Photography – With exposure objective focusing means – focusing aid – or... – Lens drive circuit or motor structure
Patent
1996-03-27
1997-07-29
Perkey, W. B.
Photography
With exposure objective focusing means, focusing aid, or...
Lens drive circuit or motor structure
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.
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Baxter Dennis Eugene
Leavy James Vergil
Newman Peter Austin
Richiuso Leonard
Boos, Jr. Francis H.
Eastman Kodak Company
Perkey W. B.
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