Ultrasonic Intensity and Phase Imaging at 3.6 MHz Using Liquid Crystal Conversion

Absfracf-A new development of the ultrasonic holography technique, using a nematic liquid crystal convertor, is presented, where an image hologram is formed on the convertor with an acoustic lens. It is shown that digital image processing of the fringed pattern, taking a few tens of seconds by an SOSq microcomputer, can provide high-resolution intensity or phase images of various internal material structures, demonstrating applications to nondestructive testing. Highquality intensity images can be made using only an economical analog processing technique if phase images are not required. Imaging delaminations smaller than 1 mm in graphite-epoxy composites is achieved at 3.6 MHz. With this new system a particular form of phase imaging and ultrasonic interferometric holography may become a practical technique.