| 摘要 |
PURPOSE:To always optimize the performance of the control system by varying the circuit gain of the tracking control system depending whether a light beam is placed to an address part of rugged structure or a signal is positioned to a tracing track part recording and reproducing the signal. CONSTITUTION:A gain switching signal 21 is inputted to a gain switching circuit 20 outputted from a signal processing circuit 15. The level of the gain switching signal 21 is varied depending whether the light beam stays in the address part 17 or the light beam remains the tracing track part 16, and the gain switching circuit 20 switches the amplification factor of the inputted track deviation signal accordingly to give an output to a phase compensation circuit 10, thereby switching the gain of the tracking control system. Even when the reflected luminous quantity is changed while the light beam stays on the address part 17 in this way, since the circuit gain of the control system is switched to make the loop gain of the control system constant, thereby eliminating the deterioration of the performance of the control system of the address part.
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