| 摘要 |
PURPOSE:To attain retrieval in a short time by interpolating a track crossing signal to attain accurate count of a crossing track when an optical beam crosses a recording medium at a high speed and a track crossing detection output is missing. CONSTITUTION:When the moving speed of a moving stand is fast, a switch 82 transmits an output of a variable frequency generating circuit 81 to a drive control circuit. When the optical beam crosses the sector separator area or the address area on the recording medium, a photodetector detects the said areas. A waveform shaping circuit 83 transmits a signal at H level in the said area and L in other area to a switch 78. When the output signal of the circuit 83 is H, the switch 78 turns off the switch and an output of the comparator 77 is not transmitted to a phase comparator circuit 79. When the signal inputted from the switch 78 is missing, the circuit 79 holds the phase error just before. Then even if the signal inputted via the switch 78 is missing, the output signal of the variable frequency generating circuit 81 is interpolated. |
