Phase extraction from electronic speckle pattern interferometry addition fringes

An Improved Large-Field Microscopic Speckle Interferometry System for Dynamic Displacement Measurement of MEMS

The traditional microscopic speckle interferometer has limited applications in engineering due to its small field of view. In this paper, we propose a large-field microscopic speckle interferometer which embeds two doublet lens groups in the improved Mach–Zehnder optical path structure to expand its field of view. At the same time, the new system can reduce the coherent noise of reflected light in the optical path. We use this new system to measure the dynamic displacement process of the entire surface of the microchips. The experimental results show that our improved measurement system can achieve large-field, real-time and high-precision dynamic measurement of micro-electromechanical systems (MEMS).

One-shot phase stepping with a pulsed laser and modulation of polarization: application to speckle interferometry

For applications involving time varying optical phase distributions, fast cameras and/or pulsed lasers have to be used. To apply phase-shifting interferometry techniques (PSI) as well, single shot capture is required. Among others, modulation of polarization and phase grating interferometry is a possible technique to be considered. In this paper, a report about the use of this technique based on a double pulse laser system is presented. Single-pulse and twin-pulse operations are considered both in optical interferometers as well as in ESPI systems (mainly in subtraction mode). In ESPI a reduction of the degree of polarization appears due to scattering, so some measures have to be taken to prevent such deletereous effect. To show the feasibility of the proposed variants some experimental results are presented.

Multiplicative electronic speckle-pattern interferometry fringes

A theoretical analysis of fringe patterns and its experimental corroboration obtained by multiplication of two speckled images with electronic speckle-pattern interferometry (ESPI) are reported. A specifically designed digital filter is used to enhance the contrast and visibility of the inherently noisy multiplication fringes. Phase retrieval is achieved by a phase-stepping technique. Experimental results are presented for the in-plane-sensitive optical ESPI setup; however, out-of-plane and shearing setups may be used as well. The method represents an alternative to the subtraction and addition techniques in ESPI.