Experimental verification of full-field accuracy in stereo-DIC based on the ESPI method

Abstract

This paper proposes a method to merge stereo-digital image correlation (DIC) and electronic speckle pattern interferometry (ESPI) data by camera calibration. The proposed method is employed to verify the accuracy of full-field out-of-plate displacements measured by stereo-DIC in a cantilever beam test. The mean absolute error and the root mean square error (RMSE) of the full-field displacement measured by four-megapixel cameras are 0.849 µm and 1.08 µm at 60 mm field of view, respectively, and the RMSE of the central area is 0.615 µm. The errors are not uniformly distributed because of the imperfect calibration. When the lenses are changed and the field of view reaches 120 mm, the RMSE is 1.48 µm with uniform distribution. These accuracies could be traced back to the laser wavelength to confirm the stereo-DIC data. The proposed method can be used not only to verify the full-field measurement accuracy of DIC but also to determine the rigid-body displacement for ESPI with a high-precision stereo-DIC. Thus, the displacement vector can be obtained. Furthermore, it can unify the coordinate of multiple ESPI systems to achieve a large range of high-precision three-dimensional deformation measurements.

An Error Estimation System for Close-Range Photogrammetric Systems and Algorithms

“…Another possibility is a direct comparison of the measurement results of the method under test with those of another method, e.g., ref. [ 33 ]. However, usually, only one or several measured objects are used, and it is impossible to estimate the full error by comparing them.…”

“…In [ 32 ], the theoretical and experimental error estimation of the Digital Image Correlation (DIC) method for the angle between the cameras of a stereo system is given. An experimental comparison of stereophotogrammetric and interferometric measurement results is given in [ 33 ]. It is also worth mentioning experimental studies on the accuracy of industrially produced RGB-D cameras [ 34 , 35 ], which have recently been widely used in various fields ranging from medicine to security.…”