Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1995-06-07
1998-10-27
Allen, Stephone
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
369100, 369 4411, G11B 1304
Patent
active
058280545
ABSTRACT:
An improved focusing method including focus capture and focus control in an optical disc system having a lens and a disc. The method includes the steps of impinging light upon a disc to be read; moving the lens to a first position; monitoring a Quad Sum signal; moving the lens away from the first position towards the disc being read while looking for a maximum of the Quad Sum signal; moving the lens away from the disc; monitoring total light received from the disc; determining, during the monitoring of light, when the total light is above one-half a measured peak value; searching for a first zero crossing; determining when the Quad Sum signal exceeds approximately one-half peak amplitude; and closing focus when the Quad sum signal exceeds the one-half peak amplitude. After closing focus, the method further includes the steps of controlling a focus error signal at a first predetermined gain to produce a first level output, the first predetermined gain being maintained while reading information stored on the disc; and controlling the focus error signal at a second predetermined gain to produce a second level output, the second predetermined gain being maintained while writing information on to the disc, and the second predetermined gain being less than the first predetermined gain. Electronic circuitry and mechanical apparatus are provided for performing the steps of the method.
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Allen Stephone
Bollella Donald
Braun Robert T.
Clark Ronald J.
Discovision Associates
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