JPS6486333A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the stability after adjustment by providing a means vary ing the servo gain, a means generating a transient response, and a means decid ing the converging stage of response so as to vary the gain in the determined converging state thereby setting the gain to the optimum gain with phase margin and gain margin inclusive thereto. CONSTITUTION:An adder 41 is provided to a focus servo circuit 16 to apply external disturbance for servo gain setting by a servo gain setting circuit 17 and the changeover of a multiplexer 43 is controlled to set the optimum servo gain. A pulse generator 51 for external disturbance generation applies an impulse as external disturbance to the adder 41 via an analog switch 52 and applied to a clock input of a counter 53 via a gate of an AND circuit 53. Thus, the excess/deficiency of the servo error signal not coped with the control system by the summed luminous quantity due to variance of the pickup or groove shape of the optical disk can be compensated and the gain is set to a truly optimum servo gain and high speed tracking is realized with stable operation.