Arrangement for detecting a signal for effecting a focus control of an optical head
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United States of America Patent
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Jun 11, 1991
Issued Date -
N/A
app pub date -
Dec 26, 1989
filing date -
Apr 15, 1987
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
This device is an arrangement for detecting a signal for effecting a focus control of an optical head with respect to an optical information recording medium by making use of a reflected light beam from the optical information recording medium. On an optical path for a reflected light beam reflected from the recording surface of the optical recording medium, a photodetector is provided. This photodetector is composed of a plurality of elements arranged symmetrically in the transverse cross section of the light beam. Thus, an output of the outside element and an output of the inside element of the plural elements arranged in the transverse cross section of the light beam are used to detect a focus error, thus to utilize the signal detected for the focus control.
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