| 摘要 |
PROBLEM TO BE SOLVED: To improve the convergency of ultrasonic beams in slice direction orthogonal with the arrangement of vibrating elements. SOLUTION: An acoustic lens 22 is composed of a first lens layer 24 and a second lens layer 26. These lens layers are composed of a base material and a mixture dispersed in it and between two lens layers, only the particle diameter of the mixture is different. Namely, the respective lens layers have mutually the same acoustic impedance and have mutually different attenuation factors on the other hand. The attenuation factor of the second lens layer 26 is higher than that of the first lens layer 24 and the acoustic lens 22 is constituted so as to gradually increase the attenuation factor from the central part to both the terminals in the slice direction as a whole. |
