Barker-coded Ultrasonic Imaging using Optical Surface Vibration Measurement

A refined imaging method is proposed that can detect the surface vibration velocity of a sample placed on a vibrating piezoelectric transducer surface in air. The piezoelectric ultrasonic transducer is excited using a Barker-coded voltage signal under a constant-voltage drive to obtain a vibration velocity with the same waveform as a coded ultrasonic signal in the time domain. The coded vibration velocity is detected using a laser Doppler vibrometer and is used to image the object placed on the transducer via cross-correlation. A silicone rubber sheet containing the characters "U" and "S" are imaged under low S/N conditions to confirm the performance of the method. Ultrasonic velocity in sample can also be measured with this system