Optical pickup apparatus utilizing a diffraction device
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United States of America Patent
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Jul 7, 1992
Grant Date -
N/A
app pub date -
Jan 12, 1990
filing date -
Jan 13, 1989
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
An optical pickup apparatus comprising a diffraction device in which a laser beam from a light source is diffracted by the diffraction device to produce a main beam and two sub-beams which are focused on a recording medium, the beams reflected from the recording medium aare diffracted by the diffraction device to be directed to at least one photodetector, whereby a tracking error signal can be detected from output signals of the photodetector by the three-spot method that is so highly reliable that an offset never arises in the tracking error signal even when the optical axis of the optical system is displaced from a given position.
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