| 摘要 |
PROBLEM TO BE SOLVED: To provide a servo error signal calculation circuit which enables a servo error calculation system to be efficiently changed and has small circuit size as a result. SOLUTION: This focus error signal calculation unit 6 is provided with: a calculation circuit 10 for receiving 16 signals input to input terminals T1 to T16 and outputting signals each indicting a difference between two input signals and signals each indicating a sum; a calculation circuit 20 for outputting signals each indicating a difference between the two output signals and signals each indicating a sum; selection calculation circuits 30 and 31 for selecting 4 signals from 16 output signals and outputting signals each indicating a difference between selected two signals and signals each indicating a sum; and a selection calculation circuit 32 for selecting two from four output signals and outputting a signal indicating a difference between selected 2 signals as a focus error signal FES. Thus, a servo error calculation system is efficiently changed, and circuit size is small. COPYRIGHT: (C)2008,JPO&INPIT
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