Fast Detection of Geometry Defects on Free-Form Surfaces Using Inverse Fringe Projection

Abstract

Complex geometries are present in practically all modern machines. Collaborative Research Center 871, “Regeneration of Complex Durable Goods,” focuses on the research and development of regeneration techniques for valuable, complex-shaped goods such as turbine blades and windpower airfoils. Wherever free-form workpieces are relevant for safe and economic function of the machine, three-dimensional geometry checking is a crucial step in manufacturing and regeneration of those goods. Fringe projection (FP) has evolved as a fast and technique for three-dimensional geometric measurements of technical workpieces. The primary uses of the FP technique cover reconstruction of unknown surface geometries, i.e. reverseengineering, as well as geometry verification, i.e., workpiece quality assessment. In our previous work1 we introduced the inverse fringe projection (iFP) principle for inherently fast measurement of geometry defects. In this article, we focus on the realization of an iFP system and depict methods for system calibration and defect detection on real workpieces. 10 THE JOURNAL OF THE CMSC/SPRING 2013 In the first section of this article, we briefly recall the setup of a conventional fringe-projection system and subsequently derive the iFP approach. After that, we explain the mathematical system model as well as our corresponding calibration procedure. Measurement results of real workpieces are used as exemplary data sets for the description of automated inspection algorithms.