IMAGING OPTICAL SYSTEM, PROJECTION DISPLAY DEVICE, AND IMAGING APPARATUS

Abstract

To provide an image formation optical system which has a wide field angle, is made compact, has superior manufacturability and assemblability, and maintains excellent optical performance, a projection type display device which comprises the image formation optical system, and an imaging device which comprises the image formation optical system.SOLUTION: An image formation optical system consists of a first optical system and a second optical system in order from an enlargement side. An intermediate image is formed between the first optical system and second optical system. A specific lens which is closest to the intermediate image on an optical system among aspherical lenses included in the first optical system has a meniscus shape which has a convex surface on a reduction side in a paraxial region. The image formation optical system satisfies a predetermined conditional expression related to a maximum image height, a focal length, and the specific lens.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed herein relates to an imaging optical system, a projection display device, and an imaging device. [Background technology]

[0002] 2. Description of the Related Art As an imaging optical system applicable to a projection display device and an imaging device, for example, an optical system described in Patent Document 1 below is known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-211479 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for imaging optical systems that have a wide angle of view, yet are compact, have excellent manufacturability and assembly properties, and have good optical performance with various aberrations appropriately corrected.

[0005] The present disclosure has been made in consideration of the above circumstances, and aims to provide an imaging optical system that has a wide angle of view while being compact, has excellent manufacturability and assembly properties, and maintains good optical performance, a projection-type 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 aspect of the technique disclosed herein is an imaging optical system consisting of a first optical system and a second optical system in that order along an optical path from the enlargement side to the reduction side, in which an intermediate image is formed on the optical path between the first optical system and the second optical system, the first optical system including at least one aspherical lens, and among the aspherical lenses included in the first optical system, a specific lens which is the aspherical lens closest to the intermediate image on the optical path has a meniscus shape with a convex surface facing the reduction side in a paraxial region, and the distance from the intersection of a normal and the optical axis at a certain point P on the lens surface to point P is defined as the local radius of curvature at point P, and the sign of the local radius of curvature is negative if the intersection is on the enlargement side of point P and positive if the intersection is on the reduction side of point P, at any point within the effective diameter of the reduction-side surface of the specific lens the sign of the local radius of curvature at the magnification side of the imaging optical system is negative, Ymax is the maximum image height on the reduction side of the imaging optical system, f is the focal length of the imaging optical system, fA is the focal length of the specific lens, Ra1 is the paraxial radius of curvature of the enlargement side surface of the specific lens, Ra2 is the paraxial radius of curvature of the reduction side surface of the specific lens, Rb1 is the local radius of curvature at the intersection of a ray of light incident from the image surface on the reduction side of the imaging optical system to the imaging optical system parallel to the optical axis at a height of 2.5×|f| from the optical axis and the enlargement side surface of the specific lens, Rb2 is the local radius of curvature at the intersection of the ray of light and the reduction side surface of the specific lens, H2 is the height of the ray of light from the optical axis at the reduction side surface of the specific lens, and when the imaging optical system is a variable magnification optical system, f, Rb1, Rb2, and H2 are the respective values ​​at the wide-angle end, 2.5≦Ymax / |f|≦2.9 (1) -0.01<|f| / fA<0.03 (2) |Ra1|<|Rb1| (3) |Ra2|<|Rb2| (4) |Rb1|<|Rb2| (5) 1.65<|Ra2 / H2|<3 (6) The conditional expressions (1), (2), (3), (4), (5), and (6) expressed by the following formulae are satisfied.

[0007] It is preferable that the imaging optical system of the above aspect satisfies at least one of the following conditional expressions (1-1), (2-1), and (6-1). 2.5≦Ymax / |f|≦2.7 (1-1) -0.01<|f| / fA<0.025 (2-1) 1.75<|Ra2 / H2|<3 (6-1)

[0008] The imaging optical system of the above aspect preferably satisfies the following conditional expression (7), and more preferably satisfies the following conditional expression (7-1). -0.1<(1 / Rb1-1 / Rb2)×|f|<-0.015 (7) -0.1<(1 / Rb1-1 / Rb2)×|f|<-0.02 (7-1)

[0009] If the height from the optical axis of a ray on the enlargement side surface of a specific lens is H1, and if the imaging optical system is a variable magnification optical system, H1 is the value at the wide-angle end, it is preferable that the enlargement side surface of the specific lens within a radius |H1| from the optical axis is located off the optical axis, on the reduction side of a spherical surface with a radius of |Ra1|, centered on the optical axis, and passing through the intersection of the enlargement side surface of the specific lens and the optical axis, and that the reduction side surface of the specific lens within a radius |H2| from the optical axis is located off the optical axis, on the reduction side of a spherical surface with a radius of |Ra2|, centered on the optical axis, and passing through the intersection of the reduction side surface of the specific lens and the optical axis.

[0010] The imaging optical system of the above aspect preferably satisfies the following conditional expression (8), and more preferably satisfies the following conditional expression (8-1). 1.35<|H2 / (2.5×f)|<1.8 (8) 1.45<|H2 / (2.5×f)|<1.8 (8-1)

[0011] When one lens component is one cemented lens or one single lens, if the maximum of the heights from the optical axis of a ray at two air-contact surfaces that intersect with the optical axis of the lens component on the most reduction side of the first optical system and the heights from the optical axis of a ray at two air-contact surfaces that intersect with the optical axis of the lens component on the most enlargement side of the second optical system is defined as Hmax, and when the imaging optical system is a variable magnification optical system, Hmax is the value at the wide-angle end, it is preferable for the imaging optical system of the above aspect to satisfy the following conditional formula (9), and it is more preferable for it to satisfy the following conditional formula (9-1). 1<|Hmax / H2|<1.8 (9) 1<|Hmax / H2|<1.5 (9-1)

[0012] It is preferred that the sign of the local radius of curvature at any point within the effective diameter of the magnification side surface of a particular lens is negative.

[0013] The imaging optical system according to the above aspect may be configured so that an optical path deflection member for bending at least one optical path is disposed inside the imaging optical system.

[0014] The imaging optical system of the above aspect is preferably a zoom optical system, in which case the second optical system preferably includes a lens group that moves during zooming.

[0015] The imaging optical system of the above aspect is preferably configured so that the reduction side is telecentric.

[0016] A projection display device according to another aspect of the technology disclosed herein comprises a light valve that outputs an optical image and the imaging optical system of the above aspect, and the imaging optical system of the above aspect projects the optical image output from the light valve onto a screen.

[0017] An imaging device according to yet another aspect of the technique of the present disclosure includes the imaging optical system of the above aspect.

[0018] In addition, in this specification, "consisting of" and "consisting of" are intended to mean that in addition to the listed components, the following may be included: a lens having substantially no power; optical elements other than lenses, such as an aperture, a filter, and a cover glass; and mechanical parts, such as a lens flange, a lens barrel, an image sensor, and an image stabilization mechanism.

[0019] The values ​​used in the conditional expressions are based on the d-line. The "d-line," "C-line," and "F-line" described in this specification are emission lines, with the d-line having a wavelength of 587.56 nm (nanometers), the C-line having a wavelength of 656.27 nm (nanometers), and the F-line having a wavelength of 486.13 nm (nanometers). Effect of the Invention

[0020] According to the technology of the present disclosure, it is possible to provide an imaging optical system that has a wide angle of view while being compact, has excellent manufacturability and assembly properties, and maintains good optical performance, a projection-type display device equipped with this imaging optical system, and an imaging device equipped with this imaging optical system. [Brief description of the drawings]

[0021] [Figure 1] 1 is a cross-sectional view showing a configuration and a light beam of an imaging optical system according to an example of an embodiment of the present disclosure, which corresponds to the imaging optical system of Example 1. FIG. [Diagram 2] FIG. 13 is a diagram for explaining a local radius of curvature. [Diagram 3] FIG. 13 is a partial enlarged view for explaining H1, H2, and Hmax. [Figure 4] 1 is a diagram for explaining the surface shape of a specific lens. [Diagram 5] 3A to 3C are diagrams showing various aberrations of the imaging optical system of Example 1. [Figure 6] 4 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a first modified example of the first embodiment. FIG. [Figure 7] 11 is a cross-sectional view showing a configuration of an imaging optical system and a light beam according to a second modified example of the first embodiment. FIG. [Figure 8] 10 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a second embodiment. [Figure 9] 6A to 6C are diagrams showing various aberrations of the imaging optical system according to the second embodiment. [Figure 10] 11 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a third embodiment. [Figure 11] 11A to 11C are diagrams showing various aberrations of the imaging optical system of Example 3. [Figure 12] 11 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a fourth embodiment. [Figure 13] 11A to 11C are diagrams showing various aberrations of the imaging optical system according to the fourth embodiment. [Figure 14] 11 is a cross-sectional view showing the configuration of an imaging optical system and a light beam according to a fifth embodiment. [Figure 15]13A to 13C are diagrams showing various aberrations in the imaging optical system of Example 5. [Figure 16] 1 is a schematic configuration diagram of a projection display device according to an embodiment. [Figure 17] FIG. 11 is a schematic configuration diagram of a projection display device according to another embodiment. [Figure 18] FIG. 13 is a schematic configuration diagram of a projection display device according to yet another embodiment. [Figure 19] 1 is a perspective view of the front side of an imaging device according to an embodiment. [Figure 20] 20 is a perspective view of the rear side of the imaging device shown in FIG. 19. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] An example of an embodiment of the technology of the present disclosure will be described in detail below with reference to the drawings. Fig. 1 shows a configuration of an imaging optical system 1 according to an embodiment of the present disclosure in a cross section including an optical axis Z. The configuration example shown in Fig. 1 corresponds to Example 1 described below. In Fig. 1, the left side is the enlargement side and the right side is the reduction side, and an axial light beam 2 and a light beam 3 at a maximum image height Ymax are also shown.

[0023] The imaging optical system 1 can be a projection optical system mounted in a projection display device, or an imaging optical system mounted in an imaging device. In the following, the imaging optical system 1 will be described assuming that it is used as a projection optical system.

[0024] Assuming that the imaging optical system 1 is mounted on a projection display device, Fig. 1 shows an example in which an optical member PP is disposed on the reduction side of the imaging optical system 1. The optical member PP is a member assumed to be a filter, a cover glass, a color synthesis prism, etc. The optical member PP is a member that does not have power, and a configuration in which the optical member PP is omitted is also possible.

[0025] 1 also shows a screen Scr and an image display surface Sim of a light valve, assuming that the imaging optical system 1 is mounted on a projection display device. In a projection display device, a light beam having image information imparted to it on the image display surface Sim is incident on the imaging optical system 1 via an optical member PP, and is projected onto the screen Scr by the imaging optical system 1. In the example of FIG. 1, the image display surface Sim corresponds to the image surface on the reduction side, and the screen Scr corresponds to the image surface on the enlargement side. In the following description, "enlargement side" refers to the screen Scr side on the optical path, and "reduction side" refers to the image display surface Sim side on the optical path.

[0026] The imaging optical system 1 is made up of, in order from the enlargement side to the reduction side along the optical path, a first optical system G1 and a second optical system G2. As an example, in the imaging optical system 1 of Fig. 1, the first optical system G1 is made up of lenses L1a to L1m, in order from the enlargement side to the reduction side, and the second optical system G2 is made up of lenses L2a to L2d, an aperture stop St, and lenses L2e to L2k, in order from the enlargement side to the reduction side.

[0027] The imaging optical system 1 is a relay type optical system, and forms an intermediate image MI of an image displayed on an image display surface Sim inside the imaging optical system 1, and projects the intermediate image MI onto a screen Scr to form a projected image. A system that forms an intermediate image MI can prevent the lens on the enlargement side from becoming large while securing a wide angle of view, and is therefore suitable for a projection display device that requires a wide angle of view. In the imaging optical system 1, the intermediate image MI is formed on the optical path between the first optical system G1 and the second optical system G2. In FIG. 1, only a part of the intermediate image MI, including the vicinity of the optical axis Z, is simply shown by a dotted line so that the position of the intermediate image MI on the optical axis Z can be seen. The intermediate image MI in FIG. 1 does not show an exact shape.

[0028] The imaging optical system 1 is configured to satisfy the following conditional expression (1), where Ymax is the maximum image height on the reduction side and f is the focal length of the imaging optical system 1. Avoiding the lower limit of conditional expression (1) is advantageous for ensuring a wide angle of view. Avoiding the upper limit of conditional expression (1) is advantageous for preventing the system from becoming large. In order to obtain better characteristics, it is more preferable that the imaging optical system 1 satisfy the following conditional expression (1-1). 2.5≦Ymax / |f|≦2.9 (1) 2.5≦Ymax / |f|≦2.7 (1-1)

[0029] The first optical system G1 includes at least one aspherical lens. The inclusion of an aspherical lens is advantageous for a small F-number, a wide angle of view, and good aberration correction. In particular, in an optical system with a wide angle of view, it is very effective in correcting distortion aberration. In the example of Figure 1, the lens L1a and the lens Lll are aspherical lenses.

[0030] For convenience of explanation, the aspherical lens included in the first optical system G1 that is closest to the intermediate image MI on the optical path will be referred to as the specific lens LS. That is, the specific lens LS is the aspherical lens that is closest to the reduction side on the optical path among the aspherical lenses included in the first optical system G1. In the example of FIG. 1, the lens L1l is the specific lens LS.

[0031] When the focal length of the specific lens LS is fA, the imaging optical system 1 is configured to satisfy the following conditional formula (2) with respect to fA and the above f. In this specification, the "focal length" used in the conditional formulas means the focal length in the paraxial region. By not being equal to or less than the lower limit of the conditional formula (2), the specific lens LS does not have an excessively strong negative refractive power, so that the refractive power of the positive lens other than the specific lens LS arranged near the intermediate image MI does not become too strong, which is advantageous for correcting distortion aberration and field curvature well. By not being equal to or more than the upper limit of the conditional formula (2), it is possible to suppress the sensitivity to errors from increasing, which is advantageous for improving manufacturability and assembly. In order to obtain better characteristics, it is preferable that the imaging optical system 1 satisfies the following conditional formula (2-1). -0.01<|f| / fA<0.03 (2) -0.01<|f| / fA<0.025 (2-1)

[0032] Moreover, the specific lens LS is configured to have a meniscus shape with a convex surface facing the reduction side in the paraxial region, which is advantageous for satisfactorily correcting distortion and curvature of field.

[0033] The specific lens LS has aspheric shapes on both the enlargement side surface and the reduction side surface, and is configured so that the surface shapes satisfy predetermined conditional expressions. Below, the terms and symbols related to these conditional expressions will be explained with reference to Figures 2, 3, and 4.

[0034] In an aspheric lens, the paraxial radius of curvature (i.e., the radius of curvature in the paraxial region) does not necessarily coincide with the radius of curvature at a point outside the paraxial region. Therefore, in the technology disclosed herein, as shown in FIG. 2, the distance from the intersection OP of the normal Np and the optical axis Z at a certain point P on the lens surface SA to the point P is defined as the local radius of curvature Rbp at the point P. The normal Np is a line that is perpendicular to the tangent plane of the lens surface SA at the point P and passes through the point P. In FIG. 2, the length of the line segment connecting the intersection OP and the point P is shown as the absolute value |Rbp| of the local radius of curvature Rbp. For ease of understanding, FIG. 2 also shows a cross section of a spherical surface Cp with a radius |Rbp|, centered on the intersection OP and passing through the point P. Note that FIG. 2 is a diagram showing an example for explanation. The local radius of curvature can be calculated at any point on a lens surface of any shape.

[0035] The sign of the local radius of curvature is negative when the intersection point OP is on the enlargement side of point P, and positive when the intersection point OP is on the reduction side of point P. In Figure 2, the left side of the figure is the enlargement side, and the right side is the reduction side, and in the example of Figure 2, the sign of the local radius of curvature at point P is negative.

[0036] The imaging optical system 1 is configured so that the sign of the local radius of curvature at any point within the effective diameter of the reduction-side surface of the specific lens LS is negative. This shape makes it possible to reduce sensitivity to errors, which is advantageous for improving manufacturability and assembly. Note that the effective diameter means the diameter of a circle consisting of the point farthest from the optical axis Z in the radial direction when considering the point where all light rays contributing to imaging intersect with the lens surface.

[0037] In addition, in the imaging optical system 1, it is preferable that the sign of the local radius of curvature at any point within the effective diameter of the enlargement-side surface of the specific lens LS is also negative. In this case, it is possible to further reduce sensitivity to errors, which is advantageous for improving manufacturability and assembly.

[0038] In the conditional formula described later, when defining the local radius of curvature of the specific lens LS, a light ray 4 is used that is parallel to the optical axis Z and incident on the imaging optical system 1 from the image plane on the reduction side of the imaging optical system 1 at a height of 2.5×|f| from the optical axis Z. FIG. 3 shows a partial enlarged view of the imaging optical system 1 on which the light ray 4 is incident. In FIG. 3, some symbols and the aperture stop St are omitted to avoid complication of the figure. As shown in FIG. 3, the intersection point of the light ray 4 and the surface on the enlargement side of the specific lens LS is defined as point P1, and the intersection point of the light ray 4 and the surface on the reduction side of the specific lens LS is defined as point P2. The local radius of curvature at point P1 is defined as Rb1, and the height of point P1 from the optical axis Z is defined as H1. The local radius of curvature at point P2 is defined as Rb2, and the height of point P2 from the optical axis Z is defined as H2.

[0039] Fig. 4 shows the paraxial radius of curvature Ra1 of the enlargement side surface of the specific lens LS in Fig. 1, and the paraxial radius of curvature Ra2 of the reduction side surface of the specific lens LS. In Fig. 4, for ease of understanding, a two-dot chain line shows a cross section of a spherical surface C1 having a radius |Ra1|, a center O1 on the optical axis Z, and passing through the intersection of the enlargement side surface of the specific lens LS and the optical axis Z, and a dashed line shows a cross section of a spherical surface C2 having a radius |Ra2|, a center O2 on the optical axis Z, and passing through the intersection of the reduction side surface of the specific lens LS and the optical axis Z. Fig. 4 also shows the above points P1, P2, height H1, and height H2.

[0040] As shown in FIG. 4, the enlargement side surface of the specific lens LS within a radius |H1| from the optical axis Z is preferably located on the reduction side of the spherical surface C1 outside the optical axis Z, and the reduction side surface of the specific lens LS within a radius |H2| from the optical axis Z is preferably located on the reduction side of the spherical surface C2 outside the optical axis Z. In this case, it is advantageous to give the specific lens LS an aspheric effect and to satisfactorily correct distortion aberration and field curvature. Note that, although H1 is shown only below the optical axis Z in FIG. 4, the above "within a radius |H1| from the optical axis Z" is not limited to below the optical axis Z, but refers to the range in all radial directions. In other words, the above "the enlargement side surface of the specific lens LS within a radius |H1| from the optical axis Z is located on the reduction side of the spherical surface C1 outside the optical axis Z" means that the entire area within a radius |H1| from the optical axis Z, except for the point on the optical axis Z, of the enlargement side surface of the specific lens LS is located on the reduction side of the spherical surface C1. Similarly, the above statement "the reduction-side surface of the specific lens LS within a radius |H2| from the optical axis Z is located outside the optical axis Z and on the reduction side of the spherical surface C2" means that the entire area of ​​the reduction-side surface of the specific lens LS within a radius |H2| from the optical axis Z, excluding points on the optical axis Z, is located on the reduction side of the spherical surface C2.

[0041] The specific lens LS is configured to satisfy the following conditional expressions (3), (4), and (5) with respect to the above Ra1, Ra2, Rb1, and Rb2. Satisfying the conditional expressions (3), (4), and (5) is advantageous in correcting distortion and curvature of field well. |Ra1|<|Rb1| (3) |Ra2|<|Rb2| (4) |Rb1|<|Rb2| (5)

[0042] Moreover, the specific lens LS is configured to satisfy the following conditional formula (6) with respect to the above Ra1 and H2. By ensuring that the value is not equal to or less than the lower limit of conditional formula (6), it is possible to suppress the sensitivity to errors from increasing, which is advantageous for improving manufacturability and assembly. By ensuring that the value is not equal to or greater than the upper limit of conditional formula (6), it is easy to maintain a shape in which the sign of the local radius of curvature is not inverted in the radial direction while obtaining the effect of an aspheric surface. Maintaining this shape is advantageous for improving manufacturability and assembly. In order to obtain better characteristics, it is more preferable that the specific lens LS satisfies the following conditional formula (6-1), and even more preferable that the value is equal to or less than the following conditional formula (6-2). 1.65<|Ra2 / H2|<3 (6) 1.75<|Ra2 / H2|<3 (6-1) 1.95<|Ra2 / H2|<3 (6-2)

[0043] With respect to Rb1 and Rb2, it is preferable that the specific lens LS satisfies the following conditional formula (7). By not being equal to or less than the lower limit of conditional formula (7), it is possible to suppress an increase in the thickness ratio (i.e., the ratio of the thickness of the lens periphery to the thickness of the lens center) and sensitivity to errors, which is advantageous for improving manufacturability and assembly. By not being equal to or greater than the upper limit of conditional formula (7), it is advantageous for obtaining a good aberration correction effect while suppressing an increase in the lens diameter. In order to obtain better characteristics, it is more preferable that the specific lens LS satisfies the following conditional formula (7-1). -0.1<(1 / Rb1-1 / Rb2)×|f|<-0.015 (7) -0.1<(1 / Rb1-1 / Rb2)×|f|<-0.02 (7-1)

[0044] With respect to H2 and f above, it is preferable that the imaging optical system 1 satisfies the following conditional expression (8). By not falling below the lower limit of conditional expression (8), it is advantageous for distortion and curvature of field to be well corrected. By not falling above the upper limit of conditional expression (8), it is possible to prevent the lens diameter from becoming large. In order to obtain better characteristics, it is more preferable that the imaging optical system 1 satisfies the following conditional expression (8-1), and it is even more preferable that the imaging optical system 1 satisfies the following conditional expression (8-2). 1.35<|H2 / (2.5×f)|<1.8 (8) 1.45<|H2 / (2.5×f)|<1.8 (8-1) 1.45<|H2 / (2.5×f)|<1.65 (8-2)

[0045] Furthermore, it is preferable that the imaging optical system 1 satisfies the following conditional formula (9) with respect to H2 and Hmax described below. Hmax is the maximum height among the heights of the light ray 4 from the optical axis Z at two air-contact surfaces intersecting with the optical axis Z of the lens component on the most reduction side of the first optical system G1 and the heights of the light ray 4 from the optical axis Z at two air-contact surfaces intersecting with the optical axis Z of the lens component on the most enlargement side of the second optical system G2. Here, one lens component means one cemented lens or one single lens. The two air-contact surfaces intersecting with the optical axis Z of one lens component are the surface on the enlargement side of that lens component and the surface on the reduction side of that lens component.

[0046] An example of Hmax is shown in Fig. 3. In the example of Fig. 3, Hmax is the maximum height of the light ray 4 from the optical axis Z on four surfaces: the enlargement side surface of lens L1m, the reduction side surface of lens L1m, the enlargement side surface of lens L2a, and the reduction side surface of lens L2b. In the example of Fig. 3, Hmax is the height of the light ray 4 from the optical axis Z on the enlargement side surface of lens L1m.

[0047] By satisfying conditional expression (9), the specific lens LS is not too far away from the intermediate image MI, which is advantageous for good correction of distortion and curvature of field. Also, by ensuring that the upper limit of conditional expression (9) is not exceeded, it is possible to prevent the lens component closest to the intermediate image MI on the enlargement or reduction side of the intermediate image MI from becoming large in diameter. In order to obtain better characteristics, it is more preferable that the imaging optical system 1 satisfies the following conditional expression (9-1). 1<|Hmax / H2|<1.8 (9) 1<|Hmax / H2|<1.5 (9-1)

[0048] The imaging optical system 1 is preferably configured so that the reduction side is telecentric. In a projection display device, the color synthesis prism disposed between the imaging optical system 1 and the light valve changes its spectral characteristics depending on the angle of the incident light. It is desirable that the imaging optical system 1 used in combination with such a member having the incidence angle dependency is configured so that the reduction side is telecentric. Note that "the reduction side is configured so that the reduction side is telecentric" is not limited to the inclination of the chief ray with respect to the optical axis Z of 0 degrees, and an error of -3 degrees or more and +3 degrees or less is allowed. In the case of an optical system that does not include an aperture stop St, when the light beam is viewed in the direction from the enlargement side to the reduction side, the telecentricity may be judged by substituting the bisector angle line between the upper maximum light beam and the lower maximum light beam in the cross section of the light beam that is focused at an arbitrary point on the image plane on the reduction side as the chief ray.

[0049] The imaging optical system 1 may be a variable magnification optical system. When the imaging optical system 1 is a variable magnification optical system, all the symbols used in the above conditional expressions are values ​​at the wide-angle end.

[0050] When the imaging optical system 1 is a variable magnification optical system, it is preferable that the imaging optical system 1 is a zoom optical system. In this case, it is possible to obtain an optical system with high convenience and versatility. In particular, when the imaging optical system 1 is used as a projection optical system, a projection optical system having a wide angle of view has a large variation in the size of the projected image caused by an error in the installation distance (i.e., the distance between the screen Scr and the projection optical system), so that if the size can be adjusted by zooming, installation becomes easy. When the imaging optical system 1 is a zoom optical system, the zoom ratio is preferably 1.05 times or more, and more preferably 1.1 times or more.

[0051] When the imaging optical system 1 is a zoom optical system, it is preferable that the second optical system G2 includes a lens group that moves when the magnification is changed. Compared to the first optical system G1 arranged on the enlargement side, the lens diameter of the second optical system G2 is easier to reduce, so moving the lens group in the second optical system G2 is advantageous for reducing the load on the drive mechanism and making the device more compact. Note that the lens group is not limited to being composed of multiple lenses, and may be composed of only one lens.

[0052] The imaging optical system 1 in the example of FIG. 1 is a zoom lens. As shown in FIG. 1, the second optical system G2 is composed of, in order from the enlargement side to the reduction side, the second A lens group G2A, the second B lens group G2B, and the second C lens group G2C. During magnification change, the second A lens group G2A and the second B lens group G2B move while changing the mutual distance, and the first optical system G1 and the second C lens group G2C are fixed with respect to the image surface. The second A lens group G2A is composed of lenses L2a to L2b in order from the enlargement side to the reduction side. The second B lens group G2B is composed of lenses L2c to L2d, an aperture stop St, and lenses L2e to L2j in order from the enlargement side to the reduction side. The second C lens group G2C is composed of a lens L2k. It should be noted that the imaging optical system 1 in FIG. 1 is just an example, and in the technology disclosed herein, the number of lenses included in the first optical system G1 and the second optical system G2 may be different from the example shown in FIG.

[0053] In addition, while FIG. 1 shows an example of an imaging optical system 1 with a linear optical path, the technology of the present disclosure is not limited to this. As shown in a modified example described later, the imaging optical system of the technology of the present disclosure may have an optical path deflection member disposed therein for bending at least one optical path, so as to have a curved optical path. A system that forms an intermediate image MI tends to have a long overall optical system length, but by bending the optical path, the device can be configured compactly. As the optical path deflection member, for example, a reflecting member such as a reflecting mirror can be used.

[0054] A bending angle of 90 degrees for the optical path is preferable from the viewpoint of manufacturability and assembly because it is a simple configuration, but an angle other than 90 degrees may be used. Furthermore, even if the angle is 90 degrees, it is not limited to being strictly 90 degrees, and an error of -3 degrees or more and +3 degrees or less may be allowed.

[0055] The number of times the optical path is bent can be set arbitrarily. When the optical path is bent twice, the optical path may be bent in the same direction both times, or the optical path may be bent in opposite directions the first and second times. When the optical path is bent twice, the optical axis Z may be configured to be in the same plane before and after bending the optical path, or may be configured to be in different planes.

[0056] In addition, the "enlargement side" and the "reduction side" according to the technology of the present disclosure are determined along the optical path, and this also applies to an imaging optical system having a curved optical path. For example, in an imaging optical system having a curved optical path, "lens LA is on the enlargement side of lens LB" has the same meaning as "lens LA is on the optical path on the enlargement side of lens LB."

[0057] All optical elements having power included in the imaging optical system 1 may be configured to be lenses. It is preferable that all lenses included in the imaging optical system 1 have a refractive index for the d-line of 2.2 or less, and more preferably 2 or less considering the current availability of lens materials. It is preferable that the imaging optical system 1 has an F-number of 3 or less. It is preferable that the imaging optical system 1 has a distortion aberration suppressed within a range of -3% or more and +3% or less. It is preferable that the imaging optical system 1 has a total angle of view larger than 120 degrees, more preferably larger than 125 degrees, and even more preferably larger than 130 degrees.

[0058] The above-mentioned preferred and possible configurations, including those related to the conditional expressions, can be arbitrarily combined, and are preferably selectively adopted as appropriate according to the required specifications. Note that the range of possible conditional expressions is not limited to the conditional expressions described in the form of expressions, but includes a range obtained by arbitrarily combining the lower and upper limits of the preferred, more preferred, and even more preferred conditional expressions.

[0059] Next, examples and modified examples of the imaging optical system according to the technology of the present disclosure will be described. Note that the reference symbols attached to the lenses in the cross-sectional views of each example are used independently for each example to avoid complication of explanation due to an increase in the number of digits of the reference symbols. Therefore, even if common reference symbols are attached in drawings of different examples, it does not necessarily mean that they have a common configuration.

[0060] [Example 1] The lens configuration and cross-sectional view of the light beam of the imaging optical system 1 of the first embodiment are shown in FIG. 1, and the configuration and the method of illustration are as described above, so some of the overlapping explanations will be omitted here. The imaging optical system 1 of the first embodiment is a zoom lens, and is composed of a first optical system G1 and a second optical system G2, in order from the enlargement side to the reduction side. An intermediate image MI is formed between the first optical system G1 and the second optical system G2. The first optical system G1 is composed of lenses L1a to L1m, in order from the enlargement side to the reduction side. The second optical system G2 is composed of a second A lens group G2A, a second B lens group G2B, and a second C lens group G2C, in order from the enlargement side to the reduction side. During magnification, the second A lens group G2A and the second B lens group G2B move while changing the mutual interval, and the first optical system G1 and the second C lens group G2C are fixed with respect to the image surface. The second-A lens group G2A is composed of, in order from the enlargement side to the reduction side, lenses L2a to L2b. The second-B lens group G2B is composed of, in order from the enlargement side to the reduction side, lenses L2c to L2d, an aperture stop St, and lenses L2e to L2j. The second-C lens group G2C is composed of lens L2k. During focusing, a focus group composed of lenses L1e to L1f moves along the optical axis Z, and the other lenses are fixed with respect to the image surface on the reduction side.

[0061] For the imaging optical system 1 of Example 1, basic lens data is shown in Tables 1A and 1B, specifications and variable surface spacing is shown in Table 2, and aspheric coefficients are shown in Table 3. Here, to avoid making one table too long, the basic lens data is shown in two tables, Table 1A and Table 1B. Table 1A shows the first optical system G1, and Table 1B shows the second optical system G2 and optical member PP.

[0062] In Tables 1A and 1B, the Sn column shows the surface numbers with the surface on the most enlargement side designated as surface 1 and the numbers increasing by one toward the reduction side, the R column shows the radius of curvature of each surface, and the D column shows the surface distance on the optical axis Z between each surface and its adjacent surface on the reduction side. Additionally, the Nd column shows the refractive index for the d-line of each component, and the νd column shows the Abbe number of each component based on the d-line. The surfaces in the bottom column of Table 1B correspond to the image surface on the reduction side.

[0063] In Tables 1A and 1B, the sign of the radius of curvature of a surface with a convex surface facing the enlargement side is positive, and the sign of the radius of curvature of a surface with a convex surface facing the reduction side is negative. In Table 1B, the surface number and the term (St) are entered in the column for the surface number of the surface corresponding to the aperture stop St. In Table 1B, the symbol DD[ ] is used for the variable surface spacing when varying magnification, and the surface number on the enlargement side of this spacing is entered in the [ ] in the D column.

[0064] Table 2 shows the zoom ratio Zr, absolute value of focal length |f|, F-number FNo., maximum total angle of view 2ω, and variable surface spacing when changing magnification for imaging optical system 1, based on the d-line. The (°) in the 2ω column means that the unit is degrees. In Table 2, the values ​​for the wide-angle end and telephoto end are shown in the columns labeled WIDE and TELE, respectively. The basic lens data and |f| are values ​​when the distance on the optical axis Z from the image plane on the magnification side to the surface on the most magnification side of imaging optical system 1 is infinite.

[0065] In the basic lens data, the surface numbers of aspheric surfaces are marked with an *, and the column for the radius of curvature of the aspheric surface shows the numerical value of the paraxial radius of curvature. In Table 3, the column Sn shows the surface numbers of the aspheric surfaces, and the columns KA and Am show the numerical values ​​of the aspheric coefficients for each aspheric surface. m is an integer of 3 or more, and for example, m = 3, 4, 5, ... 20 for the aspheric surfaces of Example 1. The numerical values ​​of the aspheric coefficients in Table 3, "E±n" (n: integer), are expressed as "×10 ±n " KA and Am are aspheric coefficients in the aspheric equation expressed below. Zd = C × H 2 / {1+(1-KA×C 2 ×H 2 ) 1 / 2}+ΣAm×H m however, Zd: Aspheric depth (a plane perpendicular to the optical axis Z where the apex of the aspheric surface is in contact with the point on the aspheric surface at height H) (the length of the perpendicular line) H: Height (distance from optical axis Z to lens surface) C: Reciprocal of paraxial curvature radius KA, Am: Aspheric coefficients In the aspheric surface formula, Σ means the summation with respect to m.

[0066] [Table 1A]

[0067] [Table 1B]

[0068] [Table 2]

[0069] [Table 3]

[0070] FIG. 5 shows each aberration diagram of the imaging optical system 1 of Example 1 when the magnification is 150 times. In FIG. 5, each aberration diagram at the wide-angle end is shown in the upper row labeled "WIDE", and each aberration diagram at the telephoto end is shown in the lower row labeled "TELE". In FIG. 5, from the left, spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration are shown. 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 aberration 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. FNo. in the spherical aberration diagram means F-number, and ω in the other aberration diagrams means half angle of view.

[0071] In addition, the above tables show values ​​rounded to a certain number of digits. The values ​​in the above tables are data normalized so that the absolute value of the focal length of the imaging optical system 1 is 1 when the distance on the optical axis Z from the image plane on the magnification side to the surface on the most magnification side of the imaging optical system 1 at the wide-angle end is infinite. The symbols, meanings, description methods, and illustration methods of each data item related to the above Example 1 are basically the same for the following examples unless otherwise specified.

[0072] [First Modification] FIG. 6 shows a cross-sectional view of the lens configuration and light beam of the imaging optical system of the first modified example. The example of FIG. 6 has a configuration in which two optical path deflection members are added to the imaging optical system of the first embodiment. In the example of FIG. 6, a reflecting mirror R1 and a reflecting mirror R2 are used as optical path deflection members, and each of them bends the optical path by 90 degrees to form a substantially U-shaped bent optical path as a whole. The imaging optical system of FIG. 6 is composed of a first optical system G1 and a second optical system G2, in order from the enlargement side to the reduction side. The first optical system G1 is composed of lenses L1a to L1h, a reflecting mirror R1, and lenses L1i to L1m, in order from the enlargement side to the reduction side. The second optical system G2 is composed of a reflecting mirror R2, lenses L2a to L2d, an aperture stop St, and lenses L2e to L2k, in order from the enlargement side to the reduction side.

[0073] [Second modified example] Fig. 7 shows a cross-sectional view of the lens configuration and light beam of the imaging optical system of the second modified example. The example of Fig. 7 differs from the example of Fig. 6 in the direction in which the optical path is bent by the reflecting mirror R2, but the other configurations are the same as the example of Fig. 6.

[0074] [Example 2] FIG. 8 shows a cross-sectional view of the lens configuration and light beam of the imaging optical system of Example 2. The imaging optical system of Example 2 is a zoom lens, and is composed of a first optical system G1 and a second optical system G2, in order from the enlargement side to the reduction side. An intermediate image MI is formed between the first optical system G1 and the second optical system G2. The first optical system G1 is composed of lenses L1a to L1m, in order from the enlargement side to the reduction side. The second optical system G2 is composed of a second A lens group G2A, a second B lens group G2B, and a second C lens group G2C, in order from the enlargement side to the reduction side. During magnification, the second A lens group G2A and the second B lens group G2B move while changing the mutual interval, and the first optical system G1 and the second C lens group G2C are fixed with respect to the image surface. The second A lens group G2A is composed of lenses L2a to L2b, in order from the enlargement side to the reduction side. The second lens group G2B is composed of, in order from the enlargement side to the reduction side, lenses L2c to L2d, an aperture stop St, and lenses L2e to L2i. The second lens group G2C is composed of lens L2j. During focusing, a focus group composed of lenses L1e to L1f moves along the optical axis Z, and the other lenses are fixed with respect to the image plane on the reduction side.

[0075] For the imaging optical system of Example 2, basic lens data is shown in Tables 4A and 4B, specifications and variable surface spacing is shown in Table 5, aspheric coefficients are shown in Table 6, and aberration diagrams for a magnification of 150 times are shown in FIG.

[0076] [Table 4A]

[0077] [Table 4B]

[0078] [Table 5]

[0079] [Table 6]

[0080] [Example 3] FIG. 10 shows a cross-sectional view of the lens configuration and light beam of the imaging optical system of Example 3. The imaging optical system of Example 3 is a zoom lens, and is composed of a first optical system G1 and a second optical system G2, in order from the enlargement side to the reduction side. An intermediate image MI is formed between the first optical system G1 and the second optical system G2. The first optical system G1 is composed of lenses L1a to L1m, in order from the enlargement side to the reduction side. The second optical system G2 is composed of a second A lens group G2A, a second B lens group G2B, and a second C lens group G2C, in order from the enlargement side to the reduction side. During magnification, the second A lens group G2A and the second B lens group G2B move while changing the mutual interval, and the first optical system G1 and the second C lens group G2C are fixed with respect to the image surface. The second A lens group G2A is composed of lenses L2a to L2b, in order from the enlargement side to the reduction side. The second lens group G2B is composed of, in order from the enlargement side to the reduction side, lenses L2c to L2d, an aperture stop St, and lenses L2e to L2i. The second lens group G2C is composed of lens L2j. During focusing, a focus group composed of lenses L1e to L1f moves along the optical axis Z, and the other lenses are fixed with respect to the image plane on the reduction side.

[0081] For the imaging optical system of Example 3, basic lens data is shown in Tables 7A and 7B, specifications and variable surface spacing is shown in Table 8, aspheric coefficients are shown in Table 9, and aberration diagrams for a magnification of 150 times are shown in FIG.

[0082] [Table 7A]

[0083] [Table 7B]

[0084] [Table 8]

[0085] [Table 9]

[0086] [Example 4] FIG. 12 shows a cross-sectional view of the lens configuration and light beam of the imaging optical system of Example 4. The imaging optical system of Example 4 is a zoom lens, and is composed of a first optical system G1 and a second optical system G2, in order from the enlargement side to the reduction side. An intermediate image MI is formed between the first optical system G1 and the second optical system G2. The first optical system G1 is composed of lenses L1a to L1n, in order from the enlargement side to the reduction side. The second optical system G2 is composed of a second A lens group G2A, a second B lens group G2B, and a second C lens group G2C, in order from the enlargement side to the reduction side. During magnification, the second A lens group G2A and the second B lens group G2B move while changing the mutual interval, and the first optical system G1 and the second C lens group G2C are fixed with respect to the image surface. The second A lens group G2A is composed of lenses L2a to L2b, in order from the enlargement side to the reduction side. The second lens group G2B is composed of, in order from the enlargement side to the reduction side, lenses L2c to L2d, an aperture stop St, and lenses L2e to L2j. The second lens group G2C is composed of a lens L2k. During focusing, a focus group composed of lenses L1e to L1f moves along the optical axis Z, and the other lenses are fixed with respect to the image plane on the reduction side.

[0087] Regarding the imaging optical system of Example 4, basic lens data is shown in Tables 10A and 10B, specifications and variable surface spacing is shown in Table 11, aspheric coefficients are shown in Table 12, and aberration diagrams at a magnification of 150 times are shown in FIG.

[0088] [Table 10A]

[0089] [Table 10B]

[0090] [Table 11]

[0091] [Table 12]

[0092] [Example 5] FIG. 14 shows a cross-sectional view of the lens configuration and light beam of the imaging optical system of Example 5. The imaging optical system of Example 5 is a zoom lens, and is composed of a first optical system G1 and a second optical system G2, in order from the enlargement side to the reduction side. An intermediate image MI is formed between the first optical system G1 and the second optical system G2. The first optical system G1 is composed of lenses L1a to L1n, in order from the enlargement side to the reduction side. The second optical system G2 is composed of a second A lens group G2A, a second B lens group G2B, and a second C lens group G2C, in order from the enlargement side to the reduction side. During magnification, the second A lens group G2A and the second B lens group G2B move while changing the mutual interval, and the first optical system G1 and the second C lens group G2C are fixed with respect to the image surface. The second A lens group G2A is composed of lenses L2a to L2b, in order from the enlargement side to the reduction side. The second lens group G2B is composed of, in order from the enlargement side to the reduction side, lenses L2c to L2d, an aperture stop St, and lenses L2e to L2j. The second lens group G2C is composed of a lens L2k. During focusing, a focus group composed of lenses L1e to L1f moves along the optical axis Z, and the other lenses are fixed with respect to the image plane on the reduction side.

[0093] Regarding the imaging optical system of Example 5, basic lens data is shown in Tables 13A and 13B, specifications and variable surface spacing is shown in Table 14, aspheric coefficients are shown in Table 15, and aberration diagrams at a magnification of 150 times are shown in FIG.

[0094] [Table 13A]

[0095] [Table 13B]

[0096] [Table 14]

[0097] [Table 15]

[0098] Table 16 shows values ​​corresponding to conditional expressions (1), (2), and (6) to (9) of the imaging optical systems of Examples 1 to 5, and Table 17 shows numerical values ​​related to the conditional expressions. Tables 16 and 17 show values ​​based on the d line at the wide-angle end. The values ​​shown in Tables 16 and 17 are rounded to a certain number of decimal places.

[0099] [Table 16]

[0100] [Table 17]

[0101] As can be seen from the above data, the imaging optical systems of Examples 1 to 5 have F-numbers of 2.4 or less at the wide-angle end, total angles of view of 130 degrees or more at the wide-angle end, are compact, and have excellent manufacturability and assembleability, while achieving high optical performance with each aberration being well corrected.

[0102] Next, a projection display device according to an embodiment of the present disclosure will be described. FIG. 16 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. 16 includes an imaging optical system 10 according to an embodiment of the present disclosure, a light source 15, transmissive display elements 11a to 11c as light valves corresponding to the respective color lights, dichroic mirrors 12 and 13 for color separation, a cross dichroic prism 14 for color synthesis, condenser lenses 16a to 16c, and total reflection mirrors 18a to 18c for deflecting the optical path. Note that FIG. 16 shows the imaging optical system 10 in a schematic manner. An integrator is disposed between the light source 15 and the dichroic mirror 12, but is omitted from FIG. 16.

[0103] White light from light source 15 is separated into three colored light beams (green light, blue light, 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, where they are modulated, and then color-synthesized by cross dichroic prism 14, before being incident on imaging optical system 10. Imaging optical system 10 projects an optical image formed by the modulated light by transmissive display elements 11a to 11c onto screen 105.

[0104] Fig. 17 is a schematic diagram of a projection display device according to another embodiment of the present disclosure. The projection display device 200 shown in Fig. 17 includes an imaging optical system 210 according to the embodiment of the present disclosure, a light source 215, DMD (Digital Micromirror Device: registered trademark) elements 21a to 21c as light valves corresponding to each color light, TIR (Total Internal Reflection) prisms 24a to 24c for color separation and color synthesis, and a polarizing separation prism 25 for separating illumination light and projection light. Note that Fig. 17 shows the imaging optical system 210 in a schematic manner. An integrator is disposed between the light source 215 and the polarizing separation prism 25, but is not shown in Fig. 17.

[0105] White light from light source 215 is reflected by a reflective surface inside polarization separation prism 25, and then separated into three colored light beams (green light, blue light, and red light) by TIR prisms 24a-24c. Each colored light beam after separation enters corresponding DMD elements 21a-21c and is modulated, travels again in the opposite direction through TIR prisms 24a-24c for color synthesis, and then passes through polarization separation prism 25 and enters imaging optical system 210. Imaging optical system 210 projects an optical image based on the modulated light modulated by DMD elements 21a-21c onto screen 205.

[0106] Fig. 18 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. 18 includes an imaging optical system 310 according to an embodiment of the present disclosure, a light source 315, reflective display elements 31a to 31c as light valves corresponding to the respective color lights, 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 to 35c. Note that Fig. 18 shows the imaging optical system 310 in a schematic manner. An integrator is disposed between the light source 315 and the dichroic mirror 32, but is not shown in Fig. 18.

[0107] White light from the light source 315 is separated into three colored light beams (green light, blue light, and red light) by the dichroic mirrors 32 and 33. Each colored light beam after separation passes through the polarization separation prisms 35a to 35c, enters the reflective display elements 31a to 31c corresponding to each colored light beam, is modulated, is color-synthesized by the cross dichroic prism 34, and then enters the imaging optical system 310. The imaging optical system 310 projects an optical image based on the modulated light by the reflective display elements 31a to 31c onto the screen 305.

[0108] 19 and 20 are external views of a camera 400 which is an imaging device according to an embodiment of the present disclosure. Fig. 19 shows a perspective view of the camera 400 seen from the front side, and Fig. 20 shows a perspective view of the camera 400 seen from the rear side. The camera 400 is a mirrorless single-lens digital camera to which an interchangeable lens 48 is removably attached. The interchangeable lens 48 has an imaging optical system 49 according to an embodiment of the present disclosure housed within a lens barrel.

[0109] Camera 400 includes camera body 41, and a shutter button 42 and a power button 43 are provided on the top surface of camera body 41. In addition, operation units 44, 45, and a display unit 46 are provided on the back surface of camera body 41. Display unit 46 displays a captured image and an image within the angle of view before capture.

[0110] A photographic opening through which light from a subject to be photographed enters is provided in the center of the front surface of camera body 41, and a mount 47 is provided at a position corresponding to the photographic opening, and an interchangeable lens 48 is attached to camera body 41 via mount 47.

[0111] Inside the camera body 41, there are provided an imaging element (not shown) such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) that outputs an imaging signal corresponding to a subject image formed by the interchangeable lens 48, a signal processing circuit (not shown) that processes the imaging signal output from the imaging element to generate an image, and a recording medium (not shown) for recording the generated image. With the camera 400, it is possible to shoot a still image or a video by pressing the shutter button 42, and image data obtained by this shooting is recorded on the recording medium.

[0112] Although the technology of the present disclosure has been described above with reference to the embodiments and examples, the technology of the present disclosure is not limited to the above embodiments and examples, and various modifications are possible. For example, the radius of curvature, surface spacing, refractive index, Abbe number, aspheric coefficient, etc. of each lens are not limited to the values ​​shown in the above numerical examples, and may take other values.

[0113] Furthermore, the projection display device according to the technology of the present disclosure is not limited to the above configuration, and for example, the optical members and light valves used for light beam separation or light beam synthesis can be modified in various ways. The light valve is not limited to a mode 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, and may be a mode in which light itself output from a self-luminous image display element is output as an optical image based on image data. Examples of the self-luminous image display element include an image display element in which light-emitting elements such as LEDs (Light Emitting Diodes) or OLEDs (Organic Light Emitting Diodes) are two-dimensionally arranged.

[0114] Furthermore, the imaging device according to the technique of the present disclosure is not limited to the above configuration, but can take various forms, such as cameras other than mirrorless types, film cameras, video cameras, and cinema cameras. [Explanation of symbols]

[0115] 1, 10, 49, 210, 310 Imaging optical system 2 On-axis luminous flux 3. Luminous flux at maximum image height 4 rays 11a to 11c Transmissive display element 12, 13, 32, 33 Dichroic mirror 14, 34 Cross dichroic prism 15, 215, 315 light source 16a~16c Condenser lenses 18a~18c, 38 Total reflection mirror 21a~21c DMD elements 24a~24c TIR Prism 25, 35a-35c Polarizing beam splitter prism 31a to 31c reflective display element 41 Camera body 42 Shutter button 43 Power button 44, 45 Operation section 46 Display section 47 Mount 48 Interchangeable Lenses 100, 200, 300 Projection display device 105, 205, 305 screens 400 Cameras C1 spherical C2 spherical Cp sphere f focal length G1 1st optical system G2 2nd optical system G2A 2A lens group G2B 2B lens group G2C 2C lens group H1 Height H2 Height Hmax Height L1a~L1n, L2a~L2k lenses LS Specific Lens MI intermediate image Np normal O1 center O2 center OP intersection P point P1 point P2 point PP Optical Components R1 Reflecting mirror R2 Reflecting mirror Ra1 Paraxial radius of curvature Ra2 Paraxial radius of curvature Rbp local radius of curvature SA lens surface Scr Screen Sim image display surface St Aperture Ymax Maximum image height Z optical axis

Claims

1. an imaging optical system including, in order from the enlargement side to the reduction side along an optical path, a first optical system and a second optical system, an intermediate image is formed on an optical path between the first optical system and the second optical system; the first optical system includes at least one aspheric lens; Among the aspherical lenses included in the first optical system, a specific lens that is an aspherical lens closest to the intermediate image on the optical path has a meniscus shape with a convex surface facing a reduction side in a paraxial region, If the distance from the intersection point of the normal and the optical axis at a certain point P on the lens surface to the point P is defined as the local radius of curvature at the point P, and the sign of the local radius of curvature is negative if the intersection point is on the enlargement side of the point P, and positive if the intersection point is on the reduction side of the point P, then the sign of the local radius of curvature at any point within the effective diameter of the reduction-side surface of the specific lens is negative, The maximum image height on the reduction side of the imaging optical system is defined as Ymax, The focal length of the imaging optical system is f, The focal length of the specific lens is fA, The paraxial radius of curvature of the magnification side surface of the specific lens is Ra1, The paraxial radius of curvature of the reduction side surface of the specific lens is Ra2, Rb1 is the local radius of curvature at the intersection between a light ray incident from the reduction-side image plane of the imaging optical system to the imaging optical system parallel to the optical axis at a height of 2.5×|f| from the optical axis and the enlargement-side surface of the specific lens, The local radius of curvature at the intersection of the light ray and the reduction-side surface of the specific lens is Rb2, The height of the light ray from the optical axis on the reduction side surface of the specific lens is H2, When the imaging optical system is a variable magnification optical system, f, Rb1, Rb2, and H2 are the values ​​at the wide-angle end, 2.5≦Ymax / |f|≦2.9 (1) -0.01<|f| / fA<0.025 (2-1) |Ra1|<|Rb1| (3) |Ra2|<|Rb2| (4) |Rb1|<|Rb2| (5) 1.65<|Ra2 / H2|<3 (6) The imaging optical system satisfies the conditional expressions (1), (2-1), (3), (4), (5), and (6) represented by the following formula:

2. -0.1<(1 / Rb1-1 / Rb2)×|f|<-0.015 (7) 2. The imaging optical system according to claim 1, which satisfies conditional expression (7) expressed as follows:

3. The height of the light ray from the optical axis on the magnification side surface of the specific lens is H1, When the imaging optical system is a variable magnification optical system, H1 is the value at the wide-angle end, the enlargement side surface of the specific lens within a radius |H1| from the optical axis is located off the optical axis and on the reduction side of a spherical surface having a radius |Ra1|, a center on the optical axis, and passing through an intersection point between the enlargement side surface of the specific lens and the optical axis; The imaging optical system described in claim 1 or 2, wherein the reduction side surface of the specific lens within a radius |H2| from the optical axis is located off the optical axis, on the reduction side of a spherical surface with a radius of |Ra2|, centered on the optical axis, and passing through the intersection of the reduction side surface of the specific lens and the optical axis.

4. 1.35<|H2 / (2.5×f)|<1.8 (8) 4. The imaging optical system according to claim 1, which satisfies conditional expression (8) represented by:

5. When one lens component is one cemented lens or one single lens, the maximum height among the height from the optical axis of the light ray at two air-contact surfaces intersecting with the optical axis of the lens component on the most reduction side of the first optical system and the height from the optical axis of the light ray at two air-contact surfaces intersecting with the optical axis of the lens component on the most enlargement side of the second optical system is defined as Hmax; When the imaging optical system is a variable magnification optical system, Hmax is the value at the wide-angle end, 1<|Hmax / H2|<1.8 (9) 5. The imaging optical system according to claim 1, which satisfies conditional expression (9) represented by:

6. 6. The imaging optical system according to claim 1, wherein a sign of a local radius of curvature at any point within an effective diameter of the enlargement-side surface of the specific lens is negative.

7. 7. The imaging optical system according to claim 1, further comprising an optical path deflecting member disposed inside the imaging optical system for bending at least one optical path.

8. 8. The imaging optical system according to claim 1, wherein the imaging optical system is a zoom optical system.

9. The imaging optical system according to claim 8 , wherein the second optical system includes a lens group that moves during magnification variation.

10. 10. The imaging optical system according to claim 1, wherein the reduction side is configured to be telecentric.

11. 2.5≦Ymax / |f|≦2.7 (1-1) 2. The imaging optical system according to claim 1, which satisfies the conditional expression (1-1) expressed by:

12. 1.75<|Ra2 / H2|<3 (6-1) 2. The imaging optical system according to claim 1, which satisfies the condition (6-1) expressed by:

13. -0.1<(1 / Rb1-1 / Rb2)×|f|<-0.02 (7-1) 3. The imaging optical system according to claim 2, which satisfies the conditional expression (7-1) expressed by:

14. 1.45<|H2 / (2.5×f)|<1.8 (8-1) 5. The imaging optical system according to claim 4, which satisfies the conditional expression (8-1) expressed by:

15. 1<|Hmax / H2|<1.5 (9-1) 6. The imaging optical system according to claim 5, which satisfies the conditional expression (9-1) expressed by:

16. a light valve for outputting an optical image; and the imaging optical system according to any one of claims 1 to 15, The imaging optical system is a projection display device that projects the optical image output from the light valve onto a screen.

17. An imaging device comprising the imaging optical system according to claim 1 .

Images