Optical pickup device with tracking and focusing utilizing a photodetector having four regions
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United States of America Patent
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-
Mar 21, 1989
Grant Date -
N/A
app pub date -
Oct 5, 1987
filing date -
Oct 3, 1986
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
In an optical pickup device for a compact disk or the like, the photodetector is divided into four regions by three parallel division lines. A focus error signal is produced by forming the difference between the sum of the outputs of the inner two regions and the sum of the outputs of the outer two regions, while a tracking error signal is generated by forming the difference between the outputs of one of the outer regions and its adjacent inner region. The sum of the widths of the two inner regions is set such that the focus error signal is zero when the reflected beam is in focus on the disk. The direction of movement of the track is inclined with respect to the division lines so that the differences in outputs from each of the adjacent inner and outer regions is zero or a minimum. The direction of movement of the light beam during tracking is parallel to the division lines.
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Cited Art Landscape
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