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As I write this article, it is autumn, 1979. Fifteen years ago, at this time of the year, Robert L. Powell and I performed some experiments at the Institute of Science and Technology (as it then was) at the University of Michigan, in the Radar and Optics Laboratory under Emmett Leith. Our contract objective was to study holograms for their potential in aerial photography; however, in practice we were trying to find out why, of all the holograms recorded of a three dimensional object, one was excellent and the rest were poor. In the course of our experiments we noticed certain characteristics of "bad" holograms and sought to investigate these defects. The result was the discovery of hologram interferometry.