Differential reflectivity method and apparatus for sorting

Abstract

Sorting apparatus and method comprise a viewing area, a removal area, and a conveyor for passing a thin bed of indiscriminately mixed items first through the viewing area and then through the removal area. Radiant energy, which includes bands of two mutually different wavelengths that are reflected in a predetermined relationship by some of the items and in other than that relationship by the other items in the mixture, is flooded into the viewing area as an integrated spread throughout the area from preferably special light fixtures producing both visible light and infrared radiation. A dual diode array, scanning camera has its paired diodes focused, respectively, on contiguous sub-areas of the viewing area across the width of the bed, so the diodes of each pair will sense the different energy wavelengths, respectively, reflected from the corresponding sub-area of the viewing area and so the comparison circuitry of the camera will produce resultant data signals for those diode pairs for which the sensed relationship is the predetermined one. Any resultant data signals are sent to control circuitry arranged to activate corresponding ones of a plurality of devices for removing from the bed as it passes through the removal area, width portions thereof corresponding to the widths and locations of corresponding predetermined pluralities of the sub-areas of the viewing area.