| 摘要 |
PROBLEM TO BE SOLVED: To determine, with a simple structure and low power consumption and in a reliable manner, whether or not an optical disk is set when an optical disk device is started.SOLUTION: A clamper which fixes an optical disk on a turn table by pressing it down is provided with, on a surface which comes into contact with the optical device, a reflection surface having high reflection parts and low reflection parts. A laser beam is emitted from an optical head, and the optical head receives a reflected light beam from the reflection surface of the clamper when an optical disk is not set and receives a reflected light beam from an optical disk when the optical disk is set. By analyzing a signal pattern thereof, presence/absence of an optical disk is determined. The reflection surface is made either in such a manner that the low reflection parts are formed in radial line shapes starting from a rotational center on a surface of a high reflection part or in such a manner that the low reflection parts are formed in concentric circle shapes on a surface of a high reflection part. |
