Edge measurement using stereovision and phase-shifting methods

Abstract

Three-dimensional edge measurement is critical in many applications such as blade manufacturing due to the stringent requirements on aerodynamic performance of blades. Optical metrology techniques provide very good tools in terms of speed and accuracy, but face some challenges as well, such as discontinuity, irregularity, and size variation in the edge shape. This paper presents several methods that include stereovision techniques to capture a sharp edge and phase-shifting to capture an edge profile of a blunt edge. For sharp edge measurement with stereovision, multiple cameras are used to view the edge from different directions. Then the captured images are processed to obtain the point cloud of the edge. For blunt edge measurement, a phase-shifting method is applied. After the edge profile is obtained, all edge information can be extracted. In this paper, different illumination methods are discussed and different edges are measured. Experimental data shows that these methods are practical in obtaining accurate edge or edge profile.