| 摘要 |
PROBLEM TO BE SOLVED: To make possible optimum laser power adjustment, verification and foreseeing of a scratch, etc., of a disk in real-time at a recording time while performing precise tracking using a differential tracking system by dividing laser beam from a semiconductor to five pieces of diffracted light and detecting them. SOLUTION: The laser beam outgoing from a semiconductor laser is divided into five pieces of beam of zero-order diffracted beam, ±1st-order diffracted beam and ±2nd-order diffracted beam, and they are placed as follows to be detected individually. When the beam spot 44a of the zero-order diffracted beam is placed on a track 56, the beam spot 47a of +2nd-order diffracted beam is placed on the an external track 58 adjacent to it, and the beam spot 45a of the +1st-order diffracted beam is placed on the middle of them. Further, the beam spot 48a of -2nd diffracted beam is placed on the an internal track 60 adjacent to the track 56 on which the beam spot 44a of the zero-order diffracted beam is placed, and the beam spot 46a of -1st-order diffracted beam is placed on the middle between the beam spot 44a of the zero-order diffracted beam and the beam spot 48a of the -1st-order diffracted beam. |
