| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method for classifying reflection conditions of an optical disk at a plurality of recording layers and at other than recording layer represented by a mirror surface or the like, and to provide a method by which it can be judged quickly that at which recording layer the present focal point is positioned from the classified result. <P>SOLUTION: A controller 303 requests that a beam expander 7 is removed to a position corresponding to a recording layer to be focused, to a driver 306. In addition, a feedback loop comprising a photodetector 10, a DSP 305 and the driver 306 is turned on, an amplitude value of a TE signal is detected, and recorded in a RAM 303b. The above is performed for a plurality of recording layer, and it can be detected whether the desired recording layer is focused or not by contrasting amplitude values of TE signals. <P>COPYRIGHT: (C)2011,JPO&INPIT |
