Ballistic auto-correlation interferometry

We propose the implementation of a ballistic auto-correlation interferometer (BAI) for the assessment of biological tissues. We develop the theory of the interferometric technique, and demonstrate that a method to isolate ballistic from forward-scattered contributions is of central importance. We, therefore, propose theoretically and experimentally a non-linear grating-based angular filter. A monochromatic source incident on a ruled grating, positioned at grazing diffraction, is followed by a narrow slit to conform the proposed system. We validate the angular amplification experimentally, with values ranging on the order of 10-20X. In addition, similar values of transversal beam size reduction, provide an efficient 100X filtering scheme. As a preliminary study for the implementation of the BAI, we compare two transillumination schemes, which include and exclude the grating-based angular filter. Our preliminary results are encouraging, and indicate that the filter effectively isolates the information needed in the BAI.