We present a new laser method that exploits curved-ray effects and that provides a practical method to investigate the stress profile in tempered glass. A feature of the technique is that the probing laser beam curves sufficiently that it exits on the same side as it enters; it does not reflect off or exit from the opposite side. The governing equations are formulated and studied using analytical methods and computer simulations. For a typical piece of tempered glass, the distance between the entry and exit points is of the order of a few tens of centimeters and is highly sensitive to details of the underlying stress distribution.
G. Wayne Brodland,
"Curved-ray technique to measure the stress profile in tempered glass," Optical Engineering 39(9), (1 September 2000). https://doi.org/10.1117/1.1287935