Diffuse reflectance measurements using lensless CMOS imaging chip

To assess superficial epithelial microcirculation, a diagnostic tool should be able to detect the heterogeneity of microvasculature, and to monitor qualitative derangement of perfusion in a diseased condition. Employing a lensless CMOS imaging chip with an RGB Bayer filter, experiments were conducted with a microfluidic platform to obtain diffuse reflectance maps. Haemoglobin (Hb) solution (160 g/l) was injected in the periodic channels (grooves) of the microfluidic phantom which were covered with ~250 μm thick layer of intralipid to obtain a diffusive environment. Image processing was performed on data acquired on the surface of the phantom to evaluate the diffuse reflectance from the subsurface periodic pattern. Thickness of the microfluidic grooves, the wavelength dependent contrast between Hb and the background, and effective periodicity of the grooves were evaluated. Results demonstrate that a lens-less CMOS camera is capable of capturing images of subsurface structures with large field of view.