| 摘要 |
PURPOSE:To achieve positioning of a center of a recording track by irradiating points on the circumference of the innermost circumferential circle of a recording track with light, and moving a recording disk in accordance with the quantity of reflected light. CONSTITUTION:A disk mounting table 11 on which a recording disk 2 is mounted is movable as shown by arrows X and Y independently by carriage motors 3 and 4. Four points where two parallel diameter lines cross the innermost circumference in the directions X and Y are irradiated with laser beam bundles (a)-(d) from an unshown light source at right angles to the disk surface. The reflected light beams of said beam bundles (a)-(d) are made incident to photodetecting elements 6-9, which are so arranged that reflected light beams having constant reflection angles by a diffraction grating formed by recording tracks are photodetected. In accordance with a difference in the quantity of a relfected light, the carriage motor 4 is driven and when the track center point of the disk is found, a center hole is bored by a working drill. |
