S-sequence bias-encoded photoacoustic imaging with top Orthogonal to Bottom Electrode (TOBE) CMUT arrays

Recently we introduced Top Orthogonal to Bottom Electrode (TOBE) Capacitive Micromachined Ultrasound Transducers (CMUTs) as novel 2D arrays capable of 3D ultrasound imaging using only N transmit/receive and N bias channels for an NxN array. Here we adapt these devices for photoacoustic imaging by biasing one column and receiving across rows in parallel, then biasing another column and receiving along rows, and repeating this procedure until all columns have been biased in turn. Only elements in rows which are biased are dominantly sensitive to receive signals. Additionally, we propose a method to bias more than one column at a time using a biasing pattern sampled from rows or columns of a Hadamard S-matrix to improve signal-to-noise ratio, and demonstrate simulation results validating the proposed theory.