| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem that a tracking error signal gets smaller while acquiring tracking error signals from an information recording medium having different groove pitches.SOLUTION: A tracking error signal is generated by using not only the signal from a light beam in an area diffracted in a diffraction optical system but also the signals from a light beam in a uniformed diffraction optical system, and the calculation is changed for optical disks each having different groove pitches. By disposing a light shield part at the center of the diffraction optical system, the light beam in a central area is prevented from being used for calculation. With this, variation in groove pitches and offset of tracking error signal which is generated in recording boundary are efficiently reduced. |
