Method for measuring yarn evenness based on cross section perimeters of yarns

The invention relates to a method for measuring yarn evenness based on cross section perimeters of yarns. Unevenness of yarn appearance can be understood and represented from the point of view of the relation between yarns and fabrics, an elliptic yarn cross section model is used as a base, a biaxial CCD camera is used for obtaining images of yarns in two directions which are mutually perpendicular, and further cross section perimeters of yarns and the concrete measurement and calculation method for yarn evenness based on cross section perimeters of yarns are provided. The method can be used for effectively reducing influences of irregular cross sections, hairiness and the like of yarns on evenness measurement of yarn appearance, and is not influenced by temperature and humidity, atmospheric conditions and other extraneous conditions, as well as yarn blending state of optical property differences and the like. Influence of yarn cross section on yarn evenness and a deformation relation in a process from yarn t