Evaluation Method Of The Perceived Quality Of Digital Print Text Clarity

With the growing popularity of digital printing technology and the increasing attention on digital prints quality, how to evaluate the text sharpness of digital prints with common digital printing equipments and paper has become a focus issue to improve the digital prints quality.This research primarily focuses on the evaluation model establishment of perceptual quality of digital prints sharpness so that the text sharpness can be predicted through this model.Theoretical analysis:first of all, this research briefly introduces the current digital prints quality requirements, the quality defects of digital prints and evaluation methods of digital prints quality; secondly, it discusses the objective quality indexes of text and line sharpness in ISO13660. The theoretical analysis lays a foundation of text sharpness comprehensive evaluation and carries out fundamental research on digital prints quality control and examination.Experimental research:firstly, designed evaluation text chart containing uniformly-spaced stripes with different orientations and widths and characters with different sizes and fonts, and output the text chart through printers with different imaging methods and digital printing paper with different types; secondly, based on eight line or text sharpness objective indexes of ISO13660, extracted four most typical indexes of contrast, raggedness, blurriness and line width and selected 16 samples with different quality levels based on the four indexes;lastly, correlated the subjective evaluation results with objective measurement values, established the mathematical relations between subjective evaluation and objective measurement and realized the evaluation model of perceptual quality of digital prints sharpness.Main conclusions of this research:(1) Mathematical evaluation model of perceptual quality is designed for black and magenta digital prints. (2) Perceptual quality of digital prints line and text sharpness is correlated with its contrast, raggedness and width, positively related with contrast and width and negatively related with raggedness. Based on this correlation, perceptual quality of text sharpness can be well predicted through the linear model established.The evaluation model of perceptual quality of digital prints text sharpness established in this research is the first attempt in China to correlate the perception of human eye on text sharpness with the objective index of physical measurement, thus providing positive support to the development of digital printing technology. Meanwhile, this research proposes new methodologies to the research on digital prints quality evaluation and provides basis for the quality improvement of digital printing devices, printing substrates and ink.