Imaging in a scanning photoacoustic microscope

Imaging in a scanning photoacoustic microscope (SPAM) is analyzed using Fourier imaging concepts. In particular, the spatial frequency response and the resolution of the instrument are examined. It is shown that in the general case, the imaging is object dependent. However, for the special cases of negligible thermal diffusion or where the specimen is either optically uniform or acoustically and thermally uniform, explicit expressions for the spatial frequency response are derived. It is shown that a SPAM may exhibit superresolution provided an acoustic lens is used rather than a large area detector.