JPH0442209A - Variable power finder and camera using the same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical real image variable magnification finder, which is used in electronic still cameras, video cameras, still cameras, and the like.

2. Description of the Related Art 2- to 3-times zoom lenses have come to be frequently used in popular still cameras, electronic still cameras, and video cameras that are small, lightweight, easy to use, and inexpensive.

As a result, there is a strong demand for an optical variable magnification viewfinder that is small, lightweight, inexpensive, easy to view, and consumes no power. Real-image variable magnification viewfinders have come into widespread use because they meet these demands and enable various types of information related to photography to be displayed within the viewfinder. As a real image variable magnification finder, a TTL method and a twin-lens method have been used so far. The TTL method, which extracts light from the imaging lens system, has the major feature of being free of parallax.
This has the disadvantage that the imaging optical system becomes large. On the other hand, although parallax occurs in the twin-lens system, it has the great advantage of being able to miniaturize the photographing and finder optical systems.

A conventional twin-lens type real image variable magnification finder is composed of an objective lens system having a variable magnification function, a field frame provided at its image formation position, an erecting system, and an eyepiece lens system. An example of a conventional variable magnification finder will be described below with reference to the drawings. (For example, application number Hei 1-19771
7) FIG. 2 shows a configuration diagram of a conventional variable magnification finder. In FIG. 2, 21.2223 are the first and second digits of the objective lens system, respectively. Second. In the third group, 24 is an erect Tachikawa relay lens system, and 25 is an eyepiece lens system.

Regarding the conventional variable magnification finder configured as above,
The operation will be explained below.

First, in the objective lens system, the first group 21 moves on the optical axis to correct diopter changes during zooming, and the second group 22 moves on the optical axis to cause a zooming effect. The third group 23, which is a fixed group, forms an inverted image 26 on the first imaging position. This inverted image 26 becomes an erect image 27 on the second imaging position by the relay lens system 24, and is enlarged by the eyepiece lens system 25.

Problems to be Solved by the Invention However, in the conventional variable magnification finder configured as described above, the first group 21 and the second group 22 are arranged in order to suppress the change in diopter when changing the magnification within a range that does not pose a practical problem. It is necessary to move on the optical axis while maintaining a certain relationship. For this,
The structure of the finder system has become complicated, and it has become smaller, lighter,
The problem was that it was not possible to achieve a low price.

The present invention provides a real image variable magnification finder that solves these problems.

Means for Solving the Problems In order to solve the above problems, the variable magnification finder of the present invention has an objective system that has an imaging function, an erecting system that converts an inverted image into an erected image, and an erecting system that converts an erected image into an erected image. and the objective system is composed of three or more groups, and further, one or more lens groups among these groups are fixed with respect to the erecting system and the eyepiece system. Furthermore, two or more lens groups sandwiching the above-mentioned fixed lens group are mechanically connected to move on the optical axis.

Operation The present invention solves the conventional problems with the above-described configuration. That is, with a simple structure in which two or more mechanically connected lens groups are moved as a whole in the optical axis direction with respect to a fixed lens group in the objective system, the deviation of the imaging position by the objective system, i.e. , the change in viewfinder diopter is minimized to the extent that it does not pose a practical problem.

Furthermore, by using the variable magnification finder of the present invention,
A small, lightweight, and low-cost camera can be realized.

EXAMPLE Hereinafter, a variable magnification finder according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration diagram of an embodiment of a variable magnification finder of the present invention. In Figure 1, 1 is the objective system, 2
is an erect system, and 3 is an eyepiece system. In particular, the objective system is composed of, in order from the object side, a first group 11 with positive refractive power, a second group 12 with negative refractive power, and a third group 13 with positive refractive power. The first group 11 and the third group 13 are mechanically connected and move in the same way during zooming, and the second group 12 is fixed with respect to the erecting system and the eyepiece system.

Next, specific numerical examples will be shown.

Group Focal length (mm) 1 18.693 2 -5.291 3 8.739 Principal point spacing (mm) Between 1st and 2nd groups Between 2nd and 3rd groups Wide-angle end
2.780 8.986 Telephoto end 7.4
05 4.361 At the wide-angle end where the first group 11 and third group 13 are closest to the eyepiece system 3, the focal length of the objective system l is 9.9
38M, the focal length at the telephoto end with the first group 11 and the third group 13 extended farthest to the object side is 25.943 mm.

The first group 11 and the third group 13 are connected, that is, the first group 11
When the distance between the third group 13 and the third group 13 is kept constant, the amount of focus movement occurring in the objective system 1 when the object point is 2 m is expressed as the third group 13.
As shown in the figure. In FIG. 3, the vertical axis represents the position of the moving group relative to the fixed group, and the horizontal axis represents the amount of focus movement. Moving group position 31
3 corresponds to the wide-angle end, and 32 corresponds to the telephoto end. From this figure, it can be seen that the maximum focus shift occurs at a position slightly closer to the wide-angle end from the telephoto end, and that the value is approximately 0.116 degrees.

The focal length of the conventionally used eyepiece system, or the combined focal length of the royal system and the eyepiece system, is about 20 mm. Therefore, the diopter change that occurs when the objective system shown in the example is used is about 0.29 diopters at most.

As is well known, a diopter change of about ±0.3 dayopter is absorbed by the human eye's adjustment ability. Therefore, the finder using the objective system of the above embodiment does not pose any practical problems.

In the above embodiment, numerical values were used to make the explanation easier to understand, but in other embodiments as well, by using the structure shown in Fig. 1 and the above-mentioned movement method, diopter changes can be achieved without causing any practical problems. It can be seen that it is possible to realize a real-image type finder that exists in Japan.

In addition to the embodiments described above, a variable finder can also be realized with an optical system in which a condensing system is provided between the objective system 1 and the erecting system 2, particularly near the imaging position of the objective system.

As the royal system 2, a relay lens system or a Porro prism can be used.

In the above embodiment, in order from the object side, the first group with positive refractive power,
An example of an objective system has been shown in which the second group has a negative refractive power and the third group has a positive refractive power, and the first group and the third group are connected and moved. In addition to this type, as shown in FIG. In the objective system composed of the fourth group 44, by connecting and moving the second group and the fourth group, an objective system with less focus movement can be realized.

FIG. 5 is a block diagram of an electronic still camera using a variable magnification finder according to the embodiment shown in -F.

In FIG. 5, 51 is a variable magnification finder 52 is a CCD
53 is a video floppy which is an image recording medium, 54 is a release button, 55 is a strobe, 56
is a photographing lens, and 57 is a battery.

In addition to electronic still cameras, the variable magnification finder of the second embodiment can be used in popular still cameras and video cameras.

As described above, by using the variable magnification finder of the above embodiment, it is possible to realize a small, lightweight, and inexpensive camera.

Effects of the Invention As is clear from the above explanation, the variable magnification finder of the present invention provides a small, lightweight, and low-cost zoom lens in which the diopter change during magnification is within a range that poses no practical problem, despite its simple structure. It is possible to realize a lens finder and a camera using it.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a variable magnification finder in the first embodiment of the present invention, FIG. 2 is a configuration diagram of a conventional finder, FIG. 3 is a characteristic diagram of the variable magnification finder in the first embodiment, and FIG. This figure is a block diagram of a variable magnification system according to the second embodiment, and FIG. 5 is a block diagram of an electronic still camera using a variable magnification finder according to the present invention. 1... Objective system, 2... Upright system, 3...
...eyepiece system. 5f--Kaika 7 I--9゛51-: fh Muneko) 53--It'Desf Ωzuji- 54-, -L lease Zf9!7 57-To the e-mail

Claims (2)

[Claims] (1) There are at least three objective systems in a variable magnification finder consisting of an objective system that has an image-forming function, an erecting system that converts an inverted image into an erected image, and an eyepiece system that magnifies the erected image. Consisting of the above groups, one or more lens groups are fixed relative to the erecting system and the eyepiece system, and two or more connected lens groups sandwiching the fixed lens group move on the optical axis. A variable magnification viewfinder that is characterized by: (2) A camera using the variable magnification finder according to claim (1).