High-Resolution Shape Measurements by Fringe Projection and Reflectance Transformation Imaging

Abstract

In this paper, we consider the advantages and limitations of two existing techniques: structured light fringe projection (FP) and reflectance transformation imaging (RTI), and we propose a new hybrid shape measurement approach that combines their advantages. FP allows direct full field-of-view measurements of shape; however, due to the nature of the technique, the high frequency shape details of the object may not be captured. RTI is a recently developed technique that allows high resolution measurements of surface normal vectors, which are related to high frequency details of shape of the object; however, extracting the object shape from RTI data requires numerical integration, which leads to cumulative low frequency bias errors. We present representative results that demonstrate the ability of our approach to perform high resolution shape measurements and non-destructive testing of structures.