Color Encoded Moire Contouring

Kevin G. Harding; Michael P. Coletta; Carl H. VanDommelen

doi:10.1117/12.949042

7 March 1989 Color Encoded Moire Contouring

Kevin G. Harding, Michael P. Coletta, Carl H. VanDommelen

Proceedings Volume 1005, Optics, Illumination, and Image Sensing for Machine Vision III; (1989) https://doi.org/10.1117/12.949042
Event: 1988 Cambridge Symposium on Advances in Intelligent Robotics Systems, 1988, Boston, MA, United States

Abstract

One of the more prevalent applications of moire is contouring of parts. Some of the techniques available to generate contour data include phase shifting, fringe center mapping and frequency shifting. These techniques rely heavily on both extensive software analysis and rigorous hardware manipulation to produce different moire patterns of the same object. For example, frequency shifted moire requires that the grating frequency be changed in each of three of four successive images of the pattern. Phase shifted moire requires that the grating be changed in phase between successive images. This is done by physically moving the grating or moving it within software. In general, these techniques suffer from a lack of robustness. Taking multiple images with the hardware uses valuable time, during which the part may actually move and thereby distort the data. Any vibrations of the parts during data taking may also present a problem with extended amounts of inspection time. If the image is changed in the software, then the system can be fooled into interpreting reflectivity and illumination variations as moire pattern data. It is difficult to get a fast and accurate contour of a part in a real world environment with the present techniques available. There have, however, been advances in the video and machine vision industry that allow for the use of new tools, such as color. This paper describes work directed toward using color to improve existing contouring techniques. The goal is to develop a means to obtain a one time snapshot of the part under inspection that gives all of the necessary information required to produce a contour. This paper will address issues such as performance of color cameras, fabrication of color gratings, and use of a dichroic, multicamer'd system, contrasted with a multi-grating, multi-color illumination system.

Citation Download Citation

Kevin G. Harding, Michael P. Coletta, and Carl H. VanDommelen "Color Encoded Moire Contouring", Proc. SPIE 1005, Optics, Illumination, and Image Sensing for Machine Vision III, (7 March 1989); https://doi.org/10.1117/12.949042

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