Photography – Exposure control circuit – Having temperature compensation circuit
Reexamination Certificate
1996-09-03
2002-05-14
Mahoney, Christopher E. (Department: 2851)
Photography
Exposure control circuit
Having temperature compensation circuit
C396S249000
Reexamination Certificate
active
06389235
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a camera that includes a shutter running condition detecting means.
2. Related Background Art
Conventionally, in operation of cameras, the lens diaphragm limits the light flux from a photographing subject and the mechanical shutter limits the exposure time for a photographing film. The shutter used for the single-lens reflex camera is basically formed of two sheets of curtain including the leading curtain and the trailing curtain and the so-called leading curtain covers the picture surface of the film before the exposure operation.
First, when the shutter button is depressed, the leading curtain is withdrawn from the picture surface to start exposing the surface of the film to light. After a predetermined period of time, the trailing curtain covers the surface of the film. The run of each of the curtains is done by means of a spring force biased mechanically. The start of the run is made by releasing each curtain latched. In prior art, these operations have been totally done under mechanical control, but now are done under electrical control in most cases. Like the prior art, the spring force is utilized to run the leading and trailing curtains, but the start of the run is controlled by activating the electromagnet that latches the curtains.
On the other hand, increasing the shutter speed to, for example, {fraction (1/8000)} sec. has been one of the important specifications. Moreover, recent frequent uses of a stroboscopic photography have been required the stroboscopic synchronization at high speed by which can perform imaging under a bright environment.
In order to achieve the purposes, the running speed (the curtain speed) of each of the curtains must be sharply increased by strengthening the spring force and controlled so as to narrow the width of the slit formed by the leading and trailing curtains. Even if the activating timing of the electromagnet is controlled accurately, the releasing speed of the latching mechanism to the electromagnet as well as the variation in the mechanical running system including a spring may prevent the shutter from operating at a desired shutter time, and more particularly at a high speed over {fraction (1/8000)} sec. This phenomenon can be first found after developing the film. Hence, a shutter which includes means for detecting its operational condition during or immediately after a photographing operation has been proposed.
However, there has been a problem in that a small detecting element mounted within a camera body cannot detect a high speed over {fraction (1/8000)} sec. with a good accuracy. A detecting element with a detection accuracy of 10 &mgr;s, for example, can detect {fraction (1/8000)} sec., or about 122 &mgr;s, but shows an inferior detection accuracy to high shutter speeds faster than {fraction (1/8000)} sec. Moreover, where the detection accuracy of the detection element depends on variations in temperatures, the above-mentioned problem arises. Furthermore, it has been required to consider a display mode in the case of an insufficient detection accuracy.
SUMMARY OF THE INVENTION
In order to overcome the foregoing problems, an object of the present invention is to provide an improved camera that can inform a photographer of the fact that the detection accuracy of the detecting element is insufficient with respect to the inspection shutter speed, thus dealing with the situation.
In order to achieve the objects described above, the camera according to the present invention is characterized by a shutter to limit the exposure time for a record medium; a shutter speed setting unit, hereinafter referred to as setting means, to set, the shutter speed of the shutter a shutter driver and controller, herein referred to as driving and controlling means, for driving and controlling the shutter; a shutter condition detector, hereinafter references as detecting means, to detect the operational condition of the shutter; a manifesting unit to manifest the result detected by the detector; and a memory to store previously inherent data to detect with the shutter condition detecting means. Thee manifesting unit is driven by the shutter condition detecting means, based on the shutter speed set by the shutter speed setting means and inherent data stored in the memory means, and then notifies of the result detected by the shutter condition detecting means.
Moreover, according to the present invention, the camera is characterized by a shutter to limit the exposure time for a record medium; a shutter speed setting means for setting the shutter speed of the shutter a shutter driving and controlling means for driving and controlling the shutter; a shutter operation condition detecting means for detecting the operational condition of the shutter condition detecting means; and a display means for displaying the operational time detected by the shutter condition detecting means.
According to the present invention, the shutter detection estimation level can be varied in accordance with a set shutter time so that the optimum estimation can be performed corresponding to the detection accuracy of the shutter detection means. Varying the display mode in accordance with the detection accuracy enables a most suitable display even if the detection accuracy is insufficient.
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Goto Tetsuro
Hasuda Masanori
Katayama Akira
Mahoney Christopher E.
Nikon Corporation
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