| 摘要 |
PROBLEM TO BE SOLVED: To make obtainable focus error signals which are adequate respectively during a focus drawing and during a focus servo operation. SOLUTION: When the focus drawing operation is carried out, both of switches 81-1 and 81-2 are held open and only the focus error signal obtained from a light spot by zero order light is used as the focus error signal. On the other hand, when the focus drawing operation is ended, the switches 81-1 and 81-2 are closed and the focus error signal obtained from the light spot of±1st order light is also used as the focus error signal.
|
