Color restoration control method and system of offset press

Abstract

The invention belongs to the technical field of printing color management, and provides a color restoration control method and system for an offset printer, and the method comprises the steps: firstly, detecting easy-control parameters and real-time change parameters of the printer, and transversely dividing a printed electronic file into a plurality of areas with the same number as ink areas of the printer; a printed matter scanning device is used for scanning a printing sample page, the chromatic aberration variable of each ink area between the printing sample page and a customer confirmation sample manuscript is calculated, an AI large model is used for learning to obtain the relation between the ink fountain opening degree variable quantity of each ink area and the corresponding chromatic aberration variable, and subsequent printed matter is scanned and detected in real time. And the AI large model generates ink key adjustment data of each ink area according to the detection result, and transmits the adjustment data to the printing machine for corresponding adjustment. The printing machine can be intelligently controlled according to the detected real-time parameters through intelligent learning of the AI large model, dependence on personal experience of a machine owner is reduced, and quality stability is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of printing color management, and particularly relates to a color reproduction control method and system for an offset printing press. Background Art

[0002] Color management has two aspects of significance: one is determined by the basic requirements of traditional color reproduction, that is, the basic settings and selections (including tone reproduction, gray balance, color correction, etc.) are made according to the color reproduction characteristics determined by paper, ink and other printing conditions, and the purpose is to make the conditions of color separation and printing adaptable; the other is the automatic color management based on a desktop publishing system or a graphic design system, that is, the color calibration of devices is carried out in a software manner, the characteristics of different color spaces are characterized, and color transfer is carried out for different input devices to achieve the best color matching.

[0003] In printing color management, the implementation of color management is divided into three steps: calibration, device characterization, and color conversion. Calibration refers to correcting each device in the printing production process, standardizing process parameters, and making it work in a stable state; device characterization means that on the premise of calibrating the device, color data is measured through various software and hardware tools and a color characteristic file of the device is generated to record the gamut characteristics of the device. Generally, there are three types of color characteristic files, namely, characteristic files of input devices, display devices, and output devices. The third step is to use a color management module to perform the conversion of device-related color spaces (such as CMYK, RGB, etc.) through a device-independent color space (Lab) to achieve the consistency of color output throughout the process from prepress to printing. In these three steps, calibration and device characterization are the keys to the effective implementation of color management. Calibration is not just a simple correction of each device, but a comprehensive diagnosis of the printing production process and technology, and the standardization and standardization of printing production process parameters.

[0004] In the process of color management of an offset printing press, color calibration needs to be carried out frequently at regular intervals, with a large workload and high requirements for the stable state of the printing press and the quality stability of printing consumables. However, the state of the printing press is constantly changing, so it is very difficult to implement. It can only rely on the experience of the press operator to adjust, which reduces production efficiency and is easily affected by human factors, resulting in unstable printing quality. Moreover, in order to facilitate the observation of the printing quality of printed matter, it is necessary to reserve a test strip position at the edge of the paper, wasting paper and increasing costs. Summary of the Invention

[0005] The purpose of the present invention is to overcome the existing defects and provide a color reproduction control method and system for an offset printing press.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: A color reduction control method for an offset printing press includes: S1: Detect the easy-to-control parameters and real-time changing parameters of the printing press to obtain real-time printing parameters; S2: Horizontally divide the printed electronic file into several regions with the same number as the ink zones of the printing press. Each region corresponds to an ink zone of the printing press, and select the color positions of representative colors in each region; S3: Use a printed matter scanning device to scan the printed sample. On the premise that the pH value of the dampening solution, the CMYK four-color registration is appropriate, and the printing dot size is reasonable, detect the color chromaticity of the representative color in each ink zone of the printed sample, and compare it with the color chromaticity of the customer-approved sample manuscript, and calculate the color difference variable of each ink zone between the printed sample and the customer-approved sample manuscript; S4: Collect the change amount of the ink fountain opening of each ink zone by the press operator, and use the AI large model to learn the relationship between the change amount of the ink fountain opening degree of each ink zone and the corresponding color difference variable; S5: Use a printed matter scanning device to perform real-time scanning and detection on the subsequent printed matter of the printing press. When the color difference variable between the printed matter and the customer-approved sample manuscript exceeds the preset threshold, the AI large model generates the ink key adjustment data of each ink zone according to the relationship between the change amount of the ink fountain opening degree of each ink zone and the corresponding color difference variable; S6: Generate a JDF file with the ink key adjustment data of each ink zone and send it to the control system of the printing press for corresponding adjustment, or generate a real-time printing press operation instruction diagram according to the JDF file to guide the operator for adjustment.

[0007] Further, in step S1, the easy-to-control parameters include ink viscosity, ink chromaticity, paper whiteness, and paper density, as well as the temperature and humidity of the environment where the printing press is located; The real-time changing parameters include the pH value of the dampening solution, the elastic coefficient of the blanket or the number of impression times, and the CMYK four-color registration situation.

[0008] Further, in step S3, the adjustment methods for CMYK four-color registration and printing dot size include: S31: Use a printed matter scanning device to detect the CMYK four-color registration data and printing dot size data of the printed sample; S32: Transmit the CMYK four-color registration data and printing dot size data to the printing press, and control the registration adjustment mechanism and printing pressure adjustment mechanism of the printing press to make corresponding adjustments; S33: After printing again, use a printed matter scanning device to detect the CMYK four-color registration data and printing dot size data of the printed matter again. If it is unqualified, return to step S32 until the adjustment is qualified.

[0009] Further, in step S3, the color chromaticity of the representative color in each ink zone of the printed proof is detected and compared with the color chromaticity of the customer-approved sample proof, and the color difference variables of each ink zone between the printed proof and the customer-approved sample proof are calculated, including: Convert the scanned file of the printed proof and the customer-approved sample proof from the RGB color gamut space to the Lab color gamut space to obtain the L value, a value, and b value of the representative color in each ink zone of both, compare the standard deviation of the color chromaticity values of both, obtain the color difference variables ΔL, Δa, and Δb of each ink zone, and calculate the total color difference △E between the two.

[0010] Further, during the learning process of the AI large model, each combination of variables is learned for one learning cycle. The variables in the variable combination include the number of types of common inks, the temperature range and humidity range in different seasons, and the number of types of common papers; The types of common inks are classified according to the viscosity and chromaticity of the inks, the types of common papers are classified according to the whiteness and density of the papers, and one learning cycle is the total number of impression times from when a new blanket starts to be used until the end of the blanket's life.

[0011] Another object of the present invention is to provide a color reproduction control system for an offset printing machine, including: A data detection module for real-time detection of ink, paper, dampening solution pH value data, environmental temperature and humidity data, as well as the number of impression times of the blanket and the ink key adjustment data of each ink zone of the printing press; A printed matter scanning module for detecting the CMYK four-color registration data and dot size data of the printed matter; A control module for collecting the state parameters of the printing press and the real-time data obtained by the data detection module, and controlling the printed matter scanning module; An AI large model module for using the AI large model to learn the change amount of the opening of each ink fountain for the printing machine operator for different color difference variables, obtain the relationship between the change amount of the ink fountain opening degree of each ink zone and the corresponding color difference variables, and generate the ink key adjustment data of each ink zone according to the real-time color difference variables. The color difference variables are the color difference variables of each ink zone between the printed matter and the customer-approved sample proof; A result output module for generating a JDF file according to the ink key adjustment data of each ink zone obtained by the AI large model, and transmitting the JDF file to the control system of the printing press for corresponding adjustment or generating a real-time printing press operation instruction diagram according to the JDF file to guide the operator for adjustment.

[0012] Further, the data detection module includes an ink chromaticity detection unit, an ink concentration detection unit, a paper whiteness detection unit, a paper density detection unit, a dampening solution pH value detection unit, an ambient temperature and humidity detection unit, and an impression cylinder impression times detection unit.

[0013] Further, the printed matter scanning module includes: A color detection unit for detecting the color of the printed matter using a spectrophotometer; A microscope detection unit for detecting the dot diameter and CMYK four-color registration of the printed matter.

[0014] Combined with the above technical solutions, the beneficial effects of the present invention compared with the prior art are as follows: By monitoring the status of the printing press and the status of consumables in real time, the present invention can obtain the color transfer characteristics of the printing press under different states and the different states of consumables through the intelligent learning of the AI large model. It can intelligently control the operation of the printing press according to the detected real-time parameters, convert manual experience into reusable algorithms, has a high degree of automation, reduces the dependence on the personal experience of the press operator, and ensures the stability of quality.

[0015] By horizontally partitioning the electronic file, each area corresponding to the ink zone of the printing press, and selecting representative color positions, the present invention realizes local refined control. By real-time monitoring the easy-to-control and real-time changing parameters of the printing press and combining the AI large model to adjust the control strategy, it can adapt to the dynamic changes of the printing press state.

[0016] By directly scanning and detecting the printed matter, the present invention eliminates the need for paper reservation for traditional test strips, reduces material waste and costs, and replaces manual repeated color calibration with automatic color recognition, shortens the production interruption time, and improves production efficiency.

[0017] By outputting the printing industry general data format (JDF) to transfer adjustment instructions, the present invention can be seamlessly docked with the existing control system of the printing press, has high compatibility, and for printing equipment that cannot be externally connected to an input port, it can also generate a real-time printing press operation instruction diagram to guide the operator for adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation to the present invention. In the drawings: Figure 1 is a flowchart of the color restoration control method of the offset printing press provided by the embodiment of the present invention; Figure 2 is a flowchart of the adjustment method for CMYK four-color registration and printing dot size provided by the embodiment of the present invention. Figure 3 It is the structural schematic diagram of the color reproduction control system of the offset printing machine provided by the embodiment of the present invention; In the figure: 1. Data detection module; 2. Printed matter scanning module; 3. Control module; 4. AI large model module; 5. Result output module; 11. Ink chromaticity detection unit; 12. Ink concentration detection unit; 13. Paper whiteness detection unit; 14. Paper density detection unit; 15. Fountain solution pH value detection unit; 16. Ambient temperature and humidity detection unit; 17. Blanket impression times detection unit; 21. Color detection unit; 22. Microscope detection unit. Specific embodiments

[0019] The following describes the preferred embodiments of the present invention with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0020] Embodiment 1: As Figure 1 shown, it is an embodiment of the color reproduction control method and system of the offset printing machine provided by the embodiment of the present invention, including: S1: Detect the easy-to-control parameters and real-time change parameters of the printing machine to obtain real-time printing parameters; S2: Horizontally divide the printed electronic file into several regions with the same number as the ink zones of the printing machine. Each region corresponds to an ink zone of the printing machine, and select the color positions of representative colors in each region; S3: Use the printed matter scanning device to scan the printed sample. On the premise that the pH value of the fountain solution, the CMYK four-color registration is appropriate, and the printing dot size is reasonable, detect the color chromaticity of the representative colors in each ink zone of the printed sample, and compare it with the color chromaticity of the customer's confirmed sample, and calculate the color difference variable of each ink zone between the printed sample and the customer's confirmed sample; S4: Collect the change amount of the ink fountain opening of each ink zone by the press operator, and use the AI large model to learn the relationship between the change amount of the ink fountain opening degree of each ink zone and the corresponding color difference variable; S5: Use the printed matter scanning device to perform real-time scanning and detection on the subsequent printed matter of the printing machine. When the color difference variable between the printed matter and the customer's confirmed sample exceeds the preset threshold, the AI large model generates the ink key adjustment data of each ink zone according to the relationship between the change amount of the ink fountain opening degree of each ink zone and the corresponding color difference variable; S6: Generate a JDF file with the ink key adjustment data of each ink zone and send it to the control system of the printing machine for corresponding adjustment, or generate a real-time printing machine operation instruction diagram according to the JDF file to guide the operator for adjustment.

[0021] Preferably, in step S1 of the embodiment of the present invention, the easily controllable parameters include ink viscosity, ink chromaticity, paper whiteness and paper density, as well as the temperature and humidity of the environment where the printing press is located; The real-time changing parameters include the pH value of the dampening solution, the elastic coefficient of the blanket or the number of impression times, and the CMYK four-color registration condition.

[0022] As Figure 2 shown, in step S3 of the embodiment of the present invention, the method for adjusting CMYK four-color registration and the size of printing dots includes: S31: Detect the CMYK four-color registration data and the printing dot size data of the printed proof by using a printed matter scanning device; S32: Transmit the CMYK four-color registration data and the printing dot size data to the printing press, and control the register adjustment mechanism and the printing pressure adjustment mechanism of the printing press to make corresponding adjustments; S33: After printing again, use the printed matter scanning device to detect the CMYK four-color registration data and the printing dot size data of the printed matter again. If it is unqualified, return to step S32 until the adjustment is qualified.

[0023] It should be noted that the adjustable mechanisms of the printing press include a plate pulling mechanism, a front guide and side guides for paper, a pH value adjustment mechanism for the dampening solution, an ink fountain opening mechanism, and a printing pressure adjustment mechanism. Among them, the plate pulling mechanism, the front guide and side guides for paper are mainly used to adjust the CMYK four-color registration. The pH value adjustment mechanism for the dampening solution is used to maintain the pH value of the dampening solution within a reasonable range. When adjusting the ink fountain opening mechanism and the printing pressure adjustment mechanism under the condition that the plate pulling mechanism, the front guide and side guides for paper, and the pH value adjustment mechanism for the dampening solution all meet the requirements, the color will change within a certain range.

[0024] Preferably, in step S3 of the embodiment of the present invention, detect the color chromaticity of the representative color in each ink zone of the printed proof, compare it with the color chromaticity of the customer's approved proof, and calculate the color difference variable of each ink zone between the printed proof and the customer's approved proof, including: Convert the scanned file of the printed proof and the customer's approved proof from the RGB color gamut space to the Lab color gamut space, obtain the L value, a value, and b value of the representative color in each ink zone of the two, compare the standard deviation of the color chromaticity values of the two, obtain the color difference variables ΔL, Δa, Δb of each ink zone, and calculate the total color difference △E between the two.

[0025] It should be noted that the Lab mode is a theoretical mode for recording light colors. CIE (Commission Internationale de L'Eclairage) is the abbreviation of the International Commission on Illumination, which formulates international standards for measuring colors and measures color values. CIE has formulated , and values to measure color values, and this measurement method is called CIELAB.

[0026] represents lightness, varying from bright (when = 100) to dark (when = 0).

[0027] The value indicates that the color varies from green ( ).

[0028] The value indicates that the color varies from yellow ( ).

[0029] After using this system, any color can find a corresponding position on its chart.

[0030] △E is the magnitude of the total color difference, representing the distance between the color spaces of two colors, used to represent the total color difference and establish a quantitative color tolerance. Usually, △E is calculated in a perceptually uniform chromaticity space.

[0031] Color difference formula: △L = L 样品 - L 标准， represents the lightness difference; △a = a 样品 - a 标准， represents the red / green difference; △b = b 样品 - b 标准， represents the yellow / blue difference; A large △L indicates a tendency towards white, and a small △L indicates a tendency towards black; A large △a indicates a tendency towards red, and a small △a indicates a tendency towards green; A large △b indicates a tendency towards yellow, and a small △b indicates a tendency towards blue.

[0032] .

[0033] As an optimization, during the learning process of the AI large model in the embodiments of the present invention, each variable combination is respectively subjected to a learning cycle of learning. The variables in the variable combination include the number of types of common inks, the temperature range and humidity range in different seasons, and the number of types of common papers; The types of the common inks are classified according to the viscosity and chromaticity of the inks, the types of the common papers are classified according to the whiteness and density of the papers, and the learning cycle is from the start of using a new blanket to the end of its service life, with the total number of impressions being one learning cycle.

[0034] It should be noted that since there are many combinations in the learning cycle, methods such as induction, reasoning, regression, decision tree, etc. can be used to infer the results of some combinations. By testing the rationality of the reasoning through actual applications, the learning cycle can be greatly reduced and the learning effect can be improved.

[0035] Embodiment 2: As Figure 3 shown, the color reproduction control system of an offset printing machine provided by the embodiment of the present invention includes: A data detection module 1, which is used to detect in real time the data of inks, papers, the pH value of dampening solution, environmental temperature and humidity data, as well as the number of impressions of the blanket and the ink key adjustment data of each ink zone of the printing machine; A printed matter scanning module 2, which is used to detect the CMYK four-color registration data and dot size data of the printed matter; A control module 3, which is used to collect the state parameters of the printing machine and the real-time data obtained by the data detection module, and control the printed matter scanning module; An AI large model module 4, which is used to utilize the AI large model to learn the change amount of the opening of each ink fountain for each ink zone by the printer operator for different color difference variables, obtain the relationship between the change amount of the opening degree of each ink fountain and the corresponding color difference variable, and generate the ink key adjustment data of each ink zone according to the real-time color difference variable, where the color difference variable is the color difference variable of each ink zone between the printed matter and the customer's confirmed sample; A result output module 5, which is used to generate a JDF file according to the ink key adjustment data of each ink zone obtained by the AI large model, and transmit the JDF file to the control system of the printing machine for corresponding adjustment or generate a real-time printing machine operation instruction diagram according to the JDF file to guide the operator for adjustment.

[0036] Preferably, the data detection module 1 in the embodiment of the present invention includes an ink chromaticity detection unit 11, an ink concentration detection unit 12, a paper whiteness detection unit 13, a paper density detection unit 14, a dampening solution pH value detection unit 15, an environmental temperature and humidity detection unit 16, and a blanket impression number detection unit 17.

[0037] Preferably, the printed matter scanning module 2 in the embodiment of the present invention includes: A color detection unit 21, which is used to detect the color of the printed matter by using a spectrophotometer; A microscope detection unit 22, which is used to detect the dot diameter and CMYK four-color registration situation of the printed matter.

[0038] It should be understood that although each step in the flowcharts of the embodiments of the present invention is shown sequentially as indicated by the arrows, these steps are not necessarily executed sequentially in the order indicated by the arrows. Unless there is a clear indication in the present invention, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, at least a part of the steps in each embodiment may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or sub-steps or stages of other steps.

[0039] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A color reproduction control method for an offset printing machine, characterized in that, The method includes: S1: Detect the easy-to-control parameters and real-time changing parameters of the printing press to obtain real-time printing parameters; S2: Horizontally divide the printed electronic file into several regions with the same number as the ink zones of the printing press. Each region corresponds to an ink zone of the printing press, and select the color positions of representative colors in each region; S3: Use a printed matter scanning device to scan the printed sample. On the premise that the pH value of the dampening solution, the CMYK four-color registration is appropriate, and the printing dot size is reasonable, detect the color chromaticity of the representative color in each ink zone of the printed sample, compare it with the color chromaticity of the customer-approved sample, and calculate the color difference variable of each ink zone between the printed sample and the customer-approved sample; S4: Collect the change amount of the ink fountain opening for each ink zone by the printing press operator, and use the AI large model to learn the relationship between the change amount of the ink fountain opening degree of each ink zone and the corresponding color difference variable; S5: Use a printed matter scanning device to perform real-time scanning and detection on the subsequent printed matter of the printing press. When the color difference variable between the printed matter and the customer-approved sample exceeds the preset threshold, the AI large model generates the ink key adjustment data for each ink zone according to the relationship between the change amount of the ink fountain opening degree of each ink zone and the corresponding color difference variable; S6: Generate a JDF file from the ink key adjustment data of each ink zone and send it to the control system of the printing press for corresponding adjustment, or generate a real-time printing press operation instruction diagram according to the JDF file to guide the operator for adjustment.

2. The color reproduction control method of the offset printing machine according to claim 1, characterized in that In step S1, the easy-to-control parameters include ink viscosity, ink chromaticity, paper whiteness, and paper density, as well as the temperature and humidity of the environment where the printing press is located; The real-time changing parameters include the pH value of the dampening solution, the elastic coefficient of the blanket or the number of impression times, and the CMYK four-color registration situation.

3. The color reproduction control method of the offset printing machine according to claim 1, characterized in that, In the said step S3, the adjustment methods for CMYK four-color registration and printing dot size include: S31: Use a printed matter scanning device to detect the CMYK four-color registration data and printing dot size data of the printed sample; S32: Transmit the CMYK four-color registration data and printing dot size data to the printing press, and control the registration adjustment mechanism and printing pressure adjustment mechanism of the printing press to make corresponding adjustments; S33: After printing again, use a printed matter scanning device to detect the CMYK four-color registration data and printing dot size data of the printed matter again. If it is unqualified, return to step S32 until the adjustment is qualified.

4. The color reproduction control method of the offset printing machine according to claim 1, wherein In the said step S3, detecting the color chromaticity of the representative color in each ink zone of the printed sample, comparing it with the color chromaticity of the customer-approved sample, and calculating the color difference variable of each ink zone between the printed sample and the customer-approved sample includes: Convert the scanned file of the printed sample and the customer-approved sample from the RGB color gamut space to the Lab color gamut space, obtain the L value, a value, and b value of the representative color in each ink zone of both, compare the standard deviation of the color chromaticity values of both, obtain the color difference variables ΔL, Δa, Δb of each ink zone, and calculate the total color difference △E of both.

5. The color reproduction control method of the offset printing machine according to claim 1, characterized in that, During the learning process of the AI large model, each combination of variables is learned for one learning cycle. The variables in the variable combination include the number of types of common inks, the temperature range and humidity range in different seasons, and the number of types of common papers. The types of common inks are divided according to the viscosity and chromaticity of the inks, and the types of common papers are divided according to the whiteness and density of the papers. The learning cycle is based on the total number of imprints from when a new blanket starts to be used until the end of the blanket's life as one learning cycle.

6. A color reproduction control system for an offset printing machine, characterized in that, The system includes: A data detection module for real-time detection of ink, paper, fountain solution pH value data, environmental temperature and humidity data, the number of imprints of the blanket, and the ink key adjustment data for each ink zone of the printing press. A printed matter scanning module for detecting the CMYK four-color registration data and dot size data of the printed matter. A control module for collecting the status parameters of the printing press and the real-time data obtained by the data detection module, and controlling the printed matter scanning module. An AI large model module for using the AI large model to learn the change amount of the ink fountain opening for each ink zone by the printing press operator for different color difference variables, obtaining the relationship between the change amount of the ink key opening for each ink zone and the corresponding color difference variables, and generating the ink key adjustment data for each ink zone according to the real-time color difference variables. The color difference variables are the color difference variables for each ink zone between the printed matter and the customer-approved sample proof. A result output module for generating a JDF file according to the ink key adjustment data for each ink zone obtained by the AI large model, and transmitting the JDF file to the control system of the printing press for corresponding adjustments or generating a real-time printing press operation instruction diagram according to the JDF file to guide the operator for adjustments.

7. The color reproduction control system of the offset printing machine according to claim 6, characterized in that, The data detection module includes an ink chromaticity detection unit, an ink concentration detection unit, a paper whiteness detection unit, a paper density detection unit, a fountain solution pH value detection unit, an environmental temperature and humidity detection unit, and a blanket imprint number detection unit.

8. The color reproduction control system of the offset printing machine according to claim 6, characterized in that, The printed matter scanning module includes: A color detection unit for detecting the color of the printed matter using a spectrophotometer. A microscope detection unit for detecting the dot diameter and CMYK four-color registration of the printed matter.

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