Shearing interferometric techniques that can provide information about the stress or deformation states of non-birefringent transparent materials and opaque specularly reflective materials are described. Two types of coherent shearing interferometers that provide full-field information about the gradients of the stress state of an object are discussed. These techniques have recently found use in stress analysis, especially in experimental fracture mechanics studies. In addition, a simpler technique called the method of caustics which is also applicable to non-birefringent materials is described in brief. This technique does not provide full-field information but has been of historical interest in experimental fracture mechanics. Examples of application of all three techniques are given.
Krishnaswamy, S. (2007). Techniques for Non-Birefringent Objects: Coherent Shearing Interferometry and Caustics. In Photomechanics (pp. 295–321). Springer Berlin Heidelberg. https://doi.org/10.1007/3-540-48800-6_9