WO2009041290A1 - Optical system and endoscope using same - Google Patents

Abstract

An optical system and an endoscope using the same. A first transmissive surface (21), a second reflective surface (22), a second reflective surface (23), and a second transmissive surface (24) are each a spherical surface. A light flux, which will enter a transparent medium (L), forms an almost Z-shaped first optical path (A) by, in forward ray tracing, entering the transparent medium (L) through an opening (S) and the first transmissive surface (21), being reflected to the side opposite to an image surface by the first reflective surface (22), being reflected to the image surface side by the second reflective surface (23), and going out to the image surface side from the transparent medium (L) through the second transmissive surface (24). At least a portion between the first reflective surface (22) and the second reflective surface (23) of the first optical path (A) is formed on only one side of a central axis (2). An image is formed in a ring shape on the image surface without an intermediate image being formed 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. is there.

 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 is an optical system that is rotationally symmetric about the central axis in a cross section including the central axis, wherein the optical system is an aperture disposed on the object side on the central axis. And a transparent medium having a refractive index greater than 1 disposed on the image plane side of the opening, the transparent medium including the first transmission surface disposed on the central axis in the vicinity of the opening, The first reflecting surface is disposed on the image plane side from the first transmission surface and has a concave surface facing the image surface side. The first reflecting surface is disposed on the opposite side of the image surface from the first reflecting surface, and the concave surface is directed to the image surface side. A second reflective surface; and a second transmissive surface disposed on the image plane side with respect to the second reflective surface. The first transmissive surface, the first reflective surface, the second reflective surface, and the second reflective surface. 2 The transmission surface is formed of a curved surface, and the light beam incident on the transparent medium passes through the aperture in the order of forward ray tracing, and the first transmission surface. Through the transparent medium, reflected by the first reflecting surface to the opposite side of the image plane, reflected by the second reflecting surface to the image plane side, and passed through the second transmitting surface from the transparent medium to the image plane. A substantially Z-shaped first optical path going out to the side, and at least a portion of the first optical path between the first reflecting surface and the second reflecting surface is configured on one side with respect to the central axis. The intermediate image is formed in an annular shape on the image plane without forming an intermediate image in the first optical path.

[0 0 0 6]

 Further, the first reflecting surface is configured to be reflected by a total reflection action and a reflection coating, and the reflecting coating is applied only in the vicinity of the central axis of the first reflecting surface. And

 [0 0 0 7]

 The first transmission surface and the second reflection surface are arranged on the object side of the transparent medium.

 [0 0 0 8]

 The first transmission surface and the second reflection surface may have the same shape at the same position.

[0 0 0 9] The first reflection surface and the second transmission surface may be arranged on the image surface side of the transparent medium.

 [0 0 1 0]

 In addition, the first reflection surface and the second transmission surface have the same shape at the same position.

 [0 0 1 1]

 In addition, a third transmission surface is provided in the vicinity of the central axis of the first reflection surface, and a light beam incident on the transparent medium passes through the opening in the order of forward ray tracing, passes through the first transmission surface, and passes through the first transmission surface. A second optical path is formed which enters inside and passes through the third transmission surface and exits from the transmission medium to the image plane side.

 [0 0 1 2]

 In addition, a lens is disposed on the object side and / or the image plane side of the transparent medium.

 [0 0 1 3]

 In addition, the transparent medium is formed by joining a first transparent medium and a second transparent medium having different refractive indexes.

 [0 0 1 4]

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

 It is characterized by satisfying the following condition: 1 D D Z (2 X 1 max) 5 5 (1)

 [0 0 1 5]

 When the maximum image height is Imax and the distance from the aperture to the image plane is Lo,

 1 <Lo / (2 X I max) <3 ··· (2) The condition is satisfied.

 [0 0 1 6]

Also, let R 1 be the curvature of the first reflecting surface and R 2 be the curvature of the second reflecting surface. 0.2 <R 1 / R 2 <3-· · · (3) The condition is satisfied.

 [0 0 1 7]

 The first reflecting surface and the second reflecting surface are each composed of a rotationally symmetric aspherical surface.

 [0 0 1 8]

 The first reflecting surface and the second reflecting surface are spherical surfaces.

 [0 0 1 9]

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

 [0 0 2 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. Brief Description of Drawings

 [0 0 2 1]

 〔Figure 1〕

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

 〔Figure 2〕

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

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

 (Fig. 4)

FIG. 5 is a cross-sectional view taken along the central axis of the optical system of Example 2-1 of the present invention. FIG. 10 is a diagram showing transverse aberration diagrams of the first optical path of the whole optical system of Example 2-1 and 2-2.

 (Fig. 6)

 FIG. 6 is a cross-sectional view taken along the central axis of the optical system of Example 2-2 of the present invention.

 (Fig. 7)

 FIG. 10 is a diagram showing a lateral aberration diagram of the second optical path of the whole optical system of Example 2-2. (Fig. 8)

 FIG. 6 is a cross-sectional view taken along the central axis of the optical system of Example 3-1 of the present invention.

 (Fig. 9)

 FIG. 10 is a diagram showing lateral aberration diagrams of the first optical path of the entire optical system of Examples 3-1 and 3-2.

 (Fig. 10)

 FIG. 5 is a cross-sectional view taken along the central axis of the optical system of Example 3-2 of the present invention.

 (Fig. 1 1)

 FIG. 10 is a diagram showing a lateral aberration diagram of the second optical path of the whole optical system of Example 3-2. (Fig. 1 2)

 It is sectional drawing taken along the central axis of the optical system of Example 4 of this invention. (Fig. 1 3)

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

 (Fig. 14)

 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.

 (Fig. 15)

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

 (Fig. 17)

 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 1 8)

 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.

 (Fig. 1 9)

 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 2 2]

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

 [0 0 2 3]

 FIG. 2 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.

 An optical system 1 according to the present invention is rotationally symmetric with respect to a central axis 2 and includes an aperture S and a transparent medium L, and forms or projects an image without forming an intermediate image in the optical path. It is. The parallel plate near the image plane 5 is the cover glass C b 2 of the image sensor.

 [0 0 2 4]

The optical system 1 of Example 1 is configured so as to be rotationally symmetric around the central axis 2 in a cross section including the central axis 2, and is disposed on the object side on the central axis 2, and the image plane of the aperture S A transparent medium L having a refractive index greater than 1, and the transparent medium L is a first transmission surface disposed on the central axis 2 near the opening S. Rear 1st group 1st transmission surface 2 1 and Rear 1st group 1st transmission surface 21 2 and rear 1st group 1st reflecting surface 2 2 rear side 1st group 2nd reflecting surface 2 3 and rear 1st group as 2nd reflecting surface which is arranged on the opposite side to the image plane from 2 2nd transmission surface 2 4 as rear transmission group 2 as the second transmission surface arranged on the image plane side from second reflection surface 2 3, rear first group first transmission surface 2 1, rear first group first The reflecting surface 2 2, the rear group 1 second reflecting surface 2 3, and the rear group 1 second transmitting surface 2 4 are spherical, and the light beam incident on the transparent medium L passes through the aperture S in the order of forward ray tracing, After entering the transparent medium L through the rear first group first transmission surface 2 1, reflected to the opposite side to the image surface 5 by the rear first group first reflection surface 2 2, and then reflected by the rear first group second reflection surface 23 Reflected on the surface 5 side, and then passes through the first group, the second transmission surface 24, and the transparent medium L. A first optical path A is formed, and at least the rear first group first reflective surface 2 2 and the rear first group second reflective surface 2 3 of the first optical path A are configured only on one side with respect to the central axis 2. Thus, an intermediate image is not formed in the first optical path A, but is formed in an annular shape on the image plane 5.

 [0 0 2 5]

 Rear group 1 first transmitting surface 2 1, rear group 1 first reflecting surface 2 2, rear group 1 second reflecting surface 2 3 arranged in the vicinity of the aperture S in the order of the optical path from the object side on the central axis 2 It is important that the rear group 1 and the second transmission surface 24 are arranged in this order, and that the rear group 1 and the first reflection surface 2 2 and the rear group 1 and the second reflection surface 2 3 are both arranged with the concave surface facing the image side. is there.

 [0 0 2 6]

It is important that the aperture S is in the vicinity of the first transmission surface 21 in the first group on the rear side of the object side. If the aperture S is arranged on the image side of the transparent medium L of the present invention, astigmatism is greatly generated and a flat image is generated. Cannot be formed. In addition, the tilt angle of the main light beam is increased, resulting in poor telecentricity. Furthermore, interference between the effective diameters of the rear first group first transmission surface 21 and the rear first group second reflection surface 23 occurs, and it becomes impossible to increase the angle of view. [0 0 2 7]

 Next, the rear first group first reflecting surface 2 2 and the rear first group second reflecting surface 2 3 face the concave side toward the image side, and the rear first group first reflecting surface 2 2 and the rear first group second reflecting surface 2 3 It is important that the optical path between is constructed on one side without straddling the axis of rotational symmetry and is a Z-shaped optical path.

 [0 0 2 8]

 With this arrangement, a negative and positive arrangement is made in order of the optical path from the object side, so that a so-called retrofocus configuration can be achieved, and a wide angle of view can be achieved. In addition, this arrangement makes it possible to place the principal point of the optical system on the object side and to 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 2 9]

 Further, by disposing the reflecting surface between the transmitting surfaces and configuring the reflecting surface as an internal reflecting surface, it is possible to reduce the occurrence of aberrations such as field curvature. 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 obtained for a wide angle of view.

 [0 0 3 0]

 Further, the rear first group first reflecting surface 2 2 is configured so that light having a wide angle of view is 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 4 a 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 0 3 1]

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 transparent medium L. This makes the mutual plane This reduces the interference of light rays at the lens and makes it possible to secure a wide angle of view.

 [0 0 3 2]

 Further, it is preferable that the rear first group first reflecting surface 2 2 and the rear first group second transmitting surface 24 be disposed close to the image surface 5 side of the transparent medium L. This makes it possible to shorten the transparent medium and the image plane 5. The total length of the optical system can be shortened.

 [0 0 3 3]

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

 [0 0 3 4]

 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 0 3 5]

 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 3 6]

 More preferably, the rear first group third reflecting surface 25 is provided near the central axis of the rear first group first reflecting surface 22, and the light beam incident on the transparent medium L has an aperture S in the order of forward ray tracing. After passing through the first group 1 first transmission surface 2 1 and entering the transparent medium L, and after passing through the first group third transmission surface 25, the second optical path B is formed that exits from the transparent medium L to the image plane 5 side. This makes it possible to capture the image of the central part.

 [0 0 3 7]

In addition, a lens is disposed on the object side and / or the image plane side of the transparent medium L. With this, the angle of view can be increased.

 [0 0 3 8]

 Further, the transparent medium L is configured by joining a first transparent medium and a second transparent medium having different refractive indexes, so that lateral chromatic aberration and the like can be reduced.

 [0 0 3 9]

 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: K D / (2 X 1 max) <5 · · · (1)

 [0 0 4 0]

 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 0 4 1]

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

 It is desirable to satisfy the following condition: 1 <Lo / (2 X I max) <3 ··· (2)

 [0 0 4 2]

 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 4 3]

In addition, 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 conditions.

 [0 0 4 4]

 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 Compared to the positive power of the reflecting surface 2 3, the negative power of the 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 4 5]

 In addition, all the embodiments are configured by a spherical surface, but may be configured by a normal aspherical surface. The parallel plane on the object side is for protecting the optical system and may be omitted. The parallel plane on the image side is for protecting the image sensor and may be omitted.

 [0 0 4 6]

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

 [0 0 4 7]

 In forward ray tracking, for example, as shown in Fig. 1, the coordinate system uses the point where the diaphragm and the center axis 2 intersect as the origin O of the decentered optical surface, and the direction perpendicular to the center axis 2 as the Y axis direction. The plane of the paper in Fig. 1 is the Y-Z plane. In addition, the direction on the image plane 5 side in FIG.

 [0 0 4 8]

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 methods. [0 0 4 9]

 In addition, the term relating to an aspheric surface that is not described in the configuration parameters described later is 0. Refractive index and Abbe number are shown for d-line (wavelength 587. 56 nm). The unit of length is mm.

 [0 0 5 0]

 A cross-sectional view taken along the central axis 2 of the optical system 1 of Example 1 is shown in FIG. Further, FIG. 3 shows a lateral aberration diagram of the entire optical system of this example. In this lateral aberration diagram, the angle shown in the center indicates (horizontal field angle, vertical field angle), and lateral aberrations in the Y direction (meridinal direction) and X direction (sagittal direction) at that field angle. Indicates. 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 positive X-axis direction for the vertical field angle. same as below.

 [0 0 5 1]

 In this example, the transmission surface and the reflection surface of the transparent medium L having a refractive index larger than 1 concentrically symmetric with respect to the central axis 2 of the optical system 1 are configured as spherical surfaces that are partially shared in the optical path. is there.

 [0 0 5 2]

 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 5 3]

 The front group G f consists of a front group cover glass C f whose refractive index is rotationally symmetric about the central axis 2 and greater than 1. The front cover glass C f is composed of parallel flat plates, and the front group first transmission surface 1 1 and the front group second transmission surface 1 2 formed on the image side with respect to the front group first transmission surface 1 1. And have.

 [0 0 5 4]

Rear group 1 G b 1 has a rotationally symmetric refractive index greater than 1 around the central axis 2 It consists of a transparent medium. The transparent medium L 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 a part of the reflection coating 4 a The rear 1st group 1st reflecting surface 2 2 having negative power and the rear 1st group 1st reflecting surface 2 2 are arranged on the opposite side of the image plane 5 and the reflective coating 4b is used. And a rear first group second reflecting surface 2 3 having a positive power and a rear first group second reflecting surface 2 4 having a positive power. 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 0 5 5]

 The rear 2 group G b 2 is composed of a rear 2 group cover glass C b 2 force whose refractive index rotationally symmetric about 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 2.

 [0 0 5 6]

 The optical system 1 forms the optical path A. The light beam incident from the object plane of optical system 1 is the front group of front group cover glass C f, first transmission surface 1 1, front group second transmission surface 1 2, front group cover glass C f and transparent medium L And enters the transparent medium L through an opening S arranged coaxially with the central axis 2. In the transparent medium L, it enters after the first group 1 first transmission surface 2 1, and the rear 1 group 1 reflection surface 2 2 is partly reflective coating 4 a, and part is totally reflected and opposite to the image surface 5 Reflected on the back, 1st group 2nd reflecting surface 2 3 Reflected on the image surface 5 side by the reflective coating 4b, and then 1st group 2nd transmitting surface 2 4 It has a light path. 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 5 7]

The specification of Example 1 is Angle of view 20.00-60.0 °

Entrance pupil diameter Φ 0.10mm

Image size Φ 0. 79 to Φ 2. 00

It is.

 [0 0 5 8]

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

[0 0 5 9]

 In this example, the transmission surface and the reflection surface of the transparent medium L having a refractive index larger than 1 concentrically symmetric with respect to the central axis 2 of the optical system 1 are configured as spherical surfaces that are partially shared in the optical path. is there.

 [0 0 6 0]

 The optical system 1 includes a front group, 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 group 1 G b 1 and rear group 2 G b 2.

 [0 0 6 1]

 The front group G ί consists of a front group cover glass C f having a refractive index rotationally symmetric around the central axis 2 greater than 1. The front cover glass C f is composed of a parallel plate, and includes a front group transmission surface 1 1 and a front group second transmission surface 1 2 formed on the image side with respect to the front group first transmission surface 1 1. Have.

 [0 0 6 2]

The rear group 1 G b 1 consists of a transparent medium with a refractive index greater than 1 which is rotationally symmetric about the central axis 2. The transparent medium L 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 a part of the reflection coating 4 a The rear first group first reflecting surface 2 2 having negative power and the rear first group first reflecting surface 2 2 are arranged on the opposite side of the image plane 5, and the reflection coating 4 b is positive. Rear 1st group 2nd reflecting surface 2 3 and rear 1st group 1 1

2 It is arranged on the image surface 5 side from the reflecting surface 2 3 and has a rear first group second transmitting surface 24 having positive power. 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 0 6 3]

 The rear 2 group G b 2 is composed of the rear 2 group cover glass C b 2 having a rotationally symmetric refractive index greater than 1 around the central axis 2. Rear 2nd group cover glass Cb2 consists of parallel flat plates, and rear 2nd group 1st transmission surface 3 1 and rear 2nd group 1st transmission surface 3 1 are formed on the image side 2nd rear group 2 And a second transmission surface 3 2.

 [0 0 6 4]

 The optical system 1 forms the first optical path A. In the first optical path A, the light beam incident from the object plane of the optical system 1 is the front group first transmission surface 1 1, front group second transmission surface 1 2, and front group cover glass C C of the front group cover glass C f; It enters the transparent medium L through an opening S arranged coaxially with the central axis 2 between f and the transparent medium L. In the transparent medium L, it enters after the first group 1 first transmission surface 2 1, and part of the rear 1 group 1 reflection surface 2 2 is partially reflective coating 4 a, and the other part is reflected to the opposite side of the image surface 5 by total reflection. After that, it is reflected by the reflective coating 4b at the first group second reflecting surface 2 3 to the image surface 5 side, and then passes through the first group second transmitting surface 24 and exits from the transparent medium L through a substantially Z-shaped optical path. Have After that, 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 positioned at a predetermined radial position away from the central axis 2 of the image surface 5. It forms an image in an annular shape.

 [0 0 6 5]

 The specifications of this Example 2-1 are

Angle of view 20.00-60.0 °

Entrance pupil diameter φ 0. 10M

Image size Φ 0. 92 ~ Φ 1. 89

It is.

[0 0 6 6] A cross-sectional view taken along the central axis 2 of the optical system 1 of Example 2-2 is shown in FIG. Further, FIG. 7 shows a lateral aberration diagram of the second optical path B of the optical system of this example. The lateral aberration diagram of the first optical path A of the optical system of this example is the same as FIG.

 [0 0 6 7]

 In this example, the transmission surface and the reflection surface of the transparent medium L having a refractive index larger than 1 concentrically symmetric with respect to the central axis 2 of the optical system 1 are configured as spherical surfaces that are partially shared in the optical path. is there.

 [0 0 6 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 ί and the rear group G b. After 1 group G b 1 and After 2 group G b 2

 [0 0 6 9]

 The front group G f consists of a front group cover glass C f whose refractive index is rotationally symmetric about the central axis 2 and greater than 1. The front cover glass C f is composed of parallel flat plates, and the front group first transmission surface 1 1 and the front group second transmission surface 1 2 formed on the image side with respect to the front group first transmission surface 1 1. And have.

 [0 0 7 0]

 The rear group 1 G b 1 consists of a transparent medium L having a refractive index that is rotationally symmetric about the central axis 2 and greater than 1. The transparent medium L is formed on the image side with respect to the rear group 1 first transmission surface 21 and the rear group 1 first transmission surface 21 on the central axis 2, and a part of the reflection medium 4 a The rear first group first reflecting surface 2 2 having negative power and the rear first group first reflecting surface 2 2 are arranged on the opposite side of the image plane 5, and the reflecting coating 4 b is positive. The rear first group second reflecting surface 2 3 having the following power and the rear first group second reflecting surface 2 3 disposed on the image plane 5 side from the rear first group second reflecting surface 2 3 and having the positive power. Further, it has a rear first group third transmission surface 25 formed on the image side with respect to the rear first group first transmission surface 21 and having a positive power.

[0 0 7 1] The rear 2 group G b 2 is composed of the rear 2 group cover glass C b 2 having a rotationally symmetric refractive index greater than 1 around the central axis 2. 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 7 2]

 The optical system 1 forms a first optical path A and a second optical path B. In the first optical path A, the light beam incident from the object plane of the optical system 1 is divided into the front group first transmission surface 1 1, the front group second transmission surface 1 2, and the front group cover glass C f of the front group cover glass C f. It enters the transparent medium L via an opening S arranged coaxially with the central axis 2 between C ί and the transparent medium L. In the transparent medium L, it enters after the first group 1st transmission surface 2 1, part of it is reflective coating 4 a, and part is totally reflected, and the back 1 group 1st reflection surface 2 2 is opposite to the image surface 5 Reflected by the first group 2nd reflecting surface 2 3 and reflected by the reflective coating 4b to the image surface 5 side, then passed through the first group 2nd transmitting surface 2 4 and exited from the transparent medium L. It has a letter-shaped optical path. After that, the rear second group cover glass Cb 2 passes through the rear second group first transmission surface 3 1 and the rear second group second transmission surface 3 2, and then circles at a predetermined radial position away from the central axis 2 of the image plane 5. An image is formed in a ring shape. Of the first optical path A, part of the optical path through which the central chief ray passes through the boundary between the rear group 1 first reflecting surface 2 2 and rear group 1 third transmitting surface 25 is due to the reflection coating. The rear 1st group 1st reflecting surface 2 2 is reflected to the opposite side of the image surface 5 and the other part is divided into two optical paths passing through the 1st group 3rd transmitting surface 25 and connected to the same position on the image surface 5. Imaged.

 [0 0 7 3]

In the second optical path B, the light beam incident from the object surface of the optical system 1 is transmitted through the front group first transmission surface 1 1, front group second transmission surface 1 2, and front group cover. The glass C f and the transparent medium L enter the transparent medium L through an opening S arranged coaxially with the central axis 2. The transparent medium L has an optical path that passes through the rear group 1 and the first transparent surface 21 and exits from the transparent medium L through the rear group 1 and the third transparent surface 25. Then rear 2nd group cover glass Cb 2 rear 2nd group 1st transparent -

An image is formed on the central axis 2 of the image plane 5 through the oversurface 3 1 and the rear second group second transmission surface 3 2.

 [0 0 7 4]

 The specifications of Example 2-2 are as follows:

Angle of view

 First optical path A 20. 00 to 60.0 °

 Second optical path B 20 °

Entrance pupil diameter Φ 0.10mm

Image size

 1st optical path A Φ 0.92 to 1.89

 Second optical path B φ 0. 90

It is.

 [0 0 7 5]

 A cross-sectional view taken along the central axis 2 of the optical system 1 of Example 3-1 is shown in FIG. Further, FIG. 9 shows a lateral aberration diagram of the entire optical system of this example.

 [0 0 7 6]

 In this embodiment, the transmission surface and the reflection surface of the transparent medium L having a refractive index larger than 1 concentrically symmetric with respect to the central axis 2 of the optical system 1 are configured as a spherical surface that is partially shared in the optical path, and In this example, a front lens group L f and a rear second lens group L b 2 are arranged before and after the transparent medium L.

 [0 0 7 7]

 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 b 1 and the second group G b 2.

 [0 0 7 8]

The front group G f consists of a front group lens L f with a refractive index greater than 1 which is rotationally symmetric about the central axis 2. The front lens group L f is composed of a negative meniscus lens with a convex surface facing the object side, and is arranged on the front group first transmission surface 1 1 and front group first transmission surface 1 1. On the other hand, it has a front group second transmission surface 1 2 formed on the image side.

 [0 0 7 9]

 The rear group 1 G b 1 consists of a transparent medium L having a refractive index that is rotationally symmetric about the central axis 2 and greater than 1. The transparent medium L is formed on the image side with respect to the rear group 1 first transmission surface 21 and the rear group 1 first transmission surface 21 on the central axis 2, and a part of the reflection medium 4 a The rear first group first reflecting surface 2 2 having negative power and the rear first group first reflecting surface 2 2 are arranged on the side opposite to the image plane 5, and a part of the reflecting coating 4 b is provided. Rear 1st group 2nd reflecting surface 2 3 with positive power and rear 1st group 2nd reflecting surface 2 3 are arranged on the image plane 5 side from the rear 1st group 2nd reflecting surface 2 3 and have rear 1st group 2nd transmitting surface 2 4 with positive power . 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 0 8 0]

 The rear second group G b 2 is composed of the rear second group lens L b 2 having a rotationally symmetric refractive index greater than 1 around the central axis 2. The rear second group lens L b 2 is a plano-concave lens having a concave surface facing the object side, and is formed on the image side with respect to the rear second group first transmission surface 3 1 and the rear second group first transmission surface 3 1. And rear 2nd group second transmitting surface 3 2.

 [0 0 8 1]

The optical system 1 forms the optical path A. In the optical path A, the light beam incident from the object plane of the optical system 1 is the front group first transmission surface 1 1 and front group second transmission surface 1 2 of the front group lens L f, the front group lens L f and the transparent medium L. And enters the transparent medium L through the opening S arranged coaxially with the central axis 2. In the transparent medium L, it enters through the first group 1 and the first transmission surface 2 1, and the rear group 1 and the first reflection surface 2 2 are partially reflective coating 4 a and partly opposite to the image surface 5 due to total reflection. Reflected toward the back side, reflected back to the image surface 5 side by the reflection coating 4 b at the first group 2 second reflecting surface 2 3, and then exited from the transparent medium L through the rear group 1 second transmitting surface 2 4 Has an optical path. After that, a predetermined position in the radial direction deviating from the central axis 2 of the image plane 5 through the rear second group first transmission surface 3 1 and rear second group second transmission surface 3 2 of the rear second group lens L b 2 A circular image is formed on the screen.

 [0 0 8 2]

 The specifications of Example 3-1 are as follows:

Angle of view 36.00-90.0 °

Entrance pupil diameter φ 0.08 mm

Image size Φ 0. 97 to Φ 2. 00

It is.

 [0 0 8 3]

 A cross-sectional view taken along the central axis 2 of the optical system 1 of Example 3-2 is shown in FIG. In addition, Fig. 11 shows a lateral aberration diagram of the second optical path of the optical system of this example. The lateral aberration diagram of the first optical path in the optical system of this example is the same as FIG.

 [0 0 8 4]

 In this example, the transmission surface and the reflection surface of the transparent medium L having a refractive index larger than 1 concentrically symmetric with respect to the central axis 2 of the optical system 1 are configured as spherical surfaces that are partially shared in the optical path. is there.

 [0 0 8 5]

 The optical system 1 includes a front group G i, a rear group G b, and an aperture S arranged coaxially with the central axis 2 between the front group G ί 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 0 8 6]

 The front group G f is composed of a front group lens f having a refractive index which is rotationally symmetric about the central axis 2 and greater than 1. The front lens group L f is composed of a negative meniscus lens having a convex surface directed toward the object side. The front lens group L f is formed on the image side with respect to the front group first transmission surface 11 and the front group first transmission surface 11. 2 transmissive surface 1 2.

 [0 0 8 7]

The rear group 1 G b 1 consists of a transparent medium L having a refractive index that is rotationally symmetric about the central axis 2 and greater than 1. Transparent medium L consists of a spherical surface on center axis 2 1st transmission surface 2 1 and rear 1st group 1st transmission surface 2 1 formed on the image side with respect to the rear 1st group 1st reflection surface 2 2 And the rear first group second reflecting surface 2 3 which is disposed on the opposite side to the image surface 5 with respect to the rear first group first reflecting surface 2 2, partially reflectively coated 4 b, and has a positive power, The rear first group second reflecting surface 2 3 is disposed on the image plane 5 'side and has a rear first group second transmitting surface 24 having positive power. Further, it has a rear first group third transmission surface 25 formed on the image side with respect to the rear first group first transmission surface 21 and having a positive power.

 [0 0 8 8]

 The rear second group G b 2 is composed of the rear second group lens L b 2 having a rotationally symmetric refractive index greater than 1 around the central axis 2. The rear second group lens L b 2 is composed of a plano-concave lens having a concave surface facing the object side, and is formed on the image side with respect to the rear second group first transmission surface 3 1 and the rear second group first transmission surface 3 1. And rear 2nd group second transmitting surface 3 2.

 [0 0 8 9]

 The optical system 1 forms a first optical path A and a second optical path B.

 [0 0 9 0]

In the first optical path A, the light beam incident from the object plane of the optical system 1 is the front group first transmission surface 1 1, front group second transmission surface 1 2, front group lens L f, and front group lens L f. The transparent medium L enters the transparent medium L through the opening S arranged coaxially with the central axis 2 between the transparent media L. In the transparent medium L, after entering through the first group first transmitting surface 2 1, partly reflecting coating 4 a, and partly by total reflection, the rear first group first reflecting surface 2 2 and the image surface 5 Reflected to the opposite side, reflected back to the image surface 5 side by the reflective coating 4b at the rear 1st group 2nd reflecting surface 2 3 and then exited from the transparent medium L via the rear 1st group 2nd transmitting surface 2 4 It has a Z-shaped optical path. After that, the rear second group lens L b 2 passes through the rear second group first transmission surface 3 1 and the rear second group second transmission surface 3, and then annulars at a predetermined radial position away from the central axis 2 of the image surface 5. To form an image. Of the first optical path A, part of the optical path through which the central principal ray passes through the boundary between the rear group 1 first reflecting surface 22 and the rear group 1 third transmitting surface 25 is due to reflection coating. Rear 1st group 1st reflecting surface 2 2 is reflected to the opposite side of image plane 5 The light beam is divided into two light paths passing through the third transmission surface 25 and imaged at the same position on the image surface 5.

 [0 0 9 1]

 In the second optical path B, the light beam incident from the object plane of the optical system 1 is transmitted through the front group first transmission surface 11 and front group second transmission surface 1 2 of the front group lens L f, and the front group lens L The light enters the transparent medium L through the opening S arranged coaxially with the central axis 2 between f and the transparent medium L. The transparent medium L has an optical path that passes through the first group first transmitting surface 21 after the first group and exits from the transparent medium L through the third group third transmitting surface 25 after the first group. Thereafter, an image is formed on the central axis 2 of the image plane 5 through the rear second group first transmission surface 3 1 and the rear second group first transmission surface 3 2 of the rear second group lens L b 2.

 [0 0 9 2]

 The specifications of Example 3-2 are as follows:

Angle of view

 First optical path A 36.00 to 90.0 °

 Second optical path B 36.

Entrance pupil diameter Φ 0.08mm

Image size

 First optical path A Φ 0.97 to φ 2.00

 Second optical path B Φ 1.49

It is.

 [0 0 9 3]

 A cross-sectional view taken along the central axis 2 of the optical system 1 of Example 4 is shown in FIG. Also, the lateral aberration diagram of the second optical path of the optical system of this example is not shown in FIG.

 [0 0 9 4]

 In this example, the transmission surface and the reflection surface of the transparent medium L having a refractive index larger than 1 concentrically symmetric with respect to the central axis 2 of the optical system 1 are configured as spherical surfaces that are partially shared in the optical path. is there.

[0 0 9 5] 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 9 6]

 The front group G f consists of a front group cover glass C f whose refractive index is rotationally symmetric about the central axis 2 and greater than 1. The front cover glass C f is composed of parallel flat plates, and the front group first transmission surface 1 1 and the front group second transmission surface 1 2 formed on the image side with respect to the front group first transmission surface 1 1. And have.

 [0 0 9 7]

 The rear group 1 G b 1 consists of a transparent medium L having a refractive index that is rotationally symmetric about the central axis 2 and greater than 1. The transparent medium L is composed of a cemented lens having a birefringent positive lens L a as the rear first group first transparent medium and a biconcave positive lens L b as the rear first group second transparent medium having different refractive indexes, and is centered. A rear group 1 first transmission surface 2 1 made of a spherical surface on axis 2 and a part of the transparent medium L are coated with reflection coating 4 a, and are formed on the image side with respect to the rear group 1 first transmission surface 2 1. The first group 1st reflecting surface 2 2 having negative power and the transparent medium L are reflected and coated 4b, and the rear 1 group 1st reflecting surface 2 2 is disposed on the opposite side of the image plane 5; The rear first group second reflecting surface 2 3 having positive power and the rear first group second transmitting surface 2 4 having positive power arranged on the image plane 5 side from the rear first group second reflecting surface 23. Have. Further, it has a refracting surface 20 a b as a cementing surface of the biconvex positive lens L a and the biconcave positive lens L b. Rear 1st group 1st transmission surface 2 1 and Rear 1st group 2nd reflection surface 2 3 have the same position and 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 0 9 8]

The rear 2 group G b 2 is composed of the rear 2 group cover glass C b 2 having a rotationally symmetric refractive index greater than 1 around the central axis 2. 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 1. [0 0 9 9]

 The optical system 1 forms the optical path A. In the optical path A, the light beam incident from the object plane of the optical system 1 is divided into the front group first transmission surface 1 1, front group second transmission surface 1 2 and front group cover one glass C f of the front group cover glass C f. Enters the transparent medium L via the opening S arranged coaxially with the central axis 2 between the transparent medium L and the transparent medium L. In the transparent medium L, it enters after the first group first transmitting surface 2 1, passes through the refracting surface 20 ab, and partly reflects coating 4 a and partly on the rear group 1 first reflecting surface 2 2. Reflected to the opposite side of the image plane 5 by total reflection, passed through the refracting surface 20 ab, and then reflected back to the image surface 5 side by the reflective coating 4 b at the second reflecting surface 2 3 in the first group, and refracting surface 20 It has a substantially Z-shaped optical path that goes out of the transparent medium L through the rear side of the first group, the second transmission surface 24, and the ab. 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, and then circles at a predetermined radial position away from the central axis 2 of the image plane 5. An image is formed in a ring shape.

 [0 1 0 0]

 The specification of this Example 4 is

Angle of view 25.00-60.0 °

Entrance pupil diameter Φ 0.20mm

Image size φ0.88〜 Ψ 1.98

It is.

 [0 1 0 1]

 The maximum image height is I max (mm), the minimum image height is I min (■), 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 0 min ( Degree), focal length F (mm) = (I max-I min) / (Θ max-Θ min), rear group G r outer diameter D (mm), rear group excluding parallel flat protective glass When the total length of G r is L o (mm), the curvature of the rear group first reflective surface 2 2 is 1, and the curvature of the rear group second reflective surface 2 3 is R 2,

Example 1 Example 2 Example 3 Example 4 I max 1.00 0.95 1.00 0.99 Θ max 60.00 60.00 66.76 60.00

I mill 0. 39 0.46 0. 48 0. 44

Θ niin 20. 00 25.00 29. 89 25. 00

F 0. 015 0.014 0. 014 0. 016

D 2. 50 2.00 3. 20 1. 30

L 1. 950 1.875 2. 650 1. 55

D (2 X I max) 1. 250 1.053 1. 600 0. 657

L o (2 X I max) 0. 975 0.987 1. 325 0. 783

R 1 6. 92 7.33 8. 06 9. 35

R 2 8. 10 8.15 8. 95 8. 89

R 1 / R 2 0. 85 0.90 0. 90 1. 05.

 [0 1 0 2]

 The configuration parameters of Examples 1 to 4 are shown below. In the following, “R E” indicates a reflecting surface.

 [0 1 0 3]

 Example 1

物体面 oo 10.00 Surface number Curvature radius Surface spacing Eccentric Refractive index Abbe

Object surface oo 10.00

 1 oo 0.50 1. 5163 64.1

2 oo 0.20

 3 ∞ (Aperture) 0.00

 4 1.69 0.64 1. 5163 64.1

5 (R E) 1.50 -0.64 1. 5163 64.1

6 (R E) 1.69 0.64 1. 5163 64.1

7 1.50 0.83

 8 oo 0.40 1. 5163 64.1

9 oo 0.10 Image plane ∞

 [0 1 0 4]

 Example 2-1

Surface number Curvature radius Surface spacing Eccentric Refractive index Abbe number Object surface ∞ 10. 00

 1 oo 0. 50 1.5163 64.1

2 ∞ 0. 20

 3 ∞ (Aperture) 0.00

 4 1.92 0. 69 1.8348 42.7

5 (R E) 1.92-0. 69 1.8348 42.7

6 (R E) 1.92 0. 69 1.8348 42.7

7 1.92 0. 51

 8 ∞ 0. 40 1.5163 64.1

9 ∞ 0. 10

Image plane ∞

 [0 1 0 5]

 Example 2— 2

1st optical path

Surface number Curvature radius Surface spacing Eccentric Refractive index Abbe number Object surface ∞ 10. 00

 1 oo 0. 50 1.5163 64.1 oo 0. 20

 3 ∞ (Aperture) 0.00

 4 1.92 0. 69 1.8348 42.7

5 (R E) 1.92-0. 69 1.8348 42.7

6 (R E) 1.92 0. 69 1.8348 42.7

7 1.92 0. 51

8 oo 0. 40 1.5163 64.1 9 oo 0.10

Image plane ∞

Second optical path

Surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ 10.00

 1 ∞ 0.50 1.5163 64.1

2 ∞ 0.20

 3 ∞ (Aperture) 0.00

 4 1.92 0.69 1.8348 42.7

5 -1.25 0.51

 6 ∞ 0.40 1.5163 64.1

7 ∞ 0.10

Image plane ∞

 [0 1 0 6]

 Example 3— 1

1st optical path

Surface number Curvature radius Surface spacing Eccentric Refractive index Abbe number Object surface ∞ OO

 1 2.61 0.50 1.5163 64.1

2 0.34 0.20

 3 ∞ (Aperture) 0.10

 4 1.74 0.81 1.8348 42.7

5 (E) 1.32-0.81 1.8348 42.7

6 (R E) 1.74 0.81 1.8348 42.7

7 1.32 1.35

 8 -1.81 0.40 1.7552 27.6

9 O0 0.10

Statue face oo [0 1 0 7]

 Example 3-2

1st optical path

Surface number Curvature radius Surface spacing Eccentric refractive index Abbe number Object surface 0O oo

 1 2. 61 0. 50 1. 5163 64. 1

2 0. 34 0. 20

 3 ∞ (Aperture) 0. 10

 5 (R E) 1. 32-0. 81 42. 7

6 (R E) 1.74 0. 81 1. 8348 42.7

7 1. 32 1. 35

 8 -1. 81 0. 40 1. 7552 27. 6

9 CO 0. 10

Statue face oo o

Second optical path

Surface number Curvature radius Surface spacing Eccentric Refractive index Abbe Retrieval Object surface oo

 1 2. 00 2. 00

 2 2. 61 0. 50 64. 1

3 0. 34 0. 20

4 ∞ (Aperture) 0. 10

 6 -0. 90 1. 35

 7 -1. 81 0. 40 1. 7552 27. 6

8 oo 0. 10

Image plane oo 0. 00

[0 1 0 8] Example 4

Surface number Curvature radius Surface spacing Eccentric refractive index Abbe Object surface OD 10. 00

 1 OO 0. 50 1. 5163 64.1

2 CO 0. 20

 3 ∞ (Aperture) 0.00

 4 1.85 0. 42 1. 4875 70.4

5 -14.18 0. 10 1. 7440 44.8

6 (R E) 3.23-0. 10 1. 7440 44.8

7 -14.18-0. 42 1. 4875 70.4

8 (R E) 1.85 0. 42 1. 4875 70.4

9 -14.18 0. 10 1. 4875 70.4

10 3.23 0. 53

 11 OO 0. 40 1. 5163 64.1

12 OO 0. 10

Image plane CO

 [0 1 0 9]

 FIG. 14 shows an arrangement example of the image and the image sensor of this embodiment. Figure 14 (a) is 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 5 0 with the left and right positions of the image A 1 in the first optical path A. Fig. 14 (b) 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 B 1 in the second optical path B. Fig. 1 4 As in (a), the vertical image is not used. FIG. 14 (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 first optical path A. In this way, if the arrangement is made, both the image A 1 of the first optical path A and the image B 1 of the second optical path B can be captured.

[0 1 1 0] 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 1002 will be described. FIG. 15 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. 15 (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 a of the camera and an image is taken and observed. Figure 15 (b) shows the schematic configuration of the tip. Panorama photography optical system according to the present invention 1 0 ·

A flare stop 10 07 made of a casing or the like having an opening 10 6 extending in the circumferential direction is arranged around the entrance surface 1 1 of 1 to prevent the incidence of flare light. Also, FIG. 15 (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 1 1 1]

 FIG. 16 shows an example in which a photographic optical system 10 1 according to the present invention is attached to a capsule endoscope 120 and images of 360 ° omnidirectional images are taken and observed. A flare stop 1 0 7 is provided for a casing having an opening 10 6 extending in the circumferential direction in front of the first transmission surface 1 1 of the front group G f of the imaging optical system 1 0 1 according to the present invention. This prevents flare light from entering.

 [0 1 1 2]

 As shown in FIG. 15 and FIG. 16, by using the photographing optical system 10 1 for the endoscope, the image behind the photographing optical system 100 1 can be imaged and observed from a different angle from the conventional angle. Various parts can be imaged and observed.

 [0 1 1 3]

Fig. 17 (a) shows an image taken through each imaging optical system 1 0 1 on a display device in a car with the imaging optical system 1 0 1 according to the present invention attached as an imaging optical system in front of the automobile 1 3 0. Fig. 17 (b) shows an example in which the processed image is subjected to image processing to correct distortion and displayed at the same time. According to the present invention as a photographic optical system at the top of An example in which multiple photographic optical systems 1 0 1 are installed and images taken through each photographic optical system 1 0 1 on a display device in a car is subjected to image processing to correct distortion and simultaneously displayed FIG. In this case, as shown in FIG. 17 (a) ·, it is preferable that the left and right images can be captured widely by matching the size of the image sensor 50 with the left and right positions of the image A 1 in the first optical path A. .

 [0 1 1 4]

 Further, in FIG. 18, the projection optical system 100 according to the present invention is used as the projection optical system of the projection apparatus 140, and a panoramic image is displayed on the display element arranged on the image plane 5. This is an example in which a 360 ° omnidirectional image is projected and displayed on a screen 1 4 1 arranged in 360 ° omnidirectional through 0-2.

 [0 1 1 5]

 Furthermore, FIG. 19 shows a projection apparatus using the photographing optical system 1 0 1 according to the present invention indoors, with the photographing apparatus 15 1 using the photographing optical system 1 0 1 according to the present invention attached to the outside of the building 1 5 0. 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 15 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 1 1 6]

 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]  In an optical system that is rotationally symmetric about the central axis in a cross section including the central axis, the optical system is disposed on the object side on the central axis, and on the image plane side of the opening. A transparent medium having a refractive index greater than 1, the transparent medium being disposed on the image plane side from the first transmission surface, and a first transmission surface disposed on the central axis in the vicinity of the opening. A first reflecting surface having a concave surface facing the image surface side, a second reflecting surface disposed on the opposite side of the image surface from the first reflecting surface, and facing the concave surface to the image surface side, and from the second reflecting surface A second transmission surface disposed on the image plane side, wherein the first transmission surface, the first reflection surface, the second reflection surface, and the second transmission surface are curved surfaces, and the transparent medium The light beam incident on the light passes through the opening in the order of the tracking of the forward light ray, enters the transparent medium through the first transmission surface, and A first substantially Z-shaped first light reflected from the projection surface to the opposite side of the image surface, reflected from the second reflection surface to the image surface side, and exits from the transparent medium to the image surface side through the second transmission surface. An optical path is configured, and at least between the first reflecting surface and the second reflecting surface of the first optical path is 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 in that the image is formed in an annular shape on the image plane without being formed.  [2]  The first reflective surface is configured to reflect by a total reflection action and a reflective coating, and the reflective coating is provided only in the vicinity of the central axis of the first reflective surface. Item 2. The optical system according to Item 1.  [3] The optical system according to claim 1, wherein the first transmission surface and the second reflection surface are disposed on the object side of the transparent medium. [ Four ]  The optical system according to claim 1, wherein the first transmission surface and the second reflection surface have the same shape at the same position.  [ Five ]  2. The optical system according to claim 1, wherein the first reflection surface and the second transmission surface are disposed on an image surface side of the transparent medium.  [6]  The optical system according to claim 1, wherein the first reflecting surface and the second transmitting surface have the same shape at the same position.  [7]  A third transmission surface is provided in the vicinity of the central axis of the first reflection surface, and a light beam incident on the transparent medium passes through the opening in the order of forward ray tracing, passes through the first transmission surface, and enters the transparent medium. 2. The optical system according to claim 1, wherein a second optical path that enters and exits from the transparent medium to the image plane side through the third transmission surface is formed.  [8]  The optical system according to claim 1, wherein a lens is disposed on the object side and / or the image plane side of the transparent medium.  [9]  The optical system according to claim 1, wherein the transparent medium is configured by joining a first transparent medium and a second transparent medium having different refractive indexes.  [ Ten ]  When the maximum image height is I max and the outer diameter of the transparent medium is D,  2. The optical system according to claim 1, wherein the following condition is satisfied: 1 DZ (2 X 1 max) <5> (1).  [1 1] If the maximum image height is I max and the distance from the aperture to the image plane is Lo 2. The optical system according to claim 1, wherein the following condition is satisfied: 1 <L o (2 X 1 max) <3 • · − (2)  [1 2] When the curvature of the first reflecting surface is R l and the curvature of the second reflecting surface is R 2,

The optical system according to claim 1, wherein the following condition is satisfied.  [ 13 ]  The optical system according to claim 1, wherein the first reflection surface and the second reflection surface are rotationally symmetric aspheric surfaces.  [ 14]  2. The optical system according to claim 1, wherein the first reflecting surface and the second reflecting surface are formed of spherical surfaces.  [1 5]  An endoscope using the optical system according to claim 1.