Imaging through random media by use of low-coherence optical heterodyning

Optical heterodyning is a detection scheme that permits the preferential detection of ballistic photons transmitted through a random medium, providing the imaging of absorbing structures within. We introduce a normalized cross-correlation function as a quantitative measure of image quality and employ it to investigate the effect of source coherence length on the ability of optical heterodyning to detect these absorbing structures. The ability to image in transmission is found to be greatly enhanced by use of a reduced-coherence-length source. The effect on image quality of the transport mean-free-path length is quantified and found to depend on source coherence length. The necessity of considering scatterer particle–particle correlations is also presented.