| 摘要 |
PURPOSE:To make focus offset quantity minimum by storing the relation of bias voltage to a focus offset signal and adjusting the focus offset at the time of performing an operation from the relation. CONSTITUTION:A focus error signal SFE is generated in an arithmetic circuit 14 and inputted in a differential amplifier 28. The focus offset signal SFO is generated in an arithmetic circuit 17 and signal voltage VFO is supplied to a microprocessor 19 through an A/D converter 18. The processor 19 reads out voltage VOF for the incorporated voltage VFO from a memory 21 based on the relative relation of the voltage VFO to the offset adjusting signal voltage VOF and outputs it to an amplifier 28 through a D/A converter 23. In the amplifier 28, the focus offset component, that is, the voltage VOF is subtracted from the signal SFE, so that the focus error signal SFE' where the focus offset component is erased is generated and impressed on a lens actuator 29. The actuator 29 moves an objective lens 9 to a position where the focus offset quantity is eliminated. |
