A New Method of Inspection Based on Shape from Shading

In computer vision, shape recovery is a classic problem. The shape from shading problem aims to reconstruct a 3D shape from one or more intensity images. Inspection of solder joint is a critical step in the assembly of PCB (Printed Circuit Board). So, non-destructive inspection technology has been widely used in a production of PCB. In automated optical inspection (AOI) field 2D inspection appears to be more prevalent industry-wide than 3D inspection, but the limit of 2D inspection in some defects is apparent. This paper deals with the reconstruction of the solder joint’s surface in PCB based on shape form shading technology. The advantages of SFS method are analyzed firstly. Then, theory and survey of SFS method is introduced. To overcome the disadvantages existing in conventional SFS methods, some improved algorithms are provided and proved by experiments. Experimental results reveal that the proposed method shows practical value in solder joint inspection.