Speckle interferometry with temporal phase evaluation: influence of decorrelation, speckle size, and nonlinearity of the camera

Abstract

Recently, a new method to measure object shape and deformation with temporal evolution of speckles in speckle interferometry was reported. In this method, certain parameters, sensitive to shape or deformation are changed continuously, and the fluctuations in the irradiance of each speckle is recorded. The information over the whole object deformation is retrieved by Fourier-transformation techniques. We present a detailed theory and analyze the influence of decorrelation due to longitudinal and lateral size of the speckles. It is also shown that the method can be used to measure small deformations (less than 5 microm) with higher resolution. Further, the nonlinearity of the camera is shown to enhance the sensitivity.

Interferometric Dynamic Measurement: Techniques Based on High-Speed Imaging or a Single Photodetector

“…In 1998, Joenathan et al performed a series of studies on temporal phase evaluation through speckle interferometry for out-of-plane deformation [36], in-plane deformation [37], the derivative of out-of-plane deformation [38], and the shape measurement [39]. The influence of decorrelation, speckle size, and nonlinearity of the camera were also discussed [40] and a rotating half-wave plate was proposed to introduce a temporal carrier. In 2002, Kaufmann and Galizzi compared the temporal phase-shifting method with the temporal Fourier transform method [41].…”

Widefield laser doppler velocimeter: development and theory.

“…This similarity has been noted in the literature by Briers in his paper [ 16 ] reconciling ESPI and LDV, as well as being briefly mentioned by Cloud in his book on optical methods [ 17 ] and implicitly understood by Joenathan in his papers on TSPI. [6][7][8] It seems desirable to the current authors to highlight the similarities and differences in the approach, to briefly derive the equations, and to reconcile the approaches in more detail than is contained in any of these references. For simplicity in illustrating both concepts, a Michelson interferometer arrangement, shown in Figure 1, is used for the discussion.…”

“…In the TSPI literature, a number of approaches are used to decode the time-varying irradiance of the pixels. Frequency-based methods are the most similar to Doppler velocimetry, [6][7][8][9] but re-curvature methods, [10] scanning phase methods, [11,12] and temporal branch-cut methods have also been utilized. [13,14] Another unique approach to obtain full-field velocity information is a system termed optically phase-locked ESPI.…”

Extended-range temporal electronic speckle pattern interferometry

“…Experimentally we will have some amount of speckle decorrelation that translates into a low-energy phase noise in the temporally sampled signal. 4 -8 Temporal fringe decorrelation can be kept under control as shown by Joenathan et al 9 whenever unwanted displacements to which the speckle interferometer is not sensitive, such as in plane displacement in out-of-plane sensitive interferometers, or out-of-plane displacement in in-plane sensitive interferometers, gives rise to decorrelation. If this warning is observed, one may have an extremely wide measurable dynamic range of as many as a few centimeters.…”

“…If this warning is observed, one may have an extremely wide measurable dynamic range of as many as a few centimeters. 9 Joenathan et al 9 were capable of obtaining 600 speckle temporal frames having ϳ85 temporal fringes with very little decorrelation. This means that the temporal fringe saving method exposed in this research can be used easily to reduce the temporal sampling demand of fast transient phenomena.…”