Optimization of speckle pattern for digital image correlation

Abstract

Since artificial speckle patterns may lead to different computation results, digital speckle pattern generated by computer is adopted for digital image correlation (DIC) to keep the results consistent. A procedure to fabricate controllable and repeatable speckle patterns is proposed, including optimization and transfer of the digital speckle patterns to specimen surfaces. Firstly, through Fast Fourier Transform (FFT) shift experiment, digital speckle pattern in multiple-radius type and single-radius type are discussed considering computation speed, systematic error, standard deviation error and root mean square error. So a speckle pattern with the optimized speckle size is obtained. Then, several indirect transfer methods are compared and utilized to fabricate the optimized digital speckle patterns on specimen surfaces. Hence, speckle pattern for DIC can be controllable and repeatable and this procedure will contribute to DIC standardization.