Angular filters for angular domain imaging optical tomography in highly scattering media

Angular Domain Imaging performs Optical Tomography imaging through highly scattering media by rejecting scattered light through micromachined Angular Filter Array (AFA) tunnels or an aperture-based Spatial Filter (SF) while accepting non-scattered light with only small angular deviations from the source. AFA imaging using a laser diode source (λ = 670 nm) resolves 153 µm structures at a Scattering Ratio (SR) of 10^7:1 in a milk-based scattering solution and 204 µm patterns for chicken tissue ±3.8 mm thick. Carbon deposition and NH4OH silicon roughening of the AFA tunnels is shown to reduce background scattered light. Smaller tunnel geometries and scan steps improve image resolution. A lens with aperture ADI Spatial Filtering was studied to verify theoretical predictions of the tradeoff between resolution and scattered light rejection. SF ADI with an Argon laser resolved 102 µm structures in a SR = 1.4×10^7:1 milk solution.