Inspection of machine parts by backprojection reconstruction

Extraction of 3D information from 2D views is an important problem in the inspection of manufactured parts. Inspection for defects and correctness of shape and size requires accurate 3D information. In this paper we present a method for 3D reconstruction by backprojection of 2D views. This method uses readily available passive imaging sensors and a computer-controlled positioner to directly produce a 3D reconstruction of the part. Consistency based processing is introduced as a method of increasing reconstruction accuracy by exploiting redundant data in the multiple images. Maximum effciency and accuracy in reconstruction is achieved using optimal view patterns and reliable silhouette extraction techniques. Although this method is applicable to the inspection of general machine parts, our immediate application was in the inspection of laser-drilled rivet holes and laser-drilled cooling holes in jet engine turbine blades.