JP4849591B2 - 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). Japanese Patent Application Laid-Open Publication No. 2004-228561 is known that includes a front group that includes a medium and is rotationally symmetric about a central axis, and a rear group that is rotationally symmetric about the central axis and has positive power.
US Patent Application Publication No. 2004/0008423

  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. In addition, since the entrance surface and the second reflection surface, and the first reflection surface and the exit surface are made of the same rotationally symmetric aspheric surface, the aberration is not necessarily corrected well and the resolving power is 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 forms an image having a 360 ° omnidirectional angle of view on an image plane, or projects an image arranged on the image plane onto a 360 ° omnidirectional angle of view. A system,
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;
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 same side as the first transmitting surface with respect to the axis, and disposed on the opposite side to the first transmitting surface across the central axis. The second reflection surface is reflected to the image surface side, passes out of the transparent medium through the second transmission surface disposed on the same side as the second reflection surface with respect to the central axis, and the rear An image is formed at a position deviating from the central axis of the image plane through the group, and the entrance pupil position in the cross section including the central axis is different from that in the cross section orthogonal to the cross section and including the central ray of the luminous flux. Configured as
The entrance pupil of the cross section perpendicular to the cross section including the middle mandrel is located in 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 | (3)
It is characterized by satisfying the following condition .

  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 light rays only in the cross section including the central axis is disposed at the entrance pupil conjugate with the aperture 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.

When the focal length in the cross section including the central axis of the front group is Ffy, and the focal length in the cross section orthogonal to the cross section is Ffx,
Ffx / Ffy <0.95 (1)
It is desirable to satisfy the following conditions .

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 (4)
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 (5)
It is desirable to satisfy the following condition.

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

  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.

  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 rotationally symmetric about the central axis 1 (in the embodiment of FIG. 1, the rear group 20 is an ideal of positive power). It is assumed that a lens is used.)

  The transparent medium of the front group 10 is disposed on the same side as the first transmission surface 11 with respect to the first transmission surface 11 and the central axis 1 on which the light beam 2 from a distance is incident. The first reflecting surface 12 on which the light beam that enters and enters the image surface side is incident is disposed on the opposite side of the first transmitting surface 11 with the central axis 1 interposed therebetween, and the first reflecting surface 12 is on the opposite side of the image surface. The second reflecting surface 13 on which the reflected light beam is incident is disposed on the same side as the second reflecting surface 13 with respect to the central axis 1, and the light beam reflected on the image surface side by the second reflecting surface 13 is incident. It consists of the second transmission surface 14. 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 of FIG. 1, a circular opening 5 constituting a diaphragm 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 an arbitrary line segment 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 curvature of rotation with respect to the central axis 1 in that case And the entrance pupil 6Y in the back-projected meridional cross section is arranged in the vicinity of the first transmission surface 11 of the front group 10 to significantly reduce unnecessary light entering the front group 10. It is possible to cut the flare and reduce flare.

  On the other hand, the sagittal section orthogonal to the central axis 1 is a rotationally symmetric system, so that the light beam also passes rotationally symmetrically, and the light beam having the same image height on the ring always passes on the central axis 1 that is the center of rotation. (FIG. 2B). Therefore, in the sagittal section, the light beam that reaches the image plane 30 on the circumference passes through the central axis 1 and then reaches the image plane 30, and the image of the back-projected aperture of the diaphragm of the sagittal section is obtained. The entrance pupil 6X in the sagittal section is present on the central axis 1.

  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.

  On the other hand, in order to realize the shape like the reflecting surfaces 12 and 13 of the present invention using the rotationally symmetric aspherical surface having the top on the rotationally symmetric axis, a large number of high-order terms are used and a lot of freedom is achieved. It is necessary to give a degree. However, since there are too many degrees of freedom, it is necessary to take a large number of sampling points for the angle of view and the wavelength.

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

  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.

  Thus, in order to make the back projection position of the diaphragm 5 different in the meridional cross section including the central axis 1 and in the sagittal cross section orthogonal to the cross section, in the optical system of the present invention, in the meridional cross section including the central axis 1 ( It is necessary to make the focal lengths of the front group 10 different in the sagittal cross section (XZ direction) orthogonal to the central axis 1 in the YZ direction.

Meridional section of the front group 10 of the optical system of the present invention (Y-Z direction) and the principal ray (center ray) of the light beam 2 incident on the sagittal cross section (X-Z direction) field angle center 2 ₀ parallel to it Dependent rays separated by a very small distance (0.1 mm) are traced, and the focal lengths Ffx, Y-X of the front group 10 in the X-Z direction are determined from the angle formed by the dependent rays and the principal rays when emitted from the front group 10. The focal length Ffy in the Z direction is obtained. In order to arrange the entrance pupil 6Y in the meridional section near the first transmission surface 11 of the front group 10,
Ffx / Ffy <0.95 (1)
1.05 <Ffx / Ffy (2)
It is preferable to satisfy any one of the following conditions.

  When the upper limit of 0.95 in conditional expression (1) is exceeded or the lower limit of 1.05 in conditional expression (2) is exceeded, the focal lengths in the meridional section and sagittal section become substantially equal, and the back projection of the diaphragm 5 The positions cannot be greatly varied, the size of the first transmission surface 11 in the direction along the central axis is increased, and the optical system is weak against flare light.

More preferably,
Ffx / Ffy <0.90 (1-1)
1.1 <Ffx / Ffy (2-1)
It is more preferable to satisfy any one of the following conditions.

  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 | (3)
It is important to satisfy the following conditions.

  If the lower limit of 5 of the conditional expression (3) 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 | (3-1)
It is preferable to satisfy the following conditions.

Further, 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 focal length Ffy of the front group 10 in the YZ direction (meridional section). The ratio is
0.1 <C / Ffy (4)
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.

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 (5)
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 (5), 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 (5-1)
It is preferable to satisfy the following conditions.

  Fx, Fy, Fx / Fy, Ffx, Ffy, Ffx / Ffy, A, B, | A / B |, C, C / Ffy, and Pβ in Examples 1 to 3 described later are as follows. Where Fx is the focal length of the entire optical system in the YZ direction, and Fy is the focal length of the entire optical system in the YZ direction.

Example 1 Example 2 Example 3
Fx -2.050 -2.094 -2.200
Fy -2.289 -3.080 -2.496
Fx / Fy 0.895 0.680 0.881
Ffx 11.455 3.712 4.421
Ffy 13.333 5.214 4.748
Ffx / Ffy 0.859 0.712 0.931
A 112.254 126.926 138.398
B -0.028 -0.007 -0.036
｜ A / B ｜ 3988.511 17058.582 3826.200
C 21.861 26.893 26.043
C / Ffy 1.640 5.158 5.485
Pβ 1.724 1.619 2.020
.

  Examples 1 to 3 of the optical system according to the present invention will be described below. 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 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. In the case of this embodiment, the rear group 20 is composed of an ideal lens having a positive power.

  The transparent medium of the front group 10 is disposed on the same side as the first transmission surface 11 with respect to the central axis 1 and the first transmission surface 11 on which the light beam 2 from a distance is incident. Is disposed on the opposite side of the first transmission surface 11 across the central axis 1, and is opposite to the image surface at the first reflection surface 12. The second reflecting surface 13 on which the reflected light beam is incident and the light beam that is disposed on the same side as the second reflecting surface 13 with respect to the central axis 1 and is reflected to the image surface side by the second reflecting surface 13 Are incident on the second transmission surface 14, and any of the transmission surfaces 11, 14 and the reflection surfaces 12, 13 are formed of an extended rotation free-form surface. However, the conic constant is zero.

  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 10 ° 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 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). In the cross section including the central axis 1 (meridional cross section: FIG. 1), an image is formed once at a position 4Y between the first reflective surface 12 and the second reflective surface 13 near the second reflective surface 13, and the center. perpendicular to the plane including the axis 1 plane including the center ray 2 ₀ of the light beam: in (sagittal section FIG. 2), and 1 Kaiyuizo a position 4X between the second reflecting surface and the second transmitting surface 14 Yes.

The specification of this Example 1 is
Horizontal field of view 360 °
Vertical angle of view 40 ° (center angle of view 10 ° (elevation angle))
Entrance pupil diameter 1.22mm
Image size φ2.49 to φ5.47mm
It is.

  In the optical system of Example 1, the first reflecting surface 12 and the second transmitting surface 14 are disposed on the image surface 30 side of the first transmitting surface 11, and the second reflecting surface 13 is disposed on the opposite side of the image surface 30. .

  In the configuration in which the image plane 30 is arranged in parallel with the ground, the optical system of Example 1 is preferably used when mainly imaging 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, and the curve connected with ▪ indicates the image height (from the central axis 1) on the image plane 30 with respect to the vertical incidence 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), 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 three lenses including five lenses L1 to L5.

  The transparent medium of the front group 10 is disposed on the same side as the first transmission surface 11 with respect to the central axis 1 and the first transmission surface 11 on which the light beam 2 from a distance is incident. Is disposed on the opposite side of the first transmission surface 11 across the central axis 1, and is opposite to the image surface at the first reflection surface 12. The second reflecting surface 13 on which the reflected light beam is incident and the light beam that is disposed on the same side as the second reflecting surface 13 with respect to the central axis 1 and is reflected to the image surface side by the second reflecting surface 13 Are incident on the second transmission surface 14, and any of the transmission surfaces 11, 14 and the reflection surfaces 12, 13 are formed of an extended rotation free-form surface. However, the conic constant is zero.

  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 negative meniscus lens L2 having a convex surface facing the front group 10, and a biconvex positive lens. It consists of a cemented lens of L3, a biconvex positive lens L4, and a cemented lens of a negative meniscus lens L5 having a concave surface facing the front group 10 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 20 ° 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 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). In the cross section including the central axis 1 (meridional cross section: FIG. 5), an image is formed once at a position 4Y between the second reflecting surface 13 and the second transmitting surface 14, and is orthogonal to the plane including the central axis 1. perilla of the light beam center light ray 2 plane containing _0: in (sagittal section 6) inside, and 1 Kaiyuizo a position 4X between the second reflecting surface and the second transmitting surface 14.

The specification of Example 2 is
Horizontal field of view 360 °
Vertical angle of view 40 ° (center angle of view 20 ° (elevation angle))
Entrance pupil diameter 2.00mm
Image size φ6.01 to φ2.08mm
It is.

  In the optical system of Example 2, the first reflecting surface 12 is disposed on the image surface 30 side of the first transmitting surface 11, and the second reflecting surface 13 is disposed on the opposite side of the image surface 30.

  In the configuration in which the image plane 30 is arranged in parallel with the ground, the optical system of Example 2 is preferably used when mainly imaging the sky side.

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

  FIG. 8 is a sectional view taken along the central axis (rotation symmetry axis) 1 of the optical system of Example 3, and FIG. 9 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), 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 three lenses including five lenses L1 to L5.

  The transparent medium of the front group 10 is disposed on the same side as the first transmission surface 11 with respect to the central axis 1 and the first transmission surface 11 on which the light beam 2 from a distance is incident. Is disposed on the opposite side of the first transmission surface 11 across the central axis 1, and is opposite to the image surface at the first reflection surface 12. The second reflecting surface 13 on which the reflected light beam is incident and the light beam that is disposed on the same side as the second reflecting surface 13 with respect to the central axis 1 and is reflected to the image surface side by the second reflecting surface 13 Are incident on the second transmission surface 14, and any of the transmission surfaces 11, 14 and the reflection surfaces 12, 13 are formed of an extended rotation free-form surface. However, the conic constant is zero.

  The lens system constituting the rear group 20 includes, in order from the front group 10 side, a biconvex positive lens L1, a cemented lens of a negative meniscus lens L2 having a convex surface facing the front group 10 and a biconvex positive lens L3, and a biconvex lens. It consists of a positive lens L4 and a cemented lens of a negative meniscus lens L5 having a concave surface facing the front group 10 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 25 ° 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 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). In the cross section including the central axis 1 (meridional cross section: FIG. 5), an image is formed once at a position 4Y between the second reflecting surface 13 and the second transmitting surface 14, and is orthogonal to the plane including the central axis 1. perilla of the light beam center light ray 2 plane containing _0: in (sagittal section 6) inside, and 1 Kaiyuizo a position 4X between the second reflecting surface and the second transmitting surface 14.

The specification of this Example 3 is
Horizontal field of view 360 °
Vertical angle of view 50 ° (center angle of view 25 ° (elevation angle))
Entrance pupil diameter 2.40mm
Image size φ5.98 to φ1.90 mm
It is.

  In the optical system of Example 2, the first reflecting surface 12 and the second transmitting surface 14 are disposed on the image surface 30 side of the first transmitting surface 11, and the second reflecting surface 13 is disposed on the opposite side of the image surface 30. .

  In the configuration in which the image plane 30 is arranged in parallel with the ground, the optical system of Example 3 is preferably used when mainly imaging the sky side.

  FIG. 11 shows the lateral aberration of the entire optical system of this example. FIG. 12 shows the vertical distortion of this embodiment. In this embodiment, the vertical distortion is relatively well corrected.

  The configuration parameters of Examples 1 to 3 are shown below. In the table below, “ERFS” indicates an extended rotation free-form surface. “IDL” indicates an ideal lens, and “RE” indicates a reflecting 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) 1.7440 44.8
3 ERFS [2] (RE) Eccentricity (3) 1.7440 44.8
4 ERFS [3] (RE) Eccentricity (4) 1.7440 44.8
5 ERFS [4] Eccentricity (5)
6 ∞ (diaphragm) Eccentricity (6)
7 IDL eccentricity (7)
Image plane ∞ Eccentricity (8)
ERFS [1]
RY 20.63
θ -51.33
R -21.89
C ₃ -4.0940 × 10 ^-2
C ₄ 9.8180 × 10 ^-3
ERFS [2]
RY -107.74
θ -95.05
R -19.96
C ₃ -1.4187 × 10 ^-3
C ₄ 8.3504 × 10 ^-5
ERFS [3]
RY 98.43
θ -131.21
R 13.88
C ₃ 3.4955 × 10 ^-3
C ₄ -1.1113 × 10 ^-4
ERFS [4]
RY 19.42
θ -80.46
R 11.30
C ₃ -2.6507 × 10 ^-2
C ₄ -3.4125 × 10 ^-4
Eccentricity (1)
X 0.00 Y 0.00 Z -21.86
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 -1.07 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (4)
X 0.00 Y 10.61 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (5)
X 0.00 Y-2.14 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (6)
X 0.00 Y -22.29 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (7)
X 0.00 Y -25.79 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (8)
X 0.00 Y -29.88 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) 1.6204 60.3
3 ERFS [2] (RE) Eccentricity (3) 1.6204 60.3
4 ERFS [3] (RE) Eccentricity (4) 1.6204 60.3
5 ERFS [4] Eccentricity (5)
6 ∞ (diaphragm) Eccentricity (6)
7 -94.51 Eccentricity (7) 1.6382 57.0
8 -6.85 Eccentric (8)
9 9.49 Eccentricity (9) 1.7552 27.6
10 3.90 Eccentricity (10) 1.6 204 60.3
11 -21.13 Eccentricity (11)
12 8.11 Eccentricity (12) 1.6 204 60.3
13 -3.96 Eccentricity (13) 1.6 130 37.1
14 -11.53 Eccentricity (14)
Image plane ∞ Eccentricity (15)
ERFS [1]
RY 19.40
θ 8.31
R -26.90
C ₃ -3.3542 × 10 ^-3
C ₄ 4.2315 × 10 ^-4
ERFS [2]
RY 725.73
θ -79.61
R-23.09
C ₃ 4.2947 × 10 ^-4
C ₄ -2.2746 × 10 ^-7
ERFS [3]
RY 37.16
θ -136.69
R 16.16
C ₃ -3.6027 × 10 ^-4
C ₄ 2.1106 × 10 ^-5
ERFS [4]
RY 3.40
θ -138.93
R 2.51
C ₃ 5.7168 × 10 ^-3
C ₄ -2.3772 × 10 ^-3
Eccentricity (1)
X 0.00 Y 0.00 Z -26.89
α 0.00 β 0.00 γ 0.00
Eccentric (2)
X 0.00 Y 0.00 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (3)
X 0.00 Y -0.58 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (4)
X 0.00 Y 21.60 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (5)
X 0.00 Y 0.47 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (6)
X 0.00 Y -5.73 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (7)
X 0.00 Y -6.23 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (8)
X 0.00 Y -8.06 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (9)
X 0.00 Y -8.16 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (10)
X 0.00 Y -9.16 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (11)
X 0.00 Y -12.66 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (12)
X 0.00 Y -12.76 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (13)
X 0.00 Y -17.26 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (14)
X 0.00 Y -18.26 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (15)
X 0.00 Y -20.26 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) 1.7094 47.8
3 ERFS [2] (RE) Eccentricity (3) 1.7094 47.8
4 ERFS [3] (RE) Eccentricity (4) 1.7094 47.8
5 ERFS [4] Eccentricity (5)
6 ∞ (diaphragm) Eccentricity (6)
7 20.06 Eccentricity (7) 1.7440 44.8
8 -9.04 Eccentricity (8)
9 12.24 Eccentricity (9) 1.7552 27.6
10 3.52 Eccentricity (10) 1.6 204 60.3
11 131.49 Eccentricity (11)
12-6.88 Eccentricity (12) 1.6204 60.3
13 -3.96 Eccentricity (13) 1.6417 34.3
14 -8.70 Eccentric (14)
15 ∞ Eccentricity (15)
Image surface ERFS [1]
RY 17.87
θ -12.58
R -26.08
C ₃ 3.3414 × 10 ^-3
C ₄ 2.4862 × 10 ^-3
ERFS [2]
RY 303.04
θ -86.46
R-23.25
C ₃ 2.3982 × 10 ^-4
C ₄ 3.2943 × 10 ^-5
ERFS [3]
RY 40.44
θ -139.08
R 18.30
C ₃ 3.2024 × 10 ^-4
C ₄ 2.0089 × 10 ^-5
ERFS [4]
RY 4.40
θ -141.26
R 3.02
C ₃ 5.1460 × 10 ^-2
C ₄ -4.1756 × 10 ^-4
Eccentricity (1)
X 0.00 Y 0.00 Z -26.04
α 0.00 β 0.00 γ 0.00
Eccentric (2)
X 0.00 Y 0.02 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (3)
X 0.00 Y -1.00 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (4)
X 0.00 Y 20.05 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (5)
X 0.00 Y -1.74 Z 0.00
α 0.00 β 0.00 γ 0.00
Eccentricity (6)
X 0.00 Y -9.04 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (7)
X 0.00 Y -9.14 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (8)
X 0.00 Y -12.13 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (9)
X 0.00 Y -12.23 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentricity (10)
X 0.00 Y -12.63 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (11)
X 0.00 Y -15.63 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (12)
X 0.00 Y -15.73 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (13)
X 0.00 Y -20.23 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (14)
X 0.00 Y -20.93 Z 0.00
α -90.00 β 0.00 γ 0.00
Eccentric (15)
X 0.00 Y -22.93 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: Intermediate image forming position 4Y in the sagittal section ... Intermediate image forming position 5 in the meridional section: Aperture (stop)
6X: Entrance pupil 6Y in the sagittal section 6: Entrance pupil 10 in the meridional section 10: Front group 11: Entrance plane (first transmission plane)
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 (10)

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;
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 same side as the first transmitting surface with respect to the axis, and disposed on the opposite side to the first transmitting surface across the central axis. The second reflection surface is reflected to the image surface side, passes out of the transparent medium through the second transmission surface disposed on the same side as the second reflection surface with respect to the central axis, and the rear An image is formed at a position deviating from the central axis of the image plane through the group, and the entrance pupil position in the cross section including the central axis is different from that in the cross section orthogonal to the cross section and including the central ray of the luminous flux. Configured as
The entrance pupil of the cross section perpendicular to the cross section including the middle mandrel is located in 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 | (3)
An optical system characterized by satisfying the following condition .   2. The optical system according to claim 1, wherein at least one reflecting surface has a rotationally symmetric shape formed by rotating an arbitrary-shaped line segment having no symmetrical surface around the central axis.   3. The optical system according to claim 1, wherein at least one reflecting surface has a rotationally symmetric shape formed by rotating an arbitrary-shaped line segment including an odd-order term around a central axis. 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 3.   The optical system according to any one of claims 1 to 4, wherein the rear group includes a rotationally symmetric coaxial refractive optical system. When the focal length in the cross section including the central axis of the front group is Ffy, and the focal length in the cross section orthogonal to the cross section is Ffx,
Ffx / Ffy <0.95 (1)
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 (4)
The optical system according to claim 1, wherein the following condition is satisfied. 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 (5)
Optical system of any one of claims 1 to 7, characterized in satisfying be. Instead of or in addition to the opening of the aperture, any of claims 1 to 8, 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 9 , wherein at least the reflection surface is cut along a cross section including a central axis, and an angle of view around the central axis is narrower than 360 °.

Images