| 摘要 |
PURPOSE:To divert the basic function of information reproduction and to inspect whether or not there is a defect on the surface of an optical disk by focusing a laser beam on the surface of the substrate of the optical disk and discriminating the quantity of reflected light detection during surface scanning. CONSTITUTION:A CPU 10 which selects an inspection mode with a switch 11 changes the target point of a focus servo 7 to the surface of the transparent substrate of the optical disk and focuses the laser beam on the surface of the substrate. In this state, the laser beam makes a surface scan on the substrate surface by the movement of the optical head 1 and the rotation of the optical disk, and a defect discrimination part 12 monitors a tracking error signal. In this state, if there is a defect such as a flaw at a beam irradiation point, diffraction is caused by projections and recesses and the reflected light spreads to the environment, so that the quantity of reflected light returning to the optical head 1 decreases. Behavior variation of the reflected light due to a difference between the smooth substrate surface and the presence of the projections and recesses as a defect can be detected most sensitively as level variation of a tracking error signal obtained from the photodetection output of the optical head 1. |
