An Efficient Method of PCB Images Stitching

In solder paste inspection, since the camera' field of view is small relative to the size of PCB, it is necessary to stitch the partial PCB images taken in different parts. Stitching PCB images requires real-time processing, while common existing methods are not satisfactory, so this paper proposes a novel method to further speed up image stitching. This study contributes in three ways: First, a 4-step improved method used for corner detection is introduced, which builds on the well-known FAST corner detection method. Second, the nearest and next nearest neighbor ratio method, bidirectional matching method and RANSAC are adopted to reduce the possibility of mismatching and optimize the performance of the corner matching. Third, several corner detection methods are compared. Performances in terms of quantitative and qualitative results are discussed so as to move towards the selection of the most appropriate method. The experiments demonstrate that the improved image stitching method outperforms other methods both in efficiency and accuracy.