  We present a pressure sensor based on a Michelson interferometer, for use in
photoacoustic tomography. Quadrature phase detection is employed allowing
measurement at any point on the mirror surface without having to retune the
interferometer, as is typically required by Fabry-Perot type detectors. This
opens the door to rapid full surface detection, which is necessary for clinical
applications. Theory relating acoustic pressure to detected acoustic particle
displacements is used to calculate the detector sensitivity, which is validated
with measurement. Proof-of-concept tomographic images of blood vessel phantoms
have been taken with sub-millimeter resolution at depths of several
millimeters.
