer to the third reflecting surface than the entire second reflecting surface in the direction of the optical axis. [Appendix 4] 4. The imaging optical system according to claim 1, wherein the entire optical window is located closer to the third reflecting surface than the point of the refractive optical system that is located on the most magnified side in the direction of the optical axis. [Appendix 5] The distance between the optical axis and the point on the optical window closest to the optical axis is hWmin. When the radius of the lens on the most enlarged side of the refractive optical system is ra, 0.9 <hWmin / ra<3 (4) 5. The imaging optical system according to claim 1, which satisfies conditional expression (4) below. [Appendix 6] the optical window is a flat plate; hWR is the distance between the optical axis and a point of the optical window that is closest to the optical axis among points located on the reflection optical system side in the direction of the optical axis, and the optical axis; When the distance between the optical axis and the point farthest from the optical axis among the points within the effective area of ​​the third reflecting surface is hM3, 0.5 <hWR / hM3<3 (5) 6. The imaging optical system according to claim 1, which satisfies conditional expression (5) below. [Appendix 7] the optical window is a flat plate; When the inclination angle of the optical window with respect to a plane perpendicular to the optical axis is θwin, 30°<θwin<85° (6) 7. The imaging optical system according to claim 1, which satisfies conditional expression (6) below. [Appendix 8] the optical window is a flat plate; The distance between the center of the image and the optical axis is Δs. The length of the short side of the image is ImS, The minimum value of V defined by V = Δs / ImS is Vmin. The length of the long side of the rectangle circumscribing the optical window is WL, The distance from the first reflecting surface to the magnified image in the direction of the optical axis is Dsc, The length of the long side of the enlarged image is PrL, If the length of the long side of the image is ImL, 0<(Vmin-0.5)×WL×(Dsc / PrL) / ImL<1.2 (7) 8. The imaging optical system according to claim 1, which satisfies conditional expression (7) below. [Appendix 9] the optical window is a flat plate; The length of the long side of the rectangle circumscribing the optical window is WL, If the length of the short side of the rectangle is WS, 2 <WL / WS<10 (8) 9. The imaging optical system according to claim 1, which satisfies conditional expression (8) below. [Appendix 10] the optical window is a flat plate; The distance between the center of the image and the optical axis is Δs. The length of the short side of the image is ImS, The minimum value of V defined by V = Δs / ImS is Vmin. The length of the long side of the rectangle circumscribing the optical window is WL, If the length of the short side of the rectangle is WS, 0.5<(Vmin-0.5)×WL / WS<1.5 (9) 10. The imaging optical system according to claim 1, which satisfies conditional expression (9) below. [Appendix 11] 6. The imaging optical system according to claim 1, wherein the optical window has a curvature in a long-side direction of the image. [Appendix 12] WpL is the length of the long side of the projection of a rectangle circumscribing the optical window onto a plane perpendicular to the direction from the center of curvature to the origin used in the equation defining the curved surface of the optical window; If the length of the short side of the projection is WpS, 1 <WpL / WpS<3 (10) 12. The imaging optical system according to claim 11, which satisfies conditional expression (10) expressed as follows: [Appendix 13] 13. The imaging optical system according to claim 11, wherein the optical window is a cylindrical lens. [Appendix 14] the surface of the optical window on the reduction side is a cylindrical surface, WpL is the length of the long side of the projection of a rectangle circumscribing the optical window onto a plane perpendicular to the direction from the center of curvature to the origin used in the equation defining the curved surface of the optical window; When the radius of curvature of the cylindrical surface in a direction perpendicular to the generating line of the cylindrical surface is Rcy, 1 <WpL / Rcy<2 (11) 14. The imaging optical system according to claim 13, which satisfies conditional expression (11) shown below. [Appendix 15] the surface of the optical window on the reduction side is a cylindrical surface, The composite focal length of the reflective optical system and the refractive optical system is fRL. When the radius of curvature of the cylindrical surface in a direction perpendicular to the generating line of the cylindrical surface is Rcy, 0 <fRL / Rcy<0.1 (12) 15. The imaging optical system according to claim 13, which satisfies conditional expression (12) shown below. [Appendix 16] 13. The imaging optical system according to claim 11, wherein the optical window has a toric shape. [Appendix 17] 13. The imaging optical system according to claim 11, wherein the surface of the optical window on the enlargement side and the surface of the optical window on the reduction side are spherical. [Appendix 18] 13. The imaging optical system according to claim 11, wherein the optical window has an aspherical shape. [Appendix 19] A projection display device comprising the imaging optical system according to any one of Supplementary Note 1 to Supplementary Note 18. [Appendix 20] An imaging device comprising the imaging optical system according to any one of Supplementary Note 1 to Supplementary Note 18. [Explanation of symbols]

[0231] 1 Imaging optical system 2. Display element 2a Display surface 3 Projection display device 4 images 4c center 6 Enlarged image 6a point 6b points 6c center 9. Cabinet 10 Imaging optical system 11a to 11c Transmissive display element 12 Dichroic mirror 13 Dichroic mirror 14 Cross dichroic prism 15 light source 16a~16c Condenser Lens 18a~18c Total reflection mirror 21a~21c DMD elements 24a~24c TIR Prism 25 Polarization separation prism 31a to 31c reflective display elements 32 Dichroic mirror 33 Dichroic mirror 34 Cross Dichroic Prism 35a~35c Polarization separation prism 38 Total Reflection Mirror 41 Light source 42 Color Wheel 43 Light guiding optical system 44 DMD elements 45 TIR Prism 46 Imaging Optical System 100 Projection display device 105 screens 200 Projection display device 205 screens 210 Imaging Optical System 215 Light source 300 Projection display device 305 screens 310 Imaging Optical System 315 Light source 400 Projection display device 405 screens 800 cameras 801 Imaging Optical System 820 Interchangeable Lens 831 Camera Body 832 shutter button 833 Power button 834 Operation section 835 Operation section 836 Display section 837 Mount 838 Image sensor AX optical axis Cray central chief ray Dsc distance GL refractive optical system GR reflective optical system hM3 distance hWR distance hWmin distance IC Image Circle ImL length ImS length L1~L14 lenses LF1 Luminous flux cross section LF2 Luminous flux cross section LF3 Luminous flux cross section LFa luminous flux LFb Luminous flux LFc Luminous flux M1 1st intermediate image M2 2nd intermediate image P1 intersection P2 point PP optical components PrL length R1 1st reflective surface R2 2nd reflective surface R3 3rd reflective surface ra radius RecW1 rectangle RecW3 rectangle RecW4 rectangle Scr Screen St aperture stop W Optical window W1 optical window W2 optical window W3 optical window W4 optical window W5 optical window W5p Projection WL length WpL Length WpS Length WS Length α angle of incidence θc incidence angle θwin Tilt angle Δs shift amount ω Maximum half angle of view

Claims

1. An imaging optical system capable of forming an enlarged image on an enlargement-side imaging plane by enlarging an image on a reduction-side imaging plane, The optical system comprises, in order from the magnification side to the reduction side along the optical path, an optical window, a reflective optical system, and a refractive optical system including a plurality of lenses, the reflective optical system includes, in order from the enlargement side to the reduction side along the optical path, a first reflecting surface having positive power, a second reflecting surface having power, and a third reflecting surface having positive power; a first intermediate image is formed on the optical path on the reduction side of the third reflecting surface and at a position conjugate with the image; a second intermediate image is formed in the reflection optical system at a position conjugate with the first intermediate image; the magnified image is formed on the optical path on the magnification side of the optical window and at a position conjugate with the second intermediate image, the center of the magnified image is at a position shifted in a direction perpendicular to the optical axis of the refractive optical system, a central principal ray is defined as a chief ray incident on the center of the magnified image when the amount of the shift is maximum; The angle of incidence of the central chief ray on the magnification-side image plane is α, When the angle of incidence of the central chief ray on the optical window is θc, ４０°＜｜α｜＜８５° （１） 0°<|θc|<35° (2) An imaging optical system that satisfies the conditions (1) and (2) expressed by the following formulas.

2. If the maximum half angle of view on the magnification side is ω, 65°<ω<90° (3) 2. The imaging optical system according to claim 1, which satisfies conditional expression (3) expressed as follows:

3. 2. The imaging optical system according to claim 1, wherein an intersection of the central chief ray and the enlargement-side surface of the optical window is located closer to the third reflecting surface than the entire second reflecting surface in the direction of the optical axis.

4. 2. The imaging optical system according to claim 1, wherein the entire optical window is located closer to the third reflecting surface than a point of the refractive optical system that is located on the most magnifying side in the direction of the optical axis.

5. The distance between the optical axis and the point on the optical window closest to the optical axis is hWmin, When the radius of the lens on the most enlarged side of the refractive optical system is ra, 0.9<hWmin / ra<3 (4) 2. The imaging optical system according to claim 1, which satisfies conditional expression (4) expressed as follows:

6. the optical window is a flat plate; hWR is the distance between the optical axis and a point of the optical window that is closest to the optical axis among points located on the reflection optical system side in the direction of the optical axis, and When the distance between the optical axis and the point farthest from the optical axis among the points within the effective area of ​​the third reflecting surface is hM3, 0.5<hWR / hM3<3 (5) 2. The imaging optical system according to claim 1, which satisfies conditional expression (5) expressed as follows:

7. the optical window is a flat plate; When the inclination angle of the optical window with respect to a plane perpendicular to the optical axis is θwin, 30°<θwin<85° (6) 2. The imaging optical system according to claim 1, which satisfies conditional expression (6) expressed as follows:

8. the optical window is a flat plate; The distance between the center of the image and the optical axis is Δs. The length of the short side of the image is ImS, The minimum value of V defined by V = Δs / ImS is Vmin, The length of the long side of the rectangle circumscribing the optical window is WL, The distance from the first reflecting surface to the magnified image in the optical axis direction is Dsc, The length of the long side of the enlarged image is PrL, If the length of the long side of the image is ImL, 0<(Vmin-0.5)×WL×(Dsc / PrL) / ImL<1.2 (7) 2. The imaging optical system according to claim 1, which satisfies conditional expression (7) expressed as follows:

9. the optical window is a flat plate; The length of the long side of the rectangle circumscribing the optical window is WL, If the length of the short side of the rectangle is WS, 2<WL / WS<10 (8) 2. The imaging optical system according to claim 1, which satisfies conditional expression (8) expressed as follows:

10. the optical window is a flat plate; The distance between the center of the image and the optical axis is Δs. The length of the short side of the image is ImS, The minimum value of V defined by V = Δs / ImS is Vmin, The length of the long side of the rectangle circumscribing the optical window is WL, If the length of the short side of the rectangle is WS, 0.5<(Vmin-0.5)×WL / WS<1.5 (9) 2. The imaging optical system according to claim 1, which satisfies conditional expression (9) expressed as follows:

11. The imaging optical system according to claim 1 , wherein the optical window has a curvature in the direction of a long side of the image.

12. WpL is the length of the long side of the projection of a rectangle circumscribing the optical window onto a plane perpendicular to the direction from the center of curvature toward the origin used in the equation defining the curved surface of the optical window; If the length of the short side of the projection is WpS, 1<WpL / WpS<3 (10) 12. The imaging optical system according to claim 11, which satisfies conditional expression (10) expressed as follows:

13. The imaging optical system according to claim 11, wherein the optical window is a cylindrical lens.

14. the surface of the optical window on the reduction side is a cylindrical surface, WpL is the length of the long side of the projection of a rectangle circumscribing the optical window onto a plane perpendicular to the direction from the center of curvature toward the origin used in the equation defining the curved surface of the optical window; When the radius of curvature of the cylindrical surface in a direction perpendicular to the generating line of the cylindrical surface is Rcy, 1<WpL / Rcy<2 (11) 14. The imaging optical system according to claim 13, which satisfies conditional expression (11) expressed as follows:

15. the surface of the optical window on the reduction side is a cylindrical surface, The composite focal length of the reflective optical system and the refractive optical system is fRL, When the radius of curvature of the cylindrical surface in a direction perpendicular to the generating line of the cylindrical surface is Rcy, 0<fRL / Rcy<0.1 (12) 14. The imaging optical system according to claim 13, which satisfies conditional expression (12) expressed as follows:

16. The imaging optical system of claim 11 , wherein the optical window has a toric shape.

17. The imaging optical system according to claim 11 , wherein the surface on the enlargement side of the optical window and the surface on the reduction side of the optical window are spherical.

18. The imaging optical system of claim 11 , wherein the optical window has an aspherical shape.

19. A projection display device comprising the imaging optical system according to any one of claims 1 to 18.

20. An imaging device comprising the imaging optical system according to any one of claims 1 to 18.

Images