| 摘要 |
PURPOSE:To obtain a tracking controller which can always perform reliable tracking control, by appropriately adjusting an offset voltage which changes in accordance with the variation of the total quantity of light received by a photodetector means. CONSTITUTION:This tracking controller is provided with a DC bias adjusting circuit 20 between the output terminal of its divider circuit 15 and the input terminal of its phase compensating circuit 16. A tracking error signal TE'' has an offset voltage which changes in accordance with the variation of total quantity of light received by a photodetector 5, but the offset voltage is adjusted by the DC bias adjusting circuit 20 so that a tracking error signal TEo superposed upon an appropriate DC voltage level can always be obtained. The tracking error signal TEo superposed upon an appropriate DC voltage level obtained from the DC bias adjusting circuit 20 is supplied to a driving coil 18 for adjusting tracking through the phase compensating circuit 16 and a driving amplifier 17, and thus, tracking control is performed.
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