A high dynamic range based printed matter imaging system and detection method

Abstract

The application discloses a kind of based on high dynamic range's printed matter imaging system and detection method, it is related to the technical field of printing imaging, the imaging system includes: image acquisition module, illumination light source, acquisition control module, data processing module and the printed matter to be measured;The printed matter to be measured is placed on the conveying belt of flow line, and moves with the uniform speed straight line of conveying belt;Image acquisition module and illumination light source are set above conveying belt, the acquisition direction of image acquisition module and the illumination direction of illumination light source are directed to the same position of conveying belt;Acquisition control module is simultaneously connected with image acquisition module and illumination light source for controlling the working state of two;Data processing module is connected with image acquisition module for receiving the image that image acquisition module collects to analyze and process, when analysis result considers that the printed matter to be measured exists defect, it is removed on subsequent flow line;Wherein, image acquisition module at least collects two different brightness images.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printed imaging, and in particular to a high dynamic range-based printed imaging system and detection method. BACKGROUND

[0002] The printing industry, such as cigarette packets, social packets and medicine packets, has many product types, and there are many samples, i.e. high light areas with high gray scale and dark tone areas with low gray scale. The current printed imaging system cannot simultaneously accommodate high light areas and dark tone areas with one set of equipment, because it is necessary to ensure that the high light area is not overexposed, and the gray scale value of the dark tone area is too low, so that the defects in the dark tone area are not visible on the image, and only the defects in the high light area and the intermediate tone can be detected, and the defects in the dark tone area cannot be detected and identified, resulting in missed detection of the product. SUMMARY

[0003] The purpose of the present application is to provide a high dynamic range-based printed imaging system and detection method.

[0004] The technical solution of the present application is to provide a high dynamic range-based printed imaging system, which is built on a flow line for printed quality detection. The imaging system comprises an image acquisition module, an illumination light source, an acquisition control module, a data processing module and a printed product to be tested.

[0005] The printed product to be tested is placed on the conveyor belt of the flow line and moves at a constant speed in a straight line with the conveyor belt. The image acquisition module and the illumination light source are arranged above the conveyor belt, and the acquisition direction of the image acquisition module and the illumination direction of the illumination light source are directed to the same position of the conveyor belt. The acquisition control module is connected to the image acquisition module and the illumination light source for controlling the working states of the two. The data processing module is connected to the image acquisition module for receiving and analyzing the images acquired by the image acquisition module. When the analysis result shows that the printed product to be tested has defects, it will be removed from the subsequent flow line.

[0006] The image acquisition module acquires at least two images with different brightness.

[0007] In any of the above technical solutions, further, the image acquisition module is a multi-channel camera sensor, the multi-channel camera sensor has a plurality of imaging channels, each imaging channel has a different exposure time, and can acquire a plurality of images with different exposure times in a very short time, and the images with different exposure times have different brightness; the illumination light source is a stable light source.

[0008] In any of the technical solutions above, further, the image acquisition module is a single-channel camera sensor; the illumination light source is a stroboscopic light source with m different brightness stroboscopes, and the illumination light source is switched by time sequence control to switch the stroboscopes in sequence at the same time interval, m times in a period, and the acquisition interval of the image acquisition module is consistent with the stroboscopic interval of the illumination light source.

[0009] In any of the technical solutions above, further, the data processing module is constructed with an underexposure mapping model and an overexposure mapping model for calculating the optimal parameters of the image acquisition module and the illumination light source when different brightness images are acquired.

[0010] Also proposed is a detection method applied to the high dynamic range-based printed matter imaging system of any of the technical solutions above, which comprises:

[0011] S1, a standard sample identical to the pattern of the printed matter to be detected moves at a constant speed with the conveying belt, and the image acquisition module captures at least two images with different brightness at the same time under the illumination assistance of the illumination light source, and the obtained images are classified into a template image set, and each image has a label of exposure;

[0012] S2, the printed matter to be detected moves at a constant speed with the conveying belt, and the image acquisition module captures at least two images with different exposure according to the same parameters as in step S1 under the illumination assistance of the illumination light source at the same time, and the images obtained in this step are classified into a to-be-detected image set, and each image has a label of exposure;

[0013] S3, the data processing module picks out the images with the same exposure from the template image set and the to-be-detected image set, aligns all pixel points one by one to calculate the absolute value of the gray difference, generates a differential image of this exposure, and classifies it into a differential image set;

[0014] S4, the normal exposure region is divided in the to-be-detected image, a preset overexposure threshold I high and a low exposure threshold I low are set, the pixels with the gray value between the overexposure threshold I high and the low exposure threshold I low are classified as the normal exposure region, and the obtained normal exposure region is synchronized to the differential image corresponding to the to-be-detected image;

[0015] S5, the pixels with the gray value higher than a preset fault tolerance threshold I wrong are searched in the normal exposure region of the differential image, and if there are, it is judged that the to-be-detected image corresponding to the differential image has defects, and the printed matter to be detected corresponding to the to-be-detected image is rejected.

[0016] In any of the technical solutions above, further, the method further comprises:

[0017] The underexposure mapping model and the overexposure mapping model are constructed to quickly calculate the optimal time parameter of different brightness images at the time of acquisition, and the time parameter is represented by t;

[0018] The preset time parameter is t0, and the image of the to-be-inspected printed matter is acquired in this state. After the flat field correction and the white balance are performed on the image, the gray scale card is acquired. It is assumed that the image has i gray scales in total, and the gray scale values of each gray scale gradually decrease;

[0019] The image is acquired multiple times, and the time parameter of each image acquisition is increased by 1 us as a step until the time parameter reaches t j when the time parameter is increased by j us; j The gray scale value of the i-th gray scale when the time parameter is t i is I j (t low ), and the data points of the gray scale values of each time are obtained to form the following sequence:

[0020]

[0021] According to the above sequence, a mapping model of the gray scale value of each time and the time parameter is established:

[0022]

[0023] The above formula is arranged in the following form:

[0024]

[0025] According to the data points of the sequence, the values of k1, k2…k i are obtained by using the least square method fitting, and at this time, t and I i (t) in the above formula are known quantities;

[0026] I i (t) is assigned to I low , that is, After the data is substituted, the time parameter t is obtained, and the image acquired under this parameter is a lower brightness image. The gray scale values of most pixels of the image can be greater than the low exposure threshold I low , so that the image has a larger area of normal exposure region;

[0027] I1(t) is assigned to I high , that is, After the data is substituted, the time parameter t is obtained, and the image acquired under this parameter is a higher brightness image. The gray scale values of most pixels of the image can be less than the overexposure threshold I high , so that the image has a larger area of normal exposure region.

[0028] In any of the technical solutions above, further, the image acquisition module is a multi-channel camera sensor, the illumination light source is a stable light source, the time parameter is the exposure time of a single channel of the image acquisition module, and the method for the image acquisition module to acquire images of different brightness includes:

[0029] The odd channels of the image acquisition module are set to low exposure, and the even channels are set to high exposure, all the lines acquired by the odd channels are extracted to form a low exposure image, all the lines acquired by the even channels are extracted to form a high exposure image, and the acquisition of the image is completed.

[0030] In any of the technical solutions above, further, the image acquisition module is a single-channel camera sensor, the illumination light source is a frequency flash light source, the frequency flash is performed in a cycle, the frequency flash is performed m times in a cycle, the acquisition interval of the image acquisition module is consistent with the frequency flash interval of the illumination light source, the time parameter is the frequency flash interval time of the illumination light source, and the method for the image acquisition module to acquire images of different brightness includes:

[0031] The image acquisition module sequentially acquires a line of the object to be measured each time, a plurality of groups of lines are extracted at intervals of m, each group of lines is acquired at the same frequency flash intensity, and each group of lines is formed into an image.

[0032] The present application has the following advantages:

[0033] The technical solution in the present application is based on a high dynamic range imaging system, at least two original images of high and low exposure at the same shooting time can be acquired at one time, a high-brightness image is overexposed in a highlight area and is improved to a normal exposure gray value in a dark tone area, defects in the dark tone area are obviously visible, and the dark tone area detection rate is improved; a low-brightness image is not overexposed in a highlight area, and the highlight area is at a normal exposure gray value, and defects in the highlight area and intermediate tone can be detected. BRIEF DESCRIPTION OF DRAWINGS

[0034] The advantages of the above and additional aspects of the present application will become apparent and easily understood in conjunction with the following drawings, in which:

[0035] Figure 1 is a general schematic diagram of a high dynamic range-based printed matter imaging system according to an embodiment of the present application;

[0036] Figure 2 is a schematic diagram of a high dynamic range-based printed matter imaging system according to an embodiment of the present application, in which a multi-channel camera sensor is used as an image acquisition module;

[0037] Figure 3 is a schematic diagram of a high dynamic range-based printed matter imaging system according to an embodiment of the present application, in which a single-channel camera sensor is used as an image acquisition module;

[0038] Figure 4 This is a schematic diagram of a template set, a set of images to be inspected, and a differential set of images based on a high dynamic range printing inspection method according to an embodiment of the present invention.

[0039] Figure 5 This is a schematic flowchart of a high dynamic range-based printed matter inspection method according to an embodiment of the present invention; Figure 6 The images are from actual cases acquired by a high dynamic range printing imaging system and detection method according to an embodiment of the present invention.

[0040] Figure 7 This is a real-world example of a printing imaging system and detection method based on a high dynamic range according to an embodiment of the present invention, which is a local difference image obtained by subtracting a template image from the actual image.

[0041] Figure 8 It is a high dynamic range image generated using existing technology. Detailed Implementation

[0042] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0043] In the following description, many specific details are set forth in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0044] Example 1:

[0045] like Figure 1 As shown, this embodiment provides a high dynamic range-based printing imaging system. The imaging system is built on a production line for printing quality inspection. The imaging system analyzes images of the same printed material at different exposure times. The imaging system includes: an image acquisition module 1, an illumination source 2, an acquisition control module 3, a data processing module 4, and the printed material to be tested 5.

[0046] The printed material 5 to be tested is placed on the conveyor belt of the production line and moves at a constant speed with the conveyor belt; the image acquisition module 1 and the illumination source 2 are set above the conveyor belt, and the acquisition direction of the image acquisition module 1 and the illumination direction of the illumination source 2 are facing the same point of the conveyor belt; the acquisition control module 3 is connected to both the image acquisition module 1 and the illumination source 2 to control their working status; the data processing module 4 is connected to the image acquisition module 1 to receive the images acquired by the image acquisition module 1 and perform analysis and processing.

[0047] In this embodiment, the image acquisition module 1 is a multi-channel camera sensor. The multi-channel camera sensor has multiple imaging channels, each with a different exposure time, which can acquire multiple images with different exposures in a very short time; the illumination source 2 is a stable light source.

[0048] Specifically, such as Figure 2 As shown, the direction of motion of the printed matter 5 to be tested is perpendicular to the acquisition direction of the image acquisition module 1. The image acquisition module 1 has n channels, where n is an even number. Since the object to be acquired is moving at a constant speed, each channel A1 to A... n In a single acquisition, the channel will simultaneously acquire data from B1 to B5 of the printed material under test. nn One of the lines; the sampling interval between adjacent channels is one pixel. In the first sampling, channel A1 samples B1, A2 samples B2, and so on, channel A... n Collect B n The same acquisition from different channels occurs at the same time; in the second acquisition, channel A1 acquires data from channel B. n+1 A2 collects B n+2 A n Collect B 2n This process continues until the object to be acquired leaves the acquisition range of image acquisition module 1; that is, channel A1 will sequentially acquire B1, B2, and B3. n+1 B 2n+1 ..., Channel A n B will be collected sequentially n B 2n B 3n ...

[0049] Odd-numbered channels are set to low exposure, and even-numbered channels are set to high exposure. Lines from all odd-numbered channels are extracted and combined into a low-exposure image, and lines from all even-numbered channels are extracted and combined into a high-exposure image, thus completing the image acquisition.

[0050] Example 2:

[0051] In this embodiment, the image acquisition module 1 is a single-channel camera sensor, and the illumination source 2 is a strobe light source with m different brightness strobes. Through timing control, the illumination source 2 continuously switches strobes in sequence at the same time interval, switching m times in one cycle. The acquisition interval of the image acquisition module 1 is consistent with the strobe interval of the illumination source 2.

[0052] Specifically, such as Figure 3 As shown, after the printed matter 5 under test moves to below the image acquisition module 1, in the first cycle, the image acquisition module 1 acquires images from C1 to C2 of the printed matter 5 under test. m There are m lines in total. In the second cycle, image acquisition module 1 acquires the C of the printed material 5 under test. m+1To C 2m There are m lines in total, and so on until the printed material 5 under test leaves the acquisition range of the image acquisition module 1. Multiple sets of lines are extracted at intervals of m, such as C1, C2, C3, C4, C5, C6, C7, C8, C9 ... m+1 C 2m+1 ..., C m C 2m C 3m ... Each group of lines is combined into a single image, and multiple acquired images under different brightness levels are input into data processing module 4 for analysis and processing.

[0053] Example 3:

[0054] like Figure 4 and Figure 5 As shown, this embodiment provides a printing imaging detection method applied to the high dynamic range printing imaging system provided in Embodiment 1 or 2. The method includes:

[0055] S1. A standard sample with the same pattern as the printed matter 5 to be tested moves at a constant speed along the conveyor belt. The image acquisition module 1 takes at least two images with different exposures at the same time under the illumination of the illumination source 2. The obtained images are included in the template image set, and each image has an exposure label.

[0056] S2. The printed material 5 to be tested moves at a constant speed with the conveyor belt. The image acquisition module 1 takes at least two images with different brightness at the same time under the illumination assistance of the illumination source 2, according to the same parameters as in step S1. The images obtained in this step are included in the image set to be tested, and each image has an exposure label.

[0057] S3, Data Processing Module 4 selects images with the same exposure from the template image set and the image set to be tested, aligns all pixels one by one to calculate the grayscale difference, generates a difference image with this exposure and incorporates it into the difference image set.

[0058] The gray level of each pixel in the difference image is the absolute value of the difference between the gray levels of corresponding pixels in the template image and the image to be tested.

[0059] S4. Divide the normally exposed area in the image to be inspected, and preset the overexposure threshold I. high and low exposure threshold I low The grayscale value is between the overexposure threshold I. high and low exposure threshold I low The pixels between them are designated as normal exposure areas, and the obtained normal exposure areas are synchronized to the differential image corresponding to the image to be inspected.

[0060] S5. Within the normal exposure area of ​​the differential image, find the grayscale value that is higher than the preset tolerance threshold I. wrongIf the difference between the pixel value of the pixel in the normal exposure area of the difference image and the pixel value of the pixel in the normal exposure area of the reference image is greater than the fault tolerance threshold I, it is determined that the test image corresponding to the difference image has a defect, and the test printed matter corresponding to the test image is rejected.

[0061] Fault tolerance threshold I wrong It can be 0, indicating that all pixels with a gray scale other than 0 in the normal exposure area of the difference image are defects; according to the requirements of production operation on the printing quality of printed matter, the fault tolerance threshold I can be appropriately increased wrong .

[0062] Example Four:

[0063] The underexposure mapping model and the overexposure mapping model are constructed to quickly calculate the optimal time parameter of different brightness images at the time of acquisition, and the time parameter is represented by t. The time parameter is the exposure time of the single channel of the image acquisition module 1 in Example One, and the flash interval time of the illumination light source 2 in Example Two.

[0064] Specifically, the preset time parameter is t0, and the image of the test printed matter is acquired in this state. After the image is subjected to flat field correction and white balance, a gray scale card is acquired. It is assumed that the image has a total of i gray scales, and the gray scale value of each gray scale decreases gradually. The image is acquired multiple times, and the time parameter of each image acquisition is increased by 1us as a step until the time parameter reaches t j when the gray scale value of the i-th gray scale is increased by jus j (t i (t j )>I low , the data points of the gray scale values of each time are obtained, and the following sequence is formed:

[0065]

[0066] According to the above sequence, a mapping model of the gray scale value of each time and the time parameter is established:

[0067]

[0068] It is arranged in the following form:

[0069]

[0070] According to the data points of the sequence, the values of k1, k2…k i are obtained by least squares fitting. At this time, t and I i (t) in the above formula are known quantities.

[0071] I i (t) is assigned to I low , that is After substituting the data, the time parameter t is obtained, and the image collected at the parameter is a lower brightness image, and the gray value of most pixels of the image can be greater than the low exposure threshold I low , so that the image has a larger area of normal exposure region.

[0072] I1(t) is assigned to I high , that is After substituting the data, the time parameter t is obtained, and the image collected at the parameter is a higher brightness image, and the gray value of most pixels of the image can be less than the overexposure threshold I high , so that the image has a larger area of normal exposure region.

[0073] According to the above mapping model, the time parameter for image acquisition is set, the influence of the reflection of the surface of the to-be-tested printed matter can be eliminated as much as possible, so that the present application can be used for the detection of conventional paper printed matters, and can also be used for the detection of printed matters made of certain reflective materials such as laser cards, gold and silver cards, and copper plate paper.

[0074] Embodiment five:

[0075] In the previous embodiments, the to-be-tested printed matter 5 prints a black and white pattern, and the image acquired by the image acquisition module 1 is a black and white image, and the normal exposure region is determined according to the gray value of each pixel of the image.

[0076] In this embodiment, the to-be-tested printed matter 5 prints a color pattern, and the image acquisition module 1 acquires a color image, specifically, the acquired color image is an RGB image, and after the acquisition, the RBG color image is converted to the HSV color space, and the brightness V is converted into a gray value for dividing the normal exposure region and guiding the mapping model of embodiment four to set a reasonable time parameter.

[0077] The values of the three parameters R (red), G (green), and B (blue) of the RBG color space are all 0 to 255, and among the three parameters of the HSV color space, the hue H takes a value of 0° to 360°, and the saturation S and the brightness V take a value of 0% to 100%; the formula for converting the parameters of the RGB color space image into the parameters of the HSV color space is as follows:

[0078] R'=R / 255; G'=G / 255; B'=B / 255;

[0079] C max =max(R', G', B');

[0080] C min =min(R', G', B');

[0081] Δ=C max -C min ;

[0082]

[0083]

[0084] V=C max .

[0085] Example six:

[0086] This embodiment provides a part of the measured image to prove the detection effect of the present application.

[0087] As Figure 6 shown, the multi-channel camera cooperates with the constant light source to collect the measured printed matter, and obtains a high-brightness image (left) and a low-brightness image (right), the defects in the box are concave-convex deviation, the defects in the circle are dirt, the concave-convex deviation in the box is obviously visible in the low-brightness image, and is invisible in the high-brightness image due to overexposure; the dirt defects in the circle are obviously visible in the high-brightness image, and are invisible in the low-brightness image due to too dark, the data processing system 4 realizes the detection of the dirt in the dark area and the concave-convex deviation in the highlight area through the processing and analysis of the high-brightness and low-brightness images, and has high application value.

[0088] As Figure 7 shown, the multi-channel camera cooperates with the constant light source to collect the measured printed matter, and obtains a high-brightness image (left) and a low-brightness image (right), the defects in the box are concave-convex deviation, the defects in the circle are dirt, the concave-convex deviation in the box is obviously visible in the low-brightness image, and is invisible in the high-brightness image due to overexposure; the dirt defects in the circle are obviously visible in the high-brightness image, and are invisible in the low-brightness image due to too dark, the data processing system 4 realizes the detection of the dirt in the dark area and the concave-convex deviation in the highlight area through the processing and analysis of the high-brightness and low-brightness images, and has high application value.

[0089] As Figure 8 shown, the prior art usually adopts the method of shooting images under different exposure degrees, and generates a high dynamic range (HDR) image by fusing these images, due to the limitation of detection cost, the precision of generating the high dynamic range image is insufficient, and the image in the figure is a high dynamic range image, due to the distortion problem of the transition zone in the fusion process, the defect detection appears the situation of missing report or false report, and the detection effect is poor.

[0090] In summary, the present application provides a printed matter imaging system and a detection method based on high dynamic range, wherein the imaging system comprises an image collection module 1, an illumination light source 2, a collection control module 3, a data processing module 4 and a measured printed matter 5.

[0091] The to-be-tested printed matter 5 is placed on the conveying belt of the flow line and moves at a constant speed in a straight line along the conveying belt; the image acquisition module 1 and the illuminating light source 2 are arranged above the conveying belt, the acquisition direction of the image acquisition module 1 and the illuminating direction of the illuminating light source 2 are directed to the same position of the conveying belt; the acquisition control module 3 is connected with the image acquisition module 1 and the illuminating light source 2 simultaneously for controlling the working states of the two; the data processing module 4 is connected with the image acquisition module 1 for receiving the images acquired by the image acquisition module 1 to analyze and process, when the analysis result considers that the to-be-tested printed matter 5 has defects, the to-be-tested printed matter 5 is removed in the subsequent flow line; the image acquisition module 1 acquires at least two images with different brightness.

[0092] The detection method comprises:

[0093] S1, the standard sample with the same pattern as the to-be-tested printed matter 5 moves at a constant speed along the conveying belt, the image acquisition module 1 shoots at least two images with different brightness at the same time under the illumination assistance of the illuminating light source 2, the obtained images are classified into a template image set, and each image has a label of exposure.

[0094] S2, the to-be-tested printed matter 5 moves at a constant speed along the conveying belt, the image acquisition module 1 shoots at least two images with different exposure according to the same parameters as step S1 under the illumination assistance of the illuminating light source 2 at the same time, the images obtained in this step are classified into a to-be-tested image set, and each image has a label of exposure.

[0095] S3, the data processing module 4 picks out the images with the same exposure from the template image set and the to-be-tested image set, aligns all pixel points one by one to make a gray scale difference, generates a differential image of this exposure and classifies it into a differential image set.

[0096] S4, the normal exposure area is divided in the to-be-tested image, the preset overexposure threshold I high and the low exposure threshold I low , the pixels with the gray scale value between the overexposure threshold I high and the low exposure threshold I low are classified as the normal exposure area, and the obtained normal exposure area is synchronized to the differential image corresponding to the to-be-tested image.

[0097] S5, whether the to-be-tested image corresponding to the differential image has defects is found according to the preset defect threshold I wrong in the normal exposure area of the differential image, if yes, the to-be-tested printed matter corresponding to the to-be-tested image is removed.

[0098] The steps in the application can be adjusted, combined and deleted in sequence according to actual needs.

[0099] The units in the device of the application can be combined, divided and deleted according to actual needs.

[0100] While the application has been disclosed with reference to the preferred embodiments thereof, it is to be understood that the application is not limited to the particulars disclosed and that various modifications and changes can be made in the application without departing from the spirit and scope thereof.

Claims

1. A detection method based on a high dynamic range printing imaging system, characterized in that, The imaging system includes: an image acquisition module (1), an illumination source (2), an acquisition control module (3), a data processing module (4), and a printed matter to be tested (5); The detection method includes: S1. A standard sample with the same pattern as the printed matter (5) to be tested moves at a constant speed along the conveyor belt. The image acquisition module (1) takes at least two images with different brightness at the same time under the illumination assistance of the illumination source (2). The obtained images are assigned to the template image set, and each image has an exposure label. S2. The printed matter to be tested (5) moves at a constant speed with the conveyor belt. The image acquisition module (1) takes at least two images with different exposures at the same time under the illumination assistance of the illumination source (2) according to the same parameters as in step S1. The images obtained in this step are included in the image set to be tested. Each image has an exposure label. S3, Data processing module (4) picks out images with the same exposure in the template image set and the image set to be tested, aligns all pixels one by one to calculate the absolute value of the gray level difference, generates the differential image of this exposure and merges it into the differential image set. S4. Divide the image to be inspected into normally exposed areas and preset the overexposure threshold. and low exposure threshold The grayscale value is between the overexposure threshold. and low exposure threshold The pixels between them are designated as normal exposure areas, and the obtained normal exposure areas are synchronized to the differential image corresponding to the image to be inspected. S5. Within the normal exposure area of ​​the differential image, find the grayscale value that is higher than the preset tolerance threshold. If a pixel exists, it is determined that the image to be inspected corresponding to the difference image has a defect, and the printed matter to be tested corresponding to the image to be inspected is rejected. The method further includes: Underexposure mapping model and overexposure mapping model are constructed to quickly calculate the optimal time parameter for images of different brightness at the time of acquisition. The time parameter is represented by t. The preset time parameter is In this state, an image of the printed matter to be inspected is acquired. After flat field correction and white balance are performed on the image, a grayscale color chart is acquired. Suppose that the image has a total of i gray levels, and the gray value of each gray level gradually decreases. Multiple images were acquired, with the time parameter for each acquisition increasing in increments of 1 μs, until it reached a certain value. j μs makes the time parameter reach The time parameter is grayscale value of the i-th gray level The data points of grayscale values ​​at each time point are obtained, forming the following sequence: ； Based on the above sequence, establish a mapping model between grayscale values ​​and time parameters at each time step: ； Organize it into the following format: ； Based on the data points of the sequence, the least squares method is used to fit the data. The value of the expression is then divided by the given expression. and All external quantities are known. Will Assigned value ,Right now After substituting the data, the time parameter t is obtained. The image acquired under this parameter is a low-brightness image, in which the grayscale value of most pixels is greater than the low-exposure threshold. This allows the image to have a larger area of ​​normal exposure. Will Assigned value ,Right now After substituting the data, the time parameter t is obtained. The image acquired under this parameter is a high-brightness image, and the grayscale value of most pixels in this image is less than the overexposure threshold. This allows the image to have a larger area of ​​normal exposure.

2. The detection method of the printed matter imaging system based on high dynamic range as described in claim 1, characterized in that, The image acquisition module (1) is a multi-channel camera sensor, the illumination source (2) is a stable light source, the time parameter is the exposure time of a single channel of the image acquisition module (1), and the method of the image acquisition module (1) acquiring images of different brightness includes: Set the odd-numbered channels of the image acquisition module (1) to low exposure and the even-numbered channels to high exposure. Extract the lines from all odd-numbered channels to form a low-exposure image and extract the lines from all even-numbered channels to form a high-exposure image, thus completing the image acquisition.

3. The detection method of the printed matter imaging system based on high dynamic range as described in claim 1, characterized in that, The image acquisition module (1) is a single-channel camera sensor, and the illumination source (2) is a strobe light source that flashes periodically, with m flashes per period. The acquisition interval of the image acquisition module (1) is consistent with the strobe interval of the illumination source (2), and the time parameter is the strobe interval time of the illumination source (2). The method for the image acquisition module (1) to acquire images of different brightness includes: The image acquisition module (1) acquires one line of the object to be tested in sequence each time, extracts multiple sets of lines at intervals of m, and each set of lines is acquired under the same stroboscopic intensity, and each set of lines is combined into an image.

Images