JPH0475038A - Photometric device for camera - Google Patents

Abstract

PURPOSE:To accurately measure the brightness of an object by deforming a condenser lens so that a focal distance may be varied and making the light receiving angle of a photodetector variable. CONSTITUTION:By rotating a clamp ring 7 in a state where it screws on a holding part main body 6, the inside diameter of the holding part main body 6 is shortened and the curvature and the thickness of the condenser lens 5 held by the holding part main body 6 can be varied. Consequently, for example, the condenser lens 5 is deformed by the lens holding part 6 according to a zooming magnification and photographing distance. For example, in the case that the zooming magnification is increased, the condenser lens 5 is pressed from a periphery so as to vary the curvature of the condenser lens 5 and make the focal distance short, so that the light receiving angle of the photodetector 2 is narrowed and set at the light receiving angle in which reflected light from the object limited in a photographing area can be received. Thus, the photometry of the brightness of the object is accuratly performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photometering device for a camera, and particularly to an improvement of a device that measures external light for exposure control.

[Prior Art] Conventionally, cameras have automatically set exposure, and in order to control this exposure, there is an external light metering method that measures the brightness of the subject. The structure of the system is shown in FIG.

In FIG. 3, a light receiving element 2, which is a photoelectric conversion element, is arranged through a condensing lens 1, and this light receiving element 2 may be a silicon photodiode (SPD) or a gallium photodiode (SPD).
An arsenic phosphor photodiode (GPD) or the like is used. The light-receiving element 2 generates a current in proportion to the incident light, and receives reflected light from the subject and generates a current in accordance with the brightness of the subject. Therefore, an ammeter 4 is connected to the light receiving element 2 via an amplifier 3.
The brightness of the subject detected by the light receiving element 2 is detected as a current value.

The above-mentioned current value is then supplied to, for example, an exposure control circuit (not shown), which controls the aperture mechanism, shutter speed, etc. according to the brightness of the subject. be done.

[Problem to be solved by the invention] However, in the conventional camera photometer described above, the acceptance angle of the light receiving element 2 that receives external light is constant, and it is difficult to accurately measure the brightness of the subject. The problem is that it cannot be done.

That is, in the case of FIG. 3, the acceptance angle α is
Conventionally, the acceptance angle α is determined by the focal length of
cannot be changed freely.

For example, even when changing the shooting magnification by zooming, light is measured at the same acceptance angle α, so when shooting a subject at a far distance, light other than the subject is also measured, whereas when shooting at a close distance, light is measured at the same angle of acceptance α. can only measure the entire area of the subject. Therefore, it was not possible to accurately measure the brightness of the subject in the photographing area, and it was not possible to set an appropriate amount of exposure.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a photometry device for a camera that can vary the light-receiving angle of a light-receiving element and accurately measure the brightness of a subject. .

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a photometry device for a camera that receives external light with a light receiving element and performs photometry for exposure control. A condensing lens made of a material that collects external light onto the light receiving element, and a lens holder that holds the condensing lens and changes the focal length by deforming the condensing lens by applying force from the surroundings. , characterized in that the light receiving angle of the light receiving element is variable.

The lens holding section can deform the condensing lens by being driven in conjunction with a lens barrel that is rotationally driven for zoom photography.

[Function] According to the above configuration, the condensing lens is deformed by the lens holder depending on the zoom magnification or the shooting distance. For example, when increasing the zoom magnification, the condensing lens is pressed from the surroundings. Shorten the focal length by changing the curvature of the lens. In this case, the light-receiving angle of the light-receiving element becomes narrower, and is set to a light-receiving angle that can receive reflected light from the object limited to the photographing area, so that the brightness of the object can be accurately measured.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of a photometer for a camera according to an embodiment, and the embodiment is adapted to a zoom function.

As shown in the figure, the condensing lens 5 is made of a rubber material that is highly transparent and flexible, and in the embodiment has a refractive index of about 13 to 15, and it can be used from the visible region to the near-infrared region like a normal glass lens. High light transmittance over a wide range (for example, 99
9%/cm) is used. This condensing lens 5 is held by a holding part main body 6 and a tightening ring 7, which is a lens holding part using a chucking mechanism. This lens barrel 8 is provided with external teeth 8a. The ring 7 for tightening the lens holding part is
It has external teeth 7a so as to mesh with the external teeth 8a of the lens barrel 8, and a female threaded portion 7b is cut inside.

On the other hand, the holding part main body 6 is made of a truncated cone-shaped cylindrical body, and a plurality of notches 6a are formed so that the inner diameter of the cylinder can be narrowed. The male threaded portion 6b is formed so that the female threaded portion 7b of the ring 7 is screwed into the male threaded portion 6b. Therefore, tightening can be done by screwing the ring 7 onto the holding part main body 6 and rotating it.
As a result, the curvature and thickness of the condensing lens 5 held by the holding part main body 6 can be changed.

The embodiment has the above configuration, and its operation will be explained below based on FIG. 2.

FIG. 2 shows how the condensing lens 5 is held by the lens holder, and when the zoom magnification is low, the ring 7 should be tightened on the rear end side (specific side) of the holder main body 6. ), and no force is applied to the condensing lens 5, so the light receiving angle α1 of the light receiving element 2 determined by the condensing lens 5 is wide (as shown in the figure).

On the other hand, when the zoom magnification is increased, the lens barrel 8 rotates, and the external teeth 8a and 7a engage with each other, so that the ring 7 tightens the holding line main body 6 (left side)
Rotate to. In this case, the holding line main body 6, which is tightened by the ring 7, reduces its cylindrical inner diameter and tightens the condenser lens 5 from around it, and the condenser lens 5 is compressed as shown by the chain line in FIG. curvature and thickness, which results in a shorter focal length of the lens. Therefore, the light receiving angle of the light receiving element 2 in this case is the second
The angle is α2 in the figure, and the light receiving angle is set narrower than when the zoom magnification is low.

By changing the light-receiving angle of the light-receiving element 2 according to the zoom magnification as described above, it is possible to set the light-receiving angle according to the size of the subject to be photographed. This makes it possible to accurately measure the brightness of a subject.

According to the photometry results, an appropriate exposure amount can be set and exposure control can be performed satisfactorily.

In the embodiments described above, the condenser lens 5 may be made variable by a chucking mechanism, or the focal length (curvature) of the condenser lens 5 may be varied by some other mechanism or an electrically driven configuration.

Further, in the above embodiment, the case where the present invention is applied to the zoom function has been explained, but the light receiving angle may be varied according to the shooting distance regardless of the shooting magnification, and in this case, for example, the above-mentioned holding This can be achieved by driving a member to change the focal length of the condenser lens 5.

[Effects of the Invention] As explained above, according to the present invention, the light receiving element can be adjusted by using a condensing lens made of a transparent and flexible material and changing the focal length by deforming the condensing lens. Since the light-receiving angle can be varied, it is possible to accurately measure the brightness of a subject limited to the photographing area, and it is possible to perform appropriate exposure control even when changing the zoom magnification, for example.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing the configuration of a photometer for a camera according to an embodiment of the present invention, FIG. 2 is a sectional view illustrating a condensing lens made variable by a lens holder, and FIG. 3 is a conventional FIG. 1 is a configuration diagram showing a photometry device for a camera. 1.5... Condensing lens, 2... Light receiving element, 6...
Holding line body, 6a...notch part, 6b...male thread part, 7...tightening ring, 7a...external tooth, 7b...female thread part, 8...lens barrel, 8a... ...external teeth. Patent applicant: Fuji Photo-Koki Co., Ltd.

Claims (2)

[Claims] (1) In a camera photometer that receives external light with a light receiving element and performs photometry for exposure control, a condenser lens made of a transparent and flexible material collects external light onto the light receiving element;
A lens holding part that holds the condensing lens and changes the focal length by deforming the condensing lens by applying force from the surroundings, and is characterized in that the light-receiving angle of the light-receiving element is variable. Photometering device for cameras. (2) The photometry device for a camera according to claim 1, wherein the lens holder deforms the condensing lens by being driven in conjunction with a lens barrel that is rotationally driven for zoom photography.