| 摘要 |
PROBLEM TO BE SOLVED: To perform a constant seeking operation by reducing a circuit scale and reducing computing data. SOLUTION: The number of traversed tracks is counted with a track number measuring counter 9 and a time (measured cycle) T when an optical beam spot traverses the interval between tracks is measured in a cycle measuring counter 8. The number of remaining tracksΔN till a target track is calculated in a subtractor 11 from the count value of the track number measuring counter 9 and changeover switches 15a, 15b, 15c are controlled by changeover control signals S1 , S2 corresponding to the value. The number of remaining tracksΔN is multiplied by an inclination coefficient A, B or C to be selected by the changeover switch 15c in a multiplier 13 and it is added with an intercept coefficient A, B or C to be selected by the changeover switch 15b in an adder 16 and a linearly approximated target reference cycle TS is generated. Then, the error signalΔT between target reference cycle TS and the measured cycle P is detected in an error detector 17 to be used as the speed control signal of a seeking operation.
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