New method for piezooptic coefficients measurements based on four-point bending

A new technique is suggested for determination of piezooptic coefficients, which represents a combination of digital imaging laser interferometry and a canonical four-point bending method. The design of interferometer, measurement procedures, and data processing are described in detail. Potentials of the present technique are tested on the example of widely used optical borosilicate glass BK7. High enough precision, together with unambiguity in determination of the sign of both piezooptic (πqm) and photoelastic (pqm) coefficients, allow us to claim it to be one of the most accurate and reliable techniques for the measurements of pqm and pqm parameters.