OPTICAL DISK REPRODUCING DEVICE

PROBLEM TO BE SOLVED: To reduce an error of disk reading. SOLUTION: When a focus or tracking is moved away from an optimum point, a PLL gain controlling circuit 1 outputs control signals in order to reduce an open loop gain of a PLL circuit 3. In response to the above, the circuit 3 reduces a phase comparison frequency of a phase comparator, reduces the amount of current in a constant current circuit, reduces a synthesized resistor value of a filter circuit and increases the frequency dividing number of a frequency divider. Thus, the open gain of the circuit 3 is further reduced from a normal value and the follow-up characteristic of the circuit 3 for disk reproducing signals is reduced. Therefore, a stable extracted clock is obtained for low reliability disk reproducing signals from a data slicer 14. As a result, the error of disk reading is reduced. COPYRIGHT: (C)2003,JPO