Patent US 4,166,540

An automatic document sorter particularly suitable for sorting retail store coupons employs a plurality of relatively coarse sorting processes in cascade. The sorting processes sequentially sort the documents according to predetermined properties of the document, including codes, such as bar codes or the like; physical properties, such as size, thickness, color, reflectivity and opacity; the characteristics of the inscriptions on the face of the document; and any uniquely marked areas of the document face. Such a sorting hierarchy permits the documents to be sorted rapidly by reducing the precision required in each sorting step. The hierarchy also permits each document to be classified during each sorting step as falling into a particular class of documents in order to simplify subsequent sorting steps. If a property uniquely identifying the document is found during any one of the sorting steps, the processing is terminated at that point without completing the subsequent sorting steps.