| 摘要 |
A focus servo error detection and correction circuit uses a negative feedback control and automatically corrects the error. The circuit comprises four photo detectors (A,B,C,D), a feedback control section coupled with the output terminal of an amplifier (3) and consisting of two resistors (R7,R8), a condenser (C1) and an amplifier (4), and an external control section coupled with the input terminal of the amplifier (4) and consisting of a resistor (R9) and a variable resistor (VR1). The output terminal of the amplifier (4) is coupled with the positive input terminal of the amplifier (3), and the output voltages of the amplifiers (3,4) are added in front of the amplifier (5).
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