Optical record carrier scanning apparatus providing optoelectronic positioning of the scanning spot
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United States of America Patent
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Apr 17, 1990
Grant Date -
N/A
app pub date -
Mar 28, 1988
filing date -
Jan 21, 1988
priority date (Note) -
Expired
status (Latency Note)
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Abstract
Optical record carrier scanning apparatus including a source of radiation which is tunable to produce different wavelengths of a radiation beam and an optical assembly for forming the radiation beam into a spot for scanning information tracks on the record carrier. The optical assembly includes a diffraction grating which diffracts the beam so that only a selected diffraction order sub-beam thereof is formed into the scanning spot, the diffraction angle of such sub-beam and consequently the position of the scanning spot relative to the track being scanned being variable by variation of the wavelength of the radiation beam. A periodic transverse variation of spot position can thus be produced entirely optoelectronically, for producing a tracking error signal to control the scanning spot to remain centered on the information track.
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