| 摘要 |
A focus search driving voltage corresponding to a signal surface of an optical disc is obtained on the basis of detection information from a photodetector when an objective lens is focused on the signal surface of the optical disc in the middle of raising or lowering the objective lens placed on standby at a lens midpoint between a temporarily set lens bottom point and a temporarily set lens top point according to a temporarily set lens bottom point voltage and a temporarily set lens top point voltage. Then, a lens bottom point voltage and a lens top point voltage at the time of device starting are obtained by an arithmetic operation program based on the focus search driving voltage and predetermined factors, and then a lens bottom point corresponding to the lens bottom point voltage is set to be nearer to the lens midpoint side than the temporarily set lens bottom point while a lens top point corresponding to the lens top point voltage is set to be nearer to the lens midpoint side than the temporarily set lens top point.
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