a CW Phased Array Ultrasonic Imaging System.

The goal of this work was to build a digitally scanned and focused ultrasonic phased array imaging system. The system was to consist of two piezoelectric transducer arrays containing 128 elements, transmitting and receiving analog electronics, digital phase controllers, system control electronics, external RF signal processing and a computer to be used for control of the imaging system and the collection and analysis of data. After succeeding in this, the imaging system was reconfigured to provide the first doubly scanned and focused array system, using the transmitting and receiving arrays simultaneously. In other experiments, an entirely new type of ultrasonic transducer array was developed and tested utilizing the piezoelectric material PVF(,2). Bulk wave PVF(,2) arrays for use in liquids were produced and tested and found to perform extremely well. PVF(,2) surface wave arrays were also fabricated and tested for surface acoustic wave scanning on silicon nitride slabs. In a new direction, the phased array imaging system was then modified to determine if it would be possible to produce phase measurements. Several methods of phase imaging by mechanical scan with the phased array system were developed and tested successfully. As a final topic, an entirely different approach to phase imaging, more closely akin to holography, is suggested here as possibly a more effective imaging technique for use with quasi-CW phased array imaging systems.