| 摘要 |
PURPOSE:To obtain track number in a short time by forming tracks on a disk by recording signals having a fixed space frequency spirally, and obtaining the track number by counting the number of signals included in a specified angle of this track. CONSTITUTION:Signals from a light detector 5 are sent to a counter 17 of a system controller 16 through a terminal A and number of pits 3 on a track 2 on which a light pickup 4 is positioned is counted. When a specified time is elapsed after starting or counting, that is, when a light disk 1 rotated by a specified angle, for instance 0.4 deg., next signal is sent from a frequency divider 15 to the counter 17 through a terminal B. Data counted until that time, that is, the number of bits included in the extent of 0.4 deg. of the track on which the light pickup 4 is positioned is sent to a comparator 25. The comparator 25 compares the data from the counter 27 with the data in a memory 24. Thus, the light pickup 4 is positioned accurately on the track 2. |
