Electronic speckle pattern interferometry
Electronic Speckle Pattern Interferometry (ESPI)[1], also known as TV Holography, is a technique which uses laser light, together with video detection, recording and processing to visualise static and dynamic displacement of components with optically rough surfaces. The visualisation is in the form of fringes on the image where each fringe nromally represent a displacement of half a wavelength of the light used (i.e quarter of a micron or so).
- ^ Jones R & Wykes C, Holographic and Speckle Interferometry, 1989, Cambridge University Press