Photography – Having variable focal length of camera objective
Patent
1997-07-14
1998-09-01
Perkey, W. B.
Photography
Having variable focal length of camera objective
396349, 359694, 359823, 359829, G03B 1704, G02B 1514, G02B 702
Patent
active
058024042
ABSTRACT:
A helicoid-structure characterized by width-enlarged parts formed by partially widening the respective troughs, which allow the crests to be linearly moved with the increment per unit rotational angle different from the increment per unit rotational angle with which the crests are linearly moved when they are guided by the troughs alone. In a specific embodiment, a stationary lens barrel is formed in its inner peripheral surface with three troughs, each describing a helical curve of appropriate length, on one hand, and a movable lens barrel is formed on its outer peripheral surface with three crests corresponding to the respective troughs each describing a helical curve of appropriate length, on the other hand. The respective troughs are partially widened transversely of the respective helical curves to form width-enlarged parts and a length of each width-enlarged part is dimensioned to be substantially equal to a length of each crest. When the crests move along the respective troughs and reach the respective width-enlarged parts, the respective crests shift transversely of the respective width-enlarged parts, whereupon an increment of linear movement per unit rotational angle with which the movable lens barrel linearly moves relative to the stationary lens barrel is varied.
REFERENCES:
patent: 5018832 (1991-05-01), Terunuma et al.
patent: 5066103 (1991-11-01), Kodaka et al.
patent: 5659810 (1997-08-01), Nomura et al.
Fuji Photo Optical Co., Ltd.
Perkey W. B.
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