| 摘要 |
PURPOSE:To increase the signal level of an oscillating circuit and to improve the SN ratio of a detection signal, by providing a resonance circuit, etc., including a detection part which detects an information signal as variation in electrostatic capacity during a relative scanning on a recording medium. CONSTITUTION:The resonance circuit includes the detection part which detects the information signal as variation in electrostatic capacity during a relative scanning on the recording medium. For example, the power source of a device 1 is turned on and a play button for reproduction is operated to drive a motor; and a turntable 7 mounting a video disk 6 rotates and a pickup head 2 is led to a playback start position to bring the reproducing stylus 8 into contact. Then, a bias is applied from a DC bias circuit 4 to an oscillator 3 through a microswitch 5 opened and closed by an operation arm 9 to energize the resonance circuit by a DC output corresponding to the bias. The potential of the bias applied to the oscillator 3 is made higher in the inner circumferential area of the disk 6 where the SN ratio degrades than that applied the outer circumferential area, increasing the output signal of the oscillator 3. |
