Three-dimensional inspection using laser-based dynamic fringe projection

This paper initially describes the principles of laser-based dynamic fringe projection techniques, and more specifically, how these techniques have been exploited in the Dynamic Automated Range Transducer (DART). This instrument employs novel techniques to produce a high accuracy single point range measurement over a wide variety of distances. The latest miniature optical components lend themselves to the production of a small, low-cost, self-contained device, which is easily portable and suitable for use in on-line, automated inspection systems, or in the field. The development of the DART for three- dimensional measurements is described. Two methods are possible, either a single beam or twin-beam system. Using a CCD photodiode array with precise pixel geometry an accurate three dimensional mapping of an object can be achieved. The problems of processing the data from the various DART systems is briefly examined. For multi-pixel measurements a parallel architecture using fast digital signal processing devices is recommended.