Analysis of reliability of subpixel displacement estimations used in digital speckle correlation method (DSCM)

This paper discusses the precise estimation of interpolation and gradient algorithm which search subpixel displacement by digital speckle correlation method. We obtain these results which the displacement estimations of subpixel are affected by speckle design, interpolation formula, estimated function etc. The theory precision of the quadratic interpolation and the gradient method are analysed by mathematics theory and numerical computation. We ameliorate all formula on discrete integral aspect for computing subpixel displacement. The experiments show that the computational results of the new formula are more stable than the general method.