Photography – Flash system responsive to focal length or distance – Illumination angle responds to focal length or distance
Reexamination Certificate
2000-06-20
2002-06-11
Perkey, W. B. (Department: 2851)
Photography
Flash system responsive to focal length or distance
Illumination angle responds to focal length or distance
C396S175000, C396S177000, C396S349000
Reexamination Certificate
active
06404988
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a camera arranged to be capable of driving a flash device to move to protruded and stowed positions and to vary the illuminating angle of the falsh device.
2. Description of Related Art
Cameras having built-in flash devices have been variously developed. Meanwhile, efforts to reduce the size of cameras have advanced during recent years. The reduction in size of a camera shortens a distance between the optical axis of a photo-taking lens and the optical axis of a flash device. In addition, the zoom ratio of the photo-taking lens has increased. The increase in zoom ratio tends to cause an increase of a distance between the camera and an object of shooting (such as a person of the like), i.e., the so-called photo-taking distance.
Under the above-stated condition, the reflection of illumination light of the flash device is apt to be made incident on the pupil of a person who is the object of shooting and to be reflected by the retina of the person, thereby causing the so-called red-eye phenomenon. It has become important to suppress the red-eye phenomenon.
To suppress the red-eye phenomenon, some of known cameras are arranged to have a flash device preliminarily emit light or some light source (lamp) other than a flash device emit light in such a way as to contract the pupil of the object (person) immediately before taking a shot.
According to another known method, a camera is provided with the so-called pop-up flash device which is arranged to move its light emitting part away from the optical axis of a photo-taking lens in using the flash device. The flash device is arranged to be stowed inside of the camera body when the camera is not used for photo-taking. Therefore, this method not only effectively suppresses the red-eye phenomenon but also enhances the portability of the camera.
Meanwhile, some of known cameras are arranged to vary the illuminating angle of a flash device according to changes taking place in focal length of a photo-taking lens (the variation of magnification), for efficient use of the light energy of the flash device.
Generally, the illuminating angle of a flash device is considered to be sufficient if it covers the angle-of-view range of the camera. In the case of a camera in which the illuminating angle of a flash device is not variable from one angle to another, the illuminating angle is set to cover an angle of view obtained at the focal length of the wide-angle end position of a photo-taking lens having variable focal lengths. Therefore, in such a case, the illuminating angle of the flash device remains at the angle covering the angle of view of the wide-angle end position even when the focal length of the photo-taking lens is shifted to a telephoto position. Further, the guide number of a flash device is fixed irrespective of the focal length of the photo-taking lens in general. Therefore, the guide number of a flash device is determined by a shootable distance at a telephoto end position where a photo-taking lens generally has a large F-number. As a result, the flash device is allowed to emit light at the illuminating angle covering the photo-taking angle of view obtained at the wide-angle end even in a case where a shot is to be taken at the telephoto end position. In such a case, a portion of the light energy emitted to the outside of the range of the photo-taking angle of view is not used and is thus wasted.
In the case of such a camera that is incapable of varying the illuminating angle of a flash device while the focal length of a photo-taking lens is variable, the flash device must be arranged to have the illuminating angle required on the side of the wide-angle end position and also to meet the requirement for the shootable distance on the side of the telephoto end position of the photo-taking lens. In a case where the zoom ratio of the photo-taking lens is large and the photo-taking lens has a large F-number, the flash device must be arranged to have a large guide number accordingly.
However, a larger guide number requires a larger amount of electric energy. Therefore, the sizes of parts of the flash device such as a charging capacitor, a flash tube, etc., become larger to eventually cause an increase in size of the camera. Besides, when the size of the charging capacitor becomes larger, the length of charging time also increases. Then, in continuously taking shots by using the flash device, the length of time of waiting for completion of charging becomes too long, thereby impairing the quick shooting.
To solve this problem, the illuminating angle of a flash device is arranged to be variable according to the focal length of the photo-taking lens as mentioned above. This method permits efficient use of the light energy for taking a shot at a telephoto position without increasing the size of the camera and without necessitating a long period of time for waiting completion of a charging action.
Further, some of known cameras have a flash device arranged by combining the pop-up type and the type having a variable illuminating angle. However, according to this arrangement, the flash device is arranged in most cases to be manually popped up. For stowing the flash device, a light emitting part which is under an urging force of a spring urging the light emitting part to move in the direction of protruding is held at a stowed position by a lock means. In using the flash device, the user of the camera is required to cause the light emitting part to pop up by unlocking the lock means. The flash device is, therefore, not so good in operability.
Another known camera has a cam arranged to be driven by a gear train provided for driving a photo-taking lens barrel and is arranged to protrude a flash device outward from a camera body by means of the cam and a cam follower. The camera is further arranged to have a light emitting part to be movable back and forth within the casing of the flash device in such a way as to vary an illuminating angle by varying a distance between the light emitting part and a convex lens disposed in front of the light emitting part.
The camera which is thus arranged to protrude the flash device outward from the camera body is provided with a cam plate which is arranged to move along with the movement of the photo-taking lens barrel in the direction of an optical axis. The cam plate is arranged to be used for driving a viewfinder and the light emitting part of the flash device to move together.
In the camera of this kind, however, the moving cam plate and the light emitting part must be arranged to reliably engage each other. This requirement imposes some limitation on the protrudable extent of the flash device and also necessitates the cam plate to be large in size. The arrangement of the camera of this kind thus does not permit efficient space utilization.
Further, the arrangement for driving the viewfinder and the light emitting part by means of a common member imposes some restriction in allocating them. Besides, since the action of moving the flash device between its stowed position and its protruded position and the action of varying the illuminating angle of the flash device necessitate use of interlocking members arranged separately from each other. The arrangement, therefore, increases the number of parts and thus causes an increase in cost.
As regards a mechanism for moving a flash device from its stowed position in the upper part of a camera to the external side of the camera, it is conceivable to connect the flash device to the upper part of a lever member which vertically extends within the body of the camera. The lever member is arranged to be swingable on its lower part, i.e., on an axis extending in parallel with the direction of an optical axis. The flash device is thus arranged to be slidingly driven by swinging the lever member.
However, such a flash-device driving mechanism necessitates a large space within the camera body and thus hinders efforts to reduce the size of the camera.
Another known camera disclosed in Japanese Laid-
Canon Kabushiki Kaisha
Perkey W. B.
Robin, Bleccker & Daley
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