We have developed an automated technique for interferogram interpretation using a PDP-12 minicomputer, Cohu television camera and Hughes scan converter. A digitized image of the interferogram is stored on disc, and a small area is read into central memory. The fringe density in that region is estimated based on the number of peaks found in several line scans across the area under study. This calculation is repeated for successive small areas until a map of fringe density covering the entire part is compiled. If the fringe density map falls within an acceptance profile, the part is accepted. Experimental results demonstrate that this technique works well on interferograms having substantial variations in intensity and fringe contrast.
D. A. Tichenor,
V. P. Madsen,
"Computer Analysis Of Holographic Interferograms For Nondestructive Testing," Optical Engineering 18(5), 185469 (1 October 1979). https://doi.org/10.1117/12.7972413