JPH01309033A - Variable power finder optical system - Google Patents

Abstract

PURPOSE:To vary the size of in-finder information in a camera wherein a light measurement system is not used in common to a photographic lens or finder optical system according to the power variation of the finder optical system by varying the power of a relay lens optical system which re-forms an image formed by an objective. CONSTITUTION:This optical system has the objective 11, a light measurement area mark 12 arranged in the focal plane of the objective, the relay lens optical system 13 which inverts an inverted image formed by the objective into an erect image, a visual field frame 14 arranged in the focal plane of the relay lens optical system, and an ocular 15, and the power of the relay lens optical system 13 is varied to vary the size of the light measurement area mark 12. The light measurement area mark 12 is therefore varied in size by the relay lens optical system 13 together with a subject image which is formed by the objective 11. Consequently, the light measurement area mark indicates the same range of an object regardless of the power variation of the finder optical system.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a variable magnification finder optical system capable of changing the size of information in the finder as the finder optical system changes magnification. The present invention relates to a variable magnification finder optical system for a variable magnification camera that performs photometry and distance measurement of a subject without passing through a photographic lens or finder optical system.

Conventional single-lens reflex cameras use the so-called TTL method, which performs photometry and distance measurement through the photographic lens, so even if you change the magnification of the photographic lens, the photometry or distance measurement area mark ( information in the viewfinder) always corresponds to the actual photometry range or distance measurement range. Therefore, there is no need to change the size of the information in the finder regarding photometry and distance measurement as the photographic lens changes its magnification.

On the other hand, the photometry (distance measurement) system of a camera whose photometry (distance measurement) system is not shared with the taking lens or finder optical system is
Figure 4 shows the distance measurement range and the actual shooting range. In the figure, (1) is the subject, (2) is the photographic lens with variable magnification, (3) is the imaging surface (film surface), (4) is the photometry (distance measurement) lens fixed to the camera, and (5) is the photographic lens that can be photographed. ) is photometric (
This is the light-receiving surface on which the distance measuring (distance-measuring) element is placed.

In the state shown in FIG. 4 (I), the focal length of the photographic lens (2) is ".
(1a) is imaged. The range of the subject (1) that the light-receiving surface (5) looks at through the photometric (distance-measuring) lens (4) is (1b), and among the images formed on the imaging surface (3), (
This means that photometry (distance measurement) is being performed in the range shown in 3b).

The state shown in FIG. 4 (II) is a state in which the focal length of the photographic lens (2) is set to f' by changing the magnification using the photographic lens (2). The photographing magnification increases by changing the magnification of the photographing lens (2), and the image of (I) of the subject (1) appears on the imaging surface (3).
Only the range of C) is imaged more enlarged than the state of (I).

In addition, since the photometry (distance measurement) lens (4) is fixed to the camera, the range (1b) of the subject that Eiko J, C5> looks at is independent of the magnification change of the photographic lens (2) (I ), but the photometry (distance measurement) range (1b) is expanded to (3b') and imaged on the imaging surface (3). Therefore, there is no problem with a finder optical system that forms a finder image at a constant magnification regardless of the magnification of the photographic lens (2), but if the finder optical system also changes magnification along with the magnification of the photographic lens (2), the photometry It is also necessary to change the thickness of the information in the viewfinder of the photometry (distance measurement) area mark that indicates the (distance measurement) range.

However, there is no known finder optical system that changes the size of the information in the finder as the finder optical system changes the magnification, and the information in the finder related to photometry (distance measurement) of the conventional variable magnification finder optical system. had the following structure.

1 Display only the photometry (distance measurement) range on either the wide-angle side or the telephoto side.

2 Displays both the wide-angle and telephoto metering (distance) ranges at the same time.

3. The LCD display uses a hologram or the like to selectively display the photometry (distance measurement) range on the wide-angle or telephoto side.

The display of information in the viewfinder with the above configuration has two focal points (
Even if a camera having a focal length of only a plurality of points is effective, it is difficult to adequately cope with a camera that continuously changes magnification. Note that in the case where photometry (distance measurement) is performed through the finder optical system, there is no need to change the size of the information in the finder.

Furthermore, the conventional method for changing the magnification of the finder optical system has been to change the magnification of an objective lens (including one that is also used as a photographic lens). It is also known that a relay lens optical system is used as an inverting optical system that returns an inverted image formed by an objective lens to an erect image, but it is also known that a relay lens optical system is used to change the magnification of a finder optical system. What exists previously did not exist.

Problems to be Solved by the Invention The purpose of the present invention is to reduce the size of information in the finder such as the photometry (distance measurement) area mark in a camera where the photometry (distance measurement) system is not shared with the photographing lens or the viewfinder optical system. It is an object of the present invention to provide a variable magnification finder optical system that can be changed as the magnification of the finder optical system changes.

Means for Solving the Problems Accordingly, the variable magnification finder optical system of the present invention focuses on a relay lens optical system that obtains an erect image by re-forming an image formed by an objective lens, and uses a relay lens optical system. The above objective is achieved by changing the magnification of the system.

In other words, in a variable magnification finder optical system used in a camera that performs photometry or distance measurement without passing through the photographing lens or finder optical system, the objective lens is placed in order from the object side, and the photometering or distance measurement device located on the focal plane of the objective lens - A photometry or distance measurement area mark that indicates the distance measurement range, a relay lens optical system that returns an inverted image formed by the objective lens to an erect image, a field frame placed on the focal plane of the relay lens optical system, and an eyepiece. and a lens, and the size of the subject image and photometry or distance measurement area mark is changed by changing the magnification of the relay lens optical system.

Operation With the above configuration, the photometry (distance measurement) area mark is magnified by the relay lens optical system together with the subject image formed by the objective lens. Therefore, regardless of the magnification of the finder optical system, the photometry (distance measurement) area mark always indicates the same range of the subject.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of a variable magnification finder optical system showing an embodiment of the present invention. The object light that has passed through the objective lens (11) has an objective lens (11) for the finder optical system in addition to the photographic lens, and is directed to the first focal plane (12).
The image is formed as an inverted image. The inverted image of the subject formed on the first focal plane (12) is returned to an erect image by the relay lens (13) and re-imaged on the second focal plane (14). The eyepiece lens (15) magnifies the subject image re-focused on the second focal plane (14).

On the first focal plane (12), there is a glass plate or 7
- etc. are arranged. Furthermore, a field frame forming a finder field of view is arranged on the second focal plane (15). In this way, a glass plate or the like on which a photometry (distance measurement) area mark is drawn on the first focal plane (12) is placed on the second focal plane (15).
), the photometry (distance measurement) area mark and field frame can be seen on the same plane as the subject image within the viewfinder screen, making it possible to obtain a clear viewfinder image. .

In addition, in Figure 1, the objective lens (11), relay lens (13), and eyepiece lens (15) are all shown as one lens, but in reality each is composed of a plurality of lens systems. Needless to say.

Now, the distance between the first focal plane (12) and the front principal point of the relay lens (13) is A, and the distance from the rear principal point of the relay lens (13) to the second focal plane (12) is B. In this case, the relay lens (13) is A;B=a;b and A:B=b
: By shifting to a, bird β1==b/a and β, 2=
Two types of scaling, a/b, are achieved. Relay lens (1
When changing the magnification of 3) continuously, the lens may be moved symmetrically in the left-right direction with the same magnification between the above-mentioned magnifications β1 and β2. In other words, by fully changing the magnification of the relay lens (13), the image on the second focal plane (14) of the photometry (distance measurement) area mark placed on the first focal plane (12) changes in magnification along with the subject image. be done. difference, second focal plane (
14) The size of the finder screen magnified by the eyepiece (15) due to the upper field frame is always constant regardless of the magnification change of the relay lens (13).

Therefore, the viewfinder screen seen through the eyepiece (15) looks like the one shown in FIG. In Figure 2, (21)
is the field of view frame, (22) is the photometry (distance measurement) area mark when the relay lens (13) is on the wide-angle side, and (23) is the photometry (distance measurement) when the relay lens (13) is on the telephoto side.
It is an area mark. When the relay lens (13) continuously changes magnification, the photometry (distance measurement) area mark changes continuously within the range shown in (22) to (23).

As explained in the prior art section with reference to Fig. 4, in cameras where the photometry (distance measurement) system is not shared with the photographic lens or the finder optical system, the difference in relation to the photographic screen occurs as the photographic lens changes magnification. The relative size of the photometry (distance measurement) range changes. Therefore, even in a variable magnification finder optical system that changes the magnification of the finder optical system as the photographic lens changes its magnification, the relative size of the photometry (distance measurement) range with respect to the finder screen changes.

In the above embodiment of the present invention, the objective lens (11) always focuses an inverted subject image at a constant magnification on the first focal plane (12) regardless of the magnification change state of the finder optical system. Therefore, by arranging the photometry (distance measurement) area mark on the first focal plane (12), the photometry (distance measurement) area mark always indicates a specific range of the subject image. The role of the relay lens (13) is to invert the inverted subject image formed on the first focal plane (12) and return it to an upright image.
The purpose of this inverted subject image is to change the magnification and re-image it on the second focal plane (14), so the photometry (distance measurement) area mark is magnified at the same magnification as that of the subject image. The image is formed on the focal plane (14).

This situation is shown in FIG. (I) is wide-angle state, (II)
is in telephoto mode. When the photometry (distance measurement) system is fixed to the camera body, the photometry (distance measurement) range is always a fixed range within the subject, so even if the shooting lens and finder optical system are changed in magnification, This means that the photometry (distance measurement) range is always properly displayed in the viewfinder image.

In addition, to prevent the subject from becoming vignetted and to prevent the amount of light from decreasing in the surrounding areas, condenser lenses are installed near the first focal plane (12) and second focal plane (14) of the finder optical system. It is also possible to place

In addition, in a variable magnification viewfinder optical system using a relay lens (13), the information displayed in the viewfinder drawn on the glass plate, etc. located at the focal plane (12) is limited to only the photometry (distance measurement) area mark. Rather, any type of lens whose size changes along with the subject image as the finder optical system changes magnification is possible.

Effects of the Invention As explained in detail above, in the variable magnification finder optical system of the present invention, a photometry (distance measurement) area mark is arranged on the focal plane of the objective lens, and magnification is changed by the relay lens optical system. Therefore, when the finder optical system is magnified, the photometry (distance measurement) area mark is also magnified together with the subject image, and the photometry (distance measurement) area mark can always indicate a specific range of the subject image.

Therefore, even when performing photometry (distance measurement) using the photometry (distance measurement) system fixed to the camera without passing through the photographic lens or finder optical system, the photometry (distance measurement) always covers a certain subject range within the viewfinder screen. It becomes possible to show it as a range.

In addition, the variable magnification finder optical system of the present invention uses a 1-lou lens optical system as an inversion optical system, and the photometry (distance measurement) area mark is placed on the focal plane of the objective lens, and the field frame is placed on the focal plane of the relay lens optical system. Since the real-image type finder optical system is arranged respectively, it is possible to clearly see the subject image, photometry (distance measurement) area mark, and field frame.

[Brief explanation of the drawing]

Fig. 1 is an exploded view of a variable magnification finder optical system showing an embodiment of the present invention, Fig. 2 is an internal view of the finder screen showing the finder screen by the variable magnification finder optical system of the present invention,
FIG. 3 is a view inside the finder showing the photometry or distance measurement range when changing the magnification using the variable magnification finder optical system of the present invention;
FIG. 4 is a diagram showing the relationship between the photometry or distance measurement range and the actual shooting range of a camera that performs photometry or distance measurement without passing through the photographic lens or finder optical system. (11)... Objective lens, (13)... Relay lens optical system, (15) - Eyepiece lens. Applicant Minolta Camera Co., Ltd. M1 Figure 2 Figure 4 Figure 5゜

Claims (1)

[Scope of Claims] 1. In a variable magnification finder optical system used in a camera that performs photometry or distance measurement without passing through a photographic lens or finder optical system, in order from the object side, an objective lens, and a focal plane of the objective lens. A photometry or distance measurement area mark is placed on the focal plane of the relay lens optical system to return the inverted image formed by the objective lens to an erect image. 1. A variable magnification finder optical system comprising a field frame and an eyepiece, and changing the magnification of a subject image and the size of a photometry or distance measurement area mark by changing the magnification of a relay lens optical system.