Abstract: Abstract: Effect of imaging mode of scanning electron microscope (SEM) is investigated on the computation results of digital speckle correlation (DSC) method. The strain distribution on plasma sprayed copper coatings is analyzed based on the results. It shows that the imaging mechanisms are different for the secondary electron imaging mode and backscattered electron imaging mode. Correspondingly, the data of correlation coefficient and its standard deviation, obtained from the computation using DSC method, should be used as the criterion for selecting the proper imaging mode of SEM. The strain distribution of plasma sprayed coatings is characterized using the DSC method. The shape of the strain concentration zone at the cracking tip changes from butterfly like to circle like.