Large in-plane displacement measurement in dual-beam speckle interferometry using temporal phase measurement

Fringe Pattern Analysis in Wavelet Domain

“…The popularity of the technique, in optical metrology, is by virtue of the several advantages it offers such as: it is a non-contact/ invasive type technique; it provides full-field of view information; it is faster in operation as almost real-time observations can be obtained; investigations on largesize objects can be observed with the use of proper optics, and the technique is less sensitive to environmental perturbations in comparison with its counterparts. The DSPI technique has proven its capability in many investigations, e.g., for the measurement of displacement/deformation with variable sensitivity to in-plane and out-of-plane direction [22][23][24][25][26][27], measurement of three-dimensional shape [28][29][30], surface roughness measurement [31], vibration measurement/monitoring [32][33][34], measurement of material properties [35][36][37], flow visualization [38,39], measurement of refractive index and temperature distribution [40][41][42], and the investigation of the magnetic fields on the temperature profile of gaseous flames [43,44]. A Doctoral Thesis describing the comprehensive study of DSPI and some of its novel investigations is recommended for interested readers working in this field [48].…”

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

“…However, the signal modulation was consistently found to be low but always higher than in the case of two speckles in one pixel. Pixels where the signal modulation is close to the quantization level of the camera used will produce no data and usually has been eliminated in our analysis by using a spike only type filter (spike filter) [5][6][7][8].…”

“…Recently we proposed an alternate method of obtaining information about the object deformation using a method called temporal phase evaluation in speckle interferometry (TSPI) using Fourier transformation methods [5]. This basic principle of the method was then extended to measure slope of the object deformation using temporal Fourier transform speckle pattern shearing interferometry (TSPSI) [6], in-plane motion using dual beam illumination [7] and shape of an object using dual beam illumination [8]. In all these methods, a point on the object is observed over time as the object is being continuously deformed or rotated or the wavelength changed continuously.…”

Towards high-speed optical measurement of shape and deformation

“…Transform-based methods [68][69][70][71][72][73][74][75] are able to retrieve the ϕ(x, y; t) from a single fringe pattern, however, this method requires either a temporal or a spatial carrier to separate the spectrum of the fringe pattern in the frequency domain. For example, at time t = t 0 , a carrier fringe pattern can be written as The significant disadvantage of transform-based methods, however, is that the introduction of a temporal carrier limits the measurement range.…”

“…the Fourier transform [68][69][70], the Hilbert transform [71,72], the temporal wavelet transform [73,74], and the windowed Fourier transform (WFT) [75], can extract the phase distribution from a single fringe of speckle pattern. However, the measurement range is limited by the introduction of carriers.…”