On the use of Bayer Sensor Color Cameras in Digital Image Correlation

Abstract

The digital image correlation (DIC) technique uses monochrome images, which are usually captured using monochrome cameras. Color cameras with Bayer filter patterns are available with higher specs and lower prices than monochrome cameras, and their images can be used in DIC after they are converted to monochrome. In this paper, in-plane rigid-body-translation experiments are used to compare the DIC strain measurement error for monochrome and color cameras under similar conditions. Furthermore, different algorithms for converting color images to monochrome are compared with the aim of reducing the DIC measurement error. The results show that monochrome images captured by color cameras cannot give the same level of accuracy as the images of monochrome cameras; however, DIC accuracy is dependent on the algorithm used for converting color-to-monochrome images. The results show that the interpolation methods used for demosaicing the color channels affect the DIC accuracy. For high contrast images, higher accuracy is achieved using low-order interpolation; while for low contrast images, higher-order interpolation gives better results. Interestingly, it is found that, for high contrast images, using the green channel image alone can give better DIC accuracy than the monochrome image that is obtained by combining the three channels.