Evaluation of spatial resolution of spherical-planar-pair lensesfor elasticity measurement with microscopic resolution

The spatial resolution of spherical-planar-pair (SPP) lenses used in an ultrasonic microspectrometer (UMSM) was evaluated by scanning the lenses over a sharp edge of a specimen. The variation of the output observed in experiments was in good agreement with the theory. In the direction perpendicular to the propagation of a leaky surface acoustic wave (SAW), the best spatial resolution was obtained. The distance a_90-10 over which the magnitude decreased from 90% to 10% was 5 μm at the frequency of 260 MHz. In the direction parallel to the leaky SAW propagation, the spatial resolution was severely affected by the excitation of the leaky SAW