1. A method of sorting articles that are moved past an inspection zone, comprising: illuminating the articles in the inspection zone with visible and infrared radiation; sensing the visible and infrared radiation reflected from the articles in the inspection zone and generating visible and infrared image data; extracting feature data from the visible and infrared image data; classifying the feature data into class categories; and separating the articles into acceptable articles and unacceptable articles in response to the class categories.