Study On Automatic Registration Of Sheet-Fed Offset Press

The register precision is an important target to test printing machines and printing products. It is difficult problems in high-speed measurement and exact calculation. Though some experts in print machine manufacture and print quality control have made plentiful research and obtained many fruits, but the above problems are not solved until now. The thesis's purpose was to raise a kind of new algorithm, which could automatically test register error. It satisfied demands that are the automatic test of offset print quality, and provided theory basis to the automatic register system's exploitation. The results in practice (?)re not only benefit to research on the sheet-fed offset automatic register system, but also improve printing quality, decrease cost of production, satisfy people's demands of high-quality printing production and bring economy benefits for enterprises, make the progress of homemade offset automatization and the advance of nation industry.The main methods: (1) According to the image processing principle and the image characteristic of register "+" line, the right smooth algorithm was chose by applying the image smooth theory. (2) The model of testing system was set up through the method that the digital image processing technology was used in the automatically testing register system. It realized the error calculate in real time, and modified the basic parameters of model. (3) A New Template Matching algorithm was proposed with statistical theory. The experimental projects were designed by the black box theory. Automatically testing register error software was programmed with VC7.0. (4) The coefficient analytical method, the average contrast and the minimum average square variance theory were used to process experimental data.The main works: (1) The five common algorithms of image smoothing were evaluated by image pre-processing theory. A new smooth algorithm suited for register "+" line image was designed. It is all-in the system from image input to register error output. (2) The traditional image register method was modified through experimental results, and the automatically algorithm model of testing register error was designed. (3) The automatically testing register error software was programmed that is based on the New Template Matching algorithm.Conclusions: (1) The image blur and image information loss would be avoid. By the smooth algorithm combined 3×1 with 1×3 median filter, that would be used in the register "+" line preprocess. (2) The New Template Matching algorithm was effective and feasible, and it can automatically test register error in the prescriptive range. Its exactness was 0.01mm and met register demands of sheet-fed offset.