Photography – Having photocell at specific position within camera – In viewfinder area
Reexamination Certificate
1999-11-18
2001-06-19
Perkey, W. B. (Department: 2851)
Photography
Having photocell at specific position within camera
In viewfinder area
C396S273000, C396S287000, C396S296000
Reexamination Certificate
active
06249650
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a single-lens reflex camera in which a mirror can be retreated before a shutter is released.
2. Description of the Related Art
Conventionally, there is known a single-lens reflex camera, in which a mirror can be moved between an object observing position for observing an object through a view-finder and a photographing position for taking a picture of the object. When the mirror is set at the object observing position, the mirror is inclined so that a luminous flux passing through a photographing optical system is reflected by the mirror and led to the view-finder. When a shutter release is carried out, the mirror is rotated from the object observing position and retreated to the photographing position, in which the mirror is horizontally positioned. When the photographing operation is completed, the mirror is returned to the object observing position.
In the single-lens reflex camera, a photometry element is provided in an optical path of the view-finder in such a manner that a luminous flux, which is reflected by the mirror which is positioned at the object observing position, is led to the photometry element. A photometry value of the object is sensed, and based on the photometry value, a shutter speed and an aperture value are controlled so that a photographing operation is performed.
In a medium-size camera in which a film having a large photographing area, such as Browny film, is mounted, the mirror is large in proportion to the photographing area. Therefore, in a shutter release operation, a shock, caused by a movement and a stoppage when the mirror is rotated from the object observing position to the photographing position, may cause a bad influence on a photographed image. In order to prevent this influence, the camera is constructed in such a manner that the mirror can be retreated to the photographing position before the shutter release operation.
However, when the mirror is retreated to the photographing position before the shutter release operation, a photometry value of the object cannot be sensed by the photometry element provided in the optical path of the view-finder optical system. Therefore, a photographing operation must be carried out utilizing the photometry value of the object, sensed immediately before the mirror was retreated, with a shutter speed and an aperture value based on the photometry value. Therefore, if a significant change of a luminance of the object occurs after the mirror is retreated, the photographing operation cannot be properly performed.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a single-lens reflex camera, in which, even if a luminance of the object is significantly changed while the mirror is retreated before a photographing operation, an improper photographing operation is prevented.
According to the present invention, there is provided a single-lens reflex camera comprising a mirror, a photometry element, a photoreceptor element, a mirror retreat mechanism and a warning processor.
The mirror is movable between an object observing position, at which a luminous flux passing through a photographing optical system is reflected by the mirror and led to a view-finder optical system, and a photographing position, at which the luminous flux is not reflected by the mirror. The photometry element is provided in an optical path of the view-finder optical system in such a manner that the luminous flux, which is reflected by the mirror at the object observing position, is led to the photometry element. The photoreceptor element has a light receiving surface which faces a shutter, so that a light beam, passing through the photographing optical system and being reflected by a shutter, enters the light receiving surface. The mirror retreat mechanism is provided for retreating the mirror to the photographing position before a shutter release operation in which the shutter opens and closes. The warning processor outputs a warning when a change in the amount of light received by the photoreceptor element exceeds a predetermined range while the mirror is retreated to the photographing position before the shutter release operation. The warning signifies that the change exceeds the predetermined range.
The single-lens reflex camera may further comprise a photometry value storing processor that stores a photometry value of an object to be photographed, the photometry value being obtained by the photometry element before the mirror is retreated by the mirror retreat mechanism. Due to this construction, it is easy for the camera to check if the change exceeds the predetermined range.
Preferably, the warning processor comprises a display, which indicates a first condition mark signifying that the mirror is retreated to the photographing position. In this case, the display may be provided in the view-finder optical system. The display may comprise a liquid crystal display provided on a camera body of the single-lens reflex camera. The first condition mark also signifies that the photometry value, obtained by the photometry element before the mirror is retreated to the photographing position, has been stored in the photometry value processor.
Preferably, the display indicates a second condition mark signifying that the change exceeds the predetermined range after the mirror is retreated by the mirror retreat mechanism. In this case, the single-lens reflex camera may further comprise a comparing processor that repeatedly checks the change. The first condition mark may be a predetermined mark that is lit, and the second condition mark may be the predetermined mark that is flashed.
The single-lens reflex camera may further comprise a mirror control switch for compulsorily moving the mirror from the photographing position when the mirror is retreated to the photographing position.
Further, according to the present invention there is provided a single-lens reflex camera comprising a mirror, a photometry element, a shutter, a photoreceptor element, a mirror retreat mechanism and a photometry value storing processor.
The mirror is movable between an object observing position, at which a luminous flux passing through a photographing optical system is reflected by the mirror and led to a view-finder optical system, and a photographing position, at which the luminous flux is not reflected by the mirror. The photometry element is provided in an optical path of the view-finder optical system in such a manner that the luminous flux, which is reflected by the mirror at the object observing position, is led to the photometry element. The shutter is provided opposite to the photographing optical system with respect to the mirror. The photoreceptor element has a light receiving surface which faces the shutter, so that a light beam, passing through the photographing optical system and being reflected by the shutter, enters the light receiving surface. The mirror retreat mechanism is provided for retreating the mirror to the photographing position before a shutter release operation in which the shutter opens and closes. The photometry value storing processor stores a photometry value of an object to be photographed, the photometry value being obtained by the photometry element before the mirror is retreated by the mirror retreat mechanism.
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Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Perkey W. B.
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