| 摘要 |
PROBLEM TO BE SOLVED: To control a focus distance and to make a sensitivity excellent by adding mass to the end part of a piezoelectric element, suppressing a vibration and controlling the effective length of an ultrasonic wave exchange part in the piezoelectric element. SOLUTION: The both end parts of the piezoelectric element 1 are coated with solders 7a and 7b as mass, glass is stuck on a first layer 4a as an acoustic matching layer and a whole surface including the solders 7a and 7b is coated with a second-layer resin 4b. Then the second layer 4b is made to be flat together with the solders 7a and 7b after grinding the surface, the both first and second layers 4a and 4b are made to have the λ/4 thickness of an ultrasonic wave frequency, and the thickness of the solders 7a and 7b is made to be λ/2. By the configuration, the solders 7a and 7b are added at the both sides of the piezoelectric element 1 and the mass is increased compared with the center part where an acoustic matching layer 4 is formed. Therefore, a center part is dominative in the vibration area of the piezoelectric element 1 and the vibration is suppressed by a mass load at the both ends. Thus, the effective length of the ultrasonic wave exchange area in the element 1 becomes the center part. |
