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Detecting method for color printing quality

A color printing and quality inspection technology, applied in color measurement devices, optical testing flaws/defects, etc., can solve the problems of very sensitive environment, small amount of data, unable to truly reflect the quality of color printing, etc., to achieve simple inspection equipment and data. The effect of reduced volume and fast inspection speed

Inactive Publication Date: 2009-02-04
CHINA BANKNOTE PRINTING & MINTING
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] The present invention solves the defect that the above-mentioned color printing quality inspection is very sensitive to the environment and cannot truly reflect the color printing quality by converting to a "black and white model" and indirectly inspecting the chromaticity error of color printing, and provides a color printing inspection method. Chromaticity error, small amount of data, insensitive to the environment, a simple system required, and a color printing quality inspection method with fast inspection speed

Method used

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  • Detecting method for color printing quality
  • Detecting method for color printing quality
  • Detecting method for color printing quality

Examples

Experimental program
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Embodiment 1

[0025] Embodiment 1: As shown in FIG. 1 , a color CCD camera captures a color image of a color printing document to be inspected, and outputs image signals of tristimulus colors R, G, and B respectively. Due to the uneven illumination of the light source and the uneven response of the color CCD camera, the image brightness is uneven, so it is necessary to compensate for the image non-uniformity; in addition, due to the change of the light source and the difference in the response of the color CCD camera to RGB colors, it is necessary Perform white balance correction on color CCD cameras, but this correction does not need to be performed three times a day, as long as it is performed once a day, or even less.

[0026] After white balance correction, the color image signal of the color printing document is divided into two paths: one path is transmitted to the color image sampling link, and the other path is transmitted to the color image to grayscale image conversion link.

[00...

Embodiment 2

[0036] Embodiment 2: The sampling density is selected as 1% of the original image, and the others are the same as in Embodiment 1.

Embodiment 3

[0037] Embodiment 3: The sampling density is 10% of the original image, and the others are the same as Embodiment 1.

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Abstract

The color printing quality detecting method features that the color printing image is separated based on color before sampling and chroma error of the sampled image is detected directly with the sampling density being 1-10 % of original image. The method of detecting the chroma error of the sampled image directly is superior to available method, which converts the color image into 'black-and-white' model before detecting the chroma error indirectly and is environment sensitive. The present invention also provides one bank note quality detecting method, which can detect all the errors of bank note quality in less detection times and fast speed with relatively simple apparatus without needing daily thrice white balance corrections.

Description

technical field [0001] The invention relates to a method for checking the quality of color printing, in particular to a method suitable for checking the quality of color printing of large banknotes. Background technique [0002] The inspection method of color printing documents, especially the color printing quality of large banknotes, determines the inspection accuracy, inspection speed and complexity of inspection equipment, and is one of the key technologies in inspection equipment. At present, only a Swiss company has produced the Nota SaveCheck II color printing quality inspection machine for large banknotes in the world. However, the inspection method used for this machine inspection is to convert the tristimulus values ​​R (red value) G (green value) and B (blue value) of the image color into black and white grayscale J values ​​by the following formula, namely [0003] J=Kr R+Kg G+Kb B (1) [0004] In the formula, Kr, Kg and Kb are conversion coefficients, ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N21/89G01J3/46G01N21/88
Inventor 顾克俭王川屈明生周仁忠王岩松杨艺
Owner CHINA BANKNOTE PRINTING & MINTING