In-Plane Displacement Measurement Using Digital Image Correlation with Lens Distortion Correction

Abstract

Two-dimensional displacement measurement using digital image correlation with lens distortion correction is described in this paper. A single cross-grating is used as a calibration reference. Using two-dimensional Fourier transform, the phases of the grating pattern are analyzed and lens distortion distribution is obtained from the unwrapped phase maps. After detecting lens distortion, the coefficients of lens distortion are determined using the least-squares method. Then, the displacement distributions without the lens distortion are obtained. The effectiveness of the method is demonstrated by applying the proposed method to the rigid body translation test and the uniaxial tension test. The results show that the proposed distortion correction method removes the effect of lens distortion from the measured displacements. By the proposed method, accurate measurements can be performed even if images are deformed by lens distortion.

Nanoscale displacement measurement of electrostatically actuated micro-devices using optical microscopy and digital image correlation

“…Optical imaging drifts, on the other hand, are of unidirectional nature and are not affected by electric fields and scanning time (all pixels are sampled simultaneously). Moreover, in high quality optics, radial distortions are negligible [57].…”

“…Images were processed on a computer (Intel(R) Core(TM) 2 CPU 2.4 GHz, 2 GHz of RAM) using MATLAB 7.4.0 (R2007a) software. Radial image distortions [57] can be neglected in the current study since a high quality lens was used. In addition, even if some radial distortions exist, they have negligible influence since the ROI was placed far from the image edges.…”

The state of the art of two‐dimensional digital image correlation computational method

“…Lava et al emphasized the negative effects of lens distortions on the determination of large strain gradients fields at microstrain scales (≤1000 um/m), and implied the necessity of camera calibration and distortion compensation for the precise acquisition. To deal with the problem of image distortion to restore fidelity image, several proved approaches in connection with 2D‐DIC systems have been presented . In 2014, Dufour et al developed a novel method that incorporates the integrated DIC into extracting the parametric description of the distortion fields.…”

Centrosymmetric 3D Deformation Measurement using Grid Method with a Single-Camera

“…Imaging distortion caused by the imaging system error was always present no matter which imaging system was used, such as camera lens distortion in a CCD chip and nonlinear higher order distortion in SEM. Using a parametric distortion model can correct lens distortion [34]. Based on the non-parametric distortion model [35], a correction method for nonlinear higher order distortion terms using DIC metrology proposed by Sutton [10] and the secondary moiré method could effectively eliminate the imaging distortion in SEM.…”