1. A biometric feature detection system comprising: a target including a target surface configured to receive a biometric feature at the target surface; an illumination source configured to illuminate at least a portion of a target surface from below the target surface with monochromatic blue light at a large angle of incidence measured from the normal of the target surface; a color filter array comprising a plurality of color mosaics arrayed across the color filter array; a light detector configured to receive light from the target through the color-filter array and provide an image of the target surface, wherein each pixel of the light detector corresponds to one of the plurality of color mosaics such that each pixel detects light associated with corresponding color filter; and a computational unit interfaced with the light detector, wherein the computation unit includes instructions to monitor the levels of blue light and compute a mathematical function on the levels of blue light in proportion with levels of other light.