| 摘要 |
PURPOSE:To catch a desired track in a short time by detecting a scan in the inner or outer circumferential direction of a light beam and controlling an optical system with the scan direction detecting output of the light beam. CONSTITUTION:An RF signal is extracted out of on output of a detector 4 by an RF amplifier circuit 17, and the level of the RF signal is discriminated by an RF detecting circuit to extract an RF detecting signal (j). The scan direction of a light beam is detected from the signal (j) and the wave form shaping output of a tracking error delivered from a waveform shaping circuit 8. A light beam scan direction detecting circuit 19 decide the presence or absence of the RF signal at the rise and fall parts of the waveform shaping output of the tracking error signal by making use of a fact that the phase of the tracking error signal is turned by 180 deg. by the scan direction of the light beam. |
