JPH02301729A - Finder system with photometry means - Google Patents

Abstract

PURPOSE:To make the ratio of the photometric range of an object side to a photographic screen invariably constant by varying the photometric range of the object side subjected to photometry actually with a photometric system attending with the variable magnification in a photographing system. CONSTITUTION:In a finder system, luminous flux from the object is reflected with a half-mirror 3 by an objective 1 having a variable magnification means interlocking the variable magnification means of the photographing system and a 1st body image in the vicinity of a 1st field lens 4 is formed. Then a secondary image forming lens 7 forms a 2nd real erect image of the 1st body image in the vicinity of a 2nd field lens 7. Then the 2nd body image is observed through an ocular 10 and a photodetector 11 is arranged on the transmission side of the half-mirror 3 to receive a part of the luminous flux transmitted through the half-mirror 3. Consequently, photometry range of the object side is varied attending with the variable magnification by the variable magnification means of the objective 1. Consequently, the ratio of the area 5d of the photometry range to the area 5a of the photographing range photographing screen of the photographing system is made invariably constant throughout the variable magnification.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a finder system having a photometric means, and in particular to an external viewfinder system having a magnification variable means linked to a magnification variable means of a photographing system such as a photographic camera or a video camera. In the type finder system, the photometry range by the photometry means placed in a part of the finder system is made variable according to the zooming of the shooting system, so that the ratio of the photometry range to the shooting range (shooting screen) remains approximately constant during zooming. The present invention relates to a finder system having a photometric means.

(Prior Art) Conventionally, in external finder systems such as so-called lens shutter cameras in which the finder system is provided independently from the photographing system, if the photographing system has a variable magnification means, the finder system also has a variable magnification means. is provided, and the magnification is changed in conjunction with the magnification changing means of the photographing system.

This ensures that the photographic screen photographed on the photosensitive surface and the subject image observed in the viewfinder field coincide.

In addition, many lens shutter cameras are of the so-called external type, in which a photometry window 55 is provided in a part of the camera body 50 independently of the photographing system 51 and the finder system 52 to perform photometry on the subject side, as shown in FIG. A photometric device is used. Furthermore, the fifth
In the figure, 5:3° 54 is a window for automatic focus detection, and 56 is a strobe light emitting surface.

In the camera shown in the figure, even if the photographing system changes the magnification and changes the size of the subject image formed on the photosensitive surface, with an external photometer, the metering range on the subject side does not change and remains constant. .

(Problems to be Solved by the Invention) In an external photometry device, the photometry range on the subject side is always constant, whereas the shooting range by the shooting system changes in various ways due to zooming.

That is, the external photometer has a problem in that the ratio of the photometric range of the subject to the photographic range of the subject photographed on the photosensitive surface by the photographing system varies depending on the magnification.

For example, as shown in FIG. 3, when the shooting system is at the wide-angle end, the photometry range for the shooting range area 5a is area 5c;
At the telephoto end, the photometry range becomes area 5b.

If the shooting system has a variable magnification means in this way, the ratio of the metering range to the shooting range of an external photometer will change due to the variable magnification, for example, the screen center center of gravity metering method will change to the screen average metering method. There were problems such as changes.

Furthermore, there is a problem in that the photometric range observed within the field of view of the finder changes as the subject distance changes, resulting in so-called parallax.

For example, as shown in Figure 4, the photometry range when observing an object at infinity with a finder system is an area of 5cl.
The photometry range when observing a close object is area 5c2
Therefore, there is a problem in that it is not possible to accurately measure the light of the subject area that is actually being observed.

The present invention changes the photometry range on the subject side that is actually measured by the photometry system in an external viewfinder system having a variable magnification means, and measures the photometry for both sides of the photographed object observed in the viewfinder field of view. 1] An object of the present invention is to provide a finder system having a photometric means so that the ratio of the range is always constant.

(Means for Solving the Problems) The finder system having the photometry means of the present invention is an external finder system provided independently from the photographing system, and the finder system is a variable magnification means of the photographing system. After the light beam from the subject is reflected by a half mirror by an objective lens having a variable magnification means linked to the lens, a first object image is formed near the first field lens, and a secondary imaging lens is used to form a first object image from the first object image. A second object image of an erect normal image is formed near the second field lens, and the second object image is observed with an eyepiece, and a light receiving element is arranged on the transmission side of the half mirror, and the second object image is observed through the half mirror. It is characterized in that by receiving a portion of the luminous flux, the photometry range on the subject side is made variable as the magnification changing means of the objective lens changes magnification.

(Example) FIG. 1 is a schematic diagram of the main parts of the optical system of the finder system of the present invention.

This embodiment shows a real-image type finder system having a magnification variable means of a secondary imaging type.

Reference numeral 1 denotes an objective lens which transmits a first object image regarding the subject through a half mirror 3 to a first field lens 4 near the first field lens 4.
It is formed on the focus surface 5.

Reference numeral 7 designates a secondary imaging lens which converts a second object image, which is an erect image, from a first object image formed at a first focus 5 by an objective lens 1 through a mirror 6 to a second object image near a second field lens 8. It is formed on the focus surface 9. Reference numeral 10 denotes an eyepiece lens for observing a second object image formed at a second focal point 9. Reference numeral 11 denotes a light receiving element, which is arranged at a position optically equivalent to the first focus point 5 on the transmission side of the half mirror 3, and receives the light that has passed through the half mirror 3 and measures the light of a specific area on the subject side. There is.

In this embodiment, a photometric system is constructed by a finder-based objective lens l and a light receiving element 11, thereby simplifying the entire apparatus.

The objective lens l includes a negative lens 1a and a positive second lens 1b.
It has two lens groups: the second lens lb is moved toward the object side to change the magnification, and the image plane fluctuation caused by the change in magnification is corrected by moving the second lens 1a non-linearly toward the object side. This allows zooming from the wide-angle end to the telephoto end.

The first field lens 4 converts the light flux from the objective lens 1 into 2
The light is focused near the entrance pupil of the next imaging lens 7.

The second field lens 8 focuses the light beam from the secondary imaging lens 7 near the eye point position behind the eyepiece lens 10.

The half mirror 3 folds the finder optical path together with the mirror 6 in order to shorten the overall depth of the finder system, and at the same time guides a portion of the light beam from the objective lens 1 to the photometry system.

In this embodiment, the magnification of the objective lens l of the finder system is changed in conjunction with the magnification changing operation of the photographing system (not shown). Further, the light receiving element 11 is arranged via the half mirror 3 at a position optically equivalent to the first focal plane 5 formed by the objective lens l.

Thereby, the photometry range on the subject side that is photometered by the light receiving element 11 is changed in accordance with the magnification change of the objective lens 1.

That is, as shown in FIG. 2, the ratio of the area 5d of the photometry range to the area 5a of the shooting range (photographing screen) by the shooting system is made to be constant within the range of magnification.

This allows the bow to measure light without parallax.

It also prevents the photometry range for the photographic screen observed within the viewfinder field of view from shifting laterally due to changes in subject distance, so that the correct photometry range without parallax can be observed.

(Effects of the Invention) According to the present invention, by configuring each element of the finder system as described above, the ratio of the metering range to the shooting screen is always constant at any zoom position during zooming, and the subject distance does not change. However, it is possible to achieve a finder system having a photometry means that can observe a correct photometry range without parallax in the photometry range within the viewfinder field of view.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the main parts of the finder system of the present invention. Fig. 2 is an explanatory diagram of the viewfinder field of view observed with the finder thread of the present invention, Figs. 3 and 4 are explanatory diagrams showing the photometry range that changes due to zooming in a conventional external finder system, and Fig. 5 is an explanatory diagram of the viewfinder field observed with the finder thread of the present invention. 1 is an external view of a conventional lens shutter camera. In the figure, 1 is an objective lens, 3 is a half mirror, 14 is a first field lens, 5 is a first focal plane, 6 is a mirror, and 7 is a 2
8 is a second field lens, 9 is a second focusing surface, 10 is an eyepiece lens, 11 is a light receiving element, 5a is a photographic screen, and 5b, 5c, and 5d are photometry ranges.

Claims (1)

[Claims] (1) An external finder system that is installed independently of the photographing system, and the finder system converts the light beam from the subject into a half mirror using an objective lens that has a variable magnification means that works with the variable magnification means of the photographic system. forming a first object image near the first field lens, forming a second object image that is erect from the first object image near the second field lens using a secondary imaging lens; The second object image is observed through an eyepiece, and a light receiving element is disposed on the transmission side of the half mirror to receive a part of the light beam that has passed through the half mirror, thereby changing the magnification of the objective lens by the variable magnification means. A finder system having a photometering means that is characterized in that the photometering range on the subject side is variable as the magnification increases.