| 摘要 |
PURPOSE:To prevent the deterioration of information stored on the surface of a disk medium. CONSTITUTION:By an instruction from a host device, a read timing pulse 11 is generated from a system control circuit 1 and supplied to a laser drive control circuit 2. In the laser drive control circuit 2, when the read timing pulse 11 is active, a changeover switch 21 is turned on, and a current from a read current source 24 is supplied to a current adding circuit 26, added to a current of a constant-current source 25 and drives a semiconductor laser 31. The semiconductor laser 31 emits light by a value of read power Prd. Even when the changeover switch 21 and the changeover switch 22 are both in a turn-off state, the current from the constant-current source 25 is supplied to the current adding circuit 26 and drives the semiconductor laser 31, and the semiconductor laser 31 emits light by a value of servo-control power Psv. |
