A printing automatic nest position control system and structure

Abstract

This invention relates to an automatic registration control system and structure for printing, belonging to the technical field of registration equipment. It includes a control module, several camera modules and a transmission module electrically connected to the control module. Each of the camera modules is correspondingly positioned behind a corresponding printhead of the registration device. The transmission module is electrically connected to the control module. The control module instructs the transmission module to move the paper sequentially past and stop below the printheads and cameras. The control module is electrically connected to the printheads and instructs them to spray ink while the paper is stopped. The camera modules are oriented towards the paper, and the cameras are used to photograph the paper and upload the photographed image to the control module. The control module adjusts the dwell time for each photographed image, ensuring both adjustment accuracy and operational efficiency.

Description

Technical Field

[0001] This invention belongs to the technical field of overprinting equipment, specifically relating to an automatic overprinting control system and structure. Background Technology

[0002] In digital printing, colors printed from multiple printheads need to be overlaid together to form a variety of colors and patterns. However, during the printing process, due to random factors such as paper displacement, printhead vibration or displacement, misregistration occurs when colors printed from multiple printheads are overlaid together to form a pattern, which seriously affects the printing effect and reduces the printing quality.

[0003] To address this issue, it's necessary to detect whether the patterns or colors in each layer of the printing press are aligned. A common solution is to install a camera at the very end of the printing press to check print quality. However, this method requires waiting until all colors are printed before detecting alignment, making it impossible to promptly identify and adjust registration errors. To address this, Chinese patent CN207683124U discloses a registration detection device with camera image recognition functionality, belonging to the field of automatic printing control technology. It consists of a camera, a tablet computer, a controller, a switch, and a host computer. The device uses cameras for image acquisition, with one camera at each station after the first station capturing images. The tablet computer calibrates the color mark images to obtain the registration error and sends it to the controller and host computer. The controller calculates the adjustment amount based on the registration error and sends it to the actuator of the printing press to change the position of the printing plate cylinder. The host computer switches the real-time color mark group images of each station via the switch and displays them on the host computer monitor. By setting up cameras and a controller, it automatically detects and executes corrections, shortening registration time and improving registration accuracy. While the above method offers advantages in terms of accuracy, in actual printing, to ensure printing efficiency, the paper needs to pass through each printhead and the space between adjacent printheads as quickly as possible. The camera recognition time between adjacent printheads is short, and overprinting involves printing patterns of various colors. When different colors are formed through overprinting, the color printed by an adjacent printhead is likely to be close to the existing color on the current printing paper. For example, if the current printhead needs to print light blue and the pattern on the current paper is dark blue, the camera is more likely to fail to distinguish the color difference during short-term shooting and recognition. Alternatively, the difference may be more obvious, such as if the current printhead needs to print light blue and the pattern on the current paper is red. In this case, the camera does not need to perform long-term multi-exposure recognition and shooting. However, the above method fails to adjust the recognition time of the camera based on the corresponding printing color of the previous printhead and the current paper. Insufficient recognition accuracy leads to insufficient adjustment accuracy, which in turn cannot guarantee adjustment accuracy or work efficiency. Therefore, a method is needed that ensures adjustment accuracy while also taking into account work efficiency. Summary of the Invention

[0004] To address the aforementioned problems in the existing technology, this invention provides an automatic registration control system and structure for printing, which features both ensuring adjustment accuracy and operational efficiency.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] An automatic registration control system and structure for printing includes a control module, a plurality of camera modules and a transmission module electrically connected to the control module, wherein the plurality of camera modules are configured in one-to-one correspondence with a plurality of printheads of the registration device, and the plurality of camera modules are respectively disposed behind the corresponding printheads.

[0007] The transmission module is electrically connected to the control module. The control module instructs the transmission module to drive the paper to pass through and stop under several printheads and several cameras in sequence. The control module is electrically connected to several printheads and instructs several printheads to spray ink when the paper stops. Several camera modules are set facing the paper. Several cameras are used to take pictures of the paper and upload the captured pattern to the control module.

[0008] The control module is input with colors sprayed by several printheads. The control module is also pre-input with mixed colors formed on the paper after printing by 1, 2...n printheads. The control module numbers the printheads corresponding to several cameras as 1, 2...n. The control module compares the color difference between the colors sprayed by printheads numbered 1, 2...n and the mixed colors formed on the paper after printing by 1, 2...n printheads, and adjusts the time for the transmission module to keep the paper below the cameras behind the 1, 2...n printheads based on the maximum values ​​of several color differences.

[0009] As a preferred embodiment of the present invention, the control module is pre-inputting the mixed colors formed on the paper after printing by 1, 2...n printheads and the colors sprayed by several printheads. Each mixed color is represented by a data group (R11, G11, B11), (R12, G12, B12)...(R1n, G1n, B1n), and each sprayed color is represented by a data group (R21, G21, B21), (R22, G22, B22)...(R2n, G2n, B2n). The control module calculates the color difference data |R11-R21|+|G11-G21|+|B11-B21| and |R12| based on the mixed color and sprayed color data groups, respectively. -R22|+|G12-G22|+|B12-B22|...|R1n-R2n|+|G1n-G2n|+|B1n-B2n|, obtain color difference data C1, C2...Cn, and calculate the dwell time t1, t2...tn of the paper under the camera corresponding to the printhead numbered 1, 2...n based on the color difference data. The control module has a color difference reference value C0 and a dwell time reference value t0 pre-inputted. The control module instructs the transmission module to adjust the dwell time of the paper under the camera corresponding to the printhead numbered 1, 2...n to t1, t2...tn respectively. The relationship between tx and Cx, and between C0 and t0 is as follows:

[0010] tx = Cx / Cx×t0×c, x = 1, 2...n, e is a pre-input constant.

[0011] As a preferred embodiment of the present invention, the control module is electrically connected to a plurality of lighting modules, and the plurality of lighting modules are configured one-to-one with a plurality of camera modules and are used to illuminate the paper.

[0012] As a preferred embodiment of the present invention, any of the lighting modules includes a ring-shaped lighting lamp, which is disposed around the end of the camera module lens.

[0013] As a preferred technical solution of the present invention, the control module is pre-inputting a reference power P0 of the lighting module. The control module calculates the power of the lighting module on the camera of the nozzles numbered 1, 2...n according to the color difference value and instructs each lighting module to operate at a power Px, wherein the relationship between Px and Cx, and between C0 and P0 is as follows:

[0014] Px = C0 / Cx × P0 × d, x = 1, 2...n, and d is a pre-input constant.

[0015] As a preferred embodiment of the present invention, it further includes a control panel, which is electrically connected to the control module and is used to display the shooting results of the camera.

[0016] The present invention also provides an automatic registration structure applicable to the above-mentioned automatic registration control system for printing, including a transmission module and a plurality of printheads. The transmission module includes a transmission roller, which is used to drive the paper to move along the line connecting the transmission rollers. The plurality of printheads are disposed above the transmission roller and facing the transmission roller. Along the transmission direction of the transmission roller, a camera module is disposed behind any of the printheads. The plurality of camera modules, the transmission roller and the printheads are electrically connected to the control module.

[0017] The beneficial effects of this invention are as follows:

[0018] (1) By having the control module compare the colors sprayed by the printheads numbered 1, 2...n with the color difference of the mixed colors formed on the paper after printing by the printheads numbered 1, 2...n, and adjusting the time for the transmission module to keep the paper under the camera behind the printheads according to the color difference, the dwell time is automatically extended when the difference between the new printed pattern and the lower layer pattern is small and the shooting time of the camera module and the judgment time of the control module need to be extended; and the dwell time is automatically reduced when the difference between the new printed pattern and the lower layer pattern is large and no extension of time is required.

[0019] (2) By having the control module adjust the power of the corresponding lighting module according to each color difference data, when the color difference is small and a larger lighting power and better fill light effect are required, the power of the lighting module is increased to ensure the clarity of the camera image and the accuracy of adjustment; when the color difference is large and a larger lighting power and better fill light effect are not required, the power of the lighting module is reduced to reduce additional power consumption. Attached Figure Description

[0020] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0021] Figure 1 This is a schematic diagram of the structure of the present invention;

[0022] Figure 2 This is a block diagram of the control loop of the present invention.

[0023] Explanation of key component symbols:

[0024] In the diagram: 1. Transmission module; 11. Transmission roller; 2. Nozzle; 3. Camera module; 31. Lighting module; 4. Control module; 5. Paper. Detailed Implementation

[0025] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0026] Please see Figure 1-2An automatic registration control system and structure for printing includes a control module 4 and a transmission module 1 electrically connected to the control module 4. Specifically, the transmission module 1 is electrically connected to the control module 4. The control module 4 instructs the transmission module 1 to drive the paper 5 to pass through and stop below a plurality of printheads 2 in sequence. The transmission module 1 includes at least two parallel transmission rollers 11. The two transmission rollers 11 and the control module 4 are connected by an encoder. The electrical signal of the control module 4 is converted by the encoder to form the movement of the transmission rollers 11. The control module 4 controls the paper feeding distance of the transmission module 1 through the encoder. A registration station is formed between the two transmission rollers 11. Specifically, the registration printing system also includes a plurality of printheads 2. The plurality of printheads 2 are arranged above the registration station formed by the transmission module 1 and aligned downwards. The plurality of printheads 2 are arranged in a row along the direction of the line connecting the two transmission rollers 11.

[0027] In use, the two drive rollers 11, under the command of the control module 4 and the encoder, drive the paper 5 on them to move forward and stop alternately in the overprinting station. When the part of the paper 5 to be printed stops below one of the printheads 2, the printhead 2 of the overprinting station prints the part to be printed below. The colored ink sprayed by the printhead 2 forms a color layer on the paper 5. Then the drive module 1 drives the paper 5 and the part of the paper 5 to be printed forward until it is aligned with the next printhead 2. The drive module 1 stops the paper 5. At this time, the part to be printed is aligned with the next printhead 2. The next printhead 2 prints the part to be printed below. The above process is repeated until all printheads 2 have printed the pattern on the part to be printed. Several layers of pattern form an overprinted pattern, and the overprinting is completed.

[0028] In the above process, the transmission module 1, printhead 2, and paper 5 need to work together to ensure that the patterns printed by several printheads 2 are printed sequentially onto the same position on the paper 5. When one of the patterns deviates from the target position, the printing effect will be reduced. Furthermore, there is an error in each process where the encoder converts the electrical signal from the control module 4 into a signal indicating the paper feed length. The closer the printhead 2 is to the rear end and its corresponding printing station along the paper feed direction, the greater the accumulated error in the paper feed distance when the paper 5 reaches that point. For example, experiments have shown that when the total paper feed length is 20-30Cx, the accumulated error of the encoder will cause the error to occur along the paper feed direction. The positional deviation of the pattern printed by the first and last printheads 2 at the printing position reaches 0.06mm. The patterns of each layer that should overlap no longer overlap, resulting in a decrease in printing quality. Therefore, it is necessary to correct the error based on the real-time printing deviation to prevent the error from getting bigger and further reducing the printing quality. For this purpose, several camera modules 3 electrically connected to the control module 4 are also included. The camera modules 3 are set one-to-one with the printheads 2 of the overprinting device. Along the paper feeding direction, each camera module 3 is set behind the corresponding printhead 2. The control module 4 instructs the transmission module 1 to drive the paper 5 to pass through and stop under the printheads 2 and the cameras in sequence.

[0029] For camera module 3, specifically, each camera module 3 includes at least one camera, and each camera is electrically connected to the control module. The camera is aimed at...

[0030] Specifically, when the registration printing equipment has a total of n printheads 2, the control module 4 numbers the corresponding printheads 2 with several cameras as 1, 2...n. For example, taking the paper feeding direction as the reference direction, the camera behind the first printhead 2 in the reference direction is printhead 1, the camera behind the second printhead 2 is printhead 2, and so on.

[0031] In use, after the pattern is printed on the printing module under a certain printhead 2, the transmission module 1 drives the printing part to continue to move forward along the paper feeding direction until it is aligned with the camera corresponding to the printhead 2. The transmission module 1 then stops the paper 5. At this time, the printing part stops below the camera. The control module 4 synchronously instructs the camera to start shooting the printing part below. Then the camera uploads the captured pattern to the control module 4. After receiving the image, the control module 4 synchronously adjusts the electrical signal sent to the encoder.

[0032] For example, when the control module 4 instructs the encoder to move the transmission module 1 to a certain printhead 2, and the encoder's own paper feeding distance deviation reaches 0.03mm, there are two non-overlapping patterns on the paper 5, and the misalignment distance between the two patterns is 0.03mm. The camera captures the pattern and uploads it to the control module 4. The control module 4 analyzes the image to determine the misalignment distance between the two patterns, and instructs the encoder to make corrections based on the misalignment distance. In this case, when the control module 4 instructs the encoder to send a signal to move to the next printhead 2, it also sends an additional 0.03mm movement signal. At this time, the area to be printed can be aligned with the next printhead 2, completing the overprinting correction.

[0033] In the above process, since the printing needs to be completed as quickly as possible, the time that the transmission module 1 carries the paper 5 and stays under the camera needs to be minimized. The clarity of the image acquired by the camera is positively correlated with the shooting time within a certain range. The control module 4 also needs to use the dwell time to analyze the image. If the dwell time is too short, there is a probability that the shooting time and analysis time will be insufficient, which will affect the adjustment accuracy. If the dwell time is too long, it will lead to insufficient work efficiency. For example, if the printhead 2 needs to print light blue and the pattern on the paper is dark blue, the camera module 3 is more likely to fail to distinguish the color difference when shooting and recognizing in a short time. There is a probability that the difference will be obvious. For example, if the printhead 2 needs to print light blue and the pattern on the paper is red, the camera module 3 does not need to perform long-term multi-exposure recognition and shooting.

[0034] Therefore, in order to adjust the dwell time according to the actual situation, the control module 4 is input with a number of colors sprayed by the printhead 2, and the control module 4 is pre-input with the mixed colors formed on the paper 5 after printing by 1, 2...n printheads 2. The control module 4 compares the color difference of the colors sprayed by the printheads 2 numbered 1, 2...n and the mixed colors formed on the paper 5 after printing by 1, 2...n printheads 2, and obtains a number of color difference values. Then, the control module 4 selects the maximum color difference value from the number of color difference values, and adjusts the time for the transmission module 1 to keep the paper 5 under the camera according to the maximum color difference value.

[0035] Specifically, all color data, including mixed colors and printing colors from printhead 2, consists of a set of RGB values, such as (R11, G11, B11), (R12, G12, B12)...(R1n, G1n, B1n). Specifically, the color of the pattern formed on paper 5 after the first printhead 2 is printed is (R11, G11, B11). The color of the pattern formed by the registration and mixing of the first and second printheads 2 on paper 5 is (R12, G12, B12)... and the color of the pattern formed by the registration and mixing of n printheads 2 on paper 5 is (R1n, G1n, B1n). The pattern colors are simulated by the operator using computer software. Simultaneously, the control module 4 is pre-inputted with the RGB values ​​of the paint colors printed by the first to nth printheads 2, such as (R21, G21, B21), (R22, G22, B22)...(R2n, G2n, B2n).

[0036] Subsequently, control module 4 calculates the color difference, obtaining several color difference data C1, C2...Cn. Control module 4 has pre-input a color difference reference value C0 and a dwell time reference value t0. Based on the color difference data, control module 4 calculates the dwell time t1, t2...tn of the paper 5 under the cameras corresponding to printheads 2 numbered 1, 2...n, and instructs transmission module 1 to adjust the dwell time of the paper 5 under the cameras corresponding to printheads 2 numbered 1, 2...n to t1, t2...tn respectively. The relationship between t and Cx, and between C0 and t0, is as follows:

[0037] t = C0 / Cx × t0 × c, e is a pre-input constant, Cx ≥ 1, when the calculation shows Cx < 1, the control module 4 sets Cx = 1;

[0038] In actual use, when a pattern is printed by x printheads 2 and a deviation occurs, the latest printed pattern on the top layer will be misaligned with the pattern on the bottom layer. At this time, part of the latest printed pattern overlaps with the bottom layer pattern, and the color values ​​of the overlapping part are (R1x, G1x, B1x). The color sprayed by the previous printhead 2 is (R2x, G2x, B2x). Since the deviation part of the latest printed pattern does not overlap with the bottom layer pattern and is directly printed on the paper, the color of the deviation part is also (R2x, G2x, B2x). When the control module 4 judges the size of the deviation based on the image uploaded by the camera module 3, it judges the boundary distance between the pattern with color (R1x, G1x, B1x) and the pattern with color (R2x, G2x, B2x) to determine the specific distance of the deviation.

[0039] When the value of |R1x-R2x|+|G1x-G2x|+|B1x-B2x| calculated by control module 4 based on (R2x, G2x, B2x) and (R1x, G1x, B1x) is small, it indicates that the difference between the new printed pattern and the lower layer pattern is small, and the boundary distance is not easy to judge. It is necessary to extend the shooting time of camera module 3 and the judgment time of control module 4. At this time, Cx is relatively small, and tx=Cx / Cx×t0×c is relatively large. Control module 4 adjusts the time when the camera stays after printhead 2 after printhead x after printhead x, so that the color difference between the offset part and the overlapping part is relatively close, the dwell time is extended accordingly, thereby extending the shooting time and judgment time of camera module 3, improving the judgment accuracy, reducing the adjustment inaccuracy caused by inaccurate judgment, and ensuring the adjustment accuracy when the colors are relatively close.

[0040] Conversely, when the value of |R1x-R2x|+|G1x-G2x|+|B1x-B2x| is large, it indicates that the difference between the new printed pattern and the lower layer pattern is large, and the boundary distance is easier to judge. There is no need to extend the shooting time of the camera module 3 and the judgment time of the control module 4. At this time, Cx is large, and tx=Cx / Cx×t0×c is small. After the control module 4 instructs the transmission module 1 to print through the printhead 2 numbered x, when the camera stays at the printhead 2 for the time tx, it completes the task of reducing the dwell time when the color difference between the offset part and the overlapping part is large. This reduces the shooting time and judgment time of the camera module 3, ensuring a certain judgment accuracy while ensuring work efficiency.

[0041] By having the control module 4 compare the colors sprayed by the printheads 2 numbered 1, 2...n with the color difference of the mixed colors formed on the paper 5 after printing by the printheads 1, 2...n, and adjusting the time for the transmission module 1 to hold the paper 5 under the camera behind the printheads 1, 2...n according to the color difference, the control module 4 automatically extends the holding time when the difference between the new printed pattern and the lower layer pattern is small and the shooting time of the camera module 3 needs to be extended, and automatically reduces the holding time when the difference between the new printed pattern and the lower layer pattern is large and no extension of time is needed.

[0042] During the shooting process of the aforementioned camera module 3, sometimes the nozzle 2 and camera module 3 may block the ambient light. In this case, the image clarity of the image captured by camera module 3 is low. To prevent this from happening, the control module 4 is electrically connected to several lighting modules 31. The lighting modules 31 are set one-to-one with the camera modules 3 and are used to illuminate the area captured by the camera. Specifically, to save space and reduce ghosting, each lighting module 31 includes a ring light. The ring light is set around the end of the lens of camera module 3 and is set towards the lens of camera module 3. At this time, the lighting module 31 can illuminate the object being photographed by camera module 3, providing supplementary light for the lighting module 31, improving the clarity of the image, and thus improving the accuracy of the control module 4 in judging based on the image, and improving the adjustment precision.

[0043] During the illumination process of the illumination module 31, excessive illumination power will lead to additional energy consumption, while insufficient illumination power will result in insignificant supplementary lighting effects. When the color difference between the newly printed pattern and the underlying pattern is small, additional supplementary lighting intensity is required to ensure image accuracy. When the color difference is large, a large supplementary lighting intensity is not necessary. Therefore, the cameras of the printheads 2, numbered 1, 2...n, are also numbered 1, 2...n. The control module 4 is pre-input with the reference power P0 of the illumination module 31. The control module 4 calculates the power of the illumination module 31 based on the color difference value and instructs the illumination modules 31 numbered 1, 2...n to operate at power Px. The relationship between P and Cx, and between C0 and P0, is: Px = C0 / Cx × P0 × d, x = 1, 2...n, and d is a pre-input constant.

[0044] When the value of Cx is small, and the colors of the offset and overlapping parts are relatively close, the value of Px = C0 / Cx × P0 × d is large. This allows for an increase in the power of the lighting module 31 when the color difference is small and a greater lighting power and better fill light effect are required, thus ensuring the clarity and adjustment accuracy of the camera image. Conversely, when the value of Cx is large, and the color difference between the offset and overlapping parts is significant, the value of Px = C0 / Cx × P0 × d is low. This allows for a decrease in the power of the lighting module 31 when the color difference is large and a greater lighting power and better fill light effect are not required, thus reducing additional power consumption.

[0045] To facilitate operators in observing the shooting results and judging whether the clarity of the shooting results meets the automatic judgment standard, a control panel is also included. The control panel is electrically connected to the control module 4 and is used to display the shooting results of the camera.

[0046] The present invention also provides an automatic registration structure applicable to the above-mentioned automatic registration control system for printing, including a transmission module 1 and a plurality of printheads 2. The transmission module 1 includes a transmission roller 11, which drives the paper 5 to move along the line of the transmission roller 11. The plurality of printheads 2 are arranged above the transmission roller 11 and facing the transmission roller 11. A camera module 3 is arranged behind any printhead 2 along the transmission direction of the transmission roller 11. The plurality of camera modules 3, the transmission roller 11 and the printheads 2 are electrically connected to the control module 4.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An automatic registration control system for printing, characterized in that: It includes a control module, several camera modules and a transmission module electrically connected to the control module, and the several camera modules are respectively arranged in correspondence with several printheads of the overprinting device, and the several camera modules are respectively arranged behind the corresponding printheads; The transmission module is electrically connected to the control module. The control module instructs the transmission module to drive the paper to pass through and stop below a number of printheads and a number of camera modules in sequence. The control module is electrically connected to the printheads and instructs the printheads to spray ink when the paper stops. The camera modules are set to face the paper and are used to photograph the paper and upload the photographed pattern to the control module. The control module is input with colors sprayed by several printheads. The control module is also pre-input with mixed colors formed on the paper after printing by 1, 2...n printheads. The control module assigns the printheads corresponding to several camera modules to numbers 1, 2...n. The control module compares the color difference between the colors sprayed by printheads numbered 1, 2...n and the mixed colors formed on the paper after printing by 1, 2...n printheads, and adjusts the time for the transmission module to keep the paper below the camera modules behind the 1, 2...n printheads based on the maximum values ​​of several color differences. The control module is pre-inputted with the mixed colors formed on the paper after printing by 1, 2...n printheads and the colors sprayed by several printheads. Each mixed color is represented by a data set (R11, G11, B11), (R12, G12, B12)...(R1n, G1n, B1n), and each sprayed color is represented by a data set (R21, G21, B21), (R22, G22, B22)...(R2n, G2n, B2n). The control module calculates the color difference data |R11-R21|+|G11-G21|+|B11-B21| and |R12-R22|+|G11-B21| based on the mixed color and sprayed color data sets, respectively. 12-G22|+|B12-B22|...|R1n-R2n|+|G1n-G2n|+|B1n-B2n| is used to obtain color difference data C1, C2...Cn. Based on this color difference data, the dwell time t1, t2...tn of the paper under the camera module corresponding to printheads numbered 1, 2...n is calculated. The control module has a pre-input color difference reference value C0 and a dwell time reference value t0. The control module instructs the transmission module to adjust the dwell time of the paper under the camera module corresponding to printheads numbered 1, 2...n to t1, t2...tn, respectively. The relationship between tx and Cx, and between C0 and t0, is as follows: tx = Cx / Cx × t0 × c, x = 1, 2...n, e is a pre-input constant; The control module is electrically connected to several lighting modules, and each of the lighting modules is configured in a one-to-one correspondence with a number of camera modules and is used to illuminate the paper. The control module is pre-input with the reference power P0 of the lighting module. The control module calculates the power of the lighting module on the camera module of the corresponding nozzle numbered 1, 2...n according to the color difference value and instructs each lighting module to operate at power Px. The relationship between Px and Cx, C0 and P0 is as follows: Px = C0 / Cx × P0 × d, x = 1, 2...n, and d is a pre-input constant.

2. The automatic registration control system for printing according to claim 1, characterized in that: Each of the lighting modules includes a ring light, which is disposed around the end of the camera module lens.

3. The automatic registration control system for printing according to claim 1, characterized in that: It also includes a control panel, which is electrically connected to the control module and is used to display the shooting results of the camera module.

4. An automatic registration structure for printing, applicable to the automatic registration control system for printing as described in any one of claims 1 to 3, characterized in that: The device includes a transmission module and several printheads. The transmission module includes a transmission roller, which drives the paper to move along the line connecting the transmission rollers. Several printheads are disposed above the transmission roller and facing the transmission roller. A camera module is disposed behind any one of the printheads along the transmission direction of the transmission roller. Several camera modules, transmission rollers and printheads are electrically connected to a control module.

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