Optical quality assurance in the textile industry: determination of the pilling grade of textile samples

One relevant quality parameter of textile material is the propensity of the material to form pills after some time of usage. This propensity is summarized in a standardized pilling grade which needs to be determined within the incoming goods inspection. To do so, small samples are pre-treated and visually inspected. This procedure is done by humans without digital assistance or documentation. We will show, how a desktop-setup with angle selective illumination included can be used to visualize and capture and analyze all the pills on a sample. The methodology is based on the computation of a locally correlative height map which is not influenced by the structure and color of the textile material.