| 摘要 |
PURPOSE: To avoid the extreme low frequency of an ultrasonic vibration by assigning a matching layer A with a thickness of DA to the surface of the montage surface side of a vibration object K with a thickness of DK and matching the thickness DA of the matching layer A to the thickness DK of the vibration object K. CONSTITUTION: A matching layer A is made of a material, for example polysilicon, where the product between a density and an elastic coefficient is lower than that of ceramic and is placed on a piezoelectric ceramic, and an acoustic exchanger is a resonator in thickness direction with a wavelength of (2n+1)λ/4, where n is an integer that is equal to or larger than 1. Also, the thickness DA of the matching layer A is matched to that of ceramic so that an ultrasonic part discharged in the direction of the montage surface is nearly completely reflected on the surface of the montage. This configuration prevents a plurality of ultrasonic sonars from decreasing a conversion efficiency owing to acousticλcoupling to a support and achieving support at one vibration node. Also, a used piezoelectric ceramic plate can be positively and electrically contacted including no reduction in acoustic amplitude as compared with a freesuspension-typeλ/2 sonar.
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