| 摘要 |
PURPOSE:To improve the temperature drift margin of a track signal detecting circuit by irradiating the light of a specific wavelength region, for which recording materials have a high reflection factor, and high absorptivity and the light of a wavelength region other than this specific wavelength region to a recording medium and detecting a track signal from the transmitted light of the latter wavelength region. CONSTITUTION: A light source 18 for recording and reproducing emits the light of a wavelength region A for which recording materials of an optical disc 17 have a high reflection factor and high absorptivity. A light source 19 for track signal detection emits the light of a wavelength region B, for which recording materials of the optical disc 17 have a low reflection factor and low absorptivity, other than the wavelength region A. Lights from light sources 18 and 19 are synthesized by a half mirror 22 and are irradiated as a spot having a minute diameter on a recording track of the disc 17. A photodetector 27 detects information signals recorded on the recording track of the disc 17, and a photodetector 28 for focus detection receives the reflected light to perform focusing. The transmitted light from the disc 17 is received by photodetectors 1 and 2 for track signal detection to control tracking. Thus, the temperature drift margin of the track signal detecting circuit is improved. |
