JPH083578B2 - Camera photometer - Google Patents

Description

The present invention relates to a photometric device for a camera, and more particularly,
The present invention mainly relates to a photometric device for a single-lens reflex camera in which focus detection for autofocus and photometry for automatic exposure control are performed by a light flux that has passed through a taking lens.

[Prior Art] Conventionally, there are various types of photometric devices for automatic exposure control in a single-lens reflex camera having both an autofocus mechanism and an automatic exposure mechanism.
There are one that measures the light flux after being reflected by the quick return mirror and passed through the finder screen, and one that measures the light flux reflected by a reflecting member other than the main mirror that performs the quick return.

[Problems to be Solved by the Invention] Among the above-described conventional photometric devices for cameras, the former takes out a part of the light flux passing through the finder screen toward the eyepiece and performs photometry, so that a large amount of light loss occurs. Since the accuracy of photometry is reduced, and both of them use the light flux near the center of the screen for focus detection of autofocus, for example, as shown in FIG. 6, there is a drawback that the photometric sensitivity drops in the center of the screen. . In FIG. 6, a is a shooting screen, b is a target photometric range, c is a focus detection range, and d and e are photometric sensitivity distributions for automatic exposure control, which are represented by relative sensitivities to image heights. is there.

The present invention eliminates the above-mentioned conventional drawbacks, performs both focus detection for autofocus and photometry for automatic exposure control with high accuracy, and can obtain uniform and even photometric sensitivity. An object is to provide a photometric device for a camera.

[Means for Solving Problems] A photometric device for a camera according to the present invention for solving the above problems includes a condenser lens 2 near a planned focal plane of a photographing lens 1.
And a pair of image forming lenses 4 are arranged in the vicinity of a position conjugate with the exit pupil of the taking lens 1 by the condenser lens 2, and the images formed by the respective image forming lenses 4 are compared with each other. In the camera configured to detect the focus of the taking lens 1, a light receiving element 7 for automatic exposure control for converting the received light amount into an electric amount and outputting the converted light amount is provided between the pair of imaging lenses 4. And

A second invention relating to the present invention is that the condenser lens 2 is provided near the planned focal plane of the taking lens 1.
And a pair of image forming lenses 4 are arranged in the vicinity of a position conjugate with the exit pupil of the taking lens 1 by the condenser lens 2, and the images formed by the respective image forming lenses 4 are compared with each other. In a camera configured to detect the focus of the taking lens 1, a light receiving element 7 for automatic exposure control is provided with a transparent plate so as to convert the received light amount into an electric amount and output it.
The light-shielding mask 6 is provided on the transparent plate 70 and is provided on the transparent plate 70, and the light-shielding mask 6 is formed on the transparent plate 70 to regulate the light flux entering the imaging lens 4.

[Operation] The condenser lens 2 is arranged near the planned focal plane of the taking lens 1, and the light receiving element 7 for automatic exposure control is provided near the position conjugate with the exit pupil of the taking lens 1 by the condenser lens 2.
Is provided, the photometric range in the shooting screen is clearly determined by the effective diameter of the condenser lens 2. Further, since the light receiving element 7 for automatic exposure control is arranged between the pair of imaging lenses 4 near the exit pupil of the taking lens 1 by the condenser lens 2 and the conjugate position, there is no depression in the central portion. Provides photometric sensitivity.

Further, in the second invention related to the present invention, the light flux heading in the direction of the imaging lens 4 passes through the transparent plate 70 to reach the imaging lens 4, and is blocked by the light shielding mask 6 so that the light flux within the predetermined range is reached. Only reaches the imaging lens 4.

[Embodiment] FIG. 1 is a schematic view of an embodiment of the present invention.

Reference numeral 1 denotes a camera lens group (hereinafter simply referred to as a "photo lens").
That is, a condenser lens 2 made of, for example, a single convex lens, and a mask 3 for limiting the incidence of light on the periphery of the condenser lens 2 are arranged near the planned focal plane behind the condenser lens 2.

The mask 3 can be omitted if the light flux incident on the periphery of the condenser lens 2 is similarly blocked by the lens frame or the like.

Although not shown, a photographing film is arranged at an image forming position behind the photographing lens 1, and the condenser lens 2 and the mask 3 are arranged between the photographing lens 1 and the quick return. It is arranged on the optical axis refracted by a known means such as a reflector (not shown) that operates in conjunction with the mirror. The refracting means is not shown since it is not directly related to the present invention, and the refracted optical axis is shown straight in FIG.

In the vicinity of a position conjugate with the exit pupil of the photographing lens 1 by the condenser lens 2, a pair of imaging lenses 4 composed of convex lenses are arranged at symmetrical positions with respect to the optical axis, and the imaging of the imaging lens 4 is performed. A pair of light receiving element arrays 5 are arranged at the positions. These light-receiving element arrays 5 are each made up of the same number (for example, 5) of light-receiving elements, and the outputs from the corresponding light-receiving elements of each array 5 are compared in a focus detection circuit (not shown), and a known so-called correlation method is used. The focus is detected by.

Reference numeral 6 denotes a light-shielding mask which is provided near the imaging lens 4 and near a position conjugate with the exit pupil of the photographing lens 1 by the condenser lens 2, and which regulates a light flux incident on the imaging lens 4 to be constant. By blocking the extra peripheral light from entering the imaging lens 4, the imaging performance of the imaging lens 4 is guaranteed and the accuracy of focus detection is improved.

Reference numeral 7 denotes a light receiving element which is arranged between the pair of imaging lenses 4 and near the position conjugate with the exit pupil of the taking lens 1 by the condenser lens 2 and which converts the received light amount into an electric amount and outputs it. The output from the light-receiving element 7 is processed by a known automatic exposure control circuit (not shown) to control the exposure amount on the film surface.

The above-mentioned mask 3 that restricts the incidence of light on the periphery of the condenser lens 2 blocks the incidence of extra flare components on the light-receiving element array 5 and also enters the light-receiving element 7 for automatic exposure control. The range of the luminous flux to be defined is fixed. That is, since the mask 3 is arranged near the planned focal plane of the photographing lens 1, the photometric range in the photographing screen is clearly defined by the mask 3, and spot photometry, central part photometry, etc. can be performed accurately.

FIG. 2 shows the positional relationship between the projected image 8 of the exit pupil of the taking lens 1, the light receiving element 7 and the imaging lens 4.

When the size of the projected image 8 of the exit pupil is larger than the light receiving surface of the light receiving element 7, the output from the light receiving element 7 becomes uniform, but conversely, the larger the light receiving area of the light receiving element 7, the larger the output signal. Therefore, it is possible to measure light with high accuracy. The same applies to the imaging lens 4 and the light receiving element array 5 side. Therefore, in this embodiment, as shown in FIG. 2, almost all of the light flux in the projected image 8 of the exit pupil is received by the light receiving element 7.
Alternatively, it is configured so as to enter either of the imaging lenses 4. In other words, it is formed that almost all of the light fluxes in the projection image 8 of the exit pupil of the taking lens 1 except the light fluxes that enter the imaging lens 4 enter the light-receiving element 7 for automatic exposure control. There is. Providing the light-shielding mask 6 close to the light-receiving element 7 (on almost the same surface) is also useful for minimizing the light flux that is not effectively used.

FIG. 3 shows the details of the light receiving element 7 portion,
Reference numeral 71 is a so-called PIN layer sandwiching an undoped i layer between p-type and n-type doped layers, and this PIN layer is sandwiched between a transparent electrode 72 and a metal electrode 73, for example, a transparent glass layer. It is fixed to the plate 70 and fixed in the camera.

An insulating layer 74 forms the exterior of the light-receiving element 7 and also serves as a light-shielding mask that defines the range of each light beam incident on the light-receiving element 7 and the imaging lens 4. By fixing the light receiving element via the transparent plate 70 in this way, it is easy to assemble and process, and even if the transparent plate 70 is placed in the light beam for focus detection, the light beam for focus detection is not blocked, so design It can be freely arranged according to the above circumstances.

FIG. 4 shows the photometric sensitivity distribution in the photographic screen of the above-described embodiment, where 10 is the photographic screen, 11 is the target photometric range, and 12 is the focus detection range. 13 and 14 show the photometric sensitivity distribution for automatic exposure control, which is represented by the relative sensitivity to the image height. As described above, in this embodiment, the light receiving element 7 for automatic exposure control is arranged between the pair of imaging lenses 4 arranged near the exit pupil of the photographing lens 1 by the condenser lens 2 and the conjugate position. , Uniform photometric sensitivity with no dip in the central part is obtained.

FIG. 5 shows an embodiment of the second invention related to the present invention, and is the same as the above embodiment except for the peripheral portion of the light receiving element, and is not shown.

In the second aspect of the invention, the light-shielding mask 6 is formed on the surface of the transparent plate 70 to which the light receiving element 7 is fixed, and the light flux heading in the direction of the imaging lens 4 passes through the transparent plate 70 and reaches the imaging lens 4. As the light reaches, it is blocked by the light-shielding mask 6 and only the light flux within a predetermined range reaches the imaging lens 4.

By thus forming the light-shielding mask 6 on the transparent plate 70, the position accuracy of the light-shielding mask is improved, and the accuracy of both focus detection and photometry for automatic exposure can be made higher.

[Effects of the Invention] According to the photometric device for a camera of the present invention, since the photometric range in the shooting screen is clearly determined by the effective diameter of the condenser lens, photometry for automatic exposure control can be performed with extremely high accuracy. Moreover, there is an excellent effect that it is possible to perform high-quality and stable photometry with no drop in sensitivity in the central portion.

In the second invention related to the present invention, the light receiving element is further provided on the transparent plate, and the light shielding mask for defining the range of the light flux incident on the light receiving element and the imaging lens is formed on the transparent plate. Assembling and processing of the light-receiving element and the light-shielding mask are easy, and their positions can be set accurately in the camera, and the accuracy of both focus detection and photometry for automatic exposure can be improved. Have an effect.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of the present invention, and FIG. 2 is a schematic view showing a positional relationship between a projected image of an exit pupil of a photographing lens of the embodiment and a light receiving element and an imaging lens, and FIG. Is an enlarged sectional view showing a light receiving element portion of the embodiment, FIG. 4 is a schematic view showing a photometric sensitivity distribution in a photographing screen of the embodiment, and FIG.
FIG. 6 is an enlarged cross-sectional view of the periphery of a light receiving element for automatic exposure control in an embodiment of the second invention related to the present invention, and FIG. 6 is a schematic view showing a photometric sensitivity distribution of a conventional camera photometric device. 1 ... Photographing lens, 2 ... Condenser lens, 3 ... Mask, 4 ... Imaging lens, 6 ... Shading mask, 7 ... Light receiving element.

Claims (3)

[Claims] 1. A condenser lens is arranged in the vicinity of an expected focal plane of the photographing lens, and a pair of condenser lenses are arranged in the vicinity of a position conjugate with the exit pupil of the condenser lens by the condenser lens, and each condenser lens is arranged. In the camera configured to detect the focus of the photographing lens by comparing the images formed by each other with each other, an automatic exposure control for converting the received light amount into an electric amount and outputting it is provided between the pair of imaging lenses. A photometric device for a camera, which is provided with a light receiving element. 2. The photometric device for a camera according to claim 1, wherein the light receiving element is provided on a transparent plate. 3. A condenser lens is arranged in the vicinity of a planned focal plane of the photographing lens, and a pair of condenser lenses are arranged in the vicinity of a position conjugate with the exit pupil of the condenser lens by the condenser lens, thereby forming each condenser lens. In a camera configured to compare the images formed by each other with each other to detect the focus of the photographing lens, a light receiving element for automatic exposure control for converting the received light amount into an electric amount and outputting the converted light is provided on the transparent plate. A photometric device for a camera, which is arranged between a pair of image-forming lenses, and a light-shielding mask for restricting a light beam incident on the image-forming lenses is formed on the transparent plate thereof.