US Patent 7161886 Optical disc identification method

A method used in an optical disc reproducing system for identifying the type of an optical disc, wherein the optical disc reproducing system comprises a pickup; the pickup comprising a first light source and a second light source. The method comprises: (a) measuring a first time needed for the focus of the first light source to move from a plastic layer to a reflection layer of the optical disc; (b) measuring the characteristics of a focus error signal while the focus of the first light source is moving in the reflection layer of the optical disc; (c) measuring the characteristics of the focus error signal while the focus of the second light source is moving in the reflection layer of the optical disc; and (d) identifying the type of the optical disc according to the first time and the results measured in steps (b) and (c).