| 摘要 |
PURPOSE:To position an optical head surely, by providing a mechanism which moves the optical head in accordance with the number of pitches to be traversed, which is given from a control circuit, and controls the optical head so that jump is continued until the number of pitches becomes zero. CONSTITUTION:A track selecting mechanism 6 includes a down counter 11 to which the number of pitches to be traversed and based on an operation instruction from a control circuit 5 is set, a flip-flop 12 which receives an index signal from an index sense amplifer 4 and a jump clock, a D-type latch circuit 13 which holds the state of the flip-flop 12, an AND circuit 31, NAND circuits 32- 35, and an inverter 36. When the track selecting mechanism 6 receives an index signal 18 during the access of the optical head, the down counter is counted down without executing jump in case of the forward access, but jump is executed without counting down the down counter in case of the reverse access. |
