Abstract: Precision measurement of blade wall thickness along the common normal of inner and exterior surfaces is required to guarantee the reliability of air engine. A blade wall thickness precision measurement method based on ICT image with sub-pixel accuracy is researched to satisfy this requirement. This method adopts edge extraction technology to find the common normal of inner and exterior surfaces and edge location technology to get the start and end points of wall thickness along the normal. Then the wall thickness with unit pixel is available by calculating the distance between the start point and the end point. Finally the wall thickness with unit millimeter is created by unifying pixel size. The experiment result demonstrates that the practical accuracy of this method reaches 0.2 pixel and 0.042mm.

Key words: image processing, wall thickness measurement method, moment match, turbine blade, ICT image