Objective evaluation of fabric pilling using stereovision

A noncontact three-dimensional measurement method for the objective evaluation of fabric pilling is developed. Three parameters, including the number, area, and density of pills, are defined by analyzing the five conventional standard pilling photographs that characterize pilling. The relationship between pilling grades and those three parameters can be obtained through a multivariable linear regression method. A CCD camera is used to capture the image of a laser line projected on the surface of the fabric specimen, and a simple trigonometric calculation is performed to reconstruct the three-dimensional shape of the fabric. Also, two CCD cameras are used to reconstruct the fabric surface with pills with a stereovision technique. The three-dimensional surface model is transformed into a binary image using a height-threshold algorithm, and the parameters extracted from that image are used to calculate the pilling grade of the specimen.