| 摘要 |
PURPOSE:To perform an error detection with high sensitivity using one optical detector, by receiving light beams focused at least by two two-piece housing type light receiving parts located symmetrically against the center of incident light beams. CONSTITUTION:On an optical axis 40, an optical detector 1 and a split type lens 2 are provided. Transmission light beams at areas 3 and 4 of the lens 2 are made incident on the light receiving parts 7 and 8 of the detector 1 as it is respectively. A track error signal by a push-pull method can be obtained by the light beams. Meanwhile, the transmission light beams at areas 5 and 6 are focused, and are irradiated on two-piece housing light receiving parts 9 and 10 in the detector 1 respectively, and a focus error signal by a knife edge method can be obtained. Thus, by using the knife edge method, the turnaround of the track error signal to the focus error signal can be fully suppressed. And both the focus error signal and the track error signal can be obtained by one optical detector, and the error detection with good sensitivity can be performed.
|
