JPH085911A - Variable power lens system and variable power finder system - Google Patents

Abstract

PURPOSE:To provide a three-focus switching variable power lens system, etc., at low cost. CONSTITUTION:The variable power lens system has a 1st afocal conversion lens system composed of a concave lens L1 which is made of plastic and has aspherical surfaces as both its surfaces and a concave lens L2 in order from the object side and a 2nd afocal conversion lens system composed of a concave lens L3, a cemented concave lens L4 of a convex lens and a concave lens, a plastic aspherical convex lens L5, and a cemented convex lens L6 of a concave lens and a convex lens, has a stop arranged, and also has an image forming lens system composed of a convex lens L7, a concave lens L8, and a plastic aspherical convex lens L9, thereby serving as a wide angle lens. The 1st conversion lens system is rotated by 90 deg. to obtain intermediate focal length through the constitution of only the 2nd conversion lens system and image forming lens system for photography through a through hole formed in the lens barrel of the 1st conversion lens, and the 2nd conversion lens system is rotated by 180 deg. to obtain a telephoto lens.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable-magnification lens system mainly used for video cameras, in which the angle of view of the lens can be switched, and a variable-magnification finder system linked with this variable-magnification lens system. Is. It is an object of the present invention to provide a lens and a finder that can be downsized, have a simple structure, and can be manufactured at extremely low cost, in spite of a high zoom ratio including a wide angle.

[0002]

2. Description of the Related Art Conventionally, there are various types of lens systems as described below as a lens system capable of changing the magnification by about 10 times.

The so-called front lens feeding type zoom lens is a convex, concave, concave, and convex refractive power arrangement as a whole, and the first group convex lens is extended to perform focusing to mechanically form a second group concave lens and a third group concave lens. The feature is that the function of focusing and zooming is optically separated by performing zooming in conjunction with.

Further, in recent years, in a video camera, with a refracting power arrangement of convex, concave, convex, and convex as a whole, a diaphragm is arranged immediately in front of the convex lens of the third group, and the concave lens of the second group and the convex lens of the fourth group are
The so-called inner focus system, in which the position is controlled by a microcomputer based on the zoom magnification setting and the distance information and is linked, has become the mainstream. This method is easy to reduce the cost by downsizing and reducing the number of lenses, and because the focus lens is small and lightweight, it is an auto focus that performs focusing by the so-called hill climbing method while watching the contrast change of the image signal of the image sensor. This is a feature that is suitable for performing the waste system at high speed.

As another inner focus system,
Convex, concave, concave, convex, and convex refractive power arrangements as a whole constitute an afocal system from the 1st to 4th groups, a diaphragm is arranged immediately in front of the 5th group convex lens, and the 2nd group concave lens and the 3rd group There is a system in which the concave lens is position-controlled by a microcomputer and linked. Since this method is an inner focus method, high-speed audio
It has a feature that it is suitable for a to-focus system.

[0006]

By the way, in the above-mentioned conventional variable power lens system, when it was attempted to see the field of view with an optical finder, there were the following problems, respectively.

In the so-called front lens feeding type zoom lens, the optical system relating to focusing and zooming is arranged in front of the diaphragm, so that the beam splitter or the like is used immediately before the diaphragm to enter the viewfinder optical system. Even if the light beam is split,
It is convenient for a single-lens viewfinder because it is possible to check optical information related to focusing and zooming with the viewfinder.
Because the front lens for focusing is large and heavy,
It is unsuitable for speeding up caching.

In the so-called four-group inner focus, the fourth-group convex lens, which plays a role of focusing correction and focusing in zooming, is arranged behind the diaphragm, so that the lens is moved to the finder from immediately before the diaphragm. Even if the light flux is branched, the finder image is not corrected for focus, so another focus correction device is required for the finder optical system, the mechanism is complicated and the cost is high, and it is not suitable for a single-lens viewfinder.

Further, the so-called four-group inner-focus lens and a finder objective lens having the same refractive power arrangement are arranged with their optical axes parallel to each other, and the movable lens is mechanically interlocked with the photographic lens. A binocular variable magnification lens and variable magnification finder can be realized by making the inverted image upright so that it can be seen through the eyepiece. However, in this method, when the angle of view at the wide-angle end exceeds 50 °, the front lens of the lens and the finder becomes extremely large, the parallax becomes large at a short distance, and the cost also increases. I cannot achieve my purpose.

In addition, the inner focus system having a convex, concave, concave, convex, and convex refractive power arrangement as a whole is suitable for the autofocus system, and the lens system behind the diaphragm is fixed. Therefore, it is suitable for a single-lens viewfinder. However, since the second group and the third group are concave lenses, the luminous flux spreads and the diaphragm diameter increases, which is disadvantageous for downsizing.
The viewfinder optical system must straddle a large diaphragm mechanism, which is disadvantageous in downsizing of the entire system.

The present invention is directed to a super wide angle, high zoom ratio, autofocus.
The objective is to provide an extremely low-cost variable power lens system and variable power finder system that are suitable for dust and interlocking viewfinders. For example, the view angle changes from a super wide angle of about 70 ° to about 10 times. Attempting to realize a lens with a conventional zoom lens leads to an increase in manufacturing cost and an increase in the lens outer diameter, so that the size of the single-lens viewfinder or the twin-lens viewfinder is entirely increased to achieve the object of the present invention. Can not.

[0012]

The structure of the present invention will be described below.

According to a first aspect of the present invention, in order from the object side, a substantially afocal first conversion lens,
In a variable power lens system including a substantially afocal second conversion lens and an imaging lens having a positive refracting power as a whole, the first conversion lens has an angular magnification of 1 or less and a second A wide-angle lens when the angular magnification of the conversion lens is set to 1 or less. When the first conversion lens is retracted and only the second conversion lens and the imaging lens are used, an intermediate focal length is obtained. Further, from this state, the second conversion lens is inverted by 180 ° to form a telephoto lens with an angular magnification of 1 or more, and the focal length is switched in three steps.

According to a second aspect of the present invention, in the variable power lens system according to the first aspect, the first conversion lens has a concave single lens and a convex single lens with an air gap in order from the object side. The lens barrel of the first conversion lens, which is opened, is provided with a through hole in the portion forming the air gap in the direction orthogonal to the optical axis, and the conversion lens barrel
It is characterized in that the concave lens and the convex lens are retracted from the optical axis by rotating by °, and photographing with the intermediate focal length and the telephoto lens is possible through the through hole.

According to a third aspect of the present invention, in the variable power lens system according to the first aspect, the second conversion lens has a rotation center at about the middle of the entire length of the conversion lens. It is characterized by rotating and scaling.

According to a fourth aspect of the present invention, in the variable power lens system according to the first aspect, a part or all of the imaging lens is moved in the optical axis direction to enable focusing. And

According to a fifth aspect of the present invention, in the variable power lens system according to the fourth aspect, when the wide-angle lens is used, the focusing lens is fixed at a predetermined position and used as a fixed focus. It is characterized by

According to a sixth aspect of the present invention, in the variable power lens system according to the fourth aspect, the focusing for an object point at infinity in three modes of a wide-angle lens, an intermediate focal length and a telephoto lens. The feature is that the lens positions are common.

According to a seventh aspect of the present invention, in the real image type viewfinder including an objective lens having a positive refractive power as a whole, an optical system for erecting an inverted image, and an eyepiece in order from the object side. The objective lenses are, in order from the object side,
An almost afocal first conversion lens, a substantially afocal second conversion lens and an imaging lens having a positive refracting power as a whole, and an angular magnification of the first conversion lens. Is less than or equal to 1 and the angular magnification of the second conversion lens is less than or equal to 1, the magnification becomes low, the first conversion lens is retracted, and only the second conversion lens and the imaging lens are used. When it is configured as described above, it becomes an intermediate magnification, and further, in this state, the second conversion lens is inverted by 180 °, the angular magnification is made 1 or more to form a high magnification, and the finder magnification is switched in three stages. And

According to the eighth aspect of the present invention, in the variable magnification finder system according to the seventh aspect, the first conversion lens has a concave single lens and a convex single lens with an air gap in order from the object side. In the lens barrel of the first conversion lens which is opened, a through hole is provided in a portion forming the air gap in a direction orthogonal to the optical axis, and the conversion lens barrel is rotated by 90 °. Thus, the concave lens and the convex lens are retracted from the optical axis, and the visual field at intermediate magnification and high magnification can be seen through the through hole.

According to a ninth aspect of the present invention, in the variable power finder system according to the seventh aspect, the second conversion lens has a rotation center about 180 ° about the middle of the entire length of the conversion lens. It is characterized by rotating and scaling.

According to a tenth aspect, in the variable power finder system according to the seventh aspect, it is possible to correct a diopter change due to a distance change by moving a part or all of the imaging lens in the optical axis direction. It is characterized by having done.

The structure according to claim 11 is characterized in that, in the variable power viewfinder system according to claim 10, the diopter distance change correction lens is fixed at a predetermined position at least when the magnification is reduced. To do.

According to a twelfth aspect of the present invention, in the variable power finder system according to the tenth aspect, a distance change correction of the diopter with respect to an object point at infinity in three modes of low magnification, intermediate magnification and high magnification is corrected. The feature is that the lens positions are common.

In the variable power lens system according to the first aspect and the variable power finder system according to the seventh aspect, the first conversion lens is retracted. It is characterized in that the zoom ratio obtained by inverting each second conversion lens is larger than the zoom ratio obtained.

In the variable power lens system according to the first aspect and the variable power viewfinder system according to the seventh aspect, each of the first conversion lenses has a lens barrel. It is characterized in that it is held integrally with and can be rotated 90 ° at the same time.

In the variable power lens system according to the first aspect and the variable power viewfinder system according to the seventh aspect, each of the second conversion lenses has a lens barrel. It is characterized in that it is held integrally with and can be rotated 180 ° at the same time.

In the zoom lens system according to claim 4 and the zoom finder system according to claim 10, the zoom lens system according to the present invention has a focusing lens and a zoom lens. Correcting the distance change of the diopter of the viewfinder system By making the focal length of the lens almost the same and holding it integrally by the lens barrel, focusing of the variable power lens system and correction of the distance change of the diopter of the variable viewfinder system are performed. It is characterized by interlocking.

In the variable power lens and variable power finder according to the nineteenth and twentieth aspects, the focusing lens of the variable power lens system is formed by an autofocus system. It is characterized in that the diopter of the subject seen by the variable magnification finder is always kept substantially constant by automatically focusing.

According to a twenty-third aspect of the invention, in the variable power finder system according to the seventh aspect, the imaging lens has a fixed concave lens and a fixed convex lens arranged behind the diopter distance change correction lens. The focal length and the back focus of the imaging lens system are longer than those of the single lens for correcting dioptric distance change.

According to a twenty-fourth aspect of the present invention, in the variable power finder system according to the seventh aspect, the eyepiece lens comprises a convex lens and a concave lens from the object side, and the distance from the image plane of the objective lens to the convex lens of the eyepiece lens. Is longer than the focal length of the eyepiece.

According to a twenty-fifth aspect of the present invention, in the variable magnification finder system according to the seventh aspect, a poromilla system is arranged as an optical system for making an inverted image an erect image, and a part or all of the poromilla system is arranged. It is characterized by being a plastic mirror.

According to a twenty-sixth aspect of the present invention, in the variable power finder system of the twenty-fifth aspect, the plastic used for the mirror substrate is made of a transparent material.

[0034]

In order to achieve the object of the present invention, the following improving actions are obtained by the above respective constituents.

According to the structure described in claim 1, a mechanism for moving the lens in the optical axis direction for zooming is unnecessary,
Since only a mechanism for rotating or sliding the afocal system so that its optical axis coincides with the imaging lens, required accuracy is low, the mechanism can be simplified, and it is advantageous in cost reduction. Further, as can be seen from FIG. 1 showing an example, since the front lens diameter (r _3-1 surface) when the second conversion lens is set to have an angular magnification of 1 or less is smaller than the aperture diameter, The effective diameter of the first conversion lens arranged can also be made small, which is suitable for downsizing and parallax reduction.

According to a second aspect of the present invention, the first converter is provided.
By retracting the John lens from the optical axis, it is necessary to rotate it so that the light flux passes through the through hole of the lens barrel rather than sliding it vertically or horizontally while keeping the optical axis parallel. Can be made small.

According to the third aspect of the present invention, the second converter is provided.
This is to minimize the space required by the John lens, whichever the second conversion lens is facing,
The distance from the diaphragm can be minimized.

The structure according to claim 4 is the first converter.
If the John lens or the second conversion lens is provided with a focusing function, the mechanism cannot be simplified by a simple rotation mechanism. Therefore, the focusing function moves the imaging lens in the optical axis direction. By
The scaling function and the focusing function can be separated mechanically, and the mechanism can be simplified.

The fifth aspect of the present invention is effective for the purpose of avoiding unnecessary malfunction of the autofocus because the focal length of the present invention at the wide angle is short and the focal point is fixed.

According to the sixth aspect of the present invention, the maximum amount of movement required for the focus lens can be minimized, and after the power is turned on, the position of the focus lens is reset by the drive motor until the focus is reached. The time can be shortened and it is effective in increasing the focus speed. Also, when zooming from wide-angle to middle or from middle to telephoto, the autofocus starts to climb up the mountain from the infinity side, so there is little malfunction and there is the effect of speeding up focusing. Furthermore, in combination with the twelfth and the nineteenth and twentieth aspects, there is an effect that the viewfinder diopter for an object point at infinity is kept constant even if the magnification is changed. In other words, when you stop recording and turn off the power, be sure to return the focusing lens to the infinity position and stop it.If you turn the conversion lens by hand without turning on the power and change the magnification. Since the finder diopter for infinity is always constant, it is possible to perform zooming and check the finder image without consuming power.

According to a seventh aspect of the present invention, substantially the same configuration as that of the taking lens system of the first aspect is applied to a finder system to obtain the same purpose and substantially the same effect.

The structure described in claim 8 is to apply the substantially same structure as the taking lens system of claim 2 to the finder system to obtain the same purpose and substantially the same effect.

According to a ninth aspect of the present invention, the same configuration as that of the taking lens system of the third aspect is applied to a finder system to obtain the same purpose and substantially the same effect.

According to a tenth aspect of the present invention, the same configuration as that of the taking lens system of the fourth aspect is applied to a finder system,
It is for the same purpose and almost the same effect.

According to the eleventh aspect of the present invention, the same configuration as the taking lens system of the fifth aspect is applied to the finder system,
It is for the same purpose and almost the same effect.

According to a twelfth aspect of the present invention, the same configuration as the taking lens system of the sixth aspect is applied to a finder system,
It is for the same purpose and almost the same effect.

The structure described in claims 13 and 14 relates to the balance between the variable magnification ratio load and the aberration correction of the first conversion lens and the second conversion lens.
Of the aberrations generated by the conversion lens of No. 3, the chromatic aberration of magnification is the biggest problem, and correction becomes difficult if the zoom ratio is too large. Since the second conversion lens is used by reversing the concave lens group and the convex lens group, it is necessary to correct the aberrations of the respective lens groups independently, so that it is easy to cope with a large zoom ratio.

The structures described in claims 15, 16, 17, 18 and 19, 20 and 21, 22 simplify the mechanism when the variable lens system and variable finder system are linked. This is the most characteristic content of the present invention for reducing the cost by reducing the number of parts constituting the lens barrel, the interlocking mechanism is simple, and it is extremely advantageous as compared with the zoom lens.

According to the twenty-third aspect of the present invention, when the refractive power arrangement from the first conversion lens of the variable power finder system to the diopter distance change correction lens is the same as that of the variable power lens system, it is as it is. Then, the size of the image of the viewfinder objective lens is the same as that of the variable power lens system, but if the screen size of the image pickup device is small, the size of the field stop of the viewfinder is too small, which makes manufacturing difficult. Along with this, the magnification of the eyepiece must be increased, which makes it difficult to correct the aberration of the eyepiece. Therefore, a concave lens is arranged behind the diopter distance change correction lens to enlarge the image size of the viewfinder objective lens, and a convex lens is arranged as a field lens that bends the light beam toward the eyepiece lens. Is easy to manufacture, and the back focus is long to facilitate the placement of the poromilla system.

The structure described in claim 24 is for facilitating the disposition of the poromirror system, and the principal point of the eyepiece lens is brought to the front side to secure the distance from the field stop to the eyepiece lens.

According to the twenty-fifth aspect of the present invention, when the field stop is made large to make it difficult to cause an error due to displacement of the field stop, it becomes difficult to manufacture a plastic Porro prism corresponding to a large field stop. -Think the system. The Polo Mira system reflects up, down, left and right four times,
Even if the first reflection surface is placed in the long back focus of the viewfinder objective lens and placed in front of the field stop, if the parts precision is maintained sufficiently, the error of glare blurring is achieved within the allowable range without the adjustment mechanism. It is possible to If the remaining three surfaces are arranged between the field stop and the eyepiece, high precision is not required because it does not affect the glaring error. Considering that the finder barrel is made of plastic, at least the first reflecting surface is integrally molded by depositing a mirror on the plastic barrel, which facilitates accuracy.

According to a twenty-sixth aspect of the present invention, in the polo mirror system according to the twenty-fifth aspect, when the sunlight is incident from the eyepiece lens, the sunlight condensing on the field stop and the mirror surface close to the field stop. This is to prevent the plastic mirror from melting due to high temperature. The field stop may be made of metal, and if the plastic mirror has a high reflectance, it takes a long time to reach a high temperature, which is not a practical problem.
The mirror's substrate is black plastic, and the pin
If there is a light, sunlight will be absorbed by the mirror substrate and the temperature will rise to high temperature in a short time. Therefore, a transparent material is suitable for the mirror substrate.

By virtue of the effects of the respective constituents described above, it is possible to change the magnification by about 10 times including the super wide angle, the front lens diameter is small, the magnification changing mechanism can be simplified, and the manufacturing cost is low. A variable-power lens system can be realized, and similarly, by linking with the variable-power and focusing of this variable-power lens system, the parallax can be reduced, the mechanism can be simplified, and the manufacturing cost is low. Double finder system can be realized.

Unlike the zoom lens, there is no continuity of zooming, but general users who are unfamiliar with video cameras often take a lot of useless zooming scenes, often failing to make the reproduced image restless. However, according to the present invention, a stable scene can be taken with a fixed angle of view, and the angle of view can be instantly converted as needed, which may be rather easy for an unskilled general user to use.

Further, the optical viewfinder has a natural color and has no discomfort as compared with the black and white electronic viewfinder, and the optical viewfinder has a color.
It looks clearer than the liquid crystal viewfinder, and there is no discomfort, and the diopter is automatically corrected in conjunction with the autofocus of the zoom lens system. Forgetting both caching and zooming, you can concentrate on shooting and have the advantage that you can use it as if you were using a still camera.

[0056]

Embodiments of the present invention will be described below.

FIGS. 1, 2 and 3 are views showing the construction of an embodiment of the variable power lens system of the present invention, which is a wide-angle lens, respectively.
The intermediate focal length and the state of the telephoto lens are shown.

The structure of this embodiment will be described with reference to FIG. 1. The afocal first converter is formed by a plastic double-sided aspherical concave lens L1 and a convex lens L2 in order from the object side.
And a concave lens L3, a cemented concave lens L4 of a convex lens and a concave lens, a plastic aspherical convex lens L5, and a cemented convex lens L6 of a concave lens and a convex lens constitute an afocal second conversion lens system. Then, the diaphragm is arranged, and the convex lens L7 and the concave lens L8 are arranged.
And an aspherical convex lens L9 made of plastic to form an imaging lens system to form a wide-angle lens, and the first conversion lens system is rotated by 90 ° to obtain the state shown in FIG. Although not shown in the figure, it is possible to shoot through a through hole opened in the lens barrel of the first conversion lens, and to obtain an image with When the conversion lens system No. 2 is rotated by 180 ° and brought into the state of FIG. 3, it becomes a telephoto lens. In the figure, Q is a flat glass corresponding to a filter, K
Is an image plane (image forming position).

Next, Tables 1 to 3 show numerical examples of this embodiment.

[0060]

[Table 1]

In the above, r _{ij is the} radius of curvature of the j-th surface of the lens Li, d _{ij is} the j-th surface spacing of the lens Li, and n _ij is the refractive index of the j-th medium of the lens Li at the e-line n _e ν _ij. : Abbe number ν _e S _i of the j-th medium of the lens Li at the e-line: Surface spacing r _10-1 and _10-2 behind the i-th conversion lens The flat glass corresponding to a filter.

[0062]

[Table 2]

[0063]

[Table 3]

Definition of aspherical surface: The depth of the aspherical surface is represented by χ _i , and the height from the optical axis is represented by H.

[0065]

## EQU1 ## χ _i = H ² / r _i {1+ (1-H ² / r _i ² ) ^1/2 }
+ ΣA _j · H ^j diaphragm is in front of r _7-1 surface 3.5, diaphragm release diameter Φ =
8.96 r _3-1 Effective diameter of surface Φ = 5.38 FIGS. 4, 5 and 6 show spherical aberration, astigmatism and distortion of wide-angle lens, intermediate focal length and telephoto lens.

Next, FIG. 7, FIG. 8 and FIG. 9 are views showing the constitution of an embodiment of the variable magnification finder system of the present invention, showing the states of the wide-angle lens, the intermediate focal length and the telephoto lens, respectively.

The structure of the present embodiment will be described with reference to FIG. 7. The double-sided aspherical concave lens F1 made of plastic and the aspherical convex lens made of plastic F2 are used in the order from the object side.
The first aspherical conversion lens system is constituted, and the aspherical second conversion lens system is constituted by the plastic aspherical concave lens F3 and the cemented convex lens F4 of the concave lens and the convex lens. Is arranged, and the plastic aspherical convex lens F5 is made to have the same focal length as the imaging lens system of the variable power lens to perform diopter distance correction in conjunction with the imaging lens, and the concave lens F6 and the convex lens F7 are used for the objective lens. The focal length of the system is increased to enlarge the size of the field stop, and the image is erected with a Poromira system M as schematically shown in FIG. 10 to form a convex lens F8 as an eyepiece. It is configured so that it can be magnified and observed with the concave lens F9. 7 to 9, K indicates an image forming position. Further, in FIG. 10, L is a variable power lens system, F is a variable power viewfinder system, F5 is a diopter distance change correction lens, P is a fixed aperture,
1 is a first conversion lens, 2 is a second conversion lens, 3 is a through hole, 4 is a diaphragm device, 5 is a guide axis, 6 is an imaging lens driving device, 7 is an imaging lens, 8 is an image sensor, Reference numeral 9 is a field stop.

Numerical examples of this embodiment are shown in Tables 4 to 6.

[0069]

[Table 4]

In the above, r _{ij is the} radius of curvature of the j-th surface of the lens Fi, d _{ij is} the j-th surface spacing of the lens Fi, n _ij is the refractive index n _e ν _ij of the j-th medium of the lens Fi. : Abbe number ν _e S ₁ of the j-th medium of the lens Fi at the e-line: Surface spacing behind the first conversion lens S ₂ : Surface spacing behind the second conversion lens S ₃ : Visual The distance between the lenses behind the distance correction lens is shown.

[0071]

[Table 5]

[0072]

[Table 6]

The fixed aperture is 2.5 behind the r _4-3 plane, and the image formation position is behind the r _7-2 plane 15.465. A wide-angle lens, an intermediate focal length and a telephoto lens are shown in FIGS. 11, 12 and 13. Shows spherical aberration, astigmatism, and distortion at magnifications corresponding to.

[0074]

[Effects of the Invention] Due to the effects of the respective constituents described above,
Including ultra wide angle, variable magnification of about 10 times is possible, front lens diameter is small, variable magnification mechanism can be simplified, and manufacturing cost is low.
A focus variable power lens system can be realized, and similarly, the parallax can be reduced, the mechanism can be simplified, and the manufacturing cost is low, in conjunction with the variable power and focusing of this variable power lens system. A variable magnification finder system can be realized.

Unlike the zoom lens, there is no continuity of zooming, but it tends to occur to general users who are unfamiliar with video cameras.
According to the present invention, it is possible to take a stable scene with a fixed angle of view, and there is no need to worry about taking a lot of useless zooming scenes and failing to make the reproduced picture restless. Accordingly, the angle of view can be instantly converted, which may be rather easy for an inexperienced general user.

Further, the optical viewfinder has a natural color and has no discomfort compared to the black and white electronic viewfinder, and the optical viewfinder has a color
It looks clearer than the LCD finder, and there is no discomfort, and the diopter is automatically corrected in conjunction with the autofocus of the zoom lens system. -There is an advantage that you can concentrate on shooting without forgetting both caching and zooming, and use it as you would with a still camera.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a case where a variable power lens system of an embodiment of the present invention is a wide-angle lens.

FIG. 2 is a configuration diagram showing a case where the variable power lens system has an intermediate focal length.

FIG. 3 is a configuration diagram showing a case where the above-described variable power lens system serves as a telephoto lens.

4 (a), (b), and (c) are aberration curve diagrams of the wide-angle lens.

5 (a), (b), and (c) are aberration curve diagrams at the intermediate focal length.

6 (a), (b) and (c) are graphs showing aberration curves of the telephoto lens.

FIG. 7 is a configuration diagram showing a case where the variable power finder system of the embodiment of the present invention is a wide-angle lens.

FIG. 8 is a configuration diagram showing a case where the variable magnification finder system has an intermediate focal length.

FIG. 9 is a configuration diagram showing a case where the variable power finder system is a telephoto lens.

FIG. 10 is a schematic diagram showing the concept of the finder optical system.

11 (a), (b), and (c) are aberration curve diagrams of the finder system at a magnification corresponding to the wide-angle lens.

12 (a), (b) and (c) are aberration curve diagrams of the finder system at a magnification corresponding to the intermediate focal length.

13 (a), (b) and (c) are respective aberration curve diagrams of the finder system at a magnification corresponding to the above telephoto lens.

[Explanation of symbols]

 L ... Variable magnification lens system F ... Variable magnification viewfinder system 1 ... First conversion lens 2 ... Second conversion lens

Claims (26)

[Claims] 1. A variable lens comprising, in order from the object side, a substantially afocal first conversion lens, a substantially afocal second conversion lens, and an imaging lens having a positive refracting power as a whole. In the double lens system, when the angular magnification of the first conversion lens is set to 1 or less and the angular magnification of the second conversion lens is set to 1 or less, it becomes a wide-angle lens, and the first conversion lens is retracted. When the second conversion lens and the imaging lens are used alone, the focal length becomes an intermediate value. From this state, the second conversion lens is inverted by 180 °, and the angular magnification is set to 1 or more. A lens with a focal length of 3
A variable power lens system characterized by switching to stages. 2. The variable power lens system according to claim 1, wherein the first conversion lens is arranged in order from the object side.
An air gap is formed between the concave single lens and the convex single lens, and the lens barrel of the first conversion lens is provided with a through hole in the portion forming the air gap in the direction orthogonal to the optical axis.
It is characterized in that the concave lens and the convex lens are retracted from the optical axis by rotating the conversion lens barrel by 90 °, and the intermediate focal length and the telephoto lens can be photographed through the through hole. Variable magnification lens system. 3. The variable power lens system according to claim 1, wherein the second conversion lens has a rotation angle of 180 ° about the middle of the entire length of the conversion lens.
Variable magnification lens system characterized by rotating and varying magnification. 4. The variable power lens system according to claim 1, wherein a part or all of the imaging lens is moved in the optical axis direction to enable focusing. 5. The variable power lens system according to claim 4, wherein when the wide-angle lens is used, the focusing lens is fixed at a predetermined position and used as a fixed focus. Lens system. 6. The variable power lens system according to claim 4, comprising a wide-angle lens, an intermediate focal length and a telephoto lens.
A variable power lens system in which the position of the focusing lens with respect to an object point at infinity in the mode is made common. 7. A real image finder comprising an objective lens having a positive refracting power as a whole in order from the object side, an optical system for erecting an inverted image, and an eyepiece, wherein the objective lens is arranged from the object side. The first conversion lens is composed of a first afocal first conversion lens, a second afocal second conversion lens, and an imaging lens having a positive refracting power as a whole. When the angular magnification is set to 1 or less and the angular magnification of the second conversion lens is set to 1 or less, the magnification becomes low, and the first conversion lens is retracted to form an image with the second conversion lens. When only the lens is used, the intermediate magnification is obtained. From this state, the second conversion lens is inverted by 180 ° and the angular magnification is made 1 or more to achieve high magnification, and the finder magnification is increased. Zoom finder system characterized by switching the phase. 8. The variable magnification finder system according to claim 7, wherein the first conversion lens comprises a concave single lens and a convex single lens with an air gap therebetween in order from the object side. In the lens barrel of the conversion lens, a through hole is provided in a portion forming the air gap in a direction orthogonal to the optical axis, and the conversion lens barrel is rotated by 90 ° so that the concave lens and the convex lens are formed. Variable magnification finder system characterized by being retracted from the optical axis so that the field of view at intermediate and high magnifications can be seen through the through hole. 9. The variable magnification finder system according to claim 7, wherein the second conversion lens has a center of rotation of about 180 ° about the middle of the entire length of the conversion lens.
Variable magnification finder system characterized by rotating and varying the magnification. 10. The variable magnification finder system according to claim 7, wherein a part or all of the imaging lens is moved in the optical axis direction to enable correction of diopter change due to distance change. Variable magnification finder system. 11. The variable power finder system according to claim 10, wherein the diopter distance change correction lens is fixed at a predetermined position at least when the magnification is reduced. 12. The variable power finder system according to claim 10, wherein the diopter distance change correction lens positions are common with respect to an object point at infinity in three modes of low magnification, intermediate magnification and high magnification. Variable magnification finder system characterized by 13. The variable power lens system according to claim 1, wherein each second conversion lens is inverted based on a variable power ratio obtained by retracting each first conversion lens. A variable power lens system characterized in that the variable power ratio obtained is larger. 14. The variable magnification finder system according to claim 7, wherein the second conversion ratios are obtained from the variable power ratios obtained by retracting the respective first conversion lenses.
A variable power finder system characterized in that the variable power ratio obtained by inverting the John lens is made larger. 15. The variable power lens system according to claim 1, wherein the respective first conversion lenses are integrally held by a lens barrel so that they can be simultaneously rotated by 90 °. Variable magnification lens system. 16. The variable magnification finder system according to claim 7, wherein each of the first conversion lenses is integrally held by a lens barrel and can be simultaneously rotated by 90 °. Variable magnification finder system. 17. The variable power lens system according to claim 1, wherein the respective second conversion lenses are integrally held by a lens barrel so that they can be simultaneously rotated by 180 °. Variable magnification lens system. 18. The variable magnification finder system according to claim 7, wherein each of the second conversion lenses is integrally held by a lens barrel and can be simultaneously rotated by 180 °. Variable magnification finder system. 19. The variable power lens system according to claim 4, wherein the focusing lens of the variable power lens system and the diopter distance change correction lens of the variable power finder system have substantially the same focal length. A variable-magnification lens system characterized in that it is integrally held by a cylinder, and focusing of the variable-magnification lens system and correction of diopter distance change of the variable-magnification finder system are linked. 20. The zoom finder system according to claim 10, wherein the focusing lens of the zoom lens system and the diopter distance change correction lens of the zoom finder system have substantially the same focal length. A variable magnification finder system that is integrally held by a cylinder, and the focusing of the variable magnification lens system and the distance change correction of the diopter of the variable magnification finder system are linked. 21. The variable power lens system according to claim 19, wherein the focusing lens of the variable power lens system is automatically focused by an autofocus system to obtain a variable power. A variable-magnification lens system that keeps the diopter of the subject seen through the viewfinder almost constant. 22. The variable power finder system according to claim 20, wherein the focusing lens of the variable power lens system is turned on.
A zoom finder system characterized by keeping the diopter of the subject seen by the zoom finder almost always constant by automatically focusing with the tofocus system. 23. The variable power finder system according to claim 7, wherein the imaging lens has a fixed concave lens and a fixed convex lens behind the diopter distance change correction lens, and the focus of the imaging lens system. A variable magnification finder system characterized in that the distance and the back focus are made longer than the value of the single lens for correcting the distance change of diopter. 24. In the variable power finder system according to claim 7, the eyepiece lens is composed of a convex lens and a concave lens from the object side, and the distance from the image plane of the objective lens to the convex lens of the eyepiece lens is the focal length of the eyepiece lens. Variable magnification finder system characterized by being made longer. 25. The variable magnification finder system according to claim 7, wherein the optical system for converting an inverted image into an erected image is a poro mirror.
Variable magnification finder system characterized in that a system is arranged and a part or all of the polo mirror system is a plastic mirror. 26. The variable power finder system according to claim 25, wherein the plastic used for the mirror substrate is made of a transparent material.