WO2014083956A1 - Reflecting photographic lens - Google Patents

Abstract

A reflecting photographic lens comprises, in order from the object side, a first reflecting mirror, a second reflecting mirror, a third reflecting mirror, and a fourth reflecting mirror, positioned such that light from the object forms an object image in a prescribed image plane after being reflected in order by the first reflecting mirror, the second reflecting mirror, the third reflecting mirror, and the fourth reflecting mirror. The first through fourth reflecting mirrors have reflecting surfaces of rotationally asymmetrical astigmatic surface shapes, and are configured being symmetric with relation to a reference plane which is perpendicular to the image plane, including a first reference axis which is defined by a normal which passes through the center of the image plane. The first reflecting mirror has a concave surface facing the direction of entry of light. The first reflecting mirror and the second reflecting mirror are inclined in the same direction with respect to an orthogonal plane which is orthogonal to the first reference axis. The third reflecting mirror and the fourth reflecting mirror are inclined in the opposite direction to the first reflecting mirror with respect to the orthogonal plane. The second reflecting mirror and the third reflecting mirror are eccentrically positioned on the same side within the reference plane with respect to the first reference mirror.

Description

Reflective lens

The present invention relates to a reflection photographic lens.

For example, as a reflective photographing lens used for a camera, a reflective photographing lens that is advantageous for achieving both good correction of chromatic aberration and miniaturization is known. A conventional reflective photographic lens includes a concave reflecting mirror and a convex reflecting mirror arranged along a single optical axis extending linearly, and is an optical system that is rotationally symmetric with respect to the optical axis (for example, see Patent Document 1). reference).

Japanese Patent Laid-Open No. 11-212132

In the conventional reflection photographing lens, the central part of the light beam from the object (subject) is blocked by the convex reflecting mirror, and then sequentially reflected by the concave reflecting mirror having the central opening and the convex reflecting mirror, and the opening of the concave reflecting mirror. To reach the image plane. As a result, the central portion of the imaging light beam reaching the image plane is lacking, and ring-shaped blurring tends to occur in the object image due to defocus (focal position shift) with respect to the image plane.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a reflective photographic lens in which ring-shaped blur due to defocus does not occur.

According to the first aspect of the present invention, the reflective photographic lens includes, in order from the object side, the first reflecting mirror, the second reflecting mirror, the third reflecting mirror, and the fourth reflecting mirror, and the light from the object. Are sequentially reflected by the first reflecting mirror, the second reflecting mirror, the third reflecting mirror, and the fourth reflecting mirror, and are arranged so as to form an object image on a predetermined image plane, and the first reflecting mirror to the fourth reflecting mirror are arranged. Has a rotationally asymmetric aspherical reflecting surface, and is configured symmetrically with respect to a reference plane perpendicular to the image plane, including a first reference axis defined by a normal passing through the center of the image plane. The mirror has a concave surface with respect to the incident direction of light, and the first reflecting mirror and the second reflecting mirror are inclined in the same direction with respect to the orthogonal plane orthogonal to the first reference axis, and the third reflecting mirror and the fourth reflecting mirror are inclined. The reflecting mirror is inclined in the direction opposite to the first reflecting mirror with respect to the orthogonal plane, and the second reflecting mirror and the third reflecting mirror are within the reference plane. It is eccentrically arranged on the same side with respect to the reflector.
According to the second aspect of the present invention, in the reflective photographic lens of the first aspect, the center curvature of the intersection curve between the reflecting surface of the first reflecting mirror and the reference surface is A11, and the center of the reflecting surface of the first reflecting mirror is set. The center curvature of the intersection curve between the surface perpendicular to the reference plane including the normal line passing through and the reflection surface of the first reflector is A12, and the center curvature of the intersection curve between the reflection surface of the second reflector and the reference surface is A12. Assuming that A21 is the center curvature of the intersection curve between the plane perpendicular to the reference plane and including the normal passing through the center of the reflecting surface of the second reflecting mirror, and the reflecting surface of the second reflecting mirror is A22, (A12-A11 ) × (A22-A21)> − 0.00000005 (1) is preferably satisfied.
According to the third aspect of the present invention, in the reflective photographic lens of the first or second aspect, the rotationally asymmetric aspheric surface of the first reflecting mirror has the normal direction at the origin of the tangential plane of the aspheric surface as the z direction, The direction of the intersection line between the tangent plane and the reference plane is the y direction, the direction perpendicular to the y direction in the tangential plane is the x direction, the sag amount of the aspherical surface in the z direction is s, and m and n include 0. When a natural number is used and the coefficient of the monomial xm · yn is C1 (m, n), it is preferably defined by the following equation (2) and satisfying the following conditional equation (3).

According to the fourth aspect of the present invention, in the reflective photographic lens of any one of the first to third aspects, the rotationally asymmetric aspherical surface of the second reflecting mirror has a normal direction at the origin of the tangential plane of the aspherical surface as z. Direction, the direction of the line of intersection between the tangent plane and the reference plane is the y direction, the direction orthogonal to the y direction within the tangential plane is the x direction, the sag amount of the aspherical surface in the z direction is s, and m and n are When a natural number including 0 is used and the coefficient of the monomial xm · yn is C2 (m, n), it is preferably defined by the following expression (4) and satisfying the following conditional expression (5).

According to the fifth aspect of the present invention, in the reflective photographic lens of any one of the first to fourth aspects, there is provided a focusing optical system having at least one movable lens and for focusing an object on the image plane. Furthermore, it is preferable to provide.
According to the sixth aspect of the present invention, in the reflective photographic lens according to the fifth aspect, it is preferable that the focusing optical system is disposed in an optical path between the fourth reflecting mirror and the image plane.
According to the seventh aspect of the present invention, in the reflective photographic lens according to the fifth or sixth aspect, the focusing optical system has a plurality of lenses that can move integrally along a direction parallel to the first reference axis. It is preferable.
According to the eighth aspect of the present invention, in the reflective photographic lens according to any one of the first to seventh aspects, the first reflecting mirror to the fourth reflecting mirror are optically conjugate with the image plane at the position of the object. It is preferable that the object surface to be defined is arranged so as to be parallel to the image plane.
According to the ninth aspect of the present invention, in the reflective photographic lens according to any one of the first to eighth aspects, the first reflecting mirror to the fourth reflecting mirror are first with respect to the center of the reflecting surface of the first reflecting mirror. It is preferable that the light incident parallel to the reference axis is arranged so as to be perpendicularly incident on the center of the image plane through the second reflecting mirror, the third reflecting mirror, and the fourth reflecting mirror.

In the reflective photographic lens of the present invention, a solid cross-section light beam that does not lack a central portion forms an object image, so that a clear object image can be obtained without ring-shaped blurring due to defocusing. .

It is a figure which shows schematically the basic composition of the reflective photographic lens concerning each Example of embodiment. It is a figure which shows schematically the cross-sectional structure along YZ plane of the reflective photographic lens concerning 1st Example. It is a figure which shows roughly the cross-sectional structure along XZ plane of the reflective photographic lens concerning 1st Example. It is a figure which shows the distortion aberration of 1st Example. It is a figure which shows the aberration with respect to e line of 1st Example by a spot diagram. It is a figure which shows the position of nine image points in the spot diagram of each Example. It is a figure which shows schematically the cross-sectional structure along YZ plane of the reflective photographic lens concerning 2nd Example. It is a figure which shows schematically the cross-sectional structure along XZ plane of the reflective photographic lens concerning 2nd Example. It is a figure which shows the distortion aberration of 2nd Example. It is a figure which shows the aberration with respect to e line of 2nd Example by a spot diagram. It is a figure which shows schematically the cross-sectional structure along YZ plane of the reflective photographic lens concerning 3rd Example. It is a figure which shows schematically the cross-sectional structure along XZ plane of the reflective photographic lens concerning 3rd Example. It is a figure which shows the distortion aberration of 3rd Example. It is a figure which shows the aberration with respect to e line of 3rd Example by a spot diagram. It is a figure which shows schematically the cross-sectional structure along YZ plane of the reflective photographic lens concerning 4th Example. It is a figure which shows schematically the cross-sectional structure along XZ plane of the reflective photographic lens concerning 4th Example. It is a figure which shows the distortion aberration of 4th Example. It is a figure which shows the aberration with respect to e line of 4th Example by a spot diagram. It is a figure which shows schematically the cross-sectional structure along YZ plane of the reflective photographic lens concerning 5th Example. It is a figure which shows schematically the cross-sectional structure along XZ plane of the reflective photographic lens concerning 5th Example. It is a figure which shows the distortion aberration of 5th Example. It is a figure which shows the aberration with respect to e line of 5th Example by a spot diagram. It is a figure which shows roughly the cross-sectional structure along YZ plane of the reflective photographic lens concerning 6th Example. It is a figure which shows schematically the cross-sectional structure along XZ plane of the reflective photographic lens concerning 6th Example. It is a figure which shows the distortion aberration of 6th Example. It is a figure which shows the aberration with respect to e line of 6th Example by a spot diagram. It is a figure which shows schematically the cross-sectional structure along YZ plane in the infinite point focusing state of the reflective photographic lens concerning 7th Example. It is a figure which shows schematically the cross-sectional structure along XZ plane in the infinite point focusing state of the reflective photographic lens concerning 7th Example. It is a figure which shows schematically the cross-sectional structure along YZ plane in the 1st distance focusing state of the reflective photographic lens concerning 7th Example. It is a figure which shows schematically the cross-sectional structure along YZ plane in the 2nd distance focusing state of the reflective photographic lens concerning 7th Example. It is a figure which shows the aberration with respect to e line in the infinite point focusing state of 7th Example by a spot diagram. It is a figure which shows the aberration with respect to e line in the 1st distance focusing state of 7th Example by a spot diagram. It is a figure which shows the aberration with respect to e line in the 2nd distance focusing state of 7th Example by a spot diagram. It is a figure which shows the aberration with respect to g line in the infinite point focusing state of 7th Example by a spot diagram. It is a figure which shows the aberration with respect to g line in the 1st distance focusing state of 7th Example by a spot diagram. It is a figure which shows the aberration with respect to g line in the 2nd distance focusing state of 7th Example by a spot diagram. It is a figure which shows schematically the cross-sectional structure along YZ plane in the infinite point focusing state of the reflective photographic lens concerning 8th Example. It is a figure which shows schematically the cross-sectional structure along XZ plane in the infinite point focusing state of the reflective photographic lens concerning 8th Example. It is a figure which shows schematically the cross-sectional structure along YZ plane in the 1st distance focusing state of the reflective photographic lens concerning 8th Example. It is a figure which shows schematically the cross-sectional structure along YZ plane in the 2nd distance focusing state of the reflective photographic lens concerning 8th Example. It is a figure which shows the aberration with respect to e line in the infinite point focusing state of 8th Example by a spot diagram. It is a figure which shows the aberration with respect to e line in the 1st distance focusing state of 8th Example by a spot diagram. It is a figure which shows the aberration with respect to e line in the 2nd distance focusing state of 8th Example by a spot diagram. It is a figure which shows the aberration with respect to g line in the infinite point focusing state of 8th Example by a spot diagram. It is a figure which shows the aberration with respect to g line in the 1st distance focusing state of 8th Example by a spot diagram. It is a figure which shows the aberration with respect to g line in the 2nd distance focusing state of 8th Example by a spot diagram.

Prior to specific description of each example in the embodiment, a basic configuration of the reflection photographing lens according to the present invention will be described. The present invention is a reflective photographic lens having high-definition imaging performance without distortion, in which chromatic aberration is well corrected over the wavelength range of g-line (435.83 nm) to C-line (656.27 nm) in the visible range. Has proposed.

Specifically, in the reflective photographing lens of the present invention, the object image is reflected on a predetermined image plane after sequentially reflecting light from the object by the first reflecting mirror, the second reflecting mirror, the third reflecting mirror, and the fourth reflecting mirror. Form. The first to fourth reflecting mirrors have a rotationally asymmetric aspherical reflecting surface and include a first reference axis defined by a normal passing through the center of the image surface and a reference surface perpendicular to the image surface Is configured symmetrically. The first reflecting mirror has a concave surface with respect to the light incident direction. The first reflecting mirror and the second reflecting mirror are inclined in the same direction with respect to the orthogonal plane orthogonal to the first reference axis, and the third reflecting mirror and the fourth reflecting mirror are opposite to the first reflecting mirror with respect to the orthogonal plane. Tilt in the direction. The second reflecting mirror and the third reflecting mirror are arranged eccentrically on the same side with respect to the first reflecting mirror in the reference plane.

In the present invention, the four reflecting mirrors are arranged eccentrically so as not to shield the imaging light beam. Then, in order to correct the decentration aberration caused by the eccentric arrangement of the reflecting mirrors, the reflecting surfaces of the four reflecting mirrors are formed in a rotationally asymmetric aspheric shape. Here, the four reflecting mirrors having the rotationally asymmetric aspherical reflecting surfaces are used to obtain a good object image. Hereinafter, the reason why the reflection photographic lens is constituted by four reflecting mirrors in the present invention will be described.

The reflection photographic lens of the present invention is preferentially used as a camera lens. In this case, it is necessary to form an inverted image as in a normal refractive optical system. Focusing on the formation of an inverted image, the number of reflecting mirrors constituting the reflective photographing lens is limited to an even number. That is, in the case of a plurality of reflecting mirrors, the minimum number of reflecting mirrors is two, and the next smallest required number is four.

On the other hand, if attention is paid only to the correction of aberrations in the reflective photographic lens, especially correction of spherical aberration, a single reflecting mirror having an aspherical reflecting surface is also possible. However, in the case of a camera lens, a relatively wide field of view is required. In order to satisfactorily correct the field curvature, at least one convex mirror and at least one concave mirror are required to suppress the so-called Petzval sum. Furthermore, in order to satisfactorily correct coma over a wide field of view, it is not sufficient to use two reflecting mirrors constituting the reflective photographic lens. Therefore, in the present invention, by using four reflecting mirrors, good correction of various aberrations (such as astigmatism and coma) is realized over a wide field of view.

In the present invention, since a telephoto lens in which correction of chromatic aberration is difficult is assumed, the focal length of the optical system becomes longer and the aperture becomes larger. Therefore, in the present invention, the first reflecting mirror disposed closest to the object side has a concave surface directed toward the incident direction of light. That is, the first reflecting mirror has a positive power. In this way, by applying positive power to the first reflecting mirror on which the light from the object first enters, the light flux that has passed through the first reflecting mirror can be reduced, and the three following the first reflecting mirror can be reduced. The aperture of the reflecting mirror can be kept small, and the weight of the optical system can be reduced.

In the reflection photographing lens of the present invention, four reflecting mirrors are arranged eccentrically in order to avoid the central shielding of the imaging light beam, which is a drawback of the coaxial reflecting optical system. Specifically, in the present invention, as a decentration arrangement advantageous for correcting coma aberration, the first reflecting mirror and the second reflecting mirror are inclined in the same direction with respect to the orthogonal plane orthogonal to the first reference axis, and the third reflecting mirror And the fourth reflecting mirror is inclined in the opposite direction to the first reflecting mirror with respect to the orthogonal plane, and the second reflecting mirror and the third reflecting mirror are eccentrically arranged on the same side with respect to the first reflecting mirror in the reference plane. Adopted.

In the configuration in which a plurality of reflecting mirrors are arranged eccentrically, astigmatism that is the lowest-order asymmetrical aberration occurs. In the present invention, in order to satisfactorily correct astigmatism, the vicinity of the center of the reflecting surface of the first reflecting mirror and the second reflecting mirror is a so-called toric surface (a surface having a different radius of curvature in two orthogonal directions). It is preferable to form. Specifically, in order to satisfactorily correct astigmatism due to the eccentric arrangement, it is preferable that the first reflecting mirror and the second reflecting mirror satisfy the following conditional expression (1).
(A12-A11) × (A22-A21)> − 0.00000005 (1)

In conditional expression (1), A11 is the central curvature of the intersection curve between the reflecting surface of the first reflecting mirror and the reference surface, and A21 is the center curvature of the intersection curve between the reflecting surface of the second reflecting mirror and the reference surface. . A12 is the central curvature of the intersection curve of the surface perpendicular to the reference surface including the normal passing through the center of the reflecting surface of the first reflecting mirror and the reflecting surface of the first reflecting mirror, and A22 is the second reflecting mirror. This is the center curvature of the intersection curve of the surface perpendicular to the reference surface including the normal passing through the center of the reflecting surface and the reflecting surface of the second reflecting mirror.

That is, (A12-A11) is a difference in curvature in two directions orthogonal to each other at the center of the first reflecting mirror, and (A22-A21) is a difference in curvature in two directions orthogonal to each other at the center of the second reflecting mirror. . Satisfying conditional expression (1) means that the difference in curvature at the center of the first reflecting mirror and the difference in curvature at the center of the second reflecting mirror have the same sign or almost no difference in curvature. Since the incident directions of light are opposite in the first reflecting mirror and the second reflecting mirror, when the signs of the curvature differences are the same, they exert positive and negative powers, respectively. Therefore, the conditional expression (1) indicates a condition in which the first reflection mirror and the second reflection mirror cancel each other out or do not strengthen each other. In other words, it is indicated that if the reflection component of the first reflecting mirror and the reflecting surface of the second reflecting mirror mutually intensify each other, it becomes difficult to correct aberrations in the entire optical system.

For example, when the first reflecting mirror and the second reflecting mirror both have a concave surface facing the object side, the first reflecting mirror has a positive power and the second reflecting mirror has a negative power. Therefore, by satisfying conditional expression (1), it is possible to correct decentration astigmatism in a direction in which the first reflecting mirror and the second reflecting mirror cancel each other. Light from various fields of incidence enters the optical system, and the amount of astigmatism due to decentration varies depending on the field of view. Conditional expression (1) represents a condition necessary for the plurality of reflecting mirrors to correct aberrations while canceling each other. In order to sufficiently exhibit the above-described effect, it is preferable to set the lower limit value of conditional expression (1) to −0.00000003.

In the present invention, in order to satisfactorily correct aberrations, it is preferable that the rotationally asymmetric aspherical surface of the first reflecting mirror is defined by the following expression (2) and satisfies the following conditional expression (3). In equation (2), the normal direction at the origin of the rotationally asymmetric aspheric tangent plane of the first reflecting mirror is the z direction, the direction of the intersection of the tangential plane and the reference plane is the y direction, and within the tangential plane and a direction perpendicular to the y direction and x direction, the sag in the z-direction of the aspherical surface and s, m and n is a natural number including 0, the coefficients of the monomial x ^m · y ⁿ C ₁ (m, n) as Yes.

 

If the lower limit of conditional expression (3) is not reached, there is a tendency for significant distortion to occur, which is not preferable. On the other hand, when the value exceeds the upper limit value of conditional expression (3), the tendency of asymmetrical aberrations to occur greatly becomes significant, which is not preferable. In order to sufficiently exhibit the above-described effect, it is preferable to set the lower limit value of conditional expression (3) to −0.002. Moreover, in order to fully demonstrate the above-mentioned effect, it is preferable to set the upper limit of conditional expression (3) to 0.000173.

Similarly, in the present invention, in order to satisfactorily correct the aberration, the rotationally asymmetric aspherical surface of the second reflecting mirror is defined by the following expression (4) and satisfies the following conditional expression (5). preferable. In Equation (4), the normal direction at the origin of the rotationally asymmetric aspheric tangent plane of the second reflecting mirror is defined as the z direction, the direction of the intersection between the tangential plane and the reference plane is defined as the y direction, and within the tangential plane. and a direction perpendicular to the y direction and x direction, the sag in the z-direction of the aspherical surface and s, m and n is a natural number including 0, the coefficients of the monomial x ^m · y ⁿ C ₂ (m, n) as Yes.

 

As in the case of conditional expression (3), if the value falls below the lower limit value of conditional expression (5), the tendency for large distortion to occur is not preferable. On the other hand, if the value exceeds the upper limit value of conditional expression (5), the tendency of a large amount of asymmetric aberration to occur becomes significant. In order to sufficiently exhibit the above-described effect, it is preferable to set the lower limit value of conditional expression (5) to −0.005. Moreover, in order to fully demonstrate the above-mentioned effect, it is preferable to set the upper limit of conditional expression (5) to 0.004.

Hereinafter, embodiments will be described with reference to the accompanying drawings. FIG. 1 is a diagram schematically illustrating a basic configuration of a reflection photographing lens according to each example of the embodiment. The reflective photographic lens according to each embodiment is a photographic lens used in, for example, a camera. As shown in FIG. 1, in order of light incidence from the object side, a first reflective mirror CM1, a second reflective mirror CM2, It has a third reflecting mirror CM3 and a fourth reflecting mirror CM4. However, in the seventh and eighth embodiments, a focusing optical system is attached in the optical path between the fourth reflecting mirror CM4 and the image plane IM (see FIGS. 27, 37, etc.).

In FIG. 1, the reference axis AXa is a straight line connecting the center of an object at infinity and the center of the first reflecting mirror CM1 (the origin of the reflecting surface). The reference axis AXb is a straight line connecting the center of the first reflecting mirror CM1 and the center of the second reflecting mirror CM2 (the origin of the reflecting surface). The reference axis AXc is a straight line connecting the center of the second reflecting mirror CM2 and the center of the third reflecting mirror CM3 (the origin of the reflecting surface). The reference axis AXd is a straight line that connects the center of the third reflecting mirror CM3 and the center of the fourth reflecting mirror CM4 (the origin of the reflecting surface). The reference axis AXe is a first reference axis defined by a normal line passing through the center of the image plane IM, and is a straight line connecting the center of the fourth reflecting mirror CM4 and the center of the image plane IM.

In FIG. 1, as the global coordinate system (X, Y, Z), the X axis in the direction perpendicular to the paper surface of FIG. 1, the Y axis in the vertical direction along the paper surface of FIG. 1, and the paper surface of FIG. The Z axis is set in the horizontal direction. In each embodiment, the reference axes AXa, AXc, and AXe extend in the horizontal direction along the Z axis. All the reference axes AXa to AXe extend linearly along the paper surface (YZ plane) in FIG. That is, the reference axes AXa to AXe are zigzag in the cross-sectional configuration along the YZ plane, but appear to overlap one straight line in the cross-sectional configuration along the XZ plane. The image plane IM is a plane parallel to the XY plane, and the object plane and the image plane IM are parallel. Hereinafter, a plane including the reference axes AXa to AXe (a plane including the first reference axis AXe and perpendicular to the image plane IM), that is, a YZ plane is defined as a reference plane.

In FIG. 1, local coordinate systems (x, y, z) in the first reflecting mirror CM1 to the fourth reflecting mirror CM4 are set. In the local coordinate system of the first reflecting mirror CM1, the x axis is set parallel to the X axis, the yz plane is set to coincide with the YZ plane, and the y axis rotates the Y axis clockwise by an angle θ01. It is consistent with the direction obtained. That is, the magnitude of the angle formed by the y-axis of the local coordinate system of the first reflecting mirror CM1 and the Y-axis of the global coordinate system is θ01. In the local coordinate system of the second reflecting mirror CM2, the x axis is set parallel to the X axis, the yz plane is set to coincide with the YZ plane, and the y axis rotates the Y axis clockwise by an angle θ02. It is consistent with the direction obtained. That is, the magnitude of the angle formed by the y-axis of the local coordinate system of the second reflecting mirror CM2 and the Y-axis of the global coordinate system is θ02.

In the local coordinate system of the third reflector CM3, the x axis is set parallel to the X axis, the yz plane is set to coincide with the YZ plane, and the y axis rotates the Y axis counterclockwise by an angle θ03. Is consistent with the direction obtained. That is, the magnitude of the angle between the y-axis of the local coordinate system of the third reflecting mirror CM3 and the Y-axis of the global coordinate system is θ03. In the local coordinate system of the fourth reflector CM4, the x axis is set parallel to the X axis, the yz plane is set to coincide with the YZ plane, and the y axis rotates the Y axis counterclockwise by an angle θ04. Is consistent with the direction obtained. That is, the magnitude of the angle formed by the y-axis of the local coordinate system of the fourth reflecting mirror CM4 and the Y-axis of the global coordinate system is θ04.

In each embodiment, the angle magnitudes θ01, θ02, θ03, and θ04 are the same (or substantially the same). The reflecting surface of the first reflecting mirror CM1 is a rotationally asymmetric aspheric surface, and has a shape that is concave on the object side in the reference plane and in the xz plane perpendicular to the reference plane. The reflecting surface of the second reflecting mirror CM2, the reflecting surface of the third reflecting mirror CM3, and the reflecting surface of the fourth reflecting mirror CM4 are rotationally asymmetric aspheric surfaces.

In the first reflecting mirror CM1 to the fourth reflecting mirror CM4, the light beam of the solid cross section without the central portion is finally formed so that the central portion of the light beam from the object reaches the image surface IM without being blocked. Are arranged eccentrically so as to form an object image. The rotationally asymmetric aspheric surfaces (that is, free-form surfaces) in the first reflecting mirror CM1 to the fourth reflecting mirror CM4 are defined by the following equation (a). In formula (a), s is the sag of the z direction of the aspherical surface (unit: mm), m and n are natural numbers including 0, C (m, n) is the coefficient of the monomial x ^m · y ⁿ It is.

 

In the reflective photographic lens according to each example of the present embodiment, not only the correction of aberrations and the miniaturization can be achieved at the same time, but a solid cross-section light beam that does not lack a central portion forms an object image. To do. As a result, a natural object image can be obtained without ring-shaped blurring due to defocusing.

[First embodiment]
FIG. 2 is a diagram schematically illustrating a cross-sectional configuration along the YZ plane of the reflective photographing lens according to the first example. FIG. 3 is a diagram schematically illustrating a cross-sectional configuration along the XZ plane of the reflective photographing lens according to the first example. In each embodiment including the first embodiment, an aperture stop can be disposed at the position of the reflection surface of the first reflecting mirror CM1. 2 and the corresponding FIG. 7, FIG. 11, FIG. 15, FIG. 19, FIG. 23, FIG. 27, FIG. 29, FIG. An aperture stop arranged in an optical path of light virtually transmitted through one reflecting mirror CM1 is shown.

In the first to sixth embodiments, a plane parallel plate as a protective glass can be disposed at a position indicated by the reference symbol IP on the object side of the first reflecting mirror CM1. In the following table (1), values of specifications of the reflection photographing lens according to the first example are listed. In the column of the optical member specifications in Table (1), the surface number indicates the order of the surfaces from the object side along the path of light traveling from the object at infinity to the image plane IM. That is, the first surface is the reflecting surface of the first reflecting mirror CM1, the second surface is the reflecting surface of the second reflecting mirror CM2, the third surface is the reflecting surface of the third reflecting mirror CM3, and the fourth surface. Is the reflecting surface of the fourth reflecting mirror CM4, and the fifth surface is the image plane IM.

In the column of the optical member specifications in Table (1), the X coordinate (unit: mm), Y coordinate (unit: mm), Z coordinate of the origin of the local coordinate system (x, y, z) on each surface (Unit: mm) and the inclination angle δ (unit: degree) of the y-axis with respect to the Y-axis. The inclination angle δ is a positive value when the y-axis is coincident with the direction in which the Y-axis is rotated counterclockwise in the corresponding page, and the Y-axis is rotated clockwise by an acute angle. A negative value is assumed when the direction and the y-axis coincide.

Therefore, referring to FIG. 1 and FIG. 2, the inclination angle δ of the local coordinate system (x, y, z) on the reflecting surface of the first reflecting mirror CM1, which is the first surface, is θ01 and takes a negative value. . The inclination angle δ of the local coordinate system (x, y, z) on the reflecting surface of the second reflecting mirror CM2, which is the second surface, is θ02 and takes a negative value. The inclination angle δ of the local coordinate system (x, y, z) on the reflecting surface of the third reflecting mirror CM3 that is the third surface is θ03 and takes a positive value. The inclination angle δ of the local coordinate system (x, y, z) on the reflecting surface of the fourth reflecting mirror CM4, which is the fourth surface, is θ04 and takes a positive value.

The column of aspherical data in Table (1) shows each parameter of equation (a) that defines rotationally asymmetric aspherical surfaces (free curved surfaces) in the first reflecting mirror CM1 to the fourth reflecting mirror CM4. The notation in Table (1) is the same in the following Tables (2) to (8).

Table (1)
<Optical member specifications>
Surface number X coordinate Y coordinate Z coordinate Tilt angle δ
1 0 0.000 0.000 -34.889 (CM1)
2 0 96.075 -35.238 -34.889 (CM2)
3 0 96.067 95.212 34.889 (CM3)
4 0 0.006 60.018 34.889 (CM4)
5 0 0.000 150.000 0.000 (IM)
<Aspherical data>
Surface number 1 2 3 4
C (2,0) -0.00111196 -0.00127119 -0.00125218 -0.00174605
C (1,1) 0 0 0 0
C (0,2) -0.000480694 0.000174116 0.000618903 0.000153427
C (3,0) 0 0 0 0
C (1,2) -0.000002 -0.000004 -0.000003 -3.70426E-07
C (2,1) 0 0 0 0
C (0,3) -2.24695E-07 0.000002 0.000007 0.000003
C (4,0) 8.17556E-10 6.32012E-09 -3.68341E-09 -1.03485E-07
C (3,1) 0 0 0 0
C (2,2) -6.5826E-10 3.66535E-09 -4.387E-08 -1.16499E-07
C (1,3) 0 0 0 0
C (0,4) 5.59211E-09 2.95256E-08 1.08619E-07 7.09422E-08
C (5,0) 0 0 0 0
C (4,1) 3.68759E-12 6.78161E-11 6.37777E-11 3.22938E-10
C (3,2) 0 0 0 0
C (2,3) 1.0378E-11 1.94033E-10 -4.46774E-10 6.30174E-10
C (1,4) 0 0 0 0
C (0,5) 2.1576E-11 1.67307E-10 6.03942E-10 -1.72657E-09
C (6,0) 9.30004E-15 5.60321E-14 -2.14873E-13 -1.13739E-11
C (5,1) 0 0 0 0
C (4,2) 4.02132E-14 6.05657E-13 8.25947E-13 -1.56772E-11
C (3,3) 0 0 0 0
C (2,4) 8.07025E-14 1.16582E-12 -5.41036E-12 2.53656E-13
C (1,5) 0 0 0 0
C (0,6) 5.95145E-14 2.83865E-14 -1.29953E-12 -4.34571E-11
C (7,0) 0 0 0 0
C (6,1) 1.51564E-15 3.96279E-14 9.38923E-14 3.09796E-12
C (5,2) 0 0 0 0
C (4,3) 4.26289E-16 3.26447E-16 -4.08818E-14 -1.62462E-12
C (3,4) 0 0 0 0
C (2,5) 5.68713E-17 -3.80918E-15 -6.82503E-14 -3.21826E-13
C (1,6) 0 0 0 0
C (0,7) 2.19776E-16 -3.18348E-15 5.42582E-14 1.18377E-12

<Conditional values>
A11 = −0.000480694
A12 = −0.00111196
A21 = 0.000174116
A22 = −0.00127119
Conditional expression (1) (A12-A11) × (A22-A21) = 9.1373E-07
Conditional expression (3) C ₁ (2,0) −C ₁ (0,2) = − 0.00063
Conditional expression (5) C ₂ (2,0) −C ₂ (0,2) = − 0.00145

FIG. 4 is a diagram showing the distortion aberration of the first example. FIG. 5 is a diagram showing the aberration with respect to the e-line of the first embodiment in a spot diagram. FIG. 6 is a diagram showing the positions of nine image points in the spot diagram of each example. In each example, assuming an FX format digital camera, as shown in FIG. 6, spots at nine image points (viewpoints) S1 to S9 in a rectangular image plane IM of 36 mm × 24 mm were calculated. . The length of the unit scale in FIG. 5 is 0.1 mm = 100 μm. The notation of FIG. 5 is the same in the corresponding FIGS. 10, 14, 18, 18, 22, 26, 31 to 36, and 41 to 46. The e-line (546.07 nm) is a reference wavelength in the present embodiment, the g-line is generally the shortest wavelength when considering a visible optical system, and the C-line is generally the longest wavelength when considering a visible optical system. It is.

Referring to FIG. 4, it can be seen that in the first embodiment, the distortion is corrected well. Referring to FIG. 5, it can be seen that in the first embodiment, the spot size is sufficiently small at each of the image points S1 to S9, and the aberration is uniform and well corrected over the entire image plane IM. Further, it can be seen that the shape of the spot at each of the image points S1 to S9 is almost symmetric, and the asymmetric aberration is well corrected. Although only the e-line aberration is shown in the first embodiment, naturally, there is no chromatic aberration because the optical system is constituted only by the reflecting mirror. Since other aberrations are exactly the same as those of the e-line, illustration of the other wavelengths is omitted.

[Second Embodiment]
FIG. 7 is a drawing schematically showing a cross-sectional configuration along the YZ plane of the reflective photographing lens according to the second example. FIG. 8 is a drawing schematically showing a cross-sectional configuration along the XZ plane of the reflective photographing lens according to the second example. In the following table (2), values of specifications of the reflection photographing lens according to the second example are listed.

Table (2)
<Optical member specifications>
Surface number X coordinate Y coordinate Z coordinate Tilt angle δ
1 0 0.000 0.000 -35.099 (CM1)
2 0 95.909 -34.713 -35.099 (CM2)
3 0 95.953 94.851 35.099 (CM3)
4 0 0.078 60.249 35.099 (CM4)
5 0 0.000 150.000 0.000 (IM)

<Aspherical data>
Surface number 1 2 3 4
C (2,0) -0.00164987 -0.00327485 -0.000987512 0.000388435
C (1,1) 0 0 0 0
C (0,2) 0.00005 0.000755856 -0.000021 -0.00152649
C (3,0) 0 0 0 0
C (2,1) -0.000001 -0.000004 -0.000015 -0.000044
C (1,2) 0 0 0 0
C (0,3) 0.000001 0.000003 0.000008 0.000011
C (4,0) 5.937E-10 3.31171E-08 1.15318E-08 -6.40427E-08
C (3,1) 0 0 0 0
C (2,2) 8.75011E-09 6.0866E-08 3.60206E-10 1.22692E-07
C (1,3) 0 0 0 0
C (0,4) 1.08945E-08 1.98768E-08 5.29289E-08 -9.07935E-08
C (5,0) 0 0 0 0
C (4,1) 2.28753E-11 3.65088E-10 -5.0743E-12 -9.04166E-10
C (3,2) 0 0 0 0
C (2,3) 8.17038E-11 4.94301E-10 -3.52291E-10 -1.23492E-09
C (1,4) 0 0 0 0
C (0,5) 4.96918E-11 8.35365E-11 4.49451E-10 2.86075E-10
C (6,0) 1.82278E-14 -7.48314E-13 -5.81015E-13 -5.65052E-12
C (5,1) 0 0 0 0
C (4,2) 3.48485E-13 3.23228E-12 2.65138E-12 -1.76242E-11
C (3,3) 0 0 0 0
C (2,4) 6.44134E-13 1.66026E-12 9.29621E-13 1.78315E-11
C (1,5) 0 0 0 0
C (0,6) 5.98521E-13 6.81299E-13 7.83144E-12 4.06735E-11
C (7,0) 0 0 0 0
C (6,1) 3.47916E-16 -1.37135E-14 -1.7864E-14 -3.56175E-13
C (5,2) 0 0 0 0
C (4,3) 3.01841E-15 1.26051E-14 6.09128E-15 1.84398E-13
C (3,4) 0 0 0 0
C (2,5) 4.31301E-15 -1.09441E-15 -1.90044E-14 -2.93239E-13
C (1,6) 0 0 0 0
C (0,7) 4.04483E-15 4.12554E-15 7.8407E-14 -1.37302E-12

<Conditional values>
A11 = 0.00005
A12 = −0.00164987
A21 = 0.000755856
A22 = −0.00327485
Conditional expression (1) (A12-A11) × (A22-A21) = 6.85168E-06
Conditional expression (3) C ₁ (2,0) −C ₁ (0,2) = − 0.00170
Conditional expression (5) C ₂ (2,0) −C ₂ (0,2) = − 0.00403

FIG. 9 is a diagram showing distortion aberration of the second example. FIG. 10 is a diagram showing the aberration with respect to the e-line of the second embodiment in a spot diagram. Referring to FIG. 9, it can be seen that the distortion aberration of the second example is larger than the distortion aberration of the first example of FIG. Focusing on conditional expression (3) and conditional expression (5), the values corresponding to the conditional expressions in the second embodiment are compared with the values corresponding to the conditional expressions in the first embodiment. It turns out that it is near the limit value of the range of (5). That is, it can be seen that conditional expression (3) and conditional expression (5) shown in the present invention are conditions that give good optical performance. Referring to FIG. 10, in the second example, it can be seen that the spot size is sufficiently small at each of the image points S1 to S9, and the aberration is uniform and well corrected over the entire image plane IM. However, in the second embodiment, it can be seen that the spot size is also inferior to that of the first embodiment. Although only the e-line aberration is shown in the second embodiment, naturally, there is no chromatic aberration because the optical system is constituted only by the reflecting mirror. Since other aberrations are exactly the same as those of the e-line, illustration of the other wavelengths is omitted.

[Third embodiment]
FIG. 11 is a drawing schematically showing a cross-sectional configuration along the YZ plane of the reflective photographing lens according to the third example. FIG. 12 is a drawing schematically showing a cross-sectional configuration along the XZ plane of the reflective photographing lens according to the third example. The following table (3) lists the values of the specifications of the reflective photographic lens according to the third example.

Table (3)
<Optical member specifications>
Surface number X coordinate Y coordinate Z coordinate Tilt angle δ
1 0 0.000 0.000 -35.006 (CM1)
2 0 95.983 -34.947 -35.006 (CM2)
3 0 95.956 94.861 35.006 (CM3)
4 0 -0.044 59.859 35.006 (CM4)
5 0 0.000 150.000 0.000 (IM)

<Aspherical data>
Surface number 1 2 3 4
C (2,0) -0.0011707 -0.0014343 -0.00120246 -0.0012942
C (1,1) 0 0 0 0
C (0,2) -0.00120324 -0.00259378 -0.000204714 0.00103217
C (3,0) 0 0 0 0
C (2,1) -0.000002 -0.00001 0.000007 0.000026
C (1,2) 0 0 0 0
C (0,3) -0.000002 -0.000012 0.000007 0.000006
C (4,0) 1.4038E-10 1.28146E-09 -7.72694E-09 -1.43306E-07
C (3,1) 0 0 0 0
C (2,2) -5.31467E-09 -3.5286E-08 3.91641E-09 -2.74444E-07
C (1,3) 0 0 0 0
C (0,4) -2.95034E-09 2.43526E-08 9.11247E-08 2.3799E-08
C (5,0) 0 0 0 0
C (4,1) -2.55017E-12 1.30791E-10 7.95753E-11 3.51119E-09
C (3,2) 0 0 0 0
C (2,3) -9.36814E-12 6.07955E-10 3.987E-10 2.51964E-09
C (1,4) 0 0 0 0
C (0,5) 3.18353E-12 1.60101E-09 1.63349E-09 1.05336E-09
C (6,0) -4.8482E-15 -1.01114E-13 -2.58568E-13 -1.84073E-11
C (5,1) 0 0 0 0
C (4,2) -3.58513E-15 2.98906E-12 -4.70375E-13 -5.99341E-11
C (3,3) 0 0 0 0
C (2,4) 1.64494E-14 1.54416E-11 1.97836E-12 -4.91561E-11
C (1,5) 0 0 0 0
C (0,6) 5.40651E-14 1.80643E-11 1.14802E-11 -3.28741E-11
C (7,0) 0 0 0 0
C (6,1) 1.47029E-16 1.15768E-14 3.30961E-14 1.31027E-12
C (5,2) 0 0 0 0
C (4,3) -2.28175E-16 -6.37977E-15 -1.19453E-13 -3.5323E-13
C (3,4) 0 0 0 0
C (2,5) 1.90901E-16 1.13312E-13 -6.04779E-15 9.1323E-13
C (1,6) 0 0 0 0
C (0,7) 2.63936E-16 4.97123E-14 1.41463E-14 4.14852E-14

<Conditional values>
A11 = −0.00120324
A12 = −0.0011707
A21 = −0.00259378
A22 = −0.00327485
Conditional expression (1) (A12-A11) × (A22-A21) = − 2.2162E-08
Conditional expression (3) C ₁ (2,0) −C ₁ (0,2) = 3.2540E-05
Conditional expression (5) C ₂ (2,0) −C ₂ (0,2) = − 6.8107E-04

FIG. 13 is a diagram showing distortion aberration of the third example. FIG. 14 is a diagram showing the aberration with respect to the e-line of the third embodiment in a spot diagram. Referring to FIG. 13, it can be seen that in the third embodiment, the distortion is corrected well. Referring to FIG. 14, in the third example, it can be seen that the spot size is sufficiently small at each of the image points S1 to S9, and the aberration is uniform and well corrected over the entire image plane IM. Further, it can be seen that the shape of the spot at each of the image points S1 to S9 is almost symmetric, and the asymmetric aberration is well corrected. Although only the e-line aberration is shown in the third embodiment, naturally, there is no chromatic aberration because the optical system is constituted only by the reflecting mirror. Since other aberrations are exactly the same as those of the e-line, illustration of the other wavelengths is omitted.

[Fourth embodiment]
FIG. 15 is a drawing schematically showing a cross-sectional configuration along the YZ plane of the reflective photographing lens according to the fourth example. FIG. 16 is a diagram schematically illustrating a cross-sectional configuration along the XZ plane of the reflective photographing lens according to the fourth example. The following table (4) lists values of specifications of the reflective photographic lens according to the fourth example.

Table (4)
<Optical member specifications>
Surface number X coordinate Y coordinate Z coordinate Tilt angle δ
1 0 0.000 0.000 -35.306 (CM1)
2 0 95.741 -34.188 -35.306 (CM2)
3 0 95.825 94.450 35.306 (CM3)
4 0 0.111 60.350 35.306 (CM4)
5 0 0.000 150.000 0.000 (IM)

<Aspherical data>
Surface number 1 2 3 4
C (2,0) -0.00180778 -0.00414062 -0.000734668 0.001069
C (1,1) 0 0 0 0
C (0,2) -0.000245633 0.000505802 0.000430981 -0.00042515
C (3,0) 0 0 0 0
C (2,1) -0.000002 -0.000013 -0.000024 -0.000042
C (1,2) 0 0 0 0
C (0,3) 1.94065E-07 0.000002 0.000006 0.000004
C (4,0) -5.97205E-10 3.6242E-08 3.24732E-08 -4.06083E-08
C (3,1) 0 0 0 0
C (2,2) 4.06067E-10 2.88507E-08 -1.19099E-08 8.33902E-08
C (1,3) 0 0 0 0
C (0,4) 9.06598E-09 2.68536E-08 9.68667E-08 7.51517E-08
C (5,0) 0 0 0 0
C (4,1) 8.79733E-12 5.82158E-10 2.53997E-10 -5.0684E-11
C (3,2) 0 0 0 0
C (2,3) 3.64733E-11 7.1795E-10 -1.18784E-09 -2.31129E-10
C (1,4) 0 0 0 0
C (0,5) 3.55401E-11 1.46624E-10 6.73584E-10 -2.11633E-09
C (6,0) 9.58321E-15 -8.79973E-13 -1.04094E-12 -4.12621E-12
C (5,1) 0 0 0 0
C (4,2) 1.8504E-13 7.82866E-12 1.06987E-11 -1.42008E-12
C (3,3) 0 0 0 0
C (2,4) 2.5809E-13 4.26948E-12 -8.19613E-12 1.1516E-12
C (1,5) 0 0 0 0
C (0,6) 1.8672E-13 3.41701E-13 3.30594E-12 -5.00837E-11
C (7,0) 0 0 0 0
C (6,1) -3.73942E-17 -9.3625E-14 -1.12091E-13 -5.07602E-13
C (5,2) 0 0 0 0
C (4,3) 1.22107E-15 4.9016E-14 2.52999E-14 -3.09476E-14
C (3,4) 0 0 0 0
C (2,5) 1.81649E-15 8.73054E-15 -1.02161E-16 4.62751E-13
C (1,6) 0 0 0 0
C (0,7) 1.22301E-15 7.61707E-16 1.3265E-13 2.12789E-12

<Conditional values>
A11 = −0.00024563
A12 = −0.00180778
A21 = 0.000505802
A22 = −0.00414062
Conditional expression (1) (A12-A11) × (A22-A21) = 7.2584E-06
Conditional expression (3) C ₁ (2,0) −C ₁ (0,2) = − 0.00156
Conditional expression (5) C ₂ (2,0) −C ₂ (0,2) = − 0.00465

FIG. 17 is a diagram showing distortion aberration of the fourth example. FIG. 18 is a diagram showing the aberration with respect to the e-line of the fourth embodiment in a spot diagram. Referring to FIG. 17, the distortion aberration of the fourth embodiment is corrected relatively well, but is still larger than the distortion aberration of the first embodiment (FIG. 4). Even in the fourth embodiment, the values corresponding to the conditional expressions (3) and (5) are in the range of the conditional expressions (3) and (5) as compared to the first embodiment. This is thought to be due to the fact that it is close to the limit value. Referring to FIG. 18, it can be seen that in the fourth example, the spot size is sufficiently small at each of image points S1 to S9, and the aberration is uniform and well corrected over the entire image plane IM. Although only the e-line aberration is shown in the fourth embodiment, naturally, there is no chromatic aberration because the optical system is constituted only by the reflecting mirror. Since other aberrations are exactly the same as those of the e-line, illustration of the other wavelengths is omitted.

[Fifth embodiment]
FIG. 19 is a drawing schematically showing a cross-sectional configuration along the YZ plane of the reflective photographing lens according to the fifth example. FIG. 20 is a drawing schematically showing a cross-sectional configuration along the XZ plane of the reflective photographing lens according to the fifth example. Table 5 below lists values of specifications of the reflective photographic lens according to the fifth example.

Table (5)
<Optical member specifications>
Surface number X coordinate Y coordinate Z coordinate Tilt angle δ
1 0 0.000 0.000 -35.004 (CM1)
2 0 95.985 -34.951 -35.004 (CM2)
3 0 95.932 94.784 35.004 (CM3)
4 0 -0.059 59.812 35.004 (CM4)
5 0 0.000 150.000 0.000 (IM)

<Aspherical data>
Surface number 1 2 3 4
C (2,0) -0.00127362 -0.00182229 -0.00132999 -0.00120444
C (1,1) 0 0 0 0
C (0,2) -0.00144573 -0.00540615 -0.00103442 0.000836174
C (3,0) 0 0 0 0
C (2,1) -0.000003 -0.000017 0.000011 0.000037
C (1,2) 0 0 0 0
C (0,3) -0.000003 -0.000033 0.000005 0.000009
C (4,0) -2.80591E-10 -2.58974E-09 -8.91126E-09 -1.8627E-07
C (3,1) 0 0 0 0
C (2,2) -6.97191E-09 -8.92492E-08 1.89796E-08 -4.08741E-07
C (1,3) 0 0 0 0
C (0,4) -6.37061E-09 -1.36782E-07 4.18658E-08 -5.04794E-08
C (5,0) 0 0 0 0
C (4,1) -3.5712E-12 2.35514E-10 1.36294E-10 5.41726E-09
C (3,2) 0 0 0 0
C (2,3) -1.70892E-11 1.08873E-09 6.61535E-10 5.41695E-09
C (1,4) 0 0 0 0
C (0,5) -1.05145E-11 3.65758E-09 1.03609E-09 2.67397E-09
C (6,0) -7.04872E-15 -1.7055E-13 -3.43195E-13 -2.45502E-11
C (5,1) 0 0 0 0
C (4,2) -1.14998E-14 6.83177E-12 -4.27555E-13 -1.16339E-10
C (3,3) 0 0 0 0
C (2,4) -3.35864E-14 4.69618E-11 4.89101E-12 -1.25273E-10
C (1,5) 0 0 0 0
C (0,6) 9.97669E-15 1.05103E-10 1.06193E-11 -5.0543E-11
C (7,0) 0 0 0 0
C (6,1) -3.14649E-16 -2.88214E-14 4.20082E-15 1.03447E-12
C (5,2) 0 0 0 0
C (4,3) -5.54554E-16 -1.54481E-13 -7.0014E-14 8.16617E-13
C (3,4) 0 0 0 0
C (2,5) -2.65536E-16 1.62381E-13 1.33449E-14 1.65347E-12
C (1,6) 0 0 0 0
C (0,7) 1.63322E-16 1.24837E-12 5.77041E-14 1.99324E-13

<Conditional values>
A11 = −0.0014457
A12 = −0.0012736
A21 = −0.0054062
A22 = −0.0018223
Conditional expression (1) (A12-A11) × (A22-A21) = 6.1682E-07
Conditional expression (3) C ₁ (2,0) −C ₁ (0,2) = 0.00017
Conditional expression (5) C ₂ (2,0) −C ₂ (0,2) = 0.00358

FIG. 21 is a diagram showing distortion aberration of the fifth example. FIG. 22 is a diagram showing the aberration with respect to the e-line of the fifth embodiment in a spot diagram. Referring to FIG. 21, it can be seen that the fifth embodiment corrects the distortion aberration well. Referring to FIG. 22, in the fifth example, it can be seen that the spot size is sufficiently small at each of the image points S1 to S9, and the aberration is uniform and well corrected over the entire image plane IM. Further, it can be seen that the shape of the spot at each of the image points S1 to S9 is almost symmetric, and the asymmetric aberration is well corrected. Although only the e-line aberration is shown in the fifth embodiment, naturally, there is no chromatic aberration because the optical system is constituted only by the reflecting mirror. Since other aberrations are exactly the same as those of the e-line, illustration of the other wavelengths is omitted.

[Sixth embodiment]
FIG. 23 is a drawing schematically showing a cross-sectional configuration along the YZ plane of the reflective photographing lens according to the sixth example. FIG. 24 is a drawing schematically showing a cross-sectional configuration along the XZ plane of the reflective photographing lens according to the sixth example. Table 6 below lists values of specifications of the reflective photographic lens according to the sixth example.

Table (6)
<Optical member specifications>
Surface number X coordinate Y coordinate Z coordinate Tilt angle δ
1 0 0.000 0.000 -35.004 (CM1)
2 0 95.985 -34.951 -35.004 (CM2)
3 0 95.932 94.784 35.004 (CM3)
4 0 -0.059 59.812 35.004 (CM4)
5 0 0.000 150.000 0.000 (IM)

<Aspherical data>
Surface number 1 2 3 4
C (2,0) -0.000776879 -0.000730729 -0.000882748 -0.000773974
C (1,1) 0 0 0 0
C (2,0) -0.000508897 -0.000239765 -0.000340017 -0.000222311
C (3,0) 0 0 0 0
C (2,1) -0.000001 -0.000002 2.38109E-07 0.000003
C (1,2) 0 0 0 0
C (0,3) -0.000001 -0.000001 0.000001 0.000003
C (4,0) 6.28502E-10 3.32246E-09 -1.9622E-09 -3.55263E-08
C (3,1) 0 0 0 0
C (2,2) 1.03722E-09 5.01325E-09 1.30491E-09 -3.10011E-08
C (1,3) 0 0 0 0
C (0,4) 4.52142E-09 2.11261E-08 4.65079E-08 1.4864E-07
C (5,0) 0 0 0 0
C (4,1) 2.09849E-12 3.15038E-11 1.14905E-11 1.41191E-10
C (3,2) 0 0 0 0
C (2,3) 8.27181E-12 1.18652E-10 2.08145E-11 1.51379E-10
C (1,4) 0 0 0 0
C (0,5) 1.0314E-11 1.27697E-10 4.29179E-11 -1.74454E-09
C (6,0) 8.02544E-16 -2.16317E-14 -6.41101E-14 -2.41539E-12
C (5,1) 0 0 0 0
C (4,2) 1.87548E-14 2.32439E-13 -5.58573E-14 -3.54202E-12
C (3,3) 0 0 0 0
C (2,4) 6.58928E-14 6.61561E-13 4.92869E-13 2.0133E-12
C (1,5) 0 0 0 0
C (0,6) 3.48619E-14 -1.14263E-13 -2.85204E-14 -4.50035E-11
C (7,0) 0 0 0 0
C (6,1) 3.85956E-16 6.45361E-15 1.91907E-14 7.17817E-13
C (5,2) 0 0 0 0
C (4,3) 4.13214E-17 -1.0478E-15 -1.65583E-14 -5.85761E-13
C (3,4) 0 0 0 0
C (2,5) 1.07595E-16 -2.22434E-15 -3.00808E-15 -2.72507E-14
C (1,6) 0 0 0 0
C (0,7) 1.31E-16 -3.64446E-15 1.77322E-14 1.08759E-12

<Conditional values>
A11 = −0.0005089
A12 = −0.00077688
A21 = −0.00023977
A22 = −0.00073073
Conditional expression (1) (A12-A11) × (A22-A21) = 1.3157E-07
Conditional expression (3) C ₁ (2,0) −C ₁ (0,2) = − 0.00027
Conditional expression (5) C ₂ (2,0) −C ₂ (0,2) = − 0.00049

FIG. 25 is a diagram showing distortion aberration of the sixth example. FIG. 26 is a diagram showing the aberration with respect to the e-line of the sixth embodiment in a spot diagram. Referring to FIG. 25, it can be seen that in the sixth example, the distortion is corrected well. Referring to FIG. 26, it can be seen that in the sixth example, the spot size is sufficiently small at each of the image points S1 to S9, and the aberration is uniform and well corrected over the entire image plane IM. Further, it can be seen that the shape of the spot at each of the image points S1 to S9 is almost symmetric, and the asymmetric aberration is well corrected. Although only the e-line aberration is shown in the sixth embodiment, naturally, there is no chromatic aberration because the optical system is constituted only by the reflecting mirror. Since other aberrations are exactly the same as those of the e-line, illustration of the other wavelengths is omitted.

[Seventh embodiment]
FIG. 27 is a diagram schematically illustrating a cross-sectional configuration along the YZ plane in the infinitely focused state of the reflective photographing lens according to the seventh example. FIG. 28 is a diagram schematically illustrating a cross-sectional configuration along the XZ plane in the infinitely focused state of the reflective photographing lens according to the seventh example. FIG. 29 is a diagram schematically showing a cross-sectional configuration along the YZ plane in the first distance focusing state (object distance D = 89505.0 mm) of the reflective photographing lens according to the seventh example. FIG. 30 is a drawing schematically showing a cross-sectional configuration along the YZ plane in the second distance focusing state (object distance D = 288858.5 mm) of the reflective photographing lens according to the seventh example.

In the seventh embodiment, a focusing optical system FS for focusing an object with respect to the image plane IM is attached in the optical path between the fourth reflecting mirror CM4 and the image plane IM. The focusing optical system FS includes three lenses L1, L2, and L3 that can move integrally along the Z direction parallel to the first reference axis AXe. The lens L1 is a meniscus lens having a convex surface R11 facing the fourth reflecting mirror CM4 and a concave surface R12 facing the image surface IM. Similarly, the lenses L2 and L3 are meniscus lenses having convex surfaces R21 and R31 facing the fourth reflecting mirror CM4 and concave surfaces R22 and R32 facing the image surface IM.

Lenses L1, L2, and L3 are formed of different optical materials. In the column of glass material data in Table (7), nC represents the refractive index of the optical material with respect to the C line (wavelength: 656.27 nm), nd represents the refractive index of the optical material with respect to the d line (wavelength: 587.56 nm), ne Is the refractive index of the optical material for the e-line (reference wavelength: 546.07 nm), nF is the refractive index of the optical material for the F-line (wavelength: 486.13 nm), and ng is for the g-line (wavelength: 435.83 nm). The refractive index of the optical material is shown. In the seventh embodiment, as in the first to sixth embodiments, a plane parallel plate as a protective glass can be disposed at a required position on the object side of the first reflecting mirror CM1.

In the column of the optical member specifications in Table (7), the surface number indicates the order of the surfaces from the object side along the path of light traveling from the object at infinity to the image plane IM. That is, the first surface is the reflecting surface of the first reflecting mirror CM1, the second surface is the reflecting surface of the second reflecting mirror CM2, the third surface is the reflecting surface of the third reflecting mirror CM3, and the fourth surface. Is the reflecting surface of the fourth reflecting mirror CM4, the fifth surface is the entrance surface R11 of the lens L1, the sixth surface is the exit surface R12 of the lens L1, and the seventh surface is the entrance surface R21 of the lens L2. The eighth surface is the exit surface R22 of the lens L2, the ninth surface is the entrance surface R31 of the lens L3, the tenth surface is the exit surface R32 of the lens L3, and the eleventh surface is the image plane IM.

In addition, in the column of the optical member specifications in Table (7), in addition to the data of the first reflecting mirror CM1 to the fourth reflecting mirror CM4, X at the center of each surface of the lenses L1 to L3 in the infinitely focused state A coordinate (unit: mm), a Y coordinate (unit: mm), a Z coordinate (unit: mm), and an inclination angle δ (unit: degree) are shown. The lenses L1 to L3 have an inclination angle δ of 0 degrees and are arranged in a normal posture without being inclined with respect to the XY plane. The column of lens surface data in Table (7) indicates the radius of curvature (unit: mm) r of each surface of the lenses L1 to L3. Here, the radius of curvature r of the lens surface with the convex surface facing the light incident side is positive.

In the column of the amount of movement of the focusing optical system in Table (7), the infinite focusing of the focusing optical system FS in the first distance focusing state is based on the position of the focusing optical system FS in the infinite focusing state. A movement amount ΔD1 (unit: mm) from the in-focus state and a movement amount ΔD2 (unit: mm) from the infinitely focused state of the focusing optical system FS in the second distance in-focus state are shown. The values of the movement amounts ΔD1 and ΔD2 are positive values when moving toward the image plane IM. Table 7 below lists values of specifications of the reflective photographic lens according to the seventh example. The notation in Table (7) is the same in Table (8).

Table (7)
<Glass data>
nC nd ne nF ng
L1 1.513855 1.51633 1.518251 1.521905 1.526214
L2 1.747295 1.755199 1.761671 1.774745 1.791497
L3 1.544572 1.548141 1.550984 1.556544 1.563351

<Optical member specifications>
Surface number X coordinate Y coordinate Z coordinate Tilt angle δ
1 0 0.00 -60.00 -37.87 (CM1)
2 0 190.00 -108.32 -37.87 (CM2)
3 0 190.00 108.32 37.87 (CM3)
4 0 0.00 60.00 37.87 (CM4)
5 0 0.00 100.00 0.00 (L1; R11)
6 0 0.00 103.00 0.00 (L1; R12)
7 0 0.00 108.42 0.00 (L2; R21)
8 0 0.00 111.42 0.00 (L2; R22)
9 0 0.00 113.42 0.00 (L3; R31)
10 0 0.00 121.42 0.00 (L3; R32)
11 0 0.00 330.00 0.00 (IM)

<Aspherical data>
Surface number 1 2 3 4
C (2,0) -4.11103.E-04 -2.90903.E-04 -5.62264.E-04 -5.40325.E-04
C (1,1) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (0,2) -2.67792.E-04 -2.90085.E-04 -5.06794.E-04 -5.49152.E-04
C (3,0) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (2,1) -1.41239.E-07 -2.05955.E-07 8.05499.E-07 2.26277.E-06
C (1,2) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (0,3) 1.83465.E-07 9.89000.E-07 1.17666.E-06 3.03799.E-06
C (4,0) 3.54753.E-10 1.21553.E-09 -3.50594.E-10 -5.31580.E-09
C (3,1) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (2,2) 2.64023.E-10 1.05016.E-09 -3.52589.E-09 -2.63365.E-08
C (1,3) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (0,4) 1.09184.E-09 5.46395.E-09 2.56841.E-09 -1.28230.E-08
C (5,0) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (4,1) 1.08935.E-13 -1.19586.E-12 -3.19791.E-12 4.67743.E-12
C (3,2) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (2,3) 7.82206.E-13 2.07412.E-12 -8.68229.E-12 7.91363.E-11
C (1,4) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (0,5) 3.30595.E-12 1.78111.E-11 1.93776.E-11 5.83881.E-11
C (6,0) -3.17881.E-15 -4.31447.E-14 -7.74547.E-14 -1.00604.E-12
C (5,1) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (4,2) -3.05460.E-15 -6.67652.E-14 -9.51359.E-14 -1.56024.E-12
C (3,3) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (2,4) -1.30062.E-15 -5.37642.E-14 -1.43180.E-13 -1.75096.E-12
C (1,5) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (0,6) 6.70080.E-15 1.77774.E-14 6.25179.E-14 -6.87357.E-13
C (7,0) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (6,1) 1.03268.E-16 1.19194.E-15 2.15616.E-15 5.33170.E-14
C (5,2) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (4,3) 9.05481.E-18 -3.04949.E-16 -4.00197.E-16 -1.23283.E-14
C (3,4) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (2,5) 2.68577.E-17 2.32651.E-16 -9.01643.E-17 2.74645.E-14
C (1,6) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (0,7) 2.34479.E-18 -1.49564.E-16 1.11004.E-16 -4.18193.E-15

<Lens surface data>
Lens surface r
R11 146.133
R12 70.138
R21 63.577
R22 59.261
R31 63.364
R32 99.301

<Movement distance of focusing optical system>
First distance focus state Second distance focus state ΔD1 ΔD2
23.18 85.3

<Conditional values>
A11 = −0.00026779
A12 = −0.0004111
A21 = −0.00029008
A22 = −0.0002909
Conditional expression (1) (A12-A11) × (A22-A21) = 1.1734E-10
Conditional expression (3) C ₁ (2,0) −C ₁ (0,2) = − 0.00014
Conditional expression (5) C ₂ (2,0) −C ₂ (0,2) = − 8.1877E-07

FIG. 31 is a diagram showing the aberration with respect to the e-line in an infinitely focused state according to the seventh embodiment in a spot diagram. FIG. 32 is a diagram showing aberrations with respect to the e-line in the first distance in-focus state according to the seventh embodiment in a spot diagram. FIG. 33 is a diagram showing the aberration with respect to the e-line in the second distance in-focus state in the seventh embodiment in a spot diagram. FIG. 34 is a diagram showing the aberration with respect to g-line in the infinite focus state in the seventh embodiment in a spot diagram. FIG. 35 is a diagram showing aberrations with respect to g-line in the first distance in-focus state according to the seventh embodiment in a spot diagram. FIG. 36 is a spot diagram showing aberrations with respect to g-line in the second distance in-focus state in the seventh embodiment.

31 to 36, in the seventh example, it can be seen that the spot size is sufficiently small at each of the image points S1 to S9, and the aberration is uniform and well corrected over the entire image plane IM. Further, it can be seen that the shape of the spot at each of the image points S1 to S9 is almost symmetric, and the asymmetric aberration is well corrected. Further, the e-line and the g-line show almost the same aberration, and it can be seen that almost no chromatic aberration occurs.

[Eighth embodiment]
FIG. 37 is a drawing schematically showing a cross-sectional configuration along the YZ plane in the infinitely focused state of the reflective photographing lens according to the eighth example. FIG. 38 is a diagram schematically illustrating a cross-sectional configuration along the XZ plane in the infinitely focused state of the reflective photographing lens according to the eighth example. FIG. 39 is a diagram schematically illustrating a cross-sectional configuration along the YZ plane in the first distance focusing state (object distance D = 89989.75 mm) of the reflective photographing lens according to the eighth example. FIG. 40 is a diagram schematically illustrating a cross-sectional configuration along the YZ plane in the second distance focusing state (object distance D = 29078.91 mm) of the reflective photographing lens according to the eighth example.

In the eighth embodiment, a focusing optical system FS and a lens L4 for focusing an object on the image plane IM are attached in the optical path between the fourth reflecting mirror CM4 and the image plane IM. The focusing optical system FS includes three lenses L1, L2, and L3 that can move integrally along the Z direction parallel to the first reference axis AXe. The lens L1 is a meniscus lens having a convex surface R11 facing the fourth reflecting mirror CM4 and a concave surface R12 facing the image surface IM. Similarly, the lenses L2, L3, and L4 are meniscus lenses having convex surfaces R21, R31, and R41 facing the fourth reflecting mirror CM4 and concave surfaces R22, R32, and R42 facing the image surface IM.

Lenses L1, L2, and L3 are formed of different optical materials. The lenses L2 and L4 are made of the same optical material. In the eighth embodiment, as in the first to seventh embodiments, a plane parallel plate as a protective glass can be disposed at a required position on the object side of the first reflecting mirror CM1.

In the column of optical member specifications in Table (8), the surface number indicates the order of the surfaces from the object side along the path of light traveling from the object at infinity to the image plane IM. That is, the first surface is the reflecting surface of the first reflecting mirror CM1, the second surface is the reflecting surface of the second reflecting mirror CM2, the third surface is the reflecting surface of the third reflecting mirror CM3, and the fourth surface. Is the reflecting surface of the fourth reflecting mirror CM4, the fifth surface is the entrance surface R11 of the lens L1, the sixth surface is the exit surface R12 of the lens L1, and the seventh surface is the entrance surface R21 of the lens L2. The eighth surface is the exit surface R22 of the lens L2, the ninth surface is the entrance surface R31 of the lens L3, the tenth surface is the exit surface R32 of the lens L3, and the eleventh surface is the entrance surface R41 of the lens L4. The twelfth surface is the exit surface R42 of the lens L4, and the thirteenth surface is the image surface IM. Table 8 below lists values of specifications of the reflective photographic lens according to the eighth example.

Table (8)
<Glass data>
nC nd ne nF ng
L1 1.513855 1.51633 1.518251 1.521905 1.526214
L2 1.747295 1.755199 1.761671 1.774745 1.791497
L3 1.544572 1.548141 1.550984 1.556544 1.563351
L4 1.747295 1.755199 1.761671 1.774745 1.791497

<Optical member specifications>
Surface number X coordinate Y coordinate Z coordinate Tilt angle δ
1 0 0.00 0.00 -37.87 (CM1)
2 0 190.00 -48.32 -37.87 (CM2)
3 0 190.00 168.32 37.86 (CM3)
4 0 0.00 120.00 37.87 (CM4)
5 0 0.00 160.00 0.00 (L1; R11)
6 0 0.00 163.00 0.00 (L1; R12)
7 0 0.00 166.50 0.00 (L2; R21)
8 0 0.00 169.50 0.00 (L2; R22)
9 0 0.00 171.50 0.00 (L3; R31)
10 0 0.00 179.50 0.00 (L3; R32)
11 0 0.00 301.17 0.00 (L4; R41)
12 0 0.00 306.17 0.00 (L4; R42)
13 0 0.00 403.35 0.00 (IM)

<Aspherical data>
Surface number 1 2 3 4
C (2,0) -4.13576.E-04 -3.02491.E-04 -5.47057.E-04 -5.12766.E-04
C (1,1) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (0,2) -2.64338.E-04 -2.96466.E-04 -5.13891.E-04 -5.62089.E-04
C (3,0) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (2,1) -1.44160.E-07 -2.14044.E-07 7.88214.E-07 2.15862.E-06
C (1,2) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (0,3) 1.17758.E-07 6.39684.E-07 8.97700.E-07 2.54277.E-06
C (4,0) 3.19320.E-10 1.11546.E-09 -3.29742.E-10 -4.21238.E-09
C (3,1) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (2,2) 2.79640.E-10 1.00278.E-09 -2.83353.E-09 -2.11459.E-08
C (1,3) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (0,4) 8.90408.E-10 4.47692.E-09 1.60168.E-09 -9.41785.E-09
C (5,0) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (4,1) 1.33095.E-13 -8.14070.E-13 -2.96567.E-12 -7.90202.E-13
C (3,2) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (2,3) 9.11951.E-13 3.21726.E-12 -5.11467.E-12 5.46120.E-11
C (1,4) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (0,5) 2.64402.E-12 1.57228.E-11 1.30720.E-11 3.43403.E-11
C (6,0) -2.25370.E-15 -3.25864.E-14 -5.91165.E-14 -7.83898.E-13
C (5,1) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (4,2) -3.06633.E-17 -3.15993.E-14 -5.61162.E-14 -1.11683.E-12
C (3,3) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (2,4) 7.98228.E-16 -3.03125.E-14 -9.31812.E-14 -1.29872.E-12
C (1,5) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (0,6) 4.46254.E-15 1.52575.E-14 3.14162.E-14 -6.03439.E-13
C (7,0) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (6,1) 9.13054.E-17 1.09799.E-15 1.85503.E-15 3.98272.E-14
C (5,2) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (4,3) 2.65533.E-17 -1.64895.E-17 -1.07597.E-16 -6.41046.E-15
C (3,4) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (2,5) 2.81231.E-17 1.88233.E-16 5.71596.E-17 1.87606.E-14
C (1,6) 0.0.E + 00 0.0.E + 00 0.0.E + 00 0.0.E + 00
C (0,7) -2.24523.E-19 -1.03917.E-16 5.08692.E-17 -8.80201.E-16

<Lens surface data>
Lens surface r
R11 206.244
R12 80.941
R21 123.848
R22 109.753
R31 81.127
R32 181.925
R41 60.948
R42 56.398

<Movement distance of focusing optical system>
First distance focus state Second distance focus state ΔD1 ΔD2
30.26 116.67

<Conditional values>
A11 = −0.00026434
A12 = −0.00041358
A21 = −0.00029647
A22 = −0.00030249
Conditional expression (1) (A12-A11) × (A22-A21) = 8.9921E-10
Conditional expression (3) C ₁ (2,0) −C ₁ (0,2) = − 1.4924E-04
Conditional expression (5) C ₂ (2,0) −C ₂ (0,2) = − 6.0253E-06

FIG. 41 is a diagram showing the aberration with respect to the e-line in the infinite focus state in the eighth embodiment in a spot diagram. FIG. 42 is a diagram showing the aberration with respect to the e-line in the first distance focusing state according to the eighth embodiment in a spot diagram. FIG. 43 is a diagram showing the aberration with respect to the e-line in the second distance in-focus state in the eighth embodiment in a spot diagram. FIG. 44 is a spot diagram showing aberrations with respect to g-line in the infinitely focused state according to the eighth embodiment. FIG. 45 is a diagram showing the aberration with respect to g-line in the first distance in-focus state according to the eighth embodiment in a spot diagram. FIG. 46 is a spot diagram showing aberrations with respect to g-line in the second distance in-focus state in the eighth embodiment.

Referring to FIGS. 41 to 46, in the eighth embodiment, as in the seventh embodiment, the spot size is sufficiently small at each image point S1 to S9, and the aberration is uniform and good over the entire image plane IM. You can see that it has been corrected. Further, it can be seen that the shape of the spot at each of the image points S1 to S9 is almost symmetric, and the asymmetric aberration is well corrected. Further, the e-line and the g-line show almost the same aberration, and it can be seen that almost no chromatic aberration occurs.

As described above, in the present embodiment, the occurrence of asymmetric aberration is satisfactorily suppressed despite the fact that it is a rotationally asymmetric optical system called a decentered optical system. In the present embodiment, an optical system is realized in which chromatic aberration is sufficiently reduced over a relatively wide image plane of 36 mm × 24 mm with respect to light in the visible wavelength band. In addition, weight reduction can be achieved by forming a reflecting mirror and a refractive member (lens etc.) with resin.

In addition, the telephoto lens is generally very large, and there is a merit of downsizing even in the case of transportation and storage. In the case of the present invention, as can be easily imagined from FIG. 2 showing the optical path diagram of the first embodiment, the space between the reflecting mirrors is larger than that of the refractive optical system. For example, the second reflecting mirror CM2 in FIG. A structure that can be divided from the third reflecting mirror CM3, or a structure that can be bent, and a structure that can be further reduced in size during transportation and storage are also possible.

In the above description, the present invention is applied to, for example, a reflective photographic lens used in a camera. However, the present invention is not limited to this, and the present invention can be similarly applied to other appropriate image devices.

The disclosure of the following priority application is hereby incorporated by reference.
Japanese Patent Application 2012 No. 260424 (filed on November 29, 2012)

CM1 First reflecting mirror CM2 Second reflecting mirror CM3 Third reflecting mirror CM4 Fourth reflecting mirror L1, L2, L3, L4 Lens IM Image plane AXa, AXb, AXc, AXd, AXe Reference axis

Claims (9)

1. A reflective photographic lens,
   In order from the object side, a first reflecting mirror, a second reflecting mirror, a third reflecting mirror, and a fourth reflecting mirror are provided, and light from the object is reflected by the first reflecting mirror, the second reflecting mirror, and the first reflecting mirror. Arranged so as to form an object image on a predetermined image plane after being sequentially reflected by the three reflecting mirrors and the fourth reflecting mirror,
   The first to fourth reflecting mirrors have a rotationally asymmetric aspherical reflecting surface and include a first reference axis defined by a normal passing through the center of the image surface and Configured symmetrically with respect to a vertical reference plane,
   The first reflecting mirror has a concave surface with respect to the incident direction of light,
   The first reflecting mirror and the second reflecting mirror are inclined in the same direction with respect to an orthogonal plane orthogonal to the first reference axis, and the third reflecting mirror and the fourth reflecting mirror are in the first direction relative to the orthogonal plane. It is tilted in the opposite direction of one reflector,
   The reflection photographic lens, wherein the second reflecting mirror and the third reflecting mirror are arranged eccentrically on the same side with respect to the first reflecting mirror in the reference plane.
2. The reflective photographic lens according to claim 1,
   A center curvature of an intersection curve between the reflecting surface of the first reflecting mirror and the reference surface is A11, and a surface orthogonal to the reference surface including a normal passing through the center of the reflecting surface of the first reflecting mirror and the first surface The center curvature of the intersecting curve with the reflecting surface of one reflecting mirror is A12, the center curvature of the intersecting curve between the reflecting surface of the second reflecting mirror and the reference surface is A21, and the center of the reflecting surface of the second reflecting mirror is A21. When the center curvature of the intersection curve of the surface perpendicular to the reference surface including the normal passing through and the reflecting surface of the second reflecting mirror is A22,
   (A12-A11) × (A22-A21)> − 0.00000005 (1)
   Reflective lens that satisfies the above conditions.
3. The reflective photographic lens according to claim 1 or 2,
   The rotationally asymmetric aspherical surface of the first reflecting mirror has a z-direction as a normal direction at the origin of a tangential plane of the aspherical surface, a y-direction as a direction of an intersection between the tangential plane and the reference plane, and the tangential plane. and a direction perpendicular to the y direction and x-direction at the inner, the amount of sag in the z-direction of the aspherical surface and s, m and n is a natural number including 0, monomial x ^m · y coefficients ⁿ C ₁ (m, n) is a reflection photographic lens that is defined by the following expression (2) and satisfies the following conditional expression (3).
   

   
4. The reflection photographing lens according to any one of claims 1 to 4,
   The rotationally asymmetric aspherical surface of the second reflecting mirror has a normal direction at the origin of the tangential plane of the aspherical surface as a z direction, a direction of an intersection line between the tangential plane and the reference plane as a y direction, and the tangential plane. and a direction perpendicular to the y direction and x-direction at the inner, the amount of sag in the z-direction of the aspherical surface and s, m and n is a natural number including 0, monomial x coefficients of ^m · y ⁿ C ₂ (m, n), a reflective photographic lens that is defined by the following expression (4) and satisfies the following conditional expression (5).
   

   
5. The reflection photographing lens according to any one of claims 1 to 4,
   A reflection photographic lens having at least one movable lens and further comprising a focusing optical system for focusing the object on the image plane.
6. The reflective photographic lens according to claim 5.
   The focusing optical system is a reflection photographing lens disposed in an optical path between the fourth reflecting mirror and the image plane.
7. In the reflective photographic lens according to claim 5 or 6,
   The focusing optical system includes a plurality of lenses that can move integrally along a direction parallel to the first reference axis.
8. The reflection photographing lens according to any one of claims 1 to 7,
   The first reflecting mirror to the fourth reflecting mirror are arranged so that an object plane defined as a plane optically conjugate with the image plane at the position of the object is parallel to the image plane. lens.
9. The reflection photographing lens according to any one of claims 1 to 8,
   In the first reflecting mirror to the fourth reflecting mirror, light incident in parallel with the first reference axis with respect to the center of the reflecting surface of the first reflecting mirror is converted into the second reflecting mirror and the third reflecting mirror. And a reflective photographic lens arranged so as to be perpendicularly incident on the center of the image plane through the fourth reflecting mirror.

Images