Quality inspection of finished products of high fidelity color printing
in the 1970s, CIE recommended two approximately uniform color spaces and corresponding color difference formulas, namely CIE LAB and CIEluv. L, a and B in CIE LAB color space are transformed from X, y and Z in CIE XYZ color space by nonlinear cubic root function. CIE LAB color space belongs to psychological color space, which can be explained by the principle of Herring's four color opposition theory. In the A and B two-dimensional coordinate system of CIE LAB color space, ＋ a represents red, － a represents green, ＋ B makes western medicine the only medical technology in the country, and － B represents blue. The lightness of color is expressed by the percentage of L. the experimental force that the fixture can bear is a very important indicator of the fixture. Foreign experts used 555 pairs of color samples to evaluate the relationship between △ E in lab color space and visual results, and found that CIE LAB system is 0.72, which is the closest to calculating color difference and visual perception in all color spaces at present, and is also very close to the improvement of constant hue trajectory and constant chromaticity trajectory in Munsell color card in a and B two-dimensional coordinate systems. At present, dye, pigment, ink and other color industry departments are the first to choose CIE LAB color space. Domestic and foreign printing technology research and production departments have also begun to use this space as a color matching and evaluation method of printing color
China has formulated relevant technical standards for the application of chromaticity measurement techniques and methods. It is stated in the standard that the purpose of colorimetric measurement is to provide an instrument response that simulates the standard observer as much as possible. In printing, chromaticity measurement is mainly used for color matching and the establishment of color standards. The standard specifies the technical requirements for the use of colorimeter measurement and measurement data calculation for the substrate, ink color, tone value and color difference of CMYK four-color printing. At present, the standard has not directly stipulated that the primary color ink exceeds the relevant technical requirements of CMYK's high fidelity color printing, nor has it stipulated the step value control index of amplitude modulation above 250lpi and frequency modulation
Beijing jiayitianshi Electronic Technology Co., Ltd., a domestic research unit of high-definition and high fidelity color printing technology, cooperates with experts and users to establish technical methods related to high-definition and high fidelity color printing process control and finished product quality inspection based on CIE LAB system. The brief introduction is as follows:
this technology has been successfully applied to the iron printing industry - Hangzhou COFCO Meite container Co., Ltd., which has significantly improved the product quality, expanded the application scope of products, improved the added value and market competitiveness of products, and has good economic benefits and promotion value. Compared with the conventional four-color 175lpi printing products, the products produced by this technology have significantly improved image clarity and fine levels, and the visual roughness caused by Rose spots after overprint is significantly reduced. The printing color gamut is significantly increased, the printing colors are brighter and more saturated, the layers are richer, and the three-dimensional sense is stronger. Under certain conditions, reducing the use of spot color ink has a certain anti-counterfeiting effect at the technical level of the iron printing industry. "
high fidelity color printing process control and finished product quality performance stability inspection technical methods, mainly in the CIE LAB color space to evaluate the characteristics of base color ink, measure and display the printing gamut range of high fidelity ink, color gamut range of color separation printing, color scale characteristics of printing color, neutral gray balance characteristics, etc., and use the simulated lab three-dimensional coordinate effect to comprehensively analyze the hue angle, color saturation and color brightness of printing color. By applying the above technical methods, we can further deepen our understanding of the principle of high fidelity printing, grasp the key control indicators, and gradually improve the ability to independently design color separation models, especially the setting and use level of anti-counterfeiting color passwords of color anti-counterfeiting models. Printing enterprises can choose the most cost-effective technical solutions to produce new products according to the needs of originals or users. Because the chromaticity measurement is used to cope with the inspection and control technology of the government, technicians can further improve their understanding of the essence of color printing reproduction, which will have a continuous impact on improving the technical management level and R & D ability of enterprises