Genesis of Various Optical Arrangements of Circular Polariscope in Digital Photoelasticity

Abstract

In the early developments for automation of photoelasticity several researchers have proposed phase shifting techniques (PST) with different optical arrangements. Several ways of calculating the isoclinic and isochromatic parameters were also reported. In many cases though the optical arrangements were different, the intensity equations remained the same. Although theoretically, each of the techniques provide the evaluation of isoclinics and isochromatics, when applied to experimental images only some of the techniques remain robust. This indicates that specific optical arrangements do play a very important role on the success of the phase shifting technique experimentally. One of the main sources of error is due to the mismatch of quarter wave plate. In this paper, the role of quarter wave plates in influencing the selection of appropriate optical arrangement for PST is studied systematically. Different possibilities of obtaining the photoelastic parameters with least error are explored.