RFID aluminum foil front and back color register control method and system

Abstract

The invention relates to the technical field of image processing and printing, and discloses an RFID aluminum foil front and back color register control method and system, and the method comprises the steps: obtaining a first color code position and a second color code position of a target printing pattern, and calculating an initial color code distance; a mathematical model is established through parameters such as the circumference of a printing plate and the distance between color cells, a first pre-overprinting position and a second pre-overprinting position are calculated, and pre-overprinting setting is carried out; in the color register process, the color register image of the printing material is detected in real time, the color code distance is obtained, error analysis is carried out, printing equipment parameters are adjusted according to errors, and accurate color register control is achieved. According to the invention, the precision and efficiency of the front and back color register of the RFID aluminum foil can be effectively improved, and the production cost and the rejection rate are obviously reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of image processing and printing, and more specifically to a method and system for controlling the color registration of the front and back sides of an RFID aluminum foil. Background Art

[0002] With the continuous development of RFID technology, RFID tags are widely used in logistics management, identity recognition and other fields. RFID tags are usually composed of aluminum foil antennas and chips, and the aluminum foil antennas need to be made by gravure printing. In the gravure printing production of RFID aluminum foil antennas, color registration accuracy is one of the key factors affecting product quality. At present, the research on the color registration control of the front and back sides of RFID aluminum foil mainly focuses on the following aspects: The Chinese patent with publication number CN113665241A discloses an automatic registration method and device. This method uses trigger targets and sensors as triggers, collects target registration target images at precise times through image acquisition equipment, and calculates the registration deviation value in combination with physical quantities such as the stretching amount of the printing material, and adjusts the color registration parameters in real time to improve printing accuracy. However, this method is mainly aimed at color registration control of single-sided printing, and does not involve the particularity of printing on the front and back sides of RFID aluminum foil. How to achieve accurate color registration in double-sided printing still needs further research.

[0003] The Chinese patent with publication number CN118386674A proposes a color registration electronic axis control system and method based on machine vision, which uses a camera to collect color mark images, calculate registration errors, and send error information to the servo driver for compensation. The system realizes the automatic control of the color registration process and improves the color registration efficiency. However, in actual production, the printing material characteristics and printing environment of RFID aluminum foil are complex and changeable. It is difficult to obtain a stable and reliable color registration effect by relying solely on visual inspection, and a more sophisticated control method is required.

[0004] In summary, the existing technology lacks a color control method specifically targeting the printing characteristics of the front and back sides of RFID aluminum foil in terms of color control of the front and back sides of RFID aluminum foil, and it is difficult to meet the accuracy requirements of double-sided printing. Summary of the invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method and system for controlling the color registration of the front and back sides of RFID aluminum foil, which can accurately control the color registration deviation of the front and back sides of RFID aluminum foil and adapt to complex printing conditions, so as to improve the production quality and efficiency of RFID tags.

[0006] To achieve the above object, the present invention provides the following technical solutions: The method for controlling the color registration of the front and back sides of RFID aluminum foil includes: Obtaining a first color mark position and a second color mark position of a target printing pattern, and calculating an initial color mark spacing according to the first color mark position and the second color mark position; obtaining a printing plate perimeter and a color group distance, and calculating a first pre-overprint position and a second pre-overprint position according to the printing plate perimeter and the color group distance, and performing pre-overprint settings according to the first pre-overprint position and the second pre-overprint position; According to the pre-printing settings, the front and back sides of the RFID aluminum foil are color-registered. During the color-registering process, the color-registering image of the printing material is obtained, and the measured color mark spacing between the first color mark and the second color mark is obtained according to the color-registering image; the color-registering control is performed according to the measured color mark spacing and the initial color mark spacing.

[0007] Furthermore, the step of acquiring the first color mark position and the second color mark position of the target printing pattern includes: Acquire image information of a target printing pattern, and mark it as a target printing image; the target printing pattern includes a first target printing pattern and a second target printing pattern; the target printing image includes a first image and a second image; Processing the target printing image to identify a first color mark and a second color mark in the target printing image; the first color mark is a color reference circle in the front printing pattern, and the second color mark is a color reference circle in the back printing pattern; A first reference coordinate of the first color mark in the target printing image is determined as the first color mark position, and a second reference coordinate of the second color mark in the target printing image is determined as the second color mark position.

[0008] Furthermore, the step of acquiring the image information of the target printed pattern includes: Collecting image information of a first target printing pattern printed by a first printing plate, and marking it as a first image; Image information of a second target printing pattern printed by a second printing plate is collected and marked as a second image.

[0009] Further, the calculating the first pre-printing position and the second pre-printing position comprises: Obtain the circumference L1 of the first printing plate and the circumference L2 of the second printing plate, and take the average of L1 and L2 as the circumference L of the printing plate; Obtaining a distance D between the first printing plate color group and the second printing plate color group, and using D as the color group distance; Obtaining a feeding speed V of the printing material and geometrical dimension parameters of the color group pattern; the geometrical dimension parameters include a length a1 of the first color group pattern, a width b1 of the first color group pattern, a length a2 of the second color group pattern, and a width b2 of the second color group pattern; According to the plate circumference L, color group distance D, feed speed V and geometric size parameters of color group pattern, a mathematical model of pre-registration position is established; The mathematical model of the pre-printing position is solved to obtain the first pre-printing position X1 and the second pre-printing position X2.

[0010] Further, the pre-printing setting includes: Rotate the first printing plate and the second printing plate to the reference origin; Taking the reference origin as the starting point, the first printing plate is rotated to the first pre-registering position, and the second printing plate is rotated to the second pre-registering position.

[0011] Furthermore, the step of obtaining the color image of the printing material includes: The initial rotation speed of the second printing plate axis is set, and during the color registration process, the position information of the printing material is detected in real time, and when the printing material reaches the preset photographing position, the color registration image of the printing material is obtained; The color image includes a PU1 color image and a PU2 color image.

[0012] Further, obtaining the measured color mark spacing between the first color mark and the second color mark includes: Performing image processing on the PU1 color image and the PU2 color image to obtain a PU1 color precision image and a PU2 color precision image; Locate the first color mark in the PU1 color set precision map, and obtain the measured position coordinates of the first color mark, which are recorded as the first measured color mark position; Locate the second color mark in the PU2 color set precision image, and obtain the measured position coordinates of the second color mark, which are recorded as the second measured color mark position; According to the first measured color mark position and the second measured color mark position, the measured distance between the two color marks is calculated and recorded as the measured color mark distance.

[0013] Further, obtaining the measured position coordinates of the first color mark includes: Divide the PU1 color image into two parts: the color mark area and the non-color mark area; In the segmented color mark area, the contour features of the first color mark are extracted to obtain the edge pixel set of the first color mark. ; Calculate the geometric center coordinates of the first color mark based on the edge pixel set of the first color mark ; The geometric center coordinates of the first color scale As the center, sub-pixel edge detection is performed in its neighborhood to obtain a high-precision edge coordinate set of the first color scale; Perform ellipse fitting on the high-precision edge coordinate set of the first color mark to obtain the sub-pixel geometric center coordinates of the first color mark ( ), recorded as the first measured color mark position.

[0014] Furthermore, the color registration control according to the measured color mark spacing and the initial color mark spacing includes: The measured color mark spacing is compared with a preset spacing threshold. If the measured color mark spacing is less than or equal to the preset spacing threshold, the initial rotation speed of the second printing plate axis is maintained; if the measured color mark spacing is greater than the preset spacing threshold, the deviation between the measured color mark spacing and the initial color mark spacing is calculated to obtain the color mark spacing deviation; According to the color mark spacing deviation, the adjustment value of the second printing plate shaft rotation speed is calculated; according to the adjustment value of the second printing plate shaft rotation speed, the initial rotation speed of the second printing plate shaft is adjusted to generate the target rotation speed of the second printing plate shaft.

[0015] An RFID aluminum foil front and back color matching control system is used to implement the above-mentioned RFID aluminum foil front and back color matching control method, and the system includes: Analysis module: used to obtain the first color mark position and the second color mark position of the target printing pattern, and calculate the initial color mark spacing according to the first color mark position and the second color mark position; obtain the circumference of the printing plate and the color group distance, and calculate the first pre-overprint position and the second pre-overprint position according to the circumference of the printing plate and the color group distance; Pre-printing module: performs pre-printing settings according to the first pre-printing position and the second pre-printing position; Real-time detection module: According to the pre-printing settings, the front and back sides of the RFID aluminum foil are overprinted. During the overprinting process, the overprint image of the printing material is obtained, and the measured color mark spacing between the first color mark and the second color mark is obtained according to the overprint image; Color registration control module: performs color registration control based on the measured color mark spacing and the initial color mark spacing.

[0016] An electronic device comprises a memory, a central processing unit and a computer program stored in the memory and executable on the central processing unit. When the central processing unit executes the computer program, the above-mentioned RFID aluminum foil front and back color matching control method is implemented.

[0017] A computer-readable storage medium stores a computer program, and when the computer program is executed, the above-mentioned RFID aluminum foil front and back color matching control method is implemented.

[0018] Compared with the prior art, the present invention has the following beneficial effects: By obtaining the color mark position of the target printing pattern and calculating the initial color mark spacing, a reference benchmark is provided for subsequent color registration control, which is conducive to improving the color registration accuracy. Parameters such as the plate circumference and color group distance are introduced, and a mathematical model of the pre-registering position is established to solve the pre-registering position, making the pre-registering more accurate and laying a good foundation for subsequent color registration. In the color registration process, the color registration image of the printing material is obtained in real time, and the measured color mark spacing is extracted through image processing, so that the color registration quality can be dynamically monitored. The measured color mark spacing is compared with the initial color mark spacing, and the second plate axis speed is dynamically adjusted accordingly, realizing closed-loop control, so that the color registration accuracy is significantly improved. Image processing algorithms such as sub-pixel edge detection and ellipse fitting are used to achieve high-precision positioning of the color mark, further improving the color registration accuracy. The overall closed-loop control method is adopted, and intelligent color registration is realized through software algorithms, which reduces manual intervention and improves production efficiency. At the same time, it can adapt to RFID aluminum foil color registration of different batches and models, and has good versatility and practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 The principle flow chart of the method for controlling the color registration of the front and back sides of RFID aluminum foil in the present invention; Figure 2 It is a flow chart of a method for obtaining image information of a target printed pattern in the RFID aluminum foil front and back color matching control method of the present invention; Figure 3 It is a flow chart of a method for calculating the first pre-printing position and the second pre-printing position in the RFID aluminum foil front and back color control method of the present invention; Figure 4 It is a flow chart of a method for performing pre-printing setting in the RFID aluminum foil front and back color control method of the present invention; Figure 5 It is a flow chart of a method for obtaining a measured color mark spacing between a first color mark and a second color mark in the RFID aluminum foil front and back color matching control method of the present invention; Figure 6 It is a flow chart of a method for obtaining the measured position coordinates of the first color mark in the RFID aluminum foil front and back color matching control method of the present invention; Figure 7 It is a functional module diagram of the RFID aluminum foil front and back color matching control system in the present invention. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example 1 See also Figure 1 As shown, this embodiment provides a method for controlling the color registration of the front and back sides of RFID aluminum foil, including: Step S1000, obtaining a first color mark position and a second color mark position of a target printing pattern, calculating an initial color mark spacing according to the first color mark position and the second color mark position, obtaining a printing plate perimeter and a color group distance, calculating a first pre-overprint position and a second pre-overprint position according to the printing plate perimeter and the color group distance, and performing pre-overprint settings according to the first pre-overprint position and the second pre-overprint position; Furthermore, step S1000 includes: Step S1100, obtaining a first color mark position and a second color mark position of a target printing pattern; Furthermore, if Figure 2 As shown, step S1100 includes: Step S1110, acquiring image information of a target printing pattern, and marking it as a target printing image; the target printing pattern includes a first target printing pattern and a second target printing pattern; the target printing image includes a first image and a second image; Further, step S1110 includes: Step S1111, using the first printing plate PU1 to print a pattern to obtain a first target printing pattern; Step S1112, using the second printing plate PU2 to print a pattern to obtain a second target printed pattern; Step S1113, collecting image information of the first target printing pattern and marking it as a first image; Step S1114, collecting image information of the second target printing pattern and marking it as a second image.

[0023] Specifically, PU1 is a printing plate specially used for printing patterns on the front side of the material, usually made of materials such as rubber or photolithography resin. PU1 is engraved with a gravure with a front pattern. When PU1 comes into contact with the printing material and applies a certain pressure, the ink is transferred from the pattern part of the gravure to the printing material to form a front pattern. The first target printing pattern is the pattern presented on the front side of the printing material after PU1 is printed, including the color reference circle (first color mark). PU2 is a printing plate specially used for printing patterns on the back side of the material. Its structure and working principle are similar to PU1, except that the reverse pattern is engraved on the gravure. After the printing material is printed by PU1, PU2 is printed on the reverse side to form the second target printing pattern, which includes the reverse color reference circle (second color mark).

[0024] After PU1 is printed, a high-speed camera is used to take a picture of the front pattern to obtain a clear digital image of the first target printed pattern, which is marked as the first image and saved. The first image contains the position information of the first color mark. After the material is printed by PU2, a high-speed camera is used to take a picture of the back pattern to obtain a digital image of the second target printed pattern, which is marked as the second image. The second image contains the position information of the second color mark.

[0025] For example: suppose you want to print an RFID antenna. There is a circle with a diameter of 2mm on the front side as the color reference circle, and there is also an identical color reference circle on the back side. First, use PU1 to print on the front side of the material to obtain a front pattern containing a 2mm color reference circle. This is the first target printing pattern. The high-speed camera shoots the front side, and the digital image obtained is the first image. Then the material is printed by PU2, and a reverse pattern containing a 2mm color reference circle is formed on the reverse side. This is the second target printing pattern. The second image can be obtained by shooting with a high-speed camera.

[0026] Step S1100 can accurately obtain the position coordinate information of the first color mark and the second color mark in the target printed pattern by taking photos and collecting them. Since the color mark is a specific mark in the printed pattern, it represents the spatial reference of the front and back patterns. By comparing the position deviation of the front and back color marks, the color registration error can be quantified. This provides a reliable data basis for subsequent error compensation. In addition, by obtaining color mark information through high-speed video and photography, real-time monitoring and feedback control of the production process can be achieved, which is conducive to improving color registration accuracy.

[0027] Step S1120, processing the target printing image, identifying a first color mark and a second color mark in the target printing image; the first color mark is a color reference circle in the front printing pattern, and the second color mark is a color reference circle in the back printing pattern; Step S1130, determining a first reference coordinate of the first color mark in the target printing image as the first color mark position, and determining a second reference coordinate of the second color mark in the target printing image as the second color mark position.

[0028] Specifically, step S1120 mainly extracts the characteristic information of the color reference circle from the first image and the second image through an image processing algorithm. The first color mark is identified from the first image; the second color mark is identified from the second image. Commonly used methods include: Image binarization: Convert a color or grayscale image into a black and white binary image so that the color reference circle has a clear contrast with the background.

[0029] Morphological operation: through morphological operations such as erosion and dilation, the image noise is eliminated and the edge of the color reference circle is repaired.

[0030] Hough circle transform: Using the principle of Hough transform, the image is voted in the parameter space to detect the circular color reference circle.

[0031] Contour extraction: Based on the edge detection algorithm, the contour curve of the color reference circle is extracted and its geometric features are calculated.

[0032] Through these image processing means, the first color mark in the first image and the second color mark in the second image can be accurately located.

[0033] For example: When printing a batch of RFID tags, the diameter of the color reference circle on both the front and back sides is 2mm. After printing on both sides, the front and back images are processed separately. First, the image is binarized so that the 2mm circular area appears white and the other areas are black. Then the Hough circle transform is used to detect the position of the circle and extract the coordinates of the center of the circle. In this way, the first reference coordinate representing the front color mark and the second reference coordinate representing the back color mark can be obtained.

[0034] Select the center coordinates of the color registration reference circle as the reference coordinates.

[0035] By executing steps S1120 and S1130, the target printing image is processed and the positions of the first color mark and the second color mark are identified, which can significantly improve the color registration accuracy and control efficiency during the printing process, thereby achieving high-quality front and back overprinting effects.

[0036] Step S1120 extracts the first color mark and the second color mark features in the target printed image through image processing algorithms (such as image binarization, morphological operations, Hough circle transform, etc.), and determines the geometric coordinates of the color mark center as the reference position in step S1130. This processing method can effectively eliminate the positioning deviation caused by image noise, printing errors or material defects, and ensure that the recognition accuracy of the color mark position reaches the sub-pixel level. Through precise color mark positioning, the distance between the front and back color marks can be accurately calculated, providing high-quality basic data for subsequent compensation of color registration errors. This high-precision processing method is particularly suitable for fields such as RFID tags that have extremely high requirements for registration accuracy, and can effectively reduce error accumulation and ensure accurate alignment of the front and back patterns.

[0037] Through high-speed cameras and automated image processing technology, steps S1120 and S1130 can capture color mark images and quickly extract color mark positions in real time during the production process, avoiding delays and errors caused by traditional manual measurement and adjustment. This real-time performance ensures dynamic adjustment capabilities during the printing process, allowing the system to respond promptly to displacement, deformation or other external interference of printed materials and maintain the stability of color registration accuracy. Especially in mass production, this automated processing significantly improves production efficiency, reduces the need for manual intervention, and reduces the errors that may be introduced by manual operation.

[0038] Through accurate color mark recognition and position determination, steps S1120 and S1130 can significantly reduce the misalignment in the front and back overprinting, and improve the consistency and appearance quality of the product. This is especially important for high-end printing products that require fine pattern alignment (such as RFID tags, packaging printing, and security anti-counterfeiting printing). High-precision overprint control not only improves the pass rate of a single batch of products, but also reduces the scrap rate, saves materials and production costs, and thus improves the overall production efficiency.

[0039] Step S1200, calculating an initial color mark spacing according to the first color mark position and the second color mark position; Specifically, the initial color mark spacing refers to the actual distance between the first color mark and the second color mark on the printing material after the printing material is printed on both sides. This distance is a quantitative value calculated by mathematical formula after obtaining the color mark position information of the front and back printed patterns through an image acquisition device (such as a high-speed camera). The initial color mark spacing provides a reference value for subsequent color registration error detection. The subsequent actual color mark spacing is compared with the initial color mark spacing to determine whether the printing parameters need to be adjusted. By quantitatively describing the positional relationship between the color marks, the alignment accuracy between the front and back patterns during the printing process is ensured. The spacing is the Euclidean distance between the center points of the two color marks, expressed as the geometric distance of the coordinates of the two points.

[0040] The initial color mark spacing provides a reference value for color registration control. By detecting the actual color mark spacing in real time and comparing it with the initial value, the printing plate position can be adjusted in time to ensure that the front and back patterns are aligned. The calculation of the initial color mark spacing is completely dependent on automated equipment and algorithms, without manual intervention, thereby reducing human errors and improving production efficiency. By accurately calculating the color mark spacing and monitoring it in real time during the subsequent process, the color registration error can be effectively reduced and the consistency and quality of the product can be improved. This method is suitable for color registration control of different materials and patterns and has strong versatility. For example, for complex RFID tags or precision circuit boards, this method can also provide reliable precision control.

[0041] Step S1300, obtaining the circumference of the printing plate and the color group distance, and calculating the first pre-printing position and the second pre-printing position according to the circumference of the printing plate and the color group distance; the color group includes the first printing plate color group and the second printing plate color group; Furthermore, if Figure 3 As shown, step S1300 includes: Step S1310, obtaining the perimeter L1 of the first printing plate and the perimeter L2 of the second printing plate, and taking the average of L1 and L2 as the perimeter L of the printing plate; Specifically, the plate circumference refers to the outer circumference of the plate cylinder, which is used to describe the length covered by the plate cylinder to complete a full rotation. This is a core parameter in the printing process, which affects the repeatability and accuracy of printing. By measuring the diameter of the first plate and the second plate, and then multiplying by π, L1 and L2 can be calculated respectively. The average value of the two is taken as the plate circumference L. By taking the average value L, the circumference parameters of the two plate cylinders can be unified, the subsequent calculation model can be simplified, and the introduction of complex compensation algorithms due to small size differences can be avoided. The unified setting of the circumference L improves the calculation efficiency, especially in automated control. This simplified processing reduces the complexity of real-time calculations.

[0042] Step S1320, obtaining a distance D between the first printing plate color group and the second printing plate color group, and using D as the color group distance; A color group refers to two adjacent groups of printed patterns on a printed material, where each group of patterns is printed by one printing plate. The distance between color groups (i.e., color group distance) is the spatial interval between two adjacent patterns on the printing material, reflecting an important parameter for printing alignment.

[0043] The obtaining of the distance D between the first printing plate color group and the second printing plate color group comprises: Get the center coordinates of the first plate color group , the center position coordinates of the second printing plate color group , the area of ​​the first printing plate color group , the area of ​​the second printing plate color group ; according to , , and , calculate the distance D between the first printing plate color group and the second printing plate color group.

[0044] in: : The horizontal coordinate of the center position of the first printing plate color group; : The vertical coordinate of the center position of the first printing plate color group; Indicates the geometric center of the first printing plate color group; : The horizontal coordinate of the center position of the second printing plate color group; : The vertical coordinate of the center position of the second printing plate color group; Indicates the geometric center of the second printing plate color group; : The rotation angle of the first printing plate color group (based on the angle with the X axis); : The rotation angle of the second plate color group (based on the angle with the X axis); the rotation angle reflects the degree of rotation of the color group relative to the standard direction. This parameter affects the relative position of the two color groups in space; : Weight coefficient of the rotation angle; controls the effect of the rotation angle on the distance D; : Weight coefficient of color group area; controls the influence of color group area on distance D; , It can be obtained through image processing algorithms, usually by image segmentation or edge detection to obtain the center position of the color group, or by directly measuring the geometric center of the color group through sensors or positioning devices. Significance: These coordinate values ​​reflect the spatial position of the color group, which is usually closely related to printing accuracy and alignment. Rotation angle , It can be obtained by extracting the boundary of the color group or calculating it through image processing algorithms (such as Hough transform). The rotation angle is used to describe the rotation of the color group relative to the reference axis (such as the X axis). The difference in rotation angle will affect the alignment of the color group. Especially in precision printing, the deviation of the angle will cause the pattern to be misaligned. Area and It can be obtained through image analysis, by counting the number of pixels in the color group area or by measuring the actual size of the color group through a sensor. The area reflects the size of the color group, and size differences may cause alignment problems, especially when the size difference between color groups is large, which may cause overlap or gaps during printing. , It is usually determined by empirical data or expert knowledge and adjusted according to actual production needs.

[0045] The relationship between the variables of the formula and the dependent variable: Dependent Variable : Color group distance It is determined by various factors (position, rotation, area). As these factors change, the distance between color groups will change.

[0046] Location :If the center positions of the two color groups change, the distance will change based on the straight-line distance between them.

[0047] Rotation Angle :As the rotation angle changes, The greater the difference in the rotation angle between the two color groups, the greater the distance will be more affected.

[0048] area :Area differences affect distance , especially when the area difference between the two color groups is large, it may cause a larger position deviation, resulting in a larger distance value.

[0049] The formula not only considers the geometric distance between color groups, but also the rotation angle and area difference. This makes the distance calculation between color groups more comprehensive and adaptable to different printing situations. In particular, when there are certain rotation or size differences between color groups, the formula can more accurately reflect the difficulty of color group alignment. In actual printing, the change in rotation angle and the area difference of color groups have an important impact on the final printing effect. By introducing the difference in rotation angle and area, the calibration of the printing press can be better adjusted to ensure the accurate alignment of the color groups during the printing process. The weight coefficients α and β can be adjusted according to actual needs, and the formula can be flexibly configured according to different production requirements. By adjusting the weight coefficients, a balance can be found between alignment accuracy and production speed.

[0050] Step S1330, obtaining a feeding speed V of the printing material and geometrical dimension parameters of the color group pattern; the geometrical dimension parameters include a length a1 of the first color group pattern, a width b1 of the first color group pattern, a length a2 of the second color group pattern, and a width b2 of the second color group pattern; Specifically, the feed speed V refers to the speed at which the printing material passes through the printing press, and the unit is generally meters per minute. It can be calculated from the radius of the plate cylinder and the speed of the plate cylinder. The length and width of the color group pattern refer to the circumscribed rectangular dimensions of a single pattern, represented by a1, b1, a2, and b2, respectively, in millimeters. These dimensions can be obtained by analyzing the design draft or directly measuring the printed sample using a measuring tool. The introduction of geometric dimension parameters is to describe the size characteristics of the color group pattern and incorporate them into the calculation of the pre-overprint position. Different pattern sizes have different requirements for the pre-rotation angle of the printing plate. Accurately obtaining these parameters is to ensure the synchronization of the printed pattern and the rotation of the cylinder to avoid overprint deviation due to speed or size mismatch.

[0051] Step S1340, establishing a pre-registration position mathematical model according to the circumference L of the printing plate, the color group distance D, the feed speed V and the geometric size parameters of the color group pattern; The pre-registration position mathematical model includes: subject to: Wherein, X1 is the first pre-printing position, and X2 is the second pre-printing position; is the objective function, which consists of two parts: Part I Indicates the distance between two pre-printing positions and the color group distance The deviation is the weight coefficient of the first part. The optimization goal of this part is to make the distance of the pre-printing position as close as possible to the color group distance, so as to ensure the overprinting accuracy.

[0052] Part 2 Indicates the deviation between the displacement of the printing material and the total length of the color group pattern, where Indicates the theoretical displacement of the printing material in the pre-registration position. Represents the total length of the two color group patterns, is the weight coefficient of the second part. The optimization goal of this part is to make the displacement of the printing material match the pattern length to avoid the offset of the overprint position and the pattern.

[0053] The constraints of the model dictate that the pre-register locations must be within the perimeter of their respective plates.

[0054] By minimizing the objective function, a set of optimal X1 and X2 values, namely the first pre-printing position and the second pre-printing position, can be obtained.

[0055] Step S1350, solving the pre-printing position mathematical model to obtain the first pre-printing position X1 and the second pre-printing position X2.

[0056] Specifically, common optimization algorithms include gradient descent, Newton's method, quasi-Newton's method, genetic algorithm, particle swarm algorithm, etc. Gradient descent is an iterative optimization algorithm used to minimize the objective function. right and The partial derivative of and until the objective function converges to the minimum. Newton's method is an optimization algorithm based on second-order derivatives, which is suitable for situations where the objective function is continuous and smooth. It uses the second-order derivative information of the objective function to accelerate convergence, but the computational complexity is high. The quasi-Newton method is an improved Newton's method that does not require the calculation of second-order derivatives. Instead, it constructs the second-order derivative matrix of the objective function through an approximate method, which is suitable for high-dimensional optimization problems. Genetic algorithm is a global optimization algorithm based on natural selection and genetic mechanisms, which is suitable for nonlinear and non-convex optimization problems, but has a slow convergence speed. Particle swarm optimization is an optimization algorithm based on group search that simulates the foraging behavior of bird flocks and is suitable for complex multi-objective optimization problems.

[0057] Step S1350 solves the mathematical model through the optimization algorithm, theoretically ensuring the best initial state of the printing system. Combined with the automatic control and real-time adjustment functions, it can effectively improve the printing quality and reduce the scrap rate, and is suitable for a variety of high-precision printing scenarios, such as RFID tags, packaging printing, etc.

[0058] Step S1400, performing pre-printing settings according to the first pre-printing position and the second pre-printing position.

[0059] Furthermore, if Figure 4 As shown, step S1400 includes: Step S1410, rotating the first printing plate and the second printing plate to a reference origin; Specifically, the servo motor of the PU1 plate is controlled to rotate the PU1 plate until the preset origin mark on the PU1 plate is aligned with the origin sensor at a fixed position. It is usually a small hole, groove, reflective sticker or laser engraved mark engraved on the plate to mark the starting position of the plate. The origin sensor can be a photoelectric sensor or a proximity switch, etc. When the origin mark is detected by the origin sensor, the control system receives the signal and stops the rotation of the PU1 plate. At this time, the angular position of the PU1 plate is defined as 0°, that is, the reference origin. Using a similar method to the PU1 plate, the servo motor of the PU2 plate is controlled to rotate the PU2 plate until the origin mark on the PU2 plate is aligned with the corresponding origin sensor. The angular position of the PU2 plate is also defined as the reference origin, that is, 0°.

[0060] A servo motor is a motor that can precisely control the rotation angle and speed. It is commonly used in the field of industrial automation. The encoder can detect the angular position of the motor shaft in real time, thereby achieving closed-loop control. An encoder is a sensor that converts the angular position or speed of the motor shaft into a digital signal. Common encoders include incremental encoders and absolute encoders. When used with a servo motor, the movement of the motor can be precisely controlled.

[0061] By setting an origin mark on the printing plate and using a sensor for detection, the absolute zero point of the angular position of the printing plate can be established. This method overcomes the problem of accumulated angle errors. Before each printing begins, the printing plate position can be recalibrated to the reference origin to ensure overprint accuracy. The use of servo motors and encoders greatly improves the accuracy and repeatability of the printing plate angle control. General servo systems can limit the error of angle control to within ±0.1°, and with high-resolution encoders, high-precision detection and feedback control of the printing plate position can be achieved. Step S1410 establishes a unified reference origin, laying the coordinate foundation for subsequent pre-overprint control. Through the precise coordination of mechanical and electrical components, the calibration and resetting functions of the printing plate position are realized, which is one of the key links in realizing the entire automatic overprint system.

[0062] Step S1420, taking the reference origin as the starting point, the first printing plate is rotated to the first pre-printing position, and the second printing plate is rotated to the second pre-printing position.

[0063] Specifically, the first pre-printing position (denoted as X1) is the position relative to the reference origin, and the unit is angle (°), which indicates the displacement that the first printing plate needs to rotate from the reference origin; by controlling the rotation of the servo motor, the first printing plate (PU1) is rotated from the reference origin (0°) to the X1 position.

[0064] The calculation formula for the rotation angle is: Rotation Angle If X1 is a positive value, it indicates clockwise rotation; if X1 is a negative value, it indicates counterclockwise rotation.

[0065] In order to eliminate the deviation caused by mechanical error, insufficient encoder accuracy or material slip, the system will make dynamic adjustments based on real-time feedback data. For example, if the actual rotation angle detected by the encoder deviates from the target value X1, the control system will compensate by adjusting the pulse signal of the servo motor until the error value is lower than the set threshold.

[0066] For example, assuming that the mathematical model of the pre-print position calculates that the first pre-print position X1 is 72°, first rotate the servo motor of the PU1 printing plate to the reference origin (0°), and then control the servo motor to rotate 72° to the first pre-print position according to the X1 value instruction. The encoder monitors the angle in real time. If it actually rotates to 71.8°, the system will continue to compensate 0.2° to ensure that the final position is 72°.

[0067] The second pre-register position (denoted as X2) refers to the position of the second printing plate (PU2) relative to its reference origin; the working principle of the PU2 servo motor is the same as that of PU1, but since the movement of the material between PU1 and PU2 will produce a certain displacement and deformation, the pre-register position (X2) of PU2 needs to be corrected in real time based on these factors. The system dynamically adjusts the position of the PU2 printing plate by comparing the encoder signals of PU1 and PU2 and the feed speed of the material.

[0068] For example, assume that the mathematical model of the pre-print position calculates that the second pre-print position X2 is 68.5°. The PU2 servo motor first rotates to the reference origin (0°), and then rotates with 68.5° as the target position. If the material slips slightly between PU1 and PU2, the system will compensate by monitoring the slip amount ΔX in real time. For example, if the slip amount is detected to be 0.5°, the final rotation target position is corrected to 69°.

[0069] By defining the reference origin and combining the high-precision control of the servo motor and encoder, the rotation position of the printing plate is ensured to be completely consistent with the preset target. By introducing encoder feedback and error compensation mechanism, deviations caused by material slippage, mechanical errors, etc. can be corrected in real time to maintain the stability of overprint accuracy. The automated pre-overprint process reduces manual intervention and improves production efficiency. High-precision overprinting reduces scrap rate, thereby reducing material waste and production costs.

[0070] Step S2000, according to the pre-printing settings, the front and back sides of the RFID aluminum foil are color-coded. During the color-coding process, a color-coding image of the printing material is obtained, and the measured color-coding distance between the first color code and the second color code is obtained according to the color-coding image; and color-coding control is performed according to the measured color-coding distance and the initial color-coding distance.

[0071] Furthermore, step S2000 includes: Step S2100, setting the initial rotation speed of the second printing plate shaft, performing RFID aluminum foil front and back color registration, during the color registration process, detecting the position information of the printing material in real time, and obtaining the color registration image of the printing material when the printing material reaches the preset photographing position; the color registration image includes the PU1 color registration image and the PU2 color registration image; Specifically, in step S2100, according to the pre-printing settings, during the process of color registration of the front and back sides of the RFID aluminum foil, the position information of the printing material (RFID aluminum foil) needs to be detected in real time. When the printing material reaches the preset photographing position, the color registration images of the front and back sides of the printing material are obtained respectively. The detection of position information usually relies on sensors, such as photoelectric sensors, laser sensors or encoders. These sensors can accurately monitor the movement state of the printing material on the printing equipment to ensure that the camera is triggered to take pictures at the appropriate time. The preset photographing position refers to a fixed position set during the printing process to obtain a clear color registration image. This position is usually determined by the equipment through multiple tests during the installation or debugging phase to ensure that the camera can fully capture the target color mark pattern.

[0072] The initial rotation speed of the second printing plate shaft is set according to the matching relationship between the feeding speed of the printing material, the rotation speed of the first printing plate shaft and the front and back printing positions.

[0073] The initial rotation speed of the second printing plate axis needs to ensure that the substrate can be accurately aligned with the pattern of the second printing plate (PU2) when printing on the reverse side after the first printing plate (PU1) completes the printing on the front side. This alignment relationship is affected by the following factors: The speed at which the printing material moves between PU1 and PU2 (ie the feed speed).

[0074] The speed of the first plate axis (ie the speed of PU1).

[0075] The geometric position of the color reference pattern (the distance between the first color mark and the second color mark).

[0076] Plate circumference (the circumference of the first and second plates).

[0077] Therefore, the initial rotation speed of the second printing plate axis needs to be determined by calculation to ensure that the color reference patterns of the front and back printing patterns are aligned.

[0078] If the first plate (PU1) and the second plate (PU2) have different circumferences, their rotation speeds will also be different. This is because the rotation speed of the plate axis and its circumference directly affect the length of each printing cycle. The rotation speeds of the two plate axes also need to be synchronized with the feed speed of the substrate to ensure that the material remains compatible during the transfer between PU1 and PU2. If the feed speed changes, the rotation speed of the second plate axis also needs to be dynamically adjusted to match the new material movement speed. The position spacing of the color reference circle (first color mark and second color mark) between the front and back patterns affects the speed setting of the second plate axis. For example, if the second plate needs to adjust the spatial alignment of the printed pattern, the error compensation may be achieved by adjusting the rotation speed of the second plate axis. During the color registration process, the rotation speed of the second plate axis is usually not fixed, but needs to be adjusted according to the actual printing deviation. For example, by comparing the measured first color mark position and the second color mark position (i.e. the center of the PU1 and PU2 patterns), the deviation is calculated and the rotation speed of PU2 is adjusted to correct the error.

[0079] Although the rotation speeds of the first and second plate axes may be different, they need to maintain strict synchronization to ensure accurate alignment of the front and back patterns. The following are the key points of the synchronization mechanism: (1) Synchronization via feed speed The feed speed of the printing material is the basis for the synchronization of the two. The rotation speeds of the first plate axis and the second plate axis will be dynamically adjusted according to the feed speed.

[0080] (2) Maintaining synchronization through color control During the color registration process, the deviation between the first color mark and the second color mark is detected in real time, and the rotation speed of the second printing plate shaft is adjusted according to the deviation to ensure the alignment of the printed patterns on the front and back sides.

[0081] The color image refers to the image data containing the color reference mark after the printing material is printed, which records the printed patterns on the front and back sides respectively. The acquisition of the color image is completed by an industrial camera, which is installed in a specific position to capture the color mark information printed on the PU1 and PU2 printing plates in real time. The U1 printing plate is responsible for front printing. The PU1 color image refers to the image data collected by the camera after the front of the printing material is printed, including the information of the first color mark (front color reference circle). The PU2 printing plate is responsible for back printing. The PU2 color image refers to the image data collected by the camera after the back of the printing material is printed, including the information of the second color mark (back color reference circle).

[0082] The plate shaft refers to the rotating shaft in the printing press that carries the plate and is used for printing. The initial rotation speed refers to the default rotation speed of the plate shaft at the beginning of printing. The rotation speed of the plate shaft directly affects the alignment of the printed pattern and the substrate. During the color registration process, the initial rotation speed must match the feed speed of the substrate to ensure the integrity and accuracy of the printed pattern.

[0083] The camera is a key device for collecting color registration images. It is usually a high-resolution industrial camera that can quickly capture high-quality image information and perform subsequent processing in the software system. The camera needs to be accurately aimed at the PU1 plate area to ensure that the image information containing the first color mark is captured. The first color mark on the PU1 plate is the color registration reference mark printed on the front. By collecting its image information, the position coordinates of the first color mark can be obtained. The camera is aimed at the PU2 plate area to collect the second color mark information in the reverse printing pattern. By collecting the PU2 color registration image, the specific position of the second color mark can be further determined.

[0084] Printing materials are prone to jitter and offset during high-speed printing. Real-time monitoring can compensate for these dynamic changes by adjusting the time point of taking photos, ensuring that the image acquisition is consistent with the actual printing position. During the process of color registration of the front and back sides of RFID aluminum foil, the synchronization of the photo taking and printing process can be ensured by real-time detection of the position information of the printing materials. This real-time monitoring can effectively reduce the deviation caused by material displacement or equipment error. The sensor detects the position information and triggers the camera to take photos to ensure that the collected color registration image is complete and clear. By aligning the industrial camera with the PU1 and PU2 printing plates and collecting the color registration images after printing on the front and back sides at the same time, the position coordinates of the color marks on the front and back sides can be accurately obtained. High-resolution cameras can capture subtle image details, and combined with subsequent image processing algorithms (such as binarization, morphological operations, Hough circle transform, etc.), sub-pixel color mark positioning can be achieved. By collecting the PU1 and PU2 color registration images and obtaining the position information of the first color mark and the second color mark respectively, the actual spacing between the front and back color marks (i.e., the measured color mark spacing) can be calculated. By comparing the measured color mark spacing with the initial color mark spacing, the alignment accuracy of the front and back patterns can be determined, thereby guiding the subsequent color registration error compensation and plate shaft speed adjustment. Through automated image acquisition and real-time analysis technology, step S2100 can quickly detect and adjust the overprint accuracy during the production process, avoiding delays and errors caused by human operation, thereby improving production efficiency. In addition, real-time monitoring and dynamic adjustment can significantly reduce the occurrence of overprint errors, reduce scrap rates, and save material costs. Step S2100 is suitable for application scenarios such as RFID tags that have extremely high requirements for overprint accuracy. By real-time acquisition of color registration images and high-precision image processing algorithms, accurate alignment of the front and back patterns can be achieved to meet the quality requirements of high-end printing products.

[0085] Step S2100 is applicable to application scenarios such as RFID tags that require extremely high overprinting accuracy. By real-time acquisition of overprinting images and high-precision image processing algorithms, accurate alignment of the front and back patterns can be achieved to meet the quality requirements of high-end printing products.

[0086] Step S2200, analyzing the color registration image to obtain a measured color mark spacing between the first color mark and the second color mark; Furthermore, if Figure 5 As shown, step S2200 includes: Step S2210, performing image processing on the PU1 color image and the PU2 color image to obtain a PU1 color image and a PU2 color image; Specifically, the core task of step S2210 is to denoise the original color image collected by PU1 and PU2 so as to generate a clear and easy-to-analyze color image. A combined filtering method of Gaussian filtering, median filtering and bilateral filtering is adopted. Gaussian filtering is a low-pass filter that smoothes the image by weighted averaging the pixel values ​​in the image, and the weight is determined by the Gaussian function. It has a suppressive effect on high-frequency noise (such as random noise) and can retain the overall structural characteristics of the image. Gaussian filtering retains the edge features of the image while smoothing the noise, and is particularly effective for Gaussian noise (such as noise generated by the sensor). Median filtering is a nonlinear filtering method that can effectively remove salt and pepper noise (random black and white spots) by taking the median of the pixel values ​​in the local window to replace the central pixel value. Median filtering has a strong suppressive effect on salt and pepper noise and does not introduce additional blur like Gaussian filtering. Bilateral filtering combines spatial similarity and pixel value similarity, smoothes the image by considering both spatial weight and pixel value weight, and retains edge details while denoising. While smoothing the noise, it can well preserve the edge features of the image, which is especially suitable for images with strong noise.

[0087] The presence of noise will lead to the loss or confusion of high-frequency information (such as edges and details) in the image, so denoising is required. Denoising can eliminate the interference of background noise, making the edges of the color mark clearer and with higher contrast, thus providing convenient conditions for subsequent color mark positioning. Gaussian filtering targets random noise, median filtering targets salt and pepper noise, and bilateral filtering targets the retention of edge features. The combination of the three can fully cope with various types of noise. The denoised image retains the edge features of the color mark area, making subsequent edge detection and geometric center calculation more accurate, thereby ensuring the high-precision requirements of overprint control.

[0088] Step S2220, locating the first color mark in the PU1 color set precision image, obtaining the measured position coordinates of the first color mark, recorded as the first measured color mark position; Furthermore, if Figure 6As shown, step S2220 includes: Step S2221, dividing the PU1 color image into two parts: a color mark area and a non-color mark area; Specifically, the adaptive threshold segmentation algorithm is used to segment the PU1 color image into two parts: the color-coded area and the non-color-coded area. The adaptive threshold segmentation automatically determines the segmentation threshold according to the local features of the image, which can effectively segment the target area, and can achieve good results even when the lighting conditions change or the background is complex. Commonly used adaptive threshold segmentation algorithms include the Otsu algorithm and the maximum entropy threshold algorithm. The Otsu algorithm calculates the gray value distribution of each pixel in the image and finds a threshold so that the intra-class variance of the foreground (target area) and the background is minimized, that is, the inter-class variance is maximized. It is suitable for the case of uniform image illumination and has high computational efficiency. The maximum entropy threshold algorithm is based on the concept of information theory and finds a threshold so that the entropy (i.e., the amount of information) of the foreground and background is maximized. It is more stable than the Otsu algorithm when the image brightness distribution is uneven.

[0089] First, the PU1 color image is converted into a grayscale image to reduce the computational complexity. Different thresholds are determined in each local window by the adaptive threshold segmentation algorithm to separate the target area from the background area. A binary image is generated, in which the target area is represented by white and the background area is represented by black.

[0090] Through the adaptive threshold segmentation algorithm, the color mark area can be accurately extracted in an environment with complex lighting and background changes without being affected by global lighting changes. The use of the Otsu algorithm or the maximum entropy threshold algorithm can improve the robustness and automation of segmentation and avoid subjective errors caused by manual adjustment of the threshold. The segmented image can significantly reduce the amount of subsequent calculations and focus on feature extraction of the color mark area.

[0091] Step S2222: extract the contour features of the first color mark in the segmented color mark area to obtain the edge pixel set of the first color mark. ; Step S2223, calculating the geometric center coordinates of the first color mark according to the edge pixel set of the first color mark ; Specifically, the purpose of extracting the contour features of the color mark is to accurately determine the boundaries of the color mark and obtain a set of edge pixels, laying the foundation for subsequent calculation of the geometric center and high-precision positioning. Contour extraction can use edge-based algorithms such as the Canny algorithm and the Sobel algorithm. Taking the Canny algorithm as an example, its basic steps are as follows: (1) Perform Gaussian filtering on the image to remove noise.

[0092] (2) Calculate the gradient magnitude and direction of the image in the x and y directions.

[0093] (3) Perform non-maximum suppression on the gradient amplitude and retain the edge points corresponding to the local maximum.

[0094] (4) Use the double threshold method to screen and connect edge points to obtain a complete edge contour.

[0095] Through the Canny algorithm, the color mark boundary can be accurately extracted while removing noise, reducing the impact of pseudo edges on subsequent calculations. The edge pixel set provides basic data for geometric center calculation and high-precision fitting, and its accuracy directly determines the reliability of subsequent processing. Non-maximum suppression and dual threshold method enhance the robustness of edge detection, making the results more suitable for complex printed images.

[0096] The geometric center coordinates reflect the approximate position of the first color mark in the image, but due to the limitations of discrete pixels, their accuracy is limited. Therefore, the geometric center coordinates are used as the initial position for subsequent sub-pixel positioning.

[0097] Step S2224, using the geometric center coordinates of the first color mark As the center, sub-pixel edge detection is performed in its neighborhood to obtain a high-precision edge coordinate set of the first color scale; Specifically, sub-pixel edge detection is a refined processing of traditional edge detection, which can improve the accuracy of edge coordinates from pixel level to sub-pixel level. Commonly used sub-pixel edge detection algorithms include sub-pixel Canny algorithm, curve fitting algorithm, etc.

[0098] The sub-pixel Canny algorithm is an improvement on the traditional Canny algorithm. It achieves sub-pixel accurate positioning of edge positions through interpolation and curve fitting. The curve fitting algorithm obtains sub-pixel edge coordinates by fitting the curve to the edge pixels in segments, calculating the inflection point or tangent of the curve. The core of sub-pixel positioning is to use the continuity of the pixel grayscale value to infer the position of the real edge, rather than relying solely on discrete pixels. Sub-pixel edge detection can significantly improve the accuracy of edge coordinates and provide high-quality data for ellipse fitting. By processing only a small range near the geometric center, the amount of calculation can be reduced while improving the reliability of positioning.

[0099] Step S2225, performing ellipse fitting on the high-precision edge coordinate set of the first color mark to obtain the sub-pixel geometric center coordinates of the first color mark ( ), recorded as the first measured color mark position.

[0100] Specifically, ellipse fitting is to optimize the edge coordinate set as a whole to obtain the best matching ellipse parameters, including the ellipse center, major semi-axis, minor semi-axis and rotation angle. Commonly used ellipse fitting algorithms include least squares method and Hough transform. The least squares method obtains the parameters of the ellipse by minimizing the sum of squares of the distances from the edge points to the fitted ellipse. The Hough transform uses the parameter space search method to determine the optimal ellipse parameters. Ellipse fitting can make full use of the global distribution characteristics of edge points to obtain a more robust center position. Sub-pixel center positioning provides a high-quality data basis for subsequent color scale spacing calculation and color registration accuracy control. The ellipse fitting method has a strong tolerance to noise and can still ensure high accuracy when the edge points are unevenly distributed.

[0101] Step S2220 realizes the high-precision sub-pixel positioning of the first color mark, and the positioning error is reduced from the pixel level to the sub-pixel level, which greatly improves the accuracy of the color mark position measurement. A variety of sub-pixel processing technologies, such as sub-pixel edge detection and curve fitting, are used to fully utilize the high-precision information in the image data and improve the positioning accuracy. The ellipse fitting takes into account the overall distribution of the color mark edge, has stronger robustness to outliers and noise, and the obtained color mark center position has sub-pixel accuracy. High-precision color mark positioning lays a solid foundation for the subsequent actual color mark spacing calculation and color registration control, which helps to improve the registration accuracy and printing quality.

[0102] Step S2220 introduces a variety of sub-pixel processing technologies into the printing color mark positioning. Through image preprocessing, sub-pixel edge detection, curve fitting and other means, high-precision sub-pixel positioning of the color mark center is achieved, and the ellipse fitting method is used to improve the robustness of positioning. The comprehensive application of these technologies has significantly improved the accuracy and reliability of color mark positioning, providing key technical support for high-quality printing control. At the same time, the technical ideas and implementation solutions adopted by this method also have certain reference significance for other machine vision applications that require high-precision target positioning.

[0103] Step S2230, locating the second color mark in the PU2 color set precision image, obtaining the measured position coordinates of the second color mark, recorded as the second measured color mark position; Step S2240: Calculate the measured distance between the two color marks according to the first measured color mark position and the second measured color mark position, and record it as the measured color mark distance.

[0104] Specifically, similar to the first measured color mark position, the method in step S2220 is used to obtain the second measured color mark position; the measured color mark spacing refers to the actual distance between the first color mark and the second color mark, and the calculation formula is the Euclidean distance between the two points. By calculating the measured color mark spacing, the relative position deviation of the front and back patterns can be quantified, providing basic data for subsequent color registration error analysis. Through high-speed cameras and automated image processing technology, the calculation of the measured color mark spacing can be completed in real time during the production process, thereby achieving rapid feedback and dynamic adjustment. The real-time calculation of the measured color mark spacing provides a basis for dynamically adjusting the plate axis, ensuring that high-quality front and back overprinting effects are always maintained in mass production.

[0105] Step S2300, comparing the measured color mark spacing with the preset spacing threshold, if the measured color mark spacing is less than or equal to the preset spacing threshold, maintaining the initial rotation speed of the second printing plate axis; if the measured color mark spacing is greater than the preset spacing threshold, executing step S2400; Specifically, the measured color mark spacing reflects the actual deviation of the current front and back overprinting. The preset spacing threshold is a quantitative indicator set according to the printing quality requirements and process level, and is usually determined by production process experts or quality management personnel based on historical data and experience. The size of the threshold needs to balance printing efficiency and printing accuracy. A too small threshold will frequently trigger adjustments and affect the production rhythm; a too large threshold will relax the deviation tolerance and reduce the overprint quality.

[0106] The measured color mark spacing collected in real time is compared with the preset threshold. If the measured spacing is less than or equal to the threshold, it means that the current overprint accuracy is within the acceptable range. At this time, the speed of the second printing plate axis (i.e. the reverse printing plate) remains unchanged and continues to print according to the original parameters. In this case, there is no need to adjust the speed, avoiding frequent parameter changes, which is conducive to maintaining the continuity and stability of equipment operation and improving production efficiency.

[0107] If the measured spacing is greater than the threshold, it indicates that the current overprint deviation has exceeded the allowable range, and the speed of the second plate axis needs to be adjusted in time to improve the overprint effect. At this time, step S2400 is automatically triggered to calculate the specific color mark spacing deviation to provide a basis for subsequent speed adjustment. By monitoring the overprint deviation in real time and comparing it with the preset threshold, this step can accurately determine whether intervention adjustment is needed, avoiding the problem of excessive adjustment or untimely adjustment, and improving production efficiency while ensuring printing quality.

[0108] Step S2300 achieves real-time monitoring and automatic judgment of color registration deviation by comparing the measured spacing with the preset threshold, which improves production efficiency while ensuring printing quality, reduces manual intervention, and provides a basis for subsequent speed adjustment. This method is particularly suitable for products with high requirements for registration accuracy, such as RFID tags, packaging printing, etc. By responding to deviations in a timely manner, it can significantly improve product qualification rate and delivery speed.

[0109] Step S2400, calculating the deviation between the measured color mark spacing and the initial color mark spacing to obtain the color mark spacing deviation; Specifically, the color mark spacing deviation refers to the absolute value of the difference between the measured color mark spacing and the initial color mark spacing. The measured color mark spacing represents the actual distance between the first color mark and the second color mark on the current printing material, and the initial color mark spacing represents the distance between the two color marks under ideal conditions. The color mark spacing deviation can quantitatively reflect the degree of difference between the current overprint state and the target state. A positive deviation means that the measured spacing is greater than the initial spacing, indicating that there is a certain misalignment in the current overprint; a negative deviation means that the measured spacing is less than the initial spacing, indicating that there may be overlap or incomplete printing problems. The size of the deviation is inversely proportional to the printing accuracy. The larger the deviation, the lower the overprint quality, and the printing parameters need to be adjusted in time.

[0110] By introducing the quantitative indicator of color mark spacing deviation, the registration accuracy can be accurately evaluated, providing a reliable basis for subsequent speed adjustment. Compared with simple threshold comparison, the deviation calculation takes into account the difference between the initial state and the current state, which can more accurately reflect the dynamic changes in the printing process and provide a data basis for precise control. Especially in batch production, by continuously tracking the deviation change trend, we can gain insight into the impact of equipment performance, material characteristics, environmental factors, etc. on color registration accuracy, thereby optimizing the production process and improving product consistency.

[0111] In addition, the feedback control method based on the deviation of the color mark spacing can significantly improve the adaptive ability of the color registration system. Traditional open-loop control often relies on parameters set by experience and is difficult to cope with various interferences in the production process. By measuring the deviation in real time and using it as a control input, the system can be dynamically adjusted according to the actual printing status, achieving closed-loop feedback, and greatly improving the robustness and adaptability of the control. This is particularly important for dealing with problems such as changes in the characteristics of the printing material, plate wear, and color consistency, and can ensure the stable output of high-quality overprint products in complex production environments.

[0112] In summary, step S2400 provides a quantitative basis for subsequent speed adjustment by calculating the color mark spacing deviation, which is a key step in achieving accurate color registration control. This method makes full use of online image acquisition and data processing technology, closely combines printing quality evaluation with process control, and reflects the intelligent and digital development direction of modern printing technology. Through accurate calculation and continuous tracking of deviations, production efficiency can be significantly improved and scrap rate can be reduced, which is of great significance to the quality control and cost management of printing companies.

[0113] Step S2500, calculate the adjustment value of the second plate shaft speed according to the color mark spacing deviation; adjust the initial speed of the second plate shaft according to the adjustment value of the second plate shaft speed, generate the target speed of the second plate shaft, and then return to step S2100 to continue color registration detection and control.

[0114] in: : The adjustment value of the second plate shaft speed, in rpm (revolutions per minute).

[0115] :Color mark spacing deviation, that is, the difference between the actual color mark spacing and the initial color mark spacing. The unit is millimeter (mm).

[0116] : Linear coefficient of color mark spacing deviation. It reflects the linear influence of color mark spacing deviation on the speed adjustment value. This parameter is obtained through empirical value or trial printing data fitting.

[0117] : The basic value of the speed adjustment value. That is, the speed adjustment value when the color mark spacing deviation is zero. This parameter is obtained through experience or historical data statistics.

[0118] : Nonlinear influence coefficient of color mark spacing deviation. It reflects the nonlinear influence of color mark spacing deviation on the speed adjustment value. This parameter is obtained by fitting the test printing data.

[0119] : Attenuation factor of the color mark spacing deviation. It controls the speed at which the nonlinear effect decays as the absolute value of the deviation increases. This parameter is selected according to the printing process characteristics and material properties.

[0120] : The periodic amplitude of the speed adjustment value. It reflects the periodic variation of the speed adjustment value with the deviation of the color mark spacing. This parameter is obtained through empirical value or trial printing data fitting.

[0121] : The periodic offset of the speed adjustment value. That is, the size of the periodic component when the color mark spacing deviation is zero. This parameter is obtained through empirical values ​​or historical data statistics.

[0122] : The periodic phase coefficient of the speed adjustment value. It controls the phase offset of the periodic component. This parameter is selected according to the dynamic characteristics of the printing equipment.

[0123] : The spatial frequency parameter of the periodic component. It determines the repetition period of the periodic component in the color mark spacing deviation domain. This parameter is selected according to the geometric size and material properties of the printing plate cylinder.

[0124] This formula comprehensively considers the linear effect, nonlinear attenuation effect, and periodic effect of the color mark spacing deviation on the speed adjustment value. When the deviation is large, the nonlinear component will gradually weaken the linear effect. At the same time, the periodic component introduces sinusoidal modulation to simulate the periodic errors that may occur in the actual printing process.

[0125] Through this formula, the rotation speed adjustment value of the second plate axis can be quickly calculated based on the detected color mark spacing deviation. By superimposing the adjustment value on the current rotation speed, the movement of the second plate can be dynamically optimized to better synchronize it with the first plate, thereby reducing the overprint error of the front and back printed patterns and improving printing accuracy. The weights of each item in the formula can be adjusted based on the test printing results to meet different printing process requirements.

[0126] When the color mark spacing deviation When the speed adjustment value changes Will also change accordingly: when When is small, the linear component dominates. and is approximately proportional. As it gradually increases, the nonlinear attenuation component will gradually weaken The impact of The growth rate gradually slows down. The periodic component introduces sinusoidal modulation, making Periodic fluctuations are superimposed on the overall trend to accommodate periodic disturbances that may occur during the printing process. Beyond a certain range, the nonlinear attenuation component dominates The change avoids excessive speed adjustment and is beneficial to maintaining printing stability.

[0127] In general, the formula can adaptively generate the adjustment value of the second plate axis speed according to the change of the color mark spacing deviation. By dynamically adjusting the plate axis speed, the accurate registration of the front and back printed patterns can be achieved, the printing error can be reduced, and the product quality can be improved. The derivation of the formula fully considers the complexity and variability of the printing process, and introduces a variety of influencing factors such as linearity, nonlinearity and periodicity, making the speed adjustment strategy more intelligent and robust. At the same time, the parameters in the formula can be optimized according to the actual printing effect to adapt to different materials, processes and equipment characteristics, and improve the adaptability and flexibility of overprint control.

[0128] The adjustment value refers to the amount of speed change required for the second plate axis (PU2 plate axis) calculated based on the deviation in the color mark spacing, usually in revolutions per minute (RPM). By adjusting the speed, the printing position of the PU2 plate can be changed, thereby correcting the overprint error. The speed of the second plate axis refers to the rotation speed of the servo motor used to drive the PU2 plate. Changes in speed will directly affect the printing position of the reverse pattern. Too fast or too slow speed may cause overprint deviation. The servo motor is the core component that controls the speed of the second plate axis and has high-precision speed adjustment capabilities. Through feedback mechanisms (such as encoder monitoring), the servo motor can adjust the speed in real time to ensure the stability of the printing system and overprint accuracy.

[0129] The target speed of the second plate shaft is calculated according to the adjustment value of the speed of the second plate shaft, for example, by adding the initial speed of the second plate shaft to the adjustment value; the adjusted target speed is used to drive the second plate shaft to reach a new printing position. The target speed is sent to the servo motor control system, and the servo motor adjusts the actual speed of the second plate shaft according to the instruction. The adjustment process adopts closed-loop control, that is, the speed of the second plate shaft is monitored in real time by the encoder, compared with the target speed, and gradually adjusted until the error is lower than the set threshold. After the speed adjustment is completed, the system returns to step S2100 to continue color registration detection and control. By real-time monitoring of the new color mark spacing, it is determined whether the overprinting effect meets the expectations. If there is still a deviation, repeat step S2500 to further adjust the speed of the second plate shaft until the overprinting accuracy meets the requirements.

[0130] By calculating the color mark spacing deviation in real time and adjusting the speed of the second printing plate shaft, the overprint error can be accurately corrected to ensure that the alignment accuracy of the front and back printed patterns reaches the sub-millimeter level. It can detect and adjust in real time during the printing process, dynamically compensate for deviations caused by material sliding, mechanical errors, etc., and avoid the accumulation of overprint errors. High-precision overprint control significantly reduces the scrap rate caused by overprint deviation, saving materials and production costs. The automated adjustment process avoids delays and errors caused by manual intervention, while ensuring the stability of printing quality. The above method is applicable to a variety of printing scenarios, especially in fields with extremely high requirements for overprint accuracy (such as RFID tags, packaging printing, etc.), and has strong versatility. Through the above calculation and adjustment method, step S2500 can quickly respond to deviation changes during the printing process, maintain the stability of the system and high-precision output, and significantly improve the overall production efficiency and product quality.

[0131] Example 2 This embodiment provides an RFID aluminum foil front and back color matching control system based on the embodiment 1, such as Figure 7 As shown, including: Analysis module: used to obtain the first color mark position and the second color mark position of the target printing pattern, and calculate the initial color mark spacing according to the first color mark position and the second color mark position; obtain the circumference of the printing plate and the color group distance, and calculate the first pre-overprint position and the second pre-overprint position according to the circumference of the printing plate and the color group distance; Pre-printing module: performs pre-printing settings according to the first pre-printing position and the second pre-printing position; Real-time detection module: According to the pre-printing settings, the front and back sides of the RFID aluminum foil are overprinted. During the overprinting process, the overprint image of the printing material is obtained, and the measured color mark spacing between the first color mark and the second color mark is obtained according to the overprint image; Color registration control module: performs color registration control based on the measured color mark spacing and the initial color mark spacing.

[0132] In the analysis module, obtaining the first color mark position and the second color mark position of the target printing pattern includes: Step S1110, acquiring image information of a target printing pattern, and marking it as a target printing image; the target printing pattern includes a first target printing pattern and a second target printing pattern; the target printing image includes a first image and a second image; Step S1120, processing the target printing image, identifying a first color mark and a second color mark in the target printing image; the first color mark is a color reference circle in the front printing pattern, and the second color mark is a color reference circle in the back printing pattern; Step S1130, determining a first reference coordinate of the first color mark in the target printing image as the first color mark position, and determining a second reference coordinate of the second color mark in the target printing image as the second color mark position.

[0133] The step S1110 includes: Step S1111, using the first printing plate PU1 to print a pattern to obtain a first target printing pattern; Step S1112, using the second printing plate PU2 to print a pattern to obtain a second target printed pattern; Step S1113, collecting image information of the first target printing pattern and marking it as a first image; Step S1114, collecting image information of the second target printing pattern and marking it as a second image.

[0134] In the analysis module, the calculating of the first pre-printing position and the second pre-printing position includes: Step S1310, obtaining the perimeter L1 of the first printing plate and the perimeter L2 of the second printing plate, and taking the average of L1 and L2 as the perimeter L of the printing plate; Step S1320, obtaining a distance D between the first printing plate color group and the second printing plate color group, and using D as the color group distance; Step S1330, obtaining a feeding speed V of the printing material and geometrical dimension parameters of the color group pattern; the geometrical dimension parameters include a length a1 of the first color group pattern, a width b1 of the first color group pattern, a length a2 of the second color group pattern, and a width b2 of the second color group pattern; Step S1340, establishing a pre-registration position mathematical model according to the circumference L of the printing plate, the color group distance D, the feed speed V and the geometric size parameters of the color group pattern; Step S1350, solving the pre-printing position mathematical model to obtain the first pre-printing position X1 and the second pre-printing position X2.

[0135] In the pre-printing module, performing pre-printing setting according to the first pre-printing position and the second pre-printing position includes: Step S1410, rotating the first printing plate and the second printing plate to a reference origin; Step S1420, taking the reference origin as the starting point, the first printing plate is rotated to the first pre-printing position, and the second printing plate is rotated to the second pre-printing position.

[0136] In the real-time detection module, the step of obtaining the color image of the printing material includes: The initial rotation speed of the second printing plate axis is set to perform color registration of the front and back sides of the RFID aluminum foil. During the color registration process, the position information of the printing material is detected in real time. When the printing material reaches the preset photographing position, the color registration image of the printing material is obtained; the color registration image includes the PU1 color registration image and the PU2 color registration image.

[0137] In the real-time detection module, obtaining the measured color mark spacing between the first color mark and the second color mark according to the color registration image includes: Step S2210, performing image processing on the PU1 color image and the PU2 color image to obtain a PU1 color image and a PU2 color image; Step S2220, locating the first color mark in the PU1 color set precision image, obtaining the measured position coordinates of the first color mark, recorded as the first measured color mark position; Step S2230, locating the second color mark in the PU2 color set precision image, obtaining the measured position coordinates of the second color mark, recorded as the second measured color mark position; Step S2240: Calculate the measured distance between the two color marks according to the first measured color mark position and the second measured color mark position, and record it as the measured color mark distance.

[0138] The step S2220 includes: Step S2221, dividing the PU1 color image into two parts: a color mark area and a non-color mark area; Step S2222: extract the contour features of the first color mark in the segmented color mark area to obtain the edge pixel set of the first color mark. ; Step S2223, calculating the geometric center coordinates of the first color mark according to the edge pixel set of the first color mark ; Step S2224, using the geometric center coordinates of the first color mark As the center, sub-pixel edge detection is performed in its neighborhood to obtain a high-precision edge coordinate set of the first color scale; Step S2225, performing ellipse fitting on the high-precision edge coordinate set of the first color mark to obtain the sub-pixel geometric center coordinates of the first color mark ( ), recorded as the first measured color mark position.

[0139] In the color registration control module, the color registration control according to the measured color mark spacing and the initial color mark spacing includes: The measured color mark spacing is compared with a preset spacing threshold. If the measured color mark spacing is less than or equal to the preset spacing threshold, the initial rotation speed of the second printing plate axis is maintained; if the measured color mark spacing is greater than the preset spacing threshold, the deviation between the measured color mark spacing and the initial color mark spacing is calculated to obtain the color mark spacing deviation; According to the color mark spacing deviation, the adjustment value of the second printing plate shaft rotation speed is calculated; according to the adjustment value of the second printing plate shaft rotation speed, the initial rotation speed of the second printing plate shaft is adjusted to generate the target rotation speed of the second printing plate shaft.

[0140] Example 3 This embodiment discloses an electronic device, which may include one or more processors and one or more memories, wherein the memories store computer-readable codes, and when the computer-readable codes are run by the one or more processors, the RFID aluminum foil front and back color matching control method as described above may be executed.

[0141] The method or system according to the embodiment of the present application can also be implemented with the help of the architecture of an electronic device. The electronic device may include a bus, one or more CPUs, a read-only memory (ROM), a random access memory (RAM), a communication port connected to a network, an input / output component, a hard disk, etc. The storage device in the electronic device, such as a ROM or a hard disk, can store the RFID aluminum foil front and back color registration control method provided in the present application. The RFID aluminum foil front and back color registration control method may, for example, include: obtaining the first color mark position and the second color mark position of the target printing pattern, and calculating the initial color mark spacing according to the first color mark position and the second color mark position; obtaining the circumference of the printing plate and the color group distance, and calculating the first pre-printing position and the second pre-printing position according to the circumference of the printing plate and the color group distance, and performing pre-printing settings according to the first pre-printing position and the second pre-printing position; performing RFID aluminum foil front and back color registration according to the pre-printing settings, and in the color registration process, obtaining the color registration image of the printing material, and obtaining the measured color registration spacing between the first color mark and the second color mark according to the color registration image; performing color registration control according to the measured color mark spacing and the initial color mark spacing.

[0142] Furthermore, the electronic device may also include a user interface. Of course, the architecture disclosed in the present invention is only exemplary, and when implementing different devices, one or more components in the electronic device disclosed in the present invention may be omitted according to actual needs.

[0143] Example 4 This embodiment discloses a computer-readable storage medium, on which computer-readable instructions are stored. When the computer-readable instructions are executed by a processor, the RFID aluminum foil front and back color matching control method of the embodiment of the present application can be executed. The storage medium includes, but is not limited to, for example, volatile memory and / or non-volatile memory. Volatile memory may include, for example, random access memory (RAM) and cache memory (cache). Non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc.

[0144] In addition, according to the implementation of the present application, the process described above with reference to the flowchart can be implemented as a computer software program. For example, the present application provides a non-transitory machine-readable storage medium, the non-transitory machine-readable storage medium stores machine-readable instructions, the machine-readable instructions can be run by a processor to execute instructions corresponding to the method steps provided in the present application, for example: obtaining the first color mark position and the second color mark position of the target printing pattern, and calculating the initial color mark spacing according to the first color mark position and the second color mark position; obtaining the perimeter of the printing plate and the color group distance, and calculating the first pre-printing position and the second pre-printing position according to the perimeter of the printing plate and the color group distance, and performing pre-printing settings according to the first pre-printing position and the second pre-printing position; performing RFID aluminum foil front and back color registration according to the pre-printing settings, and in the color registration process, obtaining the color registration image of the printing material, and obtaining the measured color mark spacing between the first color mark and the second color mark according to the color registration image; performing color registration control according to the measured color mark spacing and the initial color mark spacing. When the computer program is executed by a central processing unit (CPU), the above functions defined in the method of the present application are executed.

[0145] The methods, systems, and devices of the present application may be implemented in many ways. For example, the methods, systems, and devices of the present application may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above order of steps for the method is for illustration only, and the steps of the method of the present application are not limited to the order specifically described above unless otherwise specified. In addition, in some embodiments, the present application may also be implemented as programs recorded in a recording medium, which include machine-readable instructions for implementing the method according to the present application. Therefore, the present application also covers recording media storing programs for executing the method according to the present application.

[0146] In addition, the parts of the above-mentioned technical solutions provided in the embodiments of the present application that are consistent with the implementation principles of the corresponding technical solutions in the prior art are not described in detail to avoid excessive redundancy.

[0147] The specific implementation modes as described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation mode of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. RFID aluminum foil front and back color control method, characterized in that: The method comprises: Obtaining a first color mark position and a second color mark position of a target printing pattern, and calculating an initial color mark spacing according to the first color mark position and the second color mark position; obtaining a printing plate perimeter and a color group distance, and calculating a first pre-overprint position and a second pre-overprint position according to the printing plate perimeter and the color group distance, and performing pre-overprint settings according to the first pre-overprint position and the second pre-overprint position; According to the pre-printing settings, the front and back sides of the RFID aluminum foil are color-registered. During the color-registering process, the color-registering image of the printing material is obtained, and the measured color mark spacing between the first color mark and the second color mark is obtained according to the color-registering image; the color-registering control is performed according to the measured color mark spacing and the initial color mark spacing.

2. The RFID aluminum foil front and back color control method according to claim 1 is characterized in that: The step of obtaining the first color mark position and the second color mark position of the target printing pattern comprises: Acquire image information of a target printing pattern, and mark it as a target printing image; the target printing pattern includes a first target printing pattern and a second target printing pattern; the target printing image includes a first image and a second image; Processing the target printing image to identify a first color mark and a second color mark in the target printing image; the first color mark is a color reference circle in the front printing pattern, and the second color mark is a color reference circle in the back printing pattern; A first reference coordinate of the first color mark in the target printing image is determined as the first color mark position, and a second reference coordinate of the second color mark in the target printing image is determined as the second color mark position.

3. The RFID aluminum foil front and back color control method according to claim 2, characterized in that: The obtaining of the image information of the target printing pattern comprises: Collecting image information of a first target printing pattern printed by a first printing plate, and marking it as a first image; Image information of a second target printing pattern printed by a second printing plate is collected and marked as a second image.

4. The RFID aluminum foil front and back color control method according to claim 3 is characterized in that: The calculating of the first pre-printing position and the second pre-printing position comprises: Obtain the circumference L1 of the first printing plate and the circumference L2 of the second printing plate, and take the average of L1 and L2 as the circumference L of the printing plate; Obtaining a distance D between the first printing plate color group and the second printing plate color group, and using D as the color group distance; Obtaining a feeding speed V of the printing material and geometrical dimension parameters of the color group pattern; the geometrical dimension parameters include a length a1 of the first color group pattern, a width b1 of the first color group pattern, a length a2 of the second color group pattern, and a width b2 of the second color group pattern; According to the plate circumference L, color group distance D, feed speed V and geometric size parameters of color group pattern, a mathematical model of pre-registration position is established; The mathematical model of the pre-printing position is solved to obtain the first pre-printing position X1 and the second pre-printing position X2.

5. The RFID aluminum foil front and back color control method according to claim 1, characterized in that: The pre-printing setting includes: Rotate the first printing plate and the second printing plate to the reference origin; Taking the reference origin as the starting point, the first printing plate is rotated to the first pre-registering position, and the second printing plate is rotated to the second pre-registering position.

6. The RFID aluminum foil front and back color control method according to claim 1, characterized in that: The obtaining of the color image of the printing material comprises: The initial rotation speed of the second printing plate axis is set, and during the color registration process, the position information of the printing material is detected in real time, and when the printing material reaches the preset photographing position, the color registration image of the printing material is obtained; The color image includes a PU1 color image and a PU2 color image.

7. The RFID aluminum foil front and back color control method according to claim 6, characterized in that: The step of obtaining the measured color mark spacing between the first color mark and the second color mark comprises: Performing image processing on the PU1 color image and the PU2 color image to obtain a PU1 color precision image and a PU2 color precision image; Locate the first color mark in the PU1 color set precision map, and obtain the measured position coordinates of the first color mark, which are recorded as the first measured color mark position; Locate the second color mark in the PU2 color set precision image, and obtain the measured position coordinates of the second color mark, which are recorded as the second measured color mark position; According to the first measured color mark position and the second measured color mark position, the measured distance between the two color marks is calculated and recorded as the measured color mark distance.

8. The RFID aluminum foil front and back color control method according to claim 7, characterized in that: The step of obtaining the measured position coordinates of the first color mark comprises: Divide the PU1 color image into two parts: the color mark area and the non-color mark area; In the segmented color mark area, the contour features of the first color mark are extracted to obtain the edge pixel set of the first color mark. ; Calculate the geometric center coordinates of the first color mark based on the edge pixel set of the first color mark ; The geometric center coordinates of the first color scale As the center, sub-pixel edge detection is performed in its neighborhood to obtain a high-precision edge coordinate set of the first color scale; Perform ellipse fitting on the high-precision edge coordinate set of the first color mark to obtain the sub-pixel geometric center coordinates of the first color mark ( ), recorded as the first measured color mark position.

9. The RFID aluminum foil front and back color control method according to claim 6, characterized in that: The color registration control according to the measured color mark spacing and the initial color mark spacing includes: The measured color mark spacing is compared with a preset spacing threshold. If the measured color mark spacing is less than or equal to the preset spacing threshold, the initial rotation speed of the second printing plate axis is maintained; if the measured color mark spacing is greater than the preset spacing threshold, the deviation between the measured color mark spacing and the initial color mark spacing is calculated to obtain the color mark spacing deviation; According to the color mark spacing deviation, the adjustment value of the second printing plate shaft rotation speed is calculated; according to the adjustment value of the second printing plate shaft rotation speed, the initial rotation speed of the second printing plate shaft is adjusted to generate the target rotation speed of the second printing plate shaft.

10. An RFID aluminum foil front and back color matching control system, which is used to implement the RFID aluminum foil front and back color matching control method according to any one of claims 1 to 9, characterized in that: The system comprises: Analysis module: used to obtain the first color mark position and the second color mark position of the target printing pattern, and calculate the initial color mark spacing according to the first color mark position and the second color mark position; obtain the circumference of the printing plate and the color group distance, and calculate the first pre-overprint position and the second pre-overprint position according to the circumference of the printing plate and the color group distance; Pre-printing module: performs pre-printing settings according to the first pre-printing position and the second pre-printing position; Real-time detection module: According to the pre-printing settings, the front and back sides of the RFID aluminum foil are overprinted. During the overprinting process, the overprint image of the printing material is obtained, and the measured color mark spacing between the first color mark and the second color mark is obtained according to the overprint image; Color registration control module: performs color registration control based on the measured color mark spacing and the initial color mark spacing.

Images