| 摘要 |
PURPOSE:To form a stable and inexpensive ultrasonic sensor by employing an acoustic matching layer made of wood for impedance matching between a transducer and a medium in the ultrasonic sensor using a ceramic. CONSTITUTION:A wood acquired easily is used for a manufacture member. The acoustic impedance of the wood is specific depending on kinds of wood. The acoustic impedance of an acoustic matching member required is a geometrical mean value of acoustic impedance of a transducer and each medium depending on the matching condition well-known, and the thickness is preferably 1/4 wavelength. As the kind of wood satisfying the condition and easily acquired, a cork or a balsa is used. For example, a balsa member is adhered to a sound wave radiation face of a piezoelectric element 3 and an outer circumference of a wooden piece 4 is fixed by using a metal or a plastic ring having a larger acoustic impedance than the acoustic impedance of the wooden chip. The ultrasonic sensor shows very stable performance and offers an economical market price. |
