Reverse engineering: high speed digitization of free-form surfaces by phase-shifting grating projection moire topography

Abstract

A new digitization method is presented for automatic acquisition of geometric information on free-form surfaces for the sake of reverse engineering. Principles of grating projection moire topography are utilized with emphasis on enhancing the measuring resolution by incorporating phase-shifting fringe analysis, The measuring range and resolution can be readily adjusted to suit the object size to be measured, simply by varying the spatial line pitch of the moire gratings. In addition, no time-consuming beam scanning is required in the measurement, keeping the measuring time relatively low as compared with other existing techniques. Experimental results demonstrate that the three-dimensional coordinate data of 640 X 480 points can be attained within 5 seconds run on an IBM PC 586, with measuring resolutions of 0.1 mm down to 0.001 mm. (C) 1998 Elsevier Science Ltd. All rights reserved.