Automation of white light photoelasticity by phase-shifting technique using colour image processing hardware

The early application of the digital image processing (DIP) technique to automate photoelastic analysis is based on black and white image processing systems. The various methodologies reported can be said to rely upon one or more features of a black and white DIP system. With the 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, green and blue. This paper investigates whether one or all of the image planes can 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 then 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 compared with theoretical predictions: the comparison is found to be good.