| 摘要 |
A system for detecting a tracking error comprises a two-divided type light detector (2), LPFs (4a, 4b), first and second waveform generator (5a, 5b), first and second delay circuits (6a, 6b), first and second adders (7a, 7b) and a phase comparator (8). The detector (2) has two photo detecting elements (2a, 2b) disposed separately in the radius direction of an optical disc. The LPFs (4a, 4b) remove high frequency components from the outputs of the elements (2a, 2b). The first waveform generator (5a) generates a sine wave (B1) with amplitude corresponding to the output level of a signal (A1), which passed the LPF (4a). The second waveform generator (5b) generates a sine wave (B2) having the identical frequency to the wave (B1), with amplitude corresponding to the output level of a signal (A2), which passed the LPF (4b). The first delay circuit (6a) delays the wave (B1) by the prescribed amount of delay to form a sine wave (C1). The second delay circuit (6b) delays the wave (B2) by the same amount of delay as the wave (B1) to form a sine wave (C2). The first adder (7a) adds a signal of the wave (B1) to a signal of the wave (C1) to output the first added signal (D1). The second adder (7b) adds the signal of the wave (B1) to a signal of the wave (C2) to output the second added signal (D2). The phase comparator (8) compares the first added signal (D1) with the second added signal (D2).
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