Experimental Mechanics

, Volume 56, Issue 6, pp 969–985 | Cite as

Cross Polarization for Improved Digital Image Correlation

  • William Scott LePage
  • Samantha Hayes Daly
  • John Andrew Shaw


Digital image correlation (DIC) is a surface deformation measurement technique for which accuracy and precision are sensitive to image quality. This work presents cross polarization, the use of orthogonal linear polarizers on light source(s) and camera(s), as an effective method for improving optical DIC measurements. The benefits of cross polarization are characterized through quantitative and statistical comparisons from two experiments: rigid body translation of a flat sample and uniaxial tension of a superelastic shape-memory alloy (SMA). In both experiments, cross polarization eliminated saturated pixels that degrade DIC measurements, and increased image contrast, which enabled higher spatial precision by using smaller subsets. Subset sizes are usually optimized for correlation confidence interval (typically with subsets of 21×21 px or larger), but can be decreased to achieve the highest possible spatial precision at the expense of increased correlation confidence intervals. Smaller subset sizes (such as 9×9 px) require better images to maintain correlation within error thresholds. By comparing DIC results from a uniaxial SMA tension test with unpolarized and cross-polarized images, we show that for 9×9 px subsets, the loss of valid DIC data points was reduced almost ten-fold with cross polarization. The only disadvantage we see to cross polarization is the decrease in specimen illumination due to transmission losses through the polarizers, which can easily be accommodated with sufficiently intense light sources. With the installation of relatively inexpensive linear polarizing filters, an optimum optical DIC setup can provide even better DIC measurements by delivering images without saturated pixels and with higher contrast for increased DIC spatial precision.


Digital image correlation DIC Cross polarization Optical imaging 



We gratefully acknowledge financial support from the National Science Foundation (CAREER Award, CMMI-1251891) and the Department of Defense (NDSEG Fellowship).


  1. 1.
    Peters W, Ranson W, Sutton M, Chu T, Anderson J (1983) Application of digital correlation methods to rigid body mechanics, Vol 22Google Scholar
  2. 2.
    Sutton M, Mingqi C, Peters W, Chao Y, McNeill S (1986) Application of an optimized digital correlation method to planar deformation analysis. Image Vis Comput 4 (3):143–150CrossRefGoogle Scholar
  3. 3.
    Bay B, Smith T, Fyhrie D, Saad M (1999) Digital volume correlation: Three-dimensional strain mapping using X-ray tomography. Exp Mech 39(3):217–226CrossRefGoogle Scholar
  4. 4.
    Franck C, Hong S, Maskarinec S, Tirrell D, Ravichandran G (2007) Three-dimensional full-field measurements of large deformations in soft materials using confocal microscopy and digital volume correlation. Exp Mech 47(3):427–438CrossRefGoogle Scholar
  5. 5.
    Reu P (2014) All about Speckles: Aliasing. Exp Tech 38:1–3Google Scholar
  6. 6.
    Sutton M, Orteu J, Schreier H (2009) Image correlation for shape, motion, and deformation measurements. Springer , New YorkGoogle Scholar
  7. 7.
    Reu P (2014) All about speckles : Speckle Size Measurement. Exp Tech 44(11):4–5Google Scholar
  8. 8.
    Kammers A, Daly S (2013) Self-assembled nanoparticle surface patterning for improved digital image correlation in a scanning electron microscope. Exp Mech 53(8):1333–1341CrossRefGoogle Scholar
  9. 9.
    Reedlunn B, Daly S, Hector Jr L, Zavattieri P, Shaw J (2013) Tips and tricks for characterizing shape memory alloy wire: part 5 – full-field strain measurement by digital image correlation. Exp Tech 37(3):62–78CrossRefGoogle Scholar
  10. 10.
    Reu P (2014) Speckles and their relationship to the digital camera. Exp Tech 38(4):1–2CrossRefGoogle Scholar
  11. 11.
    Hild F, Roux S (2012) Comparison of local and global approaches to digital image correlation. Exp Mech 52(9):1503–1519CrossRefGoogle Scholar
  12. 12.
    Reu P (2015) All about Speckles: Contrast. Exp Tech 51(4):1–2Google Scholar
  13. 13.
    Kwak J (2008) Digital image correlation (DIC) methods for small scale measurement. Master’s thesis, Mechanical Engineering, State University of New York at BinghamtonGoogle Scholar
  14. 14.
    Adams A (1948) Basic photo one: camera and lensGoogle Scholar
  15. 15.
    Allphin W (1959) Primer of lamps and lightingGoogle Scholar
  16. 16.
    Apolinar E, Rowe W (1980) Examination of human fingernail ridges by means of polarized light. J Forensic Sci 25 (1):154–161CrossRefGoogle Scholar
  17. 17.
    Robertson A, Toumba K (1999) Cross-polarized photography in the study of enamel defects in dental paediatrics. J Audiov Media Med 22(2):63–70CrossRefGoogle Scholar
  18. 18.
    Kawara T, Obazawa H, 1980 A new method for retroillumination photography of cataractous lens opacities. Am J Ophthalmol 90(2):186–189Google Scholar
  19. 19.
    Anderson R (1991) Polarized light examination and photography of the skin. Arch Dermatol 127(7):1000–1005CrossRefGoogle Scholar
  20. 20.
    Cooper M, Skaggs M, Reu P (2015) High-speed stereomicroscope digital image correlation of rupture disc behavior. Society of Experimental Mechanics 2015 annual conferenceGoogle Scholar
  21. 21.
    LePage W, Shaw J, Daly S (2015) Thermomechanical characterization of shape memory alloy mode I fracture behavior. Society of Experimental Mechanics 2015 annual conferenceGoogle Scholar
  22. 22.
    Hanrahan P, Krueger W (1993) Reflection from layered surfaces due to subsurface scattering. In: Proceedings of the 20th annual conference on Computer graphics and interactive techniques, 165–174, ACMGoogle Scholar
  23. 23.
    Reu P (2015) Points on paint. Exp Tech 39:1–2Google Scholar
  24. 24.
    Pan B, Lu Z, Xie H (2010) Mean intensity gradient: An effective global parameter for quality assessment of the speckle patterns used in digital image correlation. Opt Lasers Eng 48 (4):469–477CrossRefGoogle Scholar
  25. 25.
    Prewitt J (1970) Object enhancement and extraction. Picture processing and Psychopictorics 10(1):15–19Google Scholar
  26. 26.
    Kim K, Daly S (2010) Martensite strain memory in the shape memory alloy nickel-titanium under mechanical cycling. Exp Mech 51(4):641–652CrossRefGoogle Scholar
  27. 27.
    Kim K, Daly S (2013) The effect of texture on stress-induced martensite formation in nickel–titanium. Smart Mater Struct 22(7):075012CrossRefGoogle Scholar
  28. 28.
    Woodward C (1851) A familiar introduction to the study of polarized lightGoogle Scholar

Copyright information

© Society for Experimental Mechanics 2016

Authors and Affiliations

  • William Scott LePage
    • 1
  • Samantha Hayes Daly
    • 2
  • John Andrew Shaw
    • 3
  1. 1.Department of Mechanical EngineeringUniversity of MichiganAnn ArborUSA
  2. 2.Departments of Mechanical Engineering/Materials Science, EngineeringUniversity of MichiganAnn ArborUSA
  3. 3.Department of Aerospace EngineeringUniversity of MichiganAnn ArborUSA

Personalised recommendations