Optical system, image projection device, and imaging device

Abstract

An optical system according to the present disclosure is an optical system internally having at least one intermediate image forming position in a conjugate relationship with an enlargement conjugate point on an enlargement side and a reduction conjugate point on a reduction side, and comprises a first sub-optical system and a second sub-optical system that being arranged in order from the enlargement side. The first sub-optical system has a transmission surface closest to the enlargement side and at least one reflection surface. The second sub-optical system is constituted by a plurality of lens elements. The angle of the outermost angle principal light beam with respect to the normal of the transmission surface on the air side of the transmission surface exceeds 65 degrees.

Description

Optical system, image projection device, and imaging device

[0001] The present disclosure relates to an optical system that forms an intermediate image. The present disclosure also relates to an image projection device and an imaging device using such an optical system.

[0002] Patent Document 1 discloses an attachment optical system that is detachably attached to the 3x magnification side of a projection optical system and projects the emitted projection light onto an imaging surface different from the magnification-side imaging surface of the projection optical system. The optical system described in Patent Document 1 has an optical element provided with a second optical axis disposed on the extension of the first optical axis of the projection optical system. The optical element includes an incident surface disposed on the second optical axis, a first reflection surface that reflects the light emitted from the incident surface, a second reflection surface that reflects the light reflected by the first reflection surface, and an exit surface that transmits the light reflected by the second reflection surface. The first reflection surface and the exit surface are continuous within the axial region through which the light passes through the second optical axis and the first optical axis, and the imaging surface of the attachment optical system is substantially parallel to the reduction-side imaging surface on which the light modulation element included in the projection display device forms a projection image.

[0003] Patent Document 2 discloses an optical system that forms an image of an image with an angular field of 90° or more in the vertical direction and an angular field of 180° in the horizontal direction on an image plane. The optical system described in Patent Document 2 consists of a relay optical system and an imaging optical system having positive power. The relay optical system includes a rotationally symmetric transparent medium around a central axis. The transparent medium has at least one inner surface reflecting surface, an incident surface, and an exit surface. Both the inner surface reflecting surface and the refracting surface have a rotationally symmetric shape around the central axis. The optical system described in Patent Document 2 is configured to be imaged at least once within a cross-section including the central axis and not to be imaged within a plane orthogonal to the cross-section and including the central ray of the light beam.

[0004] Japanese Patent Application Laid-Open No. 2022-156602, Patent No. 4451271

[0005] The present disclosure provides an optical system capable of miniaturization while achieving a wider angular field. The present disclosure also provides an image projection device and an imaging device using such an optical system.

[0006] An optical system according to one embodiment of the present disclosure has internally at least one intermediate imaging position that is conjugate to the magnification conjugate point on the magnification side and the reduction conjugate point on the reduction side, and comprises a first sub-optical system and a second sub-optical system arranged in order from the magnification side, wherein the first sub-optical system has the most magnified transmitting surface and at least one reflective surface, and the second sub-optical system is composed of a plurality of lens elements, and the outermost angular principal ray has an angle of more than 65 degrees with respect to the normal of the transmitting surface on the air side of the transmitting surface.

[0007] Furthermore, the image projection device according to this disclosure comprises the optical system and an image forming element that generates an image to be projected onto a screen via the optical system.

[0008] Furthermore, the imaging device according to this disclosure comprises the optical system described above and an image sensor that receives the optical image formed by the optical system and converts it into an electrical image signal.

[0009] According to this disclosure, it is possible to provide an optical system, an image projection device, and an imaging device that can be miniaturized while achieving a wider angle of view.

[0010] Arrangement diagram showing the optical system of Example 1 Explanatory diagram showing an example of how to use the image projection device using the optical system of Example 1 Explanatory diagram showing another example of how to use the image projection device using the optical system of Example 1 Transverse aberration diagram in the optical system of Example 1 Enlarged partial view showing the first sub-optical system in the optical system of Example 1 Arrangement diagram showing the optical system of Example 2 Transverse aberration diagram in the optical system of Example 2 Arrangement diagram showing the optical system of Example 3 Transverse aberration diagram in the optical system of Example 3 Arrangement diagram showing the optical system of Example 4 Transverse aberration diagram in the optical system of Example 4 Arrangement diagram showing the optical system of Example 5 Optics of Example 5 Transverse aberration diagram in the system Arrangement diagram showing the optical system of Example 6 Transverse aberration diagram in the optical system of Example 6 Arrangement diagram showing the optical system of Example 7 Transverse aberration diagram in the optical system of Example 7 Arrangement diagram showing the optical system of Example 8 Transverse aberration diagram in the optical system of Example 8 Arrangement diagram showing the optical system of Example 9 Transverse aberration diagram in the optical system of Example 9 Arrangement diagram showing the optical system of Example 10 Transverse aberration diagram in the optical system of Example 10 Arrangement diagram showing the optical system of Example 11 Transverse aberration diagram in the optical system of Example 11 Block diagram showing an example of an image projection device according to the present disclosure Block diagram showing an example of an imaging device according to the present disclosure

[0011] The embodiments will be described in detail below, with reference to the drawings as appropriate. However, unnecessarily detailed explanations may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art.

[0012] The applicant provides the accompanying drawings and the following description so that a person skilled in the art can fully understand the disclosure, and not to limit the subject matter described in the claims.

[0013] Furthermore, in this specification, terms such as "first," "second," etc., are used solely for descriptive purposes and should not be understood as expressing or implying relative importance or ranking of technical features. Features designated as "first" and "second" express or imply that they include one or more such features.

[0014] The following describes various embodiments of the optical system according to this disclosure. In each embodiment, the case in which the optical system is used in a projector (an example of an image projection device) that projects image light of an original image S, which is obtained by spatially modulating incident light using an image forming element such as a liquid crystal or a DMD (digital micromirror device) based on an image signal, onto a screen will be described. That is, the optical system according to this disclosure can be used to enlarge an original image S on an image forming element located on the reduction side and project it onto a screen by placing a screen (not shown) on the extension of the enlargement side.

[0015] Furthermore, the optical system according to this disclosure can also be used to collect light emitted from an object located on the extension of the magnification side and to form an optical image of the object on the imaging surface of an image sensor located on the reduction side.

[0016] (Embodiment 1) Hereinafter, Embodiment 1 of the present disclosure will be described with reference to Figures 1 to 24.

[0017] Figures 1, 5, 7, 9, 11, 13, 15, 17, 19, 21, and 23 are arrangement diagrams showing the optical system 1 of Examples 1 to 11, respectively. In each figure, the image formation position on the magnification side (i.e., the magnification conjugate point) is located on the right, and the image formation position on the reduction side (i.e., the reduction conjugate point) is located on the left. In each figure, the optical system 1 is shown as viewed from a direction perpendicular to the Y-Z plane (meridional plane), with the optical axis in the Z direction in the X-Y-Z Cartesian coordinate system. In each figure, the straight line drawn on the most reduced side represents the position of the original image S, and the optical elements P are located on the magnification side of the original image S. The optical elements P represent optical elements such as TIR (total internal reflection) prisms, prisms for color separation and color synthesis, optical filters, parallel plate glass, quartz low-pass filters, and infrared cut filters. The optical element P has two parallel and flat transmission surfaces.

[0018] The optical system 1 of Examples 1 to 11 has internally at least one intermediate imaging position that is conjugate to the magnification conjugate point on the magnification side and the reduction conjugate point on the reduction side. Furthermore, the optical system 1 of Examples 1 to 11 includes a first sub-optical system OP1 and a second sub-optical system OP2, in order from the magnification side to the reduction side.

[0019] In the optical system 1 of Examples 1 to 11, the first sub-optical system OP1 has the most magnified transmitting surface and at least one reflective surface. The second sub-optical system OP2 is composed of a plurality of lens elements. In the optical system 1 of Examples 1 to 11, the line connecting the vertices of the plurality of lens elements is defined as the optical axis.

[0020] Figures 2A and 2B are explanatory diagrams showing how to use the image projection device using the optical system 1 of Embodiment 1. The image projection device including the optical system 1 is placed horizontally on a support base such as a table, or on the floor. The screen SC is installed above at a relatively short horizontal distance from the support base, for example, 0.5 m away. The screen SC is a curved surface or multiplane located at the conjugate point on the magnification side. For example, the screen SC is a dome-shaped curved surface. Alternatively, the screen SC is a multiplane composed of multiple planes that intersect each other. Light generated from the optical system 1 is projected diagonally upward and forward, achieving short-focus and large-screen projection. Figures 2A and 2B show an example of rear projection of the optical system 1 of Embodiment 1, but the same applies to the optical systems 1 of Embodiments 2-4 and 6-11. Furthermore, the optical system 1 of Embodiment 5 differs from the optical systems 1 of Embodiments 1-4 and 6-11 in that it projects forward.

[0021] Figures 3, 6, 8, 10, 12, 14, 16, 18, 20, and 22 are transverse aberration diagrams of the optical system 1 of Examples 1 to 11, respectively. In each figure, (A), (B), (C), (D), and (E) show the transverse aberration diagrams of the tangential (meridional) plane and sagittal plane at positions shifted from the center in the Y direction, respectively.

[0022] (Example 1) Figure 1 is a layout diagram showing the optical system 1 according to Example 1. The surface data for Example 1 is shown in the numerical example 1 described later.

[0023] In Example 1, the first sub-optical system OP1 includes a first transmission surface T1, a second transmission surface T2, a first reflection surface R1, a second reflection surface R2, and a third reflection surface R3. In the first sub-optical system OP1, the first transmission surface T1, the first reflection surface R1, the second reflection surface R2, the third reflection surface R3, and the second transmission surface T2 are arranged in order from the magnification side to the reduction side.

[0024] The first transmission surface T1 is positioned on the most magnified side of the first sub-optical system OP1. The first transmission surface T1 has an aspherical shape with its convex side facing the air.

[0025] The second transmission surface T2 is positioned on the reduced side of the first transmission surface T1. Specifically, the second transmission surface T2 is positioned on the most reduced side of the first sub-optical system OP1. The second transmission surface T2 has an aspherical shape with its convex surface facing the air side. Specifically, the second transmission surface T2 has an aspherical shape with its convex surface facing the second sub-optical system OP2 side.

[0026] The first reflective surface R1 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2. The first reflective surface R1 has a convex shape when viewed from the side on which light rays are incident to and reflected by the first reflective surface R1. Specifically, the first reflective surface R1 has an aspherical shape with its convex surface facing the direction in which the light rays incident to the first reflective surface R1 are reflected.

[0027] The second reflective surface R2 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2, and is located on the side of the first reflective surface R1 that is smaller. The second reflective surface R2 has a concave shape when viewed from the side on which light rays are incident on and reflected by the second reflective surface R2. Specifically, the second reflective surface R2 has an aspherical shape with its concave surface facing the direction in which light rays incident on the second reflective surface R2 are reflected.

[0028] The third reflective surface R3 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2, and is located on the narrower side than the second reflective surface R2. The third reflective surface R3 has a concave shape when viewed from the side on which light rays are incident and reflected. Specifically, the third reflective surface R3 has an aspherical shape with its concave surface facing the direction in which light rays incident on the third reflective surface R3 are reflected.

[0029] In Example 1, the first transmission surface T1, the second transmission surface T2, the first reflecting surface R1, the second reflecting surface R2, and the third reflecting surface R3 are formed by a prism PM.

[0030] In Example 1, the second sub-optical system OP2 includes a plurality of lens elements L1 to L8, an aperture ST, and a light cut-off OC. The plurality of lens elements L1 to L8 are arranged in order from the magnification side to the reduction side.

[0031] Lens element L1 has a biconcave shape. Lens element L2 has a positive meniscus shape with the convex surface facing the reduction side. Lens element L3 has a biconvex shape. Lens element L4 has a biconvex shape. Lens element L5 has a biconcave shape. Lens element L6 has a biconvex shape. Lens element L7 has a biconcave shape. Lens element L8 has a biconvex shape.

[0032] The aperture ST is positioned between the reduction conjugate point and the intermediate imaging position MI. The aperture ST is located between lens elements L5 and L6.

[0033] The light-cutting OC is positioned on the magnifying side of the aperture ST. For example, the light-cutting OC cuts out peripheral light. The light-cutting OC is positioned between the aperture ST and the lens element L5.

[0034] In Example 1, the intermediate imaging position MI is located in the first sub-optical system OP1. The intermediate imaging position MI is located inside the prism PM. Specifically, the intermediate imaging position MI is located in the optical path between the third reflective surface R3 and the second transmitting surface T2.

[0035] (Example 2) Figure 5 is a layout diagram showing the optical system 1 according to Example 2. The surface data for Example 2 is shown in the numerical example 2 described later.

[0036] In Example 2, the first sub-optical system OP1 includes a first transmission surface T1, a second transmission surface T2, a first reflection surface R1, a second reflection surface R2, and a third reflection surface R3. In the first sub-optical system OP1, the first transmission surface T1, the first reflection surface R1, the second reflection surface R2, the third reflection surface R3, and the second transmission surface T2 are arranged in order from the magnification side to the reduction side.

[0037] The first transmission surface T1 is positioned on the most magnified side of the first sub-optical system OP1. The first transmission surface T1 has an aspherical shape with its convex side facing the air.

[0038] The second transmission surface T2 is positioned on the reduced side of the first transmission surface T1. Specifically, the second transmission surface T2 is positioned on the most reduced side of the first sub-optical system OP1. The second transmission surface T2 has an aspherical shape with its convex surface facing the air side. Specifically, the second transmission surface T2 has an aspherical shape with its convex surface facing the second sub-optical system OP2 side.

[0039] The first reflecting surface R1 is disposed in the optical path between the first transmitting surface T1 and the second transmitting surface T2. The first reflecting surface R1 has a convex shape when viewed from the side where light rays are incident on and reflected from the first reflecting surface R1. Specifically, the first reflecting surface R1 has an aspherical shape with a convex surface facing in the direction in which the light rays reflected from the first reflecting surface R1 are reflected.

[0040] The second reflecting surface R2 is disposed in the optical path between the first transmitting surface T1 and the second transmitting surface T2, and is disposed on the reducing side with respect to the first reflecting surface R1. The second reflecting surface R2 has a convex shape when viewed from the side where light rays are incident on and reflected from the second reflecting surface R2. Specifically, the second reflecting surface R2 has an aspherical shape with a convex surface facing in the direction in which the light rays reflected from the second reflecting surface R2 are reflected.

[0041] The third reflecting surface R3 is disposed in the optical path between the first transmitting surface T1 and the second transmitting surface T2, and is disposed on the reducing side with respect to the second reflecting surface R2. The third reflecting surface R3 has a concave shape when viewed from the side where light rays are incident on and reflected from the third reflecting surface R3. Specifically, the third reflecting surface R3 has an aspherical shape with a concave surface facing in the direction in which the light rays reflected from the third reflecting surface R3 are reflected.

[0042] In the second embodiment, the first transmitting surface T1, the second transmitting surface T2, the first reflecting surface R1, the second reflecting surface R2, and the third reflecting surface R3 are formed by a prism PM.

[0043] In the second embodiment, the second sub-optical system OP2 includes a plurality of lens elements L1 to L8, an aperture ST, and a light cut OC. The plurality of lens elements L1 to L8 are arranged in order from the enlarging side to the reducing side.

[0044] The lens element L1 has a biconcave shape. The lens element L2 has a positive meniscus shape with a convex surface facing the reducing side. The lens element L3 has a biconvex shape. The lens element L4 has a biconvex shape. The lens element L5 has a biconcave shape. The lens element L6 has a biconvex shape. The lens element L7 has a biconcave shape. The lens element L8 has a biconvex shape.

[0045] The aperture ST is located between the lens element L5 and the lens element L6.

[0046] The light cut OC is disposed between the aperture ST and the lens element L5.

[0047] In the second embodiment, the intermediate imaging position MI is located inside the prism PM of the first sub-optical system OP1. Specifically, the intermediate imaging position MI is located on the optical path between the third reflecting surface R3 and the second transmitting surface T2.

[0048] (Embodiment 3) FIG. 7 is an arrangement diagram showing the optical system 1 according to the third embodiment. The surface data of the third embodiment is shown in the numerical example 3 described later.

[0049] In the third embodiment, the first sub-optical system OP1 includes a first transmitting surface T1, a second transmitting surface T2, a first reflecting surface R1, a second reflecting surface R2, and a third reflecting surface R3. In the first sub-optical system OP1, the first transmitting surface T1, the first reflecting surface R1, the second reflecting surface R2, the third reflecting surface R3, and the second transmitting surface T2 are arranged in order from the magnifying side to the reducing side.

[0050] The first transmitting surface T1 is arranged on the most magnifying side of the first sub-optical system OP1. The first transmitting surface T1 has an aspherical shape with a convex surface facing the air side.

[0051] The second transmitting surface T2 is arranged on the reducing side of the first transmitting surface T1. Specifically, the second transmitting surface T2 is arranged on the most reducing side of the first sub-optical system OP1. The second transmitting surface T2 has an aspherical shape with a convex surface facing the air side. Specifically, the second transmitting surface T2 has an aspherical shape with a convex surface facing the second sub-optical system OP2 side.

[0052] The first reflecting surface R1 is arranged on the optical path between the first transmitting surface T1 and the second transmitting surface T2. The first reflecting surface R1 has a convex shape when viewed from the side where light rays are incident and reflected on the first reflecting surface R1. Specifically, the first reflecting surface R1 has an aspherical shape with a convex surface facing the direction in which the light rays incident on the first reflecting surface R1 are reflected.

[0053] The second reflecting surface R2 is arranged on the optical path between the first transmitting surface T1 and the second transmitting surface T2, and is arranged on the reducing side of the first reflecting surface R1. The second reflecting surface R2 has a concave shape when viewed from the side where light rays are incident and reflected on the second reflecting surface R2. Specifically, the second reflecting surface R2 has an aspherical shape with a concave surface facing the direction in which the light rays incident on the second reflecting surface R2 are reflected.

[0054] The third reflective surface R3 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2, and is located on the narrower side than the second reflective surface R2. The third reflective surface R3 has a concave shape when viewed from the side on which light rays are incident and reflected. Specifically, the third reflective surface R3 has an aspherical shape with its concave surface facing the direction in which light rays incident on the third reflective surface R3 are reflected.

[0055] In Example 3, the first transmission surface T1, the second transmission surface T2, the first reflective surface R1, the second reflective surface R2, and the third reflective surface R3 are formed by a prism PM.

[0056] In Example 3, the second sub-optical system OP2 includes a plurality of lens elements L1 to L8, an aperture ST, and a light cut-off OC. The plurality of lens elements L1 to L8 are arranged in order from the magnification side to the reduction side.

[0057] Lens element L1 has a biconcave shape. Lens element L2 has a positive meniscus shape with its convex surface facing the reduction side. Lens element L3 has a biconvex shape. Lens element L4 has a positive meniscus shape with its convex surface facing the reduction side. Lens element L5 has a biconcave shape. Lens element L6 has a biconvex shape. Lens element L7 has a negative meniscus shape with its convex surface facing the reduction side. Lens element L8 has a biconvex shape.

[0058] The aperture ST is located between lens element L5 and lens element L6.

[0059] The light-cutting OC is positioned between the aperture ST and the lens element L5.

[0060] In Example 3, the intermediate imaging position MI is located inside the prism PM of the first sub-optical system OP1. Specifically, the intermediate imaging position MI is located in the optical path between the third reflective surface R3 and the second transmitting surface T2.

[0061] (Example 4) Figure 9 is a layout diagram showing the optical system 1 according to Example 4. The surface data for Example 4 is shown in the numerical example 4 described later.

[0062] In Example 4, the first sub-optical system OP1 includes a first transmission surface T1, a second transmission surface T2, a first reflection surface R1, a second reflection surface R2, and a third reflection surface R3. In the first sub-optical system OP1, the first transmission surface T1, the first reflection surface R1, the second reflection surface R2, the third reflection surface R3, and the second transmission surface T2 are arranged in order from the magnification side to the reduction side.

[0063] The first transmission surface T1 is positioned on the most magnified side of the first sub-optical system OP1. The first transmission surface T1 has an aspherical shape with its convex side facing the air.

[0064] The second transmission surface T2 is positioned on the reduced side of the first transmission surface T1. Specifically, the second transmission surface T2 is positioned on the most reduced side of the first sub-optical system OP1. The second transmission surface T2 has an aspherical shape with its concave surface facing the air side. Specifically, the second transmission surface T2 has an aspherical shape with its concave surface facing the second sub-optical system OP2 side.

[0065] The first reflective surface R1 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2. The first reflective surface R1 has a convex shape when viewed from the side on which light rays are incident to and reflected by the first reflective surface R1. Specifically, the first reflective surface R1 has an aspherical shape with its convex surface facing the direction in which the light rays incident to the first reflective surface R1 are reflected.

[0066] The second reflective surface R2 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2, and is located on the side of the first reflective surface R1 that is smaller. The second reflective surface R2 has a concave shape when viewed from the side on which light rays are incident on and reflected by the second reflective surface R2. Specifically, the second reflective surface R2 has an aspherical shape with its concave surface facing the direction in which light rays incident on the second reflective surface R2 are reflected.

[0067] The third reflective surface R3 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2, and is located on the narrower side than the second reflective surface R2. The third reflective surface R3 has a concave shape when viewed from the side on which light rays are incident and reflected. Specifically, the third reflective surface R3 has an aspherical shape with its concave surface facing the direction in which light rays incident on the third reflective surface R3 are reflected.

[0068] In Example 4, the first transmissive surface T1, the second transmissive surface T2, the first reflective surface R1, the second reflective surface R2, and the third reflective surface R3 are formed by a prism PM.

[0069] In Example 4, the second sub-optical system OP2 includes a plurality of lens elements L1 to L9, an aperture ST, and a light cut-off OC. The plurality of lens elements L1 to L9 are arranged in order from the magnification side to the reduction side.

[0070] Lens element L1 has a negative meniscus shape with its convex surface facing the magnification side. Lens element L2 has a biconvex shape. Lens element L3 has a biconvex shape. Lens element L4 has a biconvex shape. Lens element L5 has a biconvex shape. Lens element L6 has a negative meniscus shape with its convex surface facing the reduction side. Lens element L7 has a biconvex shape. Lens element L8 has a negative meniscus shape with its convex surface facing the reduction side. Lens element L9 has a biconvex shape.

[0071] The aperture ST is located between lens elements L6 and L7.

[0072] The light-cutting OC is positioned between the aperture ST and the lens element L6.

[0073] In Embodiment 4, the first intermediate imaging position MI1 and the second intermediate imaging position MI2 are located within the optical system 1. The first intermediate imaging position MI1 is located inside the prism PM of the first sub-optical system OP1. Specifically, the first intermediate imaging position MI1 is located in the optical path between the third reflective surface R3 and the second transmissive surface T2. The second intermediate imaging position MI2 is located within the second sub-optical system OP2. Specifically, the second intermediate imaging position MI2 is located in the optical path between lens element L3 and lens element L4.

[0074] (Example 5) Figure 11 is a layout diagram showing the optical system 1 according to Example 5. The surface data for Example 5 is shown in the numerical example 5 described later.

[0075] In Example 5, the first sub-optical system OP1 includes a first transmission surface T1, a second transmission surface T2, a first reflection surface R1, and a second reflection surface R2. In the first sub-optical system OP1, the first transmission surface T1, the first reflection surface R1, the second reflection surface R2, and the second transmission surface T2 are arranged in order from the magnification side to the reduction side.

[0076] The first transmission surface T1 is positioned on the most magnified side of the first sub-optical system OP1. The first transmission surface T1 has an aspherical shape with its convex side facing the air.

[0077] The second transmission surface T2 is positioned on the reduced side of the first transmission surface T1. Specifically, the second transmission surface T2 is positioned on the most reduced side of the first sub-optical system OP1. The second transmission surface T2 has an aspherical shape with its convex surface facing the air side. Specifically, the second transmission surface T2 has an aspherical shape with its convex surface facing the second sub-optical system OP2 side.

[0078] The first reflective surface R1 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2. The first reflective surface R1 has a convex shape when viewed from the side on which light rays are incident to and reflected by the first reflective surface R1. Specifically, the first reflective surface R1 has an aspherical shape with its convex surface facing the direction in which the light rays incident to the first reflective surface R1 are reflected.

[0079] The second reflective surface R2 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2, and is located on the side of the first reflective surface R1 that is smaller. The second reflective surface R2 has a concave shape when viewed from the side on which light rays are incident on and reflected by the second reflective surface R2. Specifically, the second reflective surface R2 has an aspherical shape with its concave surface facing the direction in which light rays incident on the second reflective surface R2 are reflected.

[0080] In Example 5, the first transmission surface T1, the second transmission surface T2, the first reflective surface R1, and the second reflective surface R2 are formed by a prism PM.

[0081] In Example 5, the second sub-optical system OP2 includes a plurality of lens elements L1 to L8, an aperture ST, and a light cut-off OC. The plurality of lens elements L1 to L8 are arranged in order from the magnification side to the reduction side.

[0082] Lens element L1 has a biconcave shape. Lens element L2 has a biconvex shape. Lens element L3 has a biconvex shape. Lens element L4 has a positive meniscus shape with the convex surface facing the magnification side. Lens element L5 has a biconcave shape. Lens element L6 has a biconvex shape. Lens element L7 has a negative meniscus shape with the convex surface facing the reduction side. Lens element L8 has a biconvex shape.

[0083] The aperture ST is located between lens element L5 and lens element L6.

[0084] The light-cutting OC is positioned between the aperture ST and the lens element L5.

[0085] In Example 5, the intermediate imaging position MI is located inside the prism PM of the first sub-optical system OP1. Specifically, the intermediate imaging position MI is located in the optical path between the second reflective surface R2 and the second transmissive surface T2.

[0086] (Example 6) Figure 13 is a layout diagram showing the optical system 1 according to Example 6. The surface data for Example 6 will be shown in the numerical example 6 described later.

[0087] In Example 6, the first sub-optical system OP1 includes a first transmission surface T1, a second transmission surface T2, and a reflection surface R1. In the first sub-optical system OP1, the first transmission surface T1, the reflection surface R1, and the second transmission surface T2 are arranged in order from the magnification side to the reduction side.

[0088] The first transmission surface T1 is positioned on the most magnified side of the first sub-optical system OP1. The first transmission surface T1 has an aspherical shape with its convex side facing the air.

[0089] The second transmission surface T2 is positioned on the reduced side of the first transmission surface T1. Specifically, the second transmission surface T2 is positioned on the most reduced side of the first sub-optical system OP1. The second transmission surface T2 has an aspherical shape with its convex surface facing the air side. Specifically, the second transmission surface T2 has an aspherical shape with its convex surface facing the second sub-optical system OP2 side.

[0090] The reflective surface R1 is positioned in the optical path between the first transmitting surface T1 and the second transmitting surface T2. The reflective surface R1 has a concave shape when viewed from the side from which light rays are incident on and reflected by the reflective surface R1. Specifically, the first reflective surface R1 has an aspherical shape with its concave surface facing the direction in which light rays incident on the first reflective surface R1 are reflected.

[0091] In Example 6, the first transmission surface T1, the second transmission surface T2, and the reflective surface R1 are formed by a prism PM. Furthermore, the first transmission surface T1 and the second transmission surface T2 are superimposed in a plane of the same curvature.

[0092] In Example 6, the second sub-optical system OP2 includes a plurality of lens elements L1 to L10, an aperture ST, and a light cut OC. The plurality of lens elements L1 to L10 are arranged in order from the magnification side to the reduction side.

[0093] Lens element L1 has a negative meniscus shape with a convex surface on the magnification side. Lens element L2 has a positive meniscus shape with a convex surface facing the reduction side. Lens element L3 has a biconcave shape. Lens element L4 has a biconvex shape. Lens element L5 has a positive meniscus shape with a convex surface on the magnification side. Lens element L6 has a biconcave shape. Lens element L7 has a biconvex shape. Lens element L8 has a biconcave shape. Lens element L9 has a positive meniscus shape with a convex surface facing the reduction side. Lens element L10 has a positive meniscus shape with a convex surface facing the reduction side.

[0094] The aperture ST is located between lens elements L6 and L7.

[0095] The light-cutting OC is positioned between the aperture ST and the lens element L6.

[0096] In Example 6, the intermediate imaging position MI is located inside the prism PM of the first sub-optical system OP1. Specifically, the intermediate imaging position MI is located in the optical path between the reflective surface R1 and the second transmitting surface T2.

[0097] (Example 7) Figure 15 is a layout diagram showing the optical system 1 according to Example 7. The surface data for Example 7 is shown in the numerical example 7 described later.

[0098] In Example 7, the first sub-optical system OP1 includes a lens element L1, a first transmissive surface T1, a second transmissive surface T2, a first reflective surface R1, a second reflective surface R2, and a third reflective surface R3. In the first sub-optical system OP1, the lens element L1, the first transmissive surface T1, the first reflective surface R1, the second reflective surface R2, the third reflective surface R3, and the second transmissive surface T2 are arranged in order from the magnification side to the reduction side.

[0099] The lens element L1 is positioned on the most magnified side of the first sub-optical system OP1. The lens element L1 has a negative meniscus shape with a convex surface on the magnified side. The magnified side surface T0 of the lens element L1 is the transmission surface located on the most magnified side in the optical system 1.

[0100] The first transmissive surface T1 is positioned on the shrinking side of the lens element L1. The first transmissive surface T1 has an aspherical shape with its convex side facing the air. Specifically, the first transmissive surface T1 has an aspherical shape with its convex side facing the lens element L1.

[0101] The second transmission surface T2 is positioned on the reduced side of the first transmission surface T1. Specifically, the second transmission surface T2 is positioned on the most reduced side of the first sub-optical system OP1. The second transmission surface T2 has an aspherical shape with its convex surface facing the air side. Specifically, the second transmission surface T2 has an aspherical shape with its convex surface facing the second sub-optical system OP2 side.

[0102] The first reflective surface R1 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2. The first reflective surface R1 has a convex shape when viewed from the side on which light rays are incident to and reflected by the first reflective surface R1. Specifically, the first reflective surface R1 has an aspherical shape with its convex surface facing the direction in which the light rays incident to the first reflective surface R1 are reflected.

[0103] The second reflective surface R2 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2, and is located on the side of the first reflective surface R1 that is smaller. The second reflective surface R2 has a concave shape when viewed from the side on which light rays are incident on and reflected by the second reflective surface R2. Specifically, the second reflective surface R2 has an aspherical shape with its concave surface facing the direction in which light rays incident on the second reflective surface R2 are reflected.

[0104] The third reflective surface R3 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2, and is located on the narrower side than the second reflective surface R2. The third reflective surface R3 has a concave shape when viewed from the side on which light rays are incident and reflected. Specifically, the third reflective surface R3 has an aspherical shape with its concave surface facing the direction in which light rays incident on the third reflective surface R3 are reflected.

[0105] In Example 7, the first transmission surface T1, the second transmission surface T2, the first reflective surface R1, the second reflective surface R2, and the third reflective surface R3 are formed by a prism PM.

[0106] In Example 7, the second sub-optical system OP2 includes a plurality of lens elements L2 to L9, an aperture ST, and a light cut OC. The plurality of lens elements L2 to L9 are arranged in order from the magnification side to the reduction side.

[0107] Lens element L2 has a biconcave shape. Lens element L3 has a positive meniscus shape with the convex surface facing the reduction side. Lens element L4 has a biconvex shape. Lens element L5 has a positive meniscus shape with the convex surface facing the reduction side. Lens element L6 has a biconcave shape. Lens element L7 has a biconvex shape. Lens element L8 has a negative meniscus shape with the convex surface facing the reduction side. Lens element L9 has a biconvex shape.

[0108] The aperture ST is located between lens elements L6 and L7.

[0109] The light-cutting OC is positioned between the aperture ST and the lens element L6.

[0110] In Example 7, the intermediate imaging position MI is located inside the prism PM of the first sub-optical system OP1. Specifically, the intermediate imaging position MI is located in the optical path between the third reflective surface R3 and the second transmitting surface T2.

[0111] (Example 8) Figure 17 is a layout diagram showing the optical system 1 according to Example 8. The surface data for Example 8 is shown in the numerical example 8 described later.

[0112] In Example 8, the first sub-optical system OP1 includes a lens element L1, a first transmission surface T1, a second transmission surface T2, and a reflective surface R1. In the first sub-optical system OP1, the lens element L1, the first transmission surface T1, the reflective surface R1, and the second transmission surface T2 are arranged in order from the magnification side to the reduction side.

[0113] The lens element L1 is positioned on the most magnified side of the first sub-optical system OP1. The lens element L1 has a negative meniscus shape with a convex surface on the magnified side. The lens element L1 is shared by both the first sub-optical system OP1 and the second sub-optical system OP2. The magnified side surface T0 of the lens element L1 is the transmission surface located on the most magnified side in the optical system 1.

[0114] The first transmission surface T1 is positioned on the reduced side of the lens element L1 in the first sub-optical system OP1. The first transmission surface T1 has an aspherical shape with its convex surface facing the air side. Specifically, the first transmission surface T1 has an aspherical shape with its convex surface facing the lens element L1 side.

[0115] The second transmission surface T2 is positioned on the reduced side of the first transmission surface T1. Specifically, the second transmission surface T2 is positioned on the most reduced side of the first sub-optical system OP1. The second transmission surface T2 has an aspherical shape with its convex surface facing the air side. Specifically, the second transmission surface T2 has an aspherical shape with its convex surface facing the second sub-optical system OP2 side.

[0116] The reflective surface R1 is positioned in the optical path between the first transmitting surface T1 and the second transmitting surface T2. The reflective surface R1 has a concave shape when viewed from the side from which light rays are incident on and reflected by the reflective surface R1. Specifically, the reflective surface R1 has an aspherical shape with its concave surface facing the direction in which the light rays incident on the reflective surface R1 are reflected.

[0117] In Example 7, the first transmission surface T1, the second transmission surface T2, and the reflective surface R1 are formed by a prism PM.

[0118] In Example 7, the second sub-optical system OP2 includes a plurality of lens elements L1 to L8 and an aperture ST. The plurality of lens elements L1 to L8 are arranged in order from the magnification side to the reduction side.

[0119] The lens element L1 is positioned on the most magnified side of the second sub-optical system OP2. The lens element L1 is located on the most magnified side of the first sub-optical system OP1, and is also located on the most magnified side of the second sub-optical system OP2.

[0120] Lens element L2 has a biconcave shape. Lens element L3 has a positive meniscus shape with the convex surface facing the reduction side. Lens element L4 has a biconvex shape. Lens element L5 has a biconcave shape. Lens element L6 has a biconvex shape. Lens element L7 has a negative meniscus shape with the convex surface facing the reduction side. Lens element L8 has a biconvex shape.

[0121] The aperture ST is located between lens elements L6 and L7.

[0122] In Example 8, the intermediate imaging position MI is located inside the prism PM of the first sub-optical system OP1. Specifically, the intermediate imaging position MI is located in the optical path between the reflective surface R1 and the second transmitting surface T2.

[0123] (Example 9) Figure 19 is a layout diagram showing the optical system 1 according to Example 9. The surface data for Example 9 will be shown in the numerical example 9 described later.

[0124] In Example 9, the first sub-optical system OP1 includes a lens element L1, a first reflective surface R1, a second reflective surface R2, and a third reflective surface R3. In the first sub-optical system OP1, the lens element L1, the first reflective surface R1, the second reflective surface R2, and the third reflective surface R3 are arranged in order from the magnification side to the reduction side.

[0125] The lens element L1 is positioned on the most magnified side of the first sub-optical system OP1. The lens element L1 has a negative meniscus shape with a convex surface on the magnified side. The magnified side surface T0 of the lens element L1 is the transmission surface located on the most magnified side in the optical system 1.

[0126] The first reflective surface R1 is positioned on the side smaller than the lens element L1. The first reflective surface R1 has a convex shape when viewed from the side on which light rays are incident on and reflected by the first reflective surface R1. Specifically, the first reflective surface R1 has an aspherical shape with its convex surface facing the direction in which light rays incident on the first reflective surface R1 are reflected.

[0127] The second reflective surface R2 is positioned on the side smaller than the first reflective surface R1. The second reflective surface R2 has a concave shape when viewed from the side on which light rays are incident and reflected. Specifically, the second reflective surface R2 has an aspherical shape with its concave surface facing the direction in which light rays incident on the second reflective surface R2 are reflected.

[0128] The third reflective surface R3 is positioned on the smaller side than the second reflective surface R2 and is located on the most compact side of the first sub-optical system OP1. The third reflective surface R3 has a concave shape when viewed from the side on which light rays are incident and reflected. Specifically, the third reflective surface R3 has an aspherical shape with its concave surface facing the direction in which light rays incident on the third reflective surface R3 are reflected.

[0129] In Example 9, the first reflective surface R1, the second reflective surface R2, and the third reflective surface R3 are each formed from mirrors.

[0130] In Example 9, the second sub-optical system OP2 includes a plurality of lens elements L2 to L9, an aperture ST, and a light cut OC. The plurality of lens elements L2 to L9 are arranged in order from the magnification side to the reduction side.

[0131] Lens element L2 has a biconcave shape. Lens element L3 has a positive meniscus shape with the convex surface facing the reduction side. Lens element L4 has a biconvex shape. Lens element L5 has a positive meniscus shape with the convex surface facing the reduction side. Lens element L6 has a biconcave shape. Lens element L7 has a biconvex shape. Lens element L8 has a negative meniscus shape with the convex surface facing the reduction side. Lens element L9 has a biconvex shape.

[0132] The aperture ST is located between lens elements L6 and L7.

[0133] The light-cutting OC is positioned between the aperture ST and the lens element L6.

[0134] In Example 9, the intermediate imaging position MI is located between the first sub-optical system OP1 and the second sub-optical system OP2. Specifically, the intermediate imaging position MI is located in the optical path between the third reflective surface R3 and the lens element L2.

[0135] (Example 10) Figure 21 is a layout diagram showing the optical system 1 according to Example 10. The surface data for Example 10 is shown in the numerical example 10 described later.

[0136] In Example 10, the first sub-optical system OP1 includes a first transmission surface T1, a second transmission surface T2, a first reflection surface R1, a second reflection surface R2, and a third reflection surface R3. In the first sub-optical system OP1, the first transmission surface T1, the first reflection surface R1, the second reflection surface R2, the third reflection surface R3, and the second transmission surface T2 are arranged in order from the magnification side to the reduction side.

[0137] The first transmission surface T1 is positioned on the most magnified side of the first sub-optical system OP1. The first transmission surface T1 has an aspherical shape with its convex side facing the air.

[0138] The second transmission surface T2 is positioned on the most reduced side of the first sub-optical system OP1. The second transmission surface T2 has an aspherical shape with its convex surface facing the air side. Specifically, the second transmission surface T2 has an aspherical shape with its convex surface facing the second sub-optical system OP2 side.

[0139] The first transmission surface T1 and the second transmission surface T2 are superimposed within a plane of the same curvature. Specifically, the first transmission surface T1 and the second transmission surface T2 are formed on the same plane. That is, the first transmission surface T1, located on the most magnified side of the first sub-optical system OP1, is shared as the second transmission surface T2, located on the most reduced side of the first sub-optical system OP1.

[0140] The first reflective surface R1 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2. The first reflective surface R1 has a concave shape when viewed from the side from which light rays are incident on and reflected by the first reflective surface R1. Specifically, the first reflective surface R1 has an aspherical shape with its concave surface facing the direction in which light rays incident on the first reflective surface R1 are reflected.

[0141] The second reflective surface R2 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2, and is located on the side of the first reflective surface R1 that is smaller. The second reflective surface R2 has a concave shape when viewed from the side on which light rays are incident on and reflected by the second reflective surface R2. Specifically, the second reflective surface R2 has an aspherical shape with its concave surface facing the direction in which light rays incident on the second reflective surface R2 are reflected.

[0142] The third reflective surface R3 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2, and is located on the side of the narrower path than the second reflective surface R2. The third reflective surface R3 has a concave shape when viewed from the side on which light rays are incident and reflected. Specifically, the third reflective surface R3 has an aspherical shape with its concave surface facing the direction in which light rays incident on the third reflective surface R3 are reflected.

[0143] In Example 10, the first transmission surface T1, the second transmission surface T2, the first reflecting surface R1, the second reflecting surface R2, and the third reflecting surface R3 are formed by a prism PM.

[0144] In Example 10, the second sub-optical system OP2 includes a plurality of lens elements L1 to L9, an aperture ST, and a light cut-off OC. The plurality of lens elements L1 to L9 are arranged in order from the magnification side to the reduction side.

[0145] Lens element L1 has a biconvex shape. Lens element L2 has a biconvex shape. Lens element L3 has a positive meniscus shape with the convex surface facing the magnification side. Lens element L4 has a negative meniscus shape with the convex surface facing the magnification side. Lens element L5 has a negative meniscus shape with the convex surface facing the reduction side. Lens element L6 has a biconvex shape. Lens element L7 has a biconcave shape. Lens element L8 has a biconvex shape. Lens element L9 has a positive meniscus shape with the convex surface facing the reduction side.

[0146] The aperture ST is located between lens element L5 and lens element L6.

[0147] The light-cutting OC is positioned between the aperture ST and the lens element L5.

[0148] In Example 10, the first intermediate imaging position MI1 and the second intermediate imaging position MI2 are located within the optical system 1. The first intermediate imaging position MI1 is located inside the prism PM of the first sub-optical system OP1. Specifically, the first intermediate imaging position MI1 is located in the optical path between the first reflective surface R1 and the second reflective surface R2. The second intermediate imaging position MI2 is located between the first sub-optical system OP1 and the second sub-optical system OP2. Specifically, the second intermediate imaging position MI2 is located in the optical path between the second transmission surface T2 of the prism PM and the lens element L2 of the second sub-optical system OP2, and is closer to the second transmission surface T2 than to the lens element L2.

[0149] (Example 11) Figure 23 is a layout diagram showing the optical system 1 according to Example 11. The surface data for Example 11 is shown in the numerical example 11 described later.

[0150] In Example 11, the first sub-optical system OP1 includes a first transmission surface T1, a second transmission surface T2, a first reflection surface R1, a second reflection surface R2, and a third reflection surface R3. In the first sub-optical system OP1, the first transmission surface T1, the first reflection surface R1, the second reflection surface R2, the third reflection surface R3, and the second transmission surface T2 are arranged in order from the magnification side to the reduction side.

[0151] The first transmission surface T1 is positioned on the most magnified side of the first sub-optical system OP1. The first transmission surface T1 has an aspherical shape with its convex side facing the air.

[0152] The second transmission surface T2 is positioned on the most reduced side of the first sub-optical system OP1. The second transmission surface T2 has an aspherical shape with its convex surface facing the air side. Specifically, the second transmission surface T2 has an aspherical shape with its convex surface facing the second sub-optical system OP2 side.

[0153] The first transmission surface T1 and the second transmission surface T2 are superimposed within a plane of the same curvature. Specifically, the first transmission surface T1 and the second transmission surface T2 are formed on the same plane. That is, the first transmission surface T1, located on the most magnified side of the first sub-optical system OP1, is shared as the second transmission surface T2, located on the most reduced side of the first sub-optical system OP1.

[0154] The first reflective surface R1 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2. The first reflective surface R1 has a concave shape when viewed from the side from which light rays are incident on and reflected by the first reflective surface R1. Specifically, the first reflective surface R1 has an aspherical shape with its concave surface facing the direction in which light rays incident on the first reflective surface R1 are reflected.

[0155] The second reflective surface R2 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2, and is located on the side of the first reflective surface R1 that is smaller. The second reflective surface R2 has a convex shape when viewed from the side on which light rays are incident on and reflected by the second reflective surface R2. Specifically, the second reflective surface R2 has an aspherical shape with its convex surface facing the direction in which light rays incident on the second reflective surface R2 are reflected.

[0156] The third reflective surface R3 is positioned in the optical path between the first transmissive surface T1 and the second transmissive surface T2, and is located on the side of the narrower path than the second reflective surface R2. The third reflective surface R3 has a concave shape when viewed from the side on which light rays are incident and reflected. Specifically, the third reflective surface R3 has an aspherical shape with its concave surface facing the direction in which light rays incident on the third reflective surface R3 are reflected.

[0157] In Example 11, the first transmission surface T1, the second transmission surface T2, the first reflective surface R1, the second reflective surface R2, and the third reflective surface R3 are formed by a prism PM.

[0158] In Example 10, the second sub-optical system OP2 includes a plurality of lens elements L1 to L9, an aperture ST, and a light cut-off OC. The plurality of lens elements L1 to L9 are arranged in order from the magnification side to the reduction side.

[0159] Lens element L1 has a positive meniscus shape with its convex surface facing the reduction side. Lens element L2 has a biconvex shape. Lens element L3 has a positive meniscus shape with its convex surface facing the magnification side. Lens element L4 has a positive meniscus shape with its convex surface facing the magnification side. Lens element L5 has a biconcave shape. Lens element L6 has a biconvex shape. Lens element L7 has a negative meniscus shape with its convex surface facing the reduction side. Lens element L8 has a positive meniscus shape with its convex surface facing the reduction side. Lens element L9 has a biconvex shape.

[0160] The aperture ST is located between lens element L5 and lens element L6.

[0161] The light-cutting OC is positioned between the aperture ST and the lens element L5.

[0162] In Example 11, the first intermediate imaging position MI1 and the second intermediate imaging position MI2 are located within the prism PM of the first sub-optical system OP1. Specifically, the first intermediate imaging position MI1 is located in the optical path between the first reflective surface R1 and the second reflective surface R2. The second intermediate imaging position MI2 is located in the optical path between the third reflective surface R3 and the second transmission surface T2.

[0163] Next, the conditions that the optical system 1 according to this disclosure can satisfy will be explained. Note that multiple conditions are defined for the optical system according to each embodiment, and it is possible to satisfy all of these conditions, or to satisfy individual conditions to obtain the corresponding effects.

[0164] The optical system 1 according to Examples 1 to 11 is an optical system having at least one intermediate imaging position that is conjugate to the magnification conjugate point on the magnification side and the reduction conjugate point on the reduction side, and comprises a first sub-optical system OP1 and a second sub-optical system OP2 arranged in order from the magnification side. The first sub-optical system OP1 has the most magnified transmitting surface and at least one reflective surface. The second sub-optical system OP2 is composed of a plurality of lens elements. The outermost angular principal ray has an angle of more than 65 degrees with respect to the normal of the transmitting surface on the air side of the most magnified transmitting surface.

[0165] Referring to Figure 4, the outermost principal ray in the optical system 1 according to Embodiment 1 will be described in detail. Figure 4 is a magnified partial view showing the first sub-optical system in the optical system of Embodiment 1. In Figure 4, for clarity, the outermost principal ray is shown with a solid line, and the other rays are shown with dashed lines.

[0166] As shown in Figure 4, the outermost principal ray occurs at the air side of the first transmission surface T1, where the angle θ1 with respect to the normal of the first transmission surface T1 exceeds 65 degrees.

[0167] This configuration enables miniaturization while achieving a wide-angle view. For example, it allows for a field of view with a half-angle exceeding 100 degrees, and enables smaller lens elements and / or prisms. Furthermore, it allows projection onto a dome-shaped curved surface or multiple planes.

[0168] In Examples 2-6 and 10-11, the most magnified transmitting surface is the first transmitting surface T1 of the prism PM, while in Examples 7-9, the most magnified surface is the magnified surface of the lens element L1.

[0169] Furthermore, in the optical system 1 according to Examples 1 to 3, 7 and 9, the first sub-optical system OP1 may have, in order from the magnification side, first transmission surfaces T0, T1, first reflection surface R1, second reflection surface R2, third reflection surface R3 and second transmission surface T2. When the optical axis connecting the vertices of the multiple lens elements is defined as the Z direction, and the direction perpendicular to the Z direction is defined as the Y direction, the intermediate imaging position MI may be located in the first sub-optical system OP1 or between the first sub-optical system OP1 and the second sub-optical system OP2 when viewed from a direction perpendicular to the Y-Z plane. The reflection angle θ2 of the outermost principal ray at the first reflection surface R1 may exceed 65 degrees.

[0170] This configuration allows for wide-angle projection while reducing the size of the first sub-optical system OP1, enabling projection or photography to the back. Furthermore, by increasing the angle to the refractive surface, the reflection angle to other reflective surfaces is reduced, suppressing the occurrence of aberrations such as field curvature. Aberrations such as field curvature caused by shape errors of the reflective surfaces can also be suppressed. In addition, distortion can be more easily corrected to equidistant projection.

[0171] Furthermore, in the optical system 1 according to Examples 1 to 3, 7 and 9, the reflection angle θ3 of the outermost principal ray at the second reflective surface R2 is 48 degrees or more.

[0172] This configuration allows for a wider angle of view while reducing the size of the first sub-optical system OP1.

[0173] Furthermore, the optical system 1 according to Examples 1 to 3, 7 and 9 may satisfy the following condition (1): 0.02 < YR2 / YR1 < 0.10 ... (1) where, YR1: the distance between the principal ray of the ray closest to the optical axis OA on the first reflecting surface R1 and the outermost principal ray in a direction perpendicular to the optical axis. YR2: the distance between the principal ray of the ray closest to the optical axis OA on the second reflecting surface R2 and the outermost principal ray in a direction perpendicular to the optical axis.

[0174] This configuration allows for a wider angle while reducing the size of the first sub-optical system OP1. However, if YR1 / YR2 is 0.10 or greater, the first sub-optical system OP1 becomes larger, and if YR1 / YR2 is 0.02 or less, widening the angle becomes difficult.

[0175] Furthermore, the optical system 1 according to Examples 1 to 3, 7 and 9 may satisfy the following condition (2): 0.1 < T12 / T2S < 0.5 ... (2) where, T2S: the distance between the most enlarged and most reduced surfaces of the second sub-optical system OP2 T12: the distance between the most reduced surface of the first sub-optical system OP1 and the most enlarged surface of the second sub-optical system OP2.

[0176] This configuration allows for a wider angle of view while miniaturizing the optical system 1. However, if T12 / T2S is 0.5 or greater, the lens elements interfere at the minimum angle of view, and if T12 / T2S is 0.1 or less, the overall length of the optical system 1 increases, making it larger.

[0177] Furthermore, in the optical system 1 according to Examples 1 to 3, 7 and 9, the second sub-optical system OP2 may have an aperture ST. The plurality of lens elements of the second sub-optical system OP2 may be composed of spherical lenses on the magnifying side of the aperture ST, and may include aspherical lenses on the reducing side of the aperture ST.

[0178] This configuration allows for efficient correction of aberrations, such as field curvature, without increasing the size of the aspherical surface.

[0179] Furthermore, in the optical system 1 according to Examples 1 to 3, 7 and 9, when viewed from a direction perpendicular to the Y-Z plane, all the luminous beams of the light rays closest to the optical axis may pass through one side with respect to the optical axis at the second transmission surface T2 and the third reflection surface R3, or through the other side with respect to the optical axis at the second reflection surface R2, the first reflection surface R1 and the first transmission surfaces T0, T1.

[0180] This configuration allows for correction of field curvature and reduces the size of the first sub-optical system OP1.

[0181] Furthermore, the optical system 1 according to Examples 1 to 3 and 7 may also satisfy the following condition (3): -4 < RC1 / RC3 < -1 ... (3) where, RC1: Principal radius of curvature of the first reflective surface R1 RC3: Principal radius of curvature of the third reflective surface R3.

[0182] This configuration allows for a wider angle while miniaturizing the optical system 1. However, if RC1 / RC3 is -1.0 or higher, widening the angle becomes difficult, and if RC1 / RC3 is -4 or lower, the first sub-optical system OP1 becomes larger.

[0183] Furthermore, in the optical system 1 according to Examples 1 to 3, 7 and 9, the first transmission surfaces T0 and T1 may have a convex shape toward the air side. The first reflection surface R1 may have a convex shape when viewed from the side on which light rays are incident on and reflected by the first reflection surface R1. The third reflection surface R3 may have a concave shape when viewed from the side on which light rays are incident on and reflected by the third reflection surface R3.

[0184] This configuration allows for correction of field curvature and reduces the size of the first sub-optical system OP1.

[0185] Furthermore, in the optical system 1 according to Examples 10 and 11, the first sub-optical system OP1 may have a first transmission surface T1, a first reflection surface R1, a second reflection surface R2, a third reflection surface R3, and a second transmission surface T2 in order from the magnification side. When the optical axis connecting the vertices of the multiple lens elements is defined as the Z direction, and the direction perpendicular to the Z direction is defined as the Y direction, when viewed from a direction perpendicular to the Y-Z plane, there may be a first intermediate imaging position MI1 and a second intermediate imaging position MI2 in order from the magnification side. The first intermediate imaging position MI1 is located within the first sub-optical system OP1 and may be conjugate to the conjugate point on the magnification side and the second intermediate imaging position MI2. The second intermediate imaging position MI2 is located within the first sub-optical system OP1 or between the first sub-optical system OP1 and the second sub-optical system OP2, and may be conjugate to the conjugate point on the reduction side and the first intermediate imaging position MI1.

[0186] This configuration allows for wider angle projection, a smaller first sub-optical system OP1, and projection or photography onto the back.

[0187] Furthermore, in the optical system 1 according to Examples 10 and 11, the first transmission surface T1 and the second transmission surface T2 may overlap in at least a portion of a plane having the same curvature.

[0188] This configuration allows the first sub-optical system OP1 to be made smaller.

[0189] Furthermore, the optical systems 1 according to Examples 10 and 11 may satisfy the following condition (4): 0.3 < T12 / T2S < 1.5 ... (4) where, T2S: the distance between the most enlarged and most retracted surfaces of the second sub-optical system OP2, and T12: the distance between the most retracted surface of the first sub-optical system OP1 and the most enlarged surface of the second sub-optical system OP2.

[0190] This configuration allows for a wider angle of view while miniaturizing the optical system 1. However, if T12 / T2S is 0.3 or greater, the lens elements interfere at the minimum angle of view, and if T12 / T2S is 1.5 or less, the overall length of the optical system 1 increases, making it larger.

[0191] Furthermore, in the optical system 1 according to Examples 10 and 11, the reflection angle of the outermost principal ray may be 20° or more and 35° or less on each of the surfaces of the third reflective surface R3, the second reflective surface R2, and the first reflective surface.

[0192] This configuration allows for a wider angle of view while reducing the size of the first sub-optical system OP1.

[0193] Furthermore, in the optical system 1 according to Examples 10 and 11, when viewed from a direction perpendicular to the Y-Z plane, all the rays closest to the optical axis pass through one side with respect to the optical axis at the second transmission surface T2, the first transmission surface T1, and the third reflection surface R3, and pass through the other side with respect to the optical axis at the second reflection surface R2 and the first reflection surface R1.

[0194] This configuration allows for correction of field curvature and reduces the size of the first sub-optical system OP1.

[0195] Furthermore, the optical system 1 according to Examples 10 and 11 may satisfy the following condition (5): 0.5 < RC1 / RC3 < 1.5 ... (5) where, RC1: Principal radius of curvature of the first reflective surface R1 RC3: Principal radius of curvature of the third reflective surface R3.

[0196] This configuration allows for a wider angle while miniaturizing the optical system 1. However, if RC1 / RC3 is 1.5 or greater, widening the angle becomes difficult, and if RC1 / RC3 is 0.5 or less, the first sub-optical system OP1 becomes larger.

[0197] Furthermore, in the optical system 1 according to Examples 10 and 11, the first transmission surface T1 may have a convex shape when viewed from the air side. The first reflection surface R1 may have a concave shape when viewed from the side on which light rays are incident to and reflected by the first reflection surface R1. The third reflection surface R3 may have a concave shape when viewed from the side on which light rays are incident to and reflected by the third reflection surface R3. The second transmission surface T2 may have a convex shape when viewed from the air side.

[0198] This configuration allows for correction of field curvature and reduces the size of the first sub-optical system OP1.

[0199] Furthermore, in the optical system 1 according to Example 8, the first sub-optical system OP1 has a lens element L1 located on the most magnified side. The lens element L1 located on the most magnified side of the first sub-optical system OP1 is shared as the lens element located on the most magnified side of the second sub-optical system OP2.

[0200] With this configuration, a lens that is rotationally symmetric with respect to the optical axis can be used as the lens element L1 that magnifies the image the most, making it easier to hold the lens element L1.

[0201] The optical system 1 according to this disclosure projects an image onto a plurality of planes or curved surfaces located at the conjugate points on the magnification side.

[0202] This configuration allows images to be projected onto multiple flat or curved surfaces.

[0203] (Numerical Example 1) For the optical system of Numerical Example 1 (corresponding to Example 1), surface data is shown in Table 1, aspherical shape data is shown in Table 2, and various other data are shown in Table 3.

[0204]

[0205]

[0206]

[0207] (Numerical Example 2) For the optical system of Numerical Example 2 (corresponding to Example 2), surface data is shown in Table 4, aspherical shape data is shown in Table 5, and various other data are shown in Table 6.

[0208]

[0209]

[0210]

[0211] (Numerical Example 3) For the optical system of Numerical Example 3 (corresponding to Example 3), surface data is shown in Table 7, aspherical shape data is shown in Table 8, zoom data is shown in Table 9, and various other data is shown in Table 10.

[0212]

[0213]

[0214]

[0215]

[0216] (Numerical Example 4) For the optical system of Numerical Example 4 (corresponding to Example 4), surface data is shown in Table 11, aspherical shape data is shown in Table 12, and various other data are shown in Table 13.

[0217]

[0218]

[0219]

[0220] (Numerical Example 5) For the optical system of Numerical Example 5 (corresponding to Example 5), surface data is shown in Table 14, aspherical shape data is shown in Table 15, zoom data is shown in Table 16, and various other data is shown in Table 17.

[0221]

[0222]

[0223]

[0224]

[0225] (Numerical Example 6) For the optical system of Numerical Example 6 (corresponding to Example 6), surface data is shown in Table 18, aspherical shape data is shown in Table 19, and various other data are shown in Table 20.

[0226]

[0227]

[0228]

[0229] (Numerical Example 7) For the optical system of Numerical Example 7 (corresponding to Example 7), surface data is shown in Table 21, aspherical shape data is shown in Table 22, zoom data is shown in Table 23, and various other data is shown in Table 24.

[0230]

[0231]

[0232]

[0233]

[0234] (Numerical Example 8) For the optical system of Numerical Example 8 (corresponding to Example 8), surface data is shown in Table 25, aspherical shape data is shown in Table 26, and various other data are shown in Table 27.

[0235]

[0236]

[0237]

[0238] (Numerical Example 9) For the optical system of Numerical Example 9 (corresponding to Example 9), surface data is shown in Table 28, aspherical shape data is shown in Table 29, and various other data are shown in Table 30.

[0239]

[0240]

[0241]

[0242] (Numerical Example 10) For the optical system of Numerical Example 10 (corresponding to Example 10), surface data is shown in Table 31, aspherical shape data is shown in Table 32, and various other data are shown in Table 33.

[0243]

[0244]

[0245]

[0246] (Numerical Example 11) For the optical system of Numerical Example 11 (corresponding to Example 11), surface data is shown in Table 34, aspherical shape data is shown in Table 35, and various other data are shown in Table 36.

[0247]

[0248]

[0249]

[0250] Table 37 shows the conditions in optical system 1 for numerical examples 1 to 11 (corresponding to examples 1 to 11).

[0251]

[0252] In Table 37, the "first transmission surface incidence angle" is the angle θ1 of the outermost principal ray with respect to the normal of the transmission surface on the air side of the most magnified transmission surface. The "first reflection surface reflection angle" is the reflection angle θ2 of the outermost principal ray at the first reflection surface. The "second reflection surface reflection angle" is the reflection angle θ3 of the outermost principal ray at the second reflection surface. The "third reflection surface reflection angle" is the reflection angle of the outermost principal ray at the third reflection surface.

[0253] (Embodiment 2) Hereinafter, Embodiment 2 of the present disclosure will be described with reference to Figure 25. Figure 25 is a block diagram showing an example of an image projection device according to the present disclosure. The image projection device 100 includes the optical system 1 disclosed in Embodiment 1, an image forming element 101, a light source 102, a control unit 110, etc. The image forming element 101 is composed of liquid crystal, DMD, etc., and generates an image to be projected onto the screen SC via the optical system 1. The light source 102 is composed of an LED (light-emitting diode), laser, etc., and supplies light to the image forming element 101. The control unit 110 is composed of a CPU or MPU, etc., and controls the entire device and each component. The optical system 1 may be configured as an interchangeable lens that can be detachably attached to the image projection device 100. In this case, the device obtained by removing the optical system 1 from the image projection device 100 is an example of the main device.

[0254] The image projection device 100 described above, with the optical system 1 according to Embodiment 1, can achieve a wide-angle zoom function while reducing costs.

[0255] (Embodiment 3) Hereinafter, Embodiment 3 of the present disclosure will be described with reference to Figure 26. Figure 26 is a block diagram showing an example of an imaging device according to the present disclosure. The imaging device 200 includes the optical system 1 disclosed in Embodiment 1, an image sensor 201, a control unit 210, etc. The image sensor 201 is composed of a CCD (charge-coupled device) image sensor, a CMOS image sensor, etc., and receives the optical image of an object OBJ formed by the optical system 1 and converts it into an electrical image signal. The control unit 110 is composed of a CPU or MPU, etc., and controls the entire device and each component. The optical system 1 may be configured as an interchangeable lens that can be detachably attached to the imaging device 200. In this case, the device obtained by removing the optical system 1 from the imaging device 200 is an example of the main device.

[0256] The imaging device 200 described above, with the optical system 1 according to Embodiment 1, can achieve a wide-angle zoom function while reducing costs.

[0257] As described above, embodiments have been explained as part of the technical disclosure in this disclosure. For this purpose, accompanying drawings and a detailed description have been provided.

[0258] Therefore, the components described in the attached drawings and detailed descriptions may include not only components essential for solving the problem, but also components that are not essential for solving the problem, provided that they illustrate the technology described above. For this reason, the mere presence of such non-essential components in the attached drawings or detailed descriptions should not be immediately assumed to mean that these non-essential components are essential.

[0259] Furthermore, since the embodiments described above are for illustrative purposes of the technology described herein, various modifications, substitutions, additions, omissions, etc., can be made within the scope of the claims or their equivalents.

[0260] This disclosure is applicable to image projection devices such as projectors and head-up displays, and imaging devices such as digital still cameras, digital video cameras, surveillance cameras in surveillance systems, webcams, and in-vehicle cameras. In particular, this disclosure is applicable to optical systems that require high image quality, such as projectors, digital still camera systems, and digital video camera systems.

[0261] 1. Optical system: L1-L10 (lens element), R1-R3 (reflecting surface), T0-T2 (transmitting surface), ST (aperture), OA (optical axis), OC (light cut-off), P (optical element), PM (prism), S (original image).

Claims

1. An optical system having at least one intermediate imaging position that is conjugate to the magnification conjugate point on the magnification side and the reduction conjugate point on the reduction side, comprising a first sub-optical system and a second sub-optical system arranged in order from the magnification side, wherein the first sub-optical system has a transmission surface on the magnification side and at least one reflective surface, the second sub-optical system is composed of a plurality of lens elements, and the outermost angular principal ray has an angle of more than 65 degrees with respect to the normal of the transmission surface on the air side of the transmission surface.

2. The optical system according to claim 1, wherein the first sub-optical system has, in order from the magnifying side, a first transmissive surface, a first reflective surface, a second reflective surface, a third reflective surface, and a second transmissive surface, and the optical axis connecting the vertices of the plurality of lens elements is defined as the Z direction, and the direction perpendicular to the Z direction is defined as the Y direction, and when viewed from a direction perpendicular to the Y-Z plane, the intermediate imaging position is located between the first sub-optical system or between the first sub-optical system and the second sub-optical system, and the reflection angle of the outermost principal ray at the first reflective surface exceeds 65 degrees.

3. The optical system according to claim 2, wherein the reflection angle of the outermost principal ray at the second reflective surface is 48 degrees or more.

4. The optical system according to claim 2 or 3, satisfying the following condition (1): 0.02 < YR2 / YR1 < 0.10 ... (1) where, YR1: the distance between the principal ray of the ray closest to the optical axis on the first reflecting surface and the outermost principal ray in a direction perpendicular to the optical axis. YR2: the distance between the principal ray of the ray closest to the optical axis on the second reflecting surface and the outermost principal ray in a direction perpendicular to the optical axis.

5. An optical system according to any one of claims 2 to 4 that satisfies the following condition (2): 0.1 < T12 / T2S < 0.5 ... (2) where, T2S: the distance between the most enlarged surface and the most retracted surface of the second sub-optical system T12: the distance between the most retracted surface of the first sub-optical system and the most enlarged surface of the second sub-optical system.

6. The optical system according to any one of claims 2 to 5, wherein the second sub-optical system has an aperture, and the plurality of lens elements of the second sub-optical system are composed of spherical lenses on the magnifying side of the aperture and include aspherical lenses on the reducing side of the aperture.

7. The optical system according to any one of claims 2 to 6, wherein, when viewed from a direction perpendicular to the Y-Z plane, all the luminous beams of the rays closest to the optical axis pass through one side of the optical axis at the second transmitting surface and the third reflecting surface, and pass through the other side of the optical axis at the second reflecting surface, the first reflecting surface and the first transmitting surface.

8. An optical system according to any one of claims 2 to 7 that satisfies the following condition (3): -4 < RC1 / RC3 < -1 ... (3) where, RC1: the principal radius of curvature of the first reflecting surface RC3: the principal radius of curvature of the third reflecting surface.

9. The optical system according to any one of claims 2 to 8, wherein the first transmitting surface has a convex shape toward the air side, the first reflecting surface has a convex shape when viewed from the side on which light rays are incident on and reflected by the first reflecting surface, and the third reflecting surface has a concave shape when viewed from the side on which light rays are incident on and reflected by the third reflecting surface.

10. The optical system according to claim 1, wherein the first sub-optical system has, in order from the magnification side, a first transmission surface, a first reflection surface, a second reflection surface, a third reflection surface, and a second transmission surface, and the optical axis connecting the vertices of the plurality of lens elements is defined as the Z direction, and the direction perpendicular to the Z direction is defined as the Y direction, and when viewed from a direction perpendicular to the Y-Z plane, there are, in order from the magnification side, a first intermediate imaging position and a second intermediate imaging position, the first intermediate imaging position is located within the first sub-optical system and is conjugate to the conjugate point on the magnification side and the second intermediate imaging position, and the second intermediate imaging position is located within the first sub-optical system or between the first sub-optical system and the second sub-optical system and is conjugate to the conjugate point on the reduction side and the first intermediate imaging position.

11. The optical system according to claim 10, wherein at least a portion of the first transmission surface and the second transmission surface overlap in a plane of the same curvature.

12. The optical system according to claim 10 or 11, satisfying the following condition (4): 0.3 < T12 / T2S < 1.5 ... (4) where, T2S: the distance between the most enlarged and most retracted surfaces of the second sub-optical system T12: the distance between the most retracted surface of the first sub-optical system and the most enlarged surface of the second sub-optical system.

13. The optical system according to any one of claims 10 to 12, wherein the reflection angle of the outermost principal ray is 20° or more and 35° or less on each of the reflection angles of the third reflective surface, the second reflective surface, and the first reflective surface.

14. The optical system according to any one of claims 10 to 13, wherein, when viewed from a direction perpendicular to the Y-Z plane, all rays of light closest to the optical axis pass through one side of the optical axis at the second transmitting surface, the first transmitting surface, and the third reflecting surface, and pass through the other side of the optical axis at the second reflecting surface and the first reflecting surface.

15. An optical system according to any one of claims 10 to 14 that satisfies the following condition (5): 0.5 < RC1 / RC3 < 1.5 ... (5) where, RC1: the principal radius of curvature of the first reflecting surface RC3: the principal radius of curvature of the third reflecting surface.

16. The optical system according to any one of claims 10 to 15, wherein the first transmitting surface has a convex shape when viewed from the air side, the first reflecting surface has a concave shape when viewed from the side on which light rays are incident on and reflected from the first reflecting surface, the third reflecting surface has a concave shape when viewed from the side on which light rays are incident on and reflected from the third reflecting surface, and the second transmitting surface has a convex shape when viewed from the air side.

17. The optical system according to claim 1, wherein the first sub-optical system has a lens element located on the most magnified side, and the lens element located on the most magnified side of the first sub-optical system is shared as the lens element located on the most magnified side of the second sub-optical system.

18. The optical system according to any one of claims 1 to 17, wherein the optical system projects an image onto a plurality of planes or curved surfaces located at the conjugate points on the magnification side.

19. An image projection device comprising: an optical system according to any one of claims 1 to 18; and an image forming element that generates an image to be projected onto a screen via the optical system.

20. An imaging device comprising: an optical system according to any one of claims 1 to 18; and an image sensor that receives an optical image formed by the optical system and converts it into an electrical image signal.

Images