| 摘要 |
PURPOSE:To check deformation in the focus and track direction in addition to defect of a disc due to dust by detecting the quantity of acceleration of the disc and comparing it. CONSTITUTION:In order to check the quality of the disc, the acceleration of the disc is compared. To obtain the quantity of the said acceleration, a focus drive signal is formed into a signal corresponding to the movement of a pickup in the focus direction via an equivalent filter 18 at a low frequency region, the obtained signal is extracted for the low frequency component only via an LPF19, and the component is differentiated twice by a differentiation circuit 20. Only a high frequency component is extracted from the focus error signal via an HPF23 at a high frequency region and obtained by a differentiation circuit 24 through double differentiation. The acceleration is obtained by applying twice differentiation via an equivalent filter 26 at a low frequency region in order to obtain the deformation in the tracking direction. The value is inputted to a comparator and whether or not the level is a prescribed level or over is compared. Thus, the deformation in the focus direction is checked in addition to a defect due to dust. |
