Diffuse Reflectance Spectroscopy (DRS) uses light in the visible-near-infrared (NIR) spectrum for sub-surface sensing within optically turbid media such as biological tissues. Commonly, DRS based tissue sensing uses fiber-optic probes in direct contact with tissue, creating illumination and detection spots on the tissue sample at a fixed source-detector separation (SDS). Such a geometry eliminates Fresnel reflections from being collected by the detector and only samples multiply back-scattered light from the medium. Although fibers provide a straightforward means to implement DRS, physical contact of the fiber with tissue may perturb optical properties and, in several cases, may not be feasible. Here, we develop a non-contact, broadband optical system to acquire DRS measurements from a flat medium at a working distance of 2-3 cm. We characterize the beam profiles and geometry of our system and investigate the impact of varying working distance. Preliminary results show that the non-contact DRS system detects signatures of oxygenated hemoglobin in DRS measurements from human tissue and was sensitive to changes in spectral absorption in phantoms.
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