AUTOMATION OF WHITE-LIGHT PHOTOELASTICITY BY PHASE-SHIFTING TECHNIQUEUSING COLOR IMAGE-PROCESSING HARDWARE

The early application of the digital image processing (DIP) technique to automate photoelastic analysis is based on black and white image pr ocessing systems. The various methodologies reported carl be said to r ely upon one or more features of a black and white DIP system. With th e advancements in computer technology, modern colour image processing systems are available at affordable prices. In such systems, the image is identified as a superposition of image planes of red, gr een and b lue. This paper investigates whether one or all of the image planes ca n be thought of as behaving like an optical filter: with the hardware used, the green channel is found to behave in this way. This idea is t hen used to extend the phase-shifting technique to colour domain. For the problem of a disk under diametral compression, total fringe order variation along a few lines is evaluated by this new technique and com pared with theoretical predictions: the comparison is found to be good . (C) 1997 Elsevier Science Ltd.