Large-area ultrasound contact imaging

A method and apparatus for ultrasonic contact imaging. A thin-film transistor (TFT) array (225) is deposited on a substrate (210). A receiver (220) having a plurality of receiver elements is deposited on the TFT array (225) to receive a received signal. A transmitter (240) adjacent to the receiver (220) generates a transmit signal at an ultrasonic frequency. The transmit signal is reflected from a surface to produce a reflected signal. The received signal is a superposition of the transmit signal and the reflected signal as result of interference. The received signal is representative of differences in acoustic impedances across the surface.