| 摘要 |
PURPOSE:To obtain an acoustic lens which can check the generation of multiple reflected waves as noise component by applying a substance close to the acoustic lens in the sound impedance and large in the ultrasonic absorption on the outer surface of the acoustic lens except for a part contacting the sound field medium of a spherical lens thereof and the electrode part thereof. CONSTITUTION:In an acoustic lens 22, a substance, such as germanium, relatively close to the body 23 in the sound impedance and large in the ultrasonic absorption on the outer surface of the body 23 made of sapphire except for the electrode part 24 to be provided with a piezo-electric transducer and the lower spherical concave part 25 contacting the sound field medium such as water 8 to form a germanium-covered layer 26. A high frequency excitation voltage applied to the transducer 3 from a high frequency pulse generator 1 is converted into an ultrasonic wave which propagates as a plane wave to the spherical concave through the sapphire of the lens body 23 and then, converted into a spherical wave with the spherical concave 24, propagating to a sample 5 through water 8. On the other hand, a part of the plane wave reaching the concave 25 of the body 23 is reflected back into the lens body 23 and hits the side wall. The reflected waves are absorbed more significantly by the covered layer 26. |
