| 摘要 |
The invention relates to a technique to detect lands and grooves formed on an optical disk, and is intended to provide a land/groove detecting apparatus capable of steadily obtaining track detection signals and land/groove detection signals. According to the invention, +1-, 0- and -1-order light beams obtained from a three-beam type optical head are received by a 6-divided optical sensor, and the 0-order beam is detected by optical sensor elements a, b, c and d of a 4-divided optical sensor while the +1- and -1-order beams are detected by two optical sensor elements e and f, respectively, on the two sides of the 4-divided optical sensor. The output signals of the optical sensor elements a, b, c, d, e and f are denoted by A, B, C, D, E and F, respectively. As a tracking error signal and a land/groove detection signal are calculated by equations TE=E-F and LG=(2x(A+B+C+D)-(E+F)), the land/groove detection signal LG is held at a zero cross point of the tracking error signal TE, and whether getting on a track has taken place on a land or on a groove is determined according to a polarity of the held land/groove detection signal LG, stable tracking error signals and land/groove detection signals can be obtained.
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