Holography and interferometry in photoelasticity

A physical explanation of photoelastic interferometry and holography is presented. Reasons for special properties and specific restrictions are argued in relation to this physical picture. The controlling intensity relationships for interferometry and holography are derived by simple physical analysis. The relationship between absolute retardation, isochromatic- and isopachic-fringe systems is clarified. Model material requirements for photoelastic interferometry and holography are shown to be identical.1971 William M. Murray Lecture was presented at 1971 SESA Fall Meeting held in Milwaukee, Wisc., On October 19–22.