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

Abstract

To provide a compact, wide-angle imaging optical system, 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 disclosed herein consists of 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. 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. A first intermediate image is formed between the third reflective surface and the refractive optical system at a position conjugate with a reduction-side imaging plane, and a second intermediate image is formed within the reflective optical system at a position conjugate with the first intermediate image. There are just two intermediate images formed on the magnification side of the refractive optical system. The imaging optical system satisfies the following conditional expression regarding the maximum half view angle ω on the magnification side: 4.6<tanω<50.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] BACKGROUND ART Conventionally, imaging optical systems that can be used in projection display devices, imaging devices, and the like are known from the following Patent Documents 1 and 2. [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] There is a demand for an imaging optical system that is compact yet has a wide angle of view, and the level of these requirements is increasing year by year.

[0005] The present disclosure provides an imaging optical system that is compact yet has a wide angle of view, 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]

[0006] An imaging optical system according to one embodiment of the present disclosure comprises, in order along an optical path from the enlargement side to the reduction side, 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 between the third reflecting surface and the refractive optical system at a position conjugate with the reduction-side image forming surface, a second intermediate image is formed within the reflective optical system at a position conjugate with the first intermediate image, and the intermediate images formed on the enlargement side of the refractive optical system are only the first intermediate image and the second intermediate image, 4.6 <tanω<50 (1) Here, the maximum half angle of view on the enlargement side is set to ω.

[0007] When the magnification of the imaging optical system is β, the distance on the optical axis from the first reflecting surface to the enlargement-side image-forming surface is D0, and the distance on the optical axis from the first reflecting surface to the reduction-side image-forming surface is d, the imaging optical system of the above aspect has the following characteristics: 77.5<|β×d / D0|<200 (2) It is preferable to satisfy conditional expression (2) below.

[0008] When the distance between the optical axis and the reflection point on the first reflecting surface that is the longest from the optical axis is RM1, the distance between the optical axis and the reflection point on the second reflecting surface that is the longest from the optical axis is RM2, the distance between the optical axis and the reflection point on the third reflecting surface that is the longest from the optical axis is RM3, and the maximum image height on the reduction-side image forming surface is Y, the imaging optical system of the above aspect is as follows: 10<(RM1+RM2+RM3) / Y<25 (3) It is preferable to satisfy conditional expression (3) below.

[0009] When the distance between the optical axis and the reflection point of the light beam on the first reflecting surface that is the farthest from the optical axis is defined as RM1, and the distance on the optical axis from the first reflecting surface to the reduction-side image forming surface is defined as d, the imaging optical system of the above aspect is as follows: 0.1 <RM1 / d<0.5 (4) It is preferable to satisfy conditional expression (4) below.

[0010] When the distance between the optical axis and the reflection point of the light beam on the third reflecting surface that is the farthest from the optical axis is defined as RM3, and the distance on the optical axis from the first reflecting surface to the reduction-side image forming surface is defined as d, the imaging optical system of the above aspect is as follows: 0.1 <RM3 / d<0.4 (5) It is preferable to satisfy conditional expression (5) below.

[0011] The refractive optical system preferably includes three or more negative lenses, and more preferably includes four or more negative lenses.

[0012] It is preferable that a second intermediate image is formed on the optical path between the first reflecting surface and the second reflecting surface.

[0013] When the focal length of the first reflecting surface is fM1 and the focal length of the third reflecting surface is fM3, the imaging optical system of the above aspect has the following structure: 0.25 <fM1 / fM3<4 (6) It is preferable to satisfy conditional expression (6) below.

[0014] The first and third reflecting surfaces may be formed on the same member and may have the same surface shape.

[0015] When the distance on the optical axis between the first reflecting surface and the second reflecting surface is dM1M2 and the distance on the optical axis from the first reflecting surface to the reduction-side image forming surface is d, the imaging optical system of the above aspect has the following characteristics: 0.2<|dM1M2| / d<0.5 (7) It is preferable to satisfy conditional expression (7) below.

[0016] The lens closest to the reduction side of the refractive optical system has a positive power, and when the Abbe number of the lens closest to the reduction side of the refractive optical system based on the d-line is νp, the imaging optical system of the above aspect has the following: 40<νp<100 (8) It is preferable to satisfy conditional expression (8) below.

[0017] It is preferable that the lens closest to the reduction side of the refractive optical system has an aspherical lens surface.

[0018] At least one of the lens closest to the magnification side of the refractive optical system and the lens second from the magnification side of the refractive optical system is preferably a first negative lens having negative power, and the first negative lens preferably has an aspherical lens surface.

[0019] The refractive optical system may be configured to include six or fewer lenses, or ten or more lenses.

[0020] Another aspect of the present disclosure is a projection display device including the imaging optical system of the above aspect.

[0021] Yet another aspect of the present disclosure is an imaging device including the imaging optical system of the above aspect.

[0022] 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.

[0023] Unless otherwise specified, the sign of the power and the surface shape of optical elements, including aspherical surfaces, are considered in the paraxial region. The "focal length" used in the conditional expressions is the paraxial focal length. The "distance on the optical axis" used in the conditional expressions is the geometric distance, unless otherwise specified.

[0024] The terms "d-line," "C-line," and "F-line" used in this specification are emission lines, and the wavelength of the d-line is treated as 587.56 nm (nanometers), the wavelength of the C-line as 656.27 nm (nanometers), and the wavelength of the F-line as 486.13 nm (nanometers). [Effects of the Invention]

[0025] According to the present disclosure, it is possible to provide an imaging optical system that is compact yet has a wide angle of view, a projection display device that includes this imaging optical system, and an imaging device that includes this imaging optical system. [Brief explanation of the drawings]

[0026] [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] FIG. 10 is a diagram for explaining symbols in a conditional expression. [Figure 3] 3A to 3C are diagrams showing various aberrations in the imaging optical system of Example 1. [Figure 4] 10 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a second embodiment. [Figure 5] 10A to 10C are diagrams showing various aberrations of the imaging optical system of Example 2. [Figure 6] 10 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a third embodiment. [Figure 7] 10A to 10C are diagrams showing various aberrations of the imaging optical system of Example 3. [Figure 8] 10 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a fourth embodiment. [Figure 9] 10A to 10C are diagrams showing various aberrations of the imaging optical system of Example 4. [Figure 10] 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 11] 10A to 10C are diagrams showing various aberrations in the imaging optical system of Example 5. [Figure 12] 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 13] 10A to 10C are diagrams showing various aberrations of the imaging optical system of Example 6. [Figure 14] 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 15] 10A to 10C are diagrams showing various aberrations of the imaging optical system of Example 7. [Figure 16] 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 17]13A to 13C are diagrams showing various aberrations in the imaging optical system of Example 8. [Figure 18] 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 19] 13A to 13C are diagrams showing various aberrations in the imaging optical system of Example 9. [Figure 20] 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 21] 13A to 13C are diagrams showing various aberrations in the imaging optical system of Example 10. [Figure 22] 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 23] 13A to 13C are diagrams showing various aberrations in the imaging optical system of Example 11. [Figure 24] FIG. 22 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a modified example of the eleventh 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 twelfth embodiment. [Figure 26] 16A to 16C are diagrams showing various aberrations in the imaging optical system of Example 12. [Figure 27] 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 28] 13A to 13C are diagrams showing various aberrations in the imaging optical system of Example 13. [Figure 29] 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 30] 20A to 20C are diagrams showing various aberrations in the imaging optical system of Example 14. [Figure 31] 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 32] 20A to 20C are diagrams showing various aberrations in the imaging optical system of Example 15. [Figure 33] 1 is a schematic configuration diagram of a projection display device according to an embodiment. [Figure 34] FIG. 10 is a schematic configuration diagram of a projection display device according to another embodiment. [Figure 35] FIG. 10 is a schematic configuration diagram of a projection display device according to yet another embodiment. [Figure 36] FIG. 10 is a schematic configuration diagram of a projection display device according to yet another embodiment. [Figure 37] 1 is a perspective view of the front side of an imaging device according to an embodiment. [Figure 38] FIG. 38 is a perspective view of the rear side of the imaging device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, embodiments of the technology of the present disclosure will be described with reference to the drawings. Fig. 1 shows a cross-sectional view of the configuration and light beams in a cross section including an optical axis Z of an imaging optical system according to an embodiment of the present disclosure. The configuration example shown in Fig. 1 corresponds to Example 1, which will be described later. Fig. 1 shows a light beam B0 at the minimum angle of view and a light beam B1 at the maximum angle of view as light beams.

[0028] The imaging optical system of the present disclosure 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 of the present disclosure is used as a projection optical system. In the following, to avoid redundant explanation, the "imaging optical system of the present disclosure" may be simply referred to as the "imaging optical system."

[0029] Figure 1 shows an example in which an optical element PP and a light valve display surface Sim are arranged on the reduction side of the imaging optical system, assuming that the imaging optical system will be installed in a projection display device. The optical element PP is a component that is assumed to include a filter, cover glass, color synthesis prism, etc. The optical element PP is a component that does not have power, and a configuration in which the optical element PP is omitted is also possible. The light valve is a display element that outputs an optical image, and this optical image is displayed as an image on the display surface Sim. For example, an image display element such as a liquid crystal display element or a DMD (Digital Micromirror Device: registered trademark) can be used as the light valve.

[0030] The imaging optical system is mounted, for example, on a projection display device and projects an image displayed on a display surface Sim of a reduction-side display element onto a projection surface on an enlargement-side. In a projection display device, a light beam imparted with image information on the display surface Sim is incident on the imaging optical system via an optical member PP, and is then projected onto a screen (see, for example, reference symbol Scr in FIG. 2 ) serving as a projection surface by the imaging optical system. In other words, the display surface Sim and the screen are optically conjugate. The screen is an example of an "enlargement-side image surface" in the present disclosure, and the display surface Sim is an example of a "reduction-side image surface" in the present disclosure. Note that, in this specification, "screen" refers to an object onto which a projection image formed by the imaging optical system is projected. The screen may be, for example, a dedicated screen, or a wall, floor, ceiling, or exterior wall of a room.

[0031] In the explanations herein, the "enlargement side" refers to the screen side on the optical path, and the "reduction side" refers to the display surface Sim side on the optical path. In the explanations herein, 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, "lens A is on the enlargement side of lens B" has the same meaning as "lens A is on the optical path on the enlargement side of lens B." Therefore, in an imaging optical system that forms a folded optical path, "the side closest to the enlargement side" means the side closest to the enlargement side in terms of order on the optical path, and does not mean the side closest to the screen in terms of distance. In the following, to avoid redundant explanations, "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."

[0032] The imaging optical system of the present disclosure comprises, in order along the optical path from the magnification side to the reduction side, a reflective optical system GR and a refractive optical system GL including multiple lenses. The reflective optical system GR includes, 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.

[0033] Since the reflecting surface itself does not generate chromatic aberration, by arranging three reflecting surfaces on the magnification side of the imaging optical system, it is possible to reduce the generation of chromatic aberration in the entire 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 miniaturization.

[0034] 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 L5, an aperture stop St, and lenses L6 to L10. 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 Z. 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 Z.

[0035] In the imaging optical system of Figure 1, a light beam traveling from the display surface Sim 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, and forms a projected image on a screen (not shown in Figure 1).

[0036] The imaging optical system of the present disclosure forms at least two intermediate images, a first intermediate image M1 and a second intermediate image M2, as images conjugate with the image displayed on the display surface Sim. By forming intermediate images, the focal length of the entire system can be shortened, resulting in a configuration suitable for wide-angle viewing. 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.

[0037] The first intermediate image M1 is formed on the optical path between the third reflecting surface R3 and the refractive optical system GL, at a position conjugate with the reduction-side image plane. By not forming the first intermediate image M1 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.

[0038] The second intermediate image M2 is formed within the reflective optical system GR at a position conjugate with the first intermediate image M1. "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.

[0039] 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.

[0040] 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 may be configured to form only two intermediate images, the first intermediate image M1 and the second intermediate image M2.

[0041] 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.

[0042] It is preferable that the first reflecting surface R1 and the third reflecting surface R3 are formed from the same material and 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] It is preferable that the refractive optical system GL includes three or more negative lenses. This is advantageous for correcting various aberrations. If the refractive optical system GL includes four or more negative lenses, this is even more advantageous for correcting various aberrations.

[0045] It is preferable that at least one of the lens closest to the magnification side of the refractive optical system GL and the second lens from the magnification side of the refractive optical system GL is a first negative lens having negative power, which is advantageous for correcting curvature of field that occurs on the reflecting surface.

[0046] It is preferable that the first negative lens has an aspherical lens surface, which is more advantageous for correcting curvature of field that occurs on the reflecting surface.

[0047] It is preferable that the lens closest to the reduction side of the refractive optical system GL has a positive power, which is advantageous for ensuring telecentricity on the reduction side of the imaging optical system.

[0048] It is preferable that the lens closest to the reduction side of the refractive optical system GL has an aspherical lens surface, which is advantageous for suppressing curvature of field.

[0049] It is preferable that the number of lenses included in the refractive optical system GL is six or less, which is advantageous for reducing the size and weight.

[0050] The number of lenses included in the refractive optical system GL is preferably 10 or more, which is advantageous for correcting aberrations when a large display element is used.

[0051] It is preferable that the refractive optical system GL includes a lens set in which adjacent lenses are in contact with each other at least partially. This is advantageous for correcting chromatic aberration. In particular, if the refractive optical system GL includes two or more lens sets in which a lens having positive power and a lens having negative power are in contact with each other at least partially, this is advantageous for correcting various aberrations. Note that the above-mentioned "lens set in which adjacent lenses are in contact with each other at least partially" may be a cemented lens, or may be a so-called edge contact in which only the peripheral portions of the lenses are in contact.

[0052] Next, preferred and possible configurations for the conditional expressions of the imaging optical system of the present disclosure will be described. In the following description of the conditional expressions, in order to avoid redundant explanation, the same symbols will be used for elements with the same definitions, and duplicate explanations of the symbols will be omitted.

[0053] 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 (1): ω is the largest angle between the optical axis Z and the chief ray traveling from the surface of the imaging optical system closest to the enlargement side toward the enlargement-side image plane. By ensuring that the corresponding value of conditional expression (1) is not equal to or smaller than the lower limit, an ultra-wide-angle optical system can be realized. By ensuring that the corresponding value of conditional expression (1) is not equal to or larger than the upper limit, light blocking caused by relatively fine irregularities on the wall surface of the screen can be suppressed. 4.6 <tanω<50 (1)

[0054] In order to obtain better characteristics, it is more preferable to set the lower limit of conditional expression (1) to 4.8, and even more preferable to set it to 5.

[0055] Fig. 2 shows a cross-sectional view of the imaging optical system of Fig. 1, including the optical axis Z, and shows the maximum half angle of view ω as an example. In Fig. 2, the screen Scr is shown, but the reference numerals of the intermediate images and lenses are omitted.

[0056] It is preferable that the imaging optical system satisfy the following conditional expression (2). Here, the magnification of the imaging optical system is defined as β. The distance on the optical axis from the first reflecting surface R1 to the magnification-side imaging surface is defined as D0. The distance on the optical axis from the first reflecting surface R1 to the reduction-side imaging surface is defined as d. Note that β represents the horizontal magnification, not the vertical magnification. As an example, Figure 2 shows the above distances D0 and d. Projection with a wide angle of view is possible by ensuring that the corresponding value of conditional expression (2) is not equal to or smaller than the lower limit. Making sure that the corresponding value of conditional expression (2) is not equal to or larger than the upper limit is advantageous for shortening the overall length. 77.5<|β×d / D0|<200 (2)

[0057] In order to obtain better characteristics, the lower limit of conditional expression (2) should preferably be set to 80, and more preferably to 82.5. In order to obtain better characteristics, the upper limit of conditional expression (2) should preferably be set to 175, and even more preferably to 150.

[0058] In the example of Fig. 1, there is an intersection between first reflecting surface R1 and optical axis Z, but in cases where there is no intersection between first reflecting surface R1 and optical axis Z, unlike the example of Fig. 1, the distance d is determined as follows: Consider an imaginary surface that extends the shape of first reflecting surface R1 to optical axis Z based on the design data for the shape of first reflecting surface R1, and determine the intersection of this imaginary surface and optical axis Z as the end point of distance d on the first reflecting surface side.

[0059] It is preferable that the imaging optical system satisfy the following conditional expression (3). Here, RM1 is the distance between the optical axis Z and the reflection point on the first reflecting surface that is the longest from the optical axis Z. RM2 is the distance between the optical axis Z and the reflection point on the second reflecting surface that is the longest from the optical axis Z. RM3 is the distance between the optical axis Z and the reflection point on the third reflecting surface that is the longest from the optical axis Z. Y is the maximum image height at the reduction-side imaging surface. The above "light rays" regarding RM1, RM2, and RM3 refer to light rays used for imaging on the magnification-side imaging surface or reduction-side imaging surface. As an example, Figure 2 shows the above distances RM1, RM2, RM3, and the maximum image height Y. Ensuring that the corresponding value of conditional expression (3) is not less than the lower limit is advantageous for widening the angle of view. By ensuring that the value corresponding to conditional expression (3) is not greater than the upper limit, it is advantageous for miniaturization. 10<(RM1+RM2+RM3) / Y<25 (3)

[0060] In order to obtain better characteristics, the lower limit of conditional expression (3) should preferably be set to 11, and more preferably to 12. In order to obtain better characteristics, the upper limit of conditional expression (3) should preferably be set to 22.5, and even more preferably to 20.

[0061] It is preferable that the imaging optical system satisfy the following conditional expression (4): By ensuring that the corresponding value of conditional expression (4) is not equal to or less than the lower limit, it is advantageous for achieving a wider angle of view. By ensuring that the corresponding value of conditional expression (4) is not equal to or greater than the upper limit, it is possible to prevent the size of the optical system from increasing in size in the direction perpendicular to the optical axis Z. 0.1 <RM1 / d<0.5 (4)

[0062] To obtain better characteristics, the lower limit of conditional expression (4) should preferably be set to 0.15, and more preferably to 0.2, and the upper limit of conditional expression (4) should preferably be set to 0.45, and even more preferably to 0.4.

[0063] It is preferable that the imaging optical system satisfy the following conditional expression (5): By ensuring that the value corresponding to conditional expression (5) is not equal to or smaller than the lower limit, it is advantageous for achieving a wider angle of view. By ensuring that the value corresponding to conditional expression (5) is not equal to or larger than the upper limit, it is possible to prevent the size of the optical system from increasing in size in the direction perpendicular to the optical axis Z. 0.1 <RM3 / d<0.4 (5)

[0064] To obtain better characteristics, the lower limit of conditional expression (5) should preferably be set to 0.15, and more preferably to 0.2. To obtain better characteristics, the upper limit of conditional expression (5) should preferably be set to 0.35.

[0065] When the focal length of the first reflecting surface R1 is fM1 and the focal length of the third reflecting surface R3 is fM3, it is preferable that the imaging optical system satisfy the following conditional expression (6): By ensuring that the corresponding value of conditional expression (6) is not equal to or less than the lower limit, the curvature of the third reflecting surface R3 can be made small, so that the distance between the second reflecting surface R2 and the third reflecting surface R3 does not become too long, thereby preventing the diameter of the third reflecting surface R3 from becoming large. By ensuring that the corresponding value of conditional expression (6) is not equal to or greater than the upper limit, the curvature of the first reflecting surface R1 can be made small, so that the distance between the first reflecting surface R1 and the second reflecting surface R2 does not become too long, thereby preventing the wide-angle light beam reflected by the first reflecting surface R1 from being blocked by the third reflecting surface R3. 0.25 <fM1 / fM3<4 (6)

[0066] To obtain better characteristics, the lower limit of conditional expression (6) should preferably be set to 0.5, and more preferably to 0.8, and the upper limit of conditional expression (6) should preferably be set to 2, and more preferably to 1.25.

[0067] When the distance on the optical axis between the first reflecting surface R1 and the second reflecting surface R2 is dM1M2, it is preferable that the imaging optical system satisfy the following conditional expression (7). As an example, the above distance dM1M2 is shown in FIG. 2. By ensuring that the corresponding value of conditional expression (7) is not equal to or smaller than the lower limit, it is possible to ensure the length in the optical axis direction required for the reflective optical system GR of the present disclosure. By ensuring that the corresponding value of conditional expression (7) is not equal to or larger than the upper limit, it becomes easy to ensure the length of the refractive optical system GL, which is advantageous for good correction of geometric aberrations in the refractive optical system GL. 0.2<|dM1M2| / d<0.5 (7)

[0068] To obtain better characteristics, the lower limit of conditional expression (7) should preferably be set to 0.25, and more preferably to 0.3. To obtain better characteristics, the upper limit of conditional expression (7) should preferably be set to 0.45.

[0069] 1, there is an intersection between the first reflecting surface R1 and the optical axis Z. However, unlike the example of FIG. 1, if there is no intersection between the first reflecting surface R1 and the optical axis Z, the distance dM1M2 is determined as follows: A virtual surface is considered by extending the shape of the first reflecting surface R1 to the optical axis Z based on the design data for the shape of the first reflecting surface R1, and the intersection of this virtual surface with the optical axis Z is set as the endpoint of the distance dM1M2 on the first reflecting surface side. Similarly, if there is no intersection between the second reflecting surface R2 and the optical axis Z, a virtual surface is considered by extending the shape of the second reflecting surface R2 to the optical axis Z based on the design data for the shape of the second reflecting surface R2, and the intersection of this virtual surface with the optical axis Z is set as the endpoint of the distance dM1M2 on the second reflecting surface side.

[0070] In a configuration in which the lens closest to the reduction side of the refractive optical system GL has positive power, it is preferable that the imaging optical system satisfy the following conditional expression (8). Here, the Abbe number of the lens closest to the reduction side based on the d-line is defined as νp. By ensuring that the corresponding value of conditional expression (8) is not below the lower limit, low-dispersion materials can be used, which is advantageous for suppressing the occurrence of chromatic aberration. By ensuring that the corresponding value of conditional expression (8) is not above the upper limit, optical materials that are easily available can be used. 40<νp<100 (8)

[0071] In order to obtain better characteristics, it is more preferable to set the lower limit of conditional expression (8) to 45, and even more preferable to set it to 50.

[0072] The above-described preferred and possible configurations, including those related to the conditional expressions, can be combined in any desired manner, and are preferably selectively adopted as appropriate according to the required specifications. The example in Figure 1 is merely an example, and various modifications are possible within the scope of the gist of the technology of the present disclosure.

[0073] 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.

[0074] As an example, a preferred embodiment of the imaging optical system of the present disclosure consists of, in order along the optical path from the enlargement side to the reduction side, a reflective optical system GR and a refractive optical system GL including a plurality of lenses, wherein 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, wherein a first intermediate image M1 is formed on the optical path between the third reflecting surface R3 and the refractive optical system GL at a position conjugate to the reduction side image plane, and a second intermediate image M2 is formed within the reflective optical system GR at a position conjugate to the first intermediate image M1, and the intermediate images formed on the enlargement side of the refractive optical system GL are only the first intermediate image M1 and the second intermediate image M2, thereby satisfying the above conditional formula (1).

[0075] 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.

[0076] [Example 1] The configuration of the imaging optical system of Example 1 and a cross-sectional view of the light beam are shown in FIG. 1. The illustration method and configuration are as described above, so some overlapping explanations will be omitted here. The imaging optical system of Example 1 comprises, in order along the optical path from the magnification side to the reduction side, 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 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.

[0077] For the imaging optical system of Example 1, basic lens data is shown in Table 1, specifications are shown in Table 2, and aspherical coefficients are shown in Table 3.

[0078] The table of basic lens data 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 spacing on the optical axis between each surface and the surface adjacent to it 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 word "Reflecting surface" is written in the margin of the row corresponding to each reflective surface.

[0079] In the table of basic lens data, the sign of the radius of curvature of a surface with a convex shape facing the enlargement side is positive, and the sign of the radius of curvature of a surface with a convex shape facing the reduction side is negative. The column for the surface number corresponding to the aperture stop St lists the surface number and the phrase (St). The table of basic lens data also shows the optical element PP. The value in the bottom row of the D column in the table is the distance between the surface closest to the reduction side in the table and the display surface Sim.

[0080] Table 2 shows the focal length (f), the back focal length (Bf) in air equivalent distance, the F-number (FNo.), and the maximum full angle of view (2ω) based on the d-line. The [°] in the 2ω column indicates that the unit is degrees.

[0081] In the basic lens 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 3, 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, ... 16. The numerical values ​​of the aspherical coefficients in Table 3, "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×hm 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 Z where the vertex of the aspheric surface is in contact) h: Height (distance from optical axis Z to lens surface) C: Reciprocal of paraxial curvature radius KA, Am: aspherical coefficients In the aspherical formula, Σ means the summation over m.

[0082] 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.

[0083] [Table 1]

[0084] [Table 2]

[0085] [Table 3]

[0086] FIG. 3 shows aberration diagrams of the imaging optical system of Example 1 when the projection distance is 0.350 m (meters). "Projection distance" refers to the distance on the optical axis from the magnification-side imaging surface to the magnifying-side reflecting surface of the imaging optical system. From left to right, FIG. 3 shows spherical aberration, astigmatism, distortion, and lateral chromatic aberration. In the spherical aberration diagram, aberrations related to the d-line, C-line, and F-line are shown by solid lines, long-dashed lines, and short-dashed lines, respectively. In the astigmatism diagram, aberrations related to the d-line in the sagittal direction are shown by solid lines, and aberrations related to the d-line in the tangential direction are shown by short-dashed lines. In the distortion diagram, aberrations related to the d-line are shown by solid lines. In the lateral chromatic aberration diagram, aberrations related to the C-line and F-line are shown by long-dashed lines and short-dashed lines, respectively. In the spherical aberration diagram, the F-number value is shown after "FNo.=". In other aberration diagrams, the value of the maximum half angle of view is shown after "ω=".

[0087] The symbols, meanings, notation methods, and illustration methods of each data item related to the above-mentioned Example 1 are basically the same in the following Examples unless otherwise specified, and therefore, redundant explanations will be omitted below.

[0088] [Example 2] FIG. 4 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 enlargement side to the reduction side, 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 power, and a third reflecting surface R3 having positive power. The refractive optical system GL comprises, in order from the enlargement 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.

[0089] For the imaging optical system of Example 2, basic lens data is shown in Table 4, specifications are shown in Table 5, aspherical coefficients are shown in Table 6, and aberration diagrams at a projection distance of 0.255 m (meters) are shown in FIG.

[0090] [Table 4]

[0091] [Table 5]

[0092] [Table 6]

[0093] [Example 3] FIG. 6 shows a cross-sectional view of the configuration and light beam of the imaging optical system of Example 3. The imaging optical system of Example 3 comprises, in order along the optical path from the magnification side to the reduction side, 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 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.

[0094] For the imaging optical system of Example 3, basic lens data is shown in Table 7, specifications are shown in Table 8, aspherical coefficients are shown in Table 9, and aberration diagrams at a projection distance of 0.324 m (meters) are shown in FIG.

[0095] [Table 7]

[0096] [Table 8]

[0097] [Table 9]

[0098] [Example 4] FIG. 8 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 enlargement side to the reduction side, 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 power, and a third reflecting surface R3 having positive power. The refractive optical system GL comprises 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.

[0099] For the imaging optical system of Example 4, basic lens data is shown in Table 10, specifications are shown in Table 11, aspherical coefficients are shown in Table 12, and aberration diagrams at a projection distance of 0.430 m (meters) are shown in FIG.

[0100] [Table 10]

[0101] [Table 11]

[0102] [Table 12]

[0103] [Example 5] FIG. 10 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 enlargement side to the reduction side, 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 power, and a third reflecting surface R3 having positive power. The refractive optical system GL comprises, in order from the enlargement side to the reduction side, lenses L1 to L6, an aperture stop St, and lenses L7 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.

[0104] For the imaging optical system of Example 5, basic lens data is shown in Table 13, specifications are shown in Table 14, aspherical coefficients are shown in Table 15, and aberration diagrams at a projection distance of 0.420 m (meters) are shown in FIG.

[0105] [Table 13]

[0106] [Table 14]

[0107] [Table 15]

[0108] [Example 6] FIG. 12 shows a cross-sectional view of the configuration and light beam of the imaging optical system of Example 6. The imaging optical system of Example 6 comprises, in order along the optical path from the enlargement side to the reduction side, 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 and L2, an aperture stop St, and lenses L3 to L5. The second reflecting surface R2 is formed on the enlargement-side surface of lens L1. 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.

[0109] For the imaging optical system of Example 6, basic lens data is shown in Table 16, specifications are shown in Table 17, aspherical coefficients are shown in Table 18, and aberration diagrams at a projection distance of 0.177 m (meters) are shown in FIG.

[0110] [Table 16]

[0111] [Table 17]

[0112] [Table 18]

[0113] [Example 7] FIG. 14 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 enlargement side to the reduction side, 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 lens L0, 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. A second reflecting surface R2 having power is formed on the surface of lens L0 facing the refractive optical system (the right side in FIG. 14). The light beam reflected by the third reflecting surface R3 toward the enlargement side passes through the interior of lens L0, is reflected by the second reflecting surface R2, passes through the interior of lens L0 again, and is incident on the first reflecting surface R1. The refractive optical system GL comprises, in order from the enlargement side to the reduction side, lenses L1 to L3, an aperture stop St, and lenses L4 to L9. A first intermediate image M1 is formed on the optical path between the refractive optical system GL and the third reflecting surface R3, and a second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1.

[0114] For the imaging optical system of Example 7, basic lens data is shown in Table 19, specifications are shown in Table 20, aspherical coefficients are shown in Table 21, and aberration diagrams at a projection distance of 0.200 m (meters) are shown in FIG.

[0115] [Table 19]

[0116] [Table 20]

[0117] [Table 21]

[0118] [Example 8] FIG. 16 shows a cross-sectional view of the configuration and light beam of the imaging optical system of Example 8. The imaging optical system of Example 8 comprises, in order along the optical path from the magnification side to the reduction side, 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 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 part of the second intermediate image M2 is formed on the optical path between the second reflecting surface R2 and the first reflecting surface R1, and the other part is formed on the optical path between the third reflecting surface R3 and the second reflecting surface R2.

[0119] For the imaging optical system of Example 8, basic lens data is shown in Table 22, specifications are shown in Table 23, aspherical coefficients are shown in Table 24, and aberration diagrams at a projection distance of 0.470 m (meters) are shown in FIG.

[0120] [Table 22]

[0121] [Table 23]

[0122] [Table 24]

[0123] [Example 9] FIG. 18 shows a cross-sectional view of the configuration and light beam of the imaging optical system of Example 9. The imaging optical system of Example 9 comprises, in order along the optical path from the magnification side to the reduction side, 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 L3, an aperture stop St, and lenses L4 to L8. 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.

[0124] For the imaging optical system of Example 9, basic lens data is shown in Table 25, specifications are shown in Table 26, aspherical coefficients are shown in Tables 27A and 27B, and aberration diagrams at a projection distance of 0.183 m (meters) are shown in FIG. 19.

[0125] [Table 25]

[0126] [Table 26]

[0127] [Table 27A]

[0128] [Table 27B]

[0129] [Example 10] FIG. 20 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, 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.

[0130] For the imaging optical system of Example 10, basic lens data is shown in Table 28, specifications are shown in Table 29, aspherical coefficients are shown in Table 30, and aberration diagrams at a projection distance of 0.270 m (meters) are shown in FIG.

[0131] [Table 28]

[0132] [Table 29]

[0133] [Table 30]

[0134] [Example 11] FIG. 22 shows a cross-sectional view of the configuration and light beam of the imaging optical system of Example 11. The imaging optical system of Example 11 comprises, in order along the optical path from the magnification side to the reduction side, 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 on 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. An intermediate image M0 is formed inside the refractive optical system GL. 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] For the imaging optical system of Example 11, basic lens data is shown in Table 31, specifications are shown in Table 32, aspherical coefficients are shown in Table 33, and aberration diagrams at a projection distance of 0.140 m (meters) are shown in Figure 23. In Table 32, the absolute value of the focal length |f| is shown instead of the focal length f.

[0136] [Table 31]

[0137] [Table 32]

[0138] [Table 33]

[0139] Fig. 24 shows the configuration and light beams of an imaging optical system according to a modified example of Example 11. In Fig. 24, an intermediate image is not shown. The imaging optical system of Fig. 24 differs from the imaging optical system of Example 11 in that a reflecting surface RP having no power, which is an optical path bending member, is added to the optical path between lenses L6 and L7 in Example 11, bending the optical path by 90° within the refractive optical system GL. The other configurations of the imaging optical system of Fig. 24 are the same as those of the imaging optical system of Example 11. Bending the optical path enables a compact configuration.

[0140] [Example 12] FIG. 25 shows a cross-sectional view of the configuration of the imaging optical system of Example 12 and the light beam. The imaging optical system of Example 12 comprises, in order along the optical path from the enlargement side to the reduction side, 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 power, and a third reflecting surface R3 having positive power. The refractive optical system GL comprises, in order from the enlargement side to the reduction side, lenses L1 to L5, an aperture stop St, and lenses L6 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] For the imaging optical system of Example 12, basic lens data is shown in Table 34, specifications are shown in Table 35, aspherical coefficients are shown in Table 36, and aberration diagrams at a projection distance of 0.310 m (meters) are shown in Figure 26.

[0142] [Table 34]

[0143] [Table 35]

[0144] [Table 36]

[0145] [Example 13] FIG. 27 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, 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 L5, an aperture stop St, and lenses L6 to L9. 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.

[0146] For the imaging optical system of Example 13, the basic lens data is shown in Table 37, the specifications are shown in Table 38, the aspherical coefficients are shown in Table 39, and each aberration diagram when the projection distance is 65.8 mm (millimeters) is shown in Figure 28.

[0147] [Table 37]

[0148] [Table 38]

[0149] [Table 39]

[0150] [Example 14] FIG. 29 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 from the enlargement side to the reduction side along the optical path, a reflective optical system GR and a refractive optical system GL. The reflective optical system GR comprises, in order from the enlargement side to the reduction side along the optical path, a lens L0, 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 first reflecting surface R1 and the third reflecting surface R3 are formed on the same member and have the same surface shape. The light beam reflected by the first reflecting surface R1 toward the enlargement side passes through lens L0 and then enters a screen (not shown). The refractive optical system GL comprises, in order from the enlargement 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.

[0151] For the imaging optical system of Example 14, basic lens data is shown in Table 40, specifications are shown in Table 41, aspherical coefficients are shown in Table 42, and aberration diagrams at a projection distance of 0.350 m (meters) are shown in Figure 30.

[0152] [Table 40]

[0153] [Table 41]

[0154] [Table 42]

[0155] [Example 15] FIG. 31 shows a cross-sectional view of the configuration of the imaging optical system of Example 15 and the light beam. The imaging optical system of Example 15 comprises, in order along the optical path from the magnification side to the reduction side, 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. None of the lenses L1 to L12 are cemented lenses. Lenses L1 and L2 are in edge contact with each other, lenses L5 and L6 are in edge contact with each other, lenses L8 and L9 are in edge contact with each other, and lenses L10 and L11 are in edge contact with each other.

[0156] For the imaging optical system of Example 15, the basic lens data is shown in Table 43, the specifications are shown in Table 44, the aspherical coefficients are shown in Table 45, and each aberration diagram when the projection distance is 0.450 m (meters) is shown in Figure 32.

[0157] [Table 43]

[0158] [Table 44]

[0159] [Table 45]

[0160] Table 46 shows the corresponding values ​​of conditional expressions (1) to (8) and the value of maximum image height Y for the imaging optical systems of Examples 1 to 15. The corresponding values ​​of the Examples shown in Table 46 may be used as the upper or lower limits of the conditional expressions to set preferred ranges for the conditional expressions.

[0161] [Table 46]

[0162] The imaging optical systems of Examples 1 to 15 are configured to be compact, and in particular, the distance on the optical axis from the first reflecting surface to the display surface Sim is configured to be short. The imaging optical systems of Examples 1 to 15 have a wide angle of view, with a total angle of view of 150 degrees or more. Furthermore, the imaging optical systems of Examples 1 to 15 have well-corrected aberrations.

[0163] Next, a projection display device according to an embodiment of the present disclosure will be described. FIG. 33 is a schematic diagram of a projection display device according to an embodiment of the present disclosure. The projection display device 100 shown in FIG. 33 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. 33 only shows 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. 33.

[0164] 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.

[0165] Fig. 34 is a schematic diagram of a projection display device according to another embodiment of the present disclosure. Projection display device 200 shown in Fig. 34 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. 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. 34 only shows a schematic diagram of imaging optical system 210. An integrator is disposed between light source 215 and polarization separation prism 25, but is not shown in Fig. 34.

[0166] 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.

[0167] Fig. 35 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. 35 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. 35 only shows the imaging optical system 310. An integrator is disposed between the light source 315 and the dichroic mirror 32, but is not shown in Fig. 35.

[0168] 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.

[0169] Fig. 36 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. 36 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. 36 shows the imaging optical system 46 only in a simplified manner.

[0170] 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.

[0171] 37 and 38 are external views of a camera 800, which is an imaging device according to an embodiment of the present disclosure. Fig. 37 shows a perspective view of the camera 800 as seen from the front side, and Fig. 38 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.

[0172] 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.

[0173] 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.

[0174] 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.

[0175] 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.

[0176] 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.

[0177] 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.

[0178] The following additional notes are provided regarding the above embodiments and examples. [Appendix 1] The optical system comprises, in order from the magnification side to the reduction side along the optical path, 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 an optical path between the third reflecting surface and the refractive optical system and at a position conjugate with a reduction-side image-forming surface; a second intermediate image is formed in the reflecting optical system at a position conjugate with the first intermediate image; intermediate images formed on the magnification side of the refractive optical system are only the first intermediate image and the second intermediate image, If the maximum half angle of view on the magnification side is ω, 4.6 <tanω<50 (1) An imaging optical system that satisfies conditional expression (1) expressed as follows. [Appendix 2] The magnification of the imaging optical system is β, The distance on the optical axis from the first reflecting surface to the magnification-side image-forming surface is D0. When the distance on the optical axis from the first reflecting surface to the reduction-side image-forming surface is d, 77.5<|β×d / D0|<200 (2) 10. The imaging optical system according to claim 1, which satisfies conditional expression (2) shown below. [Appendix 3] RM1 is the distance between the optical axis and the reflection point that is the longest from the optical axis among the reflection points of the light beam on the first reflection surface, RM2 is the distance between the optical axis and the reflection point that is the longest from the optical axis among the reflection points of the light beam on the second reflecting surface, RM3 is the distance between the optical axis and the reflection point that is the longest from the optical axis among the reflection points of the light beam on the third reflecting surface, When the maximum image height on the reduction-side image forming surface is Y, 10<(RM1+RM2+RM3) / Y<25 (3) 3. The imaging optical system according to claim 1, which satisfies conditional expression (3) below. [Appendix 4] RM1 is the distance between the optical axis and the reflection point that is the longest from the optical axis among the reflection points of the light beam on the first reflection surface, When the distance on the optical axis from the first reflecting surface to the reduction-side image-forming surface is d, 0.1 <RM1 / d<0.5 (4) 4. The imaging optical system according to claim 1, which satisfies conditional expression (4) below. [Appendix 5] RM3 is the distance between the optical axis and the reflection point that is the longest from the optical axis among the reflection points of the light beam on the third reflecting surface, When the distance on the optical axis from the first reflecting surface to the reduction-side image-forming surface is d, 0.1 <RM3 / d<0.4 (5) 5. The imaging optical system according to claim 1, which satisfies conditional expression (5) below. [Appendix 6] 6. The imaging optical system according to claim 1, wherein the refractive optical system includes three or more negative lenses. [Appendix 7] 5. The imaging optical system according to claim 4, wherein the refractive optical system includes four or more negative lenses. [Appendix 8] 8. The imaging optical system according to claim 1, wherein the second intermediate image is formed on an optical path between the first reflecting surface and the second reflecting surface. [Appendix 9] The focal length of the first reflecting surface is fM1, When the focal length of the third reflecting surface is fM3, 0.25 <fM1 / fM3<4 (6) 9. The imaging optical system according to any one of claims 1 to 8, which satisfies conditional expression (6) shown below. [Appendix 10] 10. The imaging optical system according to claim 1, wherein the first reflecting surface and the third reflecting surface are formed on the same member and have the same surface shape. [Appendix 11] The distance on the optical axis between the first reflecting surface and the second reflecting surface is dM1M2, When the distance on the optical axis from the first reflecting surface to the reduction-side image-forming surface is d, 0.2<|dM1M2| / d<0.5 (7) 11. The imaging optical system according to claim 1, which satisfies conditional expression (7) below. [Appendix 12] the lens closest to the reduction side of the refractive optical system has a positive power; When the Abbe number of the lens on the most reduction side of the refractive optical system based on the d-line is νp, 40<νp<100 (8) 12. The imaging optical system according to claim 1, which satisfies conditional expression (8) below. [Appendix 13] 13. The imaging optical system according to claim 1, wherein the lens closest to the reduction side of the refractive optical system has an aspherical lens surface. [Appendix 14] 14. The imaging optical system according to claim 1, wherein at least one of the lens closest to the magnification side of the refractive optical system and the second lens from the magnification side of the refractive optical system is a first negative lens having negative power. [Appendix 15] 15. The imaging optical system according to claim 14, wherein the first negative lens has an aspherical lens surface. [Appendix 16] 16. The imaging optical system according to any one of claims 1 to 15, wherein the refractive optical system includes six or fewer lenses. [Appendix 17] 16. The imaging optical system according to any one of claims 1 to 15, wherein the refractive optical system includes 10 or more lenses. [Appendix 18] A projection display device comprising the imaging optical system according to any one of Supplementary Note 1 to Supplementary Note 17. [Appendix 19] An imaging device comprising the imaging optical system according to any one of Supplementary Note 1 to Supplementary Note 17. [Explanation of symbols]

[0179] 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 guide 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 B0 Minimum angle of view luminous flux B1 Maximum angle of view luminous flux d distance D0 distance dM1M2 interval GL refractive optical system GR reflective optical system L0~L14 lenses M0 intermediate image M1 1st intermediate image M2 2nd intermediate image PP optical components R1 1st reflective surface R2 2nd reflective surface R3 3rd reflective surface RM1 distance RM2 distance RM3 distance RP reflective surface Scr Screen Sim display surface St aperture stop Y Maximum image height Z optical axis ω Maximum half angle of view

Claims

1. The optical system comprises, in order from the magnification side to the reduction side along the optical path, 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 an optical path between the third reflecting surface and the refractive optical system and at a position conjugate with a reduction-side image-forming surface; a second intermediate image is formed in the reflection optical system at a position conjugate with the first intermediate image; intermediate images formed on the magnification side of the refractive optical system are only the first intermediate image and the second intermediate image, If the maximum half angle of view on the magnification side is ω, 4.6<tanω<50 (1) An imaging optical system that satisfies conditional expression (1) expressed as follows:

2. The magnification of the imaging optical system is β, The distance on the optical axis from the first reflecting surface to the magnification-side image-forming surface is D0. When the distance on the optical axis from the first reflecting surface to the reduction-side image-forming surface is d, 77.5<|β×d / D0|<200 (2) 2. The imaging optical system according to claim 1, which satisfies conditional expression (2) expressed as follows:

3. Among the reflection points of the light beam on the first reflecting surface, the distance between the reflection point that is the longest from the optical axis and the optical axis is defined as RM1, Among the reflection points of the light beam on the second reflecting surface, the distance between the reflection point that is the longest from the optical axis and the optical axis is defined as RM2, Among the reflection points of the light beam on the third reflecting surface, the distance between the reflection point that is the longest from the optical axis and the optical axis is defined as RM3; When the maximum image height on the reduction-side imaging surface is Y, 10<(RM1+RM2+RM3) / Y<25 (3) 2. The imaging optical system according to claim 1, which satisfies conditional expression (3) expressed as follows:

4. Among the reflection points of the light beam on the first reflecting surface, the distance between the reflection point that is the longest from the optical axis and the optical axis is defined as RM1, When the distance on the optical axis from the first reflecting surface to the reduction-side image-forming surface is d, 0.1<RM1 / d<0.5 (4) 2. The imaging optical system according to claim 1, which satisfies conditional expression (4) expressed as follows:

5. Among the reflection points of the light beam on the third reflecting surface, the distance between the reflection point that is the longest from the optical axis and the optical axis is defined as RM3; When the distance on the optical axis from the first reflecting surface to the reduction-side image-forming surface is d, 0.1<RM3 / d<0.4 (5) 2. The imaging optical system according to claim 1, which satisfies conditional expression (5) expressed as follows:

6. The imaging optical system according to claim 1 , wherein the refractive optical system includes three or more negative lenses.

7. The imaging optical system according to claim 4 , wherein the refractive optical system includes four or more negative lenses.

8. 2. The imaging optical system according to claim 1, wherein the second intermediate image is formed on an optical path between the first reflecting surface and the second reflecting surface.

9. The focal length of the first reflecting surface is fM1, When the focal length of the third reflecting surface is fM3, 0.25<fM1 / fM3<4 (6) 2. The imaging optical system according to claim 1, which satisfies conditional expression (6) expressed as follows:

10. 10. The imaging optical system according to claim 9, wherein the first reflecting surface and the third reflecting surface are formed on the same member and have the same surface shape.

11. The distance on the optical axis between the first reflecting surface and the second reflecting surface is dM1M2, When the distance on the optical axis from the first reflecting surface to the reduction-side image-forming surface is d, 0.2<|dM1M2| / d<0.5 (7) 2. The imaging optical system according to claim 1, which satisfies conditional expression (7) expressed as follows:

12. the lens closest to the reduction side of the refractive optical system has a positive power; When the Abbe number of the lens on the most reduction side of the refractive optical system based on the d-line is νp, 40<νp<100 (8) 2. The imaging optical system according to claim 1, which satisfies conditional expression (8) expressed as follows:

13. 2. The imaging optical system according to claim 1, wherein the lens closest to the reduction side of said refractive optical system has an aspherical lens surface.

14. 2. The imaging optical system according to claim 1, wherein at least one of the lens on the most magnifying side of said refractive optical system and the second lens from the magnifying side of said refractive optical system is a first negative lens having negative power.

15. The imaging optical system according to claim 14 , wherein the first negative lens has an aspherical lens surface.

16. 2. The imaging optical system according to claim 1, wherein the number of lenses included in the refractive optical system is six or less.

17. The imaging optical system according to claim 1 , wherein the refractive optical system includes ten or more lenses.

18. A projection display device comprising the imaging optical system according to any one of claims 1 to 17.

19. An imaging device comprising the imaging optical system according to any one of claims 1 to 17.

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