| 摘要 |
PURPOSE:To make a stable reproducing operation possible by increasing high frequency current injected to a sensor electrode when the sticking of foreign substance is detected by the lowering of the level of reproduction output. CONSTITUTION:When foreign substance 17 is interposed in a sensor 2 and a disk 1, the distance between an electrode 14 and the disk 1 is made larger and high frequency current becomes difficult to conduct, and the level of a detection signal from a detector 3 becomes low. A level detector 7 detects the lowering of the signal level and sends an increase signal to a power control circuit 26. The power control circuit 26 raises voltage applied to a high frequency oscillator 27 based on the increasing signal. Accordingly, the oscillation output of the high frequency oscillator 27 is increased, and high frequency current injected to a central conductor 18 through an input antenna 19 is increased, and the high high frequency current is given to a sensor electrode 14 connected to the central conductor 18. Thus, the high frequency current is conducted sufficiently and the lowering of signal detection level is prevented even when the foreign substance is interposed in the sensor 2 and disk 1.
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