Optical paper sorter

Abstract

An optical paper sorter that uses diffuse reflectance to identify a sheet of paper as either white or non-white. An illuminating fiber optic bundle carries light from a tungsten halogen lamp onto a sheet of paper. A receiving trifurcated fiber optic bundle collects light that is diffusely reflected from the sheet of paper. The light in each branch of the receiving fiber bundle is incident upon a detector after passing through a color filter positioned between the end of the fiber bundle and the detector. At each detector a specific isolated color (blue, green or red) in the visible range of the electromagnetic spectrum is incident, causing a photo electric voltage to be produced that is proportional to the intensity of the isolated component. A processor uses the mean and standard deviation of relative reflectances that are obtained based on the three voltage signals to determine if the paper is predominantly white or non-white. An air ejection device can be triggered to release a blast of air upon identifying the paper as white, or alternatively, non-white.

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