Research Of The Improvement In Digital Resolution And The Method Of The Digital Correlation

Digital image correlation method is a new optical measurement method based on numerical analysis and digital image processing.Since its introduction in the 1980 s,it has gained wide attention in many fields because of its excellent environmental adaptability and convenient measurement range and resolution adjustment.However,due to the limitations of the algorithm itself and the noise interference,the digital image correlation method has some shortcomings in the calculation speed and measurement accuracy in the practical application.In this paper,a interpolation method based on cubic spline interpolation after upsampling process is proposed.In this method,upsampling process is applied on one-dimensional/two-dimensional signal to improve the resolution,and cubic spline interpolation is used on the basis of it.The interpolation method based on cubic spline interpolation after upsampling process can be described as follows: the speckle images both before and after deformation are analyzed to obtain the characteristics of the digital image spectrum;based on the characteristics of the digital image spectrum and the given image resolution requirements,the two-dimensional digital sequence high multiples interpolation anti-imaging digital filter is designed;the image is filtered and subpixel resolution image is obtained;the cubic spline interpolation is performed on the sub-pixel resolution image to realize interpolation at any point.Through experimental results,it can be concluded that method based on cubic spline after upsampling can effectively improve the resolution of digital images,and have an advantage over only using cubic spline interpolation.In this paper,interpolation method based on cubic spline interpolation after upsampling process is applied to digital image correlation method.Firstly,digital image correlation is used on the images of the object surface both before and after deformation to obtain a preliminary correlation area.Then,on the basis of obtaining the more accurate correlation area,the upsampling processing is further performed on the deformed image to improve the sub-pixel resolution of the digital image.And the cubic spline interpolation is performed on the sub-pixel resolution image to constantly approach the maximum correlation coefficient,and finally obtain the displacement and achieve higher accuracy.It can realize the requirements of the high accuracy required in digital image analysis in existing digital image correlation.The method described in this paper can effectively improve the sub-pixel resolution of digital image analysis and it can solve the contradiction between the limited resolution of the existing digital image acquisition technology and the high-precision and high-stability requirements of the digital speckle field analysis.