| 摘要 |
PURPOSE:To reduce the influence of noises and to perform smooth tracking by driving an UP/DOWN counter which controls turning of a tracking mirror by the pulse inputs independent from the output signal of a preamplifier. CONSTITUTION:There are a count-up input 37 and a count-down input 38 in an UP/DOWN counter 29, and the output signal 31 of a D/A converter 30 is made from zero potential to positive or negative potential by the output thereof, whereby the turing direction of a tracking mirror 5 is determined. The turning quantity is determined by the number of the input pulses to the counter 29. The pulses 36 to be counted are created by superposing sample pulses 14a, 14b in an ''exculsive-OR'' gate 33 and are inputted via a delay circuit 34 to a driving direction determining circuit 35, so that to which of the input 37 or the input 38 the pulses 36 are to be inputted is selected in accordance with the level of the output signal 19 of a comparator 18. |
