Improving 3D surface measurement accuracy on metallic surfaces

3D surface measurement of machine parts is challenging with the increasing demands for micron level measurement accuracy and speed. Optical Metrology based techniques using stereovision face unique challenges in feature extraction due to the complexity of the machine parts and surface finish. For complicated parts, structured laser light is projected on the surface to generate unique or reference features for stereo reconstruction. The induced laser light on the surface is scattered due varies surface phenomena (light scattering, multiple reflections). These scattered and diffused laser lines induce new features on surface, which misguides the surface reconstruction. While targeting micron level accuracy, sub-pixel feature extraction is also effected by the speckle noise, biasing due to sampling, shape etc. In this paper, we propose new method of improving the accuracy of 3D surface reconstruction on metallic shining surfaces. The proposed template based guidance approach with tangent based feature extraction improves the accuracy of detection in the effected regions by 30%.