Thus, a faster noncontact Digital Image Correlation (DIC) mechanism is utilized along with the traditional techniques to measure the strain. 
Digital Image Correlation (DIC)
The Newton-Raphson (NR) technique is considered to be an accepted mechanism for accurate tracking of different intensity relocation. 
Newton-Raphson (NR) technique
The number of iterations can be reduced using the Sum of Square of Subset Intensity Gradients (SSSIG) method. 
Sum of Square of Subset Intensity Gradients (SSSIG) method