| 摘要 |
A detection signal is asserted when a surface of an optical disc or an Information recording layer is detected from the light reflected from the disk as the focus of the light beam is varied with respect to the disk. The said detection signal is asserted for a set masking time interval and it is normally the case that two detections will be asserted, one at the surface and one at the recording layer. By calculating the time (T1) taken between assertions, the thickness of the cover layer and thus the type of disk (BD,DVD,CD) can be detected by detecting the value T1 with a series of threshold values.
In the case that more than two detections occur, it is assumed that one is in error. In this case, two timing values (T1,T2) are calculated, and the greater value is used to determine the type of disk.
|
