JPS6142621A - Ttl photometric device of single-lens reflex camera - Google Patents

Abstract

PURPOSE:To make the linearity of a photometric output excellent, to make the photometric characteristic uniform and excellent, and also to meter efficiently a light of an object, by constituting a sub-mirror by combining two kinds or more of concentrical ring band-shaped reflecting mirrors having each different reflection characteristic. CONSTITUTION:The greater part of light passing through a photographic lens 1 is led to a finder system 3, and the balance passes through a semipermeable part of a main mirror and forms an image of an object on a sub-mirror 4, and reflected by the sub- mirror 4 and led to a photodetecting system. A photodetecting lens 5 is placed so that the image of the object on the sub-mirror 4 is formed on a photodetector 6. This sub- mirror 4 is constituted by forming two kinds of Fresnel reflecting mirrors having each different reflection characteristic on the same surface, and its minute part P consists of each part PA, PB of the ring band surface set to two kinds of different angles. In a luminous flux 11 of the photodetecting lens 5, a luminous flux 11a which is made incident on the upper part PA of the minute part P is reflected to the direcion of the upper part of an exit pupil of the photographic lens 1, and the lower part PB of the minute part P is reflected to the direction of the lower part of the exit pupil of the photographic lens 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a TTL photometry device for a single-lens reflex camera, and in particular to a main mirror for a finder having a semi-transparent section and a method for measuring light for photometry that has passed through the semi-transmission section. The present invention relates to a TTL photometry device equipped with a sub-mirror that leads to a light receiving system.

(Background of the invention) In a TTL photometry device, the light incident from the photographing lens is divided into two parts: one is sent to the finder system by the main mirror, and the other is the light that passes through the semi-transparent part of the main mirror, is reflected by the sub-mirror, and is sent to the light receiving system. divided into Most of the light incident from this photographic lens is sent to the finder system, and normally only a small amount of light is sent to the light receiving system. For that reason,
In such a photometric device, it is necessary for the submirror to efficiently guide the light that has passed through the semi-transparent portion of the main mirror to the light receiving system.

Furthermore, in order to obtain linearity of the photometric output, it is desirable that the sub-mirror has a reflection characteristic that allows the output of the light-receiving element to be proportional to the aperture size of the aperture of the photographic lens.
A photometric device with improved photometric characteristics was developed in 1983.
This is proposed in Japanese Patent No. 16576. The sub-mirror of this photometric device is composed of a central reflective area where a plurality of microscopic reflective surfaces with specific reflective properties are gathered near the center, and a reflective area where a microscopic reflective surface with light condensing properties is assembled around the center. This photometric device has good linearity of photometric output with respect to the aperture. However, there are multiple photometry methods, and especially when performing multi-segment photometry, in this photometer, the photometry information at the center of the screen is obtained from the light reflected from the center of the sub-mirror, and the photometry information at the surrounding area is Since information is obtained from the light reflected from the periphery of the sub-mirror, the reflection characteristics are different between the center and periphery of the sub-mirror, so the problem is that the photometry characteristics are different between the center and periphery of the screen, making it impossible to perform proper photometry. There is a point.

Another method for efficiently guiding the light from the photographic lens to the light receiving system is to use a Fresnel reflector with condensing properties as a submirror. This shows the reflection characteristics.

Here, in order to simplify the explanation, the traveling direction of light is assumed to be from the light receiving lens 5 to the exit pupil of the photographing lens 1.

In FIG. 9, the light flux of the light-receiving lens 5 directed toward the point Q at the center of the sub-mirror 41 is indicated by a light flux 22, and the light flux of the light-receiving lens 5 directed toward a point Q' at the upper part of the sub-mirror 41 is indicated by a light flux 22'. As shown in the figure, the conventional Fresnel reflecting mirror reliably reflects the light beam from the light receiving lens 5 in the direction of the exit pupil of the photographing lens 1. However, since the opening angle of the light beam guided to the light-receiving element 6 of the conventional sub-mirror 41 is determined by the size of the light-receiving lens 5, only light near the center of the exit pupil of the photographing lens 1 is photometered. FIG. 10 shows a projection of the area where the light-receiving lens 5 receives light onto the exit pupil on the photographing lens 1 when the conventional sub-mirror 41 is used. becomes. As shown in Fig. 9, the light-receiving lens 5 cannot normally be made very large, so
The area 23 to be photometered is much smaller than the exit pupil size of the photographic lens 1. Therefore, in stop-down photometry, etc., the aperture of the aperture of the photographic lens 1 is the area 2 to be photometered.
There was a drawback that the photometric output did not change at all until the aperture was narrowed down to a size of 3, that is, the linearity of the photometric output was poor up to the aperture. Additionally, if a brighter lens is used as the standard for photometry and a darker interchangeable lens is attached to the camera, overexposure may occur.

(Objective of the Invention) The present invention solves these drawbacks, has good linearity of photometric output, has uniform and good photometric characteristics no matter which part of the photographic screen is taken, and efficiently uses subject light. An object of the present invention is to provide a TTL photometry device that measures light well.

(Summary of the Invention) Technical points of the present invention are: - In a TTL Fuchi optical device for an eye reflex camera, the submirror is composed of a combination of two or more types of concentric annular reflecting mirrors having mutually different reflection characteristics. It is said that

(Example) FIGS. 1 to 8 show an example of the present invention. T in Figure 5
In the optical path diagram of the TL photometer, the light that has passed through the photographing lens 1 is guided to the finder system 3 by the main mirror, and the light is guided to the light receiving system (light receiving lens 5, light receiving element 6) by the submirror.
) and the light guided by it. Most of the light that has passed through this photographic lens l is guided to the finder system 3, and the rest passes through the semi-transparent part of the main mirror to form a subject image on the sub-mirror 4, and then is reflected by the sub-mirror 4 and received. guided by the system. The light-receiving lens 5 is arranged so as to form an image of the subject on the sub-mirror 4 onto the light-receiving element 6. This light receiving element 6 has five segments 6 as shown in FIG.
It is divided into 1 to 65, and multi-division photometry is performed. In addition,
In order to correctly form a subject image on the sub-mirror 4, the sub-mirror -4 should be placed at the same position as the film plane 7, but usually it is located in front of the film plane 7 due to spatial constraints. In this case, the subject image will be blurred to some extent, but the division of the screen is not so fine as shown in FIG.
5, there is a separation band section 66 with no light-receiving sensitivity, so there is little influence on photometry.

FIG. 1 shows an enlarged view of the sub-mirror 4 in FIG. 5. In FIG. 1, the sub-mirror 4 is composed of a ring-shaped reflecting mirror as shown in FIG. 1, but it is different from a conventional Fresnel reflecting mirror. The structure is equivalent to two types of Fresnel reflecting mirrors having different shapes and different reflection characteristics formed on the same surface, and will be explained in detail in FIG. 3. FIG. 2 shows the reflection characteristics of the submirror 4 shown in FIG. 1. Note that for the sake of simplicity, the traveling direction of the light is assumed to be from the light-receiving lens 5 to the exit pupil of the photographing lens 1. A light beam 11 from the light-receiving lens 5 that is incident on the minute portion P at the center of the sub-mirror 4 is reflected in the direction of the photographing lens 1 . At this time, the minute portion P has a characteristic of dividing the light beam 11 of the light-receiving lens 5 into two directions: a light beam 11A directed toward the upper part of the exit pupil of the photographing lens 1, and a light beam 11B directed toward the lower part.

Further, other parts of the sub-mirror 4, such as the upper minute part P', are also configured to have a ring-shaped reflecting mirror having similar reflection characteristics. Therefore, the submirror 4 has the above-mentioned reflection characteristics over its entire surface.

FIG. 3 shows an enlarged cross-sectional view of a part of the annular reflecting mirror shown in FIG. 1, and explains the effect of the minute portion P dividing the light beam 11 of the light-receiving lens 5 into two directions. This minute portion P consists of portions PA and PB of the annular surface set at two different angles. A minute portion P of the light beam 11 of the light receiving lens 5 in FIG.
A light beam 11a incident on the upper part PA of the photographic lens 1 is reflected toward the upper part of the exit pupil of the photographic lens 1, and a lower part PB of the minute portion P is reflected toward the lower part of the exit pupil of the photographic lens 1.

FIG. 4 shows how the light beams 11a and 11b of the light receiving lens 5 reflected by the minute portions PA and PB are projected onto the exit pupil of the photographing lens 1.

In FIG. 4, the shaded area represents the entrance pupil of the light-receiving lens 5 projected onto the exit pupil of the photographic lens 1. Furthermore, when looking at the entire annular zone including the minute portion P, this annular zone guides the light from the light receiving system to the entire surface of the exit pupil. This indicates that the part of the light incident on the photographic lens 1 surrounded by diagonal lines, that is, the part on which the entrance pupil of the light receiving lens 5 is projected so as to surround the exit pupil, is received and used for photometry. ing. In this way, the annular Fresnel reflector used in the sub-mirror 4 divides the entrance pupil of the light-receiving lens 5 into two and projects it onto the exit pupil of the photographic lens 1, so that the exit pupil of the photographic lens 1 is wider. Guides part of the light to the light receiving system. Therefore, a photometric output corresponding to the size of the aperture of the aperture can be obtained immediately from the maximum aperture of the photographic lens 1. Further, since such reflection characteristics can be obtained uniformly over the entire surface of the sub-mirror 4, it is particularly effective in a photometry device that requires uniform photometry characteristics for each divided screen, such as multi-segment photometry.

7 and 8 illustrate a method of setting the shape of the annular reflecting mirror of the sub-mirror 4. FIG. In FIG. 7, a light-receiving lens 5' and its center point R' are assumed to be located at a position symmetrical to the center point R of the entrance pupil of the light-receiving lens 5 with the plane included in the sub-mirror 4 as a boundary.

A lens 4' having the function of focusing light emitted from the center point S of the exit pupil of the photographing lens 1 onto the center point R' is assumed to be located at the sub-mirror 4. If a Fresnel reflector equivalent to this lens 4' is placed at the position of the submirror 4, the light exiting from the center point S of the exit pupil of the photographing lens 1 will be condensed at the center point R of the entrance pupil of the light receiving lens 5. Become. This lens 4
A Fresnel reflecting mirror equivalent to ' is located within the plane of the submirror 4, and has an optical axis l passing through the intersection T of the straight line connecting the center point S and R' with the plane. Therefore, this Fresnel reflecting mirror is composed of concentric ring-shaped reflecting surfaces centered on the intersection T. The cross-section of this Fresnel reflector is shown by the dotted line in FIG. 8, and the Fresnel reflector shown by the dotted line formed concentrically around the intersection T4 in FIG. The reflector on the annular zone of the embodiment is formed by providing a predetermined angle to the annular zone shown by the dotted line so as to have the shape shown by the solid line.

In this embodiment, the submirror 4 is composed of a combination of annular reflecting mirrors having two different reflection characteristics.
It can be changed as appropriate. For example, if the ridge of the ring of the Fresnel reflector shown by the solid line in Fig. 8 is slightly shaved parallel to the dotted line, it will become a ring-shaped reflector with three types of reflection characteristics. It may also be a combination of annular reflecting mirrors having reflective characteristics. The shape of the annular zone of this reflecting mirror may be determined depending on the configuration of the photographing lens 1 and the light receiving lens 5 and the required photometric characteristics. Further, the sub-mirror 4 which is a combination of such annular reflecting mirrors has the advantage that the manufacturing method of a conventional Fresnel reflecting mirror can be used as is.

(Effects of the Invention) As described above, according to the present invention, the submirror is constructed by combining two or more types of concentric annular reflecting mirrors having mutually different reflection characteristics. Since the linearity of the photometric output can be improved and the photometric characteristics can be uniformly obtained over the entire surface of the screen, any photometric method is effective.

[Brief explanation of the drawing]

Figures 1 to 8 show a preferred embodiment of the present invention;
The figure is a front view of the submirror, FIG. 2 is an explanatory diagram showing the reflection characteristics of the submirror, FIG. 3 is an enlarged view of FIG. 5 is a layout diagram of the optical system and light receiving system inside the body of a single-lens reflex camera, FIG. 6 is a front view of the multi-segment photometric element, and FIGS. 7 and 8 are FIG. 6 is an explanatory diagram of a method for setting the shape of a submirror. FIGS. 9 and 10 are explanatory diagrams showing the reflection characteristics of a conventional Fresnel reflecting mirror. (Explanation of symbols of main parts) 1...Photographing lens 2...Main mirror 4...Submirror 5...Light receiving lens 6...Light receiving element Applicant Nippon Kogaku Kogyo Co., Ltd. Agent Watanabe Takao Figure 1 Figure 2 Figure 3 Figure 4 Figure N'7' Figure 8

Claims (1)

[Scope of Claims] A main mirror that reflects subject light to a finder system and has a semi-transparent section through which the subject light can pass, and a light receiving means in a mirror box that receives the subject light that has passed through the semi-transmissive section. In the TTL photometry device for a camera, the camera has a sub-mirror that is rotatably provided on the main mirror, and the sub-mirror is composed of a combination of two or more types of concentric ring-shaped reflecting mirrors having mutually different reflection characteristics. A TTL photometry device for single-lens reflex cameras.