JP2000227554A - Image-formation optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-performance and inexpensive image-formation optical system constituted of small number of optical devices by arranging a prism member consisting of an eccentric prism and compensating eccentric aberration each other by the object-side part and the image-side part of the prism member. SOLUTION: This image-formation optical system is provided with the prism member 10 formed of medium whose refractive index (n) is larger than 1. As for the member 10; a reflecting optical path is formed of the 1st incident surface 11, the 1st reflection surface 12 and the 2nd reflection surface 13, luminous flux is rotated along a triangular optical path by the 3rd reflection surface 14, the 4th reflection surface 15 and the 1st emitting surface 16, and a crossing optical path is formed by an optical path made incident on the 3rd reflection surface 14 and an optical path leading to the 1st emitting surface 16 from the 4th reflection surface 15. The 1st and the 2nd reflection surfaces 12 and 13 or the 3rd and the 4th reflection surfaces 14 and 15 have curved surface shape by which power is given to the luminous flux and which is constituted of rotationally asymmetric surface shape compensating aberration caused by eccentricity. An intermediate image surface 4 is formed in the optical path between the 1st and the 4th reflection surfaces 12 and 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming optical system, and more particularly, to a reflecting surface for an optical device using a small image pickup device such as a video camera, a digital still camera, a film scanner, and an endoscope. The present invention relates to a decentered optical system having power.

[0002]

2. Description of the Related Art In recent years, in image forming optical systems for video cameras, digital still cameras, film scanners, endoscopes, etc., the optical systems themselves have become smaller and lighter with the downsizing of image pickup devices.
Cost reduction is required.

However, in a general rotationally symmetric coaxial optical system,
Since the thickness of the optical system is such that the optical elements are arranged in the direction of the optical axis, there is a limit in miniaturization. At the same time, in order to correct chromatic aberration caused by using a rotationally symmetric refractive lens, an increase in the number of lenses is inevitable, and cost reduction is difficult. Therefore, recently, there has been proposed an optical system in which the size of the optical system is reduced by giving power to a reflecting surface in which chromatic aberration does not occur and folding the optical path in the optical axis direction.

Japanese Unexamined Patent Publication No. Hei 7-333505 proposes that the optical path be folded by applying power to the eccentric reflecting surface to reduce the thickness of the optical system.
The number of constituent optical members is as many as five, and the actual optical performance is unknown. Also, no mention is made of the shape of the reflection surface.

In Japanese Patent Application Laid-Open Nos. 8-292371, 9-5650 and 9-90229,
An optical system is shown in which one or a plurality of mirrors are formed as a single member to form a block, thereby folding an optical path and relaying an image inside the optical system to form a final image. However, in these examples, the number of reflections is increased to relay the image, and the surface accuracy error and the eccentricity accuracy error are integrated and transferred. . At the same time, the volume of the entire optical system for relaying an image is undesirably increased.

Japanese Patent Application Laid-Open No. 9-222563 discloses an example in which a plurality of prisms are used. However, this is not preferable because relaying an image leads to an increase in cost and an increase in the size of an optical system. Also, Japanese Patent Application Laid-Open No. 9-21133
No. 1 discloses an example in which the optical path is folded by using one prism to reduce the size of the optical system, but the aberration is not sufficiently corrected.

[0007] Further, in JP-A-8-292368, JP-A-8-292372, JP-A-9-222561, JP-A-9-258105 and JP-A-9-258106, all are examples of zoom lenses. is there. However, also in these examples, since the image is relayed inside the prism, the number of reflections is large, and the surface accuracy error and the eccentricity error of the reflecting surface are accumulated and transferred, which is not preferable. At the same time, an increase in the size of the optical system is inevitable, which is not preferable.

Japanese Unexamined Patent Application Publication No. 10-20196 discloses a prism having a negative power on the object side with a diaphragm interposed between a positive front group of a positive / negative two-group zoom lens and a positive power prism on the image side. This is an example of the configuration. Also, the positive front group composed of the negative prism and the positive prism is divided into two,
There is also disclosed an example in which a negative, positive, and negative three-group zoom lens is configured. However, in the prism used in these examples, the two transmission surfaces and the two reflection surfaces are independent surfaces, so that it is necessary to secure the space, and at the same time, the imaging surface is large, which is a Leica size film format. In addition, the size of the prism itself is inevitable. In addition, since the image side is not telecentric, it is difficult to cope with an image pickup device such as a CCD. In addition, in any of the examples of the zoom lens, since the magnification is changed by moving the prism, the eccentricity of the reflection surface becomes stricter to maintain the performance in all the magnification regions, and the cost increases. Have a problem.

[0009]

When a desired refractive power is to be obtained by a general refractive optical system, chromatic aberration occurs at the boundary surface due to the chromatic dispersion characteristics of the optical element. In order to correct this and to correct other ray aberrations, the refractive optical system has a problem that many components are required and the cost is high. At the same time, since the optical path is straight along the optical axis, the entire optical system becomes longer in the optical axis direction, resulting in a problem that the imaging device becomes larger.

Further, in the decentered optical system as described in the prior art, an image is formed if the aberration of the formed image is properly corrected, and especially if the rotationally asymmetric distortion is not properly corrected. There is a problem that a figure or the like is distorted and cannot be reproduced in a correct shape.

Further, when a reflecting surface is used in the decentering optical system, the sensitivity of the decentering error is doubled as compared with that of the refracting surface. As the number of reflections is increased, the decentering error is integrated and transferred as the number of reflections increases. There is also a problem that the manufacturing accuracy such as the surface accuracy and the eccentricity of the reflection surface and the assembly accuracy are severe.

The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a high-performance, low-cost imaging optical system with a small number of optical elements. .

It is another object of the present invention to provide a high-performance imaging optical system which is reduced in size and thickness by folding an optical path using a reflection surface having a small number of reflections.

[0014]

According to the present invention, there is provided an image forming optical system having a positive refractive power as a whole for forming an object image, wherein the image forming optical system comprises:
A prism member formed of a medium having a refractive index (n) greater than 1 (n> 1), wherein the prism member causes a light beam to enter at least into the prism from the object side;
An incident surface, first to fourth reflecting surfaces for reflecting the light beam inside the prism, and a first exit surface for emitting the light beam outside the prism; the first incident surface and the second reflecting surface; Are configured such that the transmission function and the reflection function are shared by one surface by the total reflection function, and the first incidence surface, the first reflection surface, and the second reflection surface form a folded optical path. , The third reflecting surface, the fourth reflecting surface, and the first
The exit surface rotates the luminous flux along the triangular optical path,
In addition, the first reflection surface and the second reflection surface are arranged so that an intersection light path is formed by an optical path incident on the third reflection surface and an optical path guided from the fourth reflection surface to the first exit surface. At least one of the surfaces has a curved surface shape that gives power to the light beam, and the curved surface shape has a rotationally asymmetric surface shape that corrects an aberration generated by eccentricity,
In addition, at least one of the third reflection surface and the fourth reflection surface has a curved surface shape that gives power to a light beam, and the curved surface shape has a rotationally asymmetric surface shape that corrects aberration caused by eccentricity. And an intermediate image surface is formed in an optical path between the first reflection surface and the fourth reflection surface, and a stop is arranged on the incident side of the first incident surface, and The on-axis interval to the first incident surface is ER,
When the eccentric direction of all the optical systems is the Y-axis direction, the plane parallel to the axial principal ray is the YZ plane, and the direction orthogonal to the YZ plane is the X direction, Assuming that the focal length is Fy, ER / Fy ≦ 2.0 (1) is satisfied, and at least one of the following nine conditions is satisfied. It is characterized by the following. 0.1 <Px1-1 / | Px | <3 ... -0.5 <Py1-1 / | Py | <3 ...- 2 <Px1-2 / | Px | <1 ...- 1 <Py1-2 / | Py | <1 ...- 0.5 <Px2-1 / | Px | <1.5 ...- 0.5 <Py2-1 / | Py | <1.5 ... -1 <Px2-2 / | Px | <1.5 ...- 1 <Py2-2 / | Py | <1.5 ...- 1 <Px2 / Py2 <5 ... All optics The power of the system in the X direction is Px, the power in the Y direction is Py, and the power in the X direction of the first, second, third, and fourth reflecting surfaces is Px1-1, Px1-.
2, Px2-1, Px2-2, and the power in the Y direction
y1-1, Py1-2, Py2-1, Py2-2, and (Px2-1
+ Px2-2) / (Py2-1 + Py2-2) to Px2 / P
y2.

Hereinafter, the reason and operation of the above-described configuration in the present invention will be described in order. In order to achieve the above object, an image forming optical system according to the present invention is an image forming optical system having a positive refractive power as a whole for forming an object image, wherein the image forming optical system has a refractive index (n) of 1 or more. Having a large (n> 1) medium, the prism member comprising:
From the object side, at least a first incident surface on which the light beam enters the prism, and a first incident surface for reflecting the light beam within the prism.
To a fourth reflecting surface, and a first emitting surface for emitting a light beam outside the prism, wherein the first incident surface and the second reflecting surface perform one transmission operation and one reflection operation by a total reflection operation. The first reflection surface, the first reflection surface, and the second reflection surface form a folded optical path, and the third reflection surface, the fourth reflection surface, and the second reflection surface. The first exit surface rotates a light beam along a triangular optical path, and an optical path incident on the third reflective surface and the fourth optical surface.
An intersecting optical path is formed by an optical path guided from the reflection surface to the first exit surface, and at least one of the first reflection surface and the second reflection surface is a curved surface that gives power to a light beam. And the curved surface shape is constituted by a rotationally asymmetric surface shape that corrects aberrations caused by eccentricity, and at least one of the third reflection surface and the fourth reflection surface is formed into a light beam. It has a curved surface shape that gives power, and the curved surface shape is constituted by a rotationally asymmetric surface shape that corrects aberrations caused by eccentricity, and is intermediate in an optical path between the first reflection surface and the fourth reflection surface. An imaging optical system, which is configured to form an image plane.

A refractive optical element such as a lens can have power only by giving a curvature to its boundary surface. Therefore, when a light beam is refracted at the boundary surface of the lens, chromatic aberration due to the chromatic dispersion characteristics of the refractive optical element is inevitably generated. As a result, another refractive optical element is generally added for the purpose of correcting chromatic aberration.

On the other hand, a reflecting optical element such as a mirror or a prism does not generate chromatic aberration in principle even if its reflecting surface has power, and another optical element is used only for the purpose of correcting chromatic aberration. No need to add. Therefore, in the optical system using the reflective optical element, the number of constituent optical elements can be reduced from the viewpoint of chromatic aberration correction, as compared with the optical system using the refractive optical element.

At the same time, since the reflection optical system using the reflection optical element folds the optical path, the size of the optical system itself can be reduced as compared with the refractive optical system.

Further, since the reflection surface has a higher sensitivity to eccentricity error than the refraction surface, high accuracy is required for assembly adjustment.
However, among the reflective optical elements, since the relative positional relationship between the surfaces of the prisms is fixed, the eccentricity may be controlled as a single prism, and unnecessary assembly accuracy and adjustment man-hours are unnecessary.

Further, the prism has an entrance surface, an exit surface, which are refraction surfaces, and a reflection surface, and has a greater degree of freedom for aberration correction than a mirror having only a reflection surface. In particular, by allowing the reflection surface to share most of the desired power and reducing the power of the entrance surface and the exit surface, which are refraction surfaces, the degree of freedom in correcting aberrations is larger than that of a mirror, while maintaining the degree of freedom for aberrations. Compared with such a refractive optical element, the occurrence of chromatic aberration can be extremely reduced. Further, since the inside of the prism is filled with a transparent body having a higher refractive index than air, the optical path length can be made longer than that of air. Thinning and miniaturization are possible.

In the present invention, a prism member composed of one or two eccentric prisms is arranged, and the eccentric aberration is corrected by the object-side portion and the image-side portion. It enables good correction. If the number of reflections is one for each part,
It is impossible to completely correct eccentric aberration.

According to the present invention, for the above reasons, the light beam is reflected four times or more inside the prism member, and an intermediate image plane is formed in the optical path between the first reflection surface and the fourth reflection surface. It is configured so that

In the object-side portion of the prism member of the present invention, the first incidence surface and the second reflection surface are configured so that the transmission function and the reflection function are shared by one surface by total reflection. , The first incident surface, the first reflecting surface, and the second
A reflection optical path is formed by the reflection surface.

As described above, by using one surface as both the second reflecting surface and the transmitting surface of the first incident surface, at least the object-side portion of the prism member can be miniaturized, and the size of the prism member can be reduced. It is possible to take a relatively large angle of view.

In the image-side portion of the prism member of the present invention, the third reflecting surface, the fourth reflecting surface, and the first exit surface rotate a light beam along a triangular optical path, and have a third reflecting surface. And an optical path guided from the fourth reflection surface to the first exit surface forms an intersection optical path.

In the prism image side portion having such a shape, the degree of freedom for aberration correction is high, and the occurrence of aberration is small. Furthermore, since the arrangement of the two reflecting surfaces (third reflecting surface and fourth reflecting surface) on the prism image side portion is highly symmetric, aberrations occurring on the two reflecting surfaces are corrected by the two reflecting surfaces. And the occurrence of aberration is small. Further, since the optical path forms a crossed optical path in the prism image side portion, it is possible to take a longer optical path length as compared with a prism shape having a structure in which the optical path is simply turned back, and the optical path length is relatively long. The prism image side portion can be reduced in size. More preferably, since the two reflecting surfaces on the prism image side have different sign powers, the effect of mutual correction of aberrations can be increased, and a high resolution can be obtained.

Further, by using the prism image side portion that forms the cross optical path as described above, it is possible to make the prism image side portion small. This is because, when the same optical path length is taken, the space utilization efficiency is higher than that of the prism which is of the same double reflection type and has a Z-shaped optical path in the prism. In the prism shape having a Z-shaped optical path, the light rays in the prism always pass through another region, but in the prism shape in which the optical paths intersect in the prism, the light beam passes through the same region twice, and This is because the shape can be reduced in size.

In the present invention, as will be described later, the prism member may be formed of a single prism formed by joining or integral molding. Alternatively, the first prism forming the prism object side portion and the prism image side portion may be formed. The second that constitutes
Although a prism may be used, a fifth reflecting surface may be arranged between the second reflecting surface on the prism object side portion and the third reflecting surface on the prism image side portion.

As described above, in the case of the type in which the fifth reflecting surface is disposed between the second reflecting surface and the third reflecting surface on the prism image side portion, an independent optical working surface is used as the fifth reflecting surface. The degree of freedom in the arrangement of the reflecting surface is increased, the protrusion of the prism member on the side opposite to the entrance pupil (aperture) can be reduced, the thickness in the direction along the incident optical axis can be reduced, and the prism member The injection direction can be set freely.
Further, since the number of optical action surfaces is increased by one, the degree of freedom for aberration correction is high, and aberration correction can be performed well.

Here, assuming that a ray passing through the center of the object point and passing through the center of the stop and reaching the center of the image plane is an axial principal ray,
If at least one reflecting surface of the object-side portion of the prism member of the present invention and at least one reflecting surface of the image-side portion thereof are not decentered with respect to the axial principal ray, the incident ray and the reflected ray of the axial principal ray will be different. The same optical path is taken, and the axial chief ray is blocked in the optical system. As a result, an image is formed only by the light flux whose central portion is shielded, and the center becomes dark or the image is not formed at the center at all.

Further, at least one of the first reflection surface and the second reflection surface of the object side portion of the prism member of the present invention is
It has a curved surface shape that gives power to the light beam, and the curved surface shape is constituted by a rotationally asymmetric surface shape that corrects aberrations caused by eccentricity, and the third reflection surface and the fourth reflection surface of the image side portion At least one surface has a curved surface shape that gives power to the light beam, and the curved surface shape is configured to be a rotationally asymmetric surface shape that corrects aberrations caused by eccentricity.

The reason will be described in detail below. First, a coordinate system to be used and a rotationally asymmetric surface will be described. An optical axis defined by a straight line until the on-axis principal ray intersects the first surface of the optical system is defined as a Z axis, and is orthogonal to the Z axis and within an eccentric plane of each surface constituting the imaging optical system. Is defined as the Y axis,
An axis orthogonal to the optical axis and orthogonal to the Y axis is defined as an X axis. The ray tracing direction will be described in terms of forward ray tracing from the object to the image plane.

In general, in a spherical lens system composed only of spherical lenses, spherical aberration generated by a spherical surface and aberrations such as coma and field curvature are mutually corrected on several planes, so that the aberration is reduced as a whole. Configuration.

On the other hand, in order to favorably correct aberrations with a small number of surfaces, a rotationally symmetric aspherical surface or the like is used. This is to reduce various aberrations generated on the spherical surface. However, in a decentered optical system, it is impossible to correct rotationally asymmetric aberration generated by decentering by a rotationally symmetric optical system. The rotationally asymmetric aberrations caused by this eccentricity include distortion, field curvature, astigmatism and coma which also occur on the axis.

First, the rotationally asymmetric field curvature will be described. For example, light rays incident on a concave mirror decentered from an object point at infinity are reflected and imaged on the concave mirror, but after the light rays hit the concave mirror, the rear focal length to the image plane is
When the image field side is air, the radius of curvature becomes half of the radius of curvature of the portion hit by the light beam. Then, as shown in FIG. 21, an image plane inclined with respect to the axial principal ray is formed. As described above, it is impossible to correct rotationally asymmetric curvature of field with a rotationally symmetric optical system.

In order to correct the tilted curvature of field by the concave mirror M itself, which is the source, the concave mirror M is constituted by a rotationally asymmetric surface. In this example, the curvature is strong in the positive Y-axis direction ( If the refractive power is increased) and the curvature is decreased (the refractive power is decreased) in the negative direction of the Y axis, the correction can be made. In addition, by arranging a rotationally asymmetric surface having the same effect as the above configuration in the optical system separately from the concave mirror M, a flat image surface can be obtained with a small number of components. In addition, the rotationally asymmetric surface is preferably a rotationally asymmetric surface shape having no rotationally symmetric axis both inside and outside the surface, which is preferable in terms of increasing the degree of freedom and correcting aberrations.

Next, rotationally asymmetric astigmatism will be described. As described above, the eccentrically arranged concave mirror M
In this case, astigmatism as shown in FIG. 22 also occurs for axial rays. Astigmatism can be corrected by appropriately changing the curvature in the X-axis direction and the curvature in the Y-axis direction of the rotationally asymmetric surface, as described above.

Further, rotationally asymmetric coma will be described. Similarly to the above description, in the concave mirror M arranged eccentrically, coma as shown in FIG. To correct the coma aberration, the inclination of the surface can be changed as the distance from the origin of the X axis of the rotationally asymmetric surface increases, and the inclination of the surface can be appropriately changed depending on the sign of the Y axis.

In the image forming optical system according to the present invention, it is also possible that at least one surface having the above-mentioned reflecting action is decentered with respect to the axial principal ray, and has a rotationally asymmetric surface shape having power. With such a configuration, it becomes possible to correct the eccentric aberration caused by giving power to the reflecting surface by the surface itself, and by relaxing the power of the refracting surface of the prism, the occurrence of chromatic aberration itself can be reduced. Can be smaller.

The rotationally asymmetric surface used in the present invention is preferably a plane-symmetric free-form surface having only one plane of symmetry. Here, the free-form surface used in the present invention is:
It is defined by the following equation (a). Note that the Z axis of the definition formula is the axis of the free-form surface.

[0041] Here, the first term of the equation (a) is a spherical term, and the second term is a free-form surface term.

In the spherical term, c: curvature of the vertex k: conic constant (conical constant) r = √ (X ² + Y ² ).

The free-form surface term is Here, C _j (j is an integer of 2 or more) is a coefficient.

The free-form surface is generally an XZ surface,
Although neither YZ plane has a plane of symmetry, in the present invention, X
By setting all the odd-order terms to 0, a free-form surface having only one symmetry plane parallel to the YZ plane is obtained. For example, in the above definition formula (a), C ₂ , C ₅ , C ₇ ,
_{C 9, C 12, C 14} , C 16, C 18, C 20, C 23, C 25, C
₂₇ , C ₂₉ , C ₃₁ , C ₃₃ , C ₃₅ ...

By setting all odd-numbered terms of Y to 0, a free-form surface having only one symmetry plane parallel to the XZ plane is obtained. For example, in the above definition formula, C ₃ ,
_{C 5, C 8, C 10} , C 12, C 14, C 17, C 19, C 21, C
₂₃ , C ₂₅ , C ₂₇ , C ₃₀ , C ₃₂ , C ₃₄ , C ₃₆ ...

One of the directions of the symmetry plane is a symmetry plane, and the eccentricity in the corresponding direction, for example, the eccentric direction of the optical system with respect to the symmetry plane parallel to the YZ plane is in the Y-axis direction. By making the eccentric direction of the optical system the X-axis direction with respect to the symmetric plane parallel to the XZ plane, it is possible to effectively correct rotationally asymmetric aberrations caused by the eccentricity while improving the productivity. Becomes possible.

Further, the above-mentioned definition formula (a) is shown as one example as described above, and the present invention uses a rotationally asymmetric surface having only one symmetrical surface to obtain a rotation caused by eccentricity. It is characterized by correcting asymmetric aberrations and at the same time improving productivity, and it goes without saying that the same effect can be obtained for any other definitional expressions.

Now, the power of the decentered optical system and the power of the optical surface will be defined. As shown in FIG. 24, when the eccentric direction of the eccentric optical system S is set in the Y-axis direction, a light beam having a minute height d in a YZ plane parallel to the axial principal ray of the eccentric optical system S is An angle formed when the light ray incident from the object side and emitted from the decentered optical system S and projected on the YZ plane of the axial principal ray is δy, and δy / d is the power Py of the decentered optical system S in the Y direction. A light beam having a minute height d in the X direction parallel to the axial principal ray of the decentered optical system and orthogonal to the YZ plane is incident from the object side, and emitted from the decentered optical system S and the axial principal ray. Δx, and δx / d is the power Px of the eccentric optical system S in the X direction, when the projection is made on a plane orthogonal to the YZ plane and including the axial principal ray. Similarly, the power Pyn in the Y direction and the power Px in the X direction of the decentered optical surface n forming the decentered optical system S
n is defined.

Further, the reciprocals of these powers are respectively the focal length Fy of the eccentric optical system in the Y direction, the focal length Fx of the eccentric optical system in the X direction, and the focal length F of the eccentric optical surface n in the Y direction.
yn and the focal length Fxn in the X direction.

In the imaging optical system of the present invention, a stop is arranged on the incident side of the first incident surface. When the axial distance from the first entrance surface to the stop is ER and the focal length in the Y direction of the entire optical system is Fy, the relationship of ER / Fy ≦ 2.0 (1) is satisfied. is important. This condition is a condition for improving aberration correction by bringing the stop as close as possible to the prism member, and for reducing the size of the imaging optical system.
Exceeding the upper limit of 2.0 makes it particularly difficult to reduce the size of the optical system.

More preferably, it is important to satisfy the following condition: ER / Fy ≦ 1.5 (1-1)

More preferably, it is important to satisfy the following condition: ER / Fy ≦ 1.2 (1-2)

The power in the X direction and the power in the Y direction of the two reflecting surfaces (first reflecting surface and second reflecting surface) constituting the Z-shaped optical path of the prism object-side portion are Px in order from the object side.
When the power in the X direction of all optical systems is Px and the power in the Y direction is Py, 0.1 <Px1-1 / | Px | < It is important to satisfy the following conditions: This condition stipulates the ratio of the power of the first reflecting surface in the X direction to the whole system. If the lower limit of 0.1 is exceeded, the positive power at the first reflecting surface becomes too small, and the other surface Aberration, the aberration performance deteriorates. If the upper limit of 3 is exceeded, the positive power borne by the first reflecting surface will be too strong, and the eccentric aberration generated on this surface will be too large, making it difficult to correct on other surfaces.

More preferably, it is important to satisfy the following condition: 0.5 <Px1-1 / | Px | <2 ...- 1.

Next, it is important that the power of the first reflecting surface in the Y direction satisfies the following condition: -0.5 <Py1-1 / | Py | <3 ... This condition stipulates the ratio of the power of the first reflecting surface in the Y direction to the entire system. If the ratio exceeds the lower limit of -0.5, the negative power at the first reflecting surface becomes too large, and Since the surface bears a positive power, the aberration performance deteriorates. In addition, the upper limit of 3
Is exceeded, the power borne by the first reflection surface becomes too strong, the eccentric aberration generated on this surface becomes too large, and it becomes difficult to correct it on other surfaces.

More preferably, it is important to satisfy the following condition: 0.2 <Py1-1 / | Py | <1.5 ...- 1.

Next, regarding the second reflecting surface, this surface is a surface having both a transmitting action and a reflecting action, and has an effect of largely bending the optical path toward the image plane. Need to take. Therefore, if a large power is applied to this surface, both positive and negative, aberrations due to eccentricity are greatly generated, and it is difficult to correct it on other surfaces.
Therefore, it is important to satisfy the following conditions.

It is preferable to satisfy the following condition: -2 <Px1-2 / | Px | <1 This condition is the second
This defines the ratio of the power of the reflecting surface in the X direction to the entire system. If the ratio exceeds the lower limit of -2, the negative power on the second reflecting surface becomes too large, and the other surface bears the positive power. As a result, the aberration performance deteriorates. When the upper limit of 1 is exceeded, the positive power borne by the second reflecting surface becomes too strong, and the eccentric aberration generated on this surface becomes too large.
It becomes difficult to correct in other aspects.

More preferably, it is important to satisfy the following condition: -1 <Px1-2 / | Px | <0.5 (-1)

Next, it is preferable to satisfy the following condition: -1 <Py1-2 / | Py | <1. This condition is the second
This defines the ratio of the power of the reflecting surface in the Y direction to the whole system. If the ratio exceeds the lower limit of -1, the negative power on the second reflecting surface becomes too large, and the other surface bears the positive power. Therefore, the aberration performance deteriorates. If the upper limit of 1 is exceeded, the positive power borne by the second reflection surface will be too strong, and the eccentric aberration generated on this surface will be too large, making it difficult to correct on other surfaces.

More preferably, it is important to satisfy the following condition: -0.5 <Py1-2 / | Py | <1 ...- 1.

Next, the two reflecting surfaces (third reflecting surface and fourth reflecting surface) on the prism image side forming the intersection optical path will be described. X of the two reflecting surfaces forming the cross optical path on the image side
Direction power and Y direction power in order from the object side to Px2-
1, Py2-1, Px2-1, and Py2-2 preferably satisfy the following condition: -0.5 <Px2-1 / | Px | <1.5 ... This condition is the third
This defines the ratio of the power in the X direction to the entire system of the reflecting surface. If the lower limit of -0.5 is exceeded, the negative power on the third reflecting surface becomes too large, and the positive power on the other surfaces is increased. , The aberration performance deteriorates. If the upper limit of 1.5 is exceeded, the positive power borne by the third reflecting surface will be too strong, and the eccentric aberration generated on this surface will be too large, making it difficult to correct on other surfaces. .

More preferably, it is preferable to satisfy the following condition: 0.1 <Px2-1 / | Px | <1 ...- 1.

In the Y direction, it is preferable to satisfy the following condition: -0.5 <Py2-1 / | Py | <1.5. This condition is the third
This defines the ratio of the power in the Y direction to the entire system of the reflecting surface. If the lower limit of -0.5 is exceeded, the negative power on the third reflecting surface becomes too large, and the positive power is applied to other surfaces. Due to the burden, aberration performance deteriorates. The upper limit of 1.
If it exceeds 5, the positive power borne by the third reflecting surface will be too strong, and the eccentric aberration generated on this surface will be too large, making it difficult to correct on other surfaces.

More preferably, it is preferable to satisfy the following condition: 0 <Py2-1 / | Py | <1 ...- 1.

Next, the fourth reflecting surface will be described. It is preferable that the following condition is satisfied: -1 <Px2-2 / | Px | <1.5. This condition is the fourth
This defines the ratio of the power of the reflecting surface in the X direction to the whole system. If the ratio exceeds the lower limit of -1, the negative power on the fourth reflecting surface becomes too large, and the other surface bears the positive power. Therefore, the aberration performance deteriorates. In addition, the upper limit of 1.5
Is exceeded, the power borne by the fourth reflection surface becomes too strong, the eccentric aberration generated on this surface becomes too large, and it becomes difficult to correct it on other surfaces.

More preferably, it is preferable to satisfy the following condition: -0.5 <Px2-2 / | Px | <1 ...- 1.

In the Y direction, it is preferable to satisfy the following condition: -1 <Py2-2 / | Py | <1.5. This condition is the fourth
This defines the ratio of the power in the Y direction to the entire system of the reflecting surface. If the lower limit of −1 is exceeded, the negative power on the fourth reflecting surface becomes too large, and the other surface bears the positive power. Therefore, the aberration performance deteriorates. In addition, the upper limit of 1.5
Is exceeded, the power borne by the fourth reflection surface becomes too strong, the eccentric aberration generated on this surface becomes too large, and it becomes difficult to correct it on other surfaces.

More preferably, it is preferable to satisfy the following condition: -0.5 <Py2-2 / | Py | <1 ...- 1.

Further, the power in the X direction of the third reflecting surface and the fourth reflecting surface is Px2-1 and Px2-2, and the power in the Y direction is Py.
2-1 and Py2-2, and (Px2-1 + Px2-2) / (Py
When (2-1 + Py2-2) is Px2 / Py2, it is preferable to satisfy the following condition: -1 <Px2 / Py2 <5. This condition is the third
It determines the ratio of the sum of the power in the X direction and the sum of the power in the reflecting surface and the fourth reflecting surface to the sum of the power in the Y direction. Image distortion that extends in the X direction is large. On the other hand, when the value exceeds the upper limit of 5, the power in the X direction becomes too large in the Y direction, and image distortion extending in the Y direction is generated. The third reflecting surface and the fourth reflecting surface have a function of relaying a primary image formed in the middle on the object side of the optical system to the image surface, and the X direction of the third reflecting surface and the fourth reflecting surface The balance between the power in the Y direction and the power in the Y direction is important when a relay optical system is configured.

More preferably, it is preferable to satisfy the following condition: 0 <Px2 / Py2 <3...

More preferably, it is important to satisfy the following condition: 0.2 <Px2 / Py2 <2...

Further, more preferably, the above conditions
It is preferable to satisfy two or more or all of the above in order to obtain a favorable aberration correction state.

It is more preferable that at least two or more of the above conditions (1) and (2) are satisfied. Most desirably, it is preferable to configure so as to satisfy all of the nine conditions.

In the imaging optical system according to the present invention, the prism member includes a first incident surface, a first reflecting surface, a second reflecting surface, a third reflecting surface, a fourth reflecting surface, and a first exit surface. Even if it is constituted by one prism by joining or integral molding,
A first prism having an entrance surface, a first reflection surface, and a second reflection surface, and a third prism having a third reflection surface, a fourth reflection surface, and a first exit surface, and spaced from the first prism. It may be composed of two prisms.

Further, the prism member is formed by connecting the second reflecting surface to the third reflecting surface.
A fifth reflecting surface for reflecting a light beam in the prism between the reflecting surface and the first reflecting surface, a first reflecting surface, a second reflecting surface, a fifth reflecting surface, a third reflecting surface, and a fourth reflecting surface; Even if it is constituted by a single prism formed by joining or integral molding having a first reflecting surface and a fifth reflecting surface, a fifth reflecting surface for reflecting a light beam in the prism is provided between the second reflecting surface and the third reflecting surface. With the first
A first prism having an entrance surface, a first reflection surface, a second reflection surface, and a fifth reflection surface; and a third prism having a third reflection surface, a fourth reflection surface, and a first exit surface, spaced apart from the first prism. Placed second
It may be composed of a prism.

In these cases, it is desirable that both the first reflecting surface and the second reflecting surface have a rotationally asymmetric surface shape that applies power to the light beam and corrects aberrations caused by eccentricity.

In the case where the fifth reflecting surface is provided, the first reflecting surface, the second reflecting surface, and the fifth reflecting surface are used to apply power to the light beam and reduce aberrations caused by eccentricity. It is desirable to configure so as to have a rotationally asymmetric surface shape to be corrected.

Further, both the third reflecting surface and the fourth reflecting surface are
It is desirable that the light beam be configured to have a rotationally asymmetric surface shape that applies power to the light beam and corrects aberration generated by decentering.

It is desirable that the first exit surface has a rotationally asymmetric surface shape that applies power to the light beam and corrects aberrations caused by eccentricity.

When the prism member is composed of the first prism and the second prism, at least one of the exit surface of the first prism and the entrance surface of the second prism is generated by giving power to the light beam and decentering. It is desirable to have a configuration having a rotationally asymmetric surface shape that corrects aberrations.

In this case, the exit surface of the first prism and the second prism
Both surfaces of the prism and the incident surface can be configured to have a rotationally asymmetric surface shape that applies power to the light beam and corrects aberration generated by decentering.

In the above description, the rotationally asymmetric surface shape is desirably a plane-symmetric free-form surface shape having only one plane of symmetry.

The intermediate image plane is formed by a rotationally asymmetric surface, and the optically active surface disposed on the object side and the optically active surface disposed on the image forming side with respect to the intermediate image plane are mutually compensated. It is desirable that the eccentric aberration be corrected in combination.

In the image forming optical system according to the present invention, it is needless to say that focusing of the image forming optical system can be performed by extending the entire surface or moving the prism. Focusing can be performed by moving the image plane in the direction of the on-axis principal ray. Thereby, even if the direction of incidence of the axial chief ray from the object and the direction of the axial chief ray exiting from the most image-side surface do not match because the imaging optical system is decentered,
It is possible to prevent displacement of the axial principal ray on the incident side due to focusing. Further, it is also possible to divide the parallel plane plate into a plurality of wedge-shaped prisms and perform focusing by moving the prism in a direction perpendicular to the Z axis. Also in this case, focusing is possible regardless of the eccentricity of the imaging optical system.

In the present invention, temperature compensation can be achieved by using different materials for the prism object side portion and the prism image side portion. In particular, in order to prevent a focus shift due to a temperature change, which is a problem when plastic is used as the material of the prisms, it is possible to make the prism portions have different sign powers.

In the present invention, when two prism portions are joined together, it is desirable to provide respective relative positioning portions on a surface having no optical action. In particular, when two prism portions having power are joined to a reflection surface as in the present invention, the relative positional accuracy shift causes performance degradation. Therefore, in the present invention,
By providing the relative positioning portion on the surface of the prism having no optical function, it is possible to secure positional accuracy and secure desired performance. In particular, if the two prisms are integrated by a connecting member using the positioning portion, assembly adjustment becomes unnecessary, and the cost can be further reduced.

The optical path may be folded in a direction different from the eccentric direction of the image forming optical system of the present invention by using a reflecting optical member such as a mirror on the object side of the incident surface of the image forming optical system of the present invention. It is possible. Thereby, the degree of freedom of the layout of the imaging optical system is further increased, and the size of the entire imaging optical device can be reduced.

In the present invention, the image forming optical system can be composed of only a prism. As a result, the number of parts is reduced, and the cost is reduced. Furthermore, it is of course possible to integrate two prisms before and after the stop to form one prism. Thereby, further cost reduction is possible.

In the present invention, in addition to the prism,
Other lenses (positive lens, negative lens) may be included as constituent elements on either the object side or the image side or on both sides.

Further, the image forming optical system according to the present invention can be a bright single focus lens. Also, a zoom lens (magnification imaging optical system) can be formed by combining one or a plurality of refractive optical systems on the object side, between the two prisms, or on the image side of the prism.

In the present invention, it is also possible to form the refracting surface and the reflecting surface of the image forming optical system with a spherical surface or a rotationally symmetric aspherical surface.

The reflecting surface other than the total reflecting surface of the prism of the present invention may be constituted by a reflecting surface having a thin metal film such as aluminum or silver formed on the surface or a reflecting surface having a dielectric multilayer film formed thereon. Is preferred. When the metal thin film has a reflecting action, it is possible to easily obtain a high reflectance. In the case of a dielectric reflection film, it is advantageous when a reflection film having low wavelength selectivity and low absorption is formed. As a result, it is possible to obtain a low-cost, compact imaging optical system in which the manufacturing accuracy of the prism is reduced.

When the above-described image forming optical system of the present invention is arranged in the image pickup unit of the image pickup apparatus, or when the image pickup apparatus has a camera mechanism, the prism member is formed of an optical element having an optical function. The prism member is disposed closest to the object side, the incident surface of the prism member is disposed eccentrically with respect to the optical axis, and a cover member disposed perpendicular to the optical axis is disposed closer to the object side than the prism member. In addition, the prism member is configured so as to have an incident surface that is eccentrically arranged on the object side with respect to the optical axis, and the power arranged coaxially with the optical axis with an air gap interposed between the incident surface and the air surface. The cover lens may be arranged on the object side of the incident surface.

As described above, when the prism member is disposed closest to the object and the eccentric incident surface is provided on the front surface of the photographing apparatus,
Since the incident surface obliquely seen from the subject can be seen, an uncomfortable feeling may be given as if the photographing was performed around a position shifted from the subject. Therefore, by arranging a cover member or a cover lens perpendicular to the optical axis, it is possible to perform imaging without feeling uncomfortable with the object to be imaged, similarly to a general imaging device.

Any of the imaging optical systems of the present invention as described above is arranged as a finder objective optical system, and further, an image erecting optical system for erecting an object image formed by the finder objective optical system. A finder optical system can be configured from the eyepiece optical system.

Further, a camera device can be constructed by including the finder optical system and a photographing objective optical system provided in parallel with the finder optical system.

Further, the imaging optical system according to the present invention includes any one of the above-described imaging optical systems according to the present invention and an imaging device disposed on an image plane formed by the imaging optical system. Can be.

Further, any one of the above-described image forming optical systems of the present invention is arranged as a photographing objective optical system, and an optical path different from the photographing optical system or an optical path of the photographing objective optical system. The camera device can be provided with a finder optical system disposed in any of the optical paths divided from the camera.

Further, any one of the above-described image forming optical systems of the present invention, an image pickup device arranged on an image plane formed by the image forming optical system, and image information received by the image pickup device. An electronic camera device can be configured to include a recording medium that records the image data, and an image display element that forms an observation image by receiving image information from the recording medium or the image sensor.

An observation system having any one of the above-described image forming optical systems of the present invention and an image transmitting member that transmits an image formed by the image forming optical system along the long axis direction.
An endoscope apparatus can be configured to include an illumination light source and an illumination system having an illumination light transmission member that transmits illumination light from the illumination light source along the long axis direction.

[0102]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 12 of the image forming optical system according to the present invention will be described below. The configuration parameters of each embodiment will be described later. In the first to sixth embodiments, as shown in FIG. 1, the axial principal ray 1 is defined as a ray that exits the center of the object, passes through the center of the stop 2, and reaches the center of the image plane 3. Then, the on-axis principal ray 1 and the first incident surface of the prism 10 (first
Surface) passing through the intersection of 11 and the first exit surface 16, the first entrance surface 11 is perpendicular to the axial principal ray 1 incident on the surface, and the first exit surface 16 is on the axis exiting from the surface. A virtual plane is taken perpendicular to the principal ray 1. In the case of a virtual plane defined for the intersection of the entrance plane, with the intersection of each virtual plane as the origin of the eccentric optical plane between the optical plane passing through that intersection and the next virtual plane (the image plane for the last virtual plane) Is
In the case of an imaginary plane defined about the intersection of the incident axial principal ray 1 and the exit surface, the direction along the emerging axial principal ray 1 is defined as the Z-axis direction, and the axial principal ray 1 and the first incidence of the prism 10 With respect to the first virtual plane passing through the intersection with the plane (first plane) 11, the direction along the traveling direction of the axial principal ray 1 is defined as the positive Z-axis direction. When the number of reflections in the optical path from the first virtual plane to the virtual plane is an even number, the direction along the traveling direction of the axial principal ray 1 is Z
When the number of reflections is an odd number, the direction opposite to the traveling direction of the axial chief ray 1 is defined as the positive direction of the Z axis, the plane including the Z axis and the center of the image plane is defined as the YZ plane, and the origin is defined. Through Y-
A direction perpendicular to the Z plane and from the front of the paper toward the back side is defined as a positive X-axis direction, and an axis constituting a right-handed orthogonal coordinate system with the X-axis and the Z-axis is defined as a Y-axis. FIG. 1 shows each virtual surface and the first incident surface 1.
3 shows a coordinate system for a first virtual plane defined for one intersection. 2 to 6, illustration of these virtual planes and coordinate systems is omitted.

In the seventh to twelfth embodiments, as shown in FIG. 7, the on-axis principal ray 1 is defined as a ray that exits the center of the object, passes through the center of the stop 2, and reaches the center of the image plane 3. . Then, the intersection of the axial principal ray 1 with the first entrance surface (first surface) 11 of the first prism 21, the exit surface 18 of the first prism 21, the entrance surface 19 of the second prism 22, and the first exit surface 16 Through the first incident surface 11 and the incident surface 19 of the second prism 22, perpendicular to the axial principal ray 1 incident on the surfaces,
The exit surface 18 of the prism 21 and the first exit surface 16 of the second prism 22 take virtual planes perpendicular to the axial principal ray 1 exiting from the surfaces. In the case of a virtual plane defined for the intersection of the entrance plane, with the intersection of each virtual plane as the origin of the eccentric optical plane between the optical plane passing through that intersection and the next virtual plane (the image plane for the last virtual plane) In the case of an imaginary plane defined at the intersection of the incident axial principal ray 1 and the exit surface, the direction along the emerging axial principal ray 1 is defined as the Z-axis direction, and the axial principal ray 1 and the first prism 21 For the first virtual plane passing through the intersection with the first incident surface (first surface) 11, the direction along the traveling direction of the axial chief ray 1 is defined as the positive direction of the Z-axis. If the number of reflections in the optical path from one virtual plane to the virtual plane is an even number, the axial chief ray 1
Is defined as a positive Z-axis direction, and when the number of reflections is an odd number, a direction opposite to the advancing direction of the axial principal ray 1 is defined as a positive Z-axis direction, including the Z-axis and the image plane center. Plane is Y-
A direction perpendicular to the YZ plane passing through the origin is defined as a Z plane, and a direction from the near side of the drawing to the back side is defined as a positive X axis direction.
The axis constituting the right-handed orthogonal coordinate system with the axis is defined as the Y axis. FIG. 7 illustrates a coordinate system for the first virtual plane defined for the intersection of each virtual plane and the first incident plane 11. Fig. 8-
FIG. 12 does not show these virtual planes and coordinate systems.

In the first to twelfth embodiments, each plane is decentered in the YZ plane, and the only symmetric plane of each rotationally asymmetric free-form surface is the YZ plane.

For the eccentric surface, the amount of eccentricity (X, Y, and Z in the X-axis, Y-axis, and Z-axis directions) at the top of the surface from the origin of the corresponding coordinate system, and the X of the central axis (for a free-form surface, the Z-axis in the above equation (a))
The tilt angles (α, β, γ (°), respectively) about the axis, the Y axis, and the Z axis are given. In this case, the positive α and β mean counterclockwise with respect to the positive direction of each axis, and the positive γ means clockwise with respect to the positive direction of the Z axis.

In the case where a specific surface (including a virtual surface) and a surface following the specific surface (including a virtual surface) form a coaxial optical system in the optical working surfaces forming the optical system of each embodiment, the surface spacing is given. In addition, the refractive index of the medium and the Abbe number are given according to a conventional method. The sign of the surface interval is a positive value when the number of reflections in the optical path from the first virtual surface to the reference optical surface (including the virtual surface) is an even number, and is a positive value when the number is an odd number. Is shown as a negative value, but the axial chief ray 1
Are all positive values along the traveling direction.

Further, the shape of the surface of the free-form surface used in the present invention is defined by the above equation (a), and the Z axis of the definition equation is the axis of the free-form surface.

The term relating to a free-form surface on which no data is described is zero. The refractive index for d-line (wavelength 587.56 nm) is shown. The unit of the length is mm.

As another definition of the free-form surface, there is a Zernike polynomial given by the following expression (b).
The shape of this surface is defined by the following equation. The Z axis of the defining equation is the axis of the Zernike polynomial. The definition of the rotationally asymmetric surface is defined by polar coordinates of the height of the Z axis with respect to the XY plane, A is the distance from the Z axis in the XY plane, R is the azimuth around the Z axis, and the Z axis It can be expressed by the rotation angle measured from.

X = R × cos (A) y = R × sin (A) Z = D ₂ + D ₃ Rcos (A) + D ₄ Rsin (A) + D ₅ R ² cos (2A) + D ₆ (R ² −1 ^{_{) + D 7 R 2 sin (}} 2A) + D 8 R 3 cos (3A) + D 9 (3R 3 -2R) cos (A) + D 10 (3R 3 -2R) sin (A) + D 11 R 3 sin (3A) + D ^{_{12 R 4 cos (4A) +}} D 13 (4R 4 -3R 2) cos (2A) + D 14 (6R 4 -6R 2 +1) + D 15 (4R 4 -3R 2) sin (2A) + D 16 R 4 sin (4A ^{_{) + D 17 R 5 cos (}} 5A) + D 18 (5R 5 -4R 3) cos (3A) + D 19 (10R 5 -12R 3 + 3R) cos (A) + D 20 (10R 5 -12R 3 + 3R) sin (A) ^{_{+ D 21 (5R 5 -4R 3}} ) sin (3A) + D 22 R 5 sin (5A) + D 23 R 6 cos (6A) + D 24 (6R 6 -5R 4) cos (4A) + D 25 (15R 6 -20R 4 ^{+ 6R 2) cos (2A)} + D 26 (20R 6 -30R 4 + 12R 2 -1) + D 27 (15R 6 -20R 4 + 6R 2) sin (2A) ^{_{D 28 (6R 6 -5R 4)}} sin (4A) + D 29 R 6 sin (6A) ····· ··· (b) In addition, to design an optical system symmetric with respect to the X-axis direction, D
_{4, D 5, D 6,} D 10 0, D 11, D 12, D 13, D 14, D
_20, D _21, D ₂₂ ... to use.

As another example, the following definition formula (c)
Is raised. Z = ΣΣC _nm XY As an example, when k = 7 (seventh-order term) is considered, when expanded, it can be expressed by the following equation. _{Z = C 2 + C 3 y} + C 4 | x | + C 5 y 2 + C 6 y | x | + C 7 x 2 + C 8 y 3 + C 9 y 2 | x | + C 10 yx 2 + C 11 | x 3 | + C 12 y 4 ^{_{+ C 13 y 3 | x |}} + C 14 y 2 x 2 + C 15 y | x 3 | + C 16 x 4 + C 17 y 5 + C 18 y 4 | x | + C 19 y 3 x 2 + C 20 y 2 | x 3 | + C ^{_{21 yx 4 + C 22 | x}} 5 | + C 23 y 6 + C 24 y 5 | x | + C 25 y 4 x 2 + C 26 y 3 | x 3 | + C 27 y 2 x 4 + C 28 y | x 5 | + C 29 x ^{_{6 + C 30 y 7 + C}} 31 y 6 | x | + C 32 y 5 x 2 + C 33 y 4 | x 3 | + C 34 y 3 x 4 + C 35 y 2 | x 5 | + C 36 yx 6 + C 37 | x 7 | (C) In the embodiment of the present invention, the surface shape is expressed by a free-form surface using the above equation (a).
It goes without saying that the same operation and effect can be obtained by using the expression (c).

In each of Examples 1 to 12, the angle of view was 26.3 ° for the horizontal half angle of view, 20.3 ° for the vertical half angle of view, and the image height was 1.6 × 1.2 mm. The diameter is 1.15 mm, the focal length is 3.24 mm, the F-number is 2.8, which corresponds to a focal length of 35 mm when converted to a silver halide camera. Further, the present invention includes not only an imaging optical system using the imaging optical system of the present invention but also an imaging device incorporating the optical system.

Embodiment 1 FIG. 1 shows a YZ sectional view of Embodiment 1 including an axial principal ray. Although the configuration parameters of this embodiment will be described later, the free-form surface is represented by FFS, and the virtual surface is represented by HRP (virtual reference plane). The same applies to other embodiments.

In the first embodiment, the stop 2, the object-side portion of the prism 10, the image-side portion of the prism 10, and the image plane (imaging surface) 3 are arranged in the order in which light passes from the object side. Are the first incident surface 11, the first reflecting surface 12, and the second
The light is transmitted and reflected in that order. The first incident surface 11 and the second reflecting surface 13 are formed of one surface having both a transmitting action and a reflecting action, and the second reflecting face 13 is based on a total reflecting action on the dual-use face. The intermediate image plane 4 formed by the object-side portion (however, the intermediate image plane 4 in FIGS. 1 to 12 is formally taken perpendicularly to the axial principal ray 1 through the intermediate image point. Is formed behind the second reflecting surface 13.
The intermediate image plane 4 is imaged on the image plane 3 by the image-side portion of the prism 10, and the image-side portion of the prism 10 has a third reflection surface 14, a fourth reflection surface 15, and a first exit surface 16. And light rays are reflected and transmitted in that order. In addition, the light beam incident on the third reflection surface 14 and the light beam reflected from the fourth reflection surface 15 intersect in the prism 10.

The third to ninth surfaces of the constituent parameters described later are expressed by the amount of eccentricity with respect to the second virtual surface 1, and the image surface is shifted from the ninth virtual surface 2. It is represented only by the surface spacing along the axial chief ray.

Embodiments 2 and 5 FIGS. 2 and 5 show YZ sectional views of Embodiments 2 and 5 including the axial principal ray. The configuration parameters of these embodiments will be described later. In the second and fifth embodiments, the stop 2, the object-side portion of the prism 10, and the prism 10 are arranged in the order in which light passes from the object side.
, An image side (imaging plane) 3 and a prism 10
The object-side portion of the first light-emitting device has a first incident surface 11 and a first reflecting surface 12.
And the second reflecting surface 13, in which order light rays are transmitted,
reflect. The first incident surface 11 and the second reflecting surface 13 are formed of one surface having both a transmitting action and a reflecting action.
Is due to the total reflection effect on the dual-purpose surface. An intermediate image plane 4 formed by the object-side portion is formed after the second reflecting surface 13. The intermediate image plane 4 is formed by the image side portion of the prism 10.
The image side portion of the prism 10 is
It is composed of a reflecting surface 14, a fourth reflecting surface 15, and a first exit surface 16, in which light rays are reflected and transmitted in that order. In addition, the light beam incident on the third reflection surface 14 and the light beam reflected from the fourth reflection surface 15 intersect in the prism 10. The difference between the first embodiment and the second and fifth embodiments is that the directions of reflection on the third reflection surface 14 are opposite to each other.

Further, the third to ninth surfaces of the constituent parameters described later are represented by the amount of eccentricity with respect to the second virtual surface 1, and the image surface is the eccentricity from the ninth virtual surface 2. It is represented only by the surface spacing along the axial chief ray.

Embodiments 3 and 6 FIGS. 3 and 6 show YZ sectional views of Embodiments 3 and 6 including the axial chief ray, respectively. The configuration parameters of these embodiments will be described later. In the third and sixth embodiments, the stop 2, the object-side portion of the prism 10, and the prism 10 are arranged in the order in which light passes from the object side.
, An image side (imaging plane) 3 and a prism 10
The object-side portion of the first light-emitting device has a first incident surface 11 and a first reflecting surface 12.
, The second reflection surface 13 and the fifth reflection surface 17, and light rays are transmitted and reflected in that order. The first incident surface 11 and the second reflecting surface 13 are formed of one surface having both a transmitting action and a reflecting action, and the second reflecting face 13 is based on a total reflecting action on the dual-use face. The intermediate image surface 4 of the first incident surface 11, the first reflecting surface 12, and the second reflecting surface 13 of the object side portion is the second reflecting surface 1.
It is formed between the third and fifth reflection surfaces 17. The intermediate image surface 4 is imaged on the image surface 3 by the fifth reflection surface 17 and the image side portion of the prism 10, and the image side portion of the prism 10 has the third reflection surface 14, the fourth reflection surface 15, , The first exit surface 16, and light rays are reflected and transmitted in that order. In addition, the light beam incident on the third reflection surface 14 and the light beam reflected from the fourth reflection surface 15 intersect in the prism 10.

Further, the third to tenth surfaces of the constituent parameters to be described later are represented by the amount of eccentricity with respect to the virtual surface 1 of the second surface, and the image surface is the distance from the virtual surface 2 of the tenth surface. It is represented only by the surface spacing along the axial chief ray.

Embodiment 4 FIG. 4 is a sectional view taken along the line YZ of FIG. The configuration parameters of this embodiment will be described later. Example 4
Are, in order of light passing from the object side, the stop 2, the object side portion of the prism 10, the image side portion of the prism 10, and the image plane (imaging plane).
3, the object-side portion of the prism 10 includes a first incident surface 11, a first reflecting surface 12, a second reflecting surface 13, and a fifth reflecting surface 17, and light rays are transmitted and reflected in that order. .
The first incident surface 11 and the second reflecting surface 13 are formed of one surface having both a transmitting action and a reflecting action, and the second reflecting face 13 is based on a total reflecting action on the dual-use face. The first of this object side part
An intermediate image plane 4 formed by the entrance surface 11, the first reflection surface 12, and the second reflection surface 13 is formed between the second reflection surface 13 and the fifth reflection surface 17. The intermediate image plane 4 is imaged on the image plane 3 by the fifth reflection surface 17 and the image side portion of the prism 10.
The image-side portion of the third reflecting surface 14 and the fourth reflecting surface 15
And the first exit surface 16, and the rays are reflected in that order,
To Penetrate. Also, the light beam incident on the third reflecting surface 14 and the fourth
Light rays reflected from the reflection surface 15 intersect in the prism 10. The difference between the third, sixth and fourth embodiments is that the directions of reflection on the fifth reflecting surface 17 are opposite to each other.

The third to tenth constituent parameters described later are expressed by the amount of eccentricity with respect to the second virtual plane 1, and the image plane is the distance from the virtual plane 2 of the tenth plane. It is represented only by the surface spacing along the axial chief ray.

Seventh Embodiment FIG. 7 is a sectional view of the seventh embodiment taken along the line YZ including the axial principal ray. The configuration parameters of this embodiment will be described later. Example 7
Are the stop 2 and the first prism 2 in the order in which light passes from the object side.
The first prism 21 includes a first incident surface 11 and a first reflecting surface 12.
, A second reflection surface 13 and a second emission surface 18, and light rays are transmitted, reflected and transmitted in that order. The first incident surface 11 and the second reflecting surface 13 are formed of one surface having both a transmitting action and a reflecting action, and the second reflecting face 13 is based on a total reflecting action on the dual-use face. The first incident surface 11, the first reflecting surface 12, and the second
An intermediate image plane 4 formed by the reflection surface 13 is formed between the second reflection surface 13 and the second transmission surface 18. The intermediate image surface 4 is the second transmission surface 1
8 and the second prism 22 form an image on the image plane 3. The second prism 22 includes a second entrance surface 19, a third reflection surface 14, a fourth reflection surface 15, and a first exit surface 16. The light beam is transmitted, reflected and transmitted in that order. Also, the third
The light beam incident on the reflecting surface 14 and the light beam reflected from the fourth reflecting surface 15 intersect in the second prism 22.

Further, the third to seventh surfaces of the constituent parameters described later are represented by the amount of eccentricity with respect to the virtual surface 1 of the second surface, and the top position of the eighth surface (virtual surface 3) Is expressed only by the surface interval along the axial principal ray from the virtual surface 2 of the seventh surface, and the ninth to thirteenth surfaces are expressed by the amount of eccentricity with respect to the virtual surface 3 of the eighth surface. And the image plane is the first
It is represented only by the surface interval along the axial principal ray from the three virtual surfaces 4.

Embodiments 8 and 11 FIGS. 8 and 11 show YZ sectional views of Embodiments 8 and 11 including the axial chief ray, respectively. The configuration parameters of these embodiments will be described later. In the eighth and eleventh embodiments, the stop 2, the first prism 21, and the second prism 2 are arranged in the order in which light passes from the object side.
2, an image plane (imaging plane) 3, and the first prism 21
First incidence surface 11, first reflection surface 12, and second reflection surface 13
And the second exit surface 18, in which light rays are transmitted in that order,
Reflects and transmits. The first incident surface 11 and the second reflecting surface 13 are formed of one surface having both a transmitting action and a reflecting action, and the second reflecting face 13 is based on a total reflecting action on the dual-use face. First
An intermediate image plane 4 formed by the entrance surface 11, the first reflection surface 12, and the second reflection surface 13 is formed between the second reflection surface 13 and the second transmission surface 18. The intermediate image plane 4 includes the second transmission surface 18 and the second prism 2
An image is formed on the image plane 3 by the second prism 22.
Is composed of a second incident surface 19, a third reflecting surface 14, a fourth reflecting surface 15, and a first exit surface 16, and light rays are transmitted, reflected, and transmitted in that order. In addition, the light beam incident on the third reflection surface 14 and the light beam reflected from the fourth reflection surface 15 intersect in the second prism 22. The difference between the seventh embodiment, the eighth embodiment, and the eleventh embodiment is that the directions of reflection on the third reflection surface 14 are opposite to each other.

Further, the third to seventh surfaces of the constituent parameters described later are represented by the amount of eccentricity with respect to the virtual surface 1 of the second surface, and the top position of the eighth surface (virtual surface 3) Is expressed only by the surface interval along the axial principal ray from the virtual surface 2 of the seventh surface, and the ninth to thirteenth surfaces are expressed by the amount of eccentricity with respect to the virtual surface 3 of the eighth surface. And the image plane is the first
It is represented only by the surface interval along the axial principal ray from the three virtual surfaces 4.

Ninth Embodiment FIG. 9 is a sectional view taken along the line YZ of the ninth embodiment including the axial principal ray. The configuration parameters of this embodiment will be described later. Example 9
Are the stop 2 and the first prism 2 in the order in which light passes from the object side.
The first prism 21 includes a first incident surface 11 and a first reflecting surface 12.
, A second reflecting surface 13, a fifth reflecting surface 17, and a second exit surface 18, and light rays are transmitted, reflected, and transmitted in that order. The first incident surface 11 and the second reflecting surface 13 are formed of one surface having both a transmitting action and a reflecting action, and the second reflecting face 13 is based on a total reflecting action on the dual-use face. An intermediate image plane 4 formed by the first incident surface 11, the first reflecting surface 12, and the second reflecting surface 13 is formed between the fifth reflecting surface 17 and the second transmitting surface 18. The intermediate image surface 4 is imaged on the image surface 3 by the second transmitting surface 18 and the second prism 22, and the second prism 22 has the second incident surface 19, the third reflecting surface 14, and the fourth reflecting surface 14. Face 15 and the first
The light beam is transmitted, reflected, and transmitted in that order. In addition, the light beam incident on the third reflection surface 14 and the light beam reflected from the fourth reflection surface 15 intersect in the second prism 22.

The third to eighth surfaces of the constituent parameters described later are represented by the amount of eccentricity with respect to the second virtual surface 1, and the top position of the ninth surface (virtual surface 3). Is expressed only by the surface interval along the axial principal ray from the virtual surface 2 of the eighth surface, and the eccentricity with respect to the virtual surface 3 of the ninth surface is used for the tenth to fourteenth surfaces. The image plane is represented only by the surface interval along the axial principal ray from the virtual surface 4 of the fourteenth surface.

Embodiments 10 and 12 FIGS. 10 and 12 show YZ sectional views of Embodiments 10 and 12 including the axial chief ray, respectively. The configuration parameters of these embodiments will be described later. In the tenth and twelfth embodiments, the stop 2, the first prism 21, the second prism 22, and the image plane (imaging plane) 3 are arranged in the order in which light passes from the object side.
Is composed of a first incident surface 11, a first reflecting surface 12, a second reflecting surface 13, a fifth reflecting surface 17, and a second exit surface 18, and light rays are transmitted, reflected, and transmitted in that order. The first incidence surface 11 and the second reflection surface 13 are used for both transmission and reflection.
The second reflecting surface 13 is based on a total reflection effect on the dual-purpose surface. First incidence surface 11 and first reflection surface 12
And an intermediate image plane 4 formed by the second reflection surface 13 and the second reflection surface 13 and the fifth reflection surface 17. The intermediate image surface 4 is imaged on the image surface 3 by the fifth reflection surface 17, the second transmission surface 18, and the second prism 22, and the second prism 22 has the second entrance surface 19, the third reflection surface 14, a fourth reflecting surface 15, and a first exit surface 16, in which order light rays are transmitted, reflected,
To Penetrate. Also, the light beam incident on the third reflecting surface 14 and the fourth
Light rays reflected from the reflection surface 15 intersect in the second prism 22. The difference between the ninth and tenth and twelfth embodiments is that
The point is that the directions of reflection at the third reflection surface 14 are opposite to each other.

The third to eighth planes of the constituent parameters described later are represented by the amount of eccentricity with respect to the virtual plane 1 of the second plane, and the top position of the ninth plane (virtual plane 3) Is expressed only by the surface interval along the axial principal ray from the virtual surface 2 of the eighth surface, and the eccentricity with respect to the virtual surface 3 of the ninth surface is used for the tenth to fourteenth surfaces. The image plane is represented only by the surface interval along the axial principal ray from the virtual surface 4 of the fourteenth surface.

The following is a description of the configuration parameters of Examples 1 to 12 described above. “FFS” in these tables is a free-form surface, “HR”
P ″ indicates a virtual plane.

Example 1 Surface Number Curvature Radius Surface Distance Eccentricity Refractive Index Abbe Number Object Surface -100-1000.00 1 絞 り (aperture surface) 3.32 2 ∞ (HRP1) 3 FFS Eccentricity (1) 1.4924 57.6 4 FFS Eccentricity (2) 1.4924 57.6 5 FFS Eccentricity (1) 1.4924 57.6 6 FFS Eccentricity (3) 1.4924 57.6 7 FFS Eccentricity (4) 1.4924 57.6 8 FFS Eccentricity (5) 9 ∞ (HRP2) 2.63 Eccentricity (6) Image plane ＦＦ FFS C ₄ -2.5215 × 10 ^-2 C ₆ 2.7653 × 10 ^-2 FFS C ₄ -5.2284 × 10 ^-2 C ₆ 1.9608 × 10 ^-3 FFS C ₄ -3.0876 × 10 ^-2 C ₆ 3.1859 × 10 ^-3 FFS C ₄ 1.4462 × 10 ^-2 C ₆ 3.8284 × 10 ^-2 FFS C ₄ -1.4394 × 10 ^-1 C ₆ -1.0776 × 10 ^-1 Eccentricity (1) X 0.00 Y 2.27 Z -0.34 α 4.95 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.16 Z 2.28 α -17.40 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y 0.00 Z 8.08 α -27.64 β 0.00 γ eccentricity (4) X 0.00 Y 2.14 Z 6.60 α -86.85 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y -3.81 Z 3.38 α -121.68ββ 0.00 γ 0.00 Eccentricity (6) X 0.00 Y -3.81 Z 3.38 α -116.83 β 0.00 γ 0.00.

Example 2 Surface Number Curvature Radius Surface Distance Eccentricity Refractive Index Abbe Number Object Surface -100-1000.00 1 ∞ (aperture surface) 3.27 2 ∞ (HRP1) 3 FFS Eccentricity (1) 1.4924 57.6 4 FFS Eccentricity (2) 1.4924 57.6 5 FFS Eccentricity (1) 1.4924 57.6 6 FFS Eccentricity (3) 1.4924 57.6 7 FFS Eccentricity (4) 1.4924 57.6 8 FFS Eccentricity (5) 9 ∞ (HRP2) 2.00 Eccentricity (6) Image plane ∞ FFS C ₄ -1.1884 × 10 ^{_{-2 C 6 4.2044 × 10 -3 FFS}} C 4 -4.6064 × 10 -2 C 6 -3.7307 × 10 -2 FFS C 4 -3.0315 × 10 -2 C 6 -3.7523 × 10 -2 FFS C 4 2.2939 × 10 - ² C ₆ 1.0393 × 10 ^-3 FFS C ₄ -1.4092 × 10 ^-1 C ₆ -1.0316 × 10 ^-1 Eccentricity (1) X 0.00 Y 2.41 Z -0.31 α 6.73 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.09 Z 1.99 α -21.31 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y 0.00 Z 10.99 α 14.82 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y -2.88 Z 5.94 α 56.99 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y 2.27 Z 6.45 α 79.68 β 0.00 γ 0.00 Eccentricity (6) X 0.00 2.27 Z 6.45 α 86.64 β 0.00 γ 0.00.

Example 3 Surface Number Curvature Radius Surface Distance Eccentricity Refractive Index Abbe Number Object Surface -100 -1000.00 1 ∞ (aperture surface) 3.89 2 ∞ (HRP1) 3 FFS Eccentricity (1) 1.4924 57.6 4 FFS Eccentricity (2) 1.4924 57.6 5 FFS Eccentricity (1) 1.4924 57.6 6 FFS Eccentricity (3) 1.4924 57.6 7 FFS Eccentricity (4) 1.4924 57.6 8 FFS Eccentricity (5) 1.4924 57.6 9 FFS Eccentricity (6) 10 ∞ (HRP2) -2.00 Eccentricity (7) Image Surface ∞ FFS C ₄ -2.3143 × 10 ^-2 C ₆ 4.1244 × 10 ^-3 FFS C ₄ -4.5518 × 10 ^-2 C ₆ -3.3802 × 10 ^-2 FFS C ₄ -1.5971 × 10 ^-2 C ₆ -6.0639 × 10 ^{_{-3 FFS C 4 -2.3661 × 10 -2}} C 6 -3.1532 × 10 -2 FFS C 4 2.7998 × 10 -2 C 6 1.0504 × 10 -2 FFS C 4 -1.7084 × 10 -1 C 6 -5.4563 × 10 - ² Eccentricity (1) X 0.00 Y 2.68 Z -0.29 α 5.53 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.08 Z 2.13 α -22.38 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y 0.00 Z 4.28 α -36.56 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y 7.45 Z 2.02 α 84.37 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y 3.75 Z 0.04 α 39.37 β 0.00 γ 0.00 Eccentricity (6) X 0.00 Y 5.09 Z 4.47 α 18.04 β 0.00 γ 0.00 Eccentricity (7) X 0.00 Y 5.09 Z 4.47 α 196.30 β 0.00 γ 0.00.

Example 4 Surface Number Curvature Radius Surface Distance Eccentricity Refractive Index Abbe Number Object Surface -100 -1000.00 1 ∞ (aperture surface) 3.76 2 ∞ (HRP1) 3 FFS Eccentricity (1) 1.4924 57.6 4 FFS Eccentricity (2) 1.4924 57.6 5 FFS Eccentricity (1) 1.4924 57.6 6 FFS Eccentricity (3) 1.4924 57.6 7 FFS Eccentricity (4) 1.4924 57.6 8 FFS Eccentricity (5) 1.4924 57.6 9 FFS Eccentricity (6) 10 ∞ (HRP2) -2.58 Eccentricity (7) Image Surface ∞ FFS C ₄ -6.8317 × 10 ^-3 C ₆ -1.0454 × 10 ^-3 FFS C ₄ -4.0430 × 10 ^-2 C ₆ -3.5642 × 10 ^-2 FFS C ₄ -1.7590 × 10 ^-2 C ₆ -1.2473 × 10 ^-2 FFS C ₄ -2.3050 × 10 ^-2 C ₆ -7.1552 × 10 ^-3 FFS C ₄ 2.8 103 × 10 ^-2 C ₆ 3.2110 × 10 ^-2 FFS C ₄ -6.9932 × 10 ^-2 C ₆ -2.6337 × 10 ^-2 Eccentricity (1) X 0.00 Y 2.07 Z -0.88 α 23.28 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.34 Z 2.47 α -9.70 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y 0.00 Z 2.73 α 47.41 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y -8.91 Z 3.48 α -48.74 β 0.00 0.00 Eccentricity (5) X 0.00 Y -8.31 Z 0.74 α 7.52 β 0.00 γ 0.00 Eccentricity (6) X 0.00 Y -5.83 Z 5.53 α 44.57 β 0.00 γ 0.00 Eccentricity (7) X 0.00 Y -5.83 Z 5.53 α -161.65 β 0.00 γ 0.00.

Example 5 Surface Number Curvature Radius Surface Spacing Eccentricity Refractive Index Abbe Number Object Surface -100-1000.00 1 ∞ (aperture surface) 2.21 2 ∞ (HRP1) 3 FFS Eccentricity (1) 1.4924 57.6 4 FFS Eccentricity (2) 1.4924 57.6 5 FFS eccentricity (1) 1.4924 57.6 6 FFS eccentricity (3) 1.4924 57.6 7 FFS eccentricity (4) 1.4924 57.6 8 FFS eccentricity (5) 9 ∞ (HRP2) 2.04 eccentricity (6) Image plane ∞ FFS C ₄ -2.2324 × 10 ^-2 C ₆ 2.4110 × 10 ^-2 C ₈ 8.4626 × 10 ^-4 C ₁₀ 9.2 202 × 10 ^-4 FFS C ₄ -5.7826 × 10 ^-2 C ₆ -2.5266 × 10 ^-2 C ₈ 4.1440 × 10 ^-3 C _10- 1.5320 × 10 ^-3 FFS C ₄ -3.1317 × 10 ^-2 C ₆ -3.3269 × 10 ^-2 C ₈ -1.9022 × 10 ^-4 C ₁₀ -2.5822 × 10 ^-4 FFS C ₄ 2.0530 × 10 ^-2 C ₆ 1.0928 × 10 ^-2 C ₈ 4.8861 × 10 ^-4 C ₁₀ 2.1951 × 10 ^-4 FFS C ₄ -7.2489 × 10 ^-2 C ₆ -1.6286 × 10 ^-2 C ₈ 1.1176 × 10 ^-1 Eccentricity (1) X 0.00 Y 2.67 Z -0.11 α -0.86 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.06 Z 1.80 α -26.00 β 0.00 γ 0.00 Eccentricity (3) X 0.00 0.00 Z 10.83 α 13.33 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y -2.97 Z 4.91 α 60.26 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y 2.40 Z 4.55 α 91.42 β 0.00 γ 0.00 Eccentricity (6) X 0.00 Y 2.40 Z 4.55 α 95.05 β 0.00 γ 0.00.

Example 6 Surface No. Curvature Radius Surface Distance Eccentricity Refractive Index Abbe Number Object Surface -100-1000.00 1 ∞ (aperture surface) 2.17 2 ∞ (HRP1) 3 FFS Eccentricity (1) 1.4924 57.6 4 FFS Eccentricity (2) 1.4924 57.6 5 FFS Eccentricity (1) 1.4924 57.6 6 FFS Eccentricity (3) 1.4924 57.6 7 FFS Eccentricity (4) 1.4924 57.6 8 FFS Eccentricity (5) 1.4924 57.6 9 FFS Eccentricity (6) 10 ∞ (HRP2) -2.95 Eccentricity (7) Image Surface ＦＦ FFS C ₄ -4.1211 × 10 ^-2 C ₆ 2.0648 × 10 ^-2 C ₈ 6.5506 × 10 ^-3 C ₁₀ 6.3573 × 10 ^-4 C ₁₁ 2.2 140 × 10 ^-4 C ₁₃ 4.1244 × 10 ^-4 C ₁₅ -6.9872 _{^{× 10 -5 FFS C 4 -7.4673 ×}} 10 -2 C 6 -3.1403 × 10 -2 C 8 1.0805 × 10 -2 C 10 -6.1869 × 10 -4 C 11 2.5085 × 10 -4 C 13 -1.6418 × 10 - ^{_{4 C 15 2.8812 × 10 -4 FFS}} C 4 -1.9781 × 10 -2 C 6 -1.6446 × 10 -2 C 8 4.6681 × 10 -3 C 10 -5.0874 × 10 -5 C 11 2.7642 × 10 -4 C 13 - 1.5185 × 10 ^-4 C ₁₅ -1.8713 × 10 ^-4 FFS C ₄ -2.4834 × 10 ^-2 C ₆ -1.6583 × 10 ^-2 C ₈ 3.0842 × 10 ^-3 C ₁₀ 4 .8218 × 10 ^-6 C ₁₁ -5.3702 × 10 ^-5 C ₁₃ 3.2027 × 10 ^-4 C ₁₅ 2.2773 × 10 ^-4 FFS C ₄ 1.9725 × 10 ^-2 C ₆ 2.4968 × 10 ^-2 C ₈ 3.2553 × 10 ^-3 C ₁₀ -5.8531 × 10 ^-4 C ₁₁ -2.4664 × 10 ^-4 C ₁₃ -1.1748 × 10 ^-4 C ₁₅ 2.7005 × 10 ^-4 FFS C ₄ 6.9 354 × 10 ^-2 C ₆ 9.1695 × 10 ^-2 C ₈ -1.0174 × 10 ^-1 C ₁₀ -1.1246 × 10 ^-2 C ₁₁ -1.8913 × 10 ^-2 C ₁₃ -1.2958 × 10 ^-2 C ₁₅ 6.8041 × 10 ^-3 Eccentricity (1) X 0.00 Y 2.32 Z -0.21 α 2.54 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.08 Z 1.80 α -22.92 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y 0.00 Z 4.50 α -33.01 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y 8.34 Z 0.79 α 91.49 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y 4.49 Z -0.69 α 46.49 β 0.00 γ 0.00 Eccentricity (6) X 0.00 Y 6.46 Z 3.74 α 29.34 β 0.00 γ 0.00 Eccentricity (7) X 0.00 Y 6.46 Z 3.74 α 201.34 β 0.00 γ 0.00.

Example 7 Surface Number Curvature Radius Surface Distance Eccentricity Refractive Index Abbe Number Object Surface -100 -1000.00 1 ∞ (aperture surface) 1.43 2 ∞ (HRP1) 3 FFS Eccentricity (1) 1.4924 57.6 4 FFS Eccentricity (2) 1.4924 57.6 5 FFS Eccentricity (1) 1.4924 57.6 6 FFS Eccentricity (3) 7 ∞ (HRP2) 0.84 Eccentricity (4) 8 ∞ (HRP3) 9 FFS Eccentricity (5) 1.4924 57.6 10 FFS Eccentricity (6) 1.4924 57.6 11 FFS Eccentricity (7) ) 1.4924 57.6 12 FFS Eccentricity (8) 13 ∞ (HRP4) 2.66 Eccentricity (9) Image plane ＦＦ FFS C ₄ -6.9796 × 10 ^-3 C ₆ 6.4628 × 10 ^-3 FFS C ₄ -4.7890 × 10 ^-2 C _6- 2.8881 × 10 ^-2 FFS C ₄ -5.3350 × 10 ^-2 C ₆ -1.9635 × 10 ^-1 FFS C ₄ 6.0996 × 10 ^-2 C ₆ -9.9073 × 10 ^-2 FFS C ₄ -2.4317 × 10 ^-2 C _6- 1.5340 × 10 ^-2 FFS C ₄ 1.8633 × 10 ^-2 C ₆ 2.8476 × 10 ^-2 FFS C ₄ -6.1525 × 10 ^-2 C ₆ -1.4839 × 10 ^-2 Eccentricity (1) X 0.00 Y 3.40 Z -0.90 α 13.43 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.37 Z 3.89 α -13. 54 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y 7.28 Z 1.41 α 55.18 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y 7.28 Z 1.41 α 61.33 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y 0.00 Z 0.00 α -18.49 β 0.00 γ 0.00 Eccentricity (6) X 0.00 Y 1.43 Z 6.58 α -10.23 β 0.00 γ 0.00 Eccentricity (7) X 0.00 Y 3.74 Z 3.00 α -55.23 β 0.00 γ 0.00 Eccentricity (8) X 0.00 Y -1.27 Z 4.09 α -97.53 β 0.00 γ 0.00 Eccentricity (9) X 0.00 Y -1.27 Z 4.09 α -67.17 β 0.00 γ 0.00.

Example 8 Surface Number Curvature Radius Surface Distance Eccentricity Refractive Index Abbe Number Object Surface -100-1000.00 1 ∞ (aperture surface) 1.69 2 ∞ (HRP1) 3 FFS Eccentricity (1) 1.4924 57.6 4 FFS Eccentricity (2) 1.4924 57.6 5 FFS eccentricity (1) 1.4924 57.6 6 FFS eccentricity (3) 7 ∞ (HRP2) 0.92 eccentricity (4) 8 ∞ (HRP3) 9 FFS eccentricity (5) 1.4924 57.6 10 FFS eccentricity (6) 1.4924 57.6 11 FFS eccentricity (7) ) 1.4924 57.6 12 FFS Eccentricity (8) 13 ∞ (HRP4) 2.00 Eccentricity (9) Image plane ＦＦ FFS C ₄ -1.1404 × 10 ^-2 C ₆ 4.3584 × 10 ^-3 FFS C ₄ -4.1756 × 10 ^-2 C _6- 3.3108 × 10 ^-2 FFS C ₄ -1.1761 × 10 ^-1 C ₆ -1.0535 × 10 ^-1 FFS C ₄ 6.6868 × 10 ^-2 C ₆ 4.8829 × 10 ^-2 FFS C ₄ -6.7724 × 10 ^-3 C ₆ -1.7504 × 10 ^-2 FFS C ₄ 3.3910 × 10 ^-2 C ₆ 1.7912 × 10 ^-2 FFS C ₄ -1.5492 × 10 ^-1 C ₆ -9.1509 × 10 ^-2 Eccentricity (1) X 0.00 Y 3.78 Z -0.58 α 7.77 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.12 Z 2.15 α -25.02 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y 9.97 Z 1.82 α 62.36 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y 9.97 Z 1.82 α 71.98 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y 0.00 Z 0.00 α -0.50 β 0.00 γ 0.00 Eccentricity (6) X 0.00 Y 0.04 Z 6.20 α 22.84 β 0.00 γ 0.00 Eccentricity (7) X 0.00 Y -3.29 Z 2.92 α 67.84 β 0.00 γ 0.00 Eccentricity (8) X 0.00 Y 2.88 Z 2.88 α 85.95 β 0.00 γ 0.00 eccentricity (9) X 0.00 Y 2.88 Z 2.88 α 92.51 β 0.00 γ 0.00.

Example 9 Surface Number Curvature Radius Surface Distance Eccentricity Refractive Index Abbe Number Object Surface -100 -1000.00 1 ∞ (aperture surface) 2.30 2 ∞ (HRP1) 3 FFS Eccentricity (1) 1.4924 57.6 4 FFS Eccentricity (2) 1.4924 57.6 5 FFS eccentricity (1) 1.4924 57.6 6 FFS eccentricity (3) 1.4924 57.6 7 FFS eccentricity (4) 8 ∞ (HRP2) -1.29 eccentricity (5) 9 ∞ (HRP3) 10 FFS eccentricity (6) 1.4924 57.6 11 FFS eccentricity 7) 1.4924 57.6 12 FFS Eccentricity (8) 1.4924 57.6 13 FFS Eccentricity (9) 14 ∞ (HRP4) -2.00 Eccentricity (10) Image plane ＦＦ FFS C ₄ -1.4051 × 10 ^-2 C ₆ 2.8022 × 10 ^-2 FFS C ₄ -5.6507 × 10 ^-2 C ₆ -1.3161 × 10 ^-3 FFS C ₄ -1.7690 × 10 ^-2 C ₆ -5.0442 × 10 ^-3 FFS C ₄ 1.5719 × 10 ^-1 C ₆ 8.5497 × 10 ^-2 FFS C _{4 ^{5.5110 × 10 -2 C 6 3.8356 ×}} 10 -2 FFS C 4 1.6418 × 10 -2 C 6 3.0926 × 10 -2 FFS C 4 2.4674 × 10 -2 C 6 8.6744 × 10 -3 FFS C 4 -2.3012 × 10 - ² C ₆ -2.0973 × 10 ^-2 Eccentricity (1) X 0.00 Y 1.27 Z -0.54 α 20.62 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.29 Z 1.94 α -6.52 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y 5.92 Z 1.85 α 7.10 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y 9.99 Z -1.74 α -40.47 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y 9.99 Z -1.74 α -52.71 β 0.00 γ 0.00 Eccentricity (6) X 0.00 Y 0.00 Z 0.00 α -14.97 β 0.00 γ 0.00 Eccentricity (7) X 0.00 Y 0.47 Z -5.35 α -29.83 β 0.00 γ 0.00 Eccentricity (8) X 0.00 Y -2.26 Z -3.42 α 98.89 β 0.00 γ 0.00 Eccentricity (9) X 0.00 Y 3.25 Z -1.67 α 71.12 β 0.00 γ Eccentricity (10) X 0.00 Y 3.25 Z -1.67 α -106.93 β 0.00 γ 0.00.

Example 10 Surface Number Curvature Radius Surface Distance Eccentricity Refractive Index Abbe Number Object Surface ∞-1000.00 1 ∞ (aperture surface) 2.04 2 ∞ (HRP1) 3 FFS Eccentricity (1) 1.4924 57.6 4 FFS Eccentricity (2) 1.4924 57.6 5 FFS Eccentricity (1) 1.4924 57.6 6 FFS Eccentricity (3) 1.4924 57.6 7 FFS Eccentricity (4) 8 ∞ (HRP2) -1.85 Eccentricity (5) 9 ∞ (HRP3) 10 FFS Eccentricity (6) 1.4924 57.6 11 FFS Eccentricity ( 7) 1.4924 57.6 12 FFS Eccentricity (8) 1.4924 57.6 13 FFS Eccentricity (9) 14 ∞ (HRP4) -2.00 Eccentricity (10) Image plane ＦＦ FFS C ₄ -1.2594 × 10 ^-2 C ₆ -4.8520 × 10 ^-3 FFS C ₄ -4.5200 × 10 ^-2 C ₆ -4.7567 × 10 ^-2 FFS C ₄ -3.7526 × 10 ^-3 C ₆ -5.7546 × 10 ^-3 FFS C ₄ 8.6447 × 10 ^-2 C ₆ 1.2234 × 10 ^-1 FFS C ₄ -5.2972 × 10 ^-2 C ₆ 4.7932 × 10 ^-3 FFS C ₄ 2.4720 × 10 ^-2 C ₆ 2.5831 × 10 ^-2 FFS C ₄ 1.1581 × 10 ^-2 C ₆ 2.4499 × 10 ^-3 FFS C ₄ -1.8916 × 10 ^-1 C ₆ -7.9305 × 10 ^-2 Eccentricity (1) X 0.0 0 Y 1.33 Z -0.40 α 17.34 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.14 Z 1.47 α -13.40 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y 5.66 Z 1.43 α 7.01 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y 9.30 Z -1.31 α -55.59 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y 9.30 Z -1.31 α -51.71 β 0.00 γ 0.00 Eccentricity (6) X 0.00 Y 0.00 Z 0.00 α -14.08 β 0.00 γ 0.00 Eccentricity ( 7) X 0.00 Y 0.58 Z -7.00 α 20.27 β 0.00 γ 0.00 Eccentricity (8) X 0.00 Y 2.90 Z -4.70 α -105.05 β 0.00 γ 0.00 Eccentricity (9) X 0.00 Y -3.18 Z -3.10 α -71.82 β 0.00 γ 0.00 Eccentricity (10) X 0.00 Y -3.18 Z -3.10 α 102.95 β 0.00 γ 0.00.

Example 11 Surface number Curvature radius Surface distance Eccentricity Refractive index Abbe number Object plane -100-1000.00 1 絞 り (aperture plane) 2.46 2 ∞ (HRP1) 3 FFS eccentricity (1) 1.4924 57.6 4 FFS eccentricity (2) 1.4924 57.6 5 FFS eccentricity (1) 1.4924 57.6 6 FFS eccentricity (3) 7 ∞ (HRP2) 1.51 eccentricity (4) 8 ∞ (HRP3) 9 FFS eccentricity (5) 1.4924 57.6 10 FFS eccentricity (6) 1.4924 57.6 11 FFS eccentricity (7 ) 1.4924 57.6 12 FFS Eccentricity (8) 13 ∞ (HRP4) 2.00 Eccentricity (9) Image plane ＦＦ FFS C ₄ -4.0797 × 10 ^-3 C ₆ 9.0304 × 10 ^-3 C ₈ -1.6760 × 10 ^-3 C ₁₀ 1.2644 × _{^{10 -3 FFS C 4 -3.4936 × 10}} -2 C 6 -3.1213 × 10 -2 C 8 1.2304 × 10 -3 C 10 2.2770 × 10 -3 FFS C 4 -8.9998 × 10 -2 C 6 -5.1653 × 10 - ² C ₈ 5.9094 × 10 ^-3 C ₁₀ 1.1447 × 10 ^-2 FFS C ₄ 6.4630 × 10 ^-2 C ₆ 9.1823 × 10 ^-3 C ₈ 1.4946 × 10 ^-2 C ₁₀ 7.1713 × 10 ^-3 FFS C ₄ -8.2686 × 10 ^-3 C ₆ -2.4604 × 10 ^-2 C ₈ 3.6 106 × 10 ^-3 C ₁₀ -4.8361 × 10 ^-4 FFS C ₄ 3.1962 × 10 ^-2 C ₆ 1.7063 × 10 ^-2 C ₈ 3.4465 × 10 ^-3 C ₁₀ -2.5110 × 10 ^-4 FFS C ₄ -1.8053 × 10 ^-1 C ₆ -3.9578 × 10 ^-2 C ₈ 1.0752 × 10 ^-1 C ₁₀ 4.0068 × 10 ^-2 Eccentricity (1) X 0.00 Y 1.74 Z -0.74 α 22.48 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.34 Z 2.40 α -7.95 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y 9.95 Z 2.42 α 51.57 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y 9.95 Z 2.42 α 77.98 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y 0.00 Z 0.00 α 2.60 β 0.00 γ 0.00 Eccentricity (6) X 0.00 Y -0.17 Z 5.47 α 20.76 β 0.00 γ 0.00 Eccentricity (7) X 0.00 Y -2.95 Z 2.51 α 65.76 β 0.00 γ 0.00 Eccentricity (8) X 0.00 Y 2.35 Z 2.67 α 90.13 β 0.00 γ 0.00 Eccentricity (9) X 0.00 Y 2.35 Z 2.67 α 87.33 β 0.00 γ 0.00.

Example 12 Surface Number Curvature Radius Surface Distance Eccentricity Refractive Index Abbe Number Object Surface ∞-1000.00 1 ∞ (aperture surface) 2.60 2 ∞ (HRP1) 3 FFS Eccentricity (1) 1.4924 57.6 4 FFS Eccentricity (2) 1.4924 57.6 5 FFS eccentricity (1) 1.4924 57.6 6 FFS eccentricity (3) 1.4924 57.6 7 FFS eccentricity (4) 8 ∞ (HRP2) -1.21 eccentricity (5) 9 ∞ (HRP3) 10 FFS eccentricity (6) 1.4924 57.6 11 FFS eccentricity 7) 1.4924 57.6 12 FFS Eccentricity (8) 1.4924 57.6 13 FFS Eccentricity (9) 14 ∞ (HRP4) -2.00 Eccentricity (10) Image plane ∞ FFS C ₄ -2.5676 × 10 ^-2 C ₆ -1.2956 × 10 ^-2 C ₈ -2.2763 × 10 ^-3 C ₁₀ -1.1542 × 10 ^-3 FFS C ₄ -5.0631 × 10 ^-2 C ₆ -5.3228 × 10 ^-2 C ₈ -4.7245 × 10 ^-4 C ₁₀ -5.8151 × 10 ^-4 FFS C ₄ 7.8688 × 10 ^-4 C ₆ -6.7252 × 10 ^-3 C ₈ -1.2165 × 10 ^-3 C ₁₀ 4.0309 × 10 ^-4 FFS C ₄ 7.2662 × 10 ^-2 C ₆ 1.3869 × 10 ^-1 C ₈ -6.6493 × 10 ^-3 C ₁₀ 5.8745 × 10 ^-3 FFS C ₄ -6.1718 × 10 ^-2 C ₆ 5.4095 × 10 ^-2 C ₈ -2.9898 × 10 ^-3 C ₁₀ 8.6094 × 10 ^-3 FFS C ₄ 2.3221 × 10 ^-2 C ₆ 2.7086 × 10 ^-2 C ₈ -1.0197 × 10 ^-4 C ₁₀ 5.1333 × 10 ^-5 FFS C ₄ 1.4310 × 10 ^-2 C ₆ 5.2257 × 10 ^-3 C ₈ 7.0096 × 10 ^-5 C ₁₀ 1.0226 × 10 ^-4 FFS C ₄ -2.2295 × 10 ^-1 C ₆ -4.9987 × 10 ^-2 C ₈ -5.3918 × 10 ^-3 C ₁₀ -1.2306 × 10 ^-2 Eccentricity (1) X 0.00 Y 1.46 Z -0.39 α 16.05 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.13 Z 1.58 α -14.59 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y 5.65 Z 1.47 α 10.88 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y 8.66 Z -1.60 α -52.13 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y 8.66 Z -1.60 α -40.37 β 0.00 γ 0.00 Eccentricity (6) X 0.00 Y 0.00 Z 0.00 α -20.88 β 0.00 γ 0.00 Eccentricity (7) X 0.00 Y 0.92 Z -7.44 α 16.09 β 0.00 γ 0.00 Eccentricity (8) X 0.00 Y 2.88 Z -5.04 α -106.58 β 0.00 γ 0.00 Eccentricity (9) X 0.00 Y -3.01 Z -3.17 α -70.59 β 0.00 γ 0.00 Eccentricity (10) X 0.00 Y -3.01 Z -3.17 α 106.68 β 0.00 γ 0.00.

Next, FIG. 13 shows a lateral aberration diagram of the first embodiment. In this transverse aberration diagram, the numbers shown in parentheses represent (horizontal (X direction) angle of view, vertical (Y direction) angle of view),
The lateral aberration at the angle of view is shown.

The values of the conditional expressions (1) and (1) in Examples 1 to 12 are as follows.

Conditional expression Example 1 2 3 4 5 6 (1) 0.98 0.85 1.12 1.09 0.66 0.65 0.99 0.91 0.89 0.86 1.16 1.39 -0.04 0.86 0.70 0.73 0.50 0.63 -0.48 -0.23 -0.45 -0.15 -0.45 -0.77 0.56 0.10 0.09 -0.02 0.48 0.41 0.59 0.60 0.46 0.49 0.63 0.46 -0.06 0.86 0.66 0.15 0.66 0.33 0.27 0.45 0.55 0.10 0.41 0.37 0.77 0.02 0.22 0.11 0.22 0.50 1.29 1.38 1.23 2.22 1.17 1.07 Conditional expression Example 7.8 9 10 11 12 (1) 0.35 0.40 0.62 0.55 0.75 0.79 1.03 0.99 1.09 1.12 0.75 1.09 0.70 0.83 0.03 1.17 0.61 1.05 -0.15 -0.27 -0.27 -0.57 -0.09 -0.55 0.16 0.11 0.62 -0.28 0.18 -0.25 0.52 0.16 0.32
0.51 0.18 0.50 0.37 0.44 0.68
0.60 0.48 0.53 0.40 0.81 0.48 -0.32 0.69 -0.31 0.69 0.45 0.19 -0.11 0.34 -0.10 0.98 1.15 1.04 0.41 0.97 0.41

The imaging optical system according to the present invention as described above can be used for a photographing apparatus, particularly a camera, which forms an object image and receives the image with an image pickup device such as a CCD or a silver halide film for photographing. it can. It can also be used as an observation device for observing an object image through an eyepiece, particularly as an objective optical system for a finder section of a camera. Further, it can also be used as an imaging optical system for an optical device using a small imaging element such as an endoscope. less than,
The embodiment is illustrated.

FIGS. 14 to 16 are conceptual diagrams showing a configuration in which the imaging optical system of the present invention is incorporated in an objective optical system of a finder section of an electronic camera. 14 is a front perspective view showing the appearance of the electronic camera 40, FIG. 15 is a rear perspective view of the same, and FIG. 16 is a sectional view showing the configuration of the electronic camera 40. Electronic camera 40
In the case of this example, includes a photographing optical system 41 having a photographing optical path 42, a finder optical system 43 having a finder optical path 44, a shutter 45, a flash 46, a liquid crystal display monitor 47, and the like. When the shutter 45 is pressed, the photographing is performed through the photographing objective optical system 48 in conjunction therewith. An object image formed by the photographing objective optical system 48 is formed on the imaging surface 50 of the CCD 49 via a filter 51 such as a low-pass filter or an infrared cut filter. This CCD4
The object image received at 9 is passed through a processing means 52 as an electronic image to a liquid crystal display monitor 47 provided on the back of the camera.
Will be displayed. Further, a memory or the like is arranged in the processing means 52, and a captured electronic image can be recorded. This memory may be provided separately from the processing means 52, or may be configured to perform electronic recording and writing using a floppy disk or the like. Further, a silver halide camera in which a silver halide film is arranged in place of the CCD 49 may be configured.

Further, on the finder optical path 44,
A finder objective optical system 53 is provided, and the finder objective optical system 53 includes a cover lens 54,
The diaphragm 2 includes a first prism 21, a second prism 22, and a focusing lens 66.
As the imaging optical systems up to 2, the same type of optical system as in the seventh embodiment is used. The cover lens 54 used as a cover member is a lens having a negative power, and has an increased angle of view. The focus lens 66 disposed behind the second prism 22 can adjust the position in the front-rear direction of the optical axis, and is used for adjusting the focus of the finder objective optical system 53. The object image formed on the image plane 67 by the finder objective optical system 53 is formed on a field frame 57 of a Porro prism 55 which is an image erecting member. Note that the field frame 57 separates the first reflection surface 56 and the second reflection surface 58 of the Porro prism 55 from each other and is disposed therebetween. This poly prism 5
An eyepiece optical system 59 that guides the erect image to the observer's eyeball E is disposed behind the eyepiece 5.

In the camera 40 configured as described above, the finder objective optical system 53 can be configured with a small number of optical members, high performance and low cost can be realized, and the optical path itself of the objective optical system 53 can be bent. Therefore, the degree of freedom of arrangement inside the camera increases, which is advantageous in design.

Although the configuration of the photographing objective optical system 48 has not been mentioned in the configuration of FIG. 16, the prism of the present invention is not limited to the refraction type coaxial optical system as the photographing objective optical system 48. 10 or two prisms 21,
It is of course possible to use any type of imaging optics consisting of 22.

FIG. 17 is a conceptual diagram showing a configuration in which the image forming optical system of the present invention is incorporated in the objective optical system 48 of the photographing section of the electronic camera 40. In the case of this example, an imaging optical system similar to that of the first embodiment is used as the imaging objective optical system 48 arranged on the imaging optical path 42. The object image formed by the objective optical system for photographing is formed on the imaging surface 50 of the CCD 49 via a filter 51 such as a low-pass filter or an infrared cut filter. The object image received by the CCD 49 is passed through a processing unit 52 to a liquid crystal display (LC).
D) Displayed on 60 as an electronic image. The processing unit 52 also controls a recording unit 61 that records an object image captured by the CCD 49 as electronic information. LCD60
Is guided to the observer's eyeball E via the eyepiece optical system 59. The eyepiece optical system 59 is composed of an eccentric prism having a form similar to that used for the first prism 21 of the imaging optical system of the present invention. In this example, an entrance surface 62, a reflection surface 63, Reflection and refraction surface 64-3
It is composed of faces. Also, at least one of the two reflecting surfaces 63 and 64, desirably both surfaces, provide power to the luminous flux and have only one symmetric surface for correcting eccentric aberration. It is composed of curved surfaces. The only symmetric surface is formed on substantially the same plane as the only symmetric free-form surface of the prism 10 of the objective optical system 48 for photographing. The objective optical system 48 for photographing includes another lens (positive lens, negative lens).
May be included on the object side or the image side of the prism 10 as a component thereof.

In the camera 40 thus configured, the photographing objective optical system 48 can be composed of a small number of optical members, high performance and low cost can be realized, and the entire optical system can be arranged on the same plane. Thus, it is possible to realize the thickness of the thickness in the direction perpendicular to the arrangement plane.

In this embodiment, a parallel flat plate is arranged as the cover member 65 of the photographing objective optical system 48, but a lens having power may be used as in the previous embodiment.

Here, without providing the cover member, the surface of the imaging optical system according to the present invention which is arranged closest to the object may be used also as the cover member. In this example, the surface closest to the object is the incident surface of the prism 10. However, since this incident surface is eccentrically arranged with respect to the optical axis, if this surface is arranged in front of the camera, the photographing center of the camera 40 is shifted from itself when viewed from the subject side. This is an illusion (similar to a general camera, it is usual to sense that the image is taken in the vertical direction of the incident surface), giving a sense of incongruity. Therefore, when the surface closest to the object side of the imaging optical system is an eccentric surface as in the present example, providing the cover member 65 (or the cover lens 54) may cause an uncomfortable feeling when viewed from the subject side. It is desirable to be able to receive photography with the same feeling as an existing camera without feeling.

FIG. 18 shows an image forming optical system according to the present invention as an objective optical system 82 of an observation system of an electronic endoscope, and an image forming optical system according to the present invention as an eyepiece optical system of an observation system of an electronic endoscope. The conceptual diagram of the structure incorporated in the system 87 is shown. In this example, the objective optical system 82 of the observation system uses the same optical system as that of the seventh embodiment, and the eyepiece optical system 87 also uses the same optical system of the seventh embodiment. As shown in FIG. 18A, the electronic endoscope includes an electronic endoscope 71, a light source device 72 that supplies illumination light, and a video processor 73 that performs signal processing corresponding to the electronic endoscope 71. And this video processor 7
A monitor 74 for displaying the video signal output from
A VTR deck 75 connected to the video processor 73 for recording video signals and the like, and a video disk 76;
A video printer 77 that prints out a video signal as a video, and a head-mounted image display device (HMD) 78 are provided. Is configured as shown in FIG. The luminous flux illuminated from the light source device 72 is
The observation site is illuminated by the illumination objective optical system 89 through the light guide fiber bundle 88. Then, light from the observation site is formed as an object image by the observation objective optical system 82 via the cover member 85. This object image is formed on the imaging surface of the CCD 84 via a filter 83 such as a low-pass filter or an infrared cut filter. Further, this object image is converted into a video signal by the CCD 84, and the video signal is directly displayed on the monitor 74 by the video processor 73 shown in FIG.
6 and printed out from the video printer 77 as a video. The information is displayed on the image display device of the HMD 78 and displayed to the wearer of the HMD 78. At the same time, the image signal converted by the CCD 84 is displayed as an electronic image on a liquid crystal display (LCD) 86 of the eyepiece 81, and the displayed image passes through an eyepiece optical system 87 comprising an observation optical system of the present invention. It is led to the eyeball E.

The endoscope constructed as described above can be constituted by a small number of optical members, high performance and low cost can be realized, and the objective optical system 80 is arranged in the longitudinal direction of the endoscope.
The above effect can be obtained without inhibiting the reduction in diameter.

Incidentally, the imaging optical system can be used also as a projection optical system by reversing the optical path. FIG.
9 shows a conceptual diagram of a configuration in which a prism optical system according to the present invention is used as a projection optical system 96 of a presentation system in which a personal computer 90 and a liquid crystal projector 91 are combined. In the case of this example, an imaging optical system similar to that of the first embodiment is used for the projection optical system 96 with the optical path reversed. In the figure, image / document data created on the personal computer 90 is:
The signal is branched from the monitor output and output to the processing control unit 98 of the liquid crystal projector 91. The processing control section 98 of the liquid crystal projector 91 processes the input data and outputs the processed data to the liquid crystal panel (LCP) 93. The liquid crystal panel 93 displays an image corresponding to the input image data. After the amount of light transmitted from the light source 92 is determined by the gradation of the image displayed on the liquid crystal panel 93, the field lens 95 disposed immediately before the liquid crystal panel 93 and the image forming optical system of the present invention are formed. The light is projected on a screen 97 via a projection optical system 96 including a prism 10 and a cover lens 94 as a positive lens.

The projector configured as described above can be configured with a small number of optical members, can achieve high performance and low cost, and can be downsized.

Next, FIG. 20 shows a desirable configuration when the imaging optical system according to the present invention is arranged in front of an image pickup device such as a CCD or a filter. In the figure, an eccentric prism P is an image side portion or a second prism of a prism member included in the imaging optical system of the present invention. Now, the imaging surface C of the imaging device
Form a square as shown in FIG.
It is desirable from the standpoint of beautiful image formation that the symmetry plane F of the plane-symmetric free-form surface arranged at is arranged in parallel with at least one of the sides forming the quadrangle of the imaging plane C.

Further, when the imaging surface C has four interior angles, such as a square and a rectangle, each formed at substantially 90 °, the plane of symmetry F of the plane-symmetric free-form surface is parallel to the imaging surface C. It is arranged in parallel with certain two sides, more desirably, arranged in the middle of these two sides, and the configuration is such that the symmetry plane F coincides with the position where the imaging plane C is symmetrical left and right or up and down. preferable. With this configuration, it is easy to obtain the accuracy of assembling into the device,
It is effective for mass production.

In the case where a plurality or all of the optical surfaces constituting the decentered prism P, ie, the third reflecting surface, the fourth reflecting surface, and the first exit surface, are plane-symmetric free-form surfaces, a plurality of surfaces are required. It is desirable from the viewpoint of both design and aberration performance that the surface or the plane of symmetry of all surfaces is arranged on the same surface F.
It is desirable that the relationship between the symmetry plane F and the imaging plane C be the same as described above.

The above-described image forming optical system of the present invention can be constituted, for example, as follows.

[1] In an imaging optical system having an overall positive refractive power for forming an object image, the imaging optical system is formed of a medium having a refractive index (n) larger than 1 (n> 1). A prism member, the prism member, from the object side, at least, a first incident surface to enter a light beam into the prism, a first to fourth reflection surface to reflect the light beam in the prism, First to emit light beam outside prism
An emission surface, wherein the first incidence surface and the second reflection surface are configured so that a single surface performs both a transmission operation and a reflection operation by total reflection, and the first incidence surface And the first reflection surface and the second reflection surface form a folded optical path, and the third reflection surface, the fourth reflection surface, and the first emission surface rotate a light beam along a triangular optical path. And an optical path incident on the third reflecting surface and an optical path guided from the fourth reflecting surface to the first exit surface are arranged so as to form an intersection optical path, and the first reflecting surface and the second At least one of the two reflecting surfaces has a curved shape that gives power to the light beam, and the curved shape is a rotationally asymmetric surface shape that corrects aberrations caused by eccentricity, and the third reflection surface At least one surface of the surface and the fourth reflection surface, A curved surface shape that gives power to the bundle, wherein the curved surface shape is configured by a rotationally asymmetric surface shape that corrects aberrations caused by eccentricity, and in a light path between the first reflection surface and the fourth reflection surface. An aperture is arranged on the entrance side of the first entrance surface, and an axial distance from the aperture to the first entrance surface is defined as ER.
When the eccentric direction of all the optical systems is the Y-axis direction, the plane parallel to the axial principal ray is the YZ plane, and the direction orthogonal to the YZ plane is the X direction, The focal length in the direction
When y, ER / Fy ≦ 2.0 (1) is satisfied, and at least one of the following nine conditions is satisfied. Imaging optical system: 0.1 <Px1-1 / | Px | <3 ... -0.5 <Py1-1 / | Py | <3 ...- 2 <Px1-2 / | Px | <1 ...- 1 <Py1-2 / | Py | <1 ...- 0.5 <Px2-1 / | Px | <1.5 ...- 0.5 <Py2-1 / | Py | <1.5 ...- 1 <Px2-2 / | Px | <1.5 ...- 1 <Py2-2 / | Py | <1.5 ...- 1 <Px2 / Py2 <5 ... However, the power in the X direction of all optical systems is Px, the power in the Y direction is Py, and the power in the X direction of the first, second, third, and fourth reflecting surfaces is Px1. -1, Px1-
2, Px2-1, Px2-2, and the power in the Y direction
y1-1, Py1-2, Py2-1, Py2-2, and (Px2-1
+ Px2-2) / (Py2-1 + Py2-2) to Px2 / P
y2.

[2] In the above item 1, the above 9
An imaging optical system characterized in that at least two of the conditions are satisfied.

[3] In the above item 1, the above 9
An imaging optical system characterized in that at least three of the three conditions are satisfied.

[4] In the above item 1, the above 9
An imaging optical system characterized in that at least four of the conditions are satisfied.

[5] In the above item 1, the above 9 to 9
An imaging optical system characterized in that at least five of the conditions are satisfied.

[6] In the above item 1, the above 9
An imaging optical system characterized in that at least six of the conditions are satisfied.

[7] In the above item 1, the above 9
An imaging optical system characterized in that at least seven of the conditions are satisfied.

[8] In the above item 1, the above 9
An imaging optical system characterized in that at least eight of the conditions are satisfied.

[0171]

[9] In the above item 1, the above 9
An imaging optical system characterized by satisfying all three conditions.

[10] In any one of the above items 1 to 9, the prism member may be configured so that the first incident surface and the first incident surface are in contact with each other.
The connection is characterized by being constituted by a single prism formed by joining or integrally forming the reflection surface, the second reflection surface, the third reflection surface, the fourth reflection surface, and the first exit surface. Image optics.

[11] In any one of the aforementioned items 1 to 9, the prism member may be configured so that the first incident surface and the first incident surface are in contact with each other.
A first prism having a reflecting surface and the second reflecting surface, and a first prism having the third reflecting surface, the fourth reflecting surface, and the first exit surface, and being spaced apart from the first prism. An imaging optical system comprising two prisms.

[12] In any one of the aforementioned items 1 to 9, the prism member may be configured so that the second reflection surface and the third reflection surface are connected to each other.
A fifth reflecting surface for reflecting a light beam in the prism between the reflecting surface and the first reflecting surface, the first reflecting surface, the second reflecting surface, the fifth reflecting surface, and the third reflecting surface; An imaging optical system, comprising: a single prism formed by joining or integrally forming the first reflecting surface and the fourth reflecting surface and the first exit surface.

[13] In any one of the aforementioned items 1 to 9, the prism member may include the second reflecting surface and the third reflecting surface.
A first prism having a fifth reflecting surface for reflecting a light beam in the prism between the reflecting surface and the first reflecting surface, the first reflecting surface, the second reflecting surface, and the fifth reflecting surface; And a second prism having the third reflecting surface, the fourth reflecting surface, and the first exit surface, and a second prism spaced from the first prism. Image optics.

[14] In any one of the above items 10 to 13, both the first reflecting surface and the second reflecting surface may be
An imaging optical system characterized in that it is configured to have a rotationally asymmetric surface shape that applies power to a light beam and corrects aberration generated by decentering.

[15] In the above item 12 or 13, all of the three surfaces of the first reflecting surface, the second reflecting surface and the fifth reflecting surface apply power to a light beam and correct aberrations caused by eccentricity. An imaging optical system, which is configured to have a rotationally asymmetric surface shape.

[16] In any one of the above items 1 to 15, both the third reflecting surface and the fourth reflecting surface may be a rotationally asymmetric surface which applies power to a light beam and corrects aberrations caused by eccentricity. An imaging optical system, which is configured to have a shape.

[17] In any one of the above items 1 to 16, the first exit surface may be configured to have a rotationally asymmetric surface shape for applying power to a light beam and correcting aberrations caused by eccentricity. An imaging optical system characterized in that:

[18] In the above-mentioned item 11 or 13, at least one of the exit surface of the first prism and the entrance surface of the second prism applies a power to the light beam and corrects an aberration generated by eccentricity. An imaging optical system, which is configured to have an asymmetric surface shape.

[19] In the above item [18], both the exit surface of the first prism and the entrance surface of the second prism are rotationally asymmetric surfaces which apply power to the light beam and correct aberrations caused by eccentricity. An imaging optical system, which is configured to have a shape.

[20] In any one of the above items 1 to 19, the rotationally asymmetric surface shape may be such that only one symmetric surface is one.
An imaging optical system characterized by having a plane-symmetric free-form surface shape having only surfaces.

[21] In any one of the aforementioned items 1 to 20, the intermediate image surface is formed by a rotationally asymmetric surface,
The optically active surface disposed on the object side and the optically active surface disposed on the imaging surface side with respect to the intermediate image plane are configured to compensate for each other and correct eccentric aberration. Characteristic imaging optical system.

[22] The imaging optical system according to any one of the above 1 to 21 is arranged as a finder objective optical system, and further, an image corrector for erecting an object image formed by the finder objective optical system. A finder optical system comprising a vertical optical system and an eyepiece optical system.

[23] A camera device comprising: the finder optical system according to the above item 22, and a photographing objective optical system provided in parallel with the finder optical system.

[24] The imaging optical system according to any one of the above items 1 to 21, and an image pickup device arranged on an image plane formed by the imaging optical system. An imaging optical system characterized by the above-mentioned.

[25] The imaging optical system according to any one of the above items 1 to 21 is disposed as an objective optical system for imaging, and an optical path different from the optical system for imaging or the objective optical system for imaging. And a finder optical system disposed in any one of the optical paths divided from the optical path.

[26] The imaging optical system according to any one of the above items 1 to 21, an imaging device arranged on an image plane formed by the imaging optical system, and light received by the imaging device. An electronic camera apparatus, comprising: a recording medium for recording image information; and an image display element for forming an observation image by receiving image information from the recording medium or the imaging element.

[27] An observation system comprising: the imaging optical system according to any one of the above items 1 to 21; and an image transmitting member that transmits an image formed by the imaging optical system along a long axis direction. An endoscope apparatus comprising: an illumination light source; and an illumination system having an illumination light transmission member that transmits illumination light from the illumination light source along the long axis direction.

[0190]

As is apparent from the above description, according to the present invention, a high-performance and low-cost imaging optical system can be provided with a small number of optical elements. In addition, by folding the optical path using a reflection surface with a small number of reflections, it is possible to provide a high-performance imaging optical system that is reduced in size and thickness.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an imaging optical system according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of an imaging optical system according to a second embodiment of the present invention.

FIG. 3 is a sectional view of an imaging optical system according to a third embodiment of the present invention.

FIG. 4 is a sectional view of an imaging optical system according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of an imaging optical system according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view of an imaging optical system according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view of an imaging optical system according to a seventh embodiment of the present invention.

FIG. 8 is a sectional view of an imaging optical system according to Example 8 of the present invention.

FIG. 9 is a sectional view of an imaging optical system according to a ninth embodiment of the present invention.

FIG. 10 is a sectional view of an imaging optical system according to a tenth embodiment of the present invention.

FIG. 11 is a sectional view of an imaging optical system according to Example 11 of the present invention.

FIG. 12 is a sectional view of an imaging optical system according to Example 12 of the present invention.

FIG. 13 is a lateral aberration diagram of the imaging optical system of the first embodiment.

FIG. 14 is a front perspective view showing the appearance of an electronic camera to which the imaging optical system of the present invention is applied.

15 is a rear perspective view of the electronic camera of FIG.

16 is a cross-sectional view illustrating a configuration of the electronic camera in FIG.

FIG. 17 is a conceptual diagram of another electronic camera to which the imaging optical system of the present invention is applied.

FIG. 18 is a conceptual diagram of an electronic endoscope to which the imaging optical system of the present invention is applied.

FIG. 19 is a conceptual diagram of a configuration using a prism optical system according to the present invention as a projection optical system of a presentation system.

FIG. 20 is a diagram showing a desirable configuration when an imaging optical system according to the present invention is arranged in front of an image sensor.

FIG. 21 is a conceptual diagram for explaining field curvature generated by an eccentric reflecting surface.

FIG. 22 is a conceptual diagram for describing astigmatism generated by a decentered reflecting surface.

FIG. 23 is a conceptual diagram for explaining coma generated by a decentered reflecting surface.

FIG. 24 is a diagram for describing the definition of the power of the decentered optical system and the optical surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... On-axis chief ray 2 ... Stop (pupil) 3 ... Image plane 4 ... Intermediate image plane 10 ... Prism 11 ... 1st entrance surface 12 ... 1st reflection surface 13 ... 2nd reflection surface 14 ... 3rd reflection surface 15 ... 4th reflection surface 16 ... 1st emission surface 17 ... 5th reflection surface 18 ... 2nd emission surface 19 ... 2nd incidence surface 21 ... 1st prism 22 ... 2nd prism 40 ... electronic camera 41 ... photography optical system 42 ... photography Reference optical path 43 ... Finder optical system 44 ... Finder optical path 45 ... Shutter 46 ... Flash 47 ... Liquid crystal display monitor 48 ... Photo objective optical system 49 ... CCD 50 ... Imaging surface 51 ... Filter 52 ... Processing means 53 ... Finder optical objective System 54 Cover lens 55 Porro prism 56 First reflection surface 57 Field frame 58 Second reflection surface 59 Eyepiece optical system 60 Liquid crystal display element (LCD) 61 Recording means 62 Incident surface 63 Reflective surface 64 Surface for both reflection and refraction 65 Cover member 66 Focusing lens 67 Image forming surface 71 Electronic endoscope 72 Light source device 73 Video processor 74 Monitor 75 VTR deck 76 ... Video disc 77 ... Video printer 78 ... Head mounted image display device (HMD) 79 ... Insertion section 80 ... Tip section 81 ... Eyepiece section 82 ... Observation objective optical system 83 ... Filter 84 ... CCD 85 ... Cover member 86 ... Liquid crystal display element (LCD) 87 ... Eyepiece optical system 88 ... Light guide fiber bundle 89 ... Objective optical system for illumination 90 ... PC 91 ... Liquid crystal projector 92 ... Light source 93 ... Liquid crystal panel (LCP) 94 ... Cover lens 95 ... Field lens Reference numeral 96: projection optical system 97: screen 98: processing control unit M: concave mirror S: decentered optical system E: Observer's eyeball P: decentered prism C: imaging plane F: plane of symmetry of a plane-symmetric free-form surface

Claims (3)

[Claims] 1. An imaging optical system having an overall positive refractive power for forming an object image, wherein the imaging optical system has a refractive index (n) greater than 1 (n
> 1) having a prism member formed of a medium, wherein the prism member receives at least a first incident surface from the object side that allows a light beam to enter the prism, and a first to a second surface that reflects the light beam within the prism. 4 reflecting surface, and a first exit surface for emitting a light beam outside the prism, wherein the first incident surface and the second reflecting surface perform a transmissive action and a reflective action by a total reflection action on one surface. The first reflection surface, the first reflection surface, and the second reflection surface form a folded optical path, and the third reflection surface, the fourth reflection surface, and the first reflection surface. An exit surface rotates a light beam along a triangular optical path, and an intersection optical path is formed by an optical path incident on the third reflection surface and an optical path guided from the fourth reflection surface to the first exit surface. The first reflection surface and the front surface At least one of the second reflection surface and the second reflection surface has a curved surface shape that gives power to the light beam, and the curved surface shape is configured to have a rotationally asymmetric surface shape that corrects an aberration generated by eccentricity. At least one of the third reflection surface and the fourth reflection surface has a curved surface shape that gives power to a light beam, and the curved surface shape is configured to have a rotationally asymmetric surface shape that corrects aberration generated by eccentricity, A first image forming unit configured to form an intermediate image surface in an optical path between the first reflecting surface and the fourth reflecting surface; a stop arranged on an incident side of the first incident surface; The eccentric direction of the entire optical system is the Y-axis direction, the plane parallel to the axial chief ray is the YZ plane, and the direction orthogonal to the YZ plane is the X direction. The focal length in the Y direction of all optical systems is Fy
Then, ER / Fy ≦ 2.0 (1) is satisfied, and at least one of the following nine conditions is satisfied. Imaging optical system: 0.1 <Px1-1 / | Px | <3 ... -0.5 <Py1-1 / | Py | <3 ...- 2 <Px1-2 / | Px | < 1 ...- 1 <Py1-2 / | Py | <1 ...- 0.5 <Px2-1 / | Px | <1.5 ...- 0.5 <Py2-1 / | Py | <1.5 ...- 1 <Px2-2 / | Px | <1.5 ...- 1 <Py2-2 / | Py | <1.5 ...- 1 <Px2 / Py2 <5 ... However, the power in the X direction of all the optical systems is Px, the power in the Y direction is Py, and the power in the X direction of the first, second, third, and fourth reflecting surfaces is Px1−. 1, Px1-
2, Px2-1, Px2-2, and the power in the Y direction
y1-1, Py1-2, Py2-1, Py2-2, and (Px2-1
+ Px2-2) / (Py2-1 + Py2-2) to Px2 / P
y2. 2. The device according to claim 1, wherein the prism member includes the first incident surface, the first reflective surface, the second reflective surface, the third reflective surface, the fourth reflective surface, and the first exit surface. And a single prism formed by bonding or integral molding. 3. The first prism according to claim 1, wherein the prism member includes a first prism having the first incident surface, the first reflection surface, and the second reflection surface, and the third prism.
An imaging optical system comprising: a first prism having a reflecting surface, the fourth reflecting surface, and the first exit surface, and a second prism disposed at an interval.