JP2003050361A - Real image type finder optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a real image type finder optical system equipped with an image erection optical system, constituted suitable to the miniaturization/cost reduction of a camera while maintaining a good optical performance. SOLUTION: The optical system is provided with an objective lens group 10, an image reversing optical system 20 and an eyepiece group 30. The image reversing optical system 20 is provided with a 1st image reversing optical system 21 and a 2nd image reversing optical system 22. An intermediate image forming surface is arranged near the incident surface 2A of the 2nd image reversing optical system. Light is made incident on the incident surface 1A of the 1st image reversing optical system 21, then, reflected by respective optical surfaces 1B, 1C and 1D in this order, and then, emitted from the surface 1C functioning as a reflection surface and also as a transmissive surface. Thereafter, the light is made incident on the incident surface 2A of the 2nd image reversing optical system 22, then, reflected by respective optical surfaces 2B and 2C in this order, and then, emitted from the surface 2B functioning as a reflection surface and also as a transmissive surface. Mirror coating is applied on the optical surfaces 1B and 1D, the optical surface 2C is a roof reflection part, and all the refractive/refection surfaces are constituted so as to be rotation-symmetrical surfaces including a plane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a real image type finder optical system, and more particularly to a real image suitable for use in a lens shutter camera, an electronic still camera or the like in which a photographing optical system and a finder optical system are separately configured. System finder optical system.

[0002]

2. Description of the Related Art As a finder used in a lens shutter camera, a virtual image type finder and a real image type finder are generally known. However, in order to miniaturize the camera, the virtual image type has a large lens diameter. Therefore, a real image finder is used.

In recent years, in order to make each manufacturer competitive,
The cost of cameras is becoming lower. At the same time, with the further miniaturization of cameras, further miniaturization of the mounted finder optical system is required. Particularly, as a finder optical system corresponding to a so-called thin camera in which the size of the camera in the depth direction is suppressed, there is disclosed in Japanese Patent Application Laid-Open No. 12-3964.
9, JP-A-11-211998, JP-A-11-38.
211, JP-A-10-284222, and JP-A-2000
-227622 and Japanese Patent Laid-Open No. 2001-75023. JP-A-2000-22
7622 and JP-A-12-39649, a combination of a roof prism and a Reman prism is disclosed in JP-A-11-21.
In 1998 and Japanese Patent Application Laid-Open No. 10-284222, a combination of three prisms including a roof prism is disclosed.
-38211 combines a prism having an isosceles triangular prism shape with three reflecting surfaces and a prism having an isosceles triangular prism shape having a roof reflecting portion, and in Japanese Patent Laid-Open No. 2000-227622,
A combination of two prisms including a roof prism, in Japanese Patent Laid-Open No. 2001-75023, a combination of two prisms including a roof prism and a rotationally asymmetric free-form surface in which a transmission surface is inclined with respect to an optical axis is used for a thin camera. It has a finder optical system.

However, it is hard to say that these finder optical systems are capable of coping with both cost reduction and miniaturization which are being advanced at the same time. JP-A-12-3
In 9649 and Japanese Patent Laid-Open No. 11-38211, the size of the camera in the thickness direction is certainly small, but the space in front of the prism (on the object side) is small, and the space for the AF unit, AE unit, etc. is small. When arranging the camera components, in order to miniaturize and guarantee accuracy,
Inevitably, an expensive small unit must be used, and conversely, a large size unit must be used in order to make it inexpensive, which increases the thickness of the camera,
Both cost reduction and miniaturization cannot be achieved at the same time. Japanese Patent Laid-Open No. 11-2
In 11998, in addition to using three prisms (or two prisms + one mirror), there is a transmissive surface on which the optical axis is obliquely incident, so coating on one of the ghost upper transmissive surfaces is required. It is preferable to give it, and it becomes more expensive. In addition, performance deterioration occurs on the transmission surface. Also in Japanese Unexamined Patent Publication No. 10-284222, since three prisms (or two prisms + one mirror) are used, the cost of the finder itself becomes high. The first embodiment of JP-A-2000-227622 has a configuration in which the arrangements of a first image inverting optical system and a second image inverting optical system of the present invention described later are reversed, but in this configuration, the eyepiece side The prism placed on
This is inconvenient because the tip end portion protrudes into the space in front of the prism where the AF unit, AE unit, etc. are arranged. Japanese Unexamined Patent Application Publication No. 2001-75023 is premised on the use of a free-form surface that is not rotationally symmetric, such as by tilting the prism entrance surface, and cannot cope with cost reduction in terms of processing and assurance of component accuracy.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art,
It is an object of the present invention to provide a real image type viewfinder optical system including an image erecting optical system having a configuration suitable for downsizing and cost reduction of a camera while maintaining good optical performance.

[0006]

In order to achieve the above object, a real image type finder optical system according to the present invention comprises, in order from the object side, an objective lens group having a positive refractive power, an image inverting optical system, and an eyepiece lens having a positive refractive power. In the real image type finder optical system having a group, the image inversion optical system, in order from the object side,
A first image inverting optical system and a second image inverting optical system are provided, and an intermediate image forming surface formed by the objective lens group is an exit surface of the first image inverting optical system to an entrance surface of the second image inverting optical system. Arranged in the vicinity, the first image inverting optical system is incident from the incident surface 1A so that the optical axes do not intersect in the optical system, and reflected in this order on each of the optical surfaces 1B, 1C, and 1D, It is configured so that the light is emitted from an optical surface 1C that also serves as a reflecting surface and a transmitting surface, and the second image inverting optical system is made incident from the incident surface 2A so that the optical axes do not intersect in the optical system, and then the optical surface 2B. 2C, the optical surfaces 1B,
At least one of 1D and 2C is a roof reflection part, all transmission surfaces are perpendicular to the optical axis, and the following conditions are satisfied.

30 ° <θ <55 ° (1) 40 ° <Ψ <70 ° (2) where θ is the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B. The angle ψ formed by the optical surface 1B and the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C.
It is an angle with C.

Another real image type finder optical system of the present invention is a real image type finder optical system having, in order from the object side, an objective lens group having a positive refractive power, an image inverting optical system, and an eyepiece lens group having a positive refractive power. In the system, the image inverting optical system includes a first image inverting optical system and a second image inverting optical system in order from the object side, and an intermediate image forming surface formed by an objective lens group is the first image inverting optical system. The first image reversing optical system is disposed near the exit surface of the system or the incident surface of the second image reversing optical system, and the first image reversing optical system is arranged so that the optical axes do not intersect in the optical system.
From the optical surface 1C, which serves as both a reflecting surface and a transmitting surface, and is reflected by the optical surfaces 1B, 1C, and 1D in this order, and is emitted from the optical surface 1C. Inject from the incident surface 2A so that the optical axes do not intersect in the system,
The optical surfaces 2B and 2C are configured to be reflected in this order and emitted from the optical surface 2B that also serves as a reflecting surface and a transmitting surface, and at least one of the optical surfaces 1B, 1D, and 2C is a roof reflector. , All the transmitting surfaces are perpendicular to the optical axis, and the following conditions are satisfied.

30 ° <θ <56 ° (3) 30 ° <Ψ <70 ° (4) where θ is the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B. The angle ψ formed by the optical surface 1B and the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C.
It is an angle with C.

Still another real image type finder optical system of the present invention is a real image type finder optical system having, in order from the object side, an objective lens group having a positive refractive power, an image inverting optical system, and an eyepiece lens group having a positive refractive power. In, while configuring the image inverting optical system so that the optical axis does not intersect in the optical system,
It is characterized by satisfying the following conditions.

29 ° <α <75 °, (11) 0.1 <L ₂ / L ₁ <0.49 (12) where α is the optical axis passing through the intermediate image plane. The angle formed by the optical axis of the objective lens group, L _1, is the intersection of the surface of the objective lens group closest to the object side and the optical axis of the objective lens group, and The distance to the intersection of the reflecting surface and the optical axis is the distance projected on the optical axis of the objective lens group, and L ₂ is the intermediate point from the intersection of the final reflecting surface of the image inverting optical system and the optical axis. The distance from the image plane to the intersection of the first reflecting surface of the image inverting optical system and the optical axis is the distance projected on the optical axis of the objective lens group.

Still another real image type finder optical system according to the present invention is such that the first specification is such that the in-field display means is arranged near the intermediate image forming surface, and the second specification is near the intermediate image forming surface. In a real-image finder optical system with an image inversion optical system in which is an air gap, the position of the entrance surface of the image inversion optical system closer to the eyepiece than the vicinity of the intermediate image plane is shifted along the optical axis. By applying it, it is characterized in that the deviation of the diopter between the first specification and the second specification is corrected.

Hereinafter, the reason why the above structure is adopted and the operation thereof will be described.

As described above, the first real image type finder optical system according to the present invention has a real image having, in order from the object side, an objective lens group having a positive refractive power, an image inverting optical system, and an eyepiece lens group having a positive refractive power. In the type finder optical system, the image inverting optical system includes a first image inverting optical system and a second image inverting optical system in order from the object side, and the intermediate image forming surface formed by the objective lens group is the first image inverting optical system. It is arranged near the exit surface of the image inverting optical system or the entrance surface of the second image inverting optical system, and is incident on the first image inverting optical system from the entrance surface 1A so that the optical axes do not intersect in the optical system. The optical surface 1C that serves as both a reflective surface and a transmissive surface by reflecting in this order on each of the optical surfaces 1B, 1C, and 1D.
And the second image inversion optical system,
At least one of the optical surfaces 1B, 1D, and 2C is configured such that the light enters from the incident surface 2A so that the optical axes do not intersect in the optical system and is reflected in this order on each of the optical surfaces 2B and 2C. One is a roof reflection part, all the transmission surfaces are perpendicular to the optical axis, and the following conditions are satisfied.

30 ° <θ <55 ° (1) 40 ° <Ψ <70 ° (2) where θ is the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B. The angle ψ formed by the optical surface 1B and the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C.
It is an angle with C.

Here, the first image inverting optical system has three reflecting surfaces, and by arranging the optical system so that the optical axes do not intersect with each other, the effective range of the reflecting and transmitting surfaces of the optical system. It enables a miniaturized layout that partially overlaps.

Of the three reflecting surfaces, the size in the thickness direction of the camera is reduced by reflection of the optical surfaces 1B and 1C, and at the same time, the space in front of the prism can be increased by reflection of the optical surface 1D. ing. In this configuration, the optical surface 1C is made to have both the function of reflection and the function of transmission, thereby enabling downsizing.

The second image inverting optical system is constructed so that the size in the thickness direction of the camera can be reduced by reflection on the optical surface 2B, and at the same time the space in front of the prism can be increased by reflection on the optical surface 2C. There is. In this configuration, since the exit surface 2D of the second image inverting optical system is not necessarily the same surface as the optical surface 2B, it is possible to configure the second image inverting optical system with a hollow mirror prism, which leads to size reduction and low cost. It corresponds to the change.

Further, by making all the transmission surfaces perpendicular to the optical axis, it is possible to eliminate the deviation of the performance within the visual field and obtain a good observation image.

When θ becomes smaller than the lower limit of 30 ° of the conditional expression (1), the size of the first image inverting optical system becomes large and the cost becomes high. In addition, the optical surface is formed by the optical surfaces 1C and 1D. When the tip end projects into the space in front of the prism and camera components such as the AF unit and AE unit are placed in that space, a more expensive small unit must be used in order to downsize and ensure accuracy. In order to obtain an inexpensive structure, on the contrary, a large size unit must be used, which increases the thickness of the camera, which makes it impossible to achieve both low cost and downsizing. If the upper limit of 55 ° in conditional expression (1) is exceeded, it becomes difficult to satisfy the conditions for total reflection on the optical surfaces 1C and 2B at the same time. This is necessary, which is disadvantageous in terms of performance such as uniformity of brightness within the field of view and cost.

Similarly, when Ψ becomes smaller than the lower limit of 40 ° of the conditional expression (2), it becomes difficult to simultaneously satisfy the total reflection conditions on the optical surfaces 1C and 2B, and the upper limit of 70 ° is exceeded. If it becomes large, the size of the first image inversion optical system becomes large, which is inconvenient.

The second real image type finder optical system of the present invention is a real image type finder optical system having, in order from the object side, an objective lens group having a positive refractive power, an image inverting optical system, and an eyepiece lens group having a positive refractive power. In the system, the image inverting optical system comprises
A first image inverting optical system and a second image inverting optical system are provided in order from the object side, and an intermediate image forming surface formed by the objective lens group is an exit surface of the first image inverting optical system or the second image inverting surface. The first image reversing optical system is arranged near the entrance surface of the optical system and enters the first image inversion optical system from the entrance surface 1A so that the optical axes do not intersect in the optical system. It is configured to reflect in this order and to be emitted from the optical surface 1C that also serves as a reflecting surface and a transmitting surface, and the second image inverting optical system is made to enter from the incident surface 2A so that the optical axes do not intersect in the optical system. The optical surfaces 2B and 2C are reflected in this order and emitted from the optical surface 2B that also serves as a reflecting surface and a transmitting surface, and at least one of the optical surfaces 1B, 1D and 2C is a roof reflector. And all the transmitting surfaces are perpendicular to the optical axis and satisfy the following conditions. It is set to.

30 ° <θ <56 ° (3) 30 ° <Ψ <70 ° (4) where θ is the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B. The angle ψ formed by the optical surface 1B and the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C.
It is an angle with C.

Here, the first image inverting optical system has three reflecting surfaces, and by arranging them so that the optical axes do not intersect in the optical system, the effective range of the reflecting and transmitting surfaces of the optical system is increased. It enables a miniaturized layout that partially overlaps.

Of the three reflecting surfaces, the size in the thickness direction of the camera can be reduced by reflecting the optical surfaces 1B and 1C, and at the same time, the space in front of the prism can be increased by reflecting the optical surface 1D. ing. In this configuration, the optical surface 1C is made to have both the function of reflection and the function of transmission, thereby enabling downsizing.

The second image inverting optical system is constructed so that the size in the thickness direction of the camera can be reduced by reflection on the optical surface 2B, and at the same time, the space in front of the prism can be increased by reflection on the optical surface 2C. There is. In this configuration, by making the optical surface 2B have both the function of reflection and the function of transmission, the size of the second image inversion optical system in the width direction of the camera can be suppressed to a small size, which corresponds to downsizing and cost reduction. ing.

By making all the transmitting surfaces perpendicular to the optical axis,
The deviation of the performance within the visual field is eliminated, and a good observation image can be obtained.

If the lower limit of 30 ° to condition (3) is not reached, the size of the first image reversing optical system becomes large and the cost becomes high. In addition, the tip end formed by the optical surfaces 1C and 1D. Protrudes into the space in front of the prism, and when arranging camera components such as AF unit and AE unit in that space, it is necessary to use a more expensive small unit in order to downsize and ensure accuracy. On the contrary, in order to make the configuration inexpensive, a large-sized unit must be used, which increases the thickness of the camera, which makes it impossible to achieve both low cost and downsizing.

When the value exceeds the upper limit of 56 ° in the conditional expression (3), it becomes difficult to simultaneously satisfy the conditions for total reflection on the optical surfaces 1C and 2B. A coat or the like is required, which is disadvantageous in terms of performance such as uniformity of brightness in the visual field and cost.

Similarly, when Ψ becomes smaller than the lower limit of 40 ° of the conditional expression (4), it becomes difficult to simultaneously satisfy the total reflection conditions on the optical surfaces 1C and 2B, and the upper limit of 70 ° is exceeded. If it becomes large, the size of the first image inversion optical system becomes large, which is inconvenient.

Further, all refracting surfaces and reflecting surfaces are surfaces having rotationally symmetric curvatures including planes, thereby eliminating costly causes such as molding of prisms having complicated shapes and surface accuracy management. It is possible to reduce the cost.

Further, the angle between the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B is θ, and the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C and the optical surface 1C. When the angle formed is Ψ, the optical surface 1C is reflected by the optical surface 1C.
Ψ / 2 is the angle between the optical axis of the ray incident on D and the optical surface 1D.
In addition, the angle between the optical axis of the light ray incident from the optical surface 2A and the optical surface 2B is 180 ° −2θ−Ψ, and the optical axis of the light ray reflected by the optical surface 2B and incident on the optical surface 2C and the optical 2C. By setting the angle of each reflecting surface so that the angle formed is 90 ° −θ− (Ψ / 2), the optical axis of the objective lens group and the optical axis of the eyepiece lens group can be arranged substantially parallel to each other. This makes it possible to make the direction of the object observed through the viewfinder and the direction of the eye looking into the viewfinder eyepiece lens substantially the same.

Further, it is desirable that the following conditions are satisfied.

40 ° <θ <56 ° (5) 30 ° <Ψ <58 ° (6) By making the value of θ larger than the lower limit of 40 ° of the conditional expression (5), It is possible to make the image reversing optical system smaller and less expensive. In addition, the value of Ψ is defined by conditional expression (6)
By making it smaller than the upper limit value of 58 °, it becomes possible to reduce the size and cost of the image inverting optical system similarly.

Further, when the refractive index of the glass material used for the first image inverting optical system is N _d1 and the refractive index of the glass material used for the second image inverting optical system is N _d2 , N _d1 , N _d2 and θ,
Ψ preferably satisfies the following conditions.

N _d1 <1.6 (7) N _d2 <1.6 (8) 40 ° <θ <52 ° (9) 39 ° <Ψ <58 ° (10) By making N _d1 and N _d2 smaller than the upper limit of 1.6 of the conditional expressions (7) and (8), it is preferable that a cheaper glass material can be used. At that time, θ is 52 ° (conditional expression (9)
It is possible to satisfy the conditions for total reflection on the optical surfaces 1C and 2B at the same time, by making Ψ smaller than (upper limit of) and Ψ larger than 39 ° (lower limit of conditional expression (10)).

If the refractive indexes of N _d1 and N _d2 are too small, it becomes difficult to secure the optical path length for bending the optical path. Therefore, the lower limit values are set in the conditional expressions (7) and (8). It is preferable that 25 <N _d1 <1.6 (7-1) and 1.25 <N _d2 <1.6 (8-1).

Further, more preferable results can be obtained when the optical surfaces 1B and 1D are mirror-coated and the optical surface 2C is used as a roof reflecting portion. By applying a mirror coat to the optical surfaces 1B and 1D, it is possible to reflect light rays that do not satisfy the conditions for total reflection on the optical surfaces 1B and 1D, and guide an even image to the periphery of the visual field to the eyepiece lens system. Optical surface 2
By using C as the roof reflection part, the roof reflection part can be effectively arranged without affecting the size of the camera of the finder optical system in the thickness direction and the space in front of the prism. .

Further, in the first real image type finder optical system according to the present invention, the optical surface 1B is mirror-coated so that it is perpendicular to the optical axis of the light beam emitted from the optical surface 2A between the optical surfaces 2A and 2B. The optical surface 2A 'is arranged and the optical surface 2A
And 2A 'to form a field lens, the optical surface 2B can be composed of one mirror, and the optical surface 2C can be composed of a roof mirror, and the second image inverting optical system can be hollow, and the prism Is unnecessary, the configuration can be made at a lower cost, and the optical path length can be shortened, so that the configuration can be made smaller.

Further, in the real image type finder optical system according to the present invention, if the light rays traveling from the objective lens system to the intermediate image forming surface are constituted so as to satisfy the following conditions, the degree of freedom of angle setting on each total reflection surface is set. Becomes larger and more preferable results are obtained.

0 ° ≦ | χ | <7 ° (15) where χ is incident on the image inversion optical system from the objective lens group in a plane including the objective lens group optical axis and the eyepiece lens group optical axis. The angle between the principal ray of the outermost peripheral light flux and the optical axis.

In addition,     0 ° ≦ | χ | <3 ° (16) Then, a better result can be obtained.

The third real image type finder optical system according to the present invention is a real image type finder optical system having an objective lens group having a positive refractive power, an image inverting optical system, and an eyepiece lens group having a positive refractive power in order from the object side. In the system, the image inverting optical system is configured so that the optical axes do not intersect in the optical system,
It is characterized by satisfying the following conditions.

29 ° <α <75 °, (11) 0.1 <L ₂ / L ₁ <0.49 (12) where α is the optical axis passing through the intermediate image plane. The angle formed by the optical axis of the objective lens group, L _1, is the intersection of the surface of the objective lens group closest to the object side and the optical axis of the objective lens group, and The distance to the intersection of the reflecting surface and the optical axis is the distance projected on the optical axis of the objective lens group, and L ₂ is the intermediate point from the intersection of the final reflecting surface of the image inverting optical system and the optical axis. The distance from the image plane to the intersection of the first reflecting surface of the image inverting optical system and the optical axis is the distance projected on the optical axis of the objective lens group.

By arranging the optical system so that the optical axes do not intersect with each other, it is possible to realize a miniaturized layout in which the effective ranges of the reflection / transmission surfaces of the optical system are partially overlapped.

If the lower limit of 29 ° to the conditional expression (11) is exceeded, it becomes difficult to achieve a structure satisfying the total reflection condition on the reflecting surface. If it becomes larger than the upper limit of 75 °,
In the image inverting optical system, the size of the portion arranged closer to the object side than the intermediate image plane becomes large, which is not suitable for downsizing and cost reduction.

Conditional expression (12) defines the ratio of the image inverting optical system to the size of the finder optical system in the camera thickness direction. The smaller this value is, the smaller the image inversion optical system becomes, but in reality, the luminous flux width and the effective range of the intermediate image formation surface cannot be made as small as possible. On the other hand, in the range in which the value becomes smaller than 0.1, it means that the size of the objective lens group in the thickness direction of the camera is large, which is not suitable for the purpose of the present invention. Upper limit of 0.4
If it exceeds 9, the ratio of the image inversion optical system to the size of the camera in the viewfinder optical system in the thickness direction will increase, so the space on the front side (object side) of the image inversion optical system will decrease. When arranging camera components such as an AF unit and an AE unit in that space, it is inevitable to use a more expensive small unit in order to downsize and guarantee the accuracy, and conversely it is large to make it inexpensive. The size of the unit must be used, which increases the thickness of the camera, making it impossible to achieve both low cost and downsizing.

Further, the optical axis of the objective lens group and the optical axis of the eyepiece lens group are configured to be substantially parallel to each other, and more preferable results can be obtained by satisfying the following conditions.

0.35 <(L ₁ −L ₂ ) / L ₃ <1.2 (13) where L ₃ is from the intersection with the optical axis of the final reflecting surface of the image inverting optical system. , The distance to the optical axis of the objective lens group.

Conditional expression (13) represents the size in the thickness direction of the camera of the space on the front side (object side) of the image inverting optical system.
It is standardized by the distance between the optical axis of the objective lens group and the optical axis of the eyepiece lens group. If the lower limit of 0.35 is exceeded, the size of the space in the front side (object side) of the image inversion optical system in the thickness direction of the camera tends to be insufficient, and conversely, the upper limit of 1.2 is exceeded. The larger the camera, the more space it will take, and the larger the camera. In order to effectively use this space and further reduce the size and cost of the camera, it is desirable to satisfy the conditional expression (13).

Further, the image inverting optical system has at least three reflecting portions on the objective lens side from the intermediate image forming surface and at least two reflecting portions on the eyepiece side from the intermediate image forming surface. By configuring at least one of the reflection parts by the roof reflection part, it becomes possible to achieve more effective miniaturization and cost reduction.

Further, by using a glass material satisfying the following conditions at least on the eyepiece side of the intermediate image plane in the image inverting optical system, the chromatic aberration of magnification at the wide-angle end, which is conspicuous, can be corrected better. You will be able to.

33 <ν _d <34 (14) where ν _d is the Abbe number of the glass material represented by ν _d = (n _d −1) / (n _F −n _C ). Where n _d , n _F ,
n _C is the refractive index of the glass material at each wavelength of d line, F line, and C line.

Further, better results can be obtained by satisfying the following conditions integrally or individually.

0.25 <L ₂ / L ₁ <0.46 (17) 0.37 <(L ₁ −L ₂ ) / L ₃ <0.85 (18) Further, Alternatively, better results can be obtained by individually satisfying the following conditions.

0.25 <L ₂ / L ₁ <0.35 (19) 0.7 <(L ₁ −L ₂ ) / L ₃ <0.8 (20) Further, By satisfying the conditions, better results can be obtained.

45 ° <α <55 °, (21) Further, in the real image type finder optical system of the present invention,
In the case where the first specification is a configuration in which a liquid crystal display element which is a display means in the visual field is arranged near the intermediate image forming surface, and the second specification is a configuration in which the air gap is near the intermediate image forming surface, the intermediate image formation is performed. Corrects the diopter deviation between the first and second specifications by applying the position of the entrance surface of the image inverting optical system that is closer to the eyepiece side than the vicinity of the surface and shifted along the optical axis. You will be able to do so. Here, the amount by which the position of the entrance surface of the image inversion optical system on the eyepiece side from the vicinity of the intermediate image forming surface is shifted on the optical axis is from the air-equivalent length of the liquid crystal display element which is the in-field display means of the first specification It is the amount obtained by subtracting the thickness of the liquid crystal display element that is the display means within the field of view.
By that amount, the position of the entrance surface of the image inverting optical system on the eyepiece side from the vicinity of the intermediate image forming surface of the second specification is shifted to the objective lens side along the optical axis. If so, the optical path length of the image inverting optical system located closer to the eyepiece lens than the vicinity of the intermediate image formation surface will increase by that amount.Therefore, it is necessary to bring the position of the eyepiece lens group closer to the image inverting optical system along the optical axis. ,
The eyepiece lens groups must also be provided with a mechanism that allows the eyepiece groups to be displaced to positions corresponding to the first and second specifications, respectively. When an adjustment mechanism for moving the position of the eyepiece lens group along the optical axis is provided, the adjustment margin may be increased correspondingly. With such a configuration, the camera main body (finder frame configuration) can be shared between the first specification and the second specification, so that the cost can be reduced.

In the fourth real image type finder optical system according to the present invention, the first specification has a constitution in which the in-field display means is arranged near the intermediate image forming surface, and the second specification has the intermediate value. In a real-image finder optical system equipped with an image inverting optical system in which the vicinity of the image plane is an air space, the position of the entrance surface of the image inverting system closer to the eyepiece than the vicinity of the intermediate image plane is shifted along the optical axis. It is characterized in that the deviation of the diopter between the first specification and the second specification is corrected by applying each of them.

As a result, image inverting optical systems having specifications in which the position of the entrance surface of the image inverting optical system located closer to the eyepiece lens than the vicinity of the intermediate image formation surface is shifted are prepared, and the position of the eyepiece lens group is adjusted accordingly. Only by shifting along the axis, there is no change in the position other than the position of the entrance surface of the image inverting optical system, so the camera body (finder frame configuration) is shared between the first and second specifications. Therefore, the cost can be reduced.

[0060]

Embodiments of the real image type finder optical system of the present invention will be described below.

FIG. 1 shows a first embodiment of the present invention. Objective lens group 10 having positive refractive power in order from the object side
An image inverting optical system 20 and an eyepiece group 30 having a positive refractive power
The image inverting optical system 20 includes a first image inverting optical system 21 and a second image inverting optical system 22 in this order from the object side, and the intermediate image forming surface formed by the objective lens group 10 is The first image inverting optical system 21 is arranged near the entrance surface 2A of the two-image inverting optical system and enters the first image inverting optical system 21 from the entrance surface 1A so that the optical axes do not intersect in the optical system, and then the optical surfaces 1B, 1C, and 1D. Optical surface 1C that reflects in this order on each surface of the
The second image inverting optical system 22 is configured to emit from the
The light enters from the incident surface 2A so that the optical axes do not intersect in the optical system, and is reflected in this order on each of the optical surfaces 2B and 2C,
The optical surface 2B, which also serves as a reflective surface and a transmissive surface, is configured to emit light. The optical surfaces 1B and 1D are mirror-coated, the optical surface 2C is a roof reflecting portion, and all the refracting surfaces and reflecting surfaces are flat. It has a rotationally symmetric curvature surface including.

The angle θ between the optical axis of the light ray incident on the optical surface 1B and the optical surface 1B (as shown in FIG. 12, the angle θ is the optical axis of the light ray incident on the optical surface 1B and the incidence of the optical surface 1B). The angle formed by the normal line at the position is 43 °, and the angle Ψ (as shown in FIG. 12) formed between the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C and the optical surface 1C. The angle Ψ is the optical surface 1C
Is an angle formed by the optical axis of the light beam incident on the optical axis and the normal line at the incident position on the optical surface 1C. ) Is 50 °. Also, optical surface 1
The angle formed by the optical axis of the light beam reflected by C and incident on the optical surface 1D and the normal line of the optical surface 1D at the optical axis incident position is 25 °,
The angle formed by the optical axis of the light beam incident from the incident surface 2A and the normal line of the optical surface 2B at the optical axis incident position is 44 °, and the optical surface 2B
Optical axis of the light beam reflected by and incident on the optical surface 2C and the optical surface 2
The angle formed by C and the normal line at the optical axis incident position is 22 °.

The optical surface 1A of the first image inverting optical system 21
Is a concave surface, which is not essential in the present invention, and may be a flat surface or a convex surface depending on the objective lens group 10. Further, a parallel plate is arranged between the first image inverting optical system 21 and the intermediate image forming position on the assumption of a liquid crystal display plate used for display in the field of view or the like, but of course this may not be necessary. In the second image inversion optical system 22,
Power is applied so that the entrance surface 2A functions as a field lens. This is also not an essential configuration in the present invention, and there is no problem whether it is a flat surface or a concave surface, and it is possible to dispose only the field lens portion independently of the second image inverting optical system 22.

Numerical data of this embodiment will be described later, but since the optical surfaces 1B, 1C, 1D, 2B and 2C are flat surfaces,
The first image inverting optical system 21 includes an entrance surface 1A (r ₇ ) and a transmission surface 1
Only C (r ₈ ) has the second image inverting optical system 22 with the incident surface 2A.
Only (r ₉ ) and the transmitting surface 2B (r ₁₀ ) are shown, and only the interval between them is shown. Note that, in FIG. 1, the exit pupil (eye point) is indicated by reference sign EP.

In this embodiment, the objective lens group 10
Is a first group G1 composed of a biconcave negative lens, a second group G2 composed of a positive meniscus lens having a convex surface facing the object side, and a third group G3 composed of a biconvex positive lens. When doubling, the first group G1 is fixed, the second group G2 monotonously moves toward the object side, and the third group G3 moves toward the object side such that the distance between the third group G3 and the second group G2 is once widened and then narrowed. Moving.
The eyepiece lens group 30 is composed of one biconvex positive lens.

Incidentally, FIG. 12 shows the optical axis of the objective lens group 10 and the eyepiece lens group 30 of the real image type finder optical system of the present invention.
The cross section including the optical axis of the group is shown, and the definitions of the angles θ, Ψ, α and the distances L ₁ , L ₂ , L ₃ are shown. FIG. 13 is a development view of the optical path of the real image type finder optical system of the present invention, and the definition of the angle χ is shown.

In this embodiment, L ₁ , L ₂ , L ₃ , L ₂ /
The values of L ₁ , (L ₁ −L ₂ ) / L ₃ , α, and χ are as follows.

L ₁ = 21.51 L ₂ = 7.90 L ₃ = 22.21, L ₂ / L ₁ = 0.37 (L ₁ -L ₂ ) / L ₃ = 0.61 α = 44 ° χ = 5.39 ° FIG. 2 shows the present invention. 9 shows Example 2. The objective lens group 10 having a positive refracting power, the image inverting optical system 20, and the eyepiece lens group 30 having a positive refracting power are provided in order from the object side. The image inverting optical system 20 has the first image in order from the object side. Inversion optical system 2
1 and the second image inverting optical system 22, and the objective lens group 10
The intermediate image forming surface formed by is disposed near the incident surface 2A of the second image inverting optical system, and the first image inverting optical system 21 is incident from the incident surface 1A so that the optical axes do not intersect in the optical system. Then, the second image inverting optical system 22 is configured to be reflected from the optical surfaces 1B, 1C, and 1D in this order and emitted from the optical surface 1C that also serves as a reflecting surface and a transmitting surface. The optical surface is configured such that the light enters from the incident surface 2A so that the optical axes do not intersect, is reflected in this order on each of the optical surfaces 2B and 2C, and exits from the optical surface 2B that also serves as a reflective surface and a transmissive surface. Mirror coating is applied to 1B and 1D, the optical surface 2C is a roof reflection portion, and all refraction surfaces and reflection surfaces are surfaces having a rotationally symmetric curvature including a flat surface.

The angle θ between the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B (as shown in FIG. 12, the angle θ is the optical axis of the light beam incident on the optical surface 1B and the incidence of the optical surface 1B). The angle formed by the normal line at the position is 45 °, and the angle ψ between the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C and the optical surface 1C (as shown in FIG. 12, The angle Ψ is the optical surface 1C
Is an angle formed by the optical axis of the light beam incident on the optical axis and the normal line at the incident position on the optical surface 1C. ) Is 45 °. Also, optical surface 1
The angle formed by the optical axis of the light beam reflected by C and incident on the optical surface 1D and the normal line of the optical surface 1D at the optical axis incident position is 22.5.
The angle between the optical axis of the light ray incident from the incident surface 2A and the normal of the optical surface 2B at the optical axis incident position is 45 °, and the optical axis of the light ray reflected by the optical surface 2B and incident on the optical surface 2C. The angle formed by the normal line of the optical surface 2C at the incident position of the optical axis is 22.
It is 5 °.

In this embodiment, the objective lens group 1
0, the eyepiece lens group 30 is substantially the same as that of the first embodiment, and the numerical data of this embodiment is substantially the same as that of the first embodiment, and therefore will be omitted.

In this embodiment, L ₁ , L ₂ , L ₃ , L ₂ /
The values of L ₁ , (L ₁ −L ₂ ) / L ₃ , α, and χ are as follows.

L ₁ = 21.85 L ₂ = 7.43 L ₃ = 21.87 L ₂ / L ₁ = 0.34 (L ₁ -L ₂ ) / L ₃ = 0.66 α = 45 ° χ = 5.39 ° FIG. 3 shows the embodiment of the present invention. 9 shows Example 3. The objective lens group 10 having a positive refracting power, the image inverting optical system 20, and the eyepiece lens group 30 having a positive refracting power are provided in order from the object side. The image inverting optical system 20 has the first image in order from the object side. Inversion optical system 2
1 and the second image inverting optical system 22, and the objective lens group 10
The intermediate image forming surface formed by is disposed near the incident surface 2A of the second image inverting optical system, and the first image inverting optical system 21 is incident from the incident surface 1A so that the optical axes do not intersect in the optical system. Then, the second image inverting optical system 22 is configured to be reflected from the optical surfaces 1B, 1C, and 1D in this order and emitted from the optical surface 1C that also serves as a reflecting surface and a transmitting surface. The optical surface is configured such that the light enters from the incident surface 2A so that the optical axes do not intersect, is reflected in this order on each of the optical surfaces 2B and 2C, and exits from the optical surface 2B that also serves as a reflective surface and a transmissive surface. Mirror coating is applied to 1B and 1D, the optical surface 2C is a roof reflection portion, and all refraction surfaces and reflection surfaces are surfaces having a rotationally symmetric curvature including a flat surface.

The angle θ between the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B (as shown in FIG. 12, the angle θ is the optical axis of the light beam incident on the optical surface 1B and the incidence of the optical surface 1B). The angle between the optical axis of the ray reflected by the optical surface 1B and incident on the optical surface 1C and the optical surface 1C is Ψ (as shown in FIG. 12). The angle Ψ is the optical surface 1C
Is an angle formed by the optical axis of the light beam incident on the optical axis and the normal line at the incident position on the optical surface 1C. ) Is 60 °. Also, optical surface 1
The angle formed by the optical axis of the light beam reflected by C and incident on the optical surface 1D and the normal line of the optical surface 1D at the optical axis incident position is 30 °,
The angle formed by the optical axis of the light beam incident from the incident surface 2A and the normal line of the optical surface 2B at the optical axis incident position is 50 °, and the optical surface 2B
Optical axis of the light beam reflected by and incident on the optical surface 2C and the optical surface 2
The angle between C and the normal at the optical axis incident position is 25 °.

In this embodiment, the objective lens group 1
0, the eyepiece lens group 30 is substantially the same as that of the first embodiment, and the numerical data of this embodiment is substantially the same as that of the first embodiment, and therefore will be omitted.

In this embodiment, L ₁ , L ₂ , L ₃ and L ₂ /
The values of L ₁ , (L ₁ −L ₂ ) / L ₃ , α, and χ are as follows.

L ₁ = 19.83 L ₂ = 6.76 L ₃ = 23.59 L ₂ / L ₁ = 0.34 (L ₁ −L ₂ ) / L ₃ = 0.55 α = 50 ° χ = 5.39 ° FIG. 4 shows the embodiment of the present invention. 9 shows Example 4. The objective lens group 10 having a positive refracting power, the image inverting optical system 20, and the eyepiece lens group 30 having a positive refracting power are provided in order from the object side. The image inverting optical system 20 has the first image in order from the object side. Inversion optical system 2
1 and the second image inverting optical system 22, and the objective lens group 10
The intermediate image forming surface formed by is disposed near the incident surface 2A of the second image inverting optical system, and the first image inverting optical system 21 is incident from the incident surface 1A so that the optical axes do not intersect in the optical system. Then, the second image inverting optical system 22 is configured to be reflected from the optical surfaces 1B, 1C, and 1D in this order and emitted from the optical surface 1C that also serves as a reflecting surface and a transmitting surface. The optical surface is configured such that the light enters from the incident surface 2A so that the optical axes do not intersect, is reflected in this order on each of the optical surfaces 2B and 2C, and exits from the optical surface 2B that also serves as a reflective surface and a transmissive surface. Mirror coating is applied to 1D and 2C, the optical surface 1B is a roof reflection portion, and all refraction surfaces and reflection surfaces are surfaces having rotationally symmetrical curvatures including flat surfaces.

The angle θ formed between the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B (as shown in FIG. 12, the angle θ is the optical axis of the light beam incident on the optical surface 1B and the incidence of the optical surface 1B). The angle formed by the normal line at the position is 30 °, and the angle Ψ formed by the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C and the optical surface 1C (as shown in FIG. 12). The angle Ψ is the optical surface 1C
Is an angle formed by the optical axis of the light beam incident on the optical axis and the normal line at the incident position on the optical surface 1C. ) Is 50 °. Also, optical surface 1
The angle formed by the optical axis of the light beam reflected by C and incident on the optical surface 1D and the normal line of the optical surface 1D at the optical axis incident position is 25 °,
The angle formed by the optical axis of the light ray incident from the incident surface 2A and the normal line of the optical surface 2B at the optical axis incident position is 70 °, and the optical surface 2B
Optical axis of the light beam reflected by and incident on the optical surface 2C and the optical surface 2
The angle formed by C and the normal line at the optical axis incident position is 35 °.

In this embodiment, the objective lens group 1
0, the eyepiece lens group 30 is substantially the same as that of the first embodiment, and the numerical data of this embodiment is substantially the same as that of the first embodiment, and therefore will be omitted.

In this embodiment, L ₁ , L ₂ , L ₃ , L ₂ /
The values of L ₁ , (L ₁ −L ₂ ) / L ₃ , α, and χ are as follows.

L ₁ = 16.35 L ₂ = 5.12 L ₃ = 29.86 L ₂ / L ₁ = 0.31 (L ₁ -L ₂ ) / L ₃ = 0.38 α = 70 ° χ = 5.39 ° FIG. 5 shows the embodiment of the present invention. 9 shows Example 5. The objective lens group 10 having a positive refracting power, the image inverting optical system 20, and the eyepiece lens group 30 having a positive refracting power are provided in order from the object side. The image inverting optical system 20 has the first image in order from the object side. Inversion optical system 2
1 and the second image inverting optical system 22, and the objective lens group 10
The intermediate image forming surface formed by is disposed near the incident surface 2A of the second image inverting optical system, and the first image inverting optical system 21 is incident from the incident surface 1A so that the optical axes do not intersect in the optical system. Then, the second image inverting optical system 22 is configured to be reflected from the optical surfaces 1B, 1C, and 1D in this order and emitted from the optical surface 1C that also serves as a reflecting surface and a transmitting surface. The optical surface is configured such that the light enters from the incident surface 2A so that the optical axes do not intersect, is reflected in this order on each of the optical surfaces 2B and 2C, and exits from the optical surface 2B that also serves as a reflective surface and a transmissive surface. Mirror coating is applied to 1B and 1D, the optical surface 2C is a roof reflection portion, and all refraction surfaces and reflection surfaces are surfaces having a rotationally symmetric curvature including a flat surface.

The angle θ formed by the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B (as shown in FIG. 12, the angle θ is the optical axis of the light beam incident on the optical surface 1B and the incidence of the optical surface 1B). The angle formed by the normal line at the position is 30 °, and the angle Ψ formed by the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C and the optical surface 1C (as shown in FIG. 12). The angle Ψ is the optical surface 1C
Is an angle formed by the optical axis of the light beam incident on the optical axis and the normal line at the incident position on the optical surface 1C. ) Is 68 °. Also, optical surface 1
The angle formed by the optical axis of the light beam reflected by C and incident on the optical surface 1D and the normal line of the optical surface 1D at the optical axis incident position is 34 °,
The angle formed by the optical axis of the light beam incident from the incident surface 2A and the normal line of the optical surface 2B at the optical axis incident position is 52 °, and the optical surface 2B
Optical axis of the light beam reflected by and incident on the optical surface 2C and the optical surface 2
The angle formed by C and the normal to the optical axis incident position is 26 °.

In this embodiment, the objective lens group 1
0, the eyepiece lens group 30 is substantially the same as that of the first embodiment, and the numerical data of this embodiment is substantially the same as that of the first embodiment, and therefore will be omitted.

In this embodiment, L ₁ , L ₂ , L ₃ , L ₂ /
The values of L ₁ , (L ₁ −L ₂ ) / L ₃ , α, and χ are as follows.

L ₁ = 17.57 L ₂ = 7.05 L ₃ = 25.21 L ₂ / L ₁ = 0.40 (L ₁ −L ₂ ) / L ₃ = 0.42 α = 52 ° χ = 5.39 ° FIG. 6 shows the embodiment of the present invention. 9 shows Example 6. The objective lens group 10 having a positive refracting power, the image inverting optical system 20, and the eyepiece lens group 30 having a positive refracting power are provided in order from the object side. The image inverting optical system 20 has the first image in order from the object side. Inversion optical system 2
1 and the second image inverting optical system 22, and the objective lens group 10
The intermediate image forming surface formed by is disposed near the incident surface 2A of the second image inverting optical system, and the first image inverting optical system 21 is incident from the incident surface 1A so that the optical axes do not intersect in the optical system. Then, the second image inverting optical system 22 is configured to be reflected from the optical surfaces 1B, 1C, and 1D in this order and emitted from the optical surface 1C that also serves as a reflecting surface and a transmitting surface. The optical surface is configured such that the light enters from the incident surface 2A so that the optical axes do not intersect, is reflected in this order on each of the optical surfaces 2B and 2C, and exits from the optical surface 2B that also serves as a reflective surface and a transmissive surface. Mirror coating is applied to 1B and 1D, the optical surface 2C is a roof reflection portion, and all refraction surfaces and reflection surfaces are surfaces having a rotationally symmetric curvature including a flat surface.

The angle θ formed between the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B (as shown in FIG. 12, the angle θ is the optical axis of the light beam incident on the optical surface 1B and the incidence of the optical surface 1B). The angle formed by the normal line at the position is 43 °, and the angle Ψ (as shown in FIG. 12) formed between the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C and the optical surface 1C. The angle Ψ is the optical surface 1C
Is an angle formed by the optical axis of the light beam incident on the optical axis and the normal line at the incident position on the optical surface 1C. ) Is 50 °. Also, optical surface 1
The angle formed by the optical axis of the light beam reflected by C and incident on the optical surface 1D and the normal line of the optical surface 1D at the optical axis incident position is 25 °,
The angle formed by the optical axis of the light beam incident from the incident surface 2A and the normal line of the optical surface 2B at the optical axis incident position is 44 °, and the optical surface 2B
Optical axis of the light beam reflected by and incident on the optical surface 2C and the optical surface 2
The angle formed by C and the normal line at the optical axis incident position is 22 °.

Numerical data of this embodiment will be described later. Since the optical surfaces 1A, 1B, 1C, 1D, 2B and 2C are flat surfaces, the first image reversing optical system 21 transmits the light through the incident surface 1A (r ₉ ). Only the surface 1C (r ₁₀ ) is shown, only the entrance surface 2A (r ₁₁ ) and the transmission surface 2B (r ₁₂ ) of the second image inversion optical system 22 are shown, and only the interval therebetween is shown.

In this embodiment, the objective lens group 10
Is a first group G1 including a biconvex positive lens, a second group G2 including a biconcave negative lens, a third group G3 including a concave plano negative lens,
It consists of a fourth lens group G4 consisting of a biconvex positive lens, and when zooming from the wide-angle end to the telephoto end, the first lens group G1 and the fourth lens group G4 are fixed, and the second lens group G2 moves monotonically toward the image side. , The third lens group G3 moves toward the image plane side so that the distance between the third lens group G3 and the second lens group G2 is once narrowed and then widened. The eyepiece lens group 30 is composed of one biconvex positive lens.

In this embodiment, L ₁ , L ₂ , L ₃ , L ₂ /
The values of L ₁ , (L ₁ −L ₂ ) / L ₃ , α, and χ are as follows.

L ₁ = 27.91 L ₂ = 8.78 L ₃ = 27.23 L ₂ / L ₁ = 0.31 (L ₁ −L ₂ ) / L ₃ = 0.70 α = 44 ° χ = 2.09 ° FIG. 7 shows the embodiment of the present invention. 9 shows Example 7. The objective lens group 10 having a positive refracting power, the image inverting optical system 20, and the eyepiece lens group 30 having a positive refracting power are provided in order from the object side. The image inverting optical system 20 has the first image in order from the object side. Inversion optical system 2
1 and the second image inverting optical system 22, and the objective lens group 10
The intermediate image forming surface formed by is disposed near the incident surface 2A of the second image inverting optical system, and the first image inverting optical system 21 is incident from the incident surface 1A so that the optical axes do not intersect in the optical system. Then, the second image inverting optical system 22 is configured to be reflected from the optical surfaces 1B, 1C, and 1D in this order and emitted from the optical surface 1C that also serves as a reflecting surface and a transmitting surface. The optical surface is configured such that the light enters from the incident surface 2A so that the optical axes do not intersect, is reflected in this order on each of the optical surfaces 2B and 2C, and exits from the optical surface 2B that also serves as a reflective surface and a transmissive surface. Mirror coating is applied to 1D, the optical surface 2C is a roof reflecting portion, and all refracting surfaces and reflecting surfaces are surfaces having rotationally symmetrical curvatures including flat surfaces.

The angle θ between the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B (as shown in FIG. 12, the angle θ is the optical axis of the light beam incident on the optical surface 1B and the incidence of the optical surface 1B). The angle formed by the normal line at the position is 55 °, and the angle ψ between the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C and the optical surface 1C (as shown in FIG. 12, The angle Ψ is the optical surface 1C
Is an angle formed by the optical axis of the light beam incident on the optical axis and the normal line at the incident position on the optical surface 1C. ) Is 36 °. Also, optical surface 1
The angle formed by the optical axis of the light beam reflected by C and incident on the optical surface 1D and the normal line of the optical surface 1D at the optical axis incident position is 18 °,
The angle formed by the optical axis of the light beam incident from the incident surface 2A and the normal line of the optical surface 2B at the optical axis incident position is 34 °, and the optical surface 2B
Optical axis of the light beam reflected by and incident on the optical surface 2C and the optical surface 2
The angle formed by C and the normal to the optical axis incident position is 17 °.

In this embodiment, the objective lens group 1
0, the eyepiece lens group 30 is substantially the same as that of the sixth embodiment, and the numerical data of this embodiment is also substantially the same as that of the sixth embodiment, and therefore will be omitted.

In this embodiment, L ₁ , L ₂ , L ₃ , L ₂ /
The values of L ₁ , (L ₁ −L ₂ ) / L ₃ , α, and χ are as follows.

L ₁ = 35.80 L ₂ = 11.15 L ₃ = 25.92 L ₂ / L ₁ = 0.31 (L ₁ −L ₂ ) / L ₃ = 0.95 α = 34 ° χ = 2.09 ° FIG. 8 shows the embodiment of the present invention. 9 shows Example 8. The objective lens group 10 having a positive refracting power, the image inverting optical system 20, and the eyepiece lens group 30 having a positive refracting power are provided in order from the object side. The image inverting optical system 20 has the first image in order from the object side. Inversion optical system 2
1 and the second image inverting optical system 22, and the objective lens group 10
The intermediate image forming surface formed by is disposed near the incident surface 2A of the second image inverting optical system, and the first image inverting optical system 21 is incident from the incident surface 1A so that the optical axes do not intersect in the optical system. Then, the second image inverting optical system 22 is configured to be reflected from the optical surfaces 1B, 1C, and 1D in this order and emitted from the optical surface 1C that also serves as a reflecting surface and a transmitting surface. Is configured so that the light enters from the incident surface 2A so that the optical axes do not intersect, is reflected in this order on each of the optical surfaces 2B and 2C, and exits from the optical surface 2D, and a mirror coat is applied to the optical surfaces 1B and 1D. The optical surface 2C is a roof reflecting portion, and all the refracting surfaces and reflecting surfaces are surfaces having rotationally symmetrical curvatures including flat surfaces.

The angle θ between the optical axis of the light ray incident on the optical surface 1B and the optical surface 1B (as shown in FIG. 12, the angle θ is the optical axis of the light ray incident on the optical surface 1B and the incidence of the optical surface 1B). The angle formed by the normal line at the position is 43 °, and the angle Ψ (as shown in FIG. 12) formed between the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C and the optical surface 1C. The angle Ψ is the optical surface 1C
Is an angle formed by the optical axis of the light beam incident on the optical axis and the normal line at the incident position on the optical surface 1C. ) Is 50 °. Also, optical surface 1
The angle formed by the optical axis of the light beam reflected by C and incident on the optical surface 1D and the normal line of the optical surface 1D at the optical axis incident position is 25 °,
The angle formed by the optical axis of the light beam incident from the incident surface 2A and the normal line of the optical surface 2B at the optical axis incident position is 44 °, and the optical surface 2B
Optical axis of the light beam reflected by and incident on the optical surface 2C and the optical surface 2
The angle formed by C and the normal line at the optical axis incident position is 22 °.

In this embodiment, the objective lens group 1
0, the eyepiece lens group 30 is substantially the same as that of the first embodiment, and the numerical data of this embodiment is substantially the same as that of the first embodiment, and therefore will be omitted.

In this embodiment, L ₁ , L ₂ , L ₃ , L ₂ /
The values of L ₁ , (L ₁ −L ₂ ) / L ₃ , α, and χ are as follows.

L ₁ = 17.89 L ₂ = 8.23 L ₃ = 23.05 L ₂ / L ₁ = 0.46 (L ₁ -L ₂ ) / L ₃ = 0.42 α = 44 ° χ = 5.39 ° FIG. 9 shows the embodiment of the present invention. 9 shows Example 9. The objective lens group 10 having a positive refracting power, the image inverting optical system 20, and the eyepiece lens group 30 having a positive refracting power are provided in order from the object side. The image inverting optical system 20 has the first image in order from the object side. Inversion optical system 2
1 and the second image inverting optical system 22, and the objective lens group 10
The intermediate image forming surface formed by is disposed near the incident surface 2A of the second image inverting optical system, and the first image inverting optical system 21 is incident from the incident surface 1A so that the optical axes do not intersect in the optical system. Then, the second image inverting optical system 22 is configured to be reflected from the optical surfaces 1B, 1C, and 1D in this order and emitted from the optical surface 1C that also serves as a reflecting surface and a transmitting surface. Is configured so that the light enters from the first incident surface 2A of the positive lens 23 so that the optical axes do not intersect with each other, and is reflected by the second surface 2A ′ of the positive lens 23 and the optical surfaces 2B and 2C in this order. Then
Optical surfaces 1B and 1D are mirror-coated, and optical surfaces 2B
Is a plane mirror, the optical surface 2C is a roof mirror, and all refracting surfaces and reflecting surfaces are surfaces having rotationally symmetrical curvatures including a flat surface.

The angle θ between the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B (as shown in FIG. 12, the angle θ is the optical axis of the light beam incident on the optical surface 1B and the incidence of the optical surface 1B). The angle formed by the normal line at the position is 43 °, and the angle Ψ (as shown in FIG. 12) formed between the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C and the optical surface 1C. The angle Ψ is the optical surface 1C
Is an angle formed by the optical axis of the light beam incident on the optical axis and the normal line at the incident position on the optical surface 1C. ) Is 50 °. Also, optical surface 1
The angle formed by the optical axis of the light beam reflected by C and incident on the optical surface 1D and the normal line of the optical surface 1D at the optical axis incident position is 25 °,
The angle formed by the optical axis of the light beam incident from the incident surface 2A and the normal line of the optical surface 2B at the optical axis incident position is 44 °, and the optical surface 2B
Optical axis of the light beam reflected by and incident on the optical surface 2C and the optical surface 2
The angle formed by C and the normal to the optical axis incident position is 17 °.

In this embodiment, the objective lens group 1
0, the eyepiece lens group 30 is substantially the same as that of the first embodiment, and the numerical data of this embodiment is substantially the same as that of the first embodiment, and therefore will be omitted.

In this embodiment, L ₁ , L ₂ , L ₃ , L ₂ /
The values of L ₁ , (L ₁ −L ₂ ) / L ₃ , α, and χ are as follows.

L ₁ = 17.87 L ₂ = 8.20 L ₃ = 23.05 L ₂ / L ₁ = 0.46 (L ₁ −L ₂ ) / L ₃ = 0.42 α = 44 ° χ = 5.39 ° FIG. 10 shows the embodiment of the present invention. 11 shows Example 10. In order from the object side, it has an objective lens group 10 having a positive refractive power, an image inverting optical system 20, and an eyepiece lens group 30 having a positive refractive power,
The image inverting optical system 20 includes a first image inverting optical system 21 and a second image inverting optical system 22 in order from the object side, and an intermediate image forming surface formed by the objective lens group 10 is a second image inverting optical system. Of the first image inverting optical system 21
The incident surface 1A so that the optical axes do not intersect in the optical system.
From the optical surface 1C that also serves as a reflective surface and a transmissive surface, and the second image reversing optical system 22 is configured to emit light from the optical surface 1B, 1C, and 1D. It is configured such that the light enters from the incident surface 2A so that the optical axes do not intersect in the system, is reflected in this order on each of the optical surfaces 2B and 2C, and is emitted from the optical surface 2B that also serves as a reflecting surface and a transmitting surface. The optical surfaces 1B and 1D are mirror-coated, the optical surface 2C is a roof reflection portion, and all the refraction surfaces and reflection surfaces are surfaces having rotationally symmetrical curvatures including flat surfaces.

The angle θ formed between the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B (as shown in FIG. 12, the angle θ is the optical axis of the light beam incident on the optical surface 1B and the incidence of the optical surface 1B). The angle formed by the normal line at the position is 43 °, and the angle Ψ (as shown in FIG. 12) formed between the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C and the optical surface 1C. The angle Ψ is the optical surface 1C
Is an angle formed by the optical axis of the light beam incident on the optical axis and the normal line at the incident position on the optical surface 1C. ) Is 50 °. Also, optical surface 1
The angle formed by the optical axis of the light beam reflected by C and incident on the optical surface 1D and the normal line of the optical surface 1D at the optical axis incident position is 25 °,
The angle formed by the optical axis of the light beam incident from the incident surface 2A and the normal line of the optical surface 2B at the optical axis incident position is 44 °, and the optical surface 2B
Optical axis of the light beam reflected by and incident on the optical surface 2C and the optical surface 2
The angle formed by C and the normal line at the optical axis incident position is 22 °. The Abbe number ν _{d of the} glass material used in the image inverting optical system (second image inverting optical system 22) on the eyepiece side of the intermediate image plane is 33.5. This effectively corrects chromatic aberration of magnification in a wide-angle range that is easily noticeable.

In this embodiment, the objective lens group 1
0, the eyepiece lens group 30 is substantially the same as that of the sixth embodiment, and the numerical data of this embodiment is also substantially the same as that of the sixth embodiment, and therefore will be omitted.

In this embodiment, L ₁ , L ₂ , L ₃ , L ₂ /
The values of L ₁ , (L ₁ −L ₂ ) / L ₃ , α, and χ are as follows.

L ₁ = 27.78 L ₂ = 8.80 L ₃ = 27.48 L ₂ / L ₁ = 0.32 (L ₁ -L ₂ ) / L ₃ = 0.69 α = 44 ° χ = 2.09 ° FIG. 11 shows the embodiment of the present invention. 12 shows Example 11. In order from the object side, it has an objective lens group 10 having a positive refractive power, an image inverting optical system 20, and an eyepiece lens group 30 having a positive refractive power,
The image inverting optical system 20 includes a first image inverting optical system 21 and a second image inverting optical system 22 in order from the object side, and an intermediate image forming surface formed by the objective lens group 10 is a second image inverting optical system. Of the first image inverting optical system 21
The incident surface 1A so that the optical axes do not intersect in the optical system.
From the optical surface 1C that also serves as a reflective surface and a transmissive surface, and the second image reversing optical system 22 is configured to emit light from the optical surface 1B, 1C, and 1D. It is configured such that the light enters from the incident surface 2A so that the optical axes do not intersect in the system, is reflected in this order on each of the optical surfaces 2B and 2C, and is emitted from the optical surface 2B that also serves as a reflecting surface and a transmitting surface. The optical surfaces 1B and 1D are mirror-coated, the optical surface 2C is a roof reflection portion, and all the refraction surfaces and reflection surfaces are surfaces having rotationally symmetrical curvatures including flat surfaces.

The angle θ between the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B (as shown in FIG. 12, the angle θ is the optical axis of the light beam incident on the optical surface 1B and the incidence of the optical surface 1B). The angle formed by the normal line at the position is 41 °, and the angle ψ between the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C and the optical surface 1C (as shown in FIG. 12 is The angle Ψ is the optical surface 1C
Is an angle formed by the optical axis of the light beam incident on the optical axis and the normal line at the incident position on the optical surface 1C. ) Is 49 °. Also, optical surface 1
The angle formed by the optical axis of the light beam reflected by C and incident on the optical surface 1D and the normal line of the optical surface 1D at the optical axis incident position is 24.5.
The angle between the optical axis of the light ray incident from the incident surface 2A and the normal of the optical surface 2B at the optical axis incident position is 49 °, and the optical axis of the light ray reflected by the optical surface 2B and incident on the optical surface 2C. The angle formed by the normal line at the optical axis incident position of the optical surface 2C is 24.
It is 5 °.

Numerical data of this embodiment will be described later, but since the optical surfaces 1A, 1B, 1C, 1D, 2B and 2C are planes, the first image inverting optical system 21 transmits the incident surface 1A (r ₉ ) and the transmission surface. Only the surface 1C (r ₁₀ ) is shown, only the entrance surface 2A (r ₁₁ ) and the transmission surface 2B (r ₁₂ ) of the second image inversion optical system 22 are shown, and only the interval therebetween is shown.

In this embodiment, the objective lens group 10
Is a first group G1 including a negative meniscus lens having a convex surface facing the object side, a second group G2 including a biconvex positive lens, a third group G3 including a biconcave negative lens, and a fourth group including a biconvex positive lens.
It consists of group G4, and when zooming from the wide-angle end to the telephoto end,
The group G1 and the fourth group G4 are fixed, the second group G2 monotonically moves to the object side, and the third group G3 moves to the image plane side while widening the distance between the second group G2 and the second group G2. The eyepiece lens group 30 is composed of one biconvex positive lens.

In this embodiment, L ₁ , L ₂ , L ₃ , L ₂ /
The values of L ₁ , (L ₁ −L ₂ ) / L ₃ , α, and χ are as follows.

L ₁ = 26.33 L ₂ = 7.43 L ₃ = 25.00 L ₂ / L ₁ = 0.28 (L ₁ -L ₂ ) / L ₃ = 0.76 α = 49 ° χ = 2.76 ° Numerical data of Nos. 6 and 11 are shown, but symbols are other than the above, ω is a half angle of view in a plane (drawing) including the optical axis of the objective lens group 10 and the optical axis of the eyepiece lens group 30,
WE is wide-angle end, ST is intermediate state, TE is telephoto end, r ₁ ,
r ₂ ... curvature radius of each lens surface, d _1, d ₂ ... the spacing between the lens surfaces, n _d1, n _d2 ... d-line refractive index of each lens, ν _d1, ν _d2 ... Each lens Is the Abbe number. In addition,
In the aspherical shape, x is an optical axis with the traveling direction of light being positive,
When y is taken in the direction orthogonal to the optical axis, it is represented by the following formula.

X = (y ² / r) / [1+ {1- (K +
1) (y / r) ² } ^1/2 ] + A ₄ y ⁴ + A ₆ y ⁶ + A ₈ y ⁸ +
A ₁₀ y ¹⁰ However, r is a paraxial radius of curvature, K is a conic coefficient, A ₄ , A ₆ ,
A ₈ and A ₁₀ are aspherical coefficients of the 4th, 6th, 8th and 10th orders, respectively.

Example 1 r ₁ = -15.3909 d ₁ = 0.8000 n _d1 = 1.58423 ν _d1 = 30.49 r ₂ = 10.3442 (aspherical surface) d ₂ = (variable) r ₃ = 7.1858 (aspherical surface) d ₃ = _{1.4922 n d2 = 1.49241 ν d2 =} 57.66 r 4 = 117.5229 d 4 = ( _{variable) r 5 = 13.0856 d 5 =} 1.6252 n d3 = 1.49241 ν d3 = 57.66 r 6 = -13.8840 ( aspherical) d ₆ = (variable) r ₇ = -40.5163 (aspherical surface) d ₇ = 15.8700 n _d4 = 1.52542 ν _d4 = 55.78 r ₈ = ∞ d ₈ = 1.7499 r ₉ = 10.1952 d ₉ = 25.9000 n _d5 = 1.52542 ν _d5 = 55.78 r ₁₀ = ∞ d ₁₀ = 2.0530 r ₁₁ = 13.6162 (aspherical surface) d ₁₁ = 2.2210 n _d6 = 1.49241 ν _d6 = 57.66 r ₁₂ = -32.4049 d ₁₂ = 17.2700 r ₁₃ = ∞ (EP) Aspherical surface second surface K = -1.5575 A ₄ = -2.5148 × 10 ^-4 A ₆ = 5.4561 × 10 ^-5 A ₈ = 7.4446 × 10 ^-7 A ₁₀ = -5.2554 × 10 ^-7 3rd surface K = -0.6230 A ₄ = -3.2525 × 10 ^-4 A ^{_{6 = 4.5672 × 10 -5 A 8}} = -4.8442 × 10 -6 A 10 = 2.2430 × 10 -7 sixth surface _{K = -3.2507 A 4 = 2.8231 ×} 10 -4 A 6 = 4.5717 × 10 - ⁷ A ₈ = -8.8012 × 10 ^-7 A ₁₀ = 1.3402 × 10 ^-7 7th surface K = 30.9444C A ₄ = -4.9712 × 10 ^-4 A ₆ = 6.3227 × 10 ^-5 A ₈ = -9.9634 × 10 ^-6 A ₁₀ = 5.4708 × 10 ^-7 11th surface K = 3.1823 A ₄ = -2.8796 × 10 ^-4 A ₆ = -1.1635 × 10 ^-6 A ₈ = -2.3723 × 10 ^-8 A ₁₀ = -1.8182 × 10 ^-9 Zoom data (∞) WE ST TE ω (°) 20.772 12.560 7.541 d ₂ 8.4811 3.5686 0.6956 d ₄ 1.4346 3.1090 0.6911 d ₆ 0.9670 4.2051 9.4960.

Example 6 r ₁ = 15.9340 d ₁ = 3.0618 n _d1 = 1.52542 ν _d1 = 57.86 r ₂ = -16.3329 (aspherical surface) d ₂ = (variable) r ₃ = -14.0378 d ₃ = 0.8000 n _d2 = 1.58423 ν _d2 = 30.49 r ₄ = 9.7041 (aspherical surface) d ₄ = (variable) r ₅ = -5.8125 (aspherical surface) d ₅ = 0.7500 n _d3 = 1.49235 ν _d3 = 57.86 r ₆ = ∞ d ₆ = (variable) ) R ₇ = 9.5484 (aspherical surface) d ₇ = 3.1000 n _d4 = 1.52542 ν _d4 = 57.86 r ₈ = -8.5754 (aspherical surface) d ₈ = 0.3000 r ₉ = ∞ d ₉ = 22.0350 n _d5 = 1.52542 ν _d5 = 55.78 r ₁₀ = ∞ d ₁₀ = 1.6067 r ₁₁ = 19.9496 d ₁₁ = 29.0800 n _d6 = 1.52542 ν _d6 = 55.78 r ₁₂ = ∞ d ₁₂ = 1.3770 r ₁₃ = 13.8487 (aspheric surface) d ₁₃ = 2.0963 n _d7 = 1.49235 ν _d7 = 57.86 r ₁₄ = -40.8035 d ₁₄ = 16.5000 r ₁₅ = ∞ (EP) Aspheric coefficient second surface K = -5.2662 A ₄ = 1.0175 × 10 ^-4 A ₆ = 7.1492 × 10 ^-7 A ₈ = -7.5559 × 10 ^-8 A ₁₀ = 1.0476 × 10 ^-9 4th surface K = -1.0524 A ₄ = -2.0896 × 10 ^-3 A ₆ = 3.7124 × 10 ^-5 A ₈ = 2.0896 × 10 ^-6 A ₁₀ = -3.7354 × 10 ^-7 Fifth surface K = 0.4406 A ₄ = -4.2942 × 10 ^-4 A ₆ = -6.2641 × 10 ^-5 A ₈ = 3.1474 × 10 ^-6 A ₁₀ = 7.0067 × 10 ^-8 7th surface K = -0.2416 A ₄ = -2.3410 × 10 ^-5 A ₆ = -2.2063 × 10 ^-5 A ₈ = 1.2177 × 10 ^-6 A ₁₀ = -3.3333 × 10 ^-9 8th surface K _{= -1.0463 A 4 = 5.1581 × 10} -4 A 6 = -2.2170 × 10 -5 A 8 = 1.0618 × 10 -6 A 10 = 1.9887 × 10 -9 13th surface _{K = 2.2668 A 4 = -2.4333 ×} 10 - ⁴ A ₆ = 4.3186 × 10 ^-6 A ₈ = -2.7372 × 10 ^-7 A ₁₀ = 3.6835 × 10 ^-9 Zoom data (∞) WE ST TE ω (°) 20.769 10.450 5.077 d ₂ 0.7526 4.5418 6.6194 d ₄ 2.9450 1.6994 4.8146 d ₆ 8.7726 6.2290 1.0362.

Example 11 r ₁ = 34.9116 d ₁ = 0.9000 n _d1 = 1.57268 ν _d1 = 33.51 r ₂ = 4.7842 (aspherical surface) d ₂ = (variable) r ₃ = 6.1775 (aspherical surface) d ₃ = 2.9500 n _d2 = 1.52542 ν _d2 = 55.78 r ₄ = -9.4059 d ₄ = (variable) r ₅ = -4.2027 (aspherical surface) d ₅ = 0.8000 n _d3 = 1.58425 ν _d3 = 30.35 r ₆ = 4.2728 (aspherical surface) d ₆ = (variable) r ₇ = 5.5304 _{(aspherical) d 7 = 3.3000 n d4 =} 1.52542 ν d4 = 55.78 r 8 = -5.6201 ( _{aspherical) d 8 = 0.3500 r 9 =} ∞ d 9 = 19.6000 n d5 = 1.52542 ν _d5 = 55.78 r ₁₀ = ∞ d ₁₀ = 2.0043 r ₁₁ = 17.7865 d ₁₁ = 25.0000 n _d6 = 1.52542 ν _d6 = 55.78 r ₁₂ = ∞ d ₁₂ = 2.3958 r ₁₃ = 19.2220 (aspherical surface) d ₁₃ = 2.0000 n _d7 = 1.52542 ν _d7 = 55.78 r ₁₄ = -21.4065 d ₁₄ = 17.1000 r ₁₅ = ∞ (EP) Aspheric coefficient second surface K = 0.4185 A ₄ = -1.3106 × 10 ^-3 A ₆ = -1.0611 × 10 ^-4 A ₈ = 9.0141 × 10 ^-6 A ₁₀ = -6.5438 × 10 ^-7 Third surface K = -0.1995 A ₄ = -9.0860 × 10 ^-4 A ₆ = -4.3 299 x 10 ^-6 A ₈ = 4.9862 x 10 ^-8 A ₁₀ = 2.6529 x 10 ^-9 5th surface K = 1.2820 A ₄ = 7.0406 x 10 ^-3 A ₆ = -5.2546 x 10 ^-4 A ₈ = 6.5880 x 10 ^-6 A ₁₀ = 1.3665 × ₁₀ ^-5 sixth surface _{K = -8.1746 A 4 = 8.8208 ×} 10 -3 A 6 = -1.6893 × 10 -3 A 8 = 1.5906 × 10 -4 A 10 = -6.0044 × 10 - ⁶ 7th surface K = -2.5370 A ₄ = -1.4673 × 10 ^-3 A ₆ = 1.5461 × 10 ^-4 A ₈ = -6.6743 × 10 ^-6 A ₁₀ = 3.5300 × 10 ^-7 8th surface K = 0.0975 A ₄ = 3.1560 × 10 ^-4 A ₆ = 1.3210 × 10 ^-4 A ₈ = -1.1849 × 10 ^-5 A ₁₀ = 7.8785 × 10 ^-7 13th surface K = -1.7233 A ₄ = -1.3979 × 10 ^-4 A ₆ = 1.1290 × 10 ^-5 A ₈ = -5.3785 × 10 ^-7 A ₁₀ = 9.5545 × 10 ^-9 Zoom data (∞) WE ST TE ω (°) 27.2 15.6 8.8 d ₂ 9.0481 6.7863 3.4551 d ₄ 0.8916 3.9322 7.6929 d ₆ 2.4022 1.6235 1.1992.

FIG. 14 is a diagram showing the chromatic aberration of magnification (a) at the wide-angle end in Example 10 and the chromatic aberration of magnification (b) at the wide-angle end in Example 6 for comparison. As a result, the glass material of the second image inverting optical system 22 is made to satisfy the condition (14) (specifically, n _d = 1.57268, ν _d = 33.50), so that the wide-angle range is easily noticeable. It can be seen that the chromatic aberration of magnification can be effectively corrected.

The above real image type finder optical system of the present invention can be constructed, for example, as follows.

[1] In a real image type finder optical system having, in order from the object side, an objective lens group having a positive refractive power, an image inverting optical system, and an eyepiece lens group having a positive refractive power, the image inverting optical system has an object side. In order from the first image inverting optical system and the second image inverting optical system, the intermediate image forming surface formed by the objective lens group is the exit surface of the first image inverting optical system to the second image inverting optical system. Of the first image inversion optical system, which is arranged in the vicinity of the incident surface, enters from the incident surface 1A so that the optical axes do not intersect in the optical system, and the optical surfaces 1B, 1C, and 1D are sequentially arranged in this order. The second image reversing optical system is configured to be reflected and emitted from the optical surface 1C that also serves as a reflecting surface and a transmitting surface, and the second image inverting optical system is incident from the incident surface 2A so that the optical axes do not intersect in the optical system. The optical surfaces 2B and 2C are configured to reflect in this order, and At least one of the surfaces 1B, 1D, and 2C is a roof reflection part, all transmission surfaces are perpendicular to the optical axis, and the following conditions are satisfied, and a real image type finder optical system is characterized.

30 ° <θ <55 ° (1) 40 ° <Ψ <70 ° (2) where θ is the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B. The angle ψ formed by the optical surface 1B and the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C.
It is an angle with C.

[2] In a real image type finder optical system having, in order from the object side, an objective lens group having a positive refractive power, an image inverting optical system, and an eyepiece lens group having a positive refractive power, the image inverting optical system has an object side. In order from the first image inverting optical system and the second image inverting optical system, the intermediate image forming surface formed by the objective lens group is the exit surface of the first image inverting optical system to the second image inverting optical system. Of the first image inversion optical system, which is arranged in the vicinity of the incident surface, enters from the incident surface 1A so that the optical axes do not intersect in the optical system, and the optical surfaces 1B, 1C, and 1D are sequentially arranged in this order. The second image reversing optical system is configured to be reflected and emitted from the optical surface 1C that also serves as a reflecting surface and a transmitting surface, and the second image inverting optical system is incident from the incident surface 2A so that the optical axes do not intersect in the optical system. It reflects in this order on each of the optical surfaces 2B and 2C and serves as both a reflecting surface and a transmitting surface. The optical surface 2B is configured to emit light, and at least one of the optical surfaces 1B, 1D, and 2C is a roof reflection part, and all transmission surfaces are perpendicular to the optical axis.
A real image finder optical system characterized by satisfying the following conditions.

30 ° <θ <56 ° (3) 30 ° <Ψ <70 ° (4) where θ is the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B. The angle ψ formed by the optical surface 1B and the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C.
It is an angle with C.

[3] The real image type finder optical system described in 1 or 2 above, wherein all the refracting surfaces and reflecting surfaces are surfaces having rotationally symmetric curvatures including flat surfaces.

[4] The real image type finder optical system described in the above item 3, wherein the angles of the respective optical surfaces 1D, 2B and 2C are set as follows.

The optical surface 1 which is reflected by the optical surface 1C
The angle between the optical axis of the ray incident on D and the optical surface 1D is Ψ / 2, and the angle between the optical axis of the ray incident from the optical surface 2A and the optical surface 2B is 180 ° −2θ−Ψ. The angle formed by the optical axis of the light beam reflected by the optical surface 2B and incident on the optical surface 2C and the optical 2C is 90 ° -θ- (Ψ / 2).

[5] The real image type finder optical system described in 3 or 4 above, which satisfies the following condition:

40 ° <θ <56 ° (5) 30 ° <Ψ <58 ° (6) [6] The refractive index of the glass material used in the first image inversion optical system is N _d1. When the refractive index of the glass material used in the second image inversion optical system is N _d2 , N _d1 , N _d2 and θ, Ψ satisfy the following condition, and the real image formula described in the above item 5 is provided. Viewfinder optical system.

N _d1 <1.6 (7) N _d2 <1.6 (8) 40 ° <θ <52 ° (9) 39 ° <Ψ <58 ° (10) [7] The real image type viewfinder optical system according to the above item 6, wherein the optical surfaces 1B and 1D are mirror-coated, and the optical surface 2C is a roof reflector.

[8] In a real image type finder optical system having, in order from the object side, an objective lens group having a positive refractive power, an image inverting optical system, and an eyepiece lens group having a positive refractive power, the image inverting optical system is replaced by the optical system. A real image type viewfinder optical system characterized by satisfying the following conditions while being configured so that the optical axes do not intersect each other.

29 ° <α <75 °, (11) 0.1 <L ₂ / L ₁ <0.49 (12) where α is the optical axis passing through the intermediate imaging plane The angle formed by the optical axis of the objective lens group, L _1, is the intersection of the surface of the objective lens group closest to the object side and the optical axis of the objective lens group, and The distance to the intersection of the reflecting surface and the optical axis is the distance projected on the optical axis of the objective lens group, and L ₂ is the intermediate point from the intersection of the final reflecting surface of the image inverting optical system and the optical axis. The distance from the image plane to the intersection of the first reflecting surface of the image inverting optical system and the optical axis is the distance projected on the optical axis of the objective lens group.

[0129]

[9] The real image type viewfinder optical system according to the above item 8, wherein the optical axis of the objective lens group and the optical axis of the eyepiece lens group are substantially parallel to each other, and the following conditions are satisfied.

0.35 <(L ₁ −L ₂ ) / L ₃ <1.2 (13) where L ₃ is from the intersection with the optical axis of the final reflecting surface of the image inverting optical system. , The distance to the optical axis of the objective lens group.

[10] The image inverting optical system has at least three reflecting portions on the objective lens side of the intermediate image forming surface and at least two reflecting portions on the eyepiece side of the intermediate image forming surface. The real image type finder optical system according to the above item 9, wherein at least one of the reflecting portions is a roof reflecting portion.

[11] The real image described in any one of 1 to 10 above, wherein a glass material satisfying the following conditions is used on at least the eyepiece side of the intermediate image plane in the image inverting optical system. Type viewfinder optical system.

33 <ν _d <34 (14) Here, ν _d is the Abbe number of the glass material represented by ν _d = (n _d −1) / (n _F −n _C ). Where n _d , n _F ,
n _C is the refractive index of the glass material at each wavelength of d line, F line, and C line.

[12] In the real image type finder optical system described in any one of 1 to 11, the first specification is a structure in which a liquid crystal display element which is an in-field display means is arranged near the intermediate image forming surface. The second specification is a structure in which the vicinity of the intermediate image forming surface is an air space, and the position of the entrance surface of the image inverting optical system closer to the eyepiece lens than the vicinity of the intermediate image forming surface is shifted along the optical axis. The real image type finder optical system is characterized in that the deviation of the diopter between the first specification and the second specification is corrected by applying the above.

[13] The first specification is a structure in which the in-field display means is arranged in the vicinity of the intermediate image forming surface, and the second specification is provided with an image inverting optical system in which the air gap is in the vicinity of the intermediate image forming surface. In the real image finder optical system, the first specification and the first specification are applied by applying the positions of the entrance surface of the image inversion optical system located closer to the eyepiece side than the vicinity of the intermediate image forming surface along the optical axis. A real-image viewfinder optical system characterized by correcting the diopter deviation from the second specification.

[0136]

As is apparent from the above description, according to the present invention, a real image type finder provided with an image erecting optical system having a configuration suitable for downsizing and cost reduction of a camera while maintaining good optical performance. An optical system can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view including an optical axis of a real image type finder optical system according to a first embodiment of the present invention.

FIG. 2 is a sectional view including an optical axis of a real image finder optical system according to a second embodiment of the present invention.

FIG. 3 is a sectional view including an optical axis of a real image type finder optical system according to Example 3 of the present invention.

FIG. 4 is a sectional view including an optical axis of a real image type finder optical system according to Example 4 of the present invention.

FIG. 5 is a sectional view including an optical axis of a real image type finder optical system according to Example 5 of the present invention.

FIG. 6 is a sectional view including an optical axis of a real image type finder optical system according to Example 6 of the present invention.

FIG. 7 is a sectional view including an optical axis of a real image type finder optical system according to Example 7 of the present invention.

FIG. 8 is a sectional view including an optical axis of a real image type finder optical system according to Example 8 of the present invention.

FIG. 9 is a sectional view including an optical axis of a real image type finder optical system according to Example 9 of the present invention.

FIG. 10 is a sectional view including an optical axis of a real image type finder optical system according to Example 10 of the present invention.

FIG. 11 is a sectional view including an optical axis of a real image type finder optical system according to Example 11 of the present invention.

FIG. 12 Definitions of angles θ, Ψ, α and distances L ₁ , L ₂ , L
It is a figure which shows the definition of ₃ .

FIG. 13 is a diagram showing a definition of an angle χ.

FIG. 14 is a diagram showing chromatic aberration of magnification (a) at the wide-angle end in Example 6 and chromatic aberration of magnification (b) in Comparative Example in comparison.

[Explanation of symbols]

1A, 1B, 1C, 1D ... Optical surface 2A, 2B, 2C, 2D ... Optical surface 10 ... Objective lens group 20 ... Image inversion optical system 30 ... Eyepiece group 21 ... First image inverting optical system 22 ... Second image inversion optical system 23 ... Positive lens G1 ... 1st group G2 ... Second group G3 ... Group 3 G4 ... Group 4 EP ... Exit pupil (eye point)

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H018 AA11                 2H042 CA02 CA12 CA18                 2H087 KA14 RA05 RA41 TA01 TA02

Claims (3)

[Claims] 1. A real image finder optical system having, in order from the object side, an objective lens group having a positive refractive power, an image inverting optical system, and an eyepiece lens group having a positive refractive power, wherein the image inverting optical system is arranged from the object side. In order, a first image inverting optical system and a second image inverting optical system are provided, and the intermediate image forming surface formed by the objective lens group is the exit surface of the first image inverting optical system or the second image inverting optical system. The first image inversion optical system is arranged near the incident surface and enters from the incident surface 1A so that the optical axes do not intersect in the optical system, and the optical surfaces 1B, 1C,
It is configured so that each surface of 1D is reflected in this order and is emitted from an optical surface 1C that also serves as a reflecting surface and a transmitting surface, and the second image inverting optical system is incident so that the optical axes do not intersect in the optical system. The optical surface 1 is configured so that the light enters from the surface 2A and is reflected by the optical surfaces 2B and 2C in this order.
At least one of B, 1D, and 2C is a roof reflection part, all transmission surfaces are perpendicular to the optical axis, and the following conditions are satisfied, and a real image type viewfinder optical system is characterized. 30 ° <θ <55 ° (1) 40 ° <Ψ <70 ° (2) where θ is the angle between the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B. , Ψ is the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C and the optical surface 1
It is an angle with C. 2. A real image finder optical system having an objective lens group having a positive refractive power, an image inverting optical system, and an eyepiece lens group having a positive refractive power in order from the object side, wherein the image inverting optical system is arranged from the object side. In order, a first image inverting optical system and a second image inverting optical system are provided, and the intermediate image forming surface formed by the objective lens group is the exit surface of the first image inverting optical system or the second image inverting optical system. The first image inversion optical system is arranged in the vicinity of the incident surface and enters from the incident surface 1A so that the optical axes do not intersect in the optical system, and the optical surfaces 1B, 1C,
It is configured so that each surface of 1D is reflected in this order and is emitted from an optical surface 1C that also serves as a reflecting surface and a transmitting surface, and the second image inverting optical system is incident so that the optical axes do not intersect in the optical system. It is configured such that the light enters from the surface 2A, is reflected in this order on each of the optical surfaces 2B and 2C, and is emitted from the optical surface 2B that also serves as a reflection surface and a transmission surface, and at least one of the optical surfaces 1B, 1D, and 2C. One is a roof reflection section, all transmission surfaces are perpendicular to the optical axis, and the following conditions are satisfied, and a real image type viewfinder optical system is characterized. 30 ° <θ <56 ° (3) 30 ° <Ψ <70 ° (4) where θ is the angle between the optical axis of the light beam incident on the optical surface 1B and the optical surface 1B. , Ψ is the optical axis of the light beam reflected by the optical surface 1B and incident on the optical surface 1C and the optical surface 1
It is an angle with C. 3. A real image finder optical system having, in order from the object side, an objective lens group having a positive refractive power, an image inverting optical system, and an eyepiece lens group having a positive refractive power, wherein the image inverting optical system is provided in the optical system. A real-image viewfinder optical system characterized by satisfying the following conditions while being configured so that the optical axes do not intersect. 29 ° <α <75 °, (11) 0.1 <L ₂ / L ₁ <0.49 (12) where α is the objective lens group whose optical axis passing through the intermediate image plane is The angle L ₁ with the optical axis of the objective lens group is the intersection of the surface of the objective lens group closest to the object and the optical axis of the objective lens group with the first reflecting surface of the image inverting optical system after the intermediate image plane. The distance to the intersection with the optical axis is the distance projected on the optical axis of the objective lens group, and L ₂ is from the intersection with the optical axis of the final reflecting surface of the image inverting optical system to the intermediate image formation surface. The distance to the intersection of the first reflecting surface of the image inverting optical system and the optical axis thereafter is the distance projected on the optical axis of the objective lens group.