Systematic errors of a projection-moire contouring system

Projection moire techniques are useful tools for the determination of surface contour features. They can provide interferometric type fringe patterns showing regions of equal height on the surface. The difference between moire and interferometry appears in the spacing of the equal height contours lines. In an interferometric fringe pattern, the height difference between consecutive fringes is equal to the wavelength of the illumination source and is a constant over the entire pattern. For a projection moire contour pattern the height difference between consecutive fringes is determined by illumination geometry parameters and is not constant; it changes as a function of the object's out of plane height. This variation in fringe spacing causes a misrepresentation of the surface's shape if the pattern is analyzed as a traditional interferogram. This paper discusses the types of aberrations generated by this process and the dependence of aberrations on the geometry of the object.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.