Study On Quality Inspection Technique For Gravure Printing Based On The Statistical Threshold Method

High speed and automation are the developmental trend of gravure technology, but the inspection technology of printing quality can't satisfy the demand at present. Although many experts in interior and exterior have done plentiful researches, there are still lots of defects which couldn't be checked. This paper put forward a new method inspecting gravure printing quality for improving the inspection efficiency, reducing the wastage, saving the cost and achieving the progress control.The model of gravure quality inspection system based on statistical threshold method was established with the technology of digital image processing, and defects of gravure image could be detected. The peak out signal-to-noise was used to evaluate the effect of the noise process algorithms. According to the match right probability and time, the image registration algorithm is selected. The workflow of defect inspection was designed on the base of inspection demand. The variance analysis and histogram analysis were used to process experimental data.Comparing with the five algorithms, the Gauss Filter was chosen to wipe off noise. The match right probability and time of the three kinds of image registration algorithm were calculated, and the algorithm of twice integrate match with high match right probability and short time was selected. By analyzing image gray value fluctuation, the standard model image was built and the gray threshold of each pixel was gained. According to the workflow of defect inspection, the gravure quality inspection software was compiled to test and verify the statistical threshold method.It has indicated: the peak out signal-to-noise of Gauss Filter was 28.89 dB, and the image information loss would be reduced by using Gauss Filter to wipe off noise in gravure image. The algorithm of twice integrate match having the virtue of correlation coefficient method and the error method was suit for the gravure image registration, and the match time was one fifth of error method under the condition of insuring the match right probability. The algorithm of printing defect inspection based on the statistical threshold method could resolve the problem of outline false inspection, and the work time was the half of the conventional algorithm with the same precision.