Abstract

Time-average interferometry of vibrating structures was introduced by Powell and Stetson in 1965.¹ At that time, however, the only high-quality holographic recording media that were available were of the conventional type, which required cumbersome chemical processing techniques. This shortcoming was alleviated by Butters and Leendcrtz² in 1971 when they introduced electronic speckle pattern interferometry (or ESPI) in which the fringes were recorded directly on a video camera.

© 1993 Optical Society of America