Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1995-04-25
1997-04-22
Allen, Stephone
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
369 4434, 369 54, G02B 2740, G02B 704, G11B 700
Patent
active
056231385
ABSTRACT:
A focusing control apparatus has a controller and a memory so as to store the control signal of a previous step in the memory. The control signal detected by a photo-detector is changed according to the changes of temperature and light intensity input from a light source. The apparatus performs focusing control by summing in an adder signal output by the controller, which signal is the stored signal on which a computation has been performed, and the new signal input. The apparatus detects and controls an offset signal of the focusing error signal by providing a low-pass filter between the adder and the controller. A feedback circuit including an anti-aliasing circuit is further provided between the output of the adder and the controller, whereby a new focusing control signal is transmitted by correcting the signal stored in the memory after a computation has been performed thereon by the controller. Therefore, the focusing control signal transmitted to the driver of the object lens is stably maintained and the design of a control compensator can be simplified by the use of the feedback circuit.
REFERENCES:
patent: 4286318 (1981-08-01), Immink et al.
patent: 5197058 (1993-03-01), Bell, Jr. et al.
Allen Stephone
Samsung Electronics Co,. Ltd.
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