Analysis And Study On Screening Errors Based On Concept Of Printing Simulation

Screening is an important working procedure in prepress processing, and it had great effect on the fidelity duplication of the original manuscript. The digitized method provides a new technical way for us to carrying on precise screening calculation and reducing the error brought by prepress processing, therefore, the research on the digitized screening is one of the hot spots in recent years. Through research and exploration on the stimulant printing system, this paper attempted to seek a sort of solution to control and reduce the color duplication error in prepress processing. Based on the stimulant printing system, this paper used the theoretical analysis combined with digitized simulation method, carried on systemic theoretical research and technical analysis of amplitude modulated screening,frequency modulated screening and hybrid screening.The main work of this paper and results obtained are as follows:(1)Based on the thought and method of neugebauer equations, a prototype of stimulant printing system was issued and completed. The module of screening was designed and developed, and it had realized the digitized simulation function on different screening.(2)Analyzed the theory on screening errors. The research indicated, that the different screening methods produced different color effects based on the same color-separate method; The major effect factors included:the quantization error, screening algorithm, dot shape and screening angle.(3)Based on the stimulant printing system, color-difference calculation and subjective evaluation, amplitude modulated screening was analyzed and researched. The research indicated:the image screened by super cell structure screening, had moire pattern in the bright region. The middle region had smooth pattern, and the dark region had unsatisfactory reproduction in red and black.(4)Based on the stimulant printing system, color difference calculation and subjective evaluation, frequency modulated screening is analyzed and researched. The research indicated:the image screened by Bayer dithering algorithm of FM screening, had obvious artificial trace and lose the detail information; The image screened by F-S diffusion algorithm of FM screening, had the smallest color-difference and smooth pattern, but it appeared granularity and distorted contour; the image screened by dot error diffusion algorithm of FM screening, had not artificial trace and granularity, but color-difference had large error; The image screened by ELA error diffusion algorithm of FM screening, had good reproduction on detail information, and reduced the contour distortion. Compared with amplitude modulated screening and frequency modulated screening, the latter has small color-difference.(5)Based on research of advantage and disadvantage between amplitude modulated screening and frequency modulated screening, hybrid screening was proposed with different color-separation films using different screening. The stimulant experiments indicated, that this screening method can reduce screening errors.