| 摘要 |
PURPOSE:To attain a stable spot positioning method by forming a control track to a disk where the recording and reading spots are formed before and after a track and also providing the photodetectors to both spots to detect the information and track shift signals respectively. CONSTITUTION:A laser light source 1 of a wavelength lambda1 is bent by a galvanomirror 6 and stopped down by a stop-down lens 7 on a track of a disk 8 in the form of a spot 9 for recording and reproducing. While a laser light source 2 of a wavelength lambda2 is also stopped down as a spot 13 for reproduction or erasion through a galvanomirror 12. A control track 50 divided into (n) units of blocks 51 is provided at the most inner or outer circumference of the disk 8. Then pits having recess/projection parts or gradations are recorded equidistantly within blocks 51 for each track and in different numbers. The reflected light given from the disk 8 is detected by photodetectors 17, 20 and 27. Then the information is detected and the track control is carried out. In addition, the minute variance due to the temperature changes or vibrations can be corrected after the positioning is over between two spots by means of the track 50. |
