| 摘要 |
PROBLEM TO BE SOLVED: To improve accuracy of cancel of offset caused by stray light by generating various signals from reflected light information, performing offset elimination processing, and detecting an offset value by the reflected light information obtained in a state in which reflection quantity becomes the prescribed quantity or less by controlling it variably. SOLUTION: A laser output is started by reproduced power from a laser diode 231, and an object lens 220 is moved forcedly in the direction of focus in a movable range by two shaft mechanism. At the same time, the level of a pull-in signal is monitored, and the position at which reflected light quantity in accordance with the position of an object lens becomes minimum is searched. The position of an object lens at which a pull-in signal becomes minimum in a threshold value or less is detected, and the position of the object lens is stored. When surface deviation of a disk 90 is large, an object lens 220 is moved in the direction of tracking monitoring a pull-in signal, and reflected light quantity and laser power density for a disk signal surface 90a are reduced. |
