Systematic errors in digital image correlation caused by intensity interpolation

Abstract

Recently, digital image correlation as a tool for surface deformation measurements has found widespread use and acceptance in the field of experimental mechanics. The method is known to reconstruct displacements with subpixel accuracy that depends on various factors such as image quality, noise, and the correlation algorithm chosen. However, the systematic errors of the method have not been studied in detail. We address the systematic errors of the iterative spatial domain crosscorrelation algorithm caused by gray-value interpolation. We investigate the position-dependent bias in a numerical study and show that it can lead to apparent strains of the order of 40% of the actual strain level. Furthermore, we present methods to reduce this bias to acceptable levels.

Evaluating the mechanical behavior of arterial tissue using digital image correlation

“…The most common methods of interpolation in DIC are bilinear and bicubic interpolations, and reports have indicated that bicubic is more accurate than bilinear. 23,24 Materials and Methods…”

High Performance Digital Volume Correlation

“…In fact, as discussed in Schreier et al [71], interpolation can introduce a phase shift in the displacement, causing an artificial systematic error in the subsequent DVC results. For translation tests, we use the FFT and apply the Fourier transform shift theorem to translate the image without introducing phase error [65,71].…”

“…In 2D DIC, C 4 biquintic spline interpolation has also been used [71]. Interpolation methods with higher continuity often result in more accurate DVC results, though for some patterns such as with a bimodal gray level distribution, the opposite is true [71].…”

“…2D DIC has typically used C 2 bicubic spline interpolation [8] or C 4 biquintic spline interpolation [71], which has been shown to often give more accurate results than C 0 bilinear and C 1 bicubic interpolation [71]. We therefore enhance DVC by using C 2 tricubic spline interpolation, and discuss how to implement it efficiently for DVC in Chapter 4.…”

“…For translation tests, we use the FFT and apply the Fourier transform shift theorem to translate the image without introducing phase error [65,71]. Fourier series interpolation can also be used for arbitrary deformations, but the FFT algorithm no longer applies.…”