Abstract
This work explores the effect of the ill-posed problem on uncertainty quantification for motion estimation using digital image correlation (DIC) (Sutton et al. [2009]). We develop a correction factor for standard uncertainty estimates based on the cosine of the angle between the true motion and the image gradients, in an integral sense over a subregion of the image. This correction factor accounts for variability in the DIC solution previously unaccounted for when considering only image noise, interpolation bias, contrast, and the software settings such as subset size and spacing.
Similar content being viewed by others
Notes
Note, there are subtle differences between our definition of the cosine of the angle here and that used in the classical definition. Our modification is based on needing to represent only the acute angle between the two vectors. As we discuss in a subsequent section, if the motion points in the direction opposite the image gradient no loss of generality occurs.
In the DIC literature, this function is often written as G(x + u,t) − F(x)where G and F are the deformed and reference images, respectively. There are many normalized varieties of this equation such as the sum-squared-differences, zero-normalized-sum-squared-differences, etc.
We have intentionally presented the DIC problem in abstract form because the analysis that follows applies to both local and global formulations. A local, subset-based approach is used in the numerical examples to simplify the presentation. One can expect similar results for a global formulation, although this is not investigated here.
Empirical evidence suggests that this angle is small. Were it not, DIC could not be used so successfully in so many application areas.
We do not explicitly include the interpolation bias in the estimator above because the resulting error is small in comparison to the effects of noise and motion orientation.
This directional pattern is far from acceptable for use in real DIC applications. We use it here simply to highlight the connection between directionality and error in the DIC solution.
The specific details of the loading rate, specimen geometry, material type, and sample preparation are not of interest in this example and are therefore intentionally omitted.
References
Sutton MA, Orteu JJ, Schreier H (2009) Image correlation for shape, motion and deformation measurements: basic concepts, theory and applications. Springer, New York
Baker S, Matthews I (2004) Lucas-kanade 20 years on: a unifying framework. Int J Comput Vis 56:221–255
Bruhn A, Weickert J, Schnörr C (2005) Lucas/kanade meets horn/schunck: combining local and global optic flow methods. Int J Comput Vis 61:211–231
Ito K, Kunisch K (1997) Estimation of the convection coefficient in elliptic equations. Inverse Problems 13:995–1013
Lehoucq RB, Turner DZ, Garavito-garzón CA (2015) PDE-constrained optimization for digital image correlation SAND-2015-8515
Schnörr C (1991) Determining optical flow for irregular domains by minimizing quadratic functionals of a certain class. Int J Comput Vis 6:25–38
Weickert J, Schnörr C (2001) A theoretical framework for convex regularizers in pde-based computation of image motion. Int J Comput Vis 45:245–264
Horn BK, Schunck BG (1981) Determining optical flow. In: 1981 technical symposium east, international society for optics and photonics, pp 319–331
Ke XD, Schreier HW, Sutton MA, Wang YQ (2011) Error assessment in stereo-based deformation measurements, Part II: experimental validation of uncertainty and bias estimates. Exp Mech 51:423–441
Wang YQ, Sutton MA, Bruck HA, Schreier HW (2009) Quantitative error assessment in pattern matching: effects of intensity pattern noise, interpolation, strain and image contrast on motion measurements. Strain 45:160–178
Wang ZY, Li HQ, Tong JW, Ruan J (2007) Statistical analysis of the effect of intensity pattern noise on the displacement measurement precision of digital image correlation usingself-correlated images. Exp Mech 47:701–707
Wang Y, Lava P, Reu P, Debruyne D (2016) Theoretical analysis on the measurement errors of local 2D DIC: part I temporal and spatial uncertainty quantification of displacement measurements. Strain 52:110–128
Bornert M, Brmand F, Doumalin P, Dupr JC, Fazzini M, Grdiac M, Hild F, Mistou S, Molimard J, Orteu JJ, Robert L, Surrel, Y, Vacher P, Wattrisse B (2009) Assessment of digital image correlation measurement errors: methodology and results. Exp Mech 49:353–370
Schreier HW, Sutton MA (2002) Systematic erros in digital image correlation due to undermatched subset shape functions. Exp Mech 43:303–311
Schreier HW, Braasch JR, Sutton MA (2000) Systematic erros in digital image correlation caused by intensity interpolation. Opt Eng 39:2915–2921
Lecompt D, Smits A, Bossuyt S, Sol H, Vantomme J, Hemelrijck DV, Habraken AM (2006) Quality assessment of speckle patterns for digital image correlation. Opt Lasers Eng 44:1132–1145
Rossi M, Lava P, Pierron F, Debruyne D, Sasso M (2015) Effect of DIC spatial resolution, noise and interpolation bias error on identification results with VFM. Strain 51:206–222
Reu PL, Sweatt W, Miller T, Fleming D (2015) Camera system resolution and its influence on digital image correlation. Exp Mech 55:9–25
Amiot F, Bornert M, Doumalin P, Dupre JC, Fazzini M, Orteu JJ, Poilane C, Robert L, Rotinat R, Toussaint E, Wattrisse B, Wienin JS (2013) Assessment of digital image correlation measurement accuracy in the ultimate error regime: main results of a collaborative benchmark. Strain 49:483–496
Madsen K, Nielsen HB, Tingleff O (2004) Methods for non-linear least squares problems. Informatics and Mathematical Modelling, Technical University of Denmark, pp 1–58
Immerkaer J (1996) Fast noise variance estimation. Comput Vis Image Underst 64:300–302
Keys R (1981) Cubic convolution interpolation for digital image processing. IEEE Trans Acoust Speech Signal Process 29:1153–1160
Lucas BD, Kanade T et al (1981) An iterative image registration technique with an application to stereo vision. IJCAI 81:674–679
Bomarito GF, Hochhalter JD, Ruggles TJ, Cannon AH (2017) Increasing accuracy and precision of digital image correlation through pattern optimization. Opt Lasers Eng 91:73–85
Pan B, Lu Z, Xie H (2010) Mean intensity gradient: an effective global parameter for quality assessment of the speckle patterns used in digitial image correlation. Opt Lasers Eng 48:469–477
Reu P, Wattrisse B, Wang W, Robert L, Bruck H, Daly S, Rodriguez-Vera R, Bugarin F (2014) Society for Experimental mechanics: digital image correlation (DIC) challenge Web page. http://www.sem.org/dic-challenge/
Author information
Authors and Affiliations
Corresponding author
Additional information
This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
Appendix
Appendix
All symbols used in this work are defined in Table 5.
Rights and permissions
About this article
Cite this article
Lehoucq, R.B., Reu, P.L. & Turner, D.Z. The Effect of the Ill-posed Problem on Quantitative Error Assessment in Digital Image Correlation. Exp Mech 61, 609–621 (2021). https://doi.org/10.1007/s11340-017-0360-5
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11340-017-0360-5