Precision Improvement of Overprinting System Based on Improved Laplace Edge Detection Algorithm

This paper proposes a solution to locate the crossline center in overprinting system. Crosslines of 4 different colors are printed at the same coordinate. Because of mechanical error, they do not coincide. The system uses the measured deviation to calibrate. This paper obtains accurate deviation value through three steps. First, the picture collected by a CCD camera will be processed by color segregation algorithm. In this process, RGB data turn into CMYK data, and each color will be on a single picture. After that, a Laplace edge detection algorithm is improved by combining it with 2D Gauss filter. This improved Laplace edge detection algorithm has a better noise suppression effect, which means it is even less likely to judge noise as the edge of a graph. Finally, target searching algorithm based on rhombus matching is used to figure out the center of crossline. The average absolute error from 2,000 simulations is 3.192 pixel, which shows that the algorithm in this paper has a high accuracy.