| 摘要 |
PROBLEM TO BE SOLVED: To improve a recording density without impairing laser beam power, by a method wherein either of first and second addresses common to a groove adjacent to one side of an address information block and to a groove adjacent to the other side thereof is made to contain a specified address mark. SOLUTION: A laser beam emitted from a laser light source is condensed on a disk through a collimator lens and an objective lens and forms a beam spot. After a return light thereof is received by main and sub detectors and converted into an electric signal, a focus error signal is detected therefrom and a tracking error signal of the beam spot is obtained. This signal is selected by a tracking polarity selecting switch SW, and the beam spot is controlled to be at the center of a groove. When the signal inverted by an inverting amplifier is selected by the switch SW, besides, the beam spot is controlled to be at the center of a land. Then, an address mark of two patterns is detected by a system controller and it is discriminated which of first and second read address information is recorded or played back at present. |
