Fast large-area low-cost two-dimensional optical position sensor

A novel two dimensional optical position sensor based on confinement of luminescence within a flat panel is described. The basis of the sensor is a flat luminescent panel, such as those used in luminescent solar energy concentrators. In these concentrators, a glass or plastic plate is either coated or impregnated with a fluorescent material. The incident radiation produces luminescent emission, much of which is confined within the plate through total internal reflection, and is thus guided to solar cells which line the thin edges of the plate. In order to use such plates as a position sensor, four photodiodes are placed along two orthogonal axes at the edges of the plate, and the plate is illuminated with a spot of light. The spot of light induces luminescence, which is detected by the four photodiodes. The photodiodes' output is processed to provide position information. Large area position sensors based on the above idea were constructed, using fluorescent plexiglass which was obtained from commonly available fluorescent clipboards. The photodiode output was combined using a self-normalizing function to eliminate sensitivity to non-uniformity in the optical characteristics of the fluorescent plates. This paper presents the results obtained to date, together with suggestions for further improvement in the sensor based on these results.