JP3375170B2 - Variable magnification relay optical system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system for forming a viewfinder image of a single-lens reflex camera on an electronic image pickup device.

[0002]

2. Description of the Related Art There has been an attempt to project a viewfinder image of a camera on an electronic image pickup device and use the image for remote control of the camera. However, most of the attempts have been made by incorporating them into a large-scale experimental device, and there are few examples in which they can be directly applied to the finder of a general camera which is generally widely used. On the other hand, attempts have been made to incorporate an electronic image pickup device into the finder optical system of a normal camera, and an example of this has been introduced in the photo industry (July 1988 issue). The example introduced is an optical system with a fixed magnification. Has become. In addition, JP-A-62-61036 and JP-A-62-61036
No. 129828, JP 62-141862, JP 62-141864, JP 62-1
Japanese Patent No. 50234 also discloses an invention related to this incorporation, but these are also fixed magnification optical systems.

[0003]

By the way, if a video camera with a lens is attached to the back of the finder for the purpose of expanding the functions of the camera, a part of the finder screen (hereinafter, also simply referred to as a screen) on the monitor TV. Can be reflected. However, when the video camera lens is a single focus lens, the observation magnification cannot be changed, and when the video camera lens is a zoom lens, the entrance pupil is at the back, making it difficult to project the entire screen. Is. If the magnification is fixed so that the entire surface of the screen can be observed if the magnification cannot be changed, it is difficult to focus with an electronic image sensor with low resolution, and conversely, the magnification is fixed to allow sufficient focusing. However, there is a problem that only a part of the screen can be observed.

On the other hand, if the parts behind the viewfinder screen are removed and an appropriate close-up photography attachment is added in front of the video camera with a lens, or a macro lens is attached in front of the electronic image pickup device, the screen can be displayed. However, the method of reducing and projecting the screen on the electronic image pickup device by using a simple macro lens causes a change in the total length of the finder portion, which results in a poorly organized product. When combined with a normal zoom lens, the number of lens components increases, making it expensive.
Further, since the lens diameter is determined at the maximum luminous flux diameter, the effective diameter is large, and in this case, the product is not well organized. Another drawback of zoom lenses is that they do not allow quick zooming.

In viewfinder layout, the viewfinder optical system uses mirrors and prisms, and has an optical path formed by appropriately bending a long expanded optical path length. In addition, since the image displayed on the screen is generally a mirror image of left and right, it is necessary to have a mechanism for eliminating the mirror image. Therefore, if a simple macro lens or an ordinary zoom lens is used, the effective diameter on the screen side is large, and the overall size is further increased.

In view of the above problems, the present invention has an object to form a viewfinder optical system which is compact, inexpensive, and capable of rapid zooming operation, and projects a viewfinder image of a single-lens reflex camera onto an electronic image pickup device. And

[0007]

A variable power relay optical system according to the first aspect of the present invention is an optical system for forming a viewfinder image of a single-lens reflex camera on an electronic image pickup device, and has at least two different magnifications. At one magnification, the entire range photographed by the single-lens reflex camera can be observed, and at least one magnification, a part of the range photographed by the single-lens reflex camera can be magnified and observed. In the variable power relay optical system, the variable power relay optical system is arranged in the optical path order on the first reflection system emission optical path side in the vicinity of the screen surface of the single-lens reflex camera , and the variable power relay optical system changes the magnification by moving in and out of the optical path. a zoom interchangeable lens to perform a second reflecting system which deflects the light from the zoom interchangeable lens, and a imaging lens, the refractive power of the zoom interchangeable lens, the screen When observing the body as a negative refractive power, and, in accordance with the magnification of the variable magnification, positional relationship between the imaging lens and the electronic image pickup device is characterized in that change.

Further, in the variable power relay optical system according to the second aspect of the invention, in addition to the configuration of the first aspect of the invention, the refractive power of the variable power interchangeable lens has a negative refractive power when observing the entire screen. In addition, when observing a part of the screen, a positive refractive power is used. The variable power relay optical system according to the third aspect of the invention is characterized in that, in addition to the configuration of the second aspect of the invention, the variable power interchangeable lens having the negative refractive power is a single lens or a cemented lens. There is. In addition, in the variable power relay optical system according to the fourth aspect of the invention, in addition to the configuration of the third aspect of the invention, the variable power interchangeable lens having the negative refracting power has a surface closest to the screen on the electronic image pickup element side. The feature is that the absolute value of the radius of curvature is made larger than that of the surface. The variable power relay optical system according to the fifth aspect of the invention is characterized in that, in addition to the configuration of the second aspect of the invention, the variable power interchangeable lens having the positive refractive power is a cemented lens or a single lens. There is. Further, in the variable power relay optical system according to the sixth aspect of the invention, in addition to the configuration of the fifth aspect of the invention, the variable power interchangeable lens having the positive refractive power is such that the surface closest to the screen is the electronic image pickup element side. The feature is that the absolute value of the radius of curvature is made larger than that of the surface. In addition, in the variable power relay optical system according to the seventh invention, in addition to the configuration of the sixth invention, the screen side surface of the variable power interchangeable lens having the positive refractive power is a flat surface or a convex surface on the screen side. It is characterized by being. Further, in the variable power relay optical system according to the eighth aspect of the invention, in addition to the configuration of the second aspect of the invention, the variable power interchangeable lens having the positive refracting power is composed of a double lens including a concave lens and a convex lens. It is characterized by that. Also, in the variable power relay optical system according to the ninth aspect of the invention, in addition to the configuration of the eighth aspect of the invention, the variable power interchangeable lens having the negative refractive power is arranged in this order from the screen side to a convex lens and a concave lens. Is characterized by. The variable power relay optical system according to the tenth aspect of the invention is characterized in that, in addition to the configuration of the ninth aspect of the invention, the surfaces of the concave lens and the convex lens having large radii of curvature are directed toward the screen side. There is. A variable power relay according to the eleventh invention
In addition to the configuration of the first invention, the optical system includes the second reflection
The system is characterized in that the reflective surface of the system is only the roof surface.
The variable magnification relay optical system according to the 12th aspect of the present invention is
In addition to the constitution of the eleventh invention, the first reflection system is a pentad
The feature is that it is composed of Ha prism. Also books
A variable power relay optical system according to a thirteenth invention is the first invention.
In addition to the above configuration, the first reflection system has a penta roof prism.
And a reflection system in which the second reflection system reflects only once
It is characterized by being composed of.

[0009]

The variable power exchange lens of this switching optical system is arranged at a position apart from the imaging lens between the imaging lens and the screen, and the refractive power of the variable power exchange lens is observed when observing the entire screen. By making the value negative and making it positive when observing a part of the screen, the variable magnification interchangeable lens has a function of adjusting the diameter of the light flux, and the effective diameter is made small, thereby making the whole compact. As a result, the optical system has a constant overall length, is compact and inexpensive, has a small number of constituent lenses, and allows the user to perform a quick zoom operation.

FIG. 1 is a conceptual diagram showing the overall structure of a variable power relay optical system of the present invention. 1 is a screen, 2 is a first prism system, 3 is a variable power interchangeable lens, 4 is a second prism system, 5
Is an imaging lens, 6 is a filter system, 7 is an electronic image sensor,
8 is an optical axis. The light flux from the screen 1 passes through the first prism system 2, the variable power interchangeable lens 3, the second prism system 4
After that, the light passes through the imaging lens 5 and the filter system 6, and finally an image is formed on the electronic image pickup device 7.

FIG. 1A shows a state in which the projection magnification for the electronic image pickup device 7 is low and the variable power interchangeable lens 3 has a negative refracting power. FIG. 1B shows a state in which the projection magnification with respect to the electronic image sensor 7 is high, and the variable power interchangeable lens 3 has a positive refractive power.
In FIG. 1A, it is shown that the chief ray 9 emitted from the screen 1 drops sharply, is returned to an appropriate angle by the variable power interchangeable lens 3 having negative refractive power, and enters the imaging lens 5. There is. As a result, the entire screen 1 is reflected on the electronic image pickup device 7 while keeping the effective diameter of the first prism system 2 small.

On the other hand, in FIG. 1B, the variable power interchangeable lens 3
It is shown that the image forming magnification is increased by setting the positive refraction power to, and therefore only the central portion of the screen 1 is displayed on the electronic image pickup element 7. Therefore,
The user magnifies and observes the central portion of the screen 1 and can easily focus.

The shorter the focal length of the variable power interchangeable lens 3 having a positive refracting power, the larger the observation magnification. However, the length of the optical path of the first prism system 2 is limited and the length is substantially shorter than the air conversion length. It is not possible. Like a penta prism,
When the first prism system 2 bends the traveling direction of light, the smaller the effective diameter of the first prism system 2 is, the shorter the development optical path length is. Therefore, the focal length of the variable power interchangeable lens 3 having a positive refractive power can be shortened. become. That's why the first
Reducing the effective diameter of the prism system 2 is also important for zooming. With such a configuration, it is possible to use a pentaprism incorporated in a normal finder for the first prism system 2. An example is shown in FIG. 4 described later. Furthermore, regarding the scaling factor,
It is desirable that the magnification of zooming is 3 times or more, and if it is 2 times or more, the effect of zooming appears clearly, but at least 1.5
If there is no more than double, there is no effect of scaling.

Further, in general, due to manufacturing errors,
When the magnification is changed, the image forming position shifts between the high magnification and the low magnification, so an adjustment mechanism for the shift is indispensable. for that reason,
A mechanism for moving a part of the optical system in the direction of the optical axis is required, and the fact that the imaging lens 5 moves along the optical axis 8 in accordance with zooming as in the later-described embodiments of the present invention means that It is practical because the travel allowance can include adjustments.

[0015]

First Embodiment FIGS. 2 (a) and 2 (b) are configuration diagrams of a first embodiment of a variable power relay optical system according to the present invention, which is developed in the optical axis direction, and FIG. ) And FIG. 5B are curve diagrams of spherical aberration, astigmatism, distortion, color of magnification, and coma for the first example. (A) corresponds to low magnification and (b) corresponds to high magnification. In this embodiment, as described above, the position of the imaging lens 5 and the electronic image pickup device 7 is adjusted according to the magnification of the magnification change as an adjusting mechanism for the deviation of the image formation position at the time of magnification change caused by the manufacturing error. It has a structure in which relationships change.

The screen 1 is composed of a matte lens and a condenser lens, and the variable power interchangeable lens 3 is a single lens having a negative refracting power in FIG. 2A and a cemented lens having a positive refracting power in FIG. 2B. It's a lens. This corresponds to the performance of the imaging lens 5.
Depending on the performance of, the variable power interchangeable lens 3 having a negative refractive power may be a cemented lens, or the variable power interchangeable lens 3 having a positive refractive power may be a single lens.

In the variable power interchangeable lens 3 having a negative refractive power, the absolute value of the radius of curvature is made larger by making the surface of the screen 1 side closer to the surface of the electronic image pickup device 7 side.
The aberration generated in the variable power interchangeable lens 3 having a negative refractive power is reduced. On the other hand, even in the variable power interchangeable lens 3 having a positive refractive power, the surface closest to the screen 1 is the electronic photographing element 7
By making the absolute value of the radius of curvature larger than that of the surface on the side, the aberration generated in the variable power interchangeable lens 3 having a positive refractive power is reduced. In this case, it is desirable that the surface of the variable power interchangeable lens 3 having a positive refractive power on the screen 1 side is a flat surface or a convex surface on the screen 1 side.
It is desirable that the side surface is convex toward the electronic image pickup device 7 side.

The data of the first embodiment are shown below. However,
r _i (i = 0 to 22) is the radius of curvature or the name of the surface of the surface number i in the optical element forming the optical system, and d _i (i = 0
21) is the optical axis distance between the surface of the surface number i and the surface of the surface number i + 1, and n _k and ν _k (k = 1 to 12) are the refractive index of the optical glass used in the optical element described in the same row. , Appe number.
It should be noted that the virtual surface is not an existing surface, but is a virtual surface provided by design for matching the surface numbers of prisms and the like in each embodiment. Screen 1 to first prism system 2 [Reference: FIG. 2 (a) or FIG. 2 (b)] r ₀ = screen surface d ₀ = 1.8 r ₁ = ∞ d ₁ = 5.1 n ₁ = 1.6516 ν ₁ = 58.5 r _{2 = - 64.89 d 2 = 1.5} r 3 = ∞ d 3 = 92 n 2 = 1.5163 ν 2 = 64.2 r 4 = ∞ d 4 = D1

Variable magnification interchangeable lens 3 having negative refracting power [Refer to FIG. 2 (a)] r ₅ = ∞ d ₅ = 1.2 n ₃ = 1.6968 ν ₃ = 55.5 r ₆ = virtual surface d ₆ = 0 n ₄ = 1.6968 ν ₄ = 55.5 r ₇ = 65.05 d ₇ = D2

Variable magnification interchangeable lens 3 having a positive refractive power [Refer to FIG. 2B] r ₅ = 113.30 d ₅ = 5.3 n ₃ = 1.5163 ν ₃ = 64.2 r ₆ = −21.80 d ₆ = 1.0 n ₄ = 1.6477 ν ₄ = 33.8 r ₇ = -41.49 d ₇ = D2

Second prism system 4 [Reference drawing: FIG. 2 (a) or FIG. 2 (b)] r ₈ = ∞ d ₈ = 55.5 n ₅ = 1.5163 ν ₅ = 64.2 r ₉ = ∞ d ₉ = D3

Image forming lens 5 [Refer to FIG. 2 (a) or FIG. 2 (b)] r ₁₀ = 20.4 d ₁₀ = 2.3 n ₆ = 1.7432 ν ₆ = 49.3 r ₁₁ = −227.0 d ₁₁ = 0.1 r _{12 = 8.0 d 12 = 2.3 n 7} = 1.6228 ν 7 = 57.1 r 13 = - 49.8 d 13 = 0.8 n 8 = 1.7725 ν 8 = 49.7 r 14 = 5.8 d 14 = 2.1 r 15 = stop d ₁₅ = 1.8 r ₁₆ = _{- 5.3 d 16 = 0.8 n 9} = 1.7283 ν 9 = 28.5 r 17 = - 66.3 d 17 = 2.4 n 10 = 1.7292 ν 10 = 54.7 r 18 = - 7.4 d 18 = 0.1 r 19 = 251.7 d 19 = 1.9 n 11 = 1.7725 ν ₁₁ = 49.7 r ₂₀ = −13.8 d ₂₀ = D4

Filter System 6 to Electronic Imaging Device 7 [Reference: FIG. 2 (a) or FIG. 2 (b)] r ₂₁ = ∞ d ₂₁ = 6.0 n ₁₂ = 1.55 ν ₁₂ = 63.0 r ₂₂ = imaging surface

[0024]   D1, D2, D3 and D4 at low and high magnifications are the following numerical values [Refer to Fig. 2 (A) and FIG.2 (b)].                         D1 D2 D3 D4 Low fold (-1 / 7.5 fold) 1.00 6.10 15.58 17.17 High magnification (-1 / 3.4 times) 1.00 1.00 19.99 12.76

Second Embodiment FIGS. 3 (a) and 3 (b) are configuration diagrams showing a second embodiment of the variable power relay optical system according to the present invention in the optical axis direction, and FIG. It is a figure which shows the example which has arrange | positioned 2 Example to the actual single-lens reflex camera. 6A and 6B are curve diagrams of spherical aberration, astigmatism, distortion, color of magnification, and coma for the second example.
(A) corresponds to low magnification and (b) corresponds to high magnification. The second embodiment is more compact than the first embodiment. That is, the focal length of the variable power interchangeable lens 3 having a negative refracting power is shortened, but the load on the variable power interchangeable lens 3 having a negative refractive power is increased, so that
A variable power interchangeable lens 3 having a negative refractive power for removing aberrations.
Is composed of a cemented lens consisting of a concave lens and a convex lens.

Aberrations which have been a problem in the second embodiment are mainly astigmatism and distortion. In order to remove the astigmatic difference, it is desirable that the variable power interchangeable lens 3 having a negative refractive power, which is composed of a concave lens and a convex lens, be arranged in order of positive and negative from the screen 1 side. Further, in order to remove the distortion aberration, it is preferable to direct the surface of each lens having a large radius of curvature toward the screen 1 side, and in particular, the surface closest to the screen 1 should be a flat surface or a gentle convex toward the screen 1 side. It is desirable that Variable magnification interchangeable lens 3 having negative refractive power 3
, The negative lens in the group has a strong refractive power. Therefore, it is firstly necessary to construct the negative lens so that the aberration is less than the refracting power, and then the positive lens having the weakest refracting power is used to generate the reverse aberration so that the negative lens It is necessary to have a configuration that cancels aberrations.

From the perspective of how the principal ray travels, the function of the variable power interchangeable lens 3 as a whole is to weaken the angle formed by the principal ray with the optical axis. Three of the four surfaces of the variable power interchangeable lens 3 function to weaken the angle formed by the principal ray with the optical axis, and one surface functions to strengthen the angle formed by the principal ray with the optical axis. That is, by sharing the action by the three surfaces, the occurrence of aberrations is reduced, and the remaining one surface cancels the aberrations generated by the three surfaces.

On the other hand, when viewed from the way of the marginal rays on the axis, the function of the variable magnification interchangeable lens 3 as a whole is to strengthen the angle formed by the marginal rays on the axis with the optical axis. Three of the four surfaces of the variable power interchangeable lens 3 act to strengthen the angle formed by the peripheral rays on the axis with the optical axis, and one surface forms the angle formed by the peripheral rays on the axis with the optical axis. Acts to weaken. That is, it is the same as the case of the chief ray that the occurrence of aberration is reduced by sharing the action by the three surfaces and the remaining one surface cancels the aberration generated by the three surfaces. Also,
Since the positional relationship between the variable power interchangeable lens 3 having a positive refracting power and the imaging lens 5 has also changed, the color of the magnification has changed, and due to the adjustment, there is a slight change from the first embodiment. And then
Except for the variable power interchangeable lens 3, it is common to the first embodiment.

In FIG. 4 showing an example in which the second embodiment is applied to an actual single-lens reflex camera, 10 is a taking lens and 11 is a quick return mirror. The first prism system 2 is composed of a penta prism, and the variable power interchangeable lens 3 is configured by arranging a variable power lens 3a and a variable power lens 3b in close proximity to each other so that they can be exchanged as needed for variable power. The imaging lens 5 moves along the optical axis 8 in accordance with the replacement.

In the above case, since the first prism system 2 is a penta roof prism, the image is a normal image when it exits the first prism system 2. It is reflected upward by the second prism system 4, but a single reflection results in a mirror image. At this time, first, if the reflecting surface of the second prism system 4 is a roof surface, it is reflected twice there, so that a normal image can be obtained. In the second prism system 4, the electronic image pickup device 7 is used as a single reflection device and the reading direction can be reversed, or an electric means such as an image memory serving as a buffer and the reading is performed in reverse. It is also possible to get an image.

On the contrary, in the case of a single-lens reflex camera in which the first prism system 2 can be exchanged, the first prism system 2 itself is constituted by a penta prism which does not use a roof surface, and when the first prism system 2 exits. It is also possible to obtain a normal image on the electronic image pickup device 7 by forming a mirror image and reflecting the second prism system 4 by a single reflection. In this way, both the first prism system 2 and the second prism system 4 can be manufactured at low cost by not using the roof surface.

The data of the second embodiment are shown below. However,
r _j (j = 0 to 23) is the radius of curvature or the name of the surface of surface number j in the optical element forming the optical system, d _j
(J = 0 to 22) is the interval on the optical axis between the surface of surface number j and the surface of surface number j + 1, and n _l and ν _l (l = 1 to 12) are the optics used in the optical element described in the same row. It is the refractive index of glass and the Abbe number. Screen 1 to first prism system 2 [Reference: FIG. 3 (a) or FIG. 3 (b)] r ₀ = screen surface d ₀ = 1.8 r ₁ = ∞ d ₁ = 5.1 n ₁ = 1.6516 ν ₁ = 58.5 r _{2 = - 64.89 d 2 = 1.5} r 3 = ∞ d 3 = 92 n 2 = 1.5163 ν 2 = 64.2 r 4 = ∞ d 4 = D1

Variable power interchangeable lens 3 having a negative refractive power [Refer to FIG. 3 (a)] r ₅ = ∞ d ₅ = 2.2 n ₃ = 1.6968 ν ₃ = 55.5 r ₆ = −51.85 d ₆ = 0.1 r ₇ = ∞ d ₇ = 1.2 n ₄ = 1.6968 ν ₄ = 55.5 r ₈ = 19.96 d ₈ = D2

Variable power interchangeable lens 3 having a positive refractive power [Refer to FIG. 3 (b)] r ₅ = 93.74 d ₅ = 5.3 n ₃ = 1.5163 ν ₃ = 64.2 r ₆ = −20.97 d ₆ = 1.0 n _{4 = 1.6477 ν 4 = 33.8 r} 7 = - 43.28 d 7 = D2 r 8 = imaginary plane d ₈ = 0

Second prism system 4 [Reference: FIG. 3 (a) or FIG. 3 (b)] r ₉ = ∞ d ₉ = 55.5 n ₅ = 1.5163 ν ₅ = 64.2 r ₁₀ = ∞ d ₁₀ = D3

Image forming lens 5 [Reference: FIG. 3 (a) or FIG. 3 (b)] r ₁₁ = 20.4 d ₁₁ = 2.3 n ₆ = 1.7432 ν ₆ = 49.3 r ₁₂ = −227.0 d ₁₂ = 0.1 r _{13 = 8.0 d 13 = 2.3 n 7} = 1.6228 ν 7 = 57.1 r 14 = - 49.8 d 14 = 0.8 n 8 = 1.7725 ν 8 = 49.7 r 15 = 5.8 d 15 = 2.1 r 16 = stop d ₁₆ = 1.8 r ₁₇ = _{- 5.3 d 17 = 0.8 n 9} = 1.7283 ν 9 = 28.5 r 18 = - 66.3 d 18 = 2.4 n 10 = 1.7292 ν 10 = 54.7 r 19 = - 7.4 d 19 = 0.1 r 20 = 251.7 d 20 = 1.9 n 11 = 1.7725 ν ₁₁ = 49.7 r ₂₁ ＝ －13.8 d ₂₁ ＝ D4

Filter System 6 to Electronic Imaging Device 7 [Reference: FIG. 3 (a) or FIG. 3 (b)] r ₂₂ = ∞ d ₂₂ = 6.0 n ₁₂ = 1.55 ν ₁₂ = 63.0 r ₂₃ = imaging surface

[0038]   D1, D2, D3 and D4 at low and high magnifications are the following numerical values [Refer to Fig. 3 (A) and FIG.3 (b)].                         D1 D2 D3 D4 Low times (-1/7 times) 1.00 3.85 2.78 19.09 High magnification (-1 / 3.4 times) 1.05 1.00 9.25 12.76

[0039]

As described above, the variable power relay optical system of the present invention is compact, can be manufactured at a low cost, and can perform a rapid variable power operation, and the aberration can be corrected well. This has an important practical advantage that a finder image in a single-lens reflex camera can be projected on an electronic image pickup device.

[Brief description of drawings]

FIG. 1A is a conceptual diagram (state at low magnification) showing the overall configuration of a variable power relay optical system according to the present invention. (B) It is a conceptual diagram (state at the time of high magnification) which shows the whole structure of the variable power relay optical system by this invention.

FIG. 2A is a configuration diagram (a state at a low magnification) in which the first embodiment of the variable power relay optical system according to the present invention is developed in the optical axis direction. FIG. 2B is a configuration diagram (a state at high magnification) in which the first embodiment of the variable power relay optical system according to the present invention is developed in the optical axis direction.

FIG. 3A is a configuration diagram (a state at low magnification) in which a second embodiment of the variable power relay optical system according to the present invention is developed in the optical axis direction. (B) is a block diagram showing a second embodiment of the variable power relay optical system according to the present invention in the optical axis direction (state at high magnification).

FIG. 4 is a diagram showing an example in which a second embodiment of the variable power relay optical system according to the present invention is arranged in an actual single-lens reflex camera.

FIG. 5A is a curve diagram of spherical aberration, astigmatism, distortion, color of magnification, and coma in the first example (state at low magnification). FIG. 7B is a curve diagram of spherical aberration, astigmatism, distortion, magnification color, and coma in the first example (state at high magnification).

6A is a curve diagram of spherical aberration, astigmatism, distortion, color of magnification, and coma in the second example (state at low magnification). FIG. (B) A curve diagram of spherical aberration, astigmatism, distortion, color of magnification, and coma in the second example (state at high magnification).

[Explanation of symbols]

1 screen 2 First prism system 3 variable magnification interchangeable lens 4 Second prism system 5 Imaging lens 6 filter system 7 Electronic image sensor 8 optical axes 9 chief rays 10 Shooting lens 11 quick return mirror

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-141862 (JP, A) JP-A-59-219732 (JP, A) JP-A-57-74719 (JP, A) JP-A-62- 61036 (JP, A) JP-A-4-264434 (JP, A) JP-A-2-176613 (JP, A) JP-A-3-217831 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03B 13/00-13/28 H04N 5 / 222,5 / 257 G02B 15/00-15/12

Claims (13)

(57) [Claims] 1. An optical system for forming a viewfinder image of a single-lens reflex camera on an electronic image pickup device, which has at least two magnifications, one of which is the entire range photographed by the single-lens reflex camera. Can be observed, at least one magnification is a variable power relay optical system configured to be observed by enlarging a part of the range taken by the single-lens reflex camera, the variable power relay optical system is , In the order of the optical path , the first near the screen surface of the single-lens reflex camera.
A variable power interchangeable lens arranged on the reflection system exit optical path side and variable power by entering and leaving the optical path, and the variable power interchangeable lens
A second reflecting system which deflects the light from an imaging lens, the refractive power of the zoom interchangeable lens, and a negative refractive power when observing the entire screen, and, according to the magnification of the variable magnification And a variable power relay optical system in which the positional relationship between the imaging lens and the electronic image pickup device changes. 2. The variable power interchangeable lens has a negative refractive power when observing the entire screen and a positive refractive power when observing a part of the screen. The variable power relay optical system described in 1. 3. The variable power relay optical system according to claim 2, wherein the variable power interchangeable lens having the negative refractive power is a single lens or a cemented lens. 4. The variable power interchangeable lens having a negative refracting power is characterized in that the absolute value of the radius of curvature is larger on the most screen side surface than the electronic image pickup element side surface. Variable magnification relay optical system described. 5. The variable power relay optical system according to claim 2, wherein the variable power interchangeable lens having a positive refractive power is a cemented lens or a single lens. 6. The variable power interchangeable lens having a positive refracting power is characterized in that an absolute value of a radius of curvature is made larger on a surface closest to a screen than a surface closer to an electronic image pickup device. Variable magnification relay optical system described in. 7. The variable power relay optical system according to claim 6, wherein a screen side surface of the variable power interchangeable lens having a positive refractive power is a flat surface or a convex surface on the screen side. 8. The variable power relay optical system according to claim 2, wherein the variable power interchangeable lens having the positive refracting power is composed of two lenses, a concave lens and a convex lens. 9. The variable power relay optical system according to claim 8, wherein the variable power interchangeable lens having the negative refracting power is arranged in order of a convex lens and a concave lens from the screen side. 10. The variable power relay optical system according to claim 9, wherein the surfaces of the concave lens and the convex lens having large radii of curvature are directed toward the screen side. 11. A reflective surface of the second reflective system is only a roof surface.
Variable magnification relay light according to claim 1, characterized in that
Academic system. 12. A penta roof prism for the first reflection system.
12. The variable power lens according to claim 11, characterized in that
Ray optics. 13. The first reflection system is a penta prism.
And the second reflection system is a reflection system that reflects only once.
The zoom lens according to claim 1, characterized in that
Ray optics.