CHARACTERISTIC EVALUATION OF LENSES FOR ULTRASONIC MICROSPECTROMETER

An ultrasonic micro-spectrometer (UMSM) was previously developed to me asure the reflection coefficient of a solid specimen at a small spot o n its surface. Lenses for the UMSM consist of a paired spherical trans mitter and planar receiver, denoted as SPP lenses. In this paper, we s how by both experiment and calculation that an acoustic field at the b ack focal plane of the spherical lens directly influences the incident angular dependence of the SPP lenses output. The acoustic field distr ibution depends strongly on the axial symmetry of the transducer in th e spherical transmitter. Therefore, rapid variation of the field in th e case of a circular transducer is successfully prevented by changing the transducer to a rectangular one, which is suitable for system norm alization.