APPROXIMATE EXPRESSION OF FAR FIELD GENERATED BY ULTRASONIC ANGLE PROBE AND ITS APPLICATION TO SYNTHETIC APERTURE FOCUSING TECHNIQUE

摘要

Two approximate expressions of the far field of an ultrasonic angle probe are derived, based on the geometrical optics approximation. These expressions and that of the imaginary transducer are applied to the image reconstruction using the synthetic aperture focusing technique. It is demonstrated experimentally that the derived two expressions provide almost the same reconstructed images at correct, that is, predicted position, compared with the expression using the imaginary transducer. It is also shown experimentally that the reconstructed images of slits located near the bottom of a test object appear at different positions depending on the inclination angles of the slits.