JPH01147438A - Light receiving device for camera - Google Patents

Abstract

PURPOSE:To attain the coexistence of a photometric system and a focus detecting system in a single optical system and to make the best use of the bottom space of a camera main body by providing an optical path leading a flux from a photographing lens to a photodetector for range finding with a reflecting means possessing photodetectors. CONSTITUTION:The title device is constituted such that a flux from the photographing lens 1 is transmitted from the semi-transparent part of a main mirror 2 and is reflected to a mirror box bottom part 10 by a submirror 7. The flux led to the mirror box bottom part 10 passes through a filter 8 correcting relative luminosity factor and a lens doubling as photometry and focus detection, and makes incident on a metering photodetector 20a provided on part of the reflecting means 20. About 80% of the light incident on the reflecting mirror 20 is reflected on an aluminum surface, and is led to the range finding optical system possessing a light detecting means 14 to obtain focus detection information regarding an object. Two light receiving devices can be efficiently arranged in the small space of the mirror box bottom.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a light receiving device for a camera, and particularly to an eye reflex camera, which performs photometry for detecting focus and determining exposure regarding a subject image by measuring light flux from a photographing lens. This invention relates to a light receiving device for a camera that is efficiently implemented using the following methods.

(Prior art) Conventionally, in an eye reflex camera, as a basic method for simultaneously performing focus detection and photometry, a main mirror having a semi-transparent part is provided behind the photographic lens, and the light beam passing through the photographic lens is A known method is to perform photometry and focus detection by guiding a portion of the light to a focus detection light-receiving element and a photometry light-receiving element arranged at the bottom of a mirror box at the bottom of the camera body.

FIG. 6 is a sectional view of a main part of a conventional camera photometry device in which both photometry and focus detection are performed at the bottom of the camera's mirror box. In the figure, 61 is a photographing lens, 62 is a main mirror having a semi-transparent part, 63 is a sub-mirror, 64 is a film surface, 65 is a photometric element for measuring the brightness of the subject, and 66 is a condensing lens. , 67 is a light receiving element for detecting the focus up to the subject, and 68 is a condenser lens.

In the focus detection device shown in the figure, the light flux that passes through the main mirror 62 out of the light flux that passes through the photographic lens is divided into two light fluxes by the submirror 63, and each light flux is sent separately to a photometric optical system and a focus detection optical system. It has an optical arrangement that guides light.

As shown in the figure, if both the photometry and focus detection functions coexist at the bottom of the mirror box, significant optical and spatial constraints will arise. For this reason, conventionally, for example, the following methods (a) to (d) have been used.

(a) A photometric optical system is incorporated into the finder optical system, and photometry is performed within the finder optical system, and focus detection is performed using a photometric element placed at the bottom of the mirror box.

(b) An optical arrangement is used in which a semi-transmissive mirror is placed at any position in the optical path to split the light beam into two, and one light beam is guided to the photometry optical system, and the other light beam is guided to the focus detection optical system. .

(c) An optical arrangement is used in which the wavefront of the incident light beam is split by a light splitting means placed in the optical path, and one part is guided to the photometric optical system and the other part to the focus detection optical system.

(d) A method of separately extracting signals for side light and focus detection from the same element without using a light splitting means.

However, each of the above methods (a) to (d) has advantages and disadvantages, and it is difficult to perform both photometry and focus detection efficiently.

For example, in method (a), if focusing plates are replaced, differences in the diffusion characteristics of various focusing plates will appear as errors in the photometric output.

Method (b) requires optical space for photometry and focus detection, respectively, which increases the size of the light receiving device. Another problem is that the amount of light is halved and the limit of detectable brightness is low.

In method (c), if the area divided into the focus detection system is enlarged in order to increase the focus detection area, the light metering accuracy of the photometry system decreases due to vignetting of the light beam due to the difference in F-number.

Method (d) becomes difficult due to optical constraints when considering a wide range of photometry from average photometry to spot photometry.

As described above, none of the methods can be said to be satisfactory in terms of optical performance and miniaturization.

(Problems to be Solved by the Invention) The present invention employs a configuration in which a photometry device having two light receiving means for focus detection and photometry is provided in a single optical system, thereby efficiently fitting into the narrow space at the bottom of the mirror box. To provide a light receiving device for a camera having a simple configuration, in which both light receiving devices can be arranged in a single manner, and in addition, a light beam from a photographing lens can be efficiently guided to two light receiving means.

(Means for Solving the Problem) A main mirror having a semi-transparent part behind the photographic lens that transmits a part of the light beam that has passed through the photographic lens, and a main mirror between the main mirror and the photosensitive surface. A light receiving device for a camera that utilizes an output signal from the first light receiving means, further comprising: a submirror that guides a transmitted light flux from the first light receiving means to the first light receiving means; The output signals from the plurality of light receiving means are utilized by arranging a reflecting means in the optical path between the plurality of light receiving means and configuring a part of the reflecting means as the second light receiving means.

(Embodiment) FIG. 1 is a schematic diagram showing an embodiment of the present invention when applied to a single-lens reflex camera. In the figure, 1 is a photographing lens, and 2 is a main mirror having a semi-transparent part. 3 is a pentaprism, and 4 is an eyepiece lens, both of which constitute a part of the finder optical system. 5 is the shutter, 6
is the photosensitive surface. Reference numeral 7 denotes a sub-mirror, which is arranged behind the main mirror 2. 10 is a mirror box at the bottom of the camera body, 10a is an opening of the mirror box 10, 8 is a filter for correcting relative luminosity, and 9 is a lens for photometry and distance measurement, which is provided at the bottom of the mirror box 10. . Reference numeral 20 denotes a reflecting means, which has a light receiving element 20a for photometry as a second light receiving means. 14 is a first light receiving means, which has a focus detection light receiving element 14a.

11 is a mask for ghost prevention, 12 is an aperture for distance measurement,
13 is a lens for pupil division, which includes a mask 11, an aperture 12,
The lens 13 and the light receiving element 14a constitute part of a focus detection optical system.

The first light receiving means 1 is transmitted from the sub mirror 7 via the reflecting means 20.
Each element up to 4 constitutes a single optical system.

Note that the light receiving element 20a and the light receiving element 14a are connected to a printed wiring board 15.

In this embodiment, as shown in the figure, the main mirror 2 reflects a part of the light flux from the object that has passed through the photographic lens 1 and guides it to the pentaprism 3 and eyepiece lens 4 of the finder optical system. The remaining light flux is transmitted through the semi-transparent part of the main mirror 2 and reflected by the sub mirror 7 to the bottom part 10 of the mirror box.

The light beam guided to the mirror box bottom 10 passes through a filter 8 for correcting relative luminous efficiency, and a lens 9 that serves both photometry and focus detection, and then passes through a light receiving element 20a for photometry provided in a part of the reflection means 20. is incident on the In this way, the brightness of the subject is measured.

The reflecting means 20 in this embodiment has a configuration shown in FIG. 3, for example.

FIG. 3 is an enlarged configuration diagram of one embodiment of the reflecting means 20 in the photometric device according to the present invention shown in FIG.

The reflecting means 20 in this embodiment is provided with a second light receiving means. That is, as shown in the figure, a transparent electrode 3 corresponding to the light receiving element 20a is placed on a glass substrate 31 which has been subjected to a transparentization treatment.
2 (for example, ITO; indium titanium oxide, etc.), and amorphous silicon 33 is deposited on the rear part of the transparent electrode 32. Further, an aluminum thin film 34 is applied to the rear part of the amorphous silicon 33, and the entire rear part is covered with a protective part side 35.

Approximately 80% of the light beams coming from the six directions of the arrows to the reflecting means 20 having the configuration shown in the figure, that is, the light beam coming from the sub-mirror side, is reflected by the aluminum film surface 34 of the reflecting means 20, as shown in FIG. Each element is set to face the first light receiving element 14a shown.

Light enters the reflecting means 20 having such a structure, and the transparent electrode 3
2, light w7't is generated between aluminum f1834. In this embodiment, photometry is performed by detecting the photocurrent at this time.

FIG. 4 is a schematic diagram of an embodiment showing the photometric range on the photosensitive surface 6 in the apparatus shown in FIG. In the figure, 41 indicates a photosensitive surface, a is a spot photometry area, b is a partial photometry area,
C indicates the average photometric range.

In this way, the present embodiment is divided into a spot photometry area a, a partial photometry area B, and an average photometry area C as shown in FIG. It is possible to arbitrarily select and perform photometry using the photometry area switching means.

Further, in this embodiment, as shown in FIG. 2, the light receiving element 20a is structured so that it can also measure the diffusely reflected light from the photosensitive surface. That is, in the photometry device shown in FIG. 1, the main mirror 2 is retracted out of the optical path, and the brightness of the subject
That is, the light beam reaching the photosensitive surface is photometered by the light receiving element 20a of the second light receiving means. The figure shows a case in which the light beam passing through the photographing lens 1 is reflected by the photosensitive surface 6 and then photometered by the light receiving element 20a of the reflecting means 20 disposed in the mirror box.

Next, in FIG. 1, about 80% of the light incident on the reflecting means 20 is reflected by the aluminum film surface 34 of the reflecting means 20, and has a first light receiving means 14 for obtaining focus detection information regarding the subject. The light is guided to the ranging optical system. That is,
The light is received by the light receiving element 14a through the mask 11, the aperture 12, and the lens 13, and optical information related to distance measurement is obtained.

In this way, in this embodiment, a reflecting means is provided in the optical path toward the light-receiving element for distance measurement, and a part of the reflecting means is constituted by a light-receiving element made of amorphous silicon or the like. This allows photometry means and focus detection means to coexist in the system.

By adopting such a configuration, the light is guided to the focus detection element 14 without loss of the amount of light used in the reflection means 20, and a photometric device is achieved in which a drop in focus detection particle size is prevented.

Note that the distance measurement according to this embodiment is described in, for example, Japanese Patent Application Laid-Open No. 60-101.
The method proposed in Japanese Patent No. 514 can be applied.

FIG. 5 is a schematic diagram of another embodiment of the present invention. In this figure, the same elements as those shown in FIG. 1 are given the same reference numerals.

In the figure, reference numeral 50 denotes a reflecting means, which itself is made of a transparent material such as acrylic, and forms an optical prism as a whole.

The reflecting means 50 in the figure is the reflecting means 2 shown in FIG.
An optical prism is used in place of the glass substrate 31 in FIG.

In the figure, an optical prism photometric element and a pupil splitting lens 13
Although these are separate bodies, they may be integrally molded.

In each of the above embodiments, the light receiving element for photometry and the light receiving element for focus detection may be replaced. Further, other photometric means may be provided in the single optical system in this embodiment, so that three or more photometric means may be provided as a whole.

(Effects of the Invention) According to the present invention, when guiding light from a photographic lens to a light receiving element for distance measurement, a reflecting means having a light receiving element is provided in the optical path, and the light is guided through the reflecting means. This makes it possible to efficiently coexist the photometry system and focus detection system in a single optical system, making effective use of the narrow space at the bottom of the camera body, and reducing the amount of light lost from the reflecting means. Achieved a light receiving device for a camera that can perform photometry and distance measurement with high precision, and can also perform average photometry, partial photometry, spot photometry, film surface reflection photometry, etc. with a single photoreceptor element. can do.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an embodiment of the present invention, Fig. 2 is a schematic diagram showing a photometric state of film surface reflection in an embodiment of the invention, and Fig. 3 is a mirror box of an embodiment of the invention. FIG. 4 is a schematic diagram showing division of the photometric range in the present invention, and FIG. 5 is a schematic diagram showing another embodiment of the present invention. FIG. 6 is a schematic diagram showing a photometering device at the bottom of a conventional camera. In the figure, 1 is the photographic lens, 2 is the main mirror, 3 is the pentaprism, 4 is the eyepiece lens, 5 is the shutter, 6 is the film surface, 7 is the secondary mirror, 8 is the filter for correcting the relative luminous efficiency, and 9 is the photometer and a dual-purpose lens for focus detection, 10 is a mirror box, 10a is an opening, 20 is a reflecting means, 11 is a mask for ghost prevention, 12 is an aperture for focus detection, 1
3 is a pupil-dividing lens, 14 is a light receiving element for distance measurement, and 15 is a printed wiring board. Patent Applicant: Canon Co., Ltd. Ki 1 Ronrihe Ki 2 Kaito 3 Kai Δ Ryo 4 Zukotsu 6 Zutsuryo 5zu

Claims (1)

[Claims] A main mirror having a semi-transmissive part behind the photographic lens that transmits a part of the light beam that has passed through the photographic lens, and a first light receiving means that receives the transmitted light beam from the main mirror between the main mirror and the photosensitive surface. In a light receiving device for a camera that uses an output signal from the first light receiving means, a reflecting means is disposed in an optical path between the submirror and the first light receiving means. A light receiving device for a camera, characterized in that part of the reflecting means is constituted by a second light receiving means, so that output signals from the plurality of light receiving means are utilized.