Digital Fringe Reduction Techniques Applied To The Measurement Of Three-Dimensional Transonic Flow Fields

Abstract : A system for digital interferogram evaluation based on an image- processing system connected to a host computer has been implemented. The system supports one- and two-dimensional interferogram evaluations. Interferograms are digitized, enhanced, and segmented. The fringe coordinates are extracted, and the fringes are represented as polygon data structures. Fringe numbering and fringe interpolation modules are implemented. The system supports editing and interactive features as well as graphic visualization. An application of the system to the evaluation of double exposure interferograms from the transonic flow field around a helicopter blade and the reconstruction of the 3-D flow field are given. Subject terms: image and hologram data reduction; automatic fringe analysis; interferometry; digital image processing; transonic flows; holographic techniques. Reprints.