A sensor system comprised of a diffuse light source and a sensor mounted on a transparent layer of material that is adjacent to a fluid. The refractive index of the transparent layer is greater than the refractive index of the fluid, causing a portion of the diffuse light source to be reflected from...http://www.google.com/patents/US7271883?utm_source=gb-gplus-sharePatent US7271883 - Refractive index sensor using internally reflective light beams
