Photographic camera of automatic focussing type

Details Photographic camera of automatic focussing type Photographic camera of automatic focussing type

1980-12-19

1981-12-01

Gellner, Michael L.

354 31, G03B 310

Patent

active

043033210

ABSTRACT:
A photographic camera of automatic focussing type capable of focussing objects between a minimum and infinite distance. A focussing motor is coupled to a movable objective lens for moving the lens for focussing an image of an object to be photographed. A photoelectric focussing detector has a photoconductive element responsive to light rays passing through the objective lens. The photoconductive element provides a maximum response when an image of the object formed on the photoconductive element is in the focussed condition. A first electrical circuit determines the direction of movement of the focussing motor for moving the objective lens to focus the object image. A responsive zone is defined within which the output of the detector varies in accordance with the position of the objective lens, and a non-responsive zone is defined away from the responsive zone and within which the output of the detector is invariant independent of the position of the objective lens. A second electrical circuit causes the motor to rotate at a first speed when the objective lens is in the non-responsive zone, and for causing the motor to rotate at a second speed less than the first speed when the objective lens is in the responsive zone. A first switch is adapted to be actuated when the objective lens is at a position for focussing at the infinite distance, and a second switch is adapted to be actuated when the objective lens is at a position for focussing at the minimum distance such that when either switch is actuated, the rotation of the focussing motor is reversed.

REFERENCES:
patent: 3936187 (1976-02-01), Momose
patent: 4180309 (1979-12-01), Miyata et al.

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