Photography – Flash system responsive to focal length or distance – Illumination angle responds to focal length or distance
Reexamination Certificate
2001-09-13
2003-08-26
Adams, Russell (Department: 2851)
Photography
Flash system responsive to focal length or distance
Illumination angle responds to focal length or distance
C396S177000, C396S379000
Reexamination Certificate
active
06611663
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a camera in which the strobe light distribution angle and finder field angle are changed under interlocking with the zooming operations of the photographic optical system.
2. Description of the Related Art
Small-sized and lightweight strobe-built-in cameras have been conventionally used for various purposes, and in particular, most so-called compact cameras whose main purpose of use is to take snapshots have strobe devices installed inside.
In addition, many recent compact cameras have zoom lenses for the purpose of improvement in function, and in accordance with this tendency, many strobe devices have been developed to be conformable to zooming so that proper light intensities are obtained at each focal length of the photographic lens and the strobe light reaches further by increasing the size of the capacitor of the light emitting circuit to increase the light intensity.
Furthermore, many cameras with zoom lenses are constructed so that the field angle of the finder is changed under interlocking with the zoom lens in order to notify a photographer of the photographic field angle by means of the zoom lens.
For example, the camera with a zoom strobe and zoom finder proposed in Japanese Unexamined Patent Publication No. H6-18967 is constructed so that, when the zooming lens group for zooming operations is driven, the lens barrel holding the zooming lens group is rotated, the cam plate is driven up and down by the gear interlock, and the strobe device and finder device executes zooming operations following cam grooves formed in this cam plate.
In the camera proposed in the abovementioned patent publication, since the lens barrel mechanism is divided into a zooming mechanism and a focusing mechanism, the strobe device and the finder device are only interlocked with the zooming mechanism, and thereby, proper strobe light distribution and finder field angle are obtained at each focal length.
However, in order to construct the zooming mechanism and focusing mechanism separate from each other, normally, the focusing mechanism must be constructed so that a lens group for focusing operations is provided inside the zooming mechanism and driven by an exclusive drive source. Therefore, there are problems in this case such that the lens barrel mechanism becomes complicated, the cost increases, and the size of the lens barrel increases in order to install the focusing mechanism inside the lens barrel.
Therefore, recently, for the purpose of simplification and downsizing of the mechanisms, a camera has been proposed which is provided with a lens barrel, so-called, a step-zooming lens barrel that is constructed so that step-zooming of photographic lens and focusing at each zooming step are carried out by using a steplike cam alternately having zooming drive cam regions and focusing drive cam regions.
However, in the abovementioned step-zooming lens barrel, since the zooming mechanism and focusing mechanism are united together, if the strobe device is merely interlocked with the lens barrel, the strobe light distribution angle also changes when focusing, and the light intensity distribution and guide number changes depending on the focusing position, resulting in unevenness in quality of photographs taken.
Also, if the finder device is merely interlocked with the lens barrel, the finder field angle also changes when focusing, and this may give a feeling of incompatibility to the photographer. The present inventor proposed a technique for preventing changes in the strobe light distribution characteristics when focusing in Ser. No. 766,709 (applied on Jan. 22, 2001). Also, the technique disclosed in Japanese Unexamined Patent Publication No. H11-183776 is generally known.
SUMMARY OF THE INVENTION
Therefore, the object of the invention is to always obtain an optimum strobe light distribution angle and finder field angle by a simple construction in a camera with a step-zooming lens barrel. In addition, another object is to provide a camera in which the finder field angle is not allowed to change when focusing.
A camera according to one aspect of the invention comprises: a cam member with cam grooves for moving lens units, where the cam grooves alternately have variable power cam regions which move the lens units for variable power, and focusing cam regions which move the lens units for focusing; an illumination device whose light distribution angle is changeable; a finder device whose field view is changeable; an illumination device drive mechanism constructed so as to change the light distribution angle of the illumination device while the lens units move in the variable power cam regions for variable power, and prevent the illumination device from changing its light distribution angle while the lens units move in the focusing cam regions for focusing; and a finder device drive mechanism constructed so as to change the field angle of the finder device while the lens units move in the variable power cam regions for variable power under interlocking with the cam member, and prevent the finder device from changing its field angle while the lens units move in the focusing cam regions for focusing.
The finder device drive mechanism comprises at least two finder lens units and a finder cam member having cam grooves in which the finder lens units slide. The finder device drive mechanism drives the finder cam member while the lens units move in the variable power cam regions for variable power, and does not drive the finder cam member while the lens units move in the focusing cam regions for focusing.
REFERENCES:
patent: 6072954 (2000-06-01), Onda
patent: 6252628 (2001-06-01), Kobayashi
Camera Having Zoom Flash Device, U.S. patent application Publication, US 2001/0028792 A1, Publication Date Oct. 11, 2001.
Adams Russell
Canon Kabushiki Kaisha
Robin Blecker & Daley
Smith Arthur A
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