Template matching method for SMD inspection using discrete wavelet transform

We propose a template matching method for component inspection of SMD assembly system. To discriminate wrong assembled components, input image of component is matched with its standard image by template matching algorithm. For a rapid inspection system, the calculation time of matching algorithm should be minimized. Since standard images of all components located in a PCB are stored in computer, it is desirable to minimize the memory size of standard image. We apply the discrete wavelet transformation to minimize the image size as well as the calculation time, Only 7% information of original image is used to discriminate goodness or badness of component assembly. Comparative results are presented to verify the usefulness of the proposed method.