JP2014029431A - Optical system and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system capable of imaging a lateral side of the optical system at a wide angle without being affected by chromatic aberration.SOLUTION: An optical system not including a lens comprises: a hyperboloidal mirror 101 having the shape of at least a part of a rotationally symmetric convex surface having a focal point; and an opening member 102 restricting reflected light of the hyperboloidal mirror 101 to reflected light of light traveling to the focal point of the hyperboloidal mirror 101 and guiding the reflected light of the hyperboloidal mirror 101 having the restricted traveling direction to an image sensor 104 without passing through the lens.

Description

  The present invention relates to an optical system and an imaging apparatus, and more particularly, to an optical system and an imaging apparatus for performing wide-angle imaging on the side of the optical system.

  Omni-directional cameras have been developed to acquire wide-angle visual field information, and studies on catadioptric optical systems that are conscious of the lateral field of view are being actively studied in the field of robotics. In particular, an omnidirectional camera having the property of single viewpoint is expected as a useful omnidirectional optical system because it is possible to present an image that is easy for humans to view, or because conventional image processing technology can be used. ing. Here, the single viewpoint property is a property that allows an image captured by an omnidirectional camera to be converted without distortion into a perspective projection image viewed from a certain viewpoint. As typical examples of such an omnidirectional optical system having a single viewpoint, an optical system using a hyperboloidal mirror (for example, see Patent Document 1) and an optical system using a parabolic mirror (for example, Patent Document 2). See).

  In general, it is difficult to reduce the size of an optical system using a single mirror. In order to solve such a problem, an optical system in which a plurality of reflecting mirrors are combined and a single viewpoint is maintained has been proposed (for example, see Patent Documents 3 and 4).

JP-A-6-295333 US Pat. No. 6,118,474 JP-A-11-331654 International Publication No. 2010/116705

  However, in any optical system, a light receiving lens for guiding light to the image sensor is required. For this reason, there exists a subject that the image imaged with the image pick-up element receives to the influence of chromatic aberration.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an optical system and an imaging apparatus capable of performing wide-angle imaging of the side of the optical system without being affected by chromatic aberration. To do.

  In order to achieve the above object, an optical system according to an aspect of the present invention is an optical system that does not include a lens, and includes a first mirror having a shape of at least a part of a rotationally symmetrical convex surface having a focal point, An aperture that restricts the reflected light of the first mirror to the reflected light of the light directed toward the focal point of the first mirror and guides the reflected light of the first mirror, whose traveling direction is restricted, to the image sensor without passing through a lens. A part.

  According to these configurations, since the first mirror has a convex shape, it can reflect light incident from the side of the optical system. In addition, since the aperture section limits the traveling direction of the reflected light of the first mirror, only the reflected light of the light directed to the focal point of the first mirror among the reflected light of the first mirror can be guided to the image sensor. Since the image of the reflected light received by the image sensor is an image maintaining single viewpoint, it can be converted into a perspective projection image viewed from the focal point of the first mirror without distortion. In addition, since this optical system does not use a lens, the side of the optical system can be imaged at a wide angle without being affected by chromatic aberration.

  In addition, the optical system described above further has at least a part of a rotationally symmetric concave surface that guides the reflected light of the first mirror whose traveling direction is limited by the aperture portion to the imaging element. A second mirror may be provided.

  For example, the first mirror may include a hyperboloid mirror having a shape of at least a part of one of the two leaf hyperbolas.

  By making the first mirror a hyperboloid, the side of the optical system can be imaged at a wide angle.

  For example, the aperture portion may be arranged at the focal point of the other hyperboloid of the two-leaf hyperboloid.

  The light traveling toward the focal point of the first mirror is reflected toward the focal point of the other hyperboloid. For this reason, with such an arrangement, it is possible to efficiently limit the reflected light of the first mirror to the reflected light of the light traveling toward the focal point of the first mirror.

  The second mirror may include a parabolic mirror having a shape of at least a part of a paraboloid.

  For example, the aperture portion may be arranged at the focal point of the paraboloid.

  With this arrangement, the parabolic mirror can reflect the reflected light of the first mirror whose traveling direction is limited by the aperture portion in a direction parallel to the rotation axis of the parabolic mirror.

  The aperture section may include a member having an opening at a position where the reflected light of the first mirror is condensed.

  The aperture section may include a third mirror arranged at a position where the reflected light of the first mirror is collected.

  The optical system described above may further include a fourth mirror that reflects the light reflected by the third mirror and guides the light to the second mirror.

  For example, the fourth mirror may include a plane mirror.

  The first mirror is located on one side of the image sensor, and has a first hyperboloid mirror having a shape of at least a part of one hyperboloid of the first two-leaf hyperbolas, and the imaging A second hyperboloid mirror located on the other side of the element and having a shape of at least a part of one hyperboloid of the second bilobal hyperboloid, and the aperture section includes the first hyperboloid A first member having an opening at the focal point of the other hyperboloid of the first biplane hyperboloid that forms a pair with the hyperboloid of the mirror, and the second biplane biplane that forms a pair with the hyperboloid of the second hyperboloid mirror. A second member having an opening at the focal point of the other hyperboloid of the curved surface, the second mirror is located above the image sensor, and the focal point of the first paraboloid is at the opening of the first member. A first paraboloid mirror located at least part of the shape of the first paraboloid; A second paraboloid mirror having a shape of at least a part of the second paraboloid located above the image sensor and having a focal point of the second paraboloid located at the opening of the second member; It may be included.

  In this configuration, the first hyperboloidal mirror and the second hyperboloidal mirror are arranged on both sides of the optical system. For this reason, wide-angle imaging can be performed on both the left and right sides of the optical system.

  The first mirror includes a hyperboloid mirror having a shape of at least a part of one hyperboloid of the two-leaf hyperboloid, and the aperture portion has a focal point of the other hyperboloid of the two-lobe hyperboloid. The second mirror includes a third mirror having a reflecting surface, and the second mirror has a parabolic surface whose focal point coincides with the focal point of the other hyperboloid and has a shape of at least a part of the paraboloid. May be included.

  Each of the first mirror and the second mirror is a parabolic mirror having a shape of at least a part of a paraboloid, and the optical system further has a shape of at least a part of the paraboloid. The concave mirror is a position capable of reflecting the reflected light of the first mirror, which is reflected light toward the focal point of the first mirror, and the focal point of the concave mirror is the first mirror. Two apertures may be disposed at a position that coincides with the focal point of the two mirrors, and the aperture portion may include a member having an opening at the focal point of the concave mirror.

  According to this configuration, an optical system can be designed with only a parabolic mirror without using a hyperboloid mirror.

  An imaging device according to another aspect of the present invention includes the above-described optical system and an imaging element that captures an image of reflected light of a first mirror guided by the optical system.

  Even with this configuration, the same effects as those of the above-described optical system can be obtained.

  According to the present invention, it is possible to provide an optical system and an imaging apparatus capable of performing wide-angle imaging of the side of the optical system without being affected by chromatic aberration.

It is a figure which shows the structure of the imaging device which concerns on Embodiment 1 of this invention. It is a figure for demonstrating the property of a hyperboloid mirror. It is a figure for demonstrating the property of a parabolic mirror. It is a figure which shows an example of the image imaged with the image pick-up element. It is a figure which shows an example of the image imaged with the image pick-up element. It is a figure which shows the structure of the imaging device which concerns on Embodiment 2 of this invention. It is a perspective view of the imaging device which concerns on Embodiment 3 of this invention. (A) is a front view of an imaging device. (B) is a right side view of the imaging apparatus. (C) is AA sectional drawing of an imaging device. (D) is BB sectional drawing of an imaging device. It is a figure which shows the structure of the imaging device which concerns on Embodiment 3 of this invention. It is a figure which shows the structure of the imaging device which concerns on Embodiment 4 of this invention. It is a figure which shows the structure of the imaging device which concerns on the modification of Embodiment 4 of this invention. It is a figure which shows the structure of the imaging device which concerns on Embodiment 5 of this invention. It is a figure which shows the structure of the imaging device which concerns on Embodiment 6 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that each of the embodiments described below shows a specific example of the present invention. Numerical values, shapes, materials, constituent elements, arrangement positions and connection forms of constituent elements, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept are described as optional constituent elements.

(Embodiment 1)
FIG. 1 is a diagram illustrating a configuration of an imaging apparatus according to Embodiment 1 of the present invention. FIG. 1 is a diagram schematically illustrating a cross section in a vertical plane of the imaging apparatus.

  The imaging device 100 includes a hyperboloid mirror 101, an opening member 102, a parabolic mirror 103, and an imaging element 104.

  The hyperboloid mirror 101 is a convex mirror having a shape of at least a part of one of the two leaf hyperbolas. The two-leaf hyperboloid is defined by Equation 1 below.

^{aX 2 -bY 2 -cZ 2 = 1} ( Equation 1)

  Here, a, b, and c are positive real numbers, respectively. The rotation axis of the hyperboloid mirror 101 is the Z axis. Note that the equation defining the two-leaf hyperboloid is not limited to Equation 1, and may include a third or higher order term.

  Here, the property of the hyperboloid mirror 101 will be described with reference to FIG. FIG. 2 shows a cross-sectional view at the center of rotation of the two-leaf hyperboloid. The two-leaf hyperboloid is composed of two hyperboloids 211 and 213. The light 215 directed to the focal point 212 of one hyperboloid 211 of the two-leaf hyperboloid is reflected by the convex hyperboloid mirror having the shape of the hyperboloid 211 toward the focal point 214 of the other hyperboloid 213. Have. Therefore, by collecting the light passing through the focal point 214, an image having a single viewpoint can be obtained.

  The opening member 102 is an opaque member having an opening 102a. The opening member 102 is arranged so that the opening 102a is positioned at the focal point 101a of the other hyperboloid paired with the hyperboloid mirror 101. The size of the opening 102a is designed to allow light that passes through the focal point 101a to pass and not to pass other light.

  The parabolic mirror 103 is a concave mirror having a parabolic shape, and is disposed at a position where the focal point of the paraboloid coincides with the focal point 101a of the hyperboloid. The paraboloid is defined by Equation 2 below.

^{-AX 2 -bY 2 + 2cZ = 1} ( Equation 2)

  Here, a, b, and c are positive real numbers, respectively. The rotation axis of the parabolic mirror 103 is the Z axis. Note that the equation defining the paraboloid is not limited to Equation 2, and may include a third-order or higher term.

  Here, the property of the parabolic mirror 103 will be described with reference to FIG. FIG. 3 shows a cross-sectional view at the center of rotation of the paraboloid. Light 223 passing through the focal point 222 of the paraboloid 221 and traveling toward the paraboloid 221 is reflected in a direction parallel to the center of rotation 224 of the paraboloid 221 by a concave paraboloid mirror having the shape of the paraboloid 221. It has the property that the optical path is changed. For this reason, by providing an image sensor at a position facing the paraboloid mirror, the light 223 that has passed through the focal point 222 of the paraboloid 221 can be imaged.

  Referring to FIG. 1, the focal point of paraboloid mirror 103 coincides with a hyperboloid focal point 101a that forms a pair with hyperboloidal mirror 101, and aperture 102a of aperture member 102 is located at focal point 101a. . For this reason, the light that passes through the opening 102 a and is reflected by the parabolic mirror 103 is parallel to the rotation axis of the parabolic mirror 103. Therefore, by providing the image sensor 104 at a position facing the paraboloid mirror 103, the light toward the focal point of the hyperboloid mirror 101 can be imaged by the image sensor 104. For this reason, the image sensor 104 can capture an image having a single viewpoint. In addition, the arrow in FIG. 1 has shown the optical path. The same applies to the other drawings described below.

  The image sensor 104 is an image sensor configured by a CCD (Charge Coupled Device) or the like.

  Each of FIG. 4 and FIG. 5 shows an example of an image captured by the image sensor 104. It can be seen that the image captured by the image sensor 104 is an image obtained by wide-angle imaging of the side.

  As described above, according to the first embodiment, the hyperboloid mirror 101 can reflect light incident from the side of the optical system because it has a convex shape. Further, since the opening member 102 limits the traveling direction of the reflected light of the hyperboloidal mirror 101, only the reflected light of the light directed toward the focal point of the hyperboloidal mirror 101 among the reflected light of the hyperboloidal mirror 101 is guided to the image sensor 104. be able to. Since the image of the reflected light received by the image sensor 104 is an image maintaining single viewpoint, it can be converted into a perspective projection image viewed from the focal point of the hyperboloid mirror 101 without distortion. In addition, since this optical system does not use a lens, the side of the optical system can be imaged at a wide angle without being affected by chromatic aberration.

(Embodiment 2)
In the first embodiment, the hyperboloid mirror 101 is arranged only on the left side of the image sensor 104 as shown in FIG. For this reason, wide-angle imaging was possible only on the left side of the image sensor 104. On the other hand, in the present embodiment, an imaging apparatus capable of performing wide-angle imaging on both the left and right sides of the imaging element 104 by arranging a hyperboloid mirror on the right side of the imaging element 104 will be described.

  FIG. 6 is a diagram illustrating a configuration of an imaging apparatus according to Embodiment 2 of the present invention. FIG. 6 is a diagram schematically illustrating a cross section in a vertical plane of the imaging apparatus.

  The imaging apparatus 200 includes a hyperboloid mirror 101, an aperture member 102, a parabolic mirror 103, an imaging element 104, a hyperboloid mirror 201, an aperture member 202, and a paraboloid mirror 203.

  The configurations of the hyperboloid mirror 101, the aperture member 102, and the parabolic mirror 103 are the same as those in the first embodiment. Therefore, detailed description thereof will not be repeated here. The hyperboloid mirror 201, the aperture member 202, and the paraboloid mirror 203 are disposed at positions symmetrical to the hyperboloid mirror 101, the aperture member 102, and the paraboloid mirror 103 with respect to a plane orthogonal to the image sensor 104. The hyperboloid mirror 201, the aperture member 202, and the paraboloid mirror 203 have the same configuration as the hyperboloid mirror 101, the aperture member 102, and the paraboloid mirror 103 except that they are symmetric. The imaging element 104 is provided at a position facing the parabolic mirrors 103 and 203 and images the reflected light of the parabolic mirror 103 and the reflected light of the parabolic mirror 203. According to the hyperboloid mirror 201, the opening member 202, and the parabolic mirror 203, wide-angle imaging can be performed on the right side of the imaging element 104.

  Note that the parabolic mirror 103 and the parabolic mirror 203 may be integrally formed because they are in contact with each other.

  As described above, according to the second embodiment, it is possible to provide the imaging apparatus 200 that exhibits the same effects as the first embodiment. In addition, wide-angle imaging can be performed on both the left and right sides of the imaging apparatus 200.

(Embodiment 3)
An imaging apparatus according to Embodiment 3 will be described. In Embodiment 1, the optical path of the reflected light of the hyperboloidal mirror is limited by using the opening member. In this embodiment, a configuration of an imaging device that restricts the optical path of reflected light of a hyperboloidal mirror by using a small-area mirror instead of the aperture member will be described.

  FIG. 7 is a perspective view of an imaging apparatus 300 according to Embodiment 3 of the present invention. FIG. 8A is a front view of the imaging apparatus 300. FIG. FIG. 8B is a right side view of the imaging apparatus 300. FIG. 8C is a cross-sectional view of the imaging apparatus 300 taken along the line AA. FIG. 8D is a BB cross-sectional view of the imaging device 300.

  FIG. 9 is a diagram illustrating a configuration of an imaging apparatus according to Embodiment 3 of the present invention. FIG. 9 is a diagram schematically illustrating a cross section in a vertical plane of the imaging apparatus. Note that the cross-sectional view shown in FIG. 9 is inverted from the cross-sectional view shown in FIG.

  The imaging apparatus 300 includes a hyperboloid mirror 301, an aperture mirror 302, a parabolic mirror 303, an imaging element 104, cylinders 304 and 305, and a plate 306.

  The hyperboloid mirror 301 has the same configuration as the hyperboloid mirror 101. However, the difference is that the convex surface is downward.

  The aperture mirror 302 is a mirror having a reflecting surface at a hyperboloid focal point 301 a that forms a pair with the hyperboloid mirror 301. The aperture mirror 302 is designed to have a size that reflects light passing through the focal point 301a and does not reflect other light. The aperture mirror 302 is a plane mirror. However, in order to efficiently collect the reflected light of the hyperboloidal mirror 301 on the parabolic mirror 303, it may have a curved surface shape. That is, the equation defining the hyperboloid mirror 301 may include a second-order or higher term.

  The parabolic mirror 303 has the same configuration as the parabolic mirror 103, and is arranged so that the focal point of the parabolic mirror 303 coincides with the hyperboloidal focal point 301a that forms a pair with the hyperboloidal mirror 301. The light reflected by the aperture mirror 302 is reflected by the parabolic mirror 303, so that the optical path is changed in a direction parallel to the rotation axis of the parabolic mirror 303.

  The image sensor 104 is provided at a position facing the parabolic mirror 303. Thereby, the light reflected by the parabolic mirror 303 can be received.

  The plate 306 is installed around the aperture mirror 302, and prevents light other than the reflected light of the hyperboloid mirror 301 from entering the aperture mirror 302.

  The cylindrical body 304 is installed around the parabolic mirror 303, and prevents light other than the reflected light of the aperture mirror 302 from entering the parabolic mirror 303.

  The cylindrical body 305 is installed around the image sensor 104 and prevents light other than the reflected light of the parabolic mirror 303 from entering the image sensor 104.

  Note that the hyperboloid mirror 301, the cylindrical body 304, and the parabolic mirror 303 may be integrally formed because they are in contact with each other.

  As described above, according to the third embodiment, the traveling direction of the reflected light of the hyperboloidal mirror 301 can be limited using the aperture mirror 302 instead of the opening member. Thereby, only the reflected light of the light directed to the focal point of the hyperboloidal mirror 301 among the reflected light of the hyperboloidal mirror 301 can be guided to the image sensor 104. Since the image of the reflected light received by the image sensor 104 is an image maintaining single viewpoint, it can be converted into a perspective projection image viewed from the focal point of the hyperboloid mirror 301 without distortion. In addition, since this optical system does not use a lens, the side of the optical system can be imaged at a wide angle without being affected by chromatic aberration.

(Embodiment 4)
In the fourth embodiment, an imaging apparatus capable of wide-angle imaging by reflecting light four times using four mirrors and condensing the light on an imaging element will be described.

  FIG. 10 is a diagram showing a configuration of an imaging apparatus according to Embodiment 4 of the present invention. FIG. 10 is a diagram schematically illustrating a cross section in a vertical plane of the imaging apparatus.

  The imaging device 400 includes a hyperboloid mirror 401, an aperture mirror 402, a plane mirror 403, and a paraboloid mirror 404.

  The hyperboloid mirror 401 has the same configuration as the hyperboloid mirror 101. However, the difference is that the convex surface is downward.

  The aperture mirror 402 has the same configuration as the aperture mirror 302. That is, the aperture mirror 402 is a mirror having a reflecting surface at the focal point 401a of the hyperboloid paired with the hyperboloidal mirror 401. The aperture mirror 402 is designed to have a size that reflects light passing through the focal point 401a and does not reflect other light.

  The plane mirror 403 is a mirror that reflects the light reflected by the aperture mirror 402 toward the parabolic mirror 404.

  The parabolic mirror 404 has the same configuration as the parabolic mirror 103. The plane mirror 403 and the paraboloidal mirror are arranged such that the same light reaching the paraboloidal mirror 404 when the paraboloidal mirror 404 is focused on the focal point 401a reaches the paraboloidal mirror 404. The arrangement position of 404 is determined. As a result, the light incident on the parabolic mirror 404 is reflected by the parabolic mirror 404, thereby changing the optical path in a direction parallel to the rotation axis of the parabolic mirror 404.

  The image sensor 104 is provided at a position facing the paraboloid mirror 404. Thereby, the light reflected by the parabolic mirror 404 can be received.

  As described above, according to the fourth embodiment, the traveling direction of the reflected light of the hyperboloidal mirror 401 can be limited by using the aperture mirror 402 instead of the opening member. Thereby, only the reflected light of the light directed toward the focal point of the hyperboloidal mirror 401 among the reflected light of the hyperboloidal mirror 401 can be guided to the image sensor 104. Since the image of the reflected light received by the image sensor 104 is an image that maintains single viewpoint, it can be converted into a perspective projection image viewed from the focal point of the hyperboloidal mirror 401 without distortion. In addition, since this optical system does not use a lens, the side of the optical system can be imaged at a wide angle without being affected by chromatic aberration.

(Modification of Embodiment 4)
FIG. 11 is a diagram illustrating a configuration of an imaging apparatus according to a modification of the fourth embodiment of the present invention. The imaging apparatus shown in FIG. 11 performs wide-angle imaging by reflecting light four times and condensing the light on the imaging element using four mirrors similarly to the imaging apparatus 400 according to the fourth embodiment. However, the configuration and arrangement of the four mirrors are different.

  The imaging device 410 includes a hyperboloid mirror 401, a concave mirror 411, an aperture mirror 412, a parabolic mirror 413, and an imaging element 104.

  The hyperboloid mirror 401 has the same configuration as the hyperboloid mirror 401 shown in FIG. The hyperboloidal mirror 401 reflects light incident toward the focal point of the hyperboloidal mirror 401 toward the focal point of the hyperboloid that forms a pair with the hyperboloidal mirror 401.

  The concave mirror 411 is a mirror that reflects the reflected light of the light incident from the side of the hyperboloidal mirror 401 and directed toward the focal point of the hyperboloidal mirror 401 toward the aperture mirror 412. It has a shape specified by a formula having the term:

  The aperture mirror 412 reflects the light reflected by the concave mirror 411 toward the parabolic mirror 413. The aperture mirror 412 is arranged at the focal point 413a of the parabolic mirror 413, and is designed to have a size that reflects light passing around the focal point 413a of the parabolic mirror 413 and does not reflect other light. The

  The parabolic mirror 413 has the same shape as the parabolic mirror 103. However, the point that the concave surface is upward is different from the parabolic mirror 103.

  The image sensor 104 is provided at a position facing the paraboloid mirror 413 and receives light reflected by the paraboloid mirror 413.

  With such a configuration, as in the fourth embodiment, the side of the optical system can be imaged at a wide angle without being affected by chromatic aberration.

(Embodiment 5)
In the fifth embodiment, an imaging device capable of capturing an image of 360 degrees around will be described.

  FIG. 12 is a diagram showing a configuration of an imaging apparatus according to Embodiment 5 of the present invention. FIG. 12 is a diagram schematically illustrating a cross section in a vertical plane of the imaging apparatus.

  The imaging apparatus 500 includes a hyperboloid mirror 501, an opening member 502, a paraboloid mirror 503, and an imaging element 104.

  The hyperboloid mirror 501 has the same shape as the hyperboloid mirror 101. However, it differs from the hyperboloid mirror 101 in that the convex surface faces downward. Further, the hyperboloidal mirror 101 has a part of the shape of a hyperboloid, whereas the hyperboloidal mirror 501 has a complete hyperboloid shape. As a result, the hyperboloid mirror 101 can reflect only light of less than 360 degrees around its rotation axis, whereas the hyperboloid mirror 501 can reflect light of 360 degrees around its rotation axis.

  The opening member 502 is an opaque member having an opening 502a. The aperture member 502 is arranged so that the aperture 502a is positioned at a hyperboloid focal point 501a that forms a pair with the hyperboloid mirror 501. Note that the size of the opening 502a is designed to allow light passing through the focal point 501a to pass and not to pass other light.

  The parabolic mirror 503 has the same shape as the parabolic mirror 103. However, the point that the concave surface is upward is different from the parabolic mirror 103. Further, the parabolic mirror 103 has a partial paraboloid shape, whereas the parabolic mirror 503 has a complete paraboloid shape. The parabolic mirror 503 is disposed so that its focal point coincides with the focal point 501a. Further, the parabolic mirror 503 is arranged so that the rotation axis of the hyperboloid mirror 501 and the rotation axis of the paraboloid mirror 503 coincide.

  Thereby, the light that passes through the opening 502 a and is reflected by the parabolic mirror 503 is parallel to the rotation axis of the parabolic mirror 503. Therefore, by providing the image sensor 104 at a position facing the paraboloid mirror 503, the light toward the focal point of the hyperboloid mirror 501 can be captured by the image sensor 104. For this reason, the image sensor 104 can capture a 360-degree image having a single viewpoint.

  As described above, according to the fifth embodiment, the hyperboloidal mirror 501 can reflect light incident from 360 degrees around the side of the optical system because it has a convex shape. In addition, since the opening member 502 limits the traveling direction of the reflected light of the hyperboloidal mirror 501, only the reflected light of the light directed to the focal point of the hyperboloidal mirror 501 out of the reflected light of the hyperboloidal mirror 501 is guided to the image sensor 104. be able to. Since the image of the reflected light received by the image sensor 104 is an image maintaining single viewpoint, it can be converted into a perspective projection image viewed from the focal point of the hyperboloid mirror 501 without distortion. In addition, since this optical system does not use a lens, the side of the optical system can be imaged at a wide angle without being affected by chromatic aberration.

(Embodiment 6)
An imaging apparatus according to Embodiment 6 will be described. The imaging apparatus according to the sixth embodiment has a configuration in which two paraboloidal mirrors are used instead of the hyperboloidal mirror 101 in the configuration of the imaging apparatus 100 according to the first embodiment shown in FIG.

  FIG. 13 is a diagram showing a configuration of an imaging apparatus according to Embodiment 6 of the present invention. FIG. 13 is a diagram schematically illustrating a cross section in a vertical plane of the imaging apparatus.

  The imaging device 600 includes a parabolic mirror 601, a parabolic mirror 602, an opening member 603, a parabolic mirror 604, and an imaging element 104.

  Parabolic mirrors 601, 602 and 604 have the same shape as parabolic mirror 103. However, the parabolic mirror 601 is a downward convex mirror, and the parabolic mirror 602 is an upward concave mirror.

  The parabolic mirror 601 reflects light incident toward the focal point 601a of the parabolic mirror 601. The reflected light is light parallel to the rotation axis of the parabolic mirror 601.

  The parabolic mirror 602 is installed at a position where the reflected light of the parabolic mirror 601 is incident, and reflects the reflected light of the parabolic mirror 601.

  The opening member 603 has an opening 603 a and is arranged so that the opening 603 a is located at the focal point 602 a of the parabolic mirror 602. Note that the size of the opening 603a is designed to allow light passing through the focal point 602a to pass and not to pass other light. Thereby, the opening member 603 can pass only the parallel light incident on the parabolic mirror 602, that is, the light traveling toward the focal point of the parabolic mirror 601.

  The parabolic mirror 604 is disposed so that its focal point coincides with the focal point 602a, and reflects the light that has passed through the aperture member 603. Thereby, the optical path of the light that has passed through the opening member 603 can be made parallel to the rotation axis of the parabolic mirror 604.

  The image sensor 104 is provided at a position corresponding to the parabolic mirror 604. As a result, it is possible to pick up an image of light directed toward the focal point of the parabolic mirror 601 by the image pickup device 104. For this reason, the image sensor 104 can capture an image having a single viewpoint.

  As described above, according to the fifth embodiment, the parabolic mirrors 601 and 602 can be used instead of the hyperboloid mirror 101 to capture an image having a single viewpoint. As a result, the image captured by the image sensor 104 can be converted into a perspective projection image viewed from the focal point of the parabolic mirror 601 without distortion. In addition, since this optical system does not use a lens, the side of the optical system can be imaged at a wide angle without being affected by chromatic aberration.

  While the imaging device according to one or more aspects of the present invention has been described based on the embodiment, the present invention is not limited to this embodiment. Unless it deviates from the gist of the present invention, one or more of the present invention may be applied to various modifications that can be conceived by those skilled in the art, or forms constructed by combining components in different embodiments. It may be included within the scope of the embodiments.

  The optical system and the imaging apparatus according to the present invention can capture a lateral field of view, and thus can be applied to an omnidirectional camera for monitoring purposes.

100, 200, 300, 400, 410, 500, 600 Imaging devices 101, 201, 301, 401, 501 Hyperboloid mirrors 101a, 212, 214, 222, 301a, 401a, 413a, 501a, 601a, 602a Focal points 102, 202 , 502, 603 Opening member 102a, 603a, 502a Opening 103, 203, 303, 404, 413, 503, 601, 602, 604 Parabolic mirror 104 Imaging element 211, 213 Hyperboloid 215, 223 Light 221 Parabolic surface 224 Center of rotation 302, 402, 412 Aperture mirror 304, 305 Tube 306 Plate 403 Flat mirror 411 Concave mirror

Claims (14)

An optical system without a lens,
A first mirror having a shape of at least a portion of a rotationally symmetric convex surface having a focal point;
The reflected light of the first mirror is limited to the reflected light of the light directed toward the focal point of the first mirror, and the reflected light of the first mirror whose traveling direction is limited is guided to the image sensor without passing through the lens. An optical system comprising an aperture section. further,
The second mirror having at least a part of a rotationally symmetric concave surface that guides the reflected light of the first mirror, whose traveling direction is limited by the aperture portion, to the image pickup device. Optical system. The optical system according to claim 2, wherein the first mirror includes a hyperboloid mirror having a shape of at least a part of one of the two leaf hyperbolas. The optical system according to claim 3, wherein the aperture portion is disposed at a focal point of the other hyperboloid of the two-leaf hyperboloid. The optical system according to claim 2, wherein the second mirror includes a parabolic mirror having a shape of at least a part of a paraboloid. The optical system according to claim 5, wherein the aperture is disposed at a focal point of the paraboloid. The optical system according to claim 1, wherein the aperture portion includes a member having an opening at a position where the reflected light of the first mirror is condensed. The optical system according to claim 2, wherein the aperture section includes a third mirror disposed at a position where the reflected light of the first mirror is collected. further,
The optical system according to claim 8, further comprising a fourth mirror that reflects light reflected by the third mirror and guides the light to the second mirror. The optical system according to claim 9, wherein the fourth mirror includes a plane mirror. The first mirror is located on one side of the image sensor, and includes a first hyperboloid mirror having a shape of at least a part of one hyperboloid of the first two-leaf hyperbolas, and the image sensor. A second hyperboloid mirror located on the other side and having a shape of at least a part of one of the second biplane hyperboloids;
The aperture section includes a first member having an opening at a focal point of the other hyperboloid of the first biplane hyperboloid that forms a pair with the hyperboloid of the first hyperboloid mirror, and a hyperboloid of the second hyperboloid mirror. A second member having an opening at the focal point of the other hyperboloid of the second biplane hyperboloid paired with
The second mirror has a shape of at least a part of the first paraboloid located above the image sensor and having a focal point of the first paraboloid located at the opening of the first member. A second parabolic mirror and a second parabolic surface located above the image sensor and having a focal point of the second parabolic surface located at the opening of the second member; The optical system according to claim 2, further comprising a parabolic mirror. The first mirror includes a hyperboloid mirror having a shape of at least a part of one of the two leaf hyperbolas,
The aperture portion includes a third mirror having a reflective surface at the focal point of the other hyperboloid of the two-leaf hyperboloid,
The optical system according to claim 2, wherein the second mirror includes a parabolic mirror having a paraboloid focal point that coincides with a focal point of the other hyperboloid and having a shape of at least a part of the paraboloid. Each of the first mirror and the second mirror is a parabolic mirror having a shape of at least a part of a paraboloid,
The optical system further includes a concave mirror having a shape of at least a part of a paraboloid,
The concave mirror is a position capable of reflecting the reflected light of the first mirror, which is reflected light toward the focal point of the first mirror, and the focal point of the concave mirror coincides with the focal point of the second mirror. Placed in the position to
The optical system according to claim 2, wherein the aperture portion includes a member having an opening at a focal point of the concave mirror. The optical system according to any one of claims 1 to 13,
An imaging device comprising: an imaging element that images reflected light of the first mirror guided by the optical system.