WO2009041288A1

WO2009041288A1 - Optical system and endoscope using same

Info

Publication number: WO2009041288A1
Application number: PCT/JP2008/066501
Authority: WO
Inventors: Takayoshi Togino
Original assignee: Olympus Corp.
Priority date: 2007-09-27
Filing date: 2008-09-08
Publication date: 2009-04-02

Abstract

An optical system comprises a front group (Gf) including at least one reflecting surface, a back group (Gb), and an opening (S) disposed between the front group (Gf) and the back group (Gb). At least one surface of a back group first reflecting surface (22) and a back group second reflecting surface (23) is formed by a continuous curved surface on a central axis. Light flux which enters a back group transparent medium (Lb) forms an approximately Z-shaped first optical path (A) by, in the order of forward ray tracing, passing through an opening (S), entering the back group transparent medium (Lb) via a back group first transmitting surface (21), being reflected to the side opposite to an image surface (5) by the back group first reflecting surface (22), being reflected to the image surface (5) side by the back group second reflecting surface (23), and going out from the back group transparent medium (Lb) to the image surface (5) side via a back group second transparent surface (24). The first optical path (A) at least between the back group first reflecting surface (22) and the back group second reflecting surface (23) is formed on only one side with respect to the central axis (2), and an image is formed in an annular shape on the image surface (5) without formation of an intermediate image in the first optical path (A).

Description

Specification

Optical system and endoscope using the same

[0 0 0 1]

The present invention relates to an optical system and an endoscope using the same, and more particularly to an imaging optical system or a projection optical system having a function of forming an image around a rotationally symmetric axis as an annular image on an image sensor. It is. Background art

[0 0 0 2]

Conventionally, there have been optical systems that combine two spherical surfaces or parabolic mirrors.

[Patent Document 1]

Japanese Patent No. 3 3 8 2 6 8 3

[Patent Document 2]

Japanese Patent No. 3 2 1 2 7 8 4

[Patent Document 3]

Japanese Patent Publication No. 6 2-5 5 8 4 2 Disclosure of Invention

[0 0 0 3]

However, none of the optical systems described in any of the patent documents can obtain a high-angle image with a small configuration.

[0 0 0 4]

The present invention has been made in view of such a situation of the prior art, and the purpose thereof is to enable a wide observation angle of view to be imaged on an image sensor with a simple configuration, and to achieve a compact and inexpensive optical. A system and an endoscope using the system are provided. [0 0 0 5]

The optical system of the present invention that achieves the above object has a front group including at least one reflecting surface, a rear group, and an aperture disposed between the front group and the rear group, and a central axis. In the optical system that is rotationally symmetric about the central axis in a cross section including the rear group, the rear group is disposed on the image plane side of the aperture, and has a rear group transparent medium having a refractive index greater than 1. The group transparent medium is disposed on the image plane side of the rear group first transmission surface disposed on the central axis in the vicinity of the opening, and after the concave surface is directed to the image plane side from the rear group first transmission surface. A first group reflecting surface, a rear group second reflecting surface disposed on the opposite side of the image surface from the rear group first reflecting surface, and having a concave surface directed to the image surface side, and an image surface from the second group second reflecting surface. A rear group second transmission surface disposed on the side, and at least one of the rear group first reflection surface and the rear group second reflection surface is continuous on a central axis. The light beam incident on the rear group transparent medium passes through the opening in the order of forward ray tracing, enters the rear group transparent medium through the rear group first transmission surface, and the rear group. Reflected on the side opposite to the image plane by the first group reflecting surface, reflected by the second group second reflecting surface toward the image plane side, passed through the second group transmitting surface on the rear group, and exposed to the image plane side from the rear group transparent medium. A substantially Z-shaped first optical path that goes out, and at least a portion of the first optical path between the rear group first reflecting surface and the rear group second reflecting surface is configured on one side with respect to the central axis. An intermediate image is not formed in the first optical path, but is formed in an annular shape on the image plane.

[0 0 0 6]

In addition, the first reflecting surface of the rear group is a spherical surface.

[0 0 0 7]

The rear group first reflecting surface is configured to reflect by a total reflection action and a reflective coating, and the reflective coating is applied only to the vicinity of the central axis of the rear group first reflecting surface. It is characterized by being.

[0 0 0 8]

Further, the rear group first transmission surface and the rear group second reflection surface are formed of the rear group transparent medium. It is arranged on the object side of the body.

[0 0 0 9]

Further, the rear group first transmission surface and the rear group second reflection surface have the same shape and shape.

[0 0 1 0]

Further, the rear group first reflecting surface and the rear group second transmitting surface are arranged on the image plane side of the rear group transparent medium.

[0 0 1 1]

Further, the rear group first reflecting surface and the rear group second transmitting surface have the same shape at the same position.

[0 0 1 2]

Further, the front group has a front group transparent medium having a refractive index rotationally symmetric about a central axis greater than 1, the front group transparent medium comprising a front group first transmission surface, and the front group first transmission. A front group first reflecting surface disposed on the image surface side from the surface, a front group second reflecting surface disposed on the side opposite to the image surface from the front group first reflecting surface, and the front group second reflecting surface A front group second transmission surface disposed on the image plane side, and a light beam incident on the front group transmission medium passes through the front group first transmission surface in the order of forward ray tracing. After entering the transparent medium and intersecting the central axis, it is reflected to the opposite side of the image surface by the front group first reflecting surface, and to the image surface side by the front group second reflecting surface without intersecting the central axis. An optical path which is reflected and goes out from the front group transparent medium to the image plane side through the front group second transmission surface is formed.

[0 0 1 3]

Further, the front group has a front group transparent medium having a refractive index rotationally symmetric about a central axis greater than 1, the front group transparent medium comprising a front group first transmission surface, and the front group first transmission. A front group first reflecting surface disposed on the image surface side from the surface, a front group second reflecting surface disposed on the side opposite to the image surface from the front group first reflecting surface, and the front group second reflecting surface A front group second transmission surface disposed on the image plane side, and a light beam incident on the front group transmission medium passes through the front group first transmission surface in the order of forward ray tracing. After entering the transparent medium in the front group and intersecting the central axis, the light is reflected to the opposite side of the image surface by the first reflective surface of the front group, crosses the central axis again, and then reflected by the second reflective surface of the front group. An optical path is formed which is reflected to the image plane side and goes out to the image plane side from the front group transparent medium through the front group second transmission surface.

[0 0 1 4]

Further, the front group has a front group transparent medium having a refractive index rotationally symmetric about a central axis greater than 1, the front group transparent medium comprising a front group first transmission surface, and the front group first transmission. A front group first reflecting surface disposed on the opposite side of the image surface from the surface; and a front group second transmitting surface disposed on the image surface side from the front group first reflecting surface; and the front group transparent The light beam incident on the medium enters the front group transparent medium through the front group first transmission surface in the order of forward ray tracing, intersects the central axis, and then moves toward the image plane side by the front group first reflection surface. An optical path which is reflected and goes out from the front group transparent medium to the image plane side through the front group second transmission surface is formed.

[0 0 1 5]

When the maximum image height is I max and the outer diameter of the rear group is D,

0.5 <D / (2 X 1 max) <1 0 · · · · (1) The condition is satisfied.

[0 0 1 6]

When the maximum image height is I max and the distance from the aperture to the image plane is L,

0.5 <L / (2 X 1 max) <1 0 ··· (2) The condition is satisfied.

[0 0 1 7]

In addition, when the curvature of the first reflecting surface of the rear group is R 1 and the curvature of the second reflecting surface of the rear group is R 2,

0.2 <R 1 / R 2 <5--· (3) The following condition is satisfied.

[0 0 1 8] Furthermore, the present invention for achieving the above object is an endoscope using the optical system.

[0 0 1 9]

The optical system of the present invention that achieves the above object has a front group including at least one reflecting surface, a rear group, and an aperture disposed between the front group and the rear group, and a central axis. In the optical system that is rotationally symmetric about the central axis in a cross section including the rear group, the rear group is disposed on the image plane side of the aperture, and has a rear group transparent medium having a refractive index greater than 1. The group transparent medium is disposed on the image plane side of the rear group first transmission surface disposed on the central axis in the vicinity of the opening, and after the concave surface is directed to the image plane side from the rear group first transmission surface. A first group reflecting surface, a rear group second reflecting surface disposed on the opposite side of the image surface from the rear group first reflecting surface, and having a concave surface directed to the image surface side, and an image surface from the second group second reflecting surface. A rear group second transmission surface disposed on the side, and a light beam incident on the rear group transparent medium passes through the aperture in the order of forward ray tracing, and It enters the rear group transparent medium through the first transmission surface, is reflected by the rear group first reflection surface to the side opposite to the image plane, is reflected by the rear group second reflection surface to the image plane side, and the rear group A substantially Z-shaped first optical path exiting from the rear group transparent medium to the image plane side through the second transmission surface is configured, and at least the rear group first reflection surface and the rear group second of the first optical path. The space between the reflection surfaces is formed only on one side with respect to the central axis, and an intermediate image is not formed in the first optical path, and an object point around the central axis is positioned near the central axis in the vicinity of the opening. Crosses once and forms an image on the opposite side as a whole, forming an annular image on the image surface as a whole, and at least one of the rear group reflecting surfaces is a discontinuous rotationally symmetric surface on the central axis It is composed of

[0 0 2 0]

In addition, at least one of the rear group reflecting surfaces is formed of an extended rotation free-form surface formed by rotating a line segment having a discontinuous shape on the central axis around the central axis. It is characterized by that.

[0 0 2 1] Further, at least one of the reflecting surfaces of the rear group is constituted by an extended rotation free curved surface formed by rotating an arbitrary shape line segment including an odd-order term around the central axis. Features.

[0 0 2 2]

[0 0 2 3]

In addition, the rear group first transmission surface and the rear group second reflection surface are arranged on the object side of the transparent medium.

[0 0 2 4]

Further, the rear group first transmitting surface and the rear group second reflecting surface have the same shape at the same position.

[0 0 2 5]

Further, the rear group first reflecting surface and the rear group second transmitting surface are arranged on an image surface side of the transparent medium.

[0 0 2 6]

[0 0 2 7]

The front group includes a front group transparent medium having a rotationally symmetric refractive index greater than 1 around a central axis, the front group transparent medium including a front group first transmission surface, and the front group first transmission. A front group first reflecting surface disposed on the image surface side from the surface, a front group second reflecting surface disposed on the side opposite to the image surface from the front group first reflecting surface, and the front group second reflecting surface A front group second transmission surface disposed on the image plane side, and a light beam incident on the front group transmission medium passes through the front group first transmission surface in the order of forward ray tracing. After entering the transparent medium and intersecting the central axis, the front group first reflecting surface is reflected to the opposite side of the image plane, and without intersecting the central axis, the front group first An optical path is formed which is reflected by the two reflecting surfaces toward the image surface side and exits from the front group transparent medium to the image surface side through the front group second transmitting surface.

[0 0 2 8]

The front group includes a front group transparent medium having a rotationally symmetric refractive index greater than 1 around a central axis, the front group transparent medium including a front group first transmission surface, and the front group first transmission. A front group first reflecting surface disposed on the image surface side from the surface, a front group second reflecting surface disposed on the side opposite to the image surface from the front group first reflecting surface, and the front group second reflecting surface A front group second transmission surface disposed on the image plane side, and a light beam incident on the front group transmission medium passes through the front group first transmission surface in the order of forward ray tracing. After entering the transparent medium, intersecting the central axis, reflected by the front first reflecting surface on the opposite side of the image plane, intersecting the central axis again, and then reflected by the front second reflecting surface on the image side. An optical path is formed which is reflected and goes out from the front group transparent medium to the image plane side through the front group second transmission surface.

[0 0 2 9]

The front group includes a front group transparent medium having a rotationally symmetric refractive index greater than 1 around a central axis, the front group transparent medium including a front group first transmission surface, and the front group first transmission. A front group first reflecting surface disposed on the opposite side of the image surface from the surface; and a front group second transmitting surface disposed on the image surface side from the front group first reflecting surface; and the front group transparent The light beam incident on the medium enters the front group transparent medium through the front group first transmission surface in the order of forward ray tracing, intersects the central axis, and then moves toward the image plane side by the front group first reflection surface. An optical path which is reflected and goes out from the front group transparent medium to the image plane side through the front group second transmission surface is formed.

[0 0 3 0]

0.5 <D / (2 X 1 max) <1 0 ··· (1) is satisfied.

[0 0 3 1]

The maximum image height is I max and the distance from the aperture to the image plane is L. When

0.5 <L / (2 X 1 max) <1 0 ··· (2) The condition is satisfied.

[0 0 3 2]>

When the curvature of the first reflecting surface is R l and the curvature of the second reflecting surface is R 2

0.2 <R 1 / R 2 <5 * · · (3) The condition is satisfied.

[0 0 3 3]

0.5 <R 1 R 2 <2 · * · (3) 'is satisfied.

[0 0 3 4]

Furthermore, the present invention for achieving the above object is an endoscope using the optical system.

[0 0 3 5]

In the optical system of the present invention described above, a compact optical system with a high resolution and a well-corrected aberration that is capable of observing a wide angle of view or projecting an image with a wide angle of view with a simple configuration. Can do. Brief Description of Drawings

[0 0 3 6]

[Figure 1 ]

It is a figure for demonstrating the coordinate system of Example 1 of the optical system of this invention.

[Figure 2 ]

It is a figure which shows the principle of an extended rotation free-form surface.

[Figure 3] FIG. 2 is a cross-sectional view taken along the central axis of the optical system according to Example 1 of the present invention.

[Figure 4]

2 is a transverse aberration diagram for the whole optical system of Example 1. FIG.

[Figure 5]

It is sectional drawing taken along the central axis of the optical system of Example 2 of this invention.

[Figure 6]

6 is a transverse aberration diagram for the whole optical system of Example 2. FIG.

[Fig. 7]

It is sectional drawing taken along the central axis of the optical system of Example 3 of this invention.

[Figure 8]

6 is a transverse aberration diagram for the whole optical system of Example 3. FIG.

[Figure 9]

It is sectional drawing taken along the central axis of the optical system of Example 4 of this invention.

[Figure 1 0]

6 is a transverse aberration diagram for the whole optical system of Example 4. FIG.

[Figure 1 1]

It is sectional drawing taken along the central axis of the optical system of Example 5 of this invention.

[Fig. 1 2]

10 is a transverse aberration diagram for the whole optical system of Example 5. FIG.

[Fig. 1 3]

It is a figure for demonstrating the coordinate system of the optical system of Example 6 of this invention.

[Figure 1 4]

It is sectional drawing taken along the central axis of the optical system of Example 6 of this invention.

[Figure 15]

10 is a transverse aberration diagram for the whole optical system of Example 6. FIG.

[Figure 1 6]

It is sectional drawing taken along the central axis of the optical system of Example 7 of this invention.

[Figure 1 7] 10 is a transverse aberration diagram for the whole optical system of Example 7. FIG.

[Figure 1 8]

It is sectional drawing taken along the central axis of the optical system of Example 8 of this invention.

[Figure 1 9]

10 is a transverse aberration diagram for the whole optical system of Example 8. FIG.

[Figure 2 0]

It is sectional drawing taken along the central axis of the optical system of Example 9 of this invention.

[Figure 2 1]

10 is a transverse aberration diagram for the whole optical system of Example 9. FIG.

[Figure 2 2]

FIG. 6 is a cross-sectional view taken along the central axis of the optical system according to Example 10 of the present invention.

[Figure 2 3]

2 is a transverse aberration diagram for the whole optical system of Example 10. FIG.

[Figure 2 4]

It is a figure which shows the example of arrangement | positioning of the image of the optical system of this invention, and an image pick-up element.

[Figure 2 5]

2 shows an example in which the optical system of the present invention is used as a photographing optical system at the tip of an endoscope.

[Figure 2 6]

FIG. 3 is a diagram showing an example in which the optical system of Example 1 of the present invention is used as a photographing optical system for a capsule endoscope.

[Figure 2 7]

FIG. 10 is a diagram showing an example in which the optical system of Example 6 of the present invention is used as a photographing optical system for a capsule endoscope.

[Figure 2 8]

FIG. 3 is a diagram showing an example in which the optical system of the present invention is used as an imaging optical system for an automobile.

[Figure 2 9] It is a figure which shows the example which used the optical system of this invention as the projection optical system of a projection apparatus.

[Figure 3 0]

FIG. 3 is a diagram showing an example in which the optical system of the present invention is used as a photographing optical system for photographing an outdoor subject.

BEST MODE FOR CARRYING OUT THE INVENTION

[0 0 3 7]

The optical system of the present invention will be described below based on examples.

[0 0 3 8]

FIG. 3 is a cross-sectional view taken along the central axis (rotation symmetry axis) 2 of the optical system 1 of Example 1 described later. Although the following description will be described as an imaging optical system, it can also be used as a projection optical system with the optical path reversed.

[0 0 3 9]

An optical system 1 according to the present invention includes a front group G, an aperture S, and a rear group G b that are rotationally symmetric with respect to a central axis 2 and include at least one reflecting surface. An intermediate image is placed in the optical path. An optical system 1 that forms or projects an image without forming it. The parallel flat plate near the image plane 5 is the cover glass C b 2 of the image sensor.

[0 0 4 0]

The optical system 1 of Example 1 has a front group G f including at least one reflecting surface, a rear group G b, and an aperture S disposed between the front group G f and the rear group G b, In the optical system 1 that is rotationally symmetric around the central axis 2 in the cross section including the central axis 2, the rear group G b is arranged on the image plane 5 side of the aperture S, and the rear group is transparent. The rear group 1 transparent medium Lb as the medium, and the rear group 1 transparent medium Lb is disposed on the central axis 2 near the opening S as the rear group first transmission surface. 2 1 and rear 1st group 1st transmission surface 2 1 rear surface 1st reflection surface 2 2 as rear group 1st reflection surface which is arranged on the image plane side from 1 and has a concave surface facing the image surface side Rear 1st group 2nd reflective surface 2 3 and rear 1st group 2nd reflective surface are arranged on the opposite side of the image surface from 1st group 1st reflective surface 2 2 and the concave surface is directed to the image surface side. Rear group 2 second transmission surface 2 4 as rear group second transmission surface arranged on the image plane side with respect to reflection surface 2 3, and rear group 1 first transmission surface 2 1, rear group 1 1 Reflecting surface 2 2, Rear 1st group 2nd reflecting surface 2 3 and Rear 1st group 2nd transmitting surface 2 4 are composed of spherical surfaces, and the luminous flux incident on the rear 1st group transparent medium Lb is in the order of forward ray tracing. Passes through the aperture S, passes through the rear group 1 first transmission surface 2 1 and enters the rear group 1 transparent medium L b, and is reflected to the opposite side of the image plane 5 by the rear group 1 first reflection surface 2 2, and the rear group 1 First Z-shaped first optical path reflected from the second reflecting surface 2 3 to the image surface 5 side, and then exits from the rear group 1 transparent medium L b to the image surface 5 side through the rear group 1 second transmission surface 24 A, and at least the rear of the first optical path A between the first group first reflective surface 2 2 and the rear first group second reflective surface 2 3 It consists only of one side of the shaft 2, without the intermediate image is formed in the first optical path A, and is imaged on the image plane 5 circularly annular.

[0 0 4 1]

Arranged in the order of the optical path from the object side on the central axis 2 in the aperture S and its vicinity Rear 1st group 1st transmissive surface 2 1 Rear 1st group 1st reflective surface 2 2 Rear 1st group 2nd reflective surface 2 3 It is important that the rear group 1 second transmission surface 2 4 is arranged in this order, and that the rear group 1 first reflection surface 2 2 and the rear group 1 second reflection surface 2 3 are both arranged with the concave surface facing the image side. is there.

[0 0 4 2]

It is important that the aperture S is located in the vicinity of the first transmission surface 21 of the first group after the object side.Astigmatism is increased when the aperture S is arranged on the image side of the first group of transparent media L b after the present invention. It is generated and a flat image cannot be formed. In addition, the emission chief ray tilt angle increases and telecentricity deteriorates. In addition, interference between the effective diameters of the rear first group first transmission surface 2 1 and the rear first group second reflection surface 2 3 occurs, making it impossible to obtain a large angle of view.

[0 0 4 3]

Next, the rear first group first reflective surface 2 2 and the rear first group second reflective surface 2 3 are concave on the image side. In addition, it is important that the optical path between the rear 1st group first reflecting surface 2 2 and the rear 1st group second reflecting surface 2 3 is composed of one side without straddling the axis of rotational symmetry and is a Z-shaped optical path. It is. -[0 0 4 4]

This arrangement results in a negative and positive power arrangement in the order of the optical path from the object side, enabling a so-called retrofocus configuration, and widening the angle of view.

. In addition, this arrangement makes it possible to place the principal point of the optical system on the object side and take F-back. Furthermore, since an intermediate image is not formed in the middle of the optical path, the optical system can be reduced in size.

[0 0 4 5]

Furthermore, by arranging the reflecting surface between the transmitting surfaces, and configuring the reflecting surface with an internal reflecting surface, it is possible to reduce the occurrence of aberration due to the curvature of field. In addition, since the inclination of the light ray that strikes the rear first group first reflecting surface 2 2 becomes smaller than that in the air, a good result is also obtained for a wide angle of view.

[0 0 4 6]

In addition, the rear 1st group 1st reflecting surface 2 2 is configured so that rays with a wide angle of view are reflected by total reflection, and the incident angle at which the 1st group 1st reflecting surface 2 2 near the center of the angle of view does not totally reflect. It is preferable to apply a reflective coating 4a to the center of the rear first group first reflecting surface 22 so as to reflect the light beam. This makes it possible to capture an image at the center of the angle of view. In addition, since the back of the first group 1st reflecting surface 2 2 is totally reflected, it is desirable not to perform reflection coating on this part. This prevents the central beam from being blocked from exiting the optical system.

[0 0 4 7]

Further, it is preferable that the rear first group first transmission surface 21 and the rear first group second reflection surface 23 be disposed close to the object side of the rear first group transparent medium Lb. This reduces the interference of light rays on each other, and ensures a wide angle of view.

[0 0 4 8] Further, it is preferable that the rear first group first reflecting surface 2 2 and the rear first group second transmitting surface 24 be close to the image surface 5 side of the transparent medium L. This makes it possible to shorten the transparent medium L and the image plane 5. It is possible to shorten the overall length of the optical system.

[0 0 4 9]

Further, it is desirable that the rear first group second reflecting surface 23 be provided with a reflective coating 4 b in the peripheral portion, and the central portion is provided with the rear first group first transmitting surface 21 or the opening S. It is desirable not to

[0 0 5 0]

More preferably, the rear first group first reflecting surface 2 2 and the rear first group second transmitting surface 24 are preferably formed in the same place and in the same shape. With this configuration, it is possible to partially use total reflection on the first group first reflecting surface 2 2 later, and a wide angle of view of the optical system can be obtained.

[0 0 5 1]

More preferably, the rear first group first transmitting surface 2 1 and the rear first group second reflecting surface 2 3 are preferably formed in the same place and in the same shape. This configuration improves workability.

[0 0 5 2]

Further, the front group G f has a front group transparent medium L f having a rotationally symmetric refractive index greater than 1 around the central axis 2, and the front group transparent medium L is arranged in the order of the optical path in the order of the optical path. 1 1 and the front group first reflecting surface 1 2 and the front group first reflecting surface 1 2 centered on the image plane 5 side opposite to the front group first transmitting surface 1 1 and the central axis 2 Front group second reflecting surface 1 3 disposed on the same side of axis 2 as front group first reflecting surface 1 2 and on the opposite side of image surface 5 from front group second reflecting surface 1 2, and image surface 5 from front group second reflecting surface 1 3 And the front group second transmission surface 14 disposed on the side, and the light beam incident on the front group transparent medium L f passes through the front group first transmission surface 1 1 in the order of forward ray tracing. Entered into the medium L f, reflected by the front group first reflective surface 1 2 to the opposite side of the image surface 5, reflected by the front group second reflective surface 1 3 to the image surface 5 side, and front group second transmission surface 1 4 through the front transparent media It is preferable to configure an optical path that exits from L f to the image plane 5 side.

[0 0 5 3]

Further, the front group G f has a front group transparent medium L f having a rotationally symmetric refractive index greater than 1 around the central axis, and the front group transparent medium L f is arranged in the order of the optical path in the front group first transparent surface. 1 1 and front group first reflecting surface 1 1 and front group first reflecting surface 1 2 placed on the image plane 5 side on the opposite side across 1 and center axis 2 and front group first reflecting surface 1 2 and center The front group second reflecting surface 1 3 disposed on the opposite side of the axis 2 from the front group first reflecting surface 1 2 and opposite to the image surface 5 from the front group first reflecting surface 1 2, and the front group second reflecting surface 1 3 from the image surface 5 The light beam incident on the front group transparent medium L f passes through the front group first transmission surface 1 1 in the order of forward ray tracing. Enters the medium L f, reflected by the front group first reflective surface 1 2 to the opposite side of the image surface 5, reflected by the front group second reflective surface 1 3 to the image surface 5 side, and front group second transmission surface Configure the optical path going out from the front group transparent medium L f to the image plane 5 side via 1 4 Door is preferable.

[0 0 5 4]

The front group G f has a front group transparent medium L f whose rotational refractive index is greater than 1 around the central axis 2, and the front group transparent medium L f is transmitted through the front group first transmission in the order of the optical path. Surface 1 1, front group first reflective surface 1 1 and front group first reflective surface 1 2 disposed on the opposite side of image plane 5 on the opposite side of front axis first transmission surface 1 1 and central axis 2 2 and the front group second transmission surface 1 4 disposed on the image plane 5 side from 2. The light beam incident on the front group transparent medium L f is in the order of forward ray tracing in the order of the front beam first transmission surface 1 1. After passing through the front group transparent medium L f, reflected to the image plane side by the front group first reflecting surface 12, and then passed from the front group second transparent surface 14 to the image group 5 side from the front group transparent medium L f. It is preferable to construct an optical path that goes out.

[0 0 5 5]

When the maximum image height is I max and the outer diameter of the transparent medium is D,

It is desirable to satisfy the following condition: 0.5 <D Z (2 X I max) <1 0 (1)

[0 0 5 6] In conditional expression (1), when the lower limit is exceeded, the telecentricity deteriorates, and in particular, when taking an image using an image sensor such as a CCD, the peripheral light quantity is insufficient. If the upper limit is exceeded, the outer diameter of the optical system becomes too large and the optical system becomes large.

[0 0 5 7]

When the maximum image height is I niax and the distance from the aperture to the image plane is L,

It is desirable to satisfy the following condition: 0.5 <L / (2 X 1 max) <1 0 · · · (2)

[0 0 5 8]

Conditional expression (2) defines the total length of the optical system with respect to the image height. If the lower limit is exceeded, the telecentricity also deteriorates and the peripheral light quantity is insufficient. If the upper limit is exceeded, the total length becomes too long, and a compact optical system cannot be constructed.

[0 0 5 9]

Also, when the curvature of the rear first group first reflective surface 2 2 is 1, and the curvature of the rear first group second reflective surface 2 3 is R 2,

0.2 <R 1 / R 2 <5 * · (3) It is desirable to satisfy the following condition.

[0 0 6 0]

Conditional expression (3) regulates the ratio of the power of the two reflecting surfaces. When the lower limit is exceeded, the radius of curvature of the rear first group first reflecting surface 2 2 becomes smaller, and the rear first group first Compared with the positive power of 2 reflecting surface 2 3, the negative power of rear 1st group 1st reflecting surface 2 2 becomes larger and the total length of the optical system cannot be shortened. When the upper limit is exceeded, the curvature of the rear first group second reflecting surface 23 becomes smaller, the positive power of the rear first group second reflecting surface 23 becomes too large, and a large curvature of field on the object side occurs.

[0 0 6 1]

Note that all the examples are composed of spherical surfaces, but are composed of ordinary aspherical surfaces. It is also possible to make it. The parallel plane on the object side is for protecting the optical system. There is no need. The parallel plane on the image side is for protecting the image sensor and may be omitted.

[0 0 6 2]

Examples 1 to 4 of the optical system of the present invention will be described below. The configuration parameters of these optical systems will be described later.

[0 0 6 3]

In forward ray tracing, for example, as shown in Fig. 1, the coordinate system uses the point where the diaphragm surface S intersects the central axis 2 as the origin O of the decentered optical surface, and the direction perpendicular to the central axis 2 as the Y-axis direction. The Y-Z plane is the inside of the paper in Figure 1. The direction on the image plane 5 side in FIG. 1 is the Z-axis positive direction, and the Y-axis, the Z-axis and the axis that forms the right-handed orthogonal coordinate system are the X-axis positive direction.

[0 0 6 4]

For the eccentric surface, the amount of eccentricity from the origin 〇 of the optical system 1 in the coordinate system in which the surface is defined (X, Y, and Z are X, Y, and Z, respectively) and the optical system 1 The coordinate system tilt angles (α, β, r (°)) that define each surface around the X, Y, and Z axes of the coordinate system defined at the origin of ing. In that case, the positive α and | 6 mean counterclockwise rotation with respect to the positive direction of each axis, and the positive a means clockwise rotation with respect to the positive direction of the axis. It should be noted that the rotation of α, / 3, and a on the central axis of the surface is performed by rotating the coordinate system defining each surface counterclockwise around the X axis of the coordinate system defined as the origin of the optical system. Rotate α, then rotate counterclockwise / 3 around the axis of the new rotated coordinate system, and then clockwise around the axis of another rotated new coordinate system Rotate.

[0 0 6 5]

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

[0 0 6 6]

In addition, the term for aspheric surfaces for which no data is described in the constituent parameters described later is zero. Refractive index and Abbe number are shown for d-line (wavelength 5 8 7.5 6 nm). The unit of length is mm. The eccentricity of each surface is expressed by the amount of eccentricity from the reference surface as described above.

[0 0 6 7]

An aspherical surface is a rotationally symmetric aspherical surface given by the following definition.

Z = (Y ² ZR) Z [1 + ί 1-(1 + k) Y ² / R ² } ^1/2 ]

+ a Y ⁴ + b Y ⁶ + c Y ⁸ + d Y ¹⁰ +-

(a) where Z is the axis and Y is perpendicular to the axis. Where R is the paraxial radius of curvature, k is the conic constant, a, b, c, d, ... are the 4th, 6th, 8th, and 10th order aspherical coefficients, respectively. The Z axis of this definition is the axis of the rotationally symmetric aspheric surface.

[0 0 6 8]

An extended rotational free-form surface is a rotationally symmetric surface given by the following definition.

[0 0 6 9]

First, as shown in Fig. 2, the following curve (b) passing through the origin on the Y-Z coordinate plane is determined.

[0 0 7 0]

Z = (Y ² ZR Y.) / [1 + {1-(C, + 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 ² ° + · · · · + C _{n + 1} Y "+ · · · ·

• · · (b)

[0 0 7 1]

Next, turn this curve (b) in the positive direction of the X-axis and turn counterclockwise positive. Θ) A rotated curve F (Y) is defined. This curve F (Y) also passes through the origin on the Y-Z coordinate plane.

[0 0 7 2]

Move the curve F (Y) in the Y positive direction by a distance R (Y negative direction if negative), and then rotate the parallel symmetry curve around the Z axis. An extended rotation free-form surface.

[0 0 7 3]

As a result, the extended rotation free-form surface becomes a free-form surface (free curve) in the Y—Z plane and a circle with a radius I R I in the X—Y plane.

[0 0 7 4]

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

[0 0 7 5]

Where RY is the radius of curvature of the spherical term in the Y-Z section, C is the conic constant, C ₂ , C ₃ , C ₄ , C ₅ ... are the 1st, 2nd, 3rd, 4th ... Aspheric coefficient.

[0 0 7 6]

Note that the conical surface with the Z axis as the central axis is given as one of the extended rotation free-form surfaces, and RY = ∞, C,, C ₂ , C 3, C ₄ , CJ,. = (Conical angle of cone), R = (bottom radius in the X—Z plane)

[0 0 7 7]

In addition, the term for aspheric surfaces for which no data is described in the constituent parameters described later is zero. The refractive index and Abbe number are shown for the d-line (wavelength 5 8 7.5 6 nm). The unit of length is mm. The eccentricity of each surface is expressed by the amount of eccentricity from the reference surface as described above.

[0 0 7 8]

A sectional view taken along the central axis 2 of the optical system 1 of Example 1 is shown in FIG. Further, FIG. 4 shows a lateral aberration diagram of the entire optical system of this example. This lateral aberration diagram The angle shown in the center indicates (horizontal field angle, vertical field angle), and the lateral aberrations in the Y direction (meridinal direction) and X direction (sagittal direction) at that field angle. Note that a negative field angle means a clockwise angle when facing the Y-axis positive direction for the horizontal field angle, and a clockwise angle when facing the X-axis positive direction for the vertical field angle. same as below.

[0 0 7 9]

This embodiment is a spherical surface in which the transmission surface and the reflection surface of the first group of transparent media L b are used in common in the optical path after the refractive index that is rotationally symmetric with respect to the central axis 2 of the optical system 1 is greater than 1. In this example, the front group transparent medium L f is arranged as the front group G f of the first group transparent medium L b.

[0 0 8 0]

The optical system 1 includes a front group G f, a rear group G b, and an aperture S arranged coaxially with the central axis 2 between the front group G f and the rear group G b. The rear group G b It consists of rear 1 group G b 1 and rear 2 group G b 2.

[0 0 8 1]

The front group G f is composed of a front group transparent medium L f having a refractive index rotationally symmetric around the central axis 2 greater than 1. The front group transparent medium L f is made of a resin or the like having a refractive index of rotation greater than 1 around the central axis 2, and the front group first transmission surface 1 is formed of an extended rotation free-form surface by incidence of a light beam from a distance. 1 and the front group first transmission surface 1 1 and the central axis 2 are arranged on the opposite side of the front group first transmission surface 1 1 from the image plane 5 side, and from the front group first transmission surface 1 1 The front group first reflecting surface 1 2 consisting of a free-form curved surface with incident light flux and an image from the front group first reflecting surface 1 2 on the same side of the front group first reflecting surface 1 2 and the central axis 2 Located on the opposite side of surface 5, faces the front group second reflecting surface 1 3 consisting of the extended rotation free-form surface and the rear group G b when the light beam reflected by the front group first reflecting surface 12 enters. Thus, the light beam reflected by the front-group second reflecting surface 1 3 is incident and the front-group second transmitting surface 14 is formed of a spherical surface.

[0 0 8 2] The rear group 1 G b 1 is composed of a rear group 1 transparent medium L b whose refractive index rotationally symmetric about the central axis 2 is greater than 1. The rear first group transparent medium Lb is formed on the image side with respect to the rear first group first transmission surface 2 1 and the rear first group first transmission surface 2 1 formed of a spherical surface on the central axis 2, and partly Reflective coating 4a and after the concave surface is directed to the negative image side, the first group 1st reflection surface 2 2 and the back 1st group 1st reflection surface 2 2 opposite to the image surface 5 Is placed on the back, and the reflective coating 4 b is applied, and the concave surface is directed to the image surface side having a positive power, and then the first group second reflecting surface 2 3, and the rear first group second reflecting surface 2 3 to the image surface 5 side. And rear group 1 having a negative power and a second transmitting surface 2 4. Rear 1st group 1st transmission surface 2 1 and rear 1st group 2nd reflection surface 2 3 have the same position and same shape, Rear 1st group 1st reflection surface 2 2 and Rear 1st group 2nd transmission surface 2 4 are the same It consists of the same shape.

[0 0 8 3]

The rear 2 group G b 2 is composed of the rear 2 group cover glass C b 2 whose refractive index rotationally symmetric around the central axis 2 is greater than 1. The rear 2nd group cover glass Cb2 is formed of a flat plate, and is formed on the image side with respect to the rear 2nd group first transmitting surface 3 1 and the rear 2nd group first transmitting surface 3 1. 2 transmissive surface 3 2.

[0 0 8 4]

The optical system 1 forms the optical path A. The light flux incident from the object plane 3 of the optical system 1 passes through the front group first transmission surface 1 1 of the front group transparent medium L f, crosses the central axis 2, and is opposite to the front group first transmission surface 1 1. Is reflected upward from the front group first reflective surface 1 2 away from the rear group G b, and from the rear group G b on the same side as the front group first reflective surface 1 2 and the central axis 2. Reflected again in the rear group G b direction by the front group second reflecting surface 1 3 located on the far side, and exits from the front group transparent medium L f via the front group second transmitting surface 14 of the exit surface .

[0 0 8 5]

Thereafter, the light enters the rear first group transparent medium Lb through the opening S arranged coaxially with the central axis 2 between the front group transparent medium Lf and the rear first group transparent medium Lb. Rear 1st group transparent medium Lb enters through rear 1st group 1st transmission surface 2 1 and rear 1st group 1st reflection surface 2 2 is partially reflected coating 4a, partly reflected to the opposite side of image plane 5 by total reflection, and rear 1st group second reflecting surface 2 3 is reflected to image surface 5 side by reflecting coating 4b In addition, it has a substantially Z-shaped optical path that exits from the rear group 1 transparent medium Lb through the rear group 1 second transmission surface 24. After that, the rear 2nd group cover glass Cb 2 passes through the rear 2nd group 1st transmission surface 3 1 and the rear 2nd group 2nd transmission surface 3 2 to a predetermined radial position away from the center axis 2 of the image plane 5. It forms an image in an annular shape.

[0 0 8 6]

The specification of Example 1 is

Angle of view of the entire system 50.00 ° to 360.0 °

Rear group angle of view 26. 8 1 ° to 60. 22 °

Entrance pupil diameter Φ 0.94mm

The size of the image Φ 4. 04mD! ~ Φ 7. 83mm

It is.

[0 0 8 7]

A sectional view taken along the central axis 2 of the optical system 1 of Example 2 is shown in FIG. Further, FIG. 6 shows a lateral aberration diagram of the entire optical system of this example.

[0 0 8 8]

In this example, the transmission surface and the reflection surface of the rear group transparent medium Lb having a refractive index larger than 1 concentric with the central axis 2 of the optical system 1 are partially shared in the optical path. This is an example in which the front group transparent medium L f is arranged as the front group G f of the rear group transparent medium L b.

[0 0 8 9]

The optical system 1 includes a front group G f, a rear group G b, and an aperture S arranged coaxially with the central axis 2 between the front group G f and the rear group G b. The rear group G b It consists of the first group G 1 and the second group G 2.

[0 0 9 0]

The front group G f is composed of a front group transparent medium L f having a refractive index rotationally symmetric around the central axis 2 greater than 1. The front group transparent medium L f is a rotating pair around the central axis 2. The front group first transmission surface 1 1, the front group first transmission surface 1 1, and the central axis 2 are made of an extended rotation free-form surface. It is located on the opposite side of the front group first transmission surface 1 1 from the image plane 5 side, and the front group first transmission surface 1 1 enters the front group first transmission surface 1 1 Reflecting surface 1 2 and the front group first reflecting surface 1 2 and the central axis 1 are located on the opposite side of the front group first reflecting surface 1 2 from the image surface 5 on the opposite side, and the front group first reflecting surface 1 Front group second reflecting surface 1 3 consisting of an extended rotation free-form surface with the light beam reflected by 2 and the rear group G b on central axis 2 and imaged from front group second reflecting surface 1 3 It is arranged on the surface 5 side, and is composed of a front group second transmission surface 14 made of a spherical surface by the incident light beam reflected by the front group second reflection surface 13.

[0 0 9 1]

The rear group 1 G b 1 is composed of the rear group 1 transparent medium L b whose refractive index rotationally symmetric about the central axis 2 is greater than 1. The rear first group transparent medium Lb is formed on the image side with respect to the rear first group first transmission surface 2 1 and the rear first group first transmission surface 2 1 formed of a spherical surface on the central axis 2, and partly Reflective coating 4a, with the concave surface facing the negative image surface side, 1st group 1st reflection surface 2 2 and 1st group 1st reflection surface 2 2 opposite to image surface 5 After reflecting the concave coating on the image surface side with positive power and reflecting coating 4b, the 1st group 2nd reflecting surface 2 3 and the 1st group 2nd reflecting surface 2 3 on the image surface 5 side And rear group 1 having a negative power and a second transmitting surface 2 4. Rear 1st group 1st transmission surface 2 1 and rear 1st group 2nd reflection surface 2 3 are in the same position and same shape, Rear 1st group 1st reflection surface 2 2 and Rear 1st group 2nd transmission surface 2 4 are the same It consists of the same shape.

[0 0 9 2]

[0 0 9 3] The optical system 1 forms the optical path A. In the optical path A, the light beam incident from the object plane 3 of the optical system 1 enters the front group transparent medium L f via the front group first transmission surface 11 and crosses the central axis 2 before the first group first transmission surface 1. Reflected upward on the opposite side of the image plane 5 away from the rear group G b at the front group first reflective surface 1 2 on the opposite side of 1, and against the front group first reflective surface 1 2 and the central axis 2 The front group second reflecting surface 1 3 located on the opposite side and further away from the rear group G is reflected to the image plane 5 side, and the front group is transparent through the front group second transmitting surface 14 of the emitting surface. Get out of medium L f.

[0 0 9 4]

After that, it passes through the opening S arranged on the same axis as the central axis 2 between the front group transparent medium Lf and the rear group 1 transparent medium Lb, and then enters the rear group 1 transparent medium Lb. Rear group 1 Transparent medium L b enters through rear group 1 first transmission surface 2 1, rear group 1 first reflection surface 2 2, part is reflective coating 4 a, other part is total reflection, image surface 5 Is reflected to the image surface 5 side by the reflective coating 4b at the rear 1st group 2nd reflecting surface 2 3 and then passes through the 1st group 2nd transmitting surface 24 and the rear 1st group transparent medium Lb It has an approximately Z-shaped optical path that goes out of the window. After that, the rear 2nd group cover glass Cb 2 passes through the rear 2nd group 1st transmission surface 3 1 and the rear 2nd group 2nd transmission surface 3 2 to a predetermined radial position away from the central axis 2 of the image plane 5. It forms an image in an annular shape.

[0 0 9 5]

The specification of this Example 2 is

Angle of view of the entire system 80.00 ° to 360 °

Rear group angle of view 22.92 ° to 58.29 °

Entrance pupil diameter Φ 0.10mm

The size of the image Φ 3. 58mn! ~ Φ 7. 9 1mm

It is.

[0 0 9 6]

A sectional view taken along the central axis 2 of the optical system 1 of Example 3 is shown in FIG. Further, FIG. 8 shows a lateral aberration diagram of the entire optical system of this example.

[0 0 9 7] In this embodiment, the transmission surface and the reflection surface of the rear group transparent medium Lb having a refractive index that is concentric and rotationally symmetric with respect to the central axis 2 of the optical system 1 are larger than 1. This is an example in which the front group transparent medium f is arranged as the front group G f of the rear group transparent medium L b.

[0 0 9 8]

The optical system 1 includes a front group G f, a rear group G b, and an aperture S arranged coaxially with the central axis 2 between the front group G f and the rear group G b.

[0 0 9 9]

The front group G f is composed of a front group transparent medium L f having a refractive index rotationally symmetric around the central axis 2 greater than 1. The front group transparent medium L f is made of a resin or the like having a refractive index of rotation greater than 1 around the central axis 2, and the front group first transmission surface 1 is formed of an extended rotation free-form surface by incidence of a light beam from a distance. 1 and the front group first transmission surface 1 1 and the central axis 2 are located on the opposite side of the front group first transmission surface 1 1 from the image surface 5 opposite to the front group first transmission surface 1 1 The front group first reflecting surface 1 2 consisting of an extended rotation free-form surface with the incident light beam from the front and the rear group G b facing the rear group G b on the central axis 2 from the front group first reflecting surface 1 2 to the image surface 5 And a front group second transmission surface 14 made of an aspherical surface on which the light beam reflected by the front group first reflection surface 12 is incident.

[0 1 0 0]

The rear group G 1 is composed of a rear group 1 transparent medium L b having a rotationally symmetric refractive index greater than 1 around the central axis 2. The rear first group transparent medium Lb is formed on the image side with respect to the rear first group first transmission surface 2 1 and the rear first group first transmission surface 2 1 formed of a spherical surface on the central axis 2, and partly Reflective coating 4 a, and after the concave surface is directed to the negative image side, the first group 1st reflecting surface 2 2 and the rear 1 group 1st reflecting surface 2 2 opposite to the image surface 5 Is arranged, partly reflective coating 4b, and rear 1st group 2nd reflective surface 2 3 with positive par, and rear 1st group 2nd reflective surface 2 3 are placed on the image plane 5 side, negative Powerful rear 1 group 2nd transmission surface 2 4 Rear 1st group 1st transmitting surface 2 1 and Rear 1st group 2nd reflecting surface 2 3 have the same shape at the same position. The rear first group first reflecting surface 2 2 and the rear first group second transmitting surface 24 have the same shape at the same position.

[0 1 0 1]

The optical system 1 forms the optical path A. In the optical path A, the light beam incident from the object plane 3 of the optical system 1 enters the front group transparent medium L f via the front group first transmission surface 1 1, crosses the central axis 2, and the front group first transmission surface 1. The front group first reflecting surface 1 on the opposite side of 1 is reflected downward toward the rear group G b toward the rear group G b toward the image surface 5 side, passes through the front group second transmitting surface 14 of the exit surface, and passes through the front group transparent medium L. Get out of f.

[0 1 0 2]

After that, it passes through the opening S arranged on the same axis as the central axis 2 between the front group transparent medium Lf and the rear group 1 transparent medium Lb, and then enters the rear group 1 transparent medium Lb. Rear group 1 Transparent medium L b enters through rear group 1 first transmission surface 2 1, rear group 1 first reflection surface 2 2, part is reflective coating 4 a, other part is total reflection, image surface 5 Is reflected to the image surface 5 side by the reflective coating 4b at the rear 1st group 2nd reflecting surface 2 3 and then passes through the 1st group 2nd transmitting surface 24 and the rear 1st group transparent medium Lb It has an approximately Z-shaped optical path that goes out of the window. Thereafter, an image is formed in an annular shape at a predetermined position in the radial direction deviating from the central axis 2 of the image plane 5.

[0 1 0 3]

The specification of Example 3 is

Angle of view of the entire system 60.00 ° X 360 °

Rear group angle of view 13.52 ° to 52.56 °

Rear group entrance pupil diameter φ 1.00mm

The size of the image ψ 2.44mn! ~ Φ 7.95mm

It is.

[0 1 0 4]

A sectional view taken along the central axis 2 of the optical system 1 of Example 4 is shown in FIG. Further, FIG. 10 shows transverse aberration diagrams of the whole optical system of this example.

[0 1 0 5] In this embodiment, the transmission surface and the reflection surface of the rear group transparent medium Lb having a refractive index that is concentric and rotationally symmetric with respect to the central axis 2 of the optical system 1 are larger than 1. This is an example in which the front group transparent medium L f is arranged in front of the rear group transparent medium L b.

[0 1 0 6]

[0 1 0 7]

The front group G f is composed of a front group transparent medium L f having a refractive index rotationally symmetric around the central axis 2 greater than 1. The front group transparent medium L f is made of a resin or the like whose rotational refractive index is greater than 1 around the central axis 1, and the front group first transmitting surface 1 formed of an extended rotation free-form surface by the incident light beam 2 from a distance. 1 and the first transmission surface 1 1 of the front group and the front axis first transmission surface 1 1 on the opposite side of the central axis 1 from the front group first transmission surface 1 1. The front group first reflecting surface 1 2 consisting of an extended rotation free-form surface and the front group first reflecting surface 1 2 and the central axis 1 on the opposite side across the central axis 1 2 The light beam reflected by the front first group reflecting surface 12 is incident on the opposite side of the image surface 5 and is incident on the front group second reflecting surface 13 consisting of an extended rotation free curved surface and the rear group G b. Located on the image plane 5 side of the front group second reflective surface 1 2 and the central axis 2 on the image plane 5 side from the front group second reflective surface 1 2, and the light beam reflected by the front group second reflective surface 13 is incident The second transmission of the front group consisting of aspherical surfaces Consisting of 1 4.

[0 1 0 8]

The rear group 1 G b 1 is composed of a rear group 1 transparent medium L b whose refractive index rotationally symmetric about the central axis 2 is greater than 1. Rear 1st group transparent medium Lb is formed on the image side with respect to rear 1st group 1st transmission surface 2 1 and rear 1st group 1st transmission surface 2 1 consisting of a spherical surface on central axis 2, and partly Reflective coating 4a, and after the concave surface is directed to the negative image side, the first group 1st reflecting surface 2 2 and the back 1 group 1st reflecting surface 2 2 opposite to the image surface 5 Placed in the reflective coating 4b and positive 1st group 2nd reflection surface 2 3 after the concave surface is directed to the image surface side with, and 1st group 2nd transmission after 1st group 2nd reflection surface 2 3 Surface 2 and 4. Rear 1st group 1st transmission surface 2 1 and rear 1st group 2nd reflection surface 2 3 have the same position and same shape, Rear 1st group 1st reflection surface 2 2 and Rear 1st group 2nd transmission surface 2 4 are the same It consists of the same shape.

[0 1 0 9]

The optical system 1 forms the optical path A. In the optical path A, the light beam incident from the object plane 3 of the optical system 1 enters the front group transparent medium L f via the front group first transmission surface 1 1, crosses the central axis 2, and the front group first transmission surface 1. Reflected on the opposite side of the image surface 5 away from the rear group G b by the front group first reflective surface 1 2 on the opposite side of 1, and opposite to the front group first reflective surface 1 2 and the central axis 2 Is reflected to the image plane 5 side by the front group second reflecting surface 1 3 located on the side away from the rear group G b and passes through the front group second transmitting surface 14 of the exit surface and passes through the front group transparent medium L f Go out from.

[0 1 1 0]

After that, it passes through the opening S arranged on the same axis as the central axis 2 between the front group transparent medium Lf and the rear group 1 transparent medium Lb, and then enters the rear group 1 transparent medium Lb. Rear group 1 Transparent medium L b enters through rear group 1 first transmission surface 2 1, rear group 1 first reflection surface 2 2, partly reflective coating 4 a, partly total reflection and image surface 5 Reflected on the opposite side, reflected back to the image surface 5 side by the reflective coating 4 b on the rear 1st group second reflecting surface 2 3, then passed through the rear 1st group second transmitting surface 2 4 and then back from the 1st group transparent medium L b It has an approximately Z-shaped optical path that goes out. Thereafter, an image is formed in an annular shape at a predetermined position in the radial direction deviating from the central axis 2 of the image plane 5.

[0 1 1 1]

The specification of this Example 4 is

Angle of view of the entire system 60.00 ° X 360 °

Rear group angle of view 26.47 °-55.67 °

Rear group entrance pupil diameter Φ 1.OOmm

Image size ψ 4.12mii! ~ Φ 7.66mm It is.

[0 1 1 2]

A cross-sectional view taken along the central axis 2 of the optical system 1 of Example 5 is shown in FIG. In addition, FIG. 12 shows a lateral aberration diagram of the entire optical system of this example.

[0 1 1 3]

In this embodiment, the transmission surface and the reflection surface of the rear group transparent medium Lb having a refractive index that is concentric and rotationally symmetric with respect to the central axis 2 of the optical system 1 are larger than 1. This is an example in which a front group reflector R f is arranged in front of the rear group transparent medium L b.

[0 1 1 4]

[0 1 1 5]

The front group G f consists of a front group reflector R f that is rotationally symmetric about the central axis 2. The front group reflector R f is composed of a front group first reflecting surface 12 that is convex toward the image plane 5 side.

[0 1 1 6]

The rear group 1 G b 1 is composed of a rear group 1 transparent medium L b whose refractive index rotationally symmetric about the central axis 2 is greater than 1. The rear first group transparent medium Lb is formed on the image side with respect to the rear first group first transmission surface 2 1 and the rear first group first transmission surface 2 1 formed of a spherical surface on the central axis 2, and partly Reflective coating 4a and after the concave surface is directed to the negative image side, the first group 1st reflection surface 2 2 and the back 1 group 1st reflection surface 2 2 opposite to the image surface 5 After reflecting the concave coating on the image surface side with positive power and reflecting coating 4b, the 1st group 2nd reflecting surface 2 3 and the 1st group 2nd reflecting surface 2 3 on the image surface 5 side And rear group 1 having a negative power and a second transmitting surface 2 4. Rear 1st group 1st transmission surface 2 1 and rear 1st group 2nd reflection surface 2 3 have the same position and same shape, Rear 1st group 1st reflection surface 2 2 and Rear 1st group 2nd transmission surface 2 4 are the same It consists of the same shape.

[0 1 1 7] The optical system 1 forms the optical path A. In the optical path A, the light beam incident from the object surface 3 of the optical system 1 is between the front group first reflecting surface 1 1 of the front group reflector R f and between the front group reflector R f and the rear group 1 transparent medium L b. Then, after passing through the opening S arranged coaxially with the central axis 2, the light enters the first group of transparent media Lb. After that, it passes through the opening S arranged coaxially with the central axis 2 between the front group transparent medium Lf and the rear group 1 transparent medium Lb, and enters the rear group 1 transparent medium Lb. Rear 1st group transparent medium Lb enters through rear 1st group 1st transmission surface 2 1, rear 1st group 1st reflection surface 2 2, part is reflection coating 4a, part is image by total reflection Reflected on the opposite side of surface 5, reflected back to the image surface 5 side by the reflective coating 4b at the first group 2 second reflecting surface 2 3 and then passed through the first group 2 second transmitting surface 24 and rear 1 group transparent medium L It has an approximately Z-shaped optical path that exits from b. Thereafter, an image is formed in an annular shape at a predetermined position in the radial direction deviating from the central axis 2 of the image plane 5.

[0 1 1 8]

The specification of Example 5 is

Angle of view of the entire system 60.00 ° (10 ± 30 °) X 360 °

Rear group angle of view 29.59 °-49.38 °

Rear pupil diameter <ί> 1.00mm

The size of the statue Φ 2.56! ~ Φ 3.92mm

It is.

[0 1 1 9]

The maximum image height is I max (mm), the minimum image height is I min (mm), the maximum field angle of the rear group G r is 0 max (degrees), and the minimum field angle of the rear group G r is e min ( Degree), focal length F = (I max-I min) / (Θ max-Θ min), rear group G r outer diameter D (mm), rear group G r When the total length is L (mm), the curvature of the rear group first reflecting surface 22 is 1, and the curvature of the rear group second reflecting surface 2 3 is R2, Example 1 Example 2 Example 3 Example 4 Example 5

I max 3.92 3.96 3.98 3.83 1.96

Θ max 60.22 58.29 52.56 55.67 49.38

I min 2.02 1.78 1.22 2.06 1.28

Object plane Ψ [

The real o

No. 1

Θ mm 26. 81 22. 92 13. 52 26. 47 29. 59

F 0. 057 0. 061 0. 071 0. 061 0. 034

D 24. 80 21. 60 25. 20 20. 40 12. 00

L 9. 600 7. 800 13. 000 6. 20 4. 20

D (2X Imax) 3. 167 2. 730 3. 169 2. 663 3. 069

L (2X Imax) 1. 226 0. 986 1. 635 0. 809 1. 074

R 1 6. 92 7. 33 8. 06 9. 35 3. 32

R 2 8. 10 8. 15 8. 95 8. 89 4. 13

R 1 / R 2 0. 85 0. 90 0. 90 1. 05 0. 81.

[0 1 2 0]

The configuration parameters of Example 5 are shown below. The table below

“R E” indicates a reflective surface.

twenty one ]

Example 1

Radius of curvature Face spacing Eccentric Refractive index Abbe

∞ oo eccentricity (1)

1 E R F S [1] 0. 00 Eccentric (2) 1. 8348 42. 7

2 R E) E R F S [2〗 0. 00 Eccentricity (3) 1. 8348 42. 7 3 R E) E R F S [3] 0. 00 Eccentricity (4) 1. 8348 42.7 4 0. 00 Eccentricity (5)

5 ∞ (Aperture) 0.00

6 8. 10 3. 48 1. 8348 42. 7 7 R E) 6.92-3. 48 1. 8348 42. 7 8 R E) 8. 10 3. 48 1. 8348 42. 7 9 6. 92 4. 23

10 oo 1. 00 1. 5163 64. 1 11 oo 0. 70

w plane oo

E R F S [1]

R Y 27. 36

Θ 53. 19

R -10. 91

E R F S [2]

R Y -23. 52

Θ 37. 63

R 7.93

C 4 2. 4445E-05

ERFS [3] -56.42

-5.65

6.05

8.0159E-05

Eccentric [1]

X 0.00 Y 0.00 Ζ -9. 64

75.00 β 0.00 r 0. 00

Eccentric [2]

X 0.00 Υ 0.00 z -12. 56

0.00 β 0.00 r 0. 00

Eccentric [3]

X 0.00 Υ 0.00 z -3. 71

0.00 β 0.00 r 0. 00

Eccentric [4]

X 0.00 Υ 0.00 z -13. 93

0.00 β 0.00 r 0. 00

Eccentric [5]

X 0.00 Υ 0.00 z-1. 00

0.00 β 0.00 r 0. 00

[0 1 2 2]

Example 2

Surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe Object surface οο CO Eccentricity (1)

1 E R F S [1] 0. 00 Eccentric (2) 1. 8348 42. 7

2 (R E) E R F S [2] 0. 00 Eccentricity (3) 1. 8348 42. 7

3 (R E) E R F S [3] 0. 00 Eccentricity (4) 1. 8348 42. 7

4 -6.46 0.00 Eccentric (5)

5 ∞ (Aperture) 0.00

6 8. 15 3. 33 1. 8348 42. 7

7 (R E) 7.33-3. 33 1. 8348 42. 7

8 (R E) 8. 15 3. 33 1. 8348 42.7

9 7.33 2. 66

10 οο 1. 00 1. 5163 64. 1

11 0Ο 0. 70

Image plane ∞

E R F S [1]

R Y -5.96

Θ 72.36

R -9.56

ERFS [2]

Face L

Real o

Out 1

R Y -16.71

Θ 50.86

R 7.55

C 4 -2.4173E -04

E R F S [3]

R Y 8 .79

Θ 31 .80

R -6 .39

C 4 1 • 9000E -03

Eccentric [1]

X 0. 00 Y 0 Z -5.79

a 42. 56 β 0 r 0.00

Eccentric [2]

X 0. 00 Y 0 Z 16.21

a 0. 00 β 0 r 0.00 I

Eccentric [3]

X 0. 00 Υ 0 Z -4.96

a 0. 00 β 0 r 0.00

Eccentric [4]

X 0. 00 Υ 0 Z 18.89

a 0. 00 β 0 r 0.00

Eccentric [5]

X 0. 00 Υ 0 z -0.10

a 0. 00 β 0 r 0.00

twenty three ]

Example 3

Refractive index Abbe number

1.8348 42.7

4 ∞ (Aperture) 0.10

7 8.95 3.62 1.8348 42.7 8 (R E) 8.06-3.62 1.8348 42.7 9 (R E) 8.95 3.62 1.8348 42.7

10 8.06 9.31

Statue m oo

E R F S [1]

RY -2685 93 R -6.91

E R F S

R Y 14. 47

Θ -45. 37

R 5. 36

C 4 -4. 6617E-05

Eccentric [1]

X 0. 00 Y 0.00 Z -7. 24

-90.00 β 0.00 r 0. 00

Eccentric [2]

X 0. 00 Υ 0.00 z -7. 24

0. 00 β 0.00 Ύ 0. 00

Eccentric [3]

X 0. 00 Υ 0.00 Z -12. 35

0. 00 β 0.00 r 0. 00

Eccentric [4]

X 0. 00 Υ 0.00 z -0. 10

0. 00 β 0.00 r 0. 00

[0 1 2 4]

Example 4

Surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe Object surface CO oo Eccentricity (1)

1 E R F S [1] 0. 00 Eccentric (2) 2. 0033 28. 3

2 (R E) E R F S [2] 0. 00 Eccentricity (3) 2. 0033 28. 3

3 (R E) E R F S [3] 0. 00 Eccentricity (4) 2. 0033 28. 3

4 A S S [1] 0. 00 Eccentric (5)

5 ∞ (Aperture) 0. 10

6 8.89 3. 34 1. 8348 42. 7

7 (R E) 9.35 -3. 34 1. 8348 42. 7

8 (R E) 8.89 3. 34 1. 8348 42. 7

9 9.35 4. 76

E R F S [1]

21.56

Θ 88.06

R -7.74

E R F S [2]

R Y -13.48

Θ 87.67

R 8.55 C4 -1.5105E-04

E R F S [3]

R Y 10. 49

Θ 43. 16

R-6. 45

C4 6. 0876E-04

A S S [1]

R -12.90

k 0.0000

a 2.4853E-03

Eccentric [1] 1

X 0. 00 Y 0.00 ζ -14.91

132 .30 β 0.00 Ύ 0.00

Eccentric [2]

X 0. 00 Y 0 .00 ζ -6.96

0. 00 β 0 .00 r 0.00

Eccentric [3]

X 0. 00 Υ 0 .00 ζ

0. 00 β 0 .00 Ύ 0.00

Eccentric [4]

X 0. 00 Υ 0 .00 ζ

0. 00 β 0 .00 Ύ 0.00

Eccentric [5]

X 0. 00 Υ 0 .00 ζ -0. 10

0. 00 β 0 .00 r 0.00

[0 1 2 5]

Example 5

Radius of curvature Surface spacing Eccentricity Refractive index Abbe number Object surface oo oo

1 (R E) -16.88 5.00

2 ∞ (Aperture) 0. 10

3 4. 13 1.74 1. 8348 42. 7

4 (R E) 3.32 -1.74 1. 8348 42.7

5 (R E) 4. 13 1.74 1. 8348 42.7

6 3.32 2.52

Image plane CO

[0 1 2 6]

Hereinafter, the optical system of the present invention will be described based on Examples 6 to 10. [0 1 2 7]

FIG. 14 is a cross-sectional view taken along the central axis (rotation symmetry axis) 2 of the optical system 1 of Example 6 to be described later. Although the following description will be given as an imaging optical system, it can also be used as a projection optical system with the optical path reversed.

[0 1 2 8]

An optical system 1 according to the present invention is rotationally symmetric with respect to a central axis 2 and includes a front group G f including at least one reflecting surface, an aperture S, and a rear group G b. An intermediate image is placed in the optical path. An optical system 1 that forms or projects an image without forming it.

[0 1 2 9]

The optical system 1 of Example 6 includes a front group G f including at least one reflecting surface, a rear group G b, and an aperture S disposed between the front group G f and the rear group G b. In the optical system 1 that is rotationally symmetric about the central axis 2 in the cross section including the central axis 2, the rear group G b is disposed on the image plane 5 side of the aperture S and has a refractive index greater than 1. The rear group 1 transparent medium Lb as the transparent medium has the rear group 1 transparent surface Lb arranged on the central axis 2 in the vicinity of the opening S as the rear group first transmission surface. A rear surface group 1, a rear first group first reflecting surface 2 2, which is arranged on the image surface side from the rear first group first transmission surface 2 1, and has a concave surface facing the image surface side, and a rear first group first reflecting surface 2 2; Rear 1st group 2nd reflective surface 2 3 as rear 1st group 2nd reflective surface which is arranged on the opposite side to the image plane from rear 1st group 1st reflective surface 2 2 and has a concave surface facing the image side 2 Reflecting surface 2 3 Rear surface second transmitting surface arranged on the image side from 3 Rear 1st group 2nd transmission surface 24, and Rear 1st group 1st transmission surface 2 1, Rear 1st group 1st reflection surface 2 2, Rear 1st group 2nd reflection surface 2 3 and Rear 1st group 2nd The transmission surface 24 is a curved surface, and the light beam incident on the rear group 1 transparent medium Lb passes through the aperture S in the order of forward ray tracing, passes through the rear group 1 first transmission surface 21, and the rear group 1 transparent medium. Enters Lb, then reflects back to the opposite side of the image plane 5 from the first group 1st reflecting surface 2 2, reflects to the image surface 5 side from the back 1st group 2nd reflecting surface 2 3, and then back to the 1st group 2nd transmission After passing through the surface 2 4 and forming the first optical path A of approximately Z-shape that exits from the first group transparent medium L b to the image plane 5 side, and at least the rear of the first optical path A. Center axis 2 between 2 and rear 1st group 2nd reflecting surface 2 3 The object point around the central axis 2 crosses the central axis 2 once in the vicinity of the aperture S and is connected to the opposite side without forming an intermediate image in the first optical path A. As a whole, an image is formed in an annular shape on the image plane 5, and at least one of the reflecting surfaces of the rear group is composed of discontinuous rotationally symmetric surfaces on the central axis.

[0 1 3 0]

[0 1 3 1]

[0 1 3 2]

Next, it is possible to reduce the occurrence of aberrations such as field curvature by disposing the reflecting surface between the transmitting surfaces and configuring the reflecting surface with an internal reflecting surface. In addition, since the inclination of the light ray that strikes the rear first group first reflecting surface 22 is smaller than that in the air, a good result is also obtained for a wide angle of view.

[0 1 3 3]

Furthermore, it is important that the rear first group first reflecting surface 2 2 and the rear first group second reflecting surface 23 have a concave surface facing the image side.

[0 1 3 4]

This arrangement results in a negative and positive power arrangement in order of the optical path from the object side, so-called It becomes possible to make a retro focus configuration, and a wide angle of view becomes possible. In addition, this arrangement makes it possible to place the principal point of the optical system on the object side and take F-back.

[0 1 3 5]

Furthermore, it is important that the optical path between the rear first group first reflecting surface 22 and the rear first group second reflecting surface 23 is formed on one side without straddling the rotational symmetry axis.

[0 1 3 6]

Crossing the rotationally symmetric axis and the optical path means intermediate imaging with a sagittal section, and the optical path length becomes long, leading to an increase in the size of the optical system.

[0 1 3 7]

In addition, it is important to have a Z-shaped optical path.

[0 1 3 8]

By taking a Z-shaped optical path, it becomes possible to reduce the reflection angle on each surface and to reduce the occurrence of decentration aberrations. In addition, while the incident light beam from the aperture is relatively low (close to the axis of rotational symmetry), it can be applied to the rear group 1 first reflecting surface 2 2, and the rear group 1 first reflecting surface 2 2 is strongly negative. Even with this power, it is possible to reduce the occurrence of aberrations.

[0 1 3 9]

Furthermore, it is important to configure so that an intermediate image is not formed in the middle of the optical path.

[0 1 4 0]

If an image is formed in the middle of the optical path, the diameter of the light beam can be reduced. However, in an optical system characterized in that the total length of the optical system can be shortened as in the present invention, an intermediate image is formed when an intermediate image is formed. The total length becomes long, and it becomes impossible to make the optical system compact.

[0 1 4 1]

In addition, it is important that the object point around the central axis 2 intersects the central axis 2 once in the vicinity of the aperture S and forms an image on the opposite side. [0 1 4 2]

The light beam from the object passes through the aperture S on the central axis 2 and at the same time intersects the central axis 2 once and enters the opposite side of the object. Therefore, it is reflected and imaged by each reflecting surface, but if it is configured to form an image on the same side of the object and the central axis 2, it needs to intersect the central axis 2 again before it is imaged. . In the sagittal section, the crossing of the light beam that has passed through the aperture S on the central axis 2 again with the central axis 2 means that an image of the aperture S is formed. If the image is re-imaged, the exit pupil will be in the vicinity of the image, making it impossible to improve telecentricity. In addition, it is necessary to provide extra power for this purpose in the optical path, leading to an increase in the size of the optical system.

[0 1 4 3]

Next, it is important that the image plane 5 is an annular plane image plane.

[0 1 4 4]

By forming an image of an annular plane, it is possible to image or project with one plane imaging element or display element.

[0 1 4 5]

In addition, it is important that at least one of the reflecting surfaces of the rear group Gb is composed of a rotationally symmetric surface that is discontinuous on the central axis.

[0 1 4 6]

The degree of freedom to arbitrarily set the size of the image formed in an annular shape is increased, and in the case of an imaging optical system, the imaging device can be used effectively. In the case of a projection optical system, the pixels of the display element can be effectively projected.

[0 1 4 7]

More preferably, at least one of the rear first group first reflective surface 2 2 and the rear first group second reflective surface 2 3 is formed by rotating a line segment of an arbitrary shape having no symmetry plane around the central axis 2. It is important to configure it with a rotationally symmetric extended free-form surface that is formed. [0 1 4 8]

When an optical system is configured with a decentered optical system, decentration aberrations always occur. The occurrence of this decentration aberration can be reduced or corrected to be small.

[0 1 4 9]

More preferably, it is a line segment having an arbitrary shape including an odd-order term.

[0 1 5 0]

This odd-order term makes it possible to correct the distortion of the peripheral part of the screen in the peripheral optical path A and the inclination of the image plane.

[0 1 5 1]

Furthermore, the rear first group first reflecting surface 2 2 is configured so that light rays having a wide angle of view are reflected by total reflection, and the incident angle at which the rear first group first reflecting surface 2 2 is not totally reflected near the center of the angle of view. It is preferable to apply a reflective coating 4a to the center of the rear first group first reflecting surface 22 so as to reflect the light beam. As a result, it is possible to capture an image of the center of the angle of view. Furthermore, since the rear part of the first group 1st reflecting surface 2 2 is totally reflected, it is desirable that this part is not subjected to reflection coating. As a result, the central beam is not prevented from exiting the optical system.

[0 1 5 2]

Further, it is preferable that the rear first group first transmission surface 21 and the rear first group second reflection surface 23 be disposed close to the object side of the rear first group transmission medium Lb.

[0 1 5 3]

This configuration is necessary for shortening the overall length while increasing the optical path length of the optical system, and it is possible to reduce the outer diameter of the optical system while increasing the Z-shaped folded optical path. In addition, it is less likely that the rear first group second reflecting surface 23 interferes with the luminous flux from the object, and an optical system with a wide angle of view can be configured.

[0 1 5 4]

In addition, the rear 1 group first reflective surface 2 2 and the rear 1 group second transparent surface 2 4 It is preferable to dispose the light medium Lb close to the image plane 5 side.

[0 1 5 5]

Similar to the above configuration, this configuration is also necessary for shortening the overall length while taking a longer optical system optical path length, and reducing the outer diameter of the optical system while taking a longer Z-shaped folded optical path. Is possible. In addition, it becomes less likely that the rear first group first reflecting surface 22 2 interferes with the light beam emitted from the optical system and traveling toward the image plane, and an annular imaging area can be widened.

[0 1 5 6]

Further, it is desirable that the rear first group second reflecting surface 23 be provided with a reflective coating 4 b in the peripheral portion, and the central portion is provided with the rear first group first transmitting surface 21 or the opening S. It is desirable not to.

[0 1 5 7]

More preferably, the rear first group first reflecting surface 2 2 and the rear first group second transmitting surface 2 4 are preferably configured in the same place and in the same shape. With this configuration, it is possible to partially use total reflection for the rear first group first reflecting surface 22, and a wide angle of view of the optical system can be obtained.

[0 1 5 8]

More preferably, the rear first group first transmitting surface 2 1 and the rear first group second reflecting surface 2 3 are preferably configured in the same place and in the same shape. This configuration improves workability.

[0 1 5 9]

The front group G f has a front group transparent medium L f having a rotationally symmetric refractive index greater than 1 around the central axis 2, and the front group transparent medium L f has the first group first transmission in the order of the optical path. Surface 1 1, front group first reflective surface 1 1 and front group first reflective surface 1 2 disposed on the opposite side of image plane 5 across front axis 1 1 and central axis 2, and front group first reflective surface 1 2 The front group second reflecting surface 1 3 disposed on the same side of the central axis 2 as the front group first reflecting surface 1 2 and the opposite side of the image surface 5 from the front group first reflecting surface 1 2, and the image surface 5 from the front group second reflecting surface 1 3 The front group second transmission surface 14 arranged on the side, and enters the front group transparent medium L f. The incident light beam enters the front group transparent medium L f through the front group first transmission surface 11 in the order of forward ray tracing, and is reflected by the front group first reflection surface 1 2 to the opposite side to the image surface 5. Therefore, an optical path reflected from the front group second reflecting surface 13 to the image surface 5 side and going out from the front group transparent medium L f to the image surface 5 side through the front group second transmitting surface 14 can be formed. preferable.

[0 1 6 0]

The front group G f has a front group transparent medium L f having a rotationally symmetric refractive index greater than 1 around the central axis 2, and the front group transparent medium L f has the first group first transmission in the order of the optical path. Surface 1 1, front group first reflective surface 1 1 and front group first reflective surface 1 2 disposed on the opposite side of image plane 5 across front axis 1 1 and central axis 2, and front group first reflective surface 1 2 The front group second reflecting surface 1 3 disposed on the opposite side of the central axis 2 from the front group first reflecting surface 1 2 and opposite to the image surface 5 and the image surface 5 from the front group second reflecting surface 1 3 The light beam incident on the front group transparent medium L f passes through the front group first transmission surface 1 1 in the order of forward ray tracing. It enters the transparent medium L f, is reflected by the front group first reflective surface 1 2 on the side opposite to the image surface 5, is reflected by the front group second reflective surface 1 3 on the image surface 5 side, and is Construct an optical path that goes out from the front group transparent medium L f to the image plane 5 side through the transmission plane 14 Is preferred.

[0 1 6 1]

The front group G f has a front group transparent medium L f having a rotationally symmetric refractive index greater than 1 around the central axis 2, and the front group transparent medium L is arranged in the order of the optical path in the order of the optical path. 1 1 and front group first reflecting surface 1 1 and front group first reflecting surface 1 2 disposed on the opposite side of image plane 5 on the opposite side of center axis 2 and front group first reflecting surface 1 2 The light beam incident on the front group transparent medium L f passes through the front group first transmission surface 1 1 in the order of forward ray tracing. Then, the light enters the front group transparent medium L f, is reflected to the image surface side by the front group first reflection surface 12, passes through the front group second transmission surface 14, and then exits from the front group transparent medium L f to the image surface 5 side. It is preferable to construct an optical path that goes out to. [0 1 6 2]

It is desirable to satisfy the following condition: 0.5 <D / (2 X 1 max) <1 0 · · · (1)

[0 1 6 3]

In conditional expression (1), when the lower limit is exceeded, the telecentricity deteriorates, and in particular, when using an image sensor such as C CD, the amount of peripheral light is insufficient. If the upper limit is exceeded, the outer diameter of the optical system becomes too large and the optical system becomes large.

[0 1 6 4]

[0 1 6 5]

[0 1 6 6]

Also, when the curvature of the rear first group first reflective surface 2 2 is R 1 and the curvature of the rear first group second reflective surface 2 3 is R 2,

0.2 <R 1 / R 2 <5 (3) It is desirable to satisfy the following condition.

[0 1 6 7]

Conditional expression (3) regulates the ratio of the power of the two reflecting surfaces. If the lower limit is exceeded, the radius of curvature of the rear first group, first reflecting surface 2 2 becomes smaller, and the rear first group first 2 Reflective surface 2 Compared with the positive power of 3 Rear 1st group 1st reflective surface 2 The negative power of 2 increases and the total length of the optical system cannot be shortened. When the upper limit is exceeded, the curvature of the rear first group second reflecting surface 23 becomes smaller, the positive power of the rear first group second reflecting surface 23 becomes too large, and a large curvature of field on the object side occurs.

[0 1 6 8]

Furthermore, when the curvature of the rear first group first reflective surface 2 2 is R 1 and the curvature of the rear first group second reflective surface 2 3 is R 2,

It is desirable to satisfy the following condition: 0.5 <R 1 / R 2 <2 (3) '

[0 1 6 9]

It should be noted that the surfaces constituted by spherical surfaces in all the embodiments can be constituted by aspheric surfaces. Further, the parallel plane on the image side is for protecting the image sensor and may be omitted.

[0 1 7 0]

Examples 6 to 10 of the optical system of the present invention will be described below. The configuration parameters of these optical systems will be described later.

[0 1 7 1]

In forward ray tracking, for example, as shown in Fig.13, the coordinate system uses the point where the diaphragm surface S intersects the central axis 2 as the origin 〇 of the decentered optical surface, and the direction perpendicular to the central axis 2 as the Y-axis direction. The inside of the paper in Fig. 13 is the Y-Z plane. The direction opposite to the image plane 5 in FIG. 13 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. Since the direction of the Z axis differs in each embodiment, it follows the arrow Z in the figure corresponding to each embodiment.

[0 1 7 2]

For the eccentric surface, the amount of eccentricity from the origin 0 of the optical system 1 in the coordinate system in which the surface is defined (X, Y, and Z are X, Y, and Z, respectively) and the optical system X-axis, Y-axis, Z-axis The tilt angles (α, β, r)) of the coordinate system defining each plane centered on each are given. In that case, the positive of a and | 6 means counterclockwise rotation with respect to the positive direction of each axis, and the positive of a means clockwise rotation with respect to the positive direction of the Z axis. Note that the rotation of a, β, and a on the center axis of the surface is performed by rotating the coordinate system defining each surface a counterclockwise around the X axis of the coordinate system defined at the origin of the optical system. Next, rotate the new coordinate system around the Y axis by j6 counterclockwise rotation, and then rotate it around the Z axis of another rotated new coordinate system clockwise. It is.

[0 1 7 3]

In addition, 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, and in addition, the curvature of the surface The radius, the refractive index of the medium, and the Abbe number are given according to conventional methods.

[0 1 7 4]

In addition, the term for an aspherical surface for which no data is described in the constituent parameters described later is 0. Refractive index and Abbe number are shown for d-line (wavelength 5 8 7. 56 6 nm). The unit of length is mm. The eccentricity of each surface is expressed by the amount of eccentricity from the reference surface as described above.

[0 1 7 5]

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 ]

+ a Y ⁴ + b Y ⁶ + c Y ⁸ + d Y ¹⁰ +-

• · · (a) where Z is the axis and Y is perpendicular to the axis. Where R is the paraxial radius of curvature, k is the conic constant, a, b, c, d, ... are the 4th, 6th, 8th, and 10th order aspherical coefficients, respectively. The Z axis in this definition is the axis of the rotationally symmetric aspheric surface.

[0 1 7 6] An extended rotation free-form surface is a rotationally symmetric surface given by the following definition.

[0 1 7 7]

First, as shown in Fig. 2, the following curve (b) passing through the origin on the Y_Z coordinate plane is determined.

[0 1 7 8]

Z = (Y ² / RY) / [1 + {1-(C, + 1) Y ² / RY ² } ^1/2 ] + C ₂ Y + C 3 Y ² + C ₄ Y ³ + C ₅ Y + C ₆ Y ⁵ + C ₇ Y ⁶

+ · · · · + C ₂₁ Y ² . + · · · · + C _{n + 1} Y "+ · · · ·

• · · (b)

[0 1 7 9]

Next, a curve F (Y) obtained by rotating the curve (b) in the positive direction of the X axis and turning it counterclockwise is defined as an angle Θ. This curve F (Y) also passes through the origin on the Y-Z coordinate plane.

[0 1 8 0]

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

[0 1 8 1]

[0 1 8 2]

[0 1 8 3]

Where RY is the radius of curvature of the spherical term in the Y-Z cross section, is the conic constant, C ₂ , C ₃ , C ₄ , C ₅ … are the first, second, third, fourth, etc. aspheric surfaces, respectively. It is a coefficient.

[0 1 8 4] Note that the conical surface with the Z axis as the central axis is given as one of the extended rotation free-form surfaces, and RY = ∞, C,, C ₂ , C 3, C ₄ , C ₅ , "· = 0 and Θ =

(Inclination angle of conical surface), R = (X — Radius of the bottom surface in the Z plane).

[0 1 8 5]

A sectional view taken along the central axis 2 of the optical system 1 of Example 6 is shown in FIG. In addition, FIG. 15 shows a lateral aberration diagram of the entire optical system of this example. In this transverse aberration diagram, the angle shown in the center indicates (horizontal angle of view, vertical angle of view), and Y direction (meridional direction) and X direction (sagittal direction) at that angle of view. The lateral aberration is shown. Note that a negative field angle means a clockwise angle in the Y-axis positive direction for the horizontal field angle, and a clockwise angle in the X-axis positive direction for the vertical field angle. same as below.

[0 1 8 6]

In this example, an extended rotation is used in which the transmission surface and the reflection surface of the rear group transparent medium L b having a refractive index larger than 1 concentrically with the central axis 2 of the optical system 1 are partially shared in the optical path. This is an example in which a free-form surface is formed, and a front group reflector R f is arranged in front of the rear group transparent medium L b.

[0 1 8 7]

[0 1 8 8]

The front group G f consists of a front group reflector R f that is rotationally symmetric about the central axis 2. The front group reflector R f has a front group first reflecting surface 12 that is convex on the image surface 5 side, which is an aspherical surface.

[0 1 8 9]

The rear group 1 G b 1 is composed of a rear group 1 transparent medium L b whose refractive index rotationally symmetric about the central axis 2 is greater than 1. Rear Group 1 transparent media L b is on the central axis 2 The rear 1st group 1st transmission surface 2 1 and the rear 1st group 1st transmission surface 2 1 are made of aspherical surfaces with the concave surface facing the image surface side. The rear 1st group 1st reflecting surface 2 2 and the rear 1st group 1st reflecting surface 2 2 made of an extended rotation free-form surface with negative power with the concave surface facing the image surface side Reflective coating 4b, rear 1st group 2nd reflective surface 2 3 consisting of aspherical surface with positive power with concave surface facing image side, and rear 1st group 2nd reflective surface 2 3 And a rear first group second transmission surface 24 consisting of an extended rotation free-form surface having a negative power with the concave surface facing the image surface side and disposed on the surface 5 side. Rear 1st group 1st transmission surface 2 1 and Rear 1st group 2nd reflection surface 2 3 have the same position and same shape, Rear 1st group 1st reflection surface 2 2 and Rear 1st group 2nd transmission surface 2 4 It consists of the same shape at the same position.

[0 1 9 0]

The optical system 1 forms the optical path A. In the optical path A, the light beam incident from the object surface 3 of the optical system 1 is between the front group first reflecting surface 1 2 of the front group reflector R f and between the front group reflector R f and the rear group 1 transparent medium L b. Then, after passing through the aperture S arranged coaxially with the central axis 2, it enters the rear group 1 transparent medium Lb. Rear 1st group transparent medium L b enters after 1st group 1st transmission surface 2 1, rear 1st group 1st reflection surface 2 2, partly reflective coating 4a, partly total reflection image surface 5 Is reflected to the image surface 5 side by the reflective coating 4b at the rear 1st group 2nd reflecting surface 23, after passing through the 1st group 2nd transmitting surface 24 and the rear 1st group transparent medium Lb. It has an approximately Z-shaped optical path that goes out. Thereafter, an image is formed in an annular shape at a predetermined position in the radial direction that deviates from the center axis 2 force of the image plane 5.

[0 1 9 1]

The specification of this Example 6 is

Angle of view of the entire system 60.00 ° X 360 °

Rear group angle of view 28.59 °-64.75 °

Rear pupil entrance pupil diameter φ Ι. ΟΟππϋ

Φ 2. OOmn! ~ Φ 3.74mm It is.

[0 1 9 2]

A cross-sectional view taken along the central axis 2 of the optical system 1 of Example 7 is shown in FIG. In addition, FIG. 17 shows a lateral aberration diagram of the entire optical system of this example.

[0 1 9 3]

In this embodiment, the refractive index that is rotationally symmetric with respect to the central axis 2 of the optical system 1 is larger than 1, and then the transmission surface and the reflection surface of the first group of transparent media Lb are partially shared in the optical path. This is an example in which the front group transparent medium L f is arranged as the front group G f of the first group transparent medium L b after being composed of an extended rotation free-form surface.

[0 1 9 4]

The optical system 1 includes a front group G f, a rear group G b, and an aperture S arranged coaxially with the central axis 2 between the front group G f and the rear group G b, and the rear group G b It consists of rear 1 group G b 1 and rear 2 group G b 2.

[0 1 9 5]

The front group G f is composed of a front group transparent medium L f whose refractive index is rotationally symmetric around the central axis 2 and greater than 1. The front group transparent medium L is made of a resin or the like having a rotationally symmetric refractive index greater than 1 around the central axis 2, and the front group first transmitting surface 1 1 formed of an extended rotation free-form surface by incidence of a light beam from a distance. Are arranged on the opposite side of the front group first transmission surface 1 1 and the central axis 2 from the front group first transmission surface 11 1 to the image plane 5 side, and are incident from the front group first transmission surface 11. Front group first reflecting surface 1 2 consisting of an extended rotation free-form surface with the incident light beam, and front group first reflecting surface 12 on the same side with respect to front group first reflecting surface 1 2 and central axis 2 Image surface from front group first reflecting surface 1 2 5 facing the front group second reflecting surface 1 3 consisting of an extended rotation free-form surface and the rear group G b. And a front group second transparent surface 14 made of a spherical surface, into which the light beam reflected by the front group second reflective surface 13 is incident.

[0 1 9 6]

Rear group 1 G b 1 has a rotationally symmetric refractive index greater than 1 around the central axis 2 After 1 group of transparent media Lb. Rear 1st group transparent medium Lb is a rear 1st group 1st transmission surface 2 1 consisting of a spherical surface with the concave surface facing the image surface side on the central axis 2 and the rear 1st group 1st transmission surface 2 1 on the image side Partly reflective coating

4a and the rear 1st group 1st reflecting surface 2 2 consisting of an extended rotation free-form surface with negative power with the concave surface facing the image surface side, and the back 1st group 1st reflecting surface 2 2

The rear 1st group 2nd reflective surface 2 3 and the rear 1st group 2nd reflective surface 2 are composed of a spherical surface with a positive power facing the concave surface toward the image surface side. And a rear first group _second transmission surface ₂ 4, which is composed of an extended rotation free-form surface having a negative power with the concave surface facing the image surface side. Rear 1st group 1st transmission surface 2 1 and rear 1st group 2nd reflection surface 2 3 have the same position and the same shape, Rear 1st group 1st reflection surface 2 2 and Rear 1st group 2nd transmission surface 2 4 are the same It consists of the same shape.

[0 1 9 7]

The rear 2 group G b 2 is composed of the rear 2 group cover glass C b 2 whose refractive index rotationally symmetric around the central axis 2 is greater than 1. Rear 2nd group cover glass Cb2 consists of parallel flat plate, rear 2nd group 1st transmission surface 3 1 and rear 2nd group 1st transmission surface 3 1 formed on the image side with respect to rear 2nd group 1st transmission surface 3 1 Surface 3 and 2.

[0 1 9 8]

The optical system 1 forms the optical path A. The light beam incident from the object plane 3 of the optical system 1 passes through the front group first transmission surface 11 of the front group transparent medium L f, crosses the central axis 2, and the front side opposite to the front group first transmission surface 1 1. Reflected away from the rear group G b by the first group reflecting surface 1 2 and positioned on the same side of the front group first reflecting surface 1 2 and the central axis 2 and further away from the rear group G b Then, the light is reflected again in the rear group Gb direction by the front second group reflecting surface 1 3 and exits from the front group transparent medium L f through the front group second transmitting surface 1 4 on the exit surface.

[0 1 9 9]

Thereafter, the light enters the rear first group transparent medium L b through the opening S arranged coaxially with the central axis 2 between the front group transparent medium L f and the rear first group transparent medium L b. After 1 In the group transparent medium Lb, it enters after the first group first transmission surface 2 1, and after the first group first reflection surface 2 2, a part is reflective coating 4 a and a part is totally opposite to the image surface 5 due to total reflection. Reflected to the rear side, reflected back to the image surface 5 side by the reflective coating 4b at the first group 2nd reflecting surface 23, and then passed through the rear 1st group 2nd transmitting surface 24 and outside the rear 1st group transparent medium Lb It has an approximately Z-shaped optical path that goes out to. After that, the rear 2 group force bar glass Cb 2 passes through the rear 2 group 1st transmission surface 3 1 and the rear 2 group 2nd transmission surface 3 2 to a predetermined radial position away from the central axis 2 of the image surface 5. Form a circle.

[0 2 0 0]

The specification of this Example 7 is

Angle of view of entire system 50.00 ° X 360 °

Rear group angle of view 25.22 ° to 61.94 °

Entrance pupil diameter Φ 1.00 dragon

The size of the image Φ 3.87mn! ~ Φ 7.84mm

It is.

[0 2 0 1]

A sectional view taken along the central axis 2 of the optical system 1 of Example 8 is shown in FIG. In addition, FIG. 19 shows a lateral aberration diagram of the entire optical system of this example.

[0 2 0 2]

In this example, an extended rotation is used in which the transmission surface and the reflection surface of the rear group transparent medium Lb having a refractive index larger than 1 concentric with the central axis 2 of the optical system 1 are partially shared in the optical path. This is an example in which a front group transparent medium L f is arranged as a front group G f of the rear group transparent medium L b, which is composed of a free-form surface.

[0 2 0 3]

The optical system 1 is composed of a front group G f, a rear group G b, and an aperture S arranged coaxially with the central axis 2 between the front group G f and the rear group G b, and the rear group G b is It consists of the first group G 1 and the second group G 2.

[0 2 0 4] The front group G f is composed of a front group transparent medium L f whose refractive index is rotationally symmetric around the central axis 2 and greater than 1. The front group transparent medium L is made of a resin or the like having a rotationally symmetric refractive index greater than 1 around the central axis 2, and the front group first transmitting surface 1 1 formed of an extended rotation free-form surface by incidence of a light beam from a distance. The front group first transmission surface 1 1 and the central axis 2 are placed on the opposite side of the front group.1 Transmission surface 1 1 is located on the image plane 5 side from the front group first transmission surface 1 1 The front group first reflective surface 1 2 made of an extended rotation free-form surface with the incident luminous flux incident, and the front group first reflective surface 1 2 on the opposite side of the front group first reflective surface 1 2 and the central axis 1 from the front group first reflective surface 1 2 The front group second reflecting surface 1 3 made of an extended rotation free-form surface and incident on the side opposite to the surface 5 and reflected by the front group first reflecting surface 12 and the rear group G on the central axis 2 The front group second transmission surface 1 4 is located on the image plane 5 side of the front group second reflection surface 1 3 and faces the b, and is made of a spherical surface by the incident light beam reflected by the front group second reflection surface 1 3. And consist of

[0 2 0 5]

The rear group 1 G b 1 is composed of a rear group 1 transparent medium L b whose refractive index rotationally symmetric about the central axis 2 is greater than 1. Rear 1st group transparent medium Lb is a rear 1st group 1st transmission surface 2 1 consisting of a spherical surface with the concave surface facing the image surface side on the central axis 2 and the rear 1st group 1st transmission surface 2 1 on the image side 1st reflecting surface 2 2 consisting of an extended rotation free-form surface having a negative power with a concave surface facing the image surface side, and a first reflecting surface 2 2 It is located on the opposite side of the image plane 5 with respect to the reflection surface 22, is reflectively coated 4 b, and consists of a spherical surface with a positive power facing the concave surface toward the image surface side. Rear 1st group 2nd reflective surface 2 3 Rear surface 1st group 2nd transmissive surface 2 4 which is arranged on the image surface 5 side from the 2nd reflective surface 2 3 and which consists of an extended rotation free-form surface having negative power with the concave surface facing the image surface side, Have. Rear 1st group 1st transmission surface 2 1 and rear 1st group 2nd reflection surface 2 3 have the same position and the same shape, Rear 1st group 1st reflection surface 2 2 and Rear 1st group 2nd transmission surface 2 4 are the same It consists of the same shape.

[0 2 0 6] The rear 2nd group G b 2 is composed of the rear 2nd group cover glass Cb 2 whose refractive index rotationally symmetric about the central axis 2 is larger than 1. Rear 2nd group cover glass Cb2 consists of parallel flat plate, rear 2nd group 1st transmission surface 3 1 and rear 2nd group 1st transmission surface 3 1 formed on the image side with respect to rear 2nd group 1st transmission surface 3 1 Surface 3 2.

[0 2 0 7]

The optical system 1 forms the optical path A. In the optical path A, the light beam incident from the object surface 3 of the optical system 1 enters the front group transparent medium L f through the front group first transmission surface 1 1, crosses the central axis 2, and the front group first transmission surface 1. Front group first reflective surface 1 opposite to 1 is reflected from the rear group G b away from the rear group G b by the opposite side to the image surface 5 and opposite to the front group first reflective surface 1 2 and the central axis 2 Is reflected to the image plane 5 side by the front second reflecting surface 1 3 located on the side farther from the rear group Gb, and is transparent through the front second transmitting surface 14 of the exit surface. Get out of medium L f.

[0 2 0 8]

After that, it passes through the opening S arranged coaxially with the central axis 2 between the front group transparent medium Lf and the rear group 1 transparent medium Lb, and enters the rear group 1 transparent medium Lb. Rear 1st group transparent medium L b enters through rear 1st group 1st transmission surface 2 1, rear 1st group 1st reflection surface 2 2, part is reflective coating 4a, other part is total reflection, image surface 5 Reflected to the image surface 5 side by the reflective coating 4b at the rear 1st group 2nd reflecting surface 2 3 after passing through the 1st group 2nd transmitting surface 2 4 after the 1st group transparent medium Lb It has an approximately Z-shaped optical path that goes out. Then, the rear group 2 cover glass Cb 2 passes through the rear group 2 first transmitting surface 3 1 and the rear group 2 second transmitting surface 3 2, and is circled at a predetermined radial position away from the central axis 2 of the image surface 5. Form an image in a ring.

[0 2 0 9]

The specification of this Example 8 is

Angle of view of the entire system 80.00 ° X 360 °

Rear group angle of view 37. 93 ° to 58. 17 °

Entrance pupil diameter ψ 1.00 mm Image size φ 4.60mn! ~ Ψ 7.20mm

It is.

[0 2 1 0]

A cross-sectional view taken along the central axis 2 of the optical system 1 of Example 9 is shown in FIG. In addition, Fig. 21 shows a lateral aberration diagram of the entire optical system of this example.

[0 2 1 1]-In this embodiment, the transmission surface and the reflection surface of the rear group transparent medium Lb having a refractive index larger than 1 concentrically symmetric with respect to the central axis 2 of the optical system 1 are aligned in the optical path. This is an example in which the front group transparent medium L f is arranged as the front group G f of the rear group transparent medium L b.

[0 2 1 2]

[0 2 1 3]

The front group G f is composed of a front group transparent medium L f whose refractive index is rotationally symmetric around the central axis 2 and greater than 1. The front group transparent medium L f is made of a resin or the like having a rotationally symmetric refractive index greater than 1 around the central axis 2, and the front group first transmitting surface 1 formed of an extended rotation free-form surface by incidence of a light beam from a distance. 1 and the front group first transmission surface 1 1 and the central axis 2 on the opposite side, the front group first transmission surface 1 1 is disposed on the opposite side of the image plane 5 from the front group first transmission surface 1 1 The front group first reflective surface 1 2 consisting of an extended rotation free-form surface with the incident light beam from the front and the rear group G b on the central axis 2 on the central axis 2 from the front group first reflective surface 1 2 and the image plane 5 And a front group second transmission surface 14 formed of a spherical surface, on which the light beam reflected by the front group first reflection surface 12 2 is incident.

[0 2 1 4]

The rear group G 1 is composed of a rear group 1 transparent medium L b having a rotationally symmetric refractive index greater than 1 around the central axis 2. Rear 1st group transparent medium Lb consists of a rear 1st group 1st transmission surface 2 1 consisting of a spherical surface with the concave surface facing the image surface side on the central axis 2 and the 1st rear group 1st 1 Reflective surface 2 1 formed on the image side, partially coated with reflection 4a, and made up of an extended rotation free-form surface with negative power with the concave surface facing the image surface. It is placed on the opposite side of the image surface 5 with respect to the surface 2 2 and the rear first group first reflective surface 2 2, and has a positive power with a part of the reflective coating 4 b and the concave surface facing the image surface side A rear 1st group 2nd reflecting surface 2 3 consisting of a spherical surface, and an extended rotation free-form surface with negative power with the concave surface facing the image surface side, placed on the image surface 5 side from the rear 1st group 2nd reflecting surface 2 3 After that, it has 1st group 2nd transmission surface 24. Rear group 1 first transmission surface 2 1 and rear group 1 second reflection surface 2 3 have the same shape at the same position. Rear group 1 first reflection surface 2 2 and rear group 1 second transmission surface 2 4 It consists of the same shape at the same position.

[0 2 1 5]

The optical system 1 forms the optical path A. In the optical path A, the light beam incident from the object surface 3 of the optical system 1 enters the front group transparent medium L f through the front group first transmission surface 1 1, crosses the central axis 2, and the front group first transmission surface 1. Front group first reflective surface 1 opposite to 1 Reflected downward toward the rear group G b toward the rear group G b toward the image surface 5 side, and through the front group second transmission surface 14 of the projection surface, the front group transparent medium L f Go out from.

[0 2 1 6]

After that, it passes through the opening S arranged coaxially with the central axis 2 between the front group transparent medium Lf and the rear group 1 transparent medium Lb, and enters the rear group 1 transparent medium Lb. Rear 1st group transparent medium L b enters through rear 1st group 1st transmission surface 2 1, rear 1st group 1st reflection surface 2 2, part is reflective coating 4a, other part is total reflection, image surface 5 Reflected to the image surface 5 side by the reflective coating 4b at the rear 1st group 2nd reflecting surface 2 3 after passing through the 1st group 2nd transmitting surface 2 4 after the 1st group transparent medium Lb It has an approximately Z-shaped optical path that goes out. Thereafter, an image is formed in an annular shape at a predetermined position in the radial direction deviating from the central axis 2 of the image plane 5.

[0 2 1 7]

The specification of this Example 9 is

Angle of view of the entire system 40.00 ° X 360 ° Rear group angle of view 24.45 °-58.38 °

Rear pupil entrance pupil diameter (ί> 1.00mm

Image size φ 3.58mE! ~ Φ 7.03mm

It is.

[0 2 1 8]

A sectional view taken along the central axis 2 of the optical system 1 of Example 10 is shown in FIG. Also, the lateral aberration diagram of the entire optical system of this example is shown in FIG.

[0 2 1 9]

In this embodiment, the transmission surface and the reflection surface of the rear group transparent medium Lb having a refractive index larger than 1 concentric with the central axis 2 of the optical system 1 are partially used in the optical path. This is an example in which the front group transparent medium L f is arranged in front of the rear group transparent medium L b.

[0 2 2 0]

[0 2 2 1]

The front group G f is composed of a front group transparent medium L f whose refractive index is rotationally symmetric around the central axis 2 and greater than 1. The front group transparent medium L f is made of a resin or the like having a rotationally symmetric refractive index greater than 1 around the central axis 1, and the front group first transmitting surface 1 formed of an extended rotation free-form surface by the incident light beam 2 from a distance. 1 and the front group first transmitting surface 1 1 and the central axis 1 on the opposite side, the front group first transmitting surface 1 1 is disposed on the opposite side of the image surface 5 from the front group first transmitting surface 1 Front group first reflective surface 1 2 consisting of an extended rotation free-form surface with the incident light beam from 1 and front group first reflective surface 1 2 and front group first reflective surface 1 on the opposite side across central axis 1 2 is located on the opposite side of the image plane 5 from the front surface, and the light beam reflected by the front group first reflective surface 1 2 is incident on the front group second reflective surface 1 3 consisting of an extended rotation free-form surface and the rear group G b. Therefore, the light beam reflected on the second reflecting surface 13 of the front group is incident on the second reflecting surface 1 2 and the central axis 2 on the image plane 5 side from the second reflecting surface 1 3 of the front group. Spherical surface And the front group second transmitting surface 14.

[0 2 2 2]

The rear group 1 G b 1 is composed of a rear group 1 transparent medium L b whose refractive index rotationally symmetric about the central axis 2 is greater than 1. Rear 1st group transparent medium Lb is a rear 1st group 1st transmission surface 2 1 consisting of a spherical surface with the concave surface facing the image surface side on the central axis 2 and the rear 1st group 1st transmission surface 2 1 on the image side With a negative power with a concave surface facing the image surface side and a rear first group first reflective surface 2 2 and a rear first group first reflective surface 2 2 The rear 1st group 2nd reflective surface 2 3 and the rear 1st group 2nd reflective that are arranged on the opposite side of the image surface 5 and have a positive power with the concave surface facing the image surface 4b It is arranged on the image surface 5 side from the surface 23 and has a rear first group second transmission surface 24 having negative power with the concave surface facing the image surface side. Rear group 1 first transmission surface 2 1 and rear group 1 second reflection surface 2 3 have the same shape at the same position. Rear group 1 first reflection surface 2 2 and rear group 1 second transmission surface 2 4 It consists of the same shape at the same position.

[0 2 2 3]

The optical system 1 forms the optical path A. In the optical path A, the light beam incident from the object surface 3 of the optical system 1 enters the front group transparent medium L f via the front group first transmission surface 1 1, crosses the central axis 2, and the front group first transmission surface 1. Front group first reflective surface 1 opposite to 1 is reflected from the rear group G b away from the rear group G b by the opposite side to the image surface 5 and opposite to the front group first reflective surface 1 2 and the central axis 2 Is reflected to the image plane 5 side by the front group second reflecting surface 1 3 located on the side away from the rear group Gb, and passes through the front group second transmitting surface 1 4 of the projecting surface and passes through the front group transparent medium L. Get out of f.

[0 2 2 4]

After that, it passes through the opening S arranged coaxially with the central axis 2 between the front group transparent medium Lf and the rear group 1 transparent medium Lb, and enters the rear group 1 transparent medium Lb. Rear 1st group transparent medium Lb enters through rear 1st group 1st transmission surface 2 1, rear 1st group 1st reflection surface 2 2 partly reflective coating 4a, partly due to total reflection image surface 5 Reflected on the side opposite to the back, and the back 1st group 2nd reflecting surface 2 3 Reflective coating 4 b Reflected toward the image plane 5 by b, and passes through rear group 1 second transmission surface 24 and rear group 1 transparent medium L. It has a substantially Z-shaped optical path exiting from b. Thereafter, an image is formed in an annular shape at a predetermined position in the radial direction deviating from the central axis 2 of the image plane 5.

[0 2 2 5]

The specification of this Example 10 is

Angle of view of the entire system 60.00. X 360 °

Rear group angle of view 24.17 ° to 55

Rear group entrance pupil diameter Φ 1.OOfflm

Image size Φ 3.84mm to φ 7.53mm

It is.

[0 2 2 6]

The maximum image height is I max (mm), the minimum image height is I min (mm), the maximum field angle of the rear group G r is Θ max (degrees), and the minimum field angle of the rear group G r is Θ min (degrees) ), Focal length

F = (I max-I min) / (Θ max-0 min), the outer diameter of the rear group G r is D (mm), and the total length of the rear group G r is L (mm ), Where the curvature of the rear-group first reflecting surface 22 is R1, and the curvature of the rear-group second reflecting surface 23 is R2, Example 6 Example 7 Example 8 Example 9 Example 10

I max 1. 87 3. 92 3. 54 3. 51 3. 77

Θ max 64. 75 61. 94 58. 17 58. 38 55. 75

I min 1. 00 1. 93 2. 30 1. 79 1. 92

Θ min 28. 59 25. 22 37. 93 24. 45 24. 17

F 0. 024 0. 054 0. 061 0. 051 0. 059

D 6.00 10. 80 9. 60 11. 20 11. 60

L 2. 800 '4. 800 4. 400 4. 80 5. 20

D (2X Imax) 1.604 1. 378 1. 356 1. 594 1. 540

L (2x Imax) 0. 749 0. 612 0. 621 0. 683 0. 690

R 1 2. 54 2. 54 9. 11 6. 12 6. 65

R 2 3. 52 3. 52 8. 82 7. 14 7. 80

R 1 / R 2 0. 72 0. 72 1. 03 0. 86 0. 85.

[0 2 2 7] The configuration parameters of Example 6 10 will be described below. In the table below, “RE” indicates a reflective surface.

[0 2 2 8]

Example 6

Surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface oo oo Eccentricity (1)

1 (R E) Aspherical surface [1] 0.00 Eccentricity (2)

2 ∞ (Aperture) 0.00

3 Aspherical surface [2] 0.00 Eccentricity (3) 42.7

4 (R E) E R F S [1] 0.00 Eccentricity (4) 42.7

5 (RE) Aspherical surface [2] 0.00 Eccentricity (3)

42.7

6 E R F S [1] 3.49 Eccentricity (4)

Statue face oo

[0 2 2 9]

In addition, the surface distance to the image surface is the distance from the reference surface (aperture surface).

[0 2 3 0]

E R F S [1]

R Y -2. 54

Θ -16. 68

R -0. 80

C 4 2. 7077E-002

Aspherical [1]

Curvature radius 24.30

k -9.1220E + 000

Aspherical [2]

Radius of curvature -3.52

k 1.4073E-001

Eccentric [1]

X 0.00 Y 0.00

110.00 β 0.00

Eccentric [2]

X 0.00 Υ 0.00 Ζ 4.52

Face image L

Real 2 u o o 47 ° 92356 o 1

Front side 2 2 ((

0. 00 β 0. 00 r 0. 00

Eccentric [3]

X 0. 00 Y 0. 00 z -0. 10

Eccentric [4]

X 0. 00 Y 0. 00 z-1. 74

0. 00 β 0. 00 r 0. 00

3 1]

Example 7

Radius of curvature Surface spacing Eccentricity Refractive index Abbe number οο ∞ Eccentricity (1)

Ε R F S [1] 0. 00 Eccentric (2) 1. 8348 42. 7

R E) E R F S [2] 0. 00 Eccentricity (3) 1. 8348 42. 7 R E) E R F S [3] 0. 00 Eccentricity (4) 1. 8348 42. 7

-18. 83 0. 00 Eccentric (5)

∞ (Aperture) 0.00

8. 08 0. 00 1. 8348 42. 7

R E) E R F S [4] 0.00 Eccentricity (6) 1. 8348 42. 7 R E) 8. 08 0. 00 1. 8348 42. 7

E R F S [4] 5. 72

CO 1. 00 1. 5 163 64. 1

CO 0. 70

CO

3 2]

The surface distance to the 10th surface is the distance from the reference surface (diaphragm surface).

[0 2 3 3]

E R F S [1]

R Y 16. 7 1

Θ 49. 59

R-10. 48

E R F S [2]

R Y -22. 92

Θ 36. 92 [9] Tsutsu

00 • 0 义 00 • 0 SI 00 • 0 Ώ

00 '卜 Z 00 • 0 On 00 • 0 X

[S]

00 • 0 1 00 • 0 00 • 0 ε ε G Z 00 • 0 On 00 • 0 X

[V]

00 • 0 1 00 • 0 00 • 0 Ό 8 'S-Z 00 • 0 on 00 • 0 X

[ε]

00 • 0 1 00 • 0 00 • 0 Ό

• n-Z 00 • 0 input 00 • 0 X

Tsutsu

00 • 0 义 00 Ό 00 • s Ό

"01-Z 00 • 0 input 00 • 0 X

[I]

C00-3C866 1-D

'\-

66. 01 Θ

18 'Ζ A H

C00-aC866 V D

9 ΐ99 'G θ εε' se- input Η d Η a

91 · 8 Η

T0S990 / 800Zdf / X3d 19 88 贿 600Ζ OAV number

Toss

E R F S [1]

R Y-6. 52

Θ 65. 91

R -9. 51

E R F

R Y -17. 99

Θ 51. 78

R 7.06

C 4 -8. 6892E-005

E R F S [3]

R Y 6.10

Θ 36.27 R -7. 96

C 4 — 1. 1833E-004

E R F S [4

R Y 9. 1 1

Θ -7. 46

R 1.52

Eccentric [1]

X 0. 00 Y 0. 00 Ζ -7. 04 45. 00 β 0. 00 r 0. 00 Eccentricity [2]

X 0. 00 Y 0. 00 Z-16. 54 a 0. 00 β 0. 00 r 0. 00 Eccentric [3]

X 0. 00 Υ 0. 00 Z -4. 83 0. 00 β 0. 00 r 0. 00 Eccentricity [4]

X 0. 00 Υ 0. 00 Z-17. 96 0. 00 β 0. 00 r 0. 00 Eccentric [5]

X 0. 00 Υ 0. 00 Z -0. 10 0. 00 β 0. 00 r 0. 00 Eccentricity [6]

X 0. 00 Υ 0. 00 Z 0. 10 0. 00 β 0. 00 r 0. 00 Eccentric [7]

0. 00 Υ 0. 00 Z 3. 36 0. 00 β 0. 00 r 0. 00

Image Γ

O o

Surface 22

Example 9

Surface number Curvature radius Surface spacing Eccentric Refractive index Abbe Object surface ∞ Eccentricity (1)

1 E R F S [1] 0.00 Eccentricity (2) 64. 1

2 (R E) E R F S [2] 0.00 Eccentricity (3) 64.1

3 -10. 32 0.00 Eccentricity (4)

4 ∞ (Aperture) 0. 10

7 -7. 14 0.00 Eccentricity (5) 42.7

8 (R E) E R F S [3] 0.00 Eccentricity (6) 1.8348 42.7

9 (R E) -7. 14. 0.00 Eccentricity (5) 42.7

10 E R F S [3] 10.46 Eccentricity (6)

CO

3 8]

The distance from the image plane is the distance from the reference plane (aperture plane) 3 9]

E R F S [1]

R Y 103. 57

Θ -37.90

R 7.54

E R F S [2]

R Y -15.54

Θ -47.84

R-6.27

C 4 -1. 3391E-005

E R F S [3]

R Y -6. 12

Θ 12. 22

R 1. 28

C 4 -6.8442E-004

Eccentric [1]

X 0.00 Y 0.00 Z 7. 28

90.00 B 0.00 r 0.00

Eccentric [2] X 0.00 Y 0 00 ζ 7.28

0. 00 β 0 00 r 0.00

Eccentric [3]

X 0. 00 Y 0 00 ζ 12.52

0. 00 β 0 00 r 0.00

Eccentric [4]

X 0. 00 Υ 0 00 ζ 0.10

a 0. 00 β 0 00 r 0.00

Eccentric [5]

X 0. 00 Υ 0 00 ζ -0.10

a 0. 00 β 0 00 r 0.00

Eccentric [6]

X 0. 00 Υ 0 00 Ζ -3.21

0.00 β 0.00 0.00

[0 2 4 0]

Example 10

Surface number Curvature radius Surface spacing Refractive index Abbe number Object surface οο οο (1)

1 E R F S [1] 0.00 (2) 1. 8348 42.7

2 (R E) E R F S [2] 0.00 (3) 1. 8348 42.7

3 (R E) E R F S [3] 0.00 (4) 1. 8348 42.7

4 -8. 90 0.00 (5)

5 οο (Aperture) 0.00

6 7. 80 0.00 (6) 1. 8348 42.7

7 (R E) E R F S [4] 0.00 (7) 1. 8348 42.7

8 (R E) 7. 80 0.00 (6) 1. 8348 42.7

9 E R F S [4] 9.17 (7)

Image plane ∞

[0 2 4 1]

Note that the distance from the image plane is the distance from the reference plane (aperture plane).

[0 2 4 2]

E R F S [1〗

RY 23.83 U 'CI- z 00' 0 input 00 Ό X

00 '0 Top oo' o d 00 Ό »'8- Z 00 Ό Enter 00 · 0 X

[ε]

00 '0 up oo' o d 00 · 0 »

SP Z oo 'o Enter 00 0 X

[Z]

00 '0 Top 00 Ό £ 1 00' SCI »

Z8 '6- Z 00 Ό A 00 "0 X

[1]

刚 — 3s · τ PD

Of Ί H -z \-Θ

59 '9 A

[t ^] S Η Ή 3

500-38510 Ί-D ΐΐ • S- H

■ Θ 61 "8 into ¾ [

[ε] S d Η 3

900-3U8S • ί- D

00 Ί H '68 Θ

86 ΌΙ- Enter ¾

[E] s d H a

ε 9- Η

Zl '98 θ

T0S990 / 800Zdf / X3d 99 88 贿 600 Ζ OAV 0. 00 β 0. 00 r 0. 00

Eccentric [5]

X 0. 00 Y 0. 00 ζ-0. 10

a 0. 00 β 0. 00 r 0. 00

Eccentric [6〗

X 0. 00 Υ 0. 00 ζ 0. 10

0; 0. 00 β 0. 00 r 0. 00

Eccentric [7]

X 0. 00 Υ 1.00 ζ 3.5 1

0. 00 β 0. 00 r 0. 00

[0 2 4 3]

FIG. 24 shows an arrangement example of the image and the image sensor of the present embodiment. Figure 24 (a) shows an example using an image sensor with a screen ratio of 16: 9. When the image in the vertical direction is not used, it is preferable to match the size of the image sensor 50 with the left and right positions of the image A 1 in the optical path A. Fig. 24 (b) shows the case where an image sensor 50 with a screen ratio of 4: 3 is used and the image in the vertical direction is not used. FIG. 24 (c) is an example in which an image sensor 50 having a screen ratio of 4: 3 is used, and the size of the image sensor 50 is matched with the image A 1 in the optical path A. In this way, with the arrangement, the entire image A 1 of the optical path A can be captured.

[0 2 4 4]

Hereinafter, as an application example of the optical system 1 of the present invention, a usage example of the photographing optical system 1001 or the projection optical system 100 will be described. FIG. 25 is a diagram for illustrating an example in which the photographing optical system 10 1 according to the present invention is used as a photographing optical system at the distal end of the endoscope. FIG. 25 (a) shows a rigid endoscope 110. This is an example in which an imaging optical system according to the present invention is attached to the tip 110 of a and an image is taken and observed. Figure 25 (b) shows the schematic configuration of the tip. In the panoramic imaging optical system 10 1 according to the present invention, a case having an opening 1 0 6 extending in the circumferential direction around the entrance surface 1 1. A flare stop 10 7 composed of a ring or the like is arranged to prevent the flare light from entering. Fig. 25 (c) shows an image captured on the display device 1 1 4 by attaching the panoramic imaging optical system 1 0 1 according to the present invention to the tip of the flexible electronic endoscope 1 1 3 in the same manner. This is an example in which image processing is performed to correct distortion and display.

[0 2 4 5]

FIG. 26 and FIG. 27 are examples in which the imaging optical system 10 1 according to the present invention is attached to the capsule endoscope 120 and images of 360 ° omnidirectional images are taken and observed. A flare stop 1 0 7 is formed in a casing or the like having an opening 10 6 extending in the circumferential direction around the first transmission surface 1 1 of the front group G f in the optical path A of the photographing optical system 10 1 according to the present invention. This prevents flare light from entering.

[0 2 4 6]

As shown in FIG. 25, FIG. 26, and FIG. 27, by using the photographing optical system 10 1 for the endoscope, the image behind the photographing optical system 1 0 1 can be imaged and observed. Various parts can be imaged and observed from different angles.

[0 2 4 7]

FIG. 28 (a) shows a photographed optical system 1 0 1 according to the present invention attached to the front of an automobile 1 30 as a photographing optical system, and photographed through each photographing optical system 1 0 1 on a display device in a car. FIG. 28 (b) shows an example in which the processed image is subjected to image processing to correct distortion and displayed simultaneously. A plurality of photographic optical systems 1 0 1 according to the present invention are attached as the photographic optical system on the top of the image sensor, and the image captured through each of the photographic optical systems 1 0 1 is applied to a display device in a vehicle to correct distortion by performing image processing. FIG. 5 is a diagram showing an example in which images are displayed simultaneously. In this case, as shown in FIG. 24 (a), it is preferable to match the size of the image sensor 50 to the left and right positions of the image A 1 on the optical path A because the left and right images can be captured widely. [0 2 4 8]

FIG. 29 shows a projection optical system 1 0 2 using a projection optical system 1 0 2 according to the present invention as a projection optical system, displaying a panoramic image on a display element arranged on the image plane 5, and projecting optical system 1 This is an example in which a 360 ° omnidirectional image is projected and displayed on screen 14 1 arranged in 360 ° omnidirectional through 0-2.

[0 2 4 9]

Further, FIG. 30 shows a projection device using the photographing optical system 1 0 1 according to the present invention indoors, with the photographing device 15 1 using the photographing optical system 1 0 1 according to the present invention attached outside the building 15 50. 1 5 1 is arranged and connected so that the image captured by the imaging device 1 51 is sent to the projection device 1 4 0 via the electric wire 1 5 2. In such an arrangement, an outdoor 360 ° omnidirectional subject P is photographed by the photographing device 1 5 1 through the photographing optical system 1 0 1, and the video signal is projected through the electric wire 15 2. This is an example in which the image P ′ of the subject P is projected and displayed on an indoor wall surface etc. through the projection optical system 1 0 2 . Industrial application fields

[0 2 5 0]

In the optical system of the present invention described above, it is possible to obtain a compact optical system with good resolving power with good aberration correction that can observe a wide angle of view or project an image with a wide angle of view with a simple configuration. it can.

Claims

The scope of the claims

[1]

A front group sandwiching at least one reflecting surface; a rear group; and an opening disposed between the front group and the rear group, and rotating around the central axis in a cross section including the central axis In the symmetric optical system, the rear group is disposed on the image plane side of the opening and has a rear group transparent medium having a refractive index larger than 1, and the rear group transparent medium has the central axis in the vicinity of the opening. A rear group first transmission surface disposed above, a rear group first reflection surface disposed closer to the image plane side than the rear group first transmission surface, with a concave surface facing the image plane side, and the rear group first reflection A rear group second reflecting surface that is disposed on the opposite side of the image surface from the surface, with a concave surface facing the image surface side, and a rear group second transmitting surface disposed on the image surface side from the rear group second reflecting surface; And at least one of the rear group first reflective surface and the rear group second reflective surface is formed of a continuous curved surface on a central axis, and the rear group transparent medium The light beam incident on the body passes through the aperture in the order of forward ray tracing, enters the rear group transparent medium through the rear group first transmission surface, and is on the side opposite to the image plane on the rear group first reflection surface. A substantially Z-shaped first optical path that is reflected and reflected to the image plane side by the rear group second reflecting surface and exits from the rear group transparent medium to the image plane side through the rear group second transmitting surface is configured. In addition, at least the rear group first reflecting surface and the rear group second reflecting surface of the first optical path are configured only on one side with respect to the central axis, and an intermediate image is formed in the first optical path. An optical system characterized by being formed in an annular shape on the image plane without being imaged.

[2]

The optical system according to claim 1, wherein the first reflecting surface of the rear group is a spherical surface.

[3]

The rear group first reflective surface is configured to reflect by a total reflection action and a reflective coating, and the reflective coating is formed in the rear group first reflective surface. The optical system according to claim 1, wherein the optical system is provided only in the vicinity of the mandrel.

[ Four ]

2. The optical system according to claim 1, wherein the rear group first transmission surface and the rear group second reflection surface are disposed on an object side of the rear group transparent medium.

[ Five ]

The optical system according to claim 1, wherein the rear group first transmission surface and the rear group second reflection surface have the same shape at the same position.

[6]

2. The optical system according to claim 1, wherein the rear group first reflecting surface and the rear group second transmitting surface are arranged on an image surface side of the rear group transparent medium.

[7]

2. The optical system according to claim 1, wherein the rear group first reflecting surface and the rear group second transmitting surface have the same position and the same shape.

[8]

The front group has a front group transparent medium having a refractive index rotationally symmetric about a central axis greater than 1. The front group transparent medium includes a front group first transmission surface, and the front group first transmission surface. A front group first reflecting surface disposed on the image surface side, a front group second reflecting surface disposed on the opposite side of the image surface from the front group first reflecting surface, and an image from the front group second reflecting surface. A front group second transmission surface disposed on the surface side, and the light beam incident on the front group transparent medium passes through the front group first transmission surface in the order of forward ray tracing, and enters the front group transparent medium. After crossing the central axis, it is reflected to the opposite side to the image plane by the front group first reflection surface, and is reflected to the image plane side by the front group second reflection surface without crossing the central axis. 2. The optical system according to claim 1, wherein an optical path that exits from the front group transparent medium to the image surface side through the front group second transmission surface is configured. .

[9]

The front group has a front group transmission with a refractive index greater than 1 which is rotationally symmetric about the central axis. The front group transparent medium includes a front group first transmission surface, a front group first reflection surface disposed closer to the image plane than the front group first transmission surface, and the front group first reflection A front group second reflecting surface disposed on the opposite side of the image surface from the surface; and a front group second transmitting surface disposed on the image surface side from the front group second reflecting surface; and the front group transparent The light beam incident on the medium enters the front group transparent medium through the front group first transmission surface in the order of forward ray tracing, intersects the central axis, and then is opposite to the image plane at the front group first reflection surface. Is reflected to the side, and again intersects the central axis, then is reflected to the image surface side by the front group second reflecting surface, and exits from the front group transparent medium to the image surface side through the front group second transmitting surface. The optical system according to claim 1, wherein the optical system constitutes an optical path.

[ Ten ]

The front group has a front group transparent medium having a rotational symmetry about a central axis and a refractive index larger than 1, the front group transparent medium includes a front group first transmission surface, and the front group first transmission surface. A front group first reflecting surface disposed on the opposite side of the image surface, and a front group second transmitting surface disposed on the image surface side with respect to the front group first reflecting surface. A light beam incident on the medium enters the front group transparent medium via the front group first transmission surface in the order of forward ray tracing, and intersects the central axis, and then the image plane side on the front group first reflection surface. 2. The optical system according to claim 1, further comprising an optical path that is reflected by the light beam and exits to the image surface side from the front group transparent medium through the front group second transmission surface.

[1 1]

The optical system according to claim 1, wherein the following condition is satisfied: 0.5 <D / (2 X 1 max) <1 0 ··· (1)

[1 2]

When the maximum image height is I max and the distance from the aperture to the image plane is L

0.5 <L / (2 X 1 max) <1 0 (2) The optical system according to claim 1, wherein the following condition is satisfied.

[ 13 ]

Let R 1 be the curvature of the first reflecting surface of the rear group, and R 2 be the curvature of the second reflecting surface of the rear group.

The optical system according to claim 1, wherein the following condition is satisfied.

[ 14 ] ..

An endoscope using the optical system according to claim 1.

[1 5]

A front group including at least one reflecting surface; a rear group; and an opening disposed between the front group and the rear group, and rotating around the central axis in a cross section including the central axis In the symmetric optical system, the rear group is disposed on the image plane side of the opening and has a rear group transparent medium having a refractive index larger than 1, and the rear group transparent medium has the central axis in the vicinity of the opening. A rear group first transmission surface disposed above, a rear group first reflection surface disposed closer to the image plane side than the rear group first transmission surface and having a concave surface facing the image plane side; and the rear group first reflection A rear group second reflecting surface that is disposed on the opposite side of the image surface from the surface, with a concave surface facing the image surface side, and a rear group second transmitting surface disposed on the image surface side from the rear group second reflecting surface; The light beam incident on the rear group transparent medium passes through the opening in the order of forward ray tracing, passes through the rear group first transmission surface, and enters the rear group transparent medium. The rear group first reflecting surface is reflected to the opposite side of the image plane, the rear group second reflecting surface is reflected to the image plane side, and the rear group second transmitting surface is passed through the rear group transparent medium. A substantially Z-shaped first optical path that goes out to the surface side is configured, and at least a portion of the first optical path between the rear group first reflecting surface and the rear group second reflecting surface is in relation to the central axis. Consists of only one side, and without forming an intermediate image in the first optical path, an object point around the central axis intersects the central axis once in the vicinity of the aperture and forms an image on the opposite side And an optical system characterized in that the optical system is formed in an annular shape on the image plane as a whole, and at least one of the rear group reflecting surfaces is constituted by a rotationally symmetric surface that is discontinuous on the central axis. . [1 6]

At least one of the rear surface reflecting surfaces is formed of an extended rotation free-form surface formed by rotating a line segment having an arbitrary shape discontinuous on the central axis around the central axis. The optical system according to claim 15.

[1 7]

At least one of the rear surface reflecting surfaces is composed of an extended rotation free-form surface formed by rotating an arbitrary-shaped line segment including an odd-order term around the central axis. The optical system according to claim 15.

[1 8]

The rear group first reflective surface is configured to reflect by a total reflection action and a reflective coating, and the reflective coating is applied only in the vicinity of the central axis of the rear group first reflective surface. The optical system according to claim 15, characterized in that it is characterized in that:

[1 9]

16. The optical system according to claim 15, wherein the rear group first transmitting surface and the rear group second reflecting surface are disposed on the object side of the rear group transparent medium.

[2 0]

The optical system according to claim 15, wherein the rear group first transmission surface and the rear group second reflection surface have the same shape at the same position.

[twenty one ]

16. The optical system according to claim 15, wherein the rear group first reflecting surface and the rear group second transmitting surface are disposed on the image plane side of the rear group transparent medium.

[twenty two ]

16. The optical system according to claim 15, wherein the rear group first reflecting surface and the rear group second transmitting surface have the same position and the same shape.

[twenty three ]

The front group includes a front group transparent medium having a refractive index rotationally symmetric about a central axis greater than 1. The front group transparent medium includes a front group first transmission surface, and the front group first medium. A front group first reflecting surface disposed on the image surface side from the transmission surface, a front group second reflecting surface disposed on the side opposite to the image surface from the front group first reflecting surface, and the front group second reflecting surface A front group second transmission surface disposed closer to the image plane side, and a light beam incident on the front group transparent medium passes through the front group first transmission surface in the order of forward ray tracing, After entering the medium and intersecting the central axis, it is reflected to the opposite side of the image surface by the front group first reflecting surface, and reflected to the image surface side by the front group second reflecting surface without intersecting the central axis. 16. The optical system according to claim 15, further comprising an optical path that exits from the front group transparent medium to the image surface side through the front group second transmission surface.

[ twenty four ]

The front group has a front group transparent medium having a rotational symmetry about a central axis and a refractive index larger than 1, the front group transparent medium includes a front group first transmission surface, and the front group first transmission surface. A front group first reflecting surface disposed on the image surface side, a front group second reflecting surface disposed on the opposite side of the image surface from the front group first reflecting surface, and an image from the front group second reflecting surface. A front group second transmission surface disposed on the surface side, and the light beam incident on the front group transparent medium passes through the front group first transmission surface in the order of forward ray tracing, and enters the front group transparent medium. After crossing the central axis, it is reflected to the opposite side of the image plane by the front group first reflecting surface, and after crossing the central axis again, it is reflected to the image plane side by the front group second reflecting surface, 16. The optical system according to claim 15, wherein an optical path that exits from the front group transparent medium to the image surface side through the front group second transmission surface is configured.

[ twenty five ]

The front group has a front group transparent medium having a rotational symmetry about a central axis and a refractive index larger than 1, the front group transparent medium includes a front group first transmission surface, and the front group first transmission surface. A front group first reflecting surface disposed on the opposite side of the image surface, and a front group second transmitting surface disposed on the image surface side with respect to the front group first reflecting surface. The light beam incident on the medium enters the front group transparent medium through the front group first transmission surface in the order of forward ray tracing, intersects the central axis, and then the front group first reflection. 16. The optical system according to claim 15, wherein an optical path that is reflected by the surface to the image surface side and exits to the image surface side from the front group transparent medium through the front group second transmission surface is formed. system.

[2 6]

The optical system according to claim 15, wherein the following condition is satisfied: 0.5 <D / (2 X 1 max) <1 0 − − (1)

[2 7]

The optical system according to claim 15, wherein the following condition is satisfied: 0.5 <L / (2 X 1 max) <1 0... (2)

[2 8]

When the curvature of the first reflecting surface of the rear group is R1, and the curvature of the second reflecting surface of the rear group is R2,

16. The optical system according to claim 15, wherein the following condition is satisfied: 0.2 <R 1 / R 2 <5 * (3)

[2 9]

The optical system according to claim 15, wherein the following condition is satisfied: 0.5 <R 1 / R 2 <2 * (3) ′.

[3 0]

An endoscope using the optical system according to claim 15.