COMPARATIVE PERFORMANCE EVALUATION OF VARIOUS FRINGE THINNING ALGORITHMS IN PHOTOMECHANICS

In recent years several algorithms have been reported for automating f ringe data collection in photomechanics using the technique of digital image processing (DIP). Recent advances in phase shifting interferome try have offered some hope for full automation of static problems. How ever, for real-time dynamic studies conventional recording of fringes is a must. Fringe thinning is a very crucial step in extracting data f or further processing. The various DIP algorithms for fringe thinning are surveyed and an attempt is made to explain better the mechanism of fringe skeleton extraction by various algorithms. The algorithm of Ra mesh and Pramod is improved to extract fringe skeletons from saddle po ints in the fringe field. A comparative performance evaluation of thes e algorithms is discussed with respect to the quality and accuracy of fringe skeleton extracted and the processing time. Performance evaluat ion is done on a few computer-generated test images and also on images recorded by the technique of photoelasticity. The improved version of the algorithm of Ramesh and Pramod is found to give better fringe ske letons, it is also the fastest and the processing time is an order of magnitude less than the other algorithms. If is proposed that these co mputer-generated test images could be used as standard test images for checking the performance of any new fringe thinning algorithm.