Shadow moiré topography using a flatbed scanner

Abstract

Flatbed scanners are high-quality digital image recording devices that are cost-effective and widely available. In this work we demonstrate their ability to register shadow moiré fringes for topographic analysis. The fringe image obtained in color had bluish and greenish regions that correspond, respectively, to the bright and dark fringes associated with the technique. The diffraction characteristic of light passing through gratings provided a ready explanation of this behavior. The gray-scale fringe image, obtained via direct conversion of the color pattern, had rather poor contrast. Processing this gray-scale image produced only marginal improvements in contrast. The approach of separating the color image into its blue and green components, followed by gray-scale conversion, subtraction, and other processing operations, generated images with significantly higher contrast. © 2002 Society of Photo-Optical Instrumentation Engineers.