| 摘要 |
PURPOSE:To apply stable focus control to a disc having a guide pit by using a focus gain switching circuit for tracking on/off in common as a focus gain switching circuit for reproduction and recording. CONSTITUTION:The focus gain switching circuit has a low gain setting with a tracking-off command signal with focus control-on and tracking-off at first, and even when an external disturbance signal exists in a focus error signal, a drive voltage of a focus control circuit 12 is not saturated and no out-of-focus is caused. Then tracking control is applied with the tracking-on command and since no guide pit exists, the effect of an external disturbance signal due to crossing of guide pit is given on a focus error signal and the tracking performance of focus is improved by increasing a focus-through gain. A focus gain switch circuit 16 is brought into a high gain setting by a tracking-on command signal, the tracking performance of focus is improved at on-state in comparison with off-state and excellent recording/reproduction is attained. |
