| 摘要 |
PURPOSE:To reduce the influence of noise, and to stabilize a track servo, by calculating a tracking error signal by sample-holding a sum signal with the timing of a sampling pulse obtained from a differential signal. CONSTITUTION:Four detecting areas 41-44 are provided in an optical detector 10, and those four detecting areas output (a)-(d). And sums of the outputs of the detecting areas positioned at diagonal positions, S1=(a)+(c), and S2=(b)+(d), are calculated at adder circuits 20 and 21 respectively. Next, a sum signal S3=S1+S2 of the S1 and the S2 is found at an adder circuit 23, and a differential signal S4=S1-S2 between the S1 and the S2 is found at a subtraction circuit 22. Following that, the differential signal S4 is inputted to a leading edge pulse generation circuit 24 and a trailing edge pulse generation circuit 25, then sampling pulses are generated, and those pulses are supplied to gate circuits 26 and 27, and the sampling of the signal S3 is performed. In this way, an accurate tracking error signal can be obtained without being influenced by the noise, and the influence of the noise can be reduced, then the track servo can be stabilized.
|
