Electronic speckle pattern interferometry (ESPI), also known as TV Holography, is a technique which uses laser light, together with video detection, recording and processing to visualise static and dynamic displacements of components with optically rough surfaces. The visualisation is in the form of fringes on the image where each fringe normally represents a displacement of half a wavelength of the light used (i.e. quarter of a micrometre or so).
ESPI can be used for stress and strain measurement, vibration mode analysis and nondestructive testing.
ESPI is similar to holographic interferometry in many ways, but there are also significant differences between the two techniques.
Read more about Electronic Speckle Pattern Interferometry: How ESPI Works
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