DISC DRIVE APPARATUS, AND METHOD FOR RECOGNIZING CD AND DVD

摘要

A method for recognizing type (CD; DVD) of an optical disc, wherein: a light beam (32) is caused to reflect from the optical disc (2); wherein an optical lens (34) is caused to move axially with respect to said optical disc (2); a detector output signal (SR) is analyzed to detect when (P1; ts) a focus point of said light beam (32) substantially coincides with a disc surface and to detect when (P2; tL) said focus point substantially coincides with an information layer wherein a thickness time At is calculated in accordance with the formula: Deltat =tL-ts and wherein the measured thickness time Deltat is compared with a reference value (Deltat REF ) which is calculated from an experience-based average value (DeltatAV(CD)) of the thickness time Deltat of CD discs, or from an experience-based average value (DeltatAV(DVD)) of the thickness time Deltat of DVD discs, or from both.