Angular Domain Optical Imaging using a micromachined tunnel array and a Keplerian lens system

Angular Domain Imaging (ADI) is a technique that selects quasi-ballistic photons exiting from a highly scattering medium by an array of silicon micromachined micro-tunnels. Each channel has a limited acceptance angle based on its geometry therefore those photons that traverse within the acceptance angle of the micro-tunnels will be detected by the imager. In this paper, the ADI technique has been investigated by using newly micromachined tunnels with less spacing between the channels. Also, a Keplerian lens system is used to remove the diffracted light exiting from the tunnels that results due to internal reflection of scattered photons along the tunnel´s walls. With these changes, improvements in the spatial resolution including sharper edges and definition were observed. The experiments show that the new setup can resolve test structure objects down to 100 μm embedded midway through a 2 cm long cuvette filled with 0.3% Intralipid® solution in the 808 nm wavelength.