Using a heterodyne interferometer of unique design, high precision measurements of optical surfaces while undergoing deformation have been obtained. The device is described and results of various investigations are presented.
N. A. Massie,
"Quasi-Real-Time High Precision Interferometric Measurements Of Deforming Surfaces", Proc. SPIE 0153, Advances in Optical Metrology I, (15 December 1978); doi: 10.1117/12.938227; https://doi.org/10.1117/12.938227