| 摘要 |
PURPOSE:To linearize the displacing characteristic of a piezoelectric element by detecting a variation in an equivalent capacity at the time of driving the element by utilizing a variation in the amplitude of a high frequency signal which does not directly affect an influence to the displacement of the element, and correcting a displacement target signal. CONSTITUTION:A signal S7 having a central frequency fo sufficiently higher than the resonance frequency of a piezoelectric element 11 is superposed by an adder 17 on a displacement target signal S3. This superposed signal S3 is amplified by a piezoelectric element driving amplifier 10, thereby driving the element 11. The terminal voltage of the element 11 becomes the frequency component of a superposed signal by a band pass filter 14 having the frequency fo through a buffer amplifier 13. Further, the amplitude of the superposed signal is detected by an envelope detector 15, and fed back to the adder 17 through an amplifier 16. The gain of the amplifier 16 is so set as to become a suitable correction amount by a signal G1. This correction signal S4 is added by the adder 17 to the signal S3, applied through the amplifier 10 to the element 11, thereby linearizing the displacing characteristic of the element 11. |
