| 摘要 |
PURPOSE:To detect an accurate track crossing signal for a device that performs the recording and reproducing over plural tracks, by varying the time constant of a track crossing detecting circuit. CONSTITUTION:For an optical recorder and reproducer, a light beam 2 sent from a beam source 1 is focused on a disk-shaped recording medium 7 via a lens 3, a semitransparent mirror 4, a reflector 5 and a focusing lens 6; and the reflected light is applied to a photodetector 8 via a lens 6, the reflector 5 and the mirror 4. In such way, the recorded information is read. When a desired track on a recording medium 7 is retrieved, an output is obtained from a track crossing signal producing circuit 30 that shifts a shift stand 20. The signal waveform differs by the shifting speed of the stand 20. In this connection, a shift speed detection 21 is carried out for the stand 20, and the time constant is varied for the detection of waveform of the circuit 30 in accordance with the output of the detection 21. As a result, the detection is possible for the accurate track crossing signal. |
