JPS61151629A - Light receiving constitution of single-lens reflex camera - Google Patents

Abstract

PURPOSE:To accurately receive luminous fluxes passing through a photographing lens under a condition where the sensitivity distribution is uniform, by reflecting a shutter luminous flux passing through a half mirror by means of the rear sides of the shutter and half mirror and making the luminous fluxes incident on a photoreceptor element provided at a specific position. CONSTITUTION:A luminous flux passing through a photographing lens composed of lens groups 1-3 is divided into a finder luminous flux and shutter luminous flux by means of a half mirror 7. The shutter luminous flux passing through the half mirror 7 is reflected by a shutter 11 and again reflected by the rear side of the half mirror 7 and made incident on and received by a photoreceptor element 12 provided in the direction of the optical axis of a film 6, etc., and at the image forming position. When such constitution is used, the luminous flux passing through the photographing lens can be received accurately under a condition where the sensitivity distribution is uniform.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to the light receiving configuration of a single-lens reflex camera, particularly the arrangement of light-receiving elements. (Prior art) For photometry or distance measurement of a single-lens reflex camera. The light-receiving configuration requires the following Kfl conditions: (1) The light-receiving optical system must have a simple configuration and be easy to adjust.Q) A sufficient amount of light must be obtained.

(3) In photometry, a desired photometric sensitivity distribution can be obtained.In response to this, the following conventional light receiving configurations, particularly the arrangement of light receiving elements, have been proposed.

(a) 7 A configuration in which a light receiving element is placed near the eyepiece lens of the finder optical system to receive object light from the focusing plate.

(b) A configuration in which the center of the focus plate of the finder optical system is cut diagonally and joined together to form a half mirror with this joint surface, and a portion of the light beam at the center of the focus plate is guided to a light receiving element placed on the side of the focus plate.

(0) The central part of the main mirror that reflects the subject light toward the finder optical system in the lowered position is semi-transparent,
A configuration in which a sub-mirror is arranged behind this semi-transmissive part and a light receiving element is arranged in the opposite direction of the subject light from the sub-mirror.

(d) A configuration in which the light from the subject reflected on the film surface during photography is received by a light-receiving element placed in front of the film surface.

However, in the conventional configurations (a) to (d) described above, it is not possible to satisfy all of the conditions (1) to (3) of the light receiving configuration described above. Obtaining a photometric sensitivity distribution with no bias in the area, for example, dividing photometry, has caused difficult problems.
It is an object of the present invention to provide a light-receiving configuration for a single-lens reflex camera that can obtain accurate light reception, especially a uniform sensitivity distribution of a light beam passing through a photographic lens.

In order to achieve the above object, the present invention provides an optical axis along which a beam of light transmitted through a No. 7 mirror and reflected on a shutter surface or a film surface is reflected again on a surface of the half mirror on the side opposite to the photographic lens. It is characterized by a light-receiving configuration in a single-lens reflex camera in which a light-receiving element is arranged in a direction and at a position where an image is formed.

(Example) In FIG. 1, the main part configuration of a single-lens reflex camera according to an example of the present invention will be explained. The photographing lens has a first group lens configuration 1, a second group lens configuration 2, and a third group lens configuration. 6 is
It is constructed within a lens barrel (not shown), and has an aperture 5 in the middle.
is located.

Reference numeral 6 indicates a film loaded in the camera body, and reference numeral 7 indicates a half mirror, which can reflect the subject light that has passed through the photographing lens toward the viewfinder optical system (described later) and transmit it toward the film 6. , are fixedly arranged at an angle of about 45° with respect to the optical axis. 8 is the focus plate of the finder optical system, 09, which is placed at the imaging distance of the subject image, is also a penta roof prism, and 10 is also an eyepiece lens. 11 is a shutter placed immediately after the half mirror 7, and the main plate 11
The leading curtain 11C9 and the trailing curtain 11d, each of which is composed of a plurality of divided blades, are configured to run in a space K between the cover plate 111) and the cover plate 111) with a predetermined time interval. 12 is a light receiving element for photometry, and the optical axis direction in which the subject light that has passed through the photographic lens passes through the half mirror 7, is reflected on the blade surface of the shutter 11, and is reflected on the back surface of the half mirror 7; That is, 04, which is located below the half mirror 7 and at the imaging distance position, is a fourth lens group that functions as a teleconverter and is located behind the shutter 11 of the camera body. , a subject image is formed at the surface position of the film 6.

Therefore, the subject lights Li, Lsj, and Lk that have entered the first group lens configuration 1 of the photographic lens are partially transmitted through the half mirror 7 and reach the shutter 11, and when the shutter is opened during exposure, they pass through the shutter 11. and reach each point 6i, 6j, 6ktc on the film 6. Further, the remaining subject light is reflected by the half mirror 7 toward the finder optical system and reaches each point (8i, 8j, 8&) on the focusing plate 8. Here, the film 6 and the focusing plate 8 are half mirrors.
Although the distances from the lens 7 are different, since the fourth group lens configuration 4 is used and the two are set in an optically conjugate relationship, the object image is formed by both.

On the other hand, during photometry by operating the first stage of the release button, etc., the shutter is closed by the front curtain 11C of the shutter 11, so the subject light transmitted through the half mirror 7 is
, Lj, and LA are reflected by the front curtain 110, and then reflected by the back surface of the half mirror 7 (on the side opposite to the photographic lens), to each point 12i of the light receiving element 12 arranged in the direction of the reflected optical axis.

12j, reaching 12k. Here, in this embodiment, since the optical path length from passing through the half mirror to reaching the light receiving element 12 is set equal to the optical path length to the above-mentioned focusing plate 8, the object image appears on the light receiving element 12. will form an image. Here, in this case, the shutter 1
The closer the reflective surface of the first curtain 11C is to a mirror surface, the more
It is a theory that the conjugate relationship between the light receiving element 12 and the focusing plate 8 (film surface 6) approaches. Furthermore, this first act 11C
Various methods can be considered to make the blade surface close to a mirror surface, such as bright plating on the blade surface or vapor deposition of particles with high reflectance.

Therefore, during photometry, the light-receiving element 12 can perform photometry with a completely uniform sensitivity distribution over the entire screen, and can perform accurate photometry with a uniform sensitivity distribution without deviation compared to conventional methods, such as average photometry or divided photometry. Photometry can be performed. In addition, the light receiving element 12 in this embodiment has a large size so that it can receive the entire area of the object light that passes through the half mirror 7, so it can measure light in any area of the object light, and various types of photometry can be done easily. Furthermore, the influence of deviations and changes in sensitivity distribution due to positional deviations of the element 12 can be reduced. Furthermore, in this embodiment, a sufficient amount of light can be obtained with respect to the amount of light incident on the light receiving element 12. In other words, if the transmittance of the half mirror 7 is set to 70%, the reflectance on the front and back surfaces of the half mirror is set to 3OS, and the reflectance of the shutter front curtain 11c is set to 80% as numerical conditions that can be realized, the reception of the subject light is Element 1
The ratio of the received light flux of 2 is 0.7X O, 8X O, 3= 0.16B ・
It is represented by .

Next, the photometry method will be explained with reference to FIGS. 2 and 3.

FIG. 2 shows a specific element arrangement of the light receiving element 12. Each light receiving element 1 such as 5pa (silicon photocell)
2a to 128 are arranged separately as shown in the figure, and by using each of the light receiving elements 125 to 128 independently, partial photometry is possible, and by using all of them, average photometry is possible. Photometry using various combinations K of the elements 12L to 126 is also possible.

FIG. 3 shows the main parts of the photometry circuit, and each light receiving element 12
a to 120 are connected to each other via changeover switches 20a to 20e (mechanical switches are shown in the figure for ease of understanding, but are actually composed of semiconductor switches).
1j, and each output terminal of these light receiving elements 12a to 128 is connected to two input terminals of an operational amplifier 22. The feedback path of this operational amplifier 22 includes the light receiving elements 12a to 1.
A diode 24 is connected which logarithmically compresses the photocurrent of 2e. Note that the divider 26 connected to the output end of the operational amplifier 22 is a well-known circuit for dividing the logarithmically compressed photocurrent value when a plurality of light receiving elements 12a to 1241 are switched on to an appropriate value. be.

In such a configuration, when the switch 20a is closed, the photometric value of only the center of the subject is obtained as a logarithmically compressed value,
Further, when all the switches 20a to 20e are closed and this photometric value is appropriately divided by the divider 26, the average photometric value is obtained as a logarithmically compressed value.

It should be noted that the photometric circuits for the parts other than those shown in the drawings may be well-known arithmetic circuits, real-time expansion circuits, etc., and detailed explanations thereof will be omitted.

In the above-described embodiment, the shutter 11 may have a different configuration, such as a horizontally running focal plane shutter in which the leading and trailing curtains are wound around a drum and run, to achieve the same effect.

Further, the light receiving element 12 in the embodiment may be made of, for example, amorphous silicon other than SPC.

Further, the light receiving structure of the present invention can obtain similar various effects even when it is a light receiving structure for receiving object light or active light for distance measurement, for example, in addition to the structure for photometry shown in the above-described embodiments.

(Effects of the Invention) As explained above, the present invention reflects the light beam transmitted through the half mirror on the shutter surface, and further reflects the reflected light beam on the back surface of the half mirror, so that the direction of the reflected optical axis is Since an image similar to the image on the film surface is formed on the light receiving element by the K guided to the light receiving element at the image position, the light beam passing through the photographing lens is not biased and an accurate sensitivity distribution can be obtained. A light receiving configuration for a reflex camera can be provided.

Further, when the present invention is used in a photometry device, it is possible to perform photometry of a specific area, such as divisional photometry of a subject image, with great accuracy.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the main part configuration of a single-lens reflex camera according to an embodiment of the present invention. FIG. 2 is a plan view of a light receiving element. Figure 3 is a circuit diagram of the main parts of the photometric circuit. 1.2, 3.4... Lens configuration 60 ■... Film 7... Half mirror 8 sense focusing plate 11... Shutter 12... 11 light receiving elements Canon Corporation

Claims (1)

[Claims] (1) A half mirror that divides the light beam that has passed through the photographic lens into a light beam that is reflected toward the viewfinder optical system and a light beam that is transmitted toward the shutter surface; a light-receiving element disposed in the optical axis direction and at a position where the light beam is reflected again by the surface of the half mirror on the side opposite to the photographing lens and where the image is formed;
A light-receiving configuration in a single-lens reflex camera characterized by being provided with.