On Error Assessment in Stereo-based Deformation Measurements

Abstract

Using the basic equations for stereo-vision with established procedures for camera calibration, the error propagation equations for determining both bias and variability in a general 3D position are provided. The results use recent theoretical developments that quantified the bias and variance in image plane positions introduced during image plane correspondence identification for a common 3D point (e.g., pattern matching during measurement process) as a basis for preliminary application of the developments for estimation of 3D position bias and variability. Extensive numerical simulations and theoretical analyses have been performed for selected stereo system configurations amenable to closedform solution. Results clearly demonstrate that the general formulae provide a robust framework for quantifying the effect of various stereo-vision parameters and image-plane matching procedures on both the bias and variance in an estimated 3D object position.

Uncertainty assessment of coupled Digital Image Correlation and Particle Image Velocimetry for fluid-structure interaction wind tunnel experiments

“…0.1-0.25 mm) presents large errors due to the chosen stereo angle. The stereo angle provides a tradeoff in accuracy for in-plane and out-of-plane translations (Reu, 2012;Wang et al, 2011). In order to decrease error in relatively small out-of-plane rigid body motions, the stereo angle should be increased.…”

“…The stereo angle between the two cameras controls the measurement accuracy of the out of plane deformation (Tang et al, 2012;Schreier et al, 2009). This was very important in the present research as the major mode of deformation was out-of-plane and the stereo angle was carefully considered with respect to the dimensional constraints of the wind tunnel (Reu, 2012;Wang et al, 2011). As demonstrated by Crammond et al (2013), the variations in speckle pattern density and sizes influence the measurement accuracy.…”

Single‐camera special stereo‐digital image correlation applied for accurate virtual fields method identification

“…The disturbances may be caused by the systematic error of the measuring system, since the errors of strain (Figure ) cannot be ignored compared with the amplitude of measured strain (Figure ). An improved SS‐DIC measuring system with optimised system configuration and higher magnification lens would reduce the systematic error and improve the accuracy of measured strain fields …”

Biomechanical assessment in models of glaucomatous optic neuropathy

“…DIC has been applied to characterize a wide range of soft biological tissues (Boyce et al, 2008; Cheng and Gan, 2008; Sutton et al, 2007; Tonge et al, 2013b; Wang et al, 2003; Zhang et al, 2002), in part because it requires minimal specimen preparation. The primary disadvantage of DIC is that the accuracy and uncertainty is strongly dependent on the quality and noise of the speckle pattern, lighting, and imaging system (Ke et al, 2011; Ning et al, 2011; Wang et al, 2011). The displacement error and uncertainty of DIC methods are higher than for interferometric methods, and are not well characterized for non-homogenous deformations (Cirello and Pasta, 2010; Soons et al, 2012; Zhang et al, 2002).…”