Focus servo control system for automatically adjusting a relative distance between an objective lens unit and a recording surface of an optical recording medium
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United States of America Patent
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Oct 2, 1984
Grant Date -
N/A
app pub date -
Dec 22, 1981
filing date -
Dec 29, 1980
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A focus servo control system for automatically adjusting a relative distance between an objective lens unit and a recording surface of an optical recording medium in which a laser light beam is converged through an object lens on a recording surface of a recording medium and the laser light is modulated by an optical pattern on the recording surface and reflected therefrom and converted into an electrical signal wherein the focus control system includes a component adapted to be energized by an electrical current to shift the object lens perpendicularly to the recording surface, a component for detecting the laser light reflected from the recording surface for producing an error signal which represents the deviation of the focus of the lens from a desired position with respect to the recording surface, and a servo amplifier adapted to amplify the error signal thereby to produce the electric current for energizing the lens shifting components, and in order to avoid wasteful electrical power consumption and the mechanical noises, the focus control system further includes gain control components for raising the gain of the servo amplifier as the magnitude of the error signal increases.
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