| 摘要 |
PROBLEM TO BE SOLVED: To prevent a track servo offset caused by variations in track error signal occurring when scanning defects existing in an information recording medium, in a case of being provided with a track control mechanism. SOLUTION: A light flux emitted from a semiconductor laser 1 is focused on an optical disk 7 and the reflected light is received by a photo-detector 10 for reproducing and error signal, and each error signal of the reproducing signal, focus, and track is detected, and at least a track control for the optical disk is performed. Moreover, a light flux for detecting defects off the viewing angle of a collimator lens 3 is guided to an optical disk 7 by a 1st turning back mirror 11, and is focused at a more advanced position in the rotational direction of the optical disk 7 than the focal spots SP1-SP3 of the above- mentioned emitted light flux, and this reflected light of the light flux for defect detection is received by the 1st defect detection photo-detector 12, and thus, the defect is detected from a change in the level of the received light. When the defect is detected, the track control is halted for a predetermined time to make the objective lens 6 of the optical head into a fixed state and prevent a track offset from occurring by the defect, and thus, a track servo displacement is prevented. |
