| 摘要 |
PURPOSE:To decrease the fluctuation in the sensitivity of focus error by extracting and outputting a focus error signal when an optical spot is not irradiated on a pit so as to eliminate the effect of the shape of pit. CONSTITUTION:An extracting means comprising a sampling pulse generating circuit 7 inputting a recording information signal (RF signal) to a focus error detector and a sample-and-hold circuit 8 inputting an output of a subtraction circuit 4 and sampling and holding the output of the subtraction circuit 4 with a pulse outputted from the sampling pulse generating circuit 7 is provided so as to apply an output of the sample-and-hold circuit 8 to a focus servo device as a focus error signal. The time of generation of an output of a delay circuit 7-4 is within a period when the optical spot is not irradiated to the pit, that is, within the period when the RF signal is at high level. Thus, an output of the subtractor 4 is sampled and held during the period when the RF signal is at high level and the fluctuation in the sensitivity of focus error detection due to the shape of pit is eliminated. |
