An electronic speckle pattern interferometer for complete in-plane displacement measurement

Abstract

Measurement of plane-strain surface displacement with ESPI requires at least two in-plane illumination geometries. For static loading conditions it is acceptable to record these two interferograms sequentially. However, for time-dependent strain fields, it is necessary to use both illumination geometries simultaneously so that a recording is made with identical strain conditions existing for both. The authors describe a new interferometer that has been devised to measure two in-plane interferograms at the same time. The determination of the method of operation and experimental verification of the technique are given.

Modified in-plane electronic speckle pattern shearing interferometry (ESPSI)

“…Then each beam exiting the beam splitting cube should contain the shearing unit and own CCD camera. As explained in [16] a single viewing (imaging) optics should be used before the beam splitter to provide pixel by pixel correspondence of the same object points. Below we would like to present the principle of another approach to determine the surface slope of a specimen under test in the in-plane displacement detection configuration.…”

“…Note that all polarized light based systems, including the ones to measure two inplane interferograms at the same time [16], (twochannel system for registering shear type interferograms for orthogonal directions can be readily proposed along the lines presented in [16]) require the polarization state preserving surface ofthe object on reflection.…”

Uncertainty analysis using Monte Carlo method in the measurement of phase by ESPI

“…The principle of ESPI has been discussed extensively in other publications [1,2]; and used to measure two-dimensional displacements in event no dynamics [3,4] and dynamics [5,6]. In the interferometric speckle pattern the intensity of the light contains information on the optical phase and hence on the optical path length difference between the two paths through the interferometer.…”

“…Two fringe patterns corresponding to two components of the in-plane displacement were recorded simultaneously by two CCD cameras [5]; however, it is a little difficult to do so. Two fringe patterns corresponding to two components of the in-plane displacement were recorded simultaneously by two CCD cameras [5]; however, it is a little difficult to do so.…”

Residual stress measurement using a radial in-plane speckle interferometer and laser annealing: preliminary results

“…Even though some DSPI systems based on polarization discrimination methods were developed for this purpose, 10,11 this approach has two drawbacks: (a) the test surface can appreciably depolarize the two orthogonalpolarized dual-beam illumination sets causing cross interference between them; (b) the optical setup becomes more bulky and complex. A step forward to solve these problems was recently given by Albertazzi et al 12 with the development of a novel double illumination DSPI system to measure radial in-plane displacements.…”