| 摘要 |
PURPOSE:To ensure the stable tracking by performing the recording or reproducing while rocking the irradiating position of the luminous flux on a recording medium in response to the low-frequency component of a tracking error signal obtained from a reference information track provided at a partial region of the recording medium. CONSTITUTION:An optical head 23 reproduces the signal of a reference concentric information track 17 recorded to a recording plate 16. This head 23 is provided with a semiconductor laser 24, a collimator lens 25, a beam splitter 26, a condenser lens 27 which is held by a support member which can rocks vertically and horizontally, and a 2-split photodetector 28. The head 23 is actuated by a tracking servomotor to trace the track 17. Thus an error signal ES for tracking control which contains a shift of the information track due to the eccentricity of the plate 16 is obtained from a differential amplifier. A part of this signal ES is transmitted through an LPF30, and an error signal LS which is obtained only by the eccentric component obtained through the LPF30 is stored in a memory circuit 31 via a switch 32. Then the information is recorded or reproduced. |
