Region segmentation by multispectral imaging
This paper describes a method for region segmentation of a circuit board based on surface-spectral reflectance measurements by using a multispectral imaging system. The elements on a board are composed of different materials such as metal, paint, and inhomogeneous dielectric. First, we introduce the camera system for machine inspection of circuit boards. Second, an algorithm is proposed for obtaining reliable estimates of the spectral reflectances for a raw circuit board. Third, a reflectance analysis method, is presented for segmenting the reflectance image into five element regions of: (1) a substrate, (2) footprints, (3) resist-coated metals, (4) non-resist metals, and (5) silk-screen prints. The reflectance images observed at two illumination directions are used for identifying rough metallic surfaces. Finally, the feasibility of the method is shown in an experiment.