JP4839013B2 - Optical system - Google Patents

Description

  The present invention relates to an optical system, and in particular, is small and has good resolution, and forms an image having a 360 ° omnidirectional angle of view on an image plane, or an image arranged on the image plane has a 360 ° omnidirectional angle of view. The present invention relates to an optical system suitable for an all-sky camera, an all-sky projector, and the like.

Conventionally, as a small-sized optical system using a catadioptric optical system to obtain an image of 360 ° omnidirectional (entire circumference), it has a transparent surface with two internal reflection surfaces and two refractive surfaces (an incident surface and an exit surface). Patent Documents 1 and 2 are known that include a front group that includes a medium and is rotationally symmetric about the central axis, and a rear group that is rotationally symmetric about the central axis and has positive power.
US Pat. No. 4,566,763 US Pat. No. 5,473,474

  However, in the above conventional example, there is a problem that the entrance pupil is not positioned in the vicinity of the entrance surface, the effective diameter of the entrance surface is increased, and there is a lot of harmful flare light from the zenith direction or the ground, so that the image is deteriorated. Further, the aberration was not necessarily corrected well, and the resolution was not good.

  The present invention has been made in view of such problems of the prior art, and the object thereof is 360 ° omnidirectional, which is not affected by flare light, is small in size, has good aberration correction, and has good resolution. It is to provide an optical system for photographing an image having an angle of view of (entire circumference) or projecting an image in an angle of view of 360 ° omnidirectional (omnidirectional).

The optical system of the present invention that achieves the above object provides:
An optical system that forms an image having an angle of view of 360 ° on an image plane or projects an image arranged on the image plane on an angle of view of 360 °,
A front group including two reflecting surfaces rotationally symmetric about the central axis, a rear group rotationally symmetric about the central axis and having positive power, and an opening arranged coaxially with the central axis,
The front group has a transparent medium that is rotationally symmetric about a central axis, and the transparent medium has a first transmission surface, a first reflection surface, a second reflection surface, and a second transmission surface;
The first reflecting surface is disposed on the image plane side with respect to the first transmitting surface, the second reflecting surface is disposed on the side opposite to the image surface with respect to the first reflecting surface, and the second transmitting surface is disposed on the first transmitting surface. It is arranged on the image plane side from the surface,
In the case of an imaging optical system, the light beam incident on the front group enters the transparent medium through the first transmission surface, in the order in which the light beam travels. Reflected on the opposite side to the image plane by the first reflecting surface disposed on the opposite side of the first transmitting surface across the axis, and disposed on the same side as the first transmitting surface with respect to the central axis. Reflected on the image plane side by the second reflecting surface, exits from the transparent medium through the second transmitting surface, forms an image at a position deviating from the central axis of the image surface through the rear group, and The entrance pupil position is different in the cross section including the central axis and in the cross section orthogonal to the cross section and including the central ray of the luminous flux ,
The entrance pupil in the cross section perpendicular to the cross section including the central axis is located on the central axis,
When the optical path length from the entrance pupil position in the cross section including the central axis to the opening position is A, and the optical path length from the entrance pupil position in the cross section including the central axis to the first transmission surface of the front group is B,
5 <| A / B | (4)
It is characterized by satisfying the following condition .

  In addition, the number of times the aperture image is projected by projecting the aperture in the direction opposite to the incident direction of the light flux is determined in a cross section including the central axis and in a cross section orthogonal to the cross section and including the central ray of the light flux. It is desirable that they are the same.

  Further, it is desirable that at least one reflecting surface has a rotationally symmetric shape formed by rotating an arbitrary-shaped line segment having no symmetry plane around the central axis.

  Further, it is desirable that at least one reflecting surface has a rotationally symmetric shape formed by rotating an arbitrary-shaped line segment including an odd-order term around the central axis.

  In addition, it is desirable that a flare stop that restricts the aperture only in the cross section including the central axis is disposed in the vicinity of the entrance pupil conjugate with the stop formed on the object side by the front group in the cross section including the central axis. .

  The rear group is preferably composed of a rotationally symmetric coaxial refractive optical system.

In the first optical system, the height from the end opposite to the image plane in the central axis direction of the front group to the end on the image plane side is H1, and the center axis is set from the end opposite to the image plane. When the height to the entrance pupil in the included cross section is H2,
1.5 <H1 / H2 <100 (1)
It is desirable to satisfy the following condition.

In any of the optical systems, the height from the end opposite to the image plane in the central axis direction of the front group to the end on the image plane side is H1, and the center axis is included from the end opposite to the image plane. When the height to the entrance pupil in the cross section is H2,
0.5 <H1 / H2 <10 (3)
It is desirable to satisfy the following condition.

When the distance between the entrance pupil position and the central axis in the cross section including the central axis is C, and the focal length in the cross section including the central axis of the front group is Ffy,
0.1 <C / | Ffy | (5)
It is desirable to satisfy the following condition.

When the magnification of the aperture with respect to the entrance pupil in the cross section including the central axis is Pβ,
0.05 <| Pβ | <20 (6)
It is desirable to satisfy the following condition.

  In addition to or in addition to the opening, it is desirable that a ring-shaped slit opening that is rotationally symmetric about the central axis is provided in the vicinity of the first transmission surface of the front group.

  Further, at least the reflection surface may be cut along a cross section including the central axis so that the angle of view around the central axis is narrower than 360 °.

  According to the present invention described above, an image having an angle of view of 360 ° omnidirectional (entire circumference) having a good resolution is obtained without being affected by flare light and having good aberrations. An optical system for projecting an image at an angle of view can be obtained.

The optical system of the present invention will be described below based on examples. Examples 2 and 3 are reference examples and are excluded from the examples of the present invention.

  FIG. 1 is a cross-sectional view taken along a central axis (rotation symmetry axis) 1 of an optical system of Example 1 described later, and FIG. 2 is a plan view showing an optical path in the optical system. The optical system of the present invention will be described with reference to FIGS. Although the following description will be described as an imaging optical system, it can also be used as a projection optical system that projects an image in all 360 ° azimuths (entire circumference) with the optical path reversed. 2A shows only an optical path incident from an azimuth angle 0 ° direction, and FIG. 2B shows an optical path incident from ± 10 ° direction in addition to the optical path.

  The optical system of the present invention includes a front group 10 that is rotationally symmetric about the central axis 1 and a rear group 20 that is rotationally symmetric about the central axis 1, and a light beam 2 incident from a distant object is The image is formed at a position deviating from the central axis 1 of the image plane 30 perpendicular to the central axis 1 through the rear group 20 in order.

  The front group 10 is made of a transparent medium such as a resin having a rotational symmetry around the central axis 1 and a refractive index greater than 1. The two internal reflection surfaces 12 and 13 and the two transmission surfaces (incident surface and emission surface). 11 and 14. The inner reflection surfaces 12 and 13 and the transmission surfaces 11 and 14 also have a rotationally symmetric shape around the central axis 1. The rear group 20 is composed of a coaxial refractive optical system such as a lens system having a positive power and rotational symmetry about the central axis 1.

  The transparent medium of the front group 10 includes a first transmission surface 11, a first reflection surface 12, a second reflection surface 13, and a second transmission surface 14. The first transmission surface 11 is an object with respect to the central axis 1. The first reflection surface 12 is disposed on the opposite side of the first transmission surface 11 across the central axis 1, is disposed on the image plane 30 side of the first transmission surface 11, and the second reflection surface 13. Is disposed on the same side as the first transmission surface 11 with respect to the central axis 1, is disposed on the opposite side of the image surface 30 from the first transmission surface 11, and the second transmission surface 14 is imaged from the first transmission surface 11. It arrange | positions at the surface 30 side.

  The light beam 2 incident from a distance enters the transparent medium through the first transmission surface 11, and the image plane is formed on the first reflection surface 12 disposed on the opposite side of the first transmission surface 11 with the central axis 1 interposed therebetween. 30 is reflected to the image surface 30 side by the second reflecting surface 13 which is reflected on the opposite side of the central axis 1 and disposed on the same side as the first transmitting surface 11 with respect to the central axis 1, and passes through the second transmitting surface 14 to be a transparent medium. From the central axis 1 of the image plane 30 through the circular aperture 5 and the rear group 20 that are arranged coaxially with the central axis 1 between the front group 10 and the rear group 20 and constitute a diaphragm. An image is formed at a predetermined position in the radial direction.

  The role of the front group 10 is to receive a light beam coming from the entire peripheral image toward the rotational symmetry axis (center axis) 1 and convert it into an annular aerial image at an arbitrary position. The role of the rear group 20 is to project the annular aerial image onto the plane of the image sensor located on the image plane 30, and the curvature of field that is insufficiently corrected in the front group 10. It is also possible to correct the astigmatism so as to be complementary in the rear group 20.

  FIG. 5 is a cross-sectional view taken along the central axis (rotation symmetry axis) 1 of the optical system of Example 2 described later, and FIG. 6 is a plan view similar to FIG. 2 showing the optical path in the optical system. It is. Another optical system of the present invention will be described with reference to FIGS. Although the following description will be described as an imaging optical system, it can also be used as a projection optical system that projects an image in all 360 ° azimuths (entire circumference) with the optical path reversed.

  Another optical system of the present invention also includes a front group 10 that is rotationally symmetric about the central axis 1 and a rear group 20 that is rotationally symmetric about the central axis 1, and the light beam 2 incident from a distant object is An image is formed at a position deviating from the central axis 1 of the image plane 30 perpendicular to the central axis 1 through the group 10 and the rear group 20 in order.

  The front group 10 is made of a transparent medium such as a resin having a rotational symmetry around the central axis 1 and a refractive index greater than 1. The two internal reflection surfaces 12 and 13 and the two transmission surfaces (incident surface and emission surface). 11 and 14. The inner reflection surfaces 12 and 13 and the transmission surfaces 11 and 14 also have a rotationally symmetric shape around the central axis 1. The rear group 20 is composed of a coaxial refractive optical system such as a lens system having a positive power and rotational symmetry about the central axis 1.

  The transparent medium of the front group 10 includes a first transmission surface 11, a first reflection surface 12, a second reflection surface 13, and a second transmission surface 14. The first transmission surface 11 is an object with respect to the central axis 1. The first reflection surface 12 is disposed on the opposite side of the first transmission surface 11 across the central axis 1, is disposed on the opposite side of the image surface 30 from the first transmission surface 11, and is second reflected. The surface 13 is disposed on the same side as the first transmission surface 11 with respect to the central axis 1, is disposed on the opposite side of the image surface 30 from the first transmission surface 11, and the second transmission surface 14 is the second reflection surface 13. It is arranged closer to the image plane 30 side.

  The light beam 2 incident from a distance enters the transparent medium through the first transmission surface 11, and the image plane is formed on the first reflection surface 12 disposed on the opposite side of the first transmission surface 11 with the central axis 1 interposed therebetween. 30 is reflected to the image surface 30 side by the second reflecting surface 13 which is reflected on the opposite side of the central axis 1 and disposed on the same side as the first transmitting surface 11 with respect to the central axis 1, and passes through the second transmitting surface 14 to be a transparent medium. From the central axis 1 of the image plane 30 through the circular aperture 5 and the rear group 20 that are arranged coaxially with the central axis 1 between the front group 10 and the rear group 20 and constitute a diaphragm. An image is formed at a predetermined position in the radial direction.

  The role of the front group 10 is to receive a light beam coming from the entire peripheral image toward the rotational symmetry axis (center axis) 1 and convert it into an annular aerial image at an arbitrary position. The role of the rear group 20 is to project the annular aerial image onto the plane of the image sensor located on the image plane 30, and the curvature of field that is insufficiently corrected in the front group 10. It is also possible to correct the astigmatism so as to be complementary in the rear group 20.

  In the case of the embodiment shown in FIGS. 1 and 5, a circular opening 5 constituting a stop is arranged coaxially with the central axis 1 between the front group 10 and the rear group 20. The entrance pupil is formed by back-projecting the aperture 5 arranged on the central axis by the front group 10, and the feature of the present invention is that the entrance pupil is a first transmission surface (incident surface) in the meridional section. 11 is projected as the sagittal direction entrance pupil 6X on the central axis (rotation symmetry axis) 1 in the sagittal section while being arranged as the entrance pupil 6Y in the meridional direction in the vicinity of 11. In the conventional example (Patent Document 1), since the entrance pupil of the meridional section and the entrance pupil of the sagittal section are both arranged on the central axis, the flare stop for cutting harmful light cannot be effectively arranged. .

The meridional section and the sagittal section are defined as shown in FIG. FIG. 13A is a perspective view showing a schematic optical path of the optical system of the present invention, and FIG. 13B is a view showing a cross section at the center of the angle of view on the image plane 30. That is, a cross section is the meridional section that includes the center ray (chief ray) 2 ₀ of the center light beam leading to the center axis (rotationally symmetric axis) 1 and the center of the angle of view of the optical system, the central light beam orthogonal to the meridional section (main beam) section including the 2 ₀ is a sagittal section.

  In the optical system of the present invention, the curvature of a meridional section of an arbitrary shape that determines the shapes of the reflecting surfaces 12, 13 and the refracting surfaces 11, 14 by rotating around the central axis 1, and the central axis 1 in that case By independently giving the curvature of rotation, i.e., the curvature of the sagittal section, the aperture 5 is back-projected and imaged as a single image 6Y 'and back-projected and imaged again in the meridional section. By disposing the entrance pupil 6Y in the vicinity of the first transmission surface 11 of the front group 10, unnecessary light entering the front group 10 can be significantly cut, and flare can be reduced. Is.

  On the other hand, in the sagittal cross section orthogonal to the central axis 1, since it is a rotationally symmetric system, the luminous flux also passes through the rotational symmetry, and the luminous flux having the same image height on the ring always has 2 on the central axis 1 as the rotational center. Pass through once (FIGS. 2B and 6B). Accordingly, in the sagittal section, the light beam reaching the image plane 30 on the circumference passes the central axis 1 twice and then reaches the image plane 30, and the back-projected aperture 5 of the diaphragm of the sagittal section. The entrance pupil 6X in the sagittal cross section, which is an image of the above, exists on the central axis 1 (the image 6X ′ is an image of the aperture 5 formed at the first time).

  In order to take such an arrangement, the front group 10 has a rotationally symmetric shape formed by rotating a line segment having an arbitrary shape whose curvature can be freely controlled in the meridional section and the sagittal section around the central axis 1. It is important to compose in terms of surfaces. Further, in the front group 10, since the light is reflected or transmitted by the surfaces 11 to 14 having decentered power, decentration aberrations are greatly generated. In order to correct this, in particular, the reflecting surfaces 12 and 13 may use surface shapes obtained by rotating arbitrary-shaped line segments that do not have symmetry planes using odd-order terms or the like in arbitrary-shaped line segments. Become important.

  In such a configuration, when the central axis 1 is the Y axis and the cross section including the central axis 1 (FIGS. 1 and 5) is the YZ plane, as described above, the entrance pupil 6Y in the meridional cross section is in front. By arranging it in the vicinity of the first transmission surface 11 of the group 10, it becomes possible to arrange a slit-like flare stop in the vicinity of the entrance pupil 6Y in the Y direction, and to cut unnecessary light with this flare stop. Is possible.

  The flare stop can be such a mechanical slit-like stop, or a casing for the purpose of protecting the optical system, or a concentric transparent pipe-like shape on the central axis 1 painted black where the light does not pass. It may be a thing. Moreover, it is also possible to use together by using the reflective coating part of the reflective surface 12 together, carrying out the graining process of the optically unused area | region of the front group 10, or apply | coating black paint.

  In the optical system of the present invention shown in FIGS. 1 and 5, it is preferable to combine the number of back projection relays of the diaphragm 5 in the sagittal section and the number of back projection relays of the diaphragm 5 in the meridional section. In Example 1 and Example 2 described later, the first transmission surface 11 and the first reflection surface 12 are arranged with the central axis 1 therebetween. Further, the second reflecting surface 13 is disposed on the opposite side of the first reflecting surface 12 with the central axis 1 interposed therebetween, and is disposed on the same side as the first transmitting surface 11. Therefore, as shown in FIGS. 2B and 6B, the light beam having the sagittal section angle of view passes through the central axis 1 twice and enters the diaphragm 5. This means that the back-projected aperture image of the aperture is imaged once as the image 6X ′ between the first reflecting surface 12 and the second reflecting surface 13 on the central axis 1, and the first transmitting surface 11 and the first Even between the reflection surfaces 12, an image 6X is formed on the central axis 1. In other words, in the sagittal section, the first and second embodiments have a one-time relay arrangement that forms an image of the aperture image formed once, and then forms another image. This means that it is better to correct the aberration when the power of the sagittal section of each of the surfaces 11 to 14, particularly the reflecting surfaces 12 and 13, is relatively the same as that of the meridional section. The configuration is preferable for aberration correction.

  However, if the back projection position of the diaphragm 5 of the meridional section is also set on the central axis 1, the effective diameter of the incident surface becomes large, and the occurrence of flare increases, which contradicts the gist of the present invention. Furthermore, when the effective diameter of each surface increases, interference between surfaces occurs, and it becomes impossible to take a wide viewing angle in the vertical direction (direction along the central axis 1). Therefore, in the present invention, as described above, the most object side aperture image 6Y of the back-projected aperture image in the meridional section is arranged in the vicinity of the first transmission surface 11.

  Next, in the optical system of the present invention shown in FIGS. 1 and 5, the first transmission surface 11 and the first reflection surface 12 are disposed substantially opposite to each other with the central axis 1 interposed therebetween. However, the first reflecting surface 12 is disposed adjacent to the first transmitting surface 11 in the direction of the central axis 1 and on which the light beam enters from the opposite side of 180 °. In order to make this arrangement possible, the first transmission surface 11 is inclined with respect to the central axis 1, and the light beam is refracted by the first transmission surface 11, whereby the first transmission surface 11 and the first transmission surface 11 are arranged. The interference of the reflecting surface 12 is avoided. However, refracting the light beam on the first transmission surface 11 causes chromatic aberration due to chromatic dispersion. Of course, it is possible to correct by the second transmission surface 14, but it is preferable that the generation itself is small. For this purpose, it is desirable to reduce the refraction angle of the first transmission surface 11 so that the first transmission surface 11 and the first reflection surface 12 are adjacent to each other.

  When the vertical angle of the image plane is directed to the zenith (FIG. 5), if the angle of view in the upper limit direction is set so that observation is centered on the downward direction (ground), the angle at which the first transmission surface 11 is refracted is small. The light beam after passing through the first transmission surface 11 travels upward. Therefore, even if the refraction angle of the first transmission surface 11 is small, the first reflection surface 12 can be disposed on the first transmission surface 11 (Example 2).

  Similarly, when the angle of view is set so that the image is observed centering on the upper direction (FIG. 1), even if the angle of refraction at the first transmission surface 11 is small, the light beam transmitted through the first transmission surface 11 proceeds downward. . Therefore, even if the refraction angle of the first transmission surface 11 is small, the first reflection surface 12 can be disposed below the first transmission surface 11 (Example 1).

For this purpose, the position of the first transmission surface 11 with respect to the entire front group 10 is important. When the height of the front group 10 is taken in the direction perpendicular to the image surface 30, the upper end of the front group 10 (the side opposite to the image surface 30). ) To the lower end (image plane 30 side) H1, and the height from the upper end (opposite side of the image plane 30) of the front group 10 to the entrance pupil 6Y is H2.
When mainly observing the upper side opposite to the image plane (Example 1),
1.5 <H1 / H2 <100 (1)
It is preferable to satisfy the following condition.

When mainly observing the lower part of the image plane side (Example 2),
0.01 <H1 / H2 <5 (2)
It is preferable to satisfy the following condition.

When mainly observing the lateral direction perpendicular to the central axis 1 (Examples 1 and 2),
0.5 <H1 / H2 <10 (3)
It is preferable to satisfy the following condition.

  Although the numerical values of the upper limit and the lower limit to be taken for H1 / H2 differ depending on the observation direction, the meanings are the same, and the lower limits of 1.5 (conditional expression (1)) and 0.01 (conditional expression (2) ), 0.5 (conditional expression (3)), the first transmission surface 11 is positioned too low, and the interference between the first reflection surface 12 and the first transmission surface 12 with respect to the respective observation directions. It becomes impossible to arrange without. When the upper limit of 100 (conditional expression (1)), 5 (conditional expression (2)), and 10 (conditional expression (3)) is exceeded, interference between the second reflecting surface 13 and the first transmitting surface 11 is caused. As a result, it becomes impossible to arrange the second reflecting surface 13 in each observation direction. Further, if the upper and lower limits are exceeded with respect to the respective observation directions, even if the first reflection surface 12 or the second reflection surface 13 disposed adjacent to the first transmission surface 11 can be arranged, the observation angle of view can be reduced. It becomes impossible to take large.

More preferably,
When mainly observing the upper side opposite to the image plane,
2 <H1 / H2 <10 (1-1)
It is preferable to satisfy the following condition.

When mainly observing the lower part of the image side,
0.1 <H1 / H2 <5 (2-1)
It is preferable to satisfy the following condition.

When mainly observing the lateral direction perpendicular to the central axis 1,
1.5 <H1 / H2 <4 (3-1)
It is preferable to satisfy the following condition.

  As described above, the optical system of the present invention is characterized in that the entrance pupil 6Y having a section including the central axis 1 (meridional section) is projected in the vicinity of the first transmission surface 11, and a flare stop for preventing ghosts and the like. Can be arranged effectively. As a result, the effective area of the incident surface 11 of the optical system can be reduced in the meridional cross section, and unnecessary light incident on the front group 10 can be effectively prevented, which is effective for fundamental flare countermeasures. To do. For that purpose, it is important to satisfy the following conditional expression.

In the meridional cross section, the optical path length from the entrance pupil 6Y position to the stop 5 position is A, the optical path length from the entrance pupil 6Y to the first transmission surface 11 of the front group 10 and the light ray direction being positive is B, and The ratio is A / B. A / B represents the degree to which the entrance pupil 6Y is disposed in the vicinity of the entrance surface 11 of the front group 10. | A / B |
5 <| A / B | (4)
It is important to satisfy the following conditions.

  If the lower limit of 5 of the conditional expression (4) is exceeded, the entrance pupil 6Y is separated from the first optical system surface 11. The effective system of the first surface 11 becomes large, and harmful flare light incident on the front group 10 cannot be effectively cut. The larger this value is, the more effectively the flare stop for preventing flare can work.

More preferably,
20 <| A / B | (4-1)
It is preferable to satisfy the following conditions.

The distance between the entrance pupil 6Y position of the meridional section and the rotation center axis 1 where the entrance pupil 6X of the sagittal section is located is C, and the absolute distance of the focal length Ffy of the front group 10 in the YZ direction (meridional section) is absolute. The ratio of the value | Ffy |
0.1 <C / | Ffy | (5)
It is important to satisfy the following conditions. This conditional expression is a condition regarding the distance between the entrance pupil 6Y position of the meridional section and the entrance pupil 6X of the sagittal section. When the lower limit of 0.1 is exceeded, the position of the entrance pupil 6Y of the meridional section is the central axis 1 (incidence of the sagittal section). The pupil 6X position is approached, and an effective flare stop cannot be arranged.

The focal length Ffx in the XZ direction and the focal length Ffy in the YZ direction of the front group 10 are within the meridional section (YZ direction) and the sagittal section (XZ direction) of the front group 10. track and subordinate rays parallel spaced a small distance (0.1 mm) to it and the principal ray (center ray) 2 ₀ of the light beam 2 incident on the center of the angle of view, dependent ray and the principal ray when emitted from the front unit 10 The focal length Ffx of the front group 10 in the XZ direction and the focal length Ffy in the YZ direction of the front group 10 are obtained. The same applies to the focal length Fx in the YZ direction and the focal length Fy in the YZ direction of the entire optical system.

More preferably,
0.3 <C / | Ffy | (5-1)
It is preferable to satisfy the following conditions.

Next, the magnification of the image 6Y of the aperture 5 that is back-projected only by the meridional cross section is obtained by tracing rays that are inclined by a small angle of 0.01 radians (θ) from the position of the entrance pupil 6Y to the aperture 5; If this is the pupil magnification Pβ,
0.05 <| Pβ | <20 (6)
It is preferable to satisfy the following conditions.

  This condition relates to the projection magnification of the aperture image projected on the aperture 5 coaxial with the central axis 1 from the back-projected aperture image 6Y on the object side. Naturally, the closer the projection magnification Pβ is to 1, the shorter the distance between the object images. However, in order to balance the front group 10 and the rear group 20, it is important to satisfy the conditional expression (6), and the lower limit. If this value exceeds 0.05, the angle of view incident on the rear group 20 becomes larger than the angle of view incident on the front group 10, the burden of aberration correction on the rear group 20 increases, and a preferable balance of aberration correction cannot be achieved. If the upper limit of 20 is exceeded, the incident field angle of the rear group 20 decreases, but the diameter of the light beam incident on the rear group 20 increases, making it difficult to correct the occurrence of spherical aberration and the like in the rear group 20. Further, the angle of view incident on the front group 10 is increased, and a burden such as curvature of field and astigmatism is applied. The front group 10 is increased in size and an aberration correction is applied excessively, which is not preferable.

More preferably,
0.1 <| Pβ | <10 (6-1)
It is preferable to satisfy the following conditions.

  Fx, Fy, Fx / Fy, Ffx, Ffy, Ffx / Ffy, A, B, | A / B |, C, C / Ffy, | Pβ |, H1, H2, H1 / H2 is as follows.

Example 1 Example 2 Example 3
Fx 2.598 2.371 -1.880
Fy 2.112 1.956 -2.459
Fx / Fy 1.230 1.212 0.765
Ffx -19.417 -16.393 11.249
Ffy -20.619 -23.364 13.316
Ffx / Ffy 0.942 0.702 0.845
A 137.118 147.657 101.085
B -0.012 -0.108 -0.059
｜ A / B ｜ 11013.506 1370.0 1709.608
C 15.453 10.159 11.074
C / Ffy | 0.749 0.435 0.832
｜ P β ｜ 5.618 4.098 1.757
H1 26.000 29.500 34.500
H2 5.000 29.000 13.000
H1 / H2 5.200 1.017 2.654
.

  Hereinafter, Examples 1 to 3 of the optical system of the present invention will be described in more detail. The configuration parameters of these optical systems will be described later. The configuration parameters of these embodiments are based on the result of tracking the normal ray from the object plane to the image plane 30 through the front group 10 and the rear group 20, as shown in FIG.

  In the forward ray tracing, for example, as shown in FIG. 1, the coordinate system uses the position where the entrance pupil 6Y is projected on the rotational symmetry axis (center axis) 1 as the origin of the eccentric optical surface of the eccentric optical system, and the rotational symmetry axis (center). 1) A direction away from the image plane 30 on the axis 1 is defined as a positive Y-axis direction, and a plane in FIG. 1 is defined as a YZ plane. 1 is the Z axis positive direction, and the Y axis, the Z axis, and the axis constituting the right-handed orthogonal coordinate system are the X axis positive direction. .

  For the decentered surface, the amount of decentering from the center of the origin of the optical system in the coordinate system in which the surface is defined (X-axis direction, Y-axis direction, and Z-axis direction are X, Y, and Z, respectively) and the optical system The inclination angles (α, β, γ (°), respectively) of the coordinate system defining each surface centered on the X axis, Y axis, and Z axis of the coordinate system defined at the origin are given. In this case, positive α and β mean counterclockwise rotation with respect to the positive direction of each axis, and positive γ means clockwise rotation with respect to the positive direction of the Z axis. Note that the α, β, and γ rotations of the central axis of the surface are performed by rotating the coordinate system defining each surface counterclockwise around the X axis of the coordinate system defined at the origin of the optical system. Then rotate it around the Y axis of the new rotated coordinate system by β and then rotate it around the Z axis of another rotated new coordinate system by γ. It is.

  Further, among the optical action surfaces constituting the optical system of each embodiment, when a specific surface and a subsequent surface constitute a coaxial optical system, a surface interval is given, in addition, the curvature radius of the surface, The refractive index and Abbe number of the medium are given according to conventional methods.

  It should be noted that a term relating to an aspheric surface for which no data is described in the constituent parameters described later is zero. The refractive index and the Abbe number are shown for the d-line (wavelength 587.56 nm). The unit of length is mm. The eccentricity of each surface is expressed by the amount of eccentricity from the position where the entrance pupil 6Y is projected onto the rotational symmetry axis (center axis) 1 as described above.

  The aspheric surface is a rotationally symmetric aspheric surface given by the following definition.

^{Z = (Y 2 / R)} / [1+ {1- (1 + k) Y 2 / R 2} 1/2]
+ AY ⁴ + bY ⁶ + cY ⁸ + dY ¹⁰ +...
... (a)
However, Z is taken as an axis, and Y is taken in a direction perpendicular to the axis. Here, R is a paraxial radius of curvature, k is a conic constant, a, b, c, d,... Are fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients, respectively. The Z axis of this defining formula is the axis of a rotationally symmetric aspherical surface.

  The extended rotation free-form surface is a rotationally symmetric surface given by the following definition.

  First, the following curve (b) passing through the origin on the YZ coordinate plane is determined.

^{Z = (Y 2 / RY)} / [1+ {1- (C 1 +1) Y 2 / RY 2} 1/2]
C ₂ Y + C ₃ Y ² + C ₄ Y ³ + C ₅ Y ⁴ + C ₆ Y ⁵ + C ₇ Y ⁶
+ ··· + C ₂₁ Y ²⁰ + ··· + C _{n + 1} Y ⁿ + ····
... (b)
Next, a curve F (Y) obtained by rotating the curve (b) in the positive direction of the X-axis and turning it counterclockwise to be positive is determined. This curve F (Y) also passes through the origin on the YZ coordinate plane.

  The curve F (Y) is translated in the positive Z direction by a distance R (or negative Z direction if negative), and then the rotationally symmetric surface formed by rotating the translated curve around the Y axis is expanded and rotated. Let it be a free-form surface.

  As a result, the extended rotation free-form surface becomes a free-form surface (free-form curve) in the YZ plane and a circle with a radius | R | in the XZ plane.

  From this definition, the Y-axis becomes the axis of the extended rotation free-form surface (rotation symmetry axis).

Where RY is the radius of curvature of the spherical term in the YZ section, C ₁ is the conic constant, C ₂ , C ₃ , C ₄ , C ₅ . Aspheric coefficient.

  In the optical system of the present invention, at least one reflecting surface of the front group 10 is such an extended rotation free-form surface, and has at least an odd-order term when expressed by a polynomial in the YZ section. It is desirable to have a rotationally symmetric shape formed by rotating an arbitrary-shaped line segment having no symmetry plane around the central axis 1. By providing such a surface shape to at least one reflecting surface, it is possible to provide an optical system with good resolving power by correcting decentration aberration that is unavoidable in a reflecting optical system, and reducing the size of the optical system. Can be realized.

  A sectional view taken along the central axis (rotation symmetry axis) 1 of the optical system of Example 1 is shown in FIG. 1, and a plan view showing an optical path in the optical system is shown in FIG. 2A shows only an optical path incident from an azimuth angle 0 ° direction, and FIG. 2B shows an optical path incident from ± 10 ° direction in addition to the optical path.

  The optical system of this embodiment includes a front group 10 that is rotationally symmetric about the central axis 1, a rear group 20 that is rotationally symmetric about the central axis 1, and the central axis 1 between the front group 10 and the rear group 20. A light beam 2 that is formed of a coaxially arranged aperture 5 and is incident from a distant object passes through the front group 10 and the rear group 20 in order, and is connected to a position off the central axis 1 of the image plane 30 perpendicular to the central axis 1. When the central axis 1 is set to be vertical (vertical direction), for example, an image having an angle of view of 360 ° omnidirectional (all circumferences), the zenith direction is directed to the central direction of the image, and the horizon An annular image is formed on the image plane 30 so that becomes an outer circle.

  The front group 10 is made of a transparent medium such as a resin whose refractive index is rotationally symmetric around the central axis 1 and has two internal reflection surfaces 12 and 13 and two transmission surfaces 11 and 14. is there. The inner reflection surfaces 12 and 13 and the transmission surfaces 11 and 14 also have a rotationally symmetric shape around the central axis 1. The rear group 20 includes a lens system including two lenses including four lenses L1 to L4.

  The transparent medium of the front group 10 includes a first transmission surface 11, a first reflection surface 12, a second reflection surface 13, and a second transmission surface 14, and the first transmission surface 11 is on the object side with respect to the central axis 1. The first reflection surface 12 is disposed on the opposite side of the first transmission surface 11 across the central axis 1, is disposed on the image plane 30 side with respect to the first transmission surface 11, and the second reflection surface 13 is the center. It is disposed on the same side as the first transmission surface 11 with respect to the axis 1, is disposed on the opposite side of the image surface 30 from the first transmission surface 11, and the second transmission surface 14 is image surface 30 from the first transmission surface 11. Arranged on the side.

  The light beam 2 incident from a distance enters the transparent medium through the first transmission surface 11, and the image plane is formed on the first reflection surface 12 disposed on the opposite side of the first transmission surface 11 with the central axis 1 interposed therebetween. 30 is reflected to the image surface 30 side by the second reflecting surface 13 which is reflected on the opposite side of the central axis 1 and disposed on the same side as the first transmitting surface 11 with respect to the central axis 1, and passes through the second transmitting surface 14 to be a transparent medium. From the central axis 1 of the image plane 30 through the circular aperture 5 and the rear group 20 that are arranged coaxially with the central axis 1 between the front group 10 and the rear group 20 and constitute a diaphragm. An image is formed at a predetermined position in the radial direction. The first transmission surface 11, the first reflection surface 12, and the second reflection surface 13 of the front group 10 are configured as extended rotation free-form surfaces. However, the conic constant is zero. The second transmission surface 14 is formed of a rotationally symmetric aspherical surface having a top on the central axis 1.

  The lens system constituting the rear group 20 includes, in order from the front group 10 side, a cemented lens of a negative meniscus lens L1 having a convex surface facing the front group 10 and a biconvex positive lens L2, a biconvex positive lens L3, and the front group 10. And a cemented lens of a negative meniscus lens L4 having a concave surface on the side.

  When the central axis 1 is oriented in the vertical direction and the image plane 30 is oriented in the zenith direction, the central light beam 2 incident from a distance in the direction of the elevation angle of 45 ° is refracted by the first transmission surface 11 of the incident surface. The light beam that enters the transparent medium of the group 10 and is reflected in the order of the first reflecting surface 12 and the second reflecting surface 13 is refracted by the second transmitting surface 14 and exits from the transparent medium of the front group 10, thereby opening the aperture 5. And enters the rear group 20 and forms an image at a predetermined radial position away from the central axis 1 of the image plane 30.

  In the optical system of this embodiment, an aperture (aperture) 5 positioned between the front group 10 and the rear group 20 is projected on the object side, and is imaged as a single image 6Y ′ in the meridional section, and back-projected again. The entrance pupil 6Y in the meridional section imaged in this way is formed in the vicinity of the first transmission surface 11 of the front group 10, and the image 6X is placed on the central axis (rotation symmetry axis) 1 in the sagittal section. ', 6X is imaged twice, and an entrance pupil 6X is formed on the central axis 1.

In the optical system of this embodiment, light fluxes 2, 3U, 3L incident from a distance through the entrance pupil 6Y (light flux 3U is a light flux incident from a distant sky side, 3L is a light flux incident from a distant ground side). In the cross section including the central axis 1 (meridional cross section: FIG. 1), an image is formed once at the position 4Y ₁ between the first reflecting surface 12 and the second reflecting surface 13, and the second reflecting surface 13 and the second reflecting surface are again formed. , at the position 4Y ₂ between the permeate surface 14, also perpendicular to the plane including the center axis 1 plane including the center ray 2 ₀ of the light beam: in (sagittal section 2) in the first reflecting surface near position 4X ₁ and the second reflecting surface 13 is 2 Kaiyuizo a position 4X ₂ between the second transmitting surface 14.

The specification of this Example 1 is
Horizontal field of view 360 °
Vertical angle of view 90 ° (center angle of view 45 ° (elevation angle))
Entrance pupil diameter 2.2mm
Image size φ2.22 to φ6.16mm
It is.

  In the optical system of Example 1, the first reflecting surface 12 is disposed on the image surface 30 side from the first transmitting surface 11, and the second reflecting surface 13 is disposed on the opposite side of the image surface 30 from the first reflecting surface 12. The second transmission surface 14 is arranged on the image plane 30 side with respect to the first transmission surface 11.

  In the configuration in which the image plane 30 is arranged in parallel with the ground, the optical system according to the first embodiment is preferably used for an angle of view looking up at the sky side.

  FIG. 3 shows the lateral aberration of the entire optical system of this example. In this lateral aberration diagram, the angle shown in the center indicates the vertical angle of view, and the lateral aberration in the Y direction (meridional direction) and X direction (sagittal direction) at that angle of view. The positive angle of view indicates the depression angle, and the negative angle of view indicates the elevation angle. same as below.

  FIG. 4 is a diagram showing the distortion in the vertical direction of this embodiment. The curve connected with ♦ indicates the image height (from the central axis 1) on the image plane 30 with respect to the vertical incident angle of view of the optical system of the first embodiment. It is the graph which plotted the image height of the radial direction. A thick solid line represents a case where the image height is proportional to the incident angle of view (in the case of IH∝f · θ. Here, IH: image height, f: focal length, θ: angle of view). same as below.

  FIG. 5 is a sectional view taken along the central axis (rotation symmetry axis) 1 of the optical system of Example 2, and FIG. 6 is a plan view showing the same optical path as FIG. 2 in the optical system.

  The optical system of this embodiment includes a front group 10 that is rotationally symmetric about the central axis 1, a rear group 20 that is rotationally symmetric about the central axis 1, and the central axis 1 between the front group 10 and the rear group 20. A light beam 2 that is formed of a coaxially arranged aperture 5 and is incident from a distant object passes through the front group 10 and the rear group 20 in order, and is connected to a position off the central axis 1 of the image plane 30 perpendicular to the central axis 1. When the central axis 1 is set to be vertical (vertical direction), for example, an image having an angle of view of 360 ° omnidirectional (all circumferences), and the horizon becomes a circle inside the image, An annular image whose direction is an outer circle is formed on the image plane 30.

  The front group 10 is made of a transparent medium such as a resin whose refractive index is rotationally symmetric around the central axis 1 and has two internal reflection surfaces 12 and 13 and two transmission surfaces 11 and 14. is there. The inner reflection surfaces 12 and 13 and the transmission surfaces 11 and 14 also have a rotationally symmetric shape around the central axis 1. The rear group 20 includes a lens system including three lenses including five lenses L1 to L5.

  The transparent medium of the front group 10 includes a first transmission surface 11, a first reflection surface 12, a second reflection surface 13, and a second transmission surface 14, and the first transmission surface 11 is on the object side with respect to the central axis 1. The first reflection surface 12 is disposed on the opposite side of the first transmission surface 11 with the central axis 1 interposed therebetween, and is disposed on the opposite side of the image surface 30 from the first transmission surface 11. Is disposed on the same side as the first transmission surface 11 with respect to the central axis 1, disposed on the opposite side of the image surface 30 from the first reflection surface 12, and the second transmission surface 14 is imaged from the second reflection surface 13. It arrange | positions at the surface 30 side.

  The light beam 2 incident from a distance enters the transparent medium through the first transmission surface 11, and the image plane is formed on the first reflection surface 12 disposed on the opposite side of the first transmission surface 11 with the central axis 1 interposed therebetween. 30 is reflected to the image surface 30 side by the second reflecting surface 13 which is reflected on the opposite side of the central axis 1 and disposed on the same side as the first transmitting surface 11 with respect to the central axis 1, and passes through the second transmitting surface 14 to be a transparent medium. From the central axis 1 of the image plane 30 through the circular aperture 5 and the rear group 20 that are arranged coaxially with the central axis 1 between the front group 10 and the rear group 20 and constitute a diaphragm. An image is formed at a predetermined position in the radial direction. The first transmission surface 11, the first reflection surface 12, and the second reflection surface 13 of the front group 10 are configured as extended rotation free-form surfaces. However, the conic constant is zero. The second transmission surface 14 is formed of a rotationally symmetric aspherical surface having a top on the central axis 1.

  The lens system constituting the rear group 20 includes, in order from the front group 10 side, a positive meniscus lens L1 having a concave surface facing the front group 10, a cemented lens of a biconcave negative lens L2 and a biconvex positive lens L3, and a biconvex lens. It consists of a cemented lens of a positive lens L4 and a biconcave negative lens L5.

  When the central axis 1 is oriented in the vertical direction and the image plane 30 is oriented in the zenith direction, the central light beam 2 incident from a far angle in the direction of the depression angle of 35 ° is refracted by the first transmission surface 11 of the incident surface. The light beam that enters the transparent medium of the group 10 and is reflected in the order of the first reflecting surface 12 and the second reflecting surface 13 is refracted by the second transmitting surface 14 and exits from the transparent medium of the front group 10, thereby opening the aperture 5. And enters the rear group 20 and forms an image at a predetermined radial position away from the central axis 1 of the image plane 30.

  In the optical system of this embodiment, an aperture (aperture) 5 positioned between the front group 10 and the rear group 20 is projected on the object side, and is imaged as a single image 6Y ′ in the meridional section, and back-projected again. The entrance pupil 6Y in the meridional section imaged in this way is formed in the vicinity of the first transmission surface 11 of the front group 10, and the image 6X is placed on the central axis (rotation symmetry axis) 1 in the sagittal section. ', 6X is imaged twice, and an entrance pupil 6X is formed on the central axis 1.

In the optical system of this embodiment, the light fluxes 2, 3U, and 3L incident from a distance through the entrance pupil 6Y (the light flux 3U is a light flux incident from the far sky side (in this case, the horizontal direction), and 3L is a distant ground. The light beam incident from the side) is imaged once at a position 4Y ₁ in the vicinity of the first reflecting surface 12 in the section including the central axis 1 (meridional section: FIG. 5), and again with the second reflecting surface 13 and the second reflecting surface 13. , at the position 4Y ₂ between the permeate surface 14, also perpendicular to the plane including the center axis 1 plane including the center ray 2 ₀ of the light beam: in (sagittal section 6) in the first reflecting surface near position 4X ₁ and the second reflecting surface 13 is 2 Kaiyuizo a position 4X ₂ between the second transmitting surface 14.

The specification of Example 2 is
Horizontal field of view 360 °
Vertical angle of view 70 ° (Center angle of view 35 ° (Depression angle))
Entrance pupil diameter 2.30mm
Image size φ2.24 to φ5.93 mm
It is.

  In the optical system of Example 2, the first reflecting surface 12 is disposed on the opposite side of the image surface 30 from the first transmitting surface 11, and the second reflecting surface 13 is on the opposite side of the image surface 30 from the first reflecting surface 12. The second transmission surface 14 is disposed closer to the image plane 30 than the second reflection surface 13.

  In the configuration in which the image plane 30 is arranged in parallel with the ground, the optical system according to the second embodiment is preferably used for an angle of view overlooking the ground.

  FIG. 7 shows the lateral aberration of the entire optical system of this example. FIG. 8 shows the vertical distortion of this embodiment.

  FIG. 9 is a sectional view taken along the central axis (rotation symmetry axis) 1 of the optical system of Example 3, and FIG. 6 is a plan view showing the same optical path as FIG. 10 in the optical system.

  The optical system of this embodiment includes a front group 10 that is rotationally symmetric about the central axis 1, a rear group 20 that is rotationally symmetric about the central axis 1, and the central axis 1 between the front group 10 and the rear group 20. A light beam 2 that is formed of a coaxially arranged aperture 5 and is incident from a distant object passes through the front group 10 and the rear group 20 in order, and is connected to a position off the central axis 1 of the image plane 30 perpendicular to the central axis 1. When the central axis 1 is set to be vertical (vertical direction), for example, an image having an angle of view of 360 ° omnidirectional (all circumferences), the zenith direction is directed to the central direction of the image, and the horizon An annular image is formed on the image plane 30 so that becomes an outer circle.

  The front group 10 is made of a transparent medium such as a resin whose refractive index is rotationally symmetric around the central axis 1 and has two internal reflection surfaces 12 and 13 and two transmission surfaces 11 and 14. is there. The inner reflection surfaces 12 and 13 and the transmission surfaces 11 and 14 also have a rotationally symmetric shape around the central axis 1. The rear group 20 includes a lens system including two lenses including four lenses L1 to L4.

  The transparent medium of the front group 10 includes a first transmission surface 11, a first reflection surface 12, a second reflection surface 13, and a second transmission surface 14, and the first transmission surface 11 is on the object side with respect to the central axis 1. The first reflection surface 12 is disposed on the opposite side of the first transmission surface 11 with the central axis 1 interposed therebetween, and is disposed on the opposite side of the image surface 30 from the first transmission surface 11. Is disposed on the same side as the first reflecting surface 12 with respect to the central axis 1, disposed on the opposite side of the image surface 30 from the first reflecting surface 12, and the second transmitting surface 14 is imaged from the second reflecting surface 13. It arrange | positions at the surface 30 side.

  The light beam 2 incident from a distance enters the transparent medium through the first transmission surface 11, and the image plane is formed on the first reflection surface 12 disposed on the opposite side of the first transmission surface 11 with the central axis 1 interposed therebetween. 30 is reflected to the image plane 30 side by the second reflecting surface 13 which is reflected on the opposite side to the central axis 1 and arranged on the same side as the first reflecting surface 12 with respect to the central axis 1, and passes through the second transmitting surface 14 to be a transparent medium. From the central axis 1 of the image plane 30 through the circular aperture 5 and the rear group 20 that are arranged coaxially with the central axis 1 between the front group 10 and the rear group 20 and constitute a diaphragm. An image is formed at a predetermined position in the radial direction. The first transmitting surface 11, the first reflecting surface 12, and the second reflecting surface 13 of the front group 10 are formed of an extended rotation free-form surface (a part of the toric surface because the high-order term is zero). However, the conic constant is zero. The second transmission surface 14 is formed of a rotationally symmetric aspherical surface having a top on the central axis 1.

  The lens system constituting the rear group 20 includes, in order from the front group 10 side, a cemented lens of a biconcave negative lens L1 and a biconvex positive lens L2, and a cemented lens of a biconvex positive lens L3 and a biconcave negative lens L4. .

  When the central axis 1 is oriented in the vertical direction and the image plane 30 is oriented in the zenith direction, the central light beam 2 incident from a far distance in the horizontal direction is refracted by the first transmission surface 11 of the incident surface and the front group 10. The light beam that enters the transparent medium and is reflected by the first reflecting surface 12 and the second reflecting surface 13 in this order is refracted by the second transmitting surface 14 and exits from the transparent medium of the front group 10 and passes through the opening 5. Then, the light enters the rear group 20 and forms an image at a predetermined position in the radial direction away from the central axis 1 of the image plane 30.

  In the optical system of this embodiment, an aperture (aperture) 5 positioned between the front group 10 and the rear group 20 is projected on the object side, and an entrance pupil 6Y is formed in the vicinity of the first transmission surface 12 in the meridional section. The entrance pupil 6X is formed on the central axis (rotation symmetry axis) 1 in the sagittal section.

In the optical system of this embodiment, light fluxes 2, 3U, 3L incident from a distance through the entrance pupil 6Y (light flux 3U is a light flux incident from a distant sky side, 3L is a light flux incident from a distant ground side). , a section including the center axis 1: (meridional section 9) inside, and imaged on the second reflecting surface 13 near the position 4Y, also the center ray 2 ₀ of the light beam orthogonal to the plane including the center axis 1 An image is formed at a position 4X between the first reflecting surface 12 and the second reflecting surface 13 in the plane (Sagittal section: FIG. 10) including the first reflecting surface 12 and the second reflecting surface 13.

The specification of this Example 3 is
Horizontal field of view 360 °
Vertical angle of view 40 ° (center angle of view 0 ° (horizontal direction))
Entrance pupil diameter 1.60mm
Image size φ 2.37 to φ 6.03 mm
It is.

  In the optical system of Example 3, the first reflecting surface 12 is disposed on the opposite side of the image surface 30 from the first transmitting surface 11, and the second reflecting surface 13 is on the opposite side of the image surface 30 from the first reflecting surface 12. The second transmission surface 14 is disposed closer to the image plane 30 than the second reflection surface 13.

  In the configuration in which the image plane 30 is arranged in parallel with the ground, the optical system according to the third embodiment covers the vertical angle of view across the horizontal direction. Are preferably used.

  FIG. 11 shows the lateral aberration of the entire optical system of this example. FIG. 12 shows the vertical distortion of this embodiment.

  The configuration parameters of Examples 1 to 3 are shown below. In the table below, “ASS” indicates an aspherical surface, and “ERFS” indicates an extended rotation free-form surface. “RE” indicates a reflective surface.

Example 1
Surface number Curvature radius Surface spacing Eccentric refractive index Abbe number Object surface ∞ ∞
1 ∞ (entrance pupil plane) Eccentricity (1)
2 ERFS [1] Eccentricity (2) 1.7042 48.3
3 ERFS [2] (RE) Eccentricity (3) 1.7042 48.3
4 ERFS [3] (RE) Eccentricity (4) 1.7042 48.3
5 ASS [1] Eccentricity (5)
6 ∞ (diaphragm) Eccentricity (6)
7 121.09 Eccentricity (7) 1.7552 27.6
8 4.55 Eccentricity (8) 1.6532 54.6
9 -6.05 Eccentricity (9)
10 7.95 Eccentricity (10) 1.7486 35.6
11 -4.65 Eccentricity (11) 1.7353 28.4
12 -368.42 Eccentricity (12)
Image plane ∞ Eccentricity (13)
ERFS [1]
RY 22.29
θ -7.70
R -15.45
C ₃ -4.1323 × 10 ^-2
C ₄ 6.7161 × 10 ^-3
ERFS [2]
RY -24.08
θ -38.65
R 10.50
C ₃ -8.5996 × 10 ^-4
C ₄ -1.0524 × 10 ^-5
ERFS [3]
RY 8.89
θ -63.99
R -5.33
C ₃ -4.2137 × 10 ^-3
C ₄ 5.5428 × 10 ^-5
ASS [1]
R -9.80
k 0.0000
a 1.0854 × 10 ^-3
Eccentricity (1)
X 0.00 Y 0.00 Z -15.44
α 0.00 β 0.00 γ 0.00
Eccentric (2)
X 0.00 Y 0.01 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (3)
X 0.00 Y -14.07 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (4)
X 0.00 Y 4.02 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (5)
X 0.00 Y -21.50 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (6)
X 0.00 Y -22.70 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (7)
X 0.00 Y -23.76 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (8)
X 0.00 Y -24.76 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (9)
X 0.00 Y -28.76 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (10)
X 0.00 Y -28.86 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (11)
X 0.00 Y -33.86 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (12)
X 0.00 Y -34.86 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (13)
X 0.00 Y -37.28 Z 0.00
α -90.00 β 0.00 γ 0.00.

Example 2
Surface number Curvature radius Surface spacing Eccentric refractive index Abbe number Object surface ∞ ∞
1 ∞ (entrance pupil plane) Eccentricity (1)
2 ERFS [1] Eccentricity (2) 2.0033 28.3
3 ERFS [2] (RE) Eccentricity (3) 2.0033 28.3
4 ERFS [3] (RE) Eccentricity (4) 2.0033 28.3
5 ASS [1] Eccentricity (5)
6 ∞ (diaphragm) Eccentricity (6)
7 -12.64 Eccentricity (7) 1.6204 60.3
8 -6.08 Eccentricity (8)
9 -87.51 Eccentric (9) 1.7412 28.2
10 4.64 Eccentricity (10) 1.7440 44.8
11 -10.21 Eccentricity (11)
12 8.56 Eccentricity (12) 1.7552 27.6
13 -30.49 Eccentricity (13) 1.6204 60.2
14 13.33 Eccentricity (14)
Image plane ∞ Eccentricity (15)
ERFS [1]
RY 8.15
θ 39.39
R -10.16
C ₃ -1.7818 × 10 ^-2
C ₄ -1.3639 × 10 ^-2
ERFS [2]
RY -21.19
θ -1.45
R 9.94
C ₃ 2.5612 × 10 ^-3
C ₄ -1.3159 × 10 ^-4
ERFS [3]
RY 8.56
θ -60.11
R -5.12
C ₃ -3.6883 × 10 ^-3
C ₄ -1.4851 × 10 ^-3
ASS [1]
R-14.64
k 0.0000
a 1.0087 × 10 ^-3
Eccentricity (1)
X 0.00 Y 0.00 Z -10.07
α 0.00 β 0.00 γ 0.00
Eccentric (2)
X 0.00 Y -0.06 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (3)
X 0.00 Y 15.20 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (4)
X 0.00 Y 27.89 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (5)
X 0.00 Y -0.16 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (6)
X 0.00 Y -0.26 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (7)
X 0.00 Y -2.47 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (8)
X 0.00 Y -4.47 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (9)
X 0.00 Y -4.57 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (10)
X 0.00 Y -5.27 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (11)
X 0.00 Y -8.77 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (12)
X 0.00 Y -8.87 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (13)
X 0.00 Y -13.87 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (14)
X 0.00 Y -14.57 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (15)
X 0.00 Y -16.57 Z 0.00
α -90.00 β 0.00 γ 0.00.

Example 3
Surface number Curvature radius Surface spacing Eccentric refractive index Abbe number Object surface ∞ ∞
1 ∞ (entrance pupil plane) Eccentricity (1)
2 ERFS [1] Eccentricity (2) 1.5163 64.1
3 ERFS [2] (RE) Eccentricity (3) 1.5163 64.1
4 ERFS [3] (RE) Eccentricity (4) 1.5163 64.1
5 ASS [1] Eccentricity (5)
6 ∞ (diaphragm) Eccentricity (6)
7 -12.80 Eccentricity (7) 1.7552 27.6
8 3.84 Eccentricity (8) 1.7440 44.8
9 -4.65 Eccentricity (9)
10 6.92 Eccentricity (10) 1.7515 31.5
11 -3.90 Eccentricity (11) 1.7551 27.6
12 7.93 Eccentricity (12)
Image plane ∞ Eccentricity (13)
ERFS [1]
RY 19.23
θ 37.36
R -11.07
C ₃ 0.0000
C ₄ 0.0000
ERFS [2]
RY -31.85
θ -16.14
R 13.05
C ₃ 0.0000
C ₄ 0.0000
ERFS [3]
RY -147.29
θ -74.57
R 7.85
C ₃ 0.0000
C ₄ 0.0000
ASS [1]
R -38.97
k 0.0000
a 5.3621 × 10 ^-3
Eccentricity (1)
X 0.00 Y 0.00 Z -11.09
α 0.00 β 0.00 γ 0.00
Eccentric (2)
X 0.00 Y 0.00 Z -11.07
α 37.36 β 0.00 γ 0.00
Eccentricity (3)
X 0.00 Y 5.93 Z 13.05
α -16.14 β 0.00 γ 0.00
Eccentricity (4)
X 0.00 Y 11.33 Z 7.85
α -74.57 β 0.00 γ 0.00
Eccentricity (5)
X 0.00 Y -21.62 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (6)
X 0.00 Y -22.12 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (7)
X 0.00 Y -22.62 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (8)
X 0.00 Y -23.62 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (9)
X 0.00 Y -26.62 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (10)
X 0.00 Y -26.72 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (11)
X 0.00 Y -30.22 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (12)
X 0.00 Y -31.22 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (13)
X 0.00 Y -34.50 Z 0.00
α -90.00 β 0.00 γ 0.00.

  By the way, in Examples 1-3, the opening 5 is arrange | positioned coaxially with the central axis 1 between the front group 10 and the rear group 20, and this opening 5 is projected back on the object side in the plane containing the central axis 1. Thus, the entrance pupil 6Y in the plane including the central axis 1 is formed in the vicinity of the entrance plane 11, but instead of the opening 5, FIGS. As shown in the cross-sectional view including the central axis 1 of the example, a cylindrical slit or an annular slit 15 may be arranged at the position of the entrance pupil 6Y coaxially with the central axis 1. In that case, the slit 15 itself acts as a front diaphragm to form the entrance pupil 6Y. Further, apart from the opening 5 disposed between the front group 10 and the rear group 20, a flare stop composed of a cylindrical slit or a ring-shaped slit that is rotationally symmetric about the central axis 1 is disposed in the vicinity of the incident surface 11. It is desirable to do. Note that such a flare stop and the slit 15 forming the entrance pupil 6Y may be combined.

  Further, in the optical system of the above embodiment, a Y toric lens is added to the object side of the front group 10 and the Y toric lens is also a lens configured with a rotationally symmetric surface with respect to the Y axis (center axis 1). The toric lens does not have power in the X direction, while it has negative power in the Y direction (such as in the cross section of FIG. 1). It becomes possible to take a large corner. More preferably, the toric lens has a negative meniscus lens shape with a convex surface facing the object side in the YZ section, thereby minimizing the occurrence of image distortion and enabling good aberration correction. It becomes.

  Furthermore, the object side of the front group 10 is not limited to one Y toric lens having a negative meniscus lens shape in cross section, and is composed of two or three meniscus lenses, thereby reducing image distortion. Is possible. In addition to the lens, it is also easy to image or observe an arbitrary direction by reflecting and refracting the light beam with a reflection surface or prism that is rotationally symmetric with respect to the central axis 1.

  Further, in the above embodiment, the reflecting surface and the refracting surface of the front group 10 are formed by rotating line segments of arbitrary shapes around the rotational symmetry axis 1 and do not have a top on the rotational symmetry axis 1. Although it is composed of an extended rotation free-form surface, it can be easily replaced with an arbitrary curved surface.

  In addition, the optical system of the present invention uses an equation that includes an odd-order term in an expression that defines a line segment of an arbitrary shape that forms a rotationally symmetric surface. The pupil aberration is corrected.

  Further, by using the rotationally symmetric transparent medium around the central axis 1 constituting the front group 10 of the present invention as it is, an image having a 360 ° omnidirectional angle of view can be taken or projected. By cutting the cross section including the central axis 1 into half, one third, two thirds, etc., images with an angle of view around the central axis 1 of 180 °, 120 °, 240 °, etc. May be taken or projected.

  The optical system of the present invention has been described above as an imaging or observation optical system that obtains an image having 360 ° omnidirectional (all circumference) angles of view including the zenith with the central axis (rotation symmetry axis) 1 in the vertical direction. The present invention is not limited to the photographing optical system and the observation optical system, but can also be used as a projection optical system that projects an image on a 360 ° omnidirectional (all circumference) angle of view including the zenith with the optical path reversed. The endoscope can also be used as an all-round observation optical system of an in-tube observation apparatus.

  Below, the usage example of the panorama imaging optical system 31 or the panorama projection optical system 32 is demonstrated as an application example of the optical system of this invention. FIG. 17 is a diagram for illustrating an example in which the panoramic photographing optical system 31 according to the present invention is used as the photographing optical system at the distal end of the endoscope. FIG. This is an example in which a panoramic imaging optical system according to the invention is attached and images of 360 ° omnidirectional images are taken and observed. FIG. 17B shows a schematic configuration of the tip. Around the entrance surface 11 of the front group 10 of the panoramic imaging optical system 31 according to the present invention, a flare stop 17 made of a casing or the like having an opening 16 extending in a slit shape in the circumferential direction is arranged so that flare light enters. It is preventing. FIG. 17C shows a panoramic photographing optical system 31 according to the present invention similarly attached to the tip of the soft electronic endoscope 42, and performs image processing on the image photographed on the display device 43 to correct distortion. This is an example of displaying.

  In FIG. 18A, a plurality of panoramic photographing optical systems 31 according to the present invention are attached as photographing optical systems to the corners of the automobile 48 and the top of the pole of the head portion, and the panoramic photographing optical systems 31 are passed through a display device in the vehicle. FIG. 18 is a diagram illustrating an example in which a captured image is subjected to image processing to correct distortion and simultaneously displayed, and FIG. 18B illustrates a schematic configuration of the tip. Around the entrance surface 11 of the front group 10 of the panoramic imaging optical system 31 according to the present invention, a flare stop 17 made of a casing or the like having an opening 16 extending in a slit shape in the circumferential direction is arranged so that flare light enters. It is preventing.

  In FIG. 19, the panorama projection optical system 32 according to the present invention is used as the projection optical system of the projection device 44, a panorama image is displayed on the display element arranged on the image plane, and is arranged in 360 ° through the panorama projection optical system 32. This is an example in which a 360 ° omnidirectional image is projected and displayed on the screen 45.

  In FIG. 20, a photographing device 49 using the panoramic photographing optical system 31 according to the present invention is attached to the outside of a building 47, and a projecting device 44 using the panoramic projection optical system 32 according to the present invention is disposed indoors. It connects so that the imaged image may be sent to the projection device 44 via the electric wire 46. In such an arrangement, a 360 ° omnidirectional outdoor subject O is photographed by the photographing device 49 via the panoramic photographing optical system 31, and the video signal is sent to the projecting device 44 via the electric wire 46 and arranged on the image plane. In this example, the image is displayed on the display element, and the image O ′ of the subject O is projected and displayed on an indoor wall surface or the like through the panorama projection optical system 32.

It is sectional drawing taken along the central axis of the optical system of Example 1 of this invention. It is a top view which shows the optical path in the optical system of Example 1 of this invention. 2 is a transverse aberration diagram for the whole optical system of Example 1. FIG. FIG. 4 is a diagram illustrating distortion in the vertical direction according to the first embodiment. It is sectional drawing taken along the central axis of the optical system of Example 2 of this invention. It is a top view which shows the optical path in the optical system of Example 2 of this invention. FIG. 6 is a transverse aberration diagram for the whole optical system of Example 2. FIG. 6 is a diagram illustrating distortion in the vertical direction according to the second embodiment. It is sectional drawing taken along the central axis of the optical system of Example 3 of this invention. It is a top view which shows the optical path in the optical system of Example 3 of this invention. 5 is a lateral aberration diagram for the whole optical system of Example 3. FIG. FIG. 10 is a diagram illustrating distortion in the vertical direction according to the third embodiment. It is a figure for demonstrating the definition of a meridional section and a sagittal section. 6 is a cross-sectional view including a central axis of a modified example of Embodiment 1. FIG. 6 is a cross-sectional view including a central axis of a modified example of Example 2. FIG. 10 is a cross-sectional view including a central axis of a modified example of Example 3. FIG. It is a figure for showing the example which used the panorama imaging | photography optical system by this invention as an imaging | photography optical system of the endoscope front-end | tip. It is a figure for showing the example which used the panoramic imaging optical system by this invention as an imaging optical system in each corner of a motor vehicle, or the top of the pole of a head part. It is a figure for showing the example using the panorama projection optical system by this invention as a projection optical system of a projector. It is a figure for showing the example which image | photographs an outdoor to-be-photographed object via the panorama imaging | photography optical system by this invention, and is projected and displayed indoors through the panorama projection optical system by this invention.

Explanation of symbols

1 ... Center axis (axis of rotational symmetry)
2... Central luminous flux incident from a distance 2 ₀ ... Central ray (chief ray) of central luminous flux
3U: Light beam incident from the far sky side 3L: Light beam incident from the far ground side 4X ₁ , 4X ₂ , 4X: Intermediate image formation position 4Y ₁ , 4Y ₂ , 4Y in the sagittal section In the meridional section Intermediate image formation position 5 ... aperture (aperture)
6X: Entrance pupil 6X 'in the sagittal section 6 ... Image of the aperture imaged at the first time in the sagittal section 6Y ... Entrance pupil 6Y' in the meridional section 6: Opening imaged at the first time in the meridional section Image 10 ... front group 11 ... incident surface (first transmission surface)
12 ... 1st reflective surface 13 ... 2nd reflective surface 14 ... Ejection surface (2nd transmissive surface)
DESCRIPTION OF SYMBOLS 15 ... Cylindrical slit or ring-shaped slit 16 ... Opening 17 extended in the shape of a slit in the circumferential direction ... Flare stop 20 ... Rear group 30 ... Image plane 31 ... Panoramic imaging optical system 32 ... Panoramic projection optical system 41 ... Inside rigid Endoscope 42 ... Soft electronic endoscope 43 ... Display device 44 ... Projection device 45 ... Screen 46 ... Electric wire 47 ... Building 48 ... Automobile 49 ... Shooting devices L1-L5 ... Lens O ... Subject O '... Video

Claims (12)

An optical system that forms an image having an angle of view of 360 ° on an image plane or projects an image arranged on the image plane on an angle of view of 360 °,
A front group including two reflecting surfaces rotationally symmetric about the central axis, a rear group rotationally symmetric about the central axis and having positive power, and an opening arranged coaxially with the central axis,
The front group has a transparent medium that is rotationally symmetric about a central axis, and the transparent medium has a first transmission surface, a first reflection surface, a second reflection surface, and a second transmission surface;
The first reflecting surface is disposed on the image plane side with respect to the first transmitting surface, the second reflecting surface is disposed on the side opposite to the image surface with respect to the first reflecting surface, and the second transmitting surface is disposed on the first transmitting surface. It is arranged on the image plane side from the surface,
In the case of an imaging optical system, the light beam incident on the front group enters the transparent medium through the first transmission surface, in the order in which the light beam travels. Reflected on the opposite side to the image plane by the first reflecting surface disposed on the opposite side of the first transmitting surface across the axis, and disposed on the same side as the first transmitting surface with respect to the central axis. Reflected on the image plane side by the second reflecting surface, exits from the transparent medium through the second transmitting surface, forms an image at a position deviating from the central axis of the image surface through the rear group, and The entrance pupil position is different in the cross section including the central axis and in the cross section orthogonal to the cross section and including the central ray of the luminous flux ,
The entrance pupil in the cross section perpendicular to the cross section including the central axis is located on the central axis,
When the optical path length from the entrance pupil position in the cross section including the central axis to the opening position is A, and the optical path length from the entrance pupil position in the cross section including the central axis to the first transmission surface of the front group is B,
5 <| A / B | (4)
An optical system characterized by satisfying the following condition . The number of aperture images formed by projecting the aperture in the direction opposite to the incident direction of the light beam is the same in the cross section including the central axis and in the cross section orthogonal to the cross section and including the central ray of the light beam. The optical system according to claim 1, wherein: 3. The optical system according to claim 1, wherein at least one of the reflecting surfaces has a rotationally symmetric shape formed by rotating an arbitrary-shaped line segment having no symmetrical surface around the central axis. Any one of claims 1 to 3, characterized in that it has a rotationally symmetric shape formed by rotation about the center axis of a line segment of any desired shape, further comprising a reflective surface odd order terms of at least one surface Optical system. A flare stop that restricts light rays only in the cross section including the central axis is disposed at an entrance pupil conjugate with the aperture formed on the object side by the front group in the cross section including the central axis. The optical system according to any one of claims 1 to 4 . The rear group includes an optical system of any one of claims 1, characterized in that it consists of a coaxial dioptric system of rotational symmetry 5. The height from the end opposite to the image plane in the central axis direction of the front group to the end on the image plane side is H1, and the height from the end opposite to the image plane to the entrance pupil in the cross section including the central axis Is H2,
1.5 <H1 / H2 <100 (1)
The optical system according to claim 1, wherein the following condition is satisfied. The height from the end opposite to the image plane in the central axis direction of the front group to the end on the image plane side is H1, and the height from the end opposite to the image plane to the entrance pupil in the cross section including the central axis Is H2,
0.5 <H1 / H2 <10 (3)
The optical system according to claim 1, wherein the following condition is satisfied. When the distance between the entrance pupil position and the central axis in the cross section including the central axis is C, and the focal length in the cross section including the central axis of the front group is Ffy,
0.1 <C / | Ffy | (5)
Satisfy conditions the optical system of any one of claims 1 8, characterized in comprising. When the magnification of the aperture with respect to the entrance pupil in the cross section including the central axis is Pβ,
0.05 <| Pβ | <20 (6)
Satisfy conditions the optical system of any one of claims 1 6, characterized in comprising. Instead of or in addition to the opening of the aperture, any of claims 1 to 10, characterized in that it comprises a rotationally symmetric zonal slit opening about the center axis to said first transmitting surface of the front group The optical system according to claim 1. The optical system according to any one of claims 1 to 11 , wherein at least the reflection surface is cut by a cross section including a central axis, and an angle of view around the central axis is configured to be narrower than 360 °.

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