Method and apparatus for automatic deployment of camera lens

Photography – With exposure objective focusing means – focusing aid – or... – Lens drive circuit or motor structure

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G03B 1336

Patent

active

056529287

ABSTRACT:
Camera autofocus apparatus and method employing an autoranging device to determine a lens destination focus position in terms of a target number of signal pulses from a lens motion sensor photo-interrupter. A lens drive motor is initially driven at maximum speed by a 100% pulse width modulated drive signal. At a fixed number of signal pulses in advance of the target, the average motor speed is calculated and a reduced pulse with modulated drive signal, determined based on the calculated motor speed, is applied to the drive motor to cause the lens to arrive at a uniform speed at a near destination focus position that is suitable for application of a standard motor stopping routine. During the motor stopping routine, the motor is initially "plugged" (reverse polarity drive signal) and the signal pulse period is monitored until a predetermined period is reached. At this point, the plug is removed and an electrical brake (short circuit) is applied to the motor to bring the lens to a rest at the destination focus position.

REFERENCES:
patent: 4772909 (1988-09-01), Ogasawara
patent: 4878077 (1989-10-01), Maeno et al.
patent: 4897683 (1990-01-01), Suzuki et al.
patent: 5057859 (1991-10-01), Ishimaru et al.
patent: 5206677 (1993-04-01), Onuki et al.
patent: 5367354 (1994-11-01), Kawasaki et al.

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