Optical system, image projection device, and imaging device

Abstract

An optical system according to the present disclosure comprises a first sub-optical system and a second sub-optical system that are arranged in order from the reduction side to the enlargement side. The first sub-optical system includes a plurality of lenses that are rotationally symmetric with respect to an optical axis, and the second sub-optical system includes at least two reflection surfaces each having a concave surface. There are a first intermediate image position, a second intermediate image position, and a third intermediate image position in order from the reduction side to the enlargement side. Principal rays having different image heights intersect each other twice between a maximum enlargement-side surface and a maximum reduction-side surface of the first sub-optical system. The first intermediate image position is located in the first sub-optical system, and is a conjugate point on the reduction side and a conjugate point of a second intermediate image. The second intermediate image position is located in the second sub-optical system, and is a conjugate point of a first intermediate image and a conjugate point of a third intermediate image. The third intermediate image position is located further toward the enlargement side than the second intermediate image position in the second sub-optical system, and is a conjugate point of the second intermediate image and a conjugate point on the enlargement side.

Description

Optical system, image projection device and imaging device

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

[0002] Patent Document 1 discloses a compact optical system with low flare and high resolution for capturing images with a 360° omnidirectional (all-around) angle of view or projecting images across a 360° omnidirectional (all-around) angle of view. The optical system described in Patent Document 1 includes a front group having two reflective surfaces that are rotationally symmetric about a central axis, and a rear group that is rotationally symmetric about the central axis and has positive power. The optical system includes a first reflective surface located on the opposite side of the entrance pupil and a second reflective surface located on the opposite side of the first reflective surface, and an entrance pupil in a cross section including the central axis is located between the outer peripheries of the first reflective surface and the second reflective surface. A light beam incident from a distant object passes through the front group and the rear group in order to form an image at a position off the central axis of the image plane. In a cross section including the central axis, the entrance pupil is located away from the central axis, and in a plane perpendicular to the plane including the central axis and including the central ray of the light beam, the entrance pupil is located on the central axis. The rear group is composed of at least two groups.

[0003] Patent Document 2 discloses a projection optical system that projects image light generated by modulating a light beam emitted from a light source. The projection optical system described in Patent Document 2 includes a first lens system having a positive refractive power overall and refracting the generated image light, a first reflective optical system having two or more reflective surfaces that fold and reflect the image light refracted by the first lens system, a second lens system having a positive refractive power overall and refracting the image light reflected by the first reflective optical system, and a second reflective optical system having a concave reflective surface that reflects the image light refracted by the second lens system toward a projection target.

[0004] JP 2007-328232 A International Publication No. 2019 / 012795

[0005] The present disclosure provides an optical system that can suppress distortion at a wide angle while increasing peripheral light intensity, and also provides an image projection device and an imaging device that use such an optical system.

[0006] An optical system according to one aspect of the present disclosure includes a first sub-optical system and a second sub-optical system arranged in order from a reduction side to an enlargement side, the first sub-optical system including a plurality of lenses that are rotationally symmetric about an optical axis, the second sub-optical system including at least two reflective surfaces having concave surfaces, and when the optical axis is defined as a Z direction and a direction orthogonal to the Z direction is defined as a Y direction, when viewed from a direction perpendicular to a Y-Z plane, there are a first intermediate imaging position, a second intermediate imaging position, and a third intermediate imaging position in order from the reduction side to the enlargement side, and when viewed from a direction perpendicular to the Y-Z plane, the first sub-optical system Chief rays of different image heights intersect twice between the most enlarged surface and the most reduced surface, the first intermediate imaging position is located within the first sub-optical system and is a conjugate point of the reduction side and a conjugate point of the second intermediate imaging at the second intermediate imaging position, the second intermediate imaging position is located within the second sub-optical system and is a conjugate point of the first intermediate imaging at the first intermediate imaging position and a conjugate point of the third intermediate imaging at the third intermediate imaging position, and the third intermediate imaging position is located on the enlargement side of the second intermediate imaging position within the second sub-optical system and is a conjugate point of the second intermediate imaging and a conjugate point of the enlargement side.

[0007] An image projection device according to the present disclosure includes the above optical system and an image forming element that generates an image to be projected onto a screen via the optical system.

[0008] An imaging device according to the present disclosure includes the optical system described above and an imaging element that receives an optical image formed by the optical system and converts it into an electrical image signal.

[0009] According to the optical system according to the present disclosure, it is possible to increase the amount of peripheral light while suppressing distortion at a wide angle.

[0010] Layout diagram showing the optical system of Example 1. Explanatory diagram showing a usage mode of an image projection device using the optical system of Example 1. Longitudinal aberration diagram in the optical system of Example 1. Lateral aberration diagram in the optical system of Example 1. Partially enlarged view showing an enlarged view of the most enlarged side of the first sub-optical system in the optical system of Example 1. Partially enlarged view showing an enlarged view of the second sub-optical system in the optical system of Example 1. Layout diagram showing the optical system of Example 2. Longitudinal aberration diagram in the optical system of Example 2. Lateral aberration diagram in the optical system of Example 2. Layout diagram showing the optical system of Example 3. Longitudinal aberration diagram in the optical system of Example 3. Lateral aberration diagram in the optical system of Example 3. Partially enlarged view showing an enlarged view of the second sub-optical system in the optical system of Example 3. Layout diagram showing the optical system of Example 4. Longitudinal aberration diagram in the optical system of Example 4. Lateral aberration diagram in the optical system of Example 4. Layout diagram showing the optical system of Example 5. Layout diagram showing the optical system of Example 6. 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] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of well-known matters or redundant explanation of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art.

[0012] The applicant provides the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and does not intend for them to limit the subject matter described in the claims.

[0013] Additionally, the terms "first," "second," etc., used herein are for descriptive purposes only and should not be understood as expressing or implying relative importance or ranking of technical features. Features qualified as "first" and "second" expressly or imply the inclusion of one or more of the feature.

[0014] Below, various embodiments of the optical system according to the present disclosure will be described. In each embodiment, a case will be described 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. That is, the optical system according to the present disclosure can be used to enlarge and project the original image S on an image forming element arranged on the reduction side by placing a screen (not shown) on an extension of the enlargement side.

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

[0016] First Embodiment Hereinafter, a first embodiment of the present disclosure will be described with reference to FIGS.

[0017] FIGS. 1, 7, 10, 14, 17, and 18 are layout diagrams showing the optical system 1 of Examples 1 to 6, respectively. In each diagram, the magnification-side imaging position (i.e., the magnification conjugate point) is located on the left, and the reduction-side imaging position (i.e., the reduction conjugate point) is located on the right. Each diagram shows the layout of the optical system 1 as viewed from a direction perpendicular to the Y-Z plane (meridional plane), with the optical axis OA in the Z direction in an X-Y-Z orthogonal coordinate system. For clarity, each diagram shows the chief ray passing through the center of the original image S in the X direction and the lowest point in the Y direction (normalized height Y = 0.0 at the reduction conjugate point), and the chief ray passing through the center of the original image S in the X direction and the highest point in the Y direction (normalized height Y = 1.0 at the reduction conjugate point). In each diagram, the straight line drawn on the most reduced side represents the position of the original image S, and the optical element P is located on the magnification side of the original image S. The optical element P represents an optical element such as a TIR (total internal reflection) prism, a prism for color separation or color synthesis, an optical filter, a parallel plate glass, a quartz low-pass filter, an infrared cut filter, etc. The optical element P has two parallel and flat transmitting surfaces.

[0018] The optical system 1 of Examples 1 to 6 includes, in order from the reduction side to the magnification side, a first sub-optical system OP1 and a second sub-optical system OP2. Here, the most magnification-side surface of the first sub-optical system OP1 is the refractive surface that is closest to the reduction side across air from the most reduction-side reflective surface. The most reduction-side surface of the first sub-optical system OP1 is located closer to the reduction side than the most magnification-side surface, and is the reduction-side surface of the lens that has the most power on the reduction side.

[0019] In the optical system 1 of Examples 1 to 6, the first sub-optical system OP1 includes a plurality of lens elements L1 to L10 that are rotationally symmetric about the optical axis OA, and a stop ST. The second sub-optical system OP2 includes at least two reflective surfaces each having a concave surface.

[0020] In addition, in the optical system 1 of Examples 1 to 6, a first intermediate imaging position MI1, a second intermediate imaging position MI2, and a third intermediate imaging position MI3 are formed in that order from the reduction side to the enlargement side, and chief rays of different image heights intersect twice between the surface on the most enlarged side and the surface on the most reduced side of the first sub-optical system OP1.

[0021] The first intermediate image position MI1 is formed within the first sub-optical system OP1. The first intermediate image position MI1 is a position where the first intermediate image is formed, and is a conjugate point on the reduction side and a conjugate point of the second intermediate image formed at the second intermediate image position MI2.

[0022] The second intermediate imaging position MI2 and the third intermediate imaging position MI3 are formed within the second sub-optical system OP2. The second intermediate imaging position MI2 is a position where the second intermediate image is formed, and is a conjugate point of the first intermediate image at the first intermediate imaging position MI1 and a conjugate point of the third intermediate image at the third intermediate imaging position. The third intermediate imaging position MI3 is a position where the third intermediate image is formed, and is located on the magnification side of the second intermediate imaging position MI2 within the second sub-optical system OP2, and is a conjugate point of the second intermediate image and the magnification side.

[0023] FIG. 2 is an explanatory diagram showing a usage mode of an image projection device using the optical system 1 of Example 1. The image projection device including the optical system 1 is placed horizontally on a support stand such as a table or on the floor. A screen SC is installed vertically above the support stand at a relatively short horizontal distance, for example, 0.5 m. The screen SC is a single plane located at the conjugate point on the magnification side. Light generated from the optical system 1 is projected obliquely upward and forward, achieving a short-focus, large-screen projection. Note that while FIG. 2 shows an example of forward projection using the optical system 1 of Example 1, the same applies to the optical system 1 of Example 3. Furthermore, the optical systems 1 of Examples 2 and 4 differ from the optical systems 1 of Examples 1 and 3 in that they perform rear projection.

[0024] 3, 8, 11, and 15 are longitudinal aberration diagrams for the optical systems 1 of Examples 1 to 4, respectively. In each diagram, (A), (B), and (C) respectively show spherical aberration diagrams, astigmatism diagrams, and distortion diagrams. In the spherical aberration diagrams, the horizontal axis represents spherical aberration (mm), and the vertical axis represents F-number (indicated by F in the diagrams). In the spherical aberration diagrams, the solid line represents the d-line, the short dashed line represents the F-line, and the long dashed line represents the C-line characteristics. In the astigmatism diagrams, the horizontal axis represents astigmatism (mm), and the vertical axis represents image height. In the astigmatism diagrams, the solid line represents the sagittal plane characteristics, and the dashed line represents the meridional plane characteristics. In the distortion diagrams, the horizontal axis represents distortion (%), and the vertical axis represents image height.

[0025] 4, 9, 12, and 16 are lateral aberration diagrams for the optical systems 1 of Examples 1 to 4. In each diagram, (A), (B), (C), (D), and (E) respectively show lateral aberration diagrams for the tangential (meridional) plane and the sagittal plane at positions shifted from the center in the Y direction.

[0026] 1 is a layout diagram showing an optical system 1 according to Example 1. Surface data of Example 1 will be shown in Numerical Example 1, which will be described later.

[0027] In the first embodiment, the first sub-optical system OP1 includes a plurality of lens elements L1 to L10 and a diaphragm ST.

[0028] In the first sub-optical system OP1, multiple lens elements L1 to L10 are arranged in order from the magnification side to the reduction side. Lens element L1 has a biconvex shape. Lens element L2 has a positive meniscus shape with a convex surface facing the magnification side. Lens element L3 has a negative meniscus shape with a convex surface facing the magnification side. Lens element L4 has a biconvex shape. Lens element L5 has a biconvex shape. Lens element L6 has a positive meniscus shape with a convex surface facing the magnification side. Lens element L7 has a biconvex shape. Lens element L8 has a negative meniscus shape with a convex surface facing the reduction side. Lens element L9 has a positive meniscus shape with a convex surface facing the reduction side. Lens element L10 has a biconvex shape.

[0029] The stop ST is positioned between the reduction conjugate point and the first intermediate image position MI1. The stop ST is located between the lens element L6 and the lens element L7.

[0030] The second sub-optical system OP2 includes a first reflecting surface R1 and a second reflecting surface R2. In the second sub-optical system OP2, the first reflecting surface R1 and the second reflecting surface R2 are arranged in this order from the magnification side to the reduction side.

[0031] The first reflecting surface R1 is disposed on the most magnified side of the second sub-optical system OP2. The first reflecting surface R1 has an aspheric shape with a concave surface facing in the direction in which the light ray incident on the first reflecting surface R1 is reflected.

[0032] The second reflecting surface R2 is disposed on the most reduction side of the second sub-optical system OP2. The second reflecting surface R2 has an aspheric shape with a concave surface facing in the direction in which the light ray incident on the second reflecting surface R2 is reflected.

[0033] Air exists in the optical path between the first reflecting surface R1 and the second reflecting surface R2, and this configuration can increase the transmittance.

[0034] As an example, the first reflecting surface R1 and the second reflecting surface R2 are formed by mirrors.

[0035] The first intermediate imaging position MI1 is formed in the optical path between the lens element L4 and the lens element L6 in the first sub-optical system OP1. The second intermediate imaging position MI2 is formed in the optical path between the lens element L1 and the first reflecting surface R1 in the second sub-optical system OP2. The third intermediate imaging position MI3 is formed in the optical path between the first reflecting surface R1 and the second reflecting surface R2 in the second sub-optical system OP2.

[0036] In the first sub-optical system OP1, the chief ray intersects between the lens element L6 and the lens element L7, and between the lens element L3 and the lens element L5.

[0037] 7 is a layout diagram showing an optical system 1 according to Example 2. Surface data of Example 2 will be shown in Numerical Example 2, which will be described later.

[0038] In the second embodiment, the first sub-optical system OP1 includes a plurality of lens elements L1 to L9 and a diaphragm ST.

[0039] In the first sub-optical system OP1, multiple lens elements L1 to L9 are arranged in order from the magnification side to the reduction side. Lens element L1 has a biconvex shape. Lens element L2 has a positive meniscus shape with a convex surface facing the magnification side. Lens element L3 has a positive meniscus shape with a convex surface facing the reduction side. Lens element L4 has a biconvex shape. Lens element L5 has a positive meniscus shape with a convex surface facing the magnification side. Lens element L6 has a positive meniscus shape with a convex surface facing the reduction side. Lens element L7 has a biconcave shape. Lens element L8 has a biconvex shape. Lens element L9 has a biconvex shape.

[0040] The aperture stop ST is disposed on the enlargement side surface of the lens element L6.

[0041] The second sub-optical system OP2 includes a first reflecting surface R1, a second reflecting surface R2, and a third reflecting surface R3. In the second sub-optical system OP2, the first reflecting surface R1 to the third reflecting surface R3 are arranged in order from the magnification side to the reduction side.

[0042] The first reflecting surface R1 is disposed on the most magnified side of the second sub-optical system OP2. The first reflecting surface R1 has an aspheric shape with a concave surface facing in the direction in which the light ray incident on the first reflecting surface R1 is reflected.

[0043] The second reflecting surface R2 is disposed between the first reflecting surface R1 and the third reflecting surface R3. The second reflecting surface R2 reflects the light reflected by the third reflecting surface R3 toward the first reflecting surface R1. The second reflecting surface R2 has a shape with a concave surface facing in the direction in which the light incident on the second reflecting surface R2 is reflected.

[0044] The third reflecting surface R3 is disposed on the most reduction side of the second sub-optical system OP2. The third reflecting surface R3 has an aspheric shape with a concave surface facing in the direction in which the light ray incident on the third reflecting surface R3 is reflected.

[0045] Air exists in the optical path between the first reflecting surface R1 and the third reflecting surface R3, and this configuration can increase the transmittance.

[0046] As an example, the first reflecting surface R1, the second reflecting surface R2, and the third reflecting surface R3 are formed by mirrors.

[0047] The first intermediate imaging position MI1 is formed in the optical path between the lens element L3 and the lens element L4 in the first sub-optical system OP1. The second intermediate imaging position MI2 is formed in the optical path between the lens element L1 and the third reflecting surface R3 in the second sub-optical system OP2. The third intermediate imaging position MI3 is formed in the optical path between the first reflecting surface R1 and the third reflecting surface R3.

[0048] In the first sub-optical system OP1, the chief ray intersects between the lens element L5 and the lens element L6, and with the lens element L2.

[0049] 10 is a layout diagram showing an optical system 1 according to Example 3. Surface data of Example 3 will be shown in Numerical Example 3, which will be described later.

[0050] In the third embodiment, the first sub-optical system OP1 includes a plurality of lens elements L1 to L10 and a diaphragm ST.

[0051] In the first sub-optical system OP1, multiple lens elements L1 to L10 are arranged in order from the magnification side to the reduction side. Lens element L1 has a positive meniscus shape with a convex surface facing the reduction side. Lens element L2 has a biconvex shape. Lens element L3 has a negative meniscus shape with a convex surface facing the reduction side. Lens element L4 has a biconvex shape. Lens element L5 has a biconvex shape. Lens element L6 has a positive meniscus shape with a convex surface facing the magnification side. Lens element L7 has a biconvex shape. Lens element L8 has a positive meniscus shape with a convex surface facing the reduction side. Lens element L9 has a negative meniscus shape with a convex surface facing the reduction side. Lens element L10 has a biconvex shape.

[0052] A diaphragm ST is disposed between lens element L6 and lens element L7.

[0053] The second sub-optical system OP2 includes a first transmitting surface T1, a second transmitting surface T2, a first reflecting surface R1, and a second reflecting surface R2. In the second sub-optical system OP2, the first transmitting surface T1, the first reflecting surface R1, the second reflecting surface R2, and the second transmitting surface T2 are arranged in this order from the magnification side to the reduction side.

[0054] The first transmitting surface T1 is disposed on the most enlarged side of the second sub-optical system OP2. The first transmitting surface T1 has an aspherical shape with a convex surface facing toward the air.

[0055] The second transmitting surface T2 is disposed on the most reduction side of the second sub-optical system OP2. The second transmitting surface T2 has an aspherical shape with a convex surface facing toward the air.

[0056] The first reflecting surface R1 is the reflecting surface that is arranged on the most magnified side of the multiple reflecting surfaces in the second sub-optical system OP2, and is arranged on the optical path between the first transmitting surface T1 and the second transmitting surface T2. The first reflecting surface R1 has an aspheric shape with a concave surface facing in the direction in which the light ray incident on the first reflecting surface R1 is reflected.

[0057] The second reflecting surface R2 is the reflecting surface located on the most reduced side of the plurality of reflecting surfaces in the second sub-optical system OP2, and is located on the optical path between the first transmitting surface T1 and the second transmitting surface T2. The second reflecting surface R2 has an aspheric shape with a concave surface facing in the direction in which the light ray incident on the second reflecting surface R2 is reflected.

[0058] A medium with a refractive index of 1.4 or more is provided in the optical path between the first reflecting surface R1 and the second reflecting surface R2. As an example, the first transmitting surface T1, the second transmitting surface T2, the first reflecting surface R1, and the second reflecting surface R2 are formed by a prism PM. The prism PM is formed of, for example, glass, synthetic resin, or the like. With this configuration, the reflecting surface can be made smaller, and the second sub-optical system OP2 can be made more compact.

[0059] The first intermediate imaging position MI1 is formed in the optical path between the lens element L4 and the lens element L5 in the first sub-optical system OP1. The second intermediate imaging position MI2 is formed in the optical path between the second transmitting surface T2 and the second reflecting surface R2 in the second sub-optical system OP2. The third intermediate imaging position MI3 is formed in the optical path between the first reflecting surface R1 and the first transmitting surface T1.

[0060] In the first sub-optical system OP1, the chief ray intersects between the lens element L1 and the lens element L3, and between the lens element L6 and the lens element L7.

[0061] 14 is a layout diagram showing an optical system 1 according to Example 4. Surface data of Example 4 will be shown in Numerical Example 4, which will be described later.

[0062] In the fourth embodiment, the first sub-optical system OP1 includes a plurality of lens elements L1 to L9 and a diaphragm ST.

[0063] In the first sub-optical system OP1, multiple lens elements L1 to L9 are arranged in order from the enlargement side to the reduction side. Lens element L1 has a negative meniscus shape with a convex surface facing the reduction side. Lens element L2 has a biconvex shape. Lens element L3 has a positive meniscus shape with a convex surface facing the reduction side. Lens element L4 has a positive meniscus shape with a convex surface facing the reduction side. Lens element L5 has a biconvex shape. Lens element L6 has a biconvex shape. Lens element L7 has a negative meniscus shape with a convex surface facing the reduction side. Lens element L8 has a negative meniscus shape with a convex surface facing the reduction side. Lens element L9 has a biconvex shape.

[0064] A diaphragm ST is disposed between lens element L5 and lens element L6.

[0065] The second sub-optical system OP2 includes a first transmitting surface T1, a second transmitting surface T2, a first reflecting surface R1, a second reflecting surface R2, a third reflecting surface R3, and a third transmitting surface T2, which are arranged in this order from the magnification side to the reduction side.

[0066] The first transmitting surface T1 is disposed on the most enlarged side of the second sub-optical system OP2. The first transmitting surface T1 has an aspherical shape with a convex surface facing toward the air.

[0067] The second transmitting surface T2 is disposed on the most reduction side of the second sub-optical system OP2. The second transmitting surface T2 has an aspherical shape with a convex surface facing toward the air.

[0068] The first reflecting surface R1 is the reflecting surface that is arranged on the most magnified side of the multiple reflecting surfaces in the second sub-optical system OP2, and is arranged on the optical path between the first transmitting surface T1 and the second transmitting surface T2. The first reflecting surface R1 has an aspheric shape with a concave surface facing in the direction in which the light ray incident on the first reflecting surface R1 is reflected.

[0069] The second reflecting surface R2 is disposed between the first reflecting surface R1 and the third reflecting surface R3. The second reflecting surface R2 reflects the light reflected by the third reflecting surface R3 toward the first reflecting surface R1. The second reflecting surface R2 has an aspheric shape with a concave surface facing in the direction in which the light incident on the second reflecting surface R2 is reflected.

[0070] The third reflecting surface R3 is the reflecting surface arranged on the most reduced side among the plurality of reflecting surfaces in the second sub-optical system OP2, and is arranged on the optical path between the first transmitting surface T1 and the second transmitting surface T2. The third reflecting surface R3 has an aspheric shape with a concave surface facing in the direction in which the light ray incident on the third reflecting surface R3 is reflected.

[0071] A medium with a refractive index of 1.4 or higher is provided in the optical path between the first reflecting surface R1 and the third reflecting surface R3. As an example, 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. The prism PM is formed of, for example, glass, synthetic resin, or the like. With this configuration, the reflecting surfaces can be made smaller, and the second sub-optical system OP2 can be made more compact.

[0072] The first intermediate imaging position MI1 is formed in the optical path between the lens element L3 and the lens element L5 in the first sub-optical system OP1. The second intermediate imaging position MI2 is formed in the optical path between the second transmitting surface T2 and the third reflecting surface R3 in the second sub-optical system OP2. The third intermediate imaging position MI3 is formed in the optical path between the second reflecting surface R2 and the first transmitting surface T1.

[0073] The chief ray intersects within the lens element L2 and between the lens elements L5 and L6 in the first sub-optical system OP1.

[0074] Fifth Example FIG. 17 is a layout diagram showing an optical system 1 according to a fifth example.

[0075] The optical system 1 of Example 5 further includes a lens element L20 on the most enlarged side of the second sub-optical system OP2 in addition to the configuration of the optical system 1 of Example 1.

[0076] As an example, lens element L20 has a positive meniscus shape with a convex surface facing the magnification side.

[0077] Sixth Embodiment FIG. 18 is a layout diagram showing an optical system 1 according to a sixth embodiment.

[0078] The optical system 1 of Example 6 has the same configuration as the optical system 1 of Example 5, and in addition, a medium and air exist in the optical path between the first reflecting surface R1 and the second reflecting surface R2.

[0079] The medium is a transparent medium with a refractive index of 1.4 or more, and is, for example, an optical element made of glass, synthetic resin, etc. As an example, a first optical element PA1 and a second optical element PA2 are arranged in the optical path between the first reflecting surface R1 and the second reflecting surface R2. The first optical element PA1 is arranged on the enlargement side of the second optical element PA2 in the optical path between the first reflecting surface R1 and the second reflecting surface R2.

[0080] The first and second reflecting surfaces R1 and R2 are provided on the rear surfaces of the first and second optical elements PA1 and PA2, respectively, so that the first and second reflecting surfaces R1 and R2 reflect light rays from the rear surfaces of the first and second optical elements PA1 and PA2.

[0081] Air exists in the optical path between the first optical element PA1 and the second optical element PA2. By adopting the configurations of Examples 5 and 6, the reflecting surfaces R1 and R2 can be made small.

[0082] As described above, the optical system 1 according to the present disclosure has the following characteristics when viewed from a direction perpendicular to the Y-Z plane: (i) there are, in order from the reduction side to the enlargement side, a first intermediate imaging position MI1, a second intermediate imaging position MI2, and a third intermediate imaging position MI3; and (ii) chief rays at different image heights intersect twice between the most enlargement-side surface and the most reduction-side surface of the first sub-optical system OP1. The combination of these characteristics (i) and (ii) can increase peripheral illumination while suppressing distortion at wide angles. Specifically, the most off-axis angle can be increased and the angle of the image height close to the optical axis OA can be reduced. For example, the most off-axis angle can be 75 degrees or more, and the angle of the image height close to the optical axis OA can be 25 degrees or less. Here, "angle" refers to the angle of incidence of the light ray relative to the normal to the projection surface.

[0083] Next, conditions that can be satisfied by the optical system according to the present disclosure will be described. Note that, although multiple conditions are specified for the optical system according to each example, it is possible to satisfy all of these multiple conditions, or to satisfy individual conditions to obtain the corresponding effects.

[0084] Fig. 5 is a partially enlarged view showing the most enlarged side of the first sub-optical system OP1 in the optical system 1 of Example 1. Note that Fig. 5 shows the optical system 1 of Example 1 as an example of conditions that can be satisfied by the optical system 1 according to the present disclosure.

[0085] 5 , the optical system 1 according to the present disclosure satisfies the following condition (1): 3.0< ymax / y1 < 20.0 (1) where, y1: height in the Y direction of the chief ray closest to the optical axis on the most magnification side surface of the first sub-optical system, and ymax: height of the most off-axis chief ray on the most magnification side surface of the first sub-optical system.

[0086] With this configuration, distortion can be suppressed.

[0087] 1, 7, 10, and 14, the optical system 1 of the present disclosure satisfies the following condition (2): 10.0 < |fL1 / f| < 40.0 (2), where fL1 is the focal length of the lens on the most magnifying side of the first sub-optical system, and f is the focal length of the entire system.

[0088] With this configuration, the effective diameter of the reflecting surface can be reduced.

[0089] In the optical system 1 of the present disclosure, the surface on the reduction side of the first intermediate image is aspherical.

[0090] With this configuration, distortion can be suppressed.

[0091] Fig. 6 is a partially enlarged view showing the second sub-optical system OP2 in the optical system 1 of Example 1. Note that Fig. 6 shows the optical system 1 of Example 1 as an example of conditions that can be satisfied by the optical system 1 according to the present disclosure.

[0092] 6, the optical system 1 of the present disclosure satisfies the following condition (3): |ωmax|>75° (3), where ωmax is the maximum angle of view of the optical system.

[0093] This configuration allows for short-focus, large-screen projection.

[0094] Furthermore, the optical system 1 of the present disclosure satisfies the following condition (4): |ωmin| < 25° (4) where, ωmin: minimum angle of view of the optical system.

[0095] With this configuration, it is possible to prevent the projection position from becoming higher while preventing the shift amount from becoming larger.

[0096] 1, 7, 10, and 14, the optical system 1 of the present disclosure satisfies the following condition (5): 0.3 < L1m / L1s < 0.7 (5), where, L1m: distance from the most enlargement side surface of the first sub-optical system to the first intermediate imaging position, and L1s: distance from the most reduction side surface of the first sub-optical system to the first intermediate imaging position.

[0097] With this configuration, the reflecting surface can be made smaller.

[0098] Furthermore, the optical system 1 of the present disclosure satisfies the following condition (6): 0.2 < L2a / (L1m+L1s) < 0.5 (6) where, L1m: distance from the most enlargement side surface of the first sub-optical system to the first intermediate imaging position, L1s: distance from the most reduction side surface of the first sub-optical system to the first intermediate imaging position, and L2a: distance from the most enlargement side surface of the first sub-optical system to the most reduction side reflecting surface of the second sub-optical system.

[0099] With this configuration, the reflecting surface can be made smaller.

[0100] Fig. 13 is a partially enlarged view showing a second sub-optical system in the optical system of Example 3. Note that Fig. 13 shows the optical system 1 of Example 3 as an example of conditions that can be satisfied by the optical system 1 according to the present disclosure.

[0101] 13 , in the optical system 1 of the present disclosure, from the most magnification-side reflecting surface to the most magnification-side transmitting surface of the second sub-optical system OP2, the optical path ratio of the chief ray closest to the optical axis OA to the chief ray farthest from the optical axis OA satisfies the following condition (7): 1.1< OL2 / OL1 < 1.3 (7) where, OL1: optical path length of the chief ray closest to the optical axis from the most magnification-side reflecting surface of the second sub-optical system to the most magnification-side transmitting surface OL2: optical path length of the most off-axis chief ray from the most magnification-side reflecting surface of the second sub-optical system to the most magnification-side transmitting surface

[0102] With this configuration, the second sub-optical system OP2 can be made smaller.

[0103] 1, 7, 10, and 14, the optical system 1 of the present disclosure satisfies the following conditions (8) to (10): 3.0 < |f1s / f| < 20.0 (8) 5.0 < |f1m / f| < 20.0 (9) 2.0 < |f2 / f| < 5.0 (10) where, f1s: focal length of the first sub-optical system on the reduction side from the first intermediate imaging position, f1m: focal length of the first sub-optical system on the enlargement side from the first intermediate imaging position, and f2: focal length of the second sub-optical system.

[0104] With this configuration, the reflecting surface can be made smaller.

[0105] Furthermore, the optical system 1 of the present disclosure satisfies the following condition (11): 0.2<|f1 / f|<0.6 (11) where, f1: focal length of the first sub-optical system, and f: focal length of the entire system.

[0106] With this configuration, the reflecting surface can be made smaller.

[0107] Referring to FIG. 2, the optical system 1 of the present disclosure projects an image onto a single plane located at a conjugate point on the magnification side.

[0108] Such a configuration allows the image to be projected onto a single plane.

[0109] Numerical Example 1 With regard to the optical system of Numerical Example 1 (corresponding to Example 1), surface data is shown in Table 1, and aspherical lens shape data is shown in Table 2.

[0110]

[0111]

[0112] Numerical Example 2 With regard to the optical system of Numerical Example 2 (corresponding to Example 2), surface data is shown in Table 3, odd-order aspherical surface data of the lens is shown in Table 4, and aspherical surface data of the lens is shown in Table 5.

[0113]

[0114] Numerical Example 3 With regard to the optical system of Numerical Example 3 (corresponding to Example 3), surface data is shown in Table 6, and aspherical lens shape data is shown in Table 7.

[0115] Numerical Example 4 With regard to the optical system of Numerical Example 4 (corresponding to Example 4), surface data is shown in Table 8, and aspherical shape data of the lens is shown in Table 9.

[0116] Tables 10 and 11 show the conditions in the optical system 1 of Numerical Examples 1 to 4 (corresponding to Examples 1 to 4).

[0117]

[0118]

[0119] (Embodiment 2) Hereinafter, embodiment 2 of the present disclosure will be described with reference to FIG. 19 . FIG. 19 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, and the like. The image forming element 101 is configured with a liquid crystal display (LCD), a DMD, or the like, and generates an image to be projected onto the screen SR via the optical system 1. The light source 102 is configured with an LED (light-emitting diode), a laser, or the like, and supplies light to the image forming element 101. The control unit 110 is configured with a CPU, an MPU, or the like, 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 image projection device 100 from which the optical system 1 has been removed is an example of a main body device.

[0120] The image projection device 100 described above can achieve a wide-angle zoom function while reducing costs by using the optical system 1 according to the first embodiment.

[0121] (Embodiment 3) Hereinafter, embodiment 3 of the present disclosure will be described with reference to FIG. 20 . FIG. 20 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 imaging element 201, a control unit 210, and the like. The imaging element 201 is configured as a CCD (charge-coupled device) image sensor, a CMOS image sensor, or the like, and receives an 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 configured as a CPU or MPU, or the like, 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 imaging device 200 from which the optical system 1 has been removed is an example of a main body device.

[0122] The imaging device 200 described above can achieve a wide-angle zoom function while reducing costs by using the optical system 1 according to the first embodiment.

[0123] As described above, the embodiments have been described as disclosure of the technology in the present disclosure, and the accompanying drawings and detailed description have been provided for this purpose.

[0124] Therefore, the components shown in the accompanying drawings and detailed description may include not only essential components for solving the problem, but also components that are not essential for solving the problem in order to illustrate the above technology. Therefore, the fact that these non-essential components are shown in the accompanying drawings or detailed description should not be interpreted as immediately indicating that these non-essential components are essential.

[0125] Furthermore, since the above-described embodiments are intended to illustrate the technology of the present disclosure, various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.

[0126] Furthermore, in the above-described embodiment, the optical system 1 is described as viewed from a direction orthogonal to the Y-Z plane, with the optical axis OA defined as the Z direction in an X-Y-Z Cartesian coordinate system. However, the optical system 1 viewed from a direction orthogonal to the X-Z plane may also be the same as the optical system 1 viewed from a direction orthogonal to the Y-Z plane. That is, even in the optical system 1 viewed from a direction orthogonal to the X-Z plane, three intermediate image positions may be formed, and chief rays at different image heights may intersect twice within the first sub-optical system OP1 between the surface on the most enlargement side and the surface on the most reduction side of the first sub-optical system.

[0127] The present disclosure is applicable to image projection devices such as projectors and head-up displays, as well as imaging devices such as digital still cameras, digital video cameras, surveillance cameras in surveillance systems, web cameras, and in-vehicle cameras. In particular, the present disclosure is applicable to optical systems that require high image quality, such as projectors, digital still camera systems, and digital video camera systems.

[0128] 1 Optical system L1 to L10, L20 Lens elements R1 to R3 Reflecting surfaces T1 to T2 Transmitting surfaces ST Aperture P, PA1, PA2 Optical elements PM Prism S Original image

Claims

1. A system comprising a first sub-optical system and a second sub-optical system arranged in order from the reduction side to the enlargement side, wherein the first sub-optical system includes a plurality of lenses that are rotationally symmetric about the optical axis, and the second sub-optical system includes at least two reflective surfaces with concave surfaces, wherein, when the optical axis is defined as the Z direction and the direction perpendicular to the Z direction is defined as the Y direction, there are a first intermediate imaging position, a second intermediate imaging position, and a third intermediate imaging position in order from the reduction side to the enlargement side when viewed from a direction perpendicular to the Y-Z plane, and when viewed from a direction perpendicular to the Y-Z plane, chief rays of different image heights intersect twice between the most enlargement side surface and the most reduction side surface of the first sub-optical system, and the first intermediate imaging position is located within the first sub-optical system and is a conjugate point of the reduction side and a conjugate point of the second intermediate imaging at the second intermediate imaging position, An optical system wherein the second intermediate imaging position is located within the second sub-optical system and is a conjugate point of the first intermediate imaging at the first intermediate imaging position and a conjugate point of the third intermediate imaging at the third intermediate imaging position, and the third intermediate imaging position is located on the magnification side of the second intermediate imaging position within the second sub-optical system and is a conjugate point of the second intermediate imaging and a conjugate point of the magnification side.

2. The optical system described in claim 1, wherein the at least two reflecting surfaces include a first reflecting surface arranged on the most enlarged side of the second sub-optical system and a second reflecting surface arranged on the most reduced side of the second sub-optical system, and air is present in the optical path between the first reflecting surface and the second reflecting surface.

3. The optical system described in claim 1, wherein the at least two reflecting surfaces include a first reflecting surface located on the most enlarged side of the second sub-optical system and a second reflecting surface located on the most reduced side of the second sub-optical system, and a medium having a refractive index of 1.4 or more is provided in the optical path between the first reflecting surface and the second reflecting surface.

4. The optical system according to any one of claims 1 to 3, which satisfies the following condition (1): 3.0< ymax / y1 < 20.0 (1), where, y1: height in the Y direction of the chief ray closest to the optical axis on the surface on the most magnification side of the first sub-optical system, and ymax: height of the most off-axis chief ray on the surface on the most magnification side of the first sub-optical system.

5. The optical system according to any one of claims 1 to 4, which satisfies the following condition (2): 10.0 < |fL1 / f| < 40.0 (2), where fL1 is the focal length of the lens on the most magnifying side of the first sub-optical system, and f is the focal length of the entire system.

6. The optical system according to any one of claims 1 to 5, wherein the surface on the reduction side of the first intermediate image is aspherical.

7. The optical system according to any one of claims 1 to 6, which satisfies the following condition (3): |ωmax| > 75° (3), where ωmax: maximum angle of view of the optical system.

8. The optical system according to claim 1, which satisfies the following condition (4): |ωmin| < 25° (4), where ωmin: minimum angle of view of the optical system.

9. The optical system according to claim 1, which satisfies the following condition (5): 0.3 < L1m / L1s < 0.7 (5), where L1m: distance from the most enlargement side surface of the first sub-optical system to the first intermediate imaging position, and L1s: distance from the most reduction side surface of the first sub-optical system to the first intermediate imaging position.

10. The optical system according to claim 1, which satisfies the following condition (6): 0.2 < L2a / (L1m + L1s) < 0.5 (6), where, L1m: distance from the most enlargement side surface of the first sub-optical system to the first intermediate imaging position, L1s: distance from the most reduction side surface of the first sub-optical system to the first intermediate imaging position, and L2a: distance from the most enlargement side surface of the first sub-optical system to the most reduction side reflecting surface of the second sub-optical system.

11. The optical system according to claim 3, wherein, from the most magnification-side reflecting surface to the most magnification-side transmitting surface of the second sub-optical system, the optical path ratio of the chief ray closest to the optical axis to the chief ray farthest from the optical axis satisfies the following condition (7): 1.1 < OL2 / OL1 < 1.3 (7) where, OL1: optical path length of the chief ray closest to the optical axis from the most magnification-side reflecting surface of the second sub-optical system to the most magnification-side transmitting surface OL2: optical path length of the most off-axis chief ray from the most magnification-side reflecting surface to the most magnification-side transmitting surface of the second sub-optical system 12. The optical system according to claim 1, which satisfies the following conditions (8) to (10): 3.0 < |f1s / f| < 20.0 (8) 5.0 < |f1m / f| < 20.0 (9) 2.0 < |f2 / f| < 5.0 (10) where, f1s: focal length of the first sub-optical system on the reduction side from the first intermediate imaging position, f1m: focal length of the first sub-optical system on the enlargement side from the first intermediate imaging position, f2: focal length of the second sub-optical system, and f: focal length of the entire system.

13. The optical system according to claim 1, which satisfies the following condition (11): 0.2 < |f1 / f| < 0.6 (11), where, f1: focal length of the first sub-optical system, and f: focal length of the entire system.

14. The optical system of claim 1, wherein the optical system projects an image onto a single plane located at a conjugate point of the magnification side.

15. An image projection device comprising: an optical system according to any one of claims 1 to 14; and an image forming element that generates an image to be projected onto a screen via said optical system.

16. An imaging device comprising: an optical system according to any one of claims 1 to 14; and an imaging element that receives an optical image formed by the optical system and converts it into an electrical image signal.

Images