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Tracking system for optical recording and/or reproducing apparatus employing a main light beam and a plurality of auxiliary light beams










Image Number 3 for United States Patent #5090004.

In an optical recording and/or reproducing apparatus a main light beam and at least two auxiliary light beams are caused to impinge upon a disc for recording information thereon or reproducing information therefrom in a manner so that light beam spots formed on the disc by two auxiliary light beams are respectively equidistant from a light beam spot formed on the disc by the main light beam with a space between the auxiliary light beam spots in a radial direction of the disc corresponding to N/2 times a track pitch on the disc and the aforementioned light beams are then guided from the disc to a photosensor comprising a first photodetecting element divided into two parts for detecting the main light beam and a second photodetecting element divided into two parts for detecting both auxiliary light beams. A tracking error signal is produced based on a difference between detection outputs derived respectively from two parts of the first photodetecting element and a difference between detection outputs derived respectively from two parts of the second photodetecting element, one of which is subjected to level adjustment for compensating a difference in intensity between the main light beam and each of the auxiliary light beams.








 
 
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