Camera lens control mechanism

Claim 1

A lens control module comprising a housing attachable to a camera, which camera is equipped with a demand unit and has a lens element movable between extreme positions, said housing containing an actuator (6) for moving the lens element, control means (2) driven by said actuator for movement between extreme positions in unison with the movement of the lens, which control means produces a feedback signal representing the position of the actuator and hence of the lens element, means (20) for producing an error signal representing the difference between a demand signal from said demand unit and said feedback signal, an amplifier (3) connected to control the actuator in response to said error signal, and a slipping clutch (8) connected between said actuator and said control means so that when said control means reaches one of said extreme positions before the lens reaches the corresponding extreme position said clutch slips and said actuator may continue to drive said lens element until the lens element also reaches a corresponding extreme position in alignment with said control means, and switch means (14, 15) accessible from outside said housing and operable to selectively apply a predetermined signal to the actuator which causes said actuator to drive at least one of said lens element and control means until they are brought into alignment in corresponding extreme positions, said module being detachable as a unit from said camera.