A nozzle clogging detection device and method for a printhead, printing apparatus

Abstract

The application relates to the technical field of printhead nozzle state detection, in particular to a nozzle blockage detection device and method of a printhead and a printing device. The device comprises: an infrared laser generation unit for generating parallel infrared lasers on a nozzle array extension line; a light spot detection unit for detecting a light spot signal formed by the infrared lasers; a translation mechanism for driving the infrared laser generation unit and the light spot detection unit to translate along the nozzle array arrangement direction, so that the infrared laser path is adapted to the target nozzle array; a blockage detection unit for controlling the infrared laser generation unit and the light spot detection unit to move, so that the infrared laser path is located on a plane determined by the array extension direction of the target nozzle array and a direction perpendicular to the array extension direction on the ejection side, and in the case that the infrared laser is emitted and an ejection instruction is sent to a specified nozzle, a first light spot signal is acquired, and the working state of the specified nozzle is detected according to the first light spot signal.

Description

Technical Field

[0001] This application relates to the field of printhead nozzle status detection technology, and in particular to a printhead nozzle clogging detection device, a printing device, and a method for detecting nozzle clogging in a printing device. Background Technology

[0002] In inkjet printers, the printhead, as the core ejection component, typically comprises multiple nozzle arrays. Each nozzle array has numerous tiny nozzles arranged sequentially along its extension direction. Each nozzle ejects ink droplets under the control of a drive signal to achieve precise image or text output. When any nozzle becomes clogged, partially clogged, or experiences ejection abnormalities, defects such as broken lines, imperfections, or abnormal color gradation will appear in the printed result, directly affecting print quality. Therefore, accurate and timely detection of the working status of each nozzle in the printhead is a crucial technical issue for ensuring print quality and stable equipment operation.

[0003] Currently, the main methods for detecting nozzle clogging include the following conventional methods:

[0004] The first method is the test page printing method. Users print specific test patterns or calibration diagrams and then visually inspect the printouts for broken lines or missing ink to determine if the nozzles are clogged. This method is simple to operate, but it heavily relies on subjective human judgment, has limited accuracy, and cannot be automated or used for online testing. Therefore, it is not suitable for applications requiring real-time monitoring of equipment operating status.

[0005] The second method is optical detection. This method uses a camera or high-speed imaging device to capture the trajectory, shape, or volume changes of ink droplets during their flight in the air, thereby determining whether the nozzle is ejecting ink normally. Although this method has high accuracy in experimental environments, it typically requires a complex optical imaging system, a high-speed image acquisition module, and corresponding image processing algorithms. The system structure is complex and costly, and it has strict requirements for installation space and ambient light conditions, making it difficult to promote and apply in ordinary consumer-grade printing devices.

[0006] The third method is piezoelectric signal analysis. For piezoelectric printheads, changes in the electrical signal characteristics driving the piezoelectric element can be analyzed to indirectly infer whether the nozzle is clogged or has ejection abnormalities. However, this method is susceptible to individual circuit differences, temperature variations, and electromagnetic interference, resulting in insufficient stability of the detection results. Furthermore, this method is not applicable to thermal inkjet printheads, lacks versatility across different printhead structures, and has limitations in overall reliability.

[0007] In summary, existing nozzle clogging detection solutions either rely on manual judgment and have low automation, or have complex structures and high costs, or have limited applicability and insufficient reliability, making it difficult to balance the requirements of cost, structural simplification, detection accuracy and automation. Summary of the Invention

[0008] (a) Technical problems to be solved

[0009] In view of the above-mentioned shortcomings and deficiencies of the prior art, this application provides a nozzle clogging detection device and method for printheads, and a printing device, which solves the technical problems of existing nozzle clogging detection schemes relying on manual judgment, having low automation, or having complex detection structures and high costs.

[0010] (II) Technical Solution

[0011] To achieve the above objectives, the main technical solutions adopted in this application include:

[0012] In a first aspect, embodiments of this application provide a nozzle clogging detection device for a printhead, characterized in that it includes:

[0013] An infrared laser generating unit is used to generate a parallel infrared laser beam along the extension line of the nozzle array in the printhead.

[0014] A spot detection unit is used to detect the spot signal formed by the infrared laser on a detection plane that is aligned with the normal direction of the target nozzle array.

[0015] A translation mechanism is used to drive the infrared laser generating unit and the spot detection unit to translate synchronously along the nozzle array arrangement direction so that the infrared laser path is adapted to the target nozzle array.

[0016] A clogging detection unit is electrically connected to the printhead, the infrared laser generating unit, the spot detection unit, and the translation mechanism. The clogging detection unit controls the movement of the infrared laser generating unit and the spot detection unit through the translation mechanism, so that the infrared laser path is located on a plane jointly determined by the array extension direction of the target nozzle array and the direction perpendicular to the array extension direction on the spray side, and the infrared laser path is parallel to the array extension direction. When the infrared laser generating unit emits infrared laser and issues a spray command to a designated nozzle in the target nozzle array, the spot detection unit acquires a first spot signal and detects the working state of the designated nozzle based on the first spot signal, wherein the first spot signal is obtained at a preset time interval after the spray command is issued.

[0017] Optionally, in some embodiments of this application, the preset time interval includes the jetting delay from when the printhead receives the jetting command to when the ink droplet is ejected, and the flight time required for the ink droplet to move to the center of the infrared laser path after being ejected from the nozzle.

[0018] Optionally, in some embodiments of this application, the infrared laser generated by the infrared laser generating unit has a wavelength range of 750nm to 3000nm, the cross-section of the infrared laser is circular or rectangular, and the diameter of the spot image formed by the infrared laser on the detection plane is larger than the maximum diameter of the ink droplet ejected by the nozzle.

[0019] Optionally, in some embodiments of this application, the blockage detection unit is further configured to determine the light spot signal intensity difference between the first light spot signal and the pre-acquired second light spot signal, and compare the light spot signal intensity difference with a preset threshold, wherein:

[0020] If the difference in light spot signal intensity is greater than the preset threshold, it is determined that an ink droplet has passed through the infrared laser path, so as to determine that the designated nozzle is in normal inkjet state;

[0021] If the difference in light spot signal intensity is less than or equal to the preset threshold, the designated nozzle is determined to be in a blocked state.

[0022] The second spot signal is the spot signal formed on the detection plane by the infrared laser when no ink droplet passes through the infrared laser path.

[0023] Optionally, in some embodiments of this application, the blockage detection unit is further configured to acquire a corresponding spot image based on the first spot signal, and determine whether a dark spot appears in the spot image of the first spot signal. If no dark spot appears, the specified nozzle is determined to be in a blocked state. The dark spot is a local light intensity reduction area in the spot image caused by the ink droplet passing through the infrared laser path.

[0024] Optionally, in some embodiments of this application, the blockage detection unit is further configured to, when a dark spot appears in the spot image of the first spot signal, determine whether the designated nozzle has a spray direction deviation based on the position of the dark spot in the spot image and a preset effective detection area of ​​the spot image. The line connecting the projection point of the designated nozzle position on the detection plane and the center position of the spot image formed by the infrared laser on the detection plane is used as a reference axis. Two boundary rays extending from both sides of the reference axis, with an angle not greater than a preset spray deviation angle, are respectively extended from the reference axis. The effective detection area is the intersection of the area surrounded by the boundary rays and the projection area of ​​the spot image on the detection plane.

[0025] Optionally, in some embodiments of this application, the blockage detection unit is further configured to, when a dark spot appears in the spot image of the first spot signal, extract image features from the spot image and input the extracted image features into a pre-trained image recognition model to determine the direction and angle of ink droplet ejection, compare the ejection angle with a preset angle tolerance range, and determine that the specified nozzle has an ejection direction offset when the ejection angle exceeds the preset angle tolerance range; wherein, the image features include the center position coordinates, area parameters, and local grayscale decrease magnitude of the dark spot, the local grayscale decrease magnitude being the difference between the average pixel grayscale value of the dark spot and the average pixel grayscale value of the spot area other than the dark spot in the spot image, and the image recognition model is configured to output a value corresponding to the ink droplet ejection angle based on the image features in the spot image;

[0026] When the image recognition model is pre-trained using training data, the training data includes image features of light spot images collected under different known spray angle conditions and corresponding ink droplet spray angle annotation information.

[0027] Optionally, in some embodiments of this application, the clogging detection unit is further configured to, when a dark spot appears in the light spot image of the first light spot signal, acquire the dark spot features of the light spot image, and determine whether the ink droplet corresponding to the dark spot is rotating based on the dark spot features;

[0028] The dark spot features of the light spot image include: the roundness of the dark spot outline, the aspect ratio, the smoothness of the dark spot edge, and the skewness of the edge curve.

[0029] The degree of skewing of the edge curve of the dark spot is obtained in the following way:

[0030] Based on the coordinates of the edge curve of the dark spot extracted from the spot image, the edge curve is fitted, and the angle between the edge curve and the reference axis from the nozzle position to the center of the spot image is calculated. The angle is then used as a quantitative value of the skewness of the edge curve.

[0031] Secondly, embodiments of this application also provide a printing device, including:

[0032] Print head;

[0033] The nozzle clogging detection device for the printhead as described in the first aspect.

[0034] Thirdly, embodiments of this application also provide a method for detecting nozzle clogging in a printing device, comprising the following steps:

[0035] The infrared laser generating unit and the spot detection unit are driven to translate along the nozzle array arrangement direction so that the infrared laser path is adapted to the target nozzle array.

[0036] The infrared laser generating unit is controlled to emit infrared laser, such that the infrared laser path is located on a plane jointly determined by the array extension direction of the target nozzle array and the direction perpendicular to the array extension direction on the spray side, and the infrared laser path is parallel to the array extension direction.

[0037] A spray command is issued to a designated nozzle in the target nozzle array;

[0038] The first spot signal is obtained by the spot detection unit, and the first spot signal is obtained at a preset time interval after the spray command is issued;

[0039] The working status of the designated nozzle is detected based on the first light spot signal.

[0040] (III) Beneficial Effects

[0041] The nozzle clogging detection device for a printhead provided in this application embodiment generates a parallel infrared laser beam along the extension line of the nozzle array of the printhead using an infrared laser generation unit. A spot detection unit detects the spot signal formed by the infrared laser on a detection plane aligned with the normal direction of the target nozzle array, thus fixing and controlling the spatial relationship between the infrared laser path and the nozzle array. When a spray command is issued to a designated nozzle in the target nozzle array, a first spot signal is acquired at a preset time interval after the spray command is issued. This allows the first spot signal to correspond to the spray state of the designated nozzle, thereby achieving accurate detection of the working state of the designated nozzle and improving the targeting and accuracy of nozzle clogging detection.

[0042] Furthermore, this application incorporates a translation mechanism to drive the infrared laser generating unit and the spot detection unit to synchronously translate along the nozzle array arrangement direction, thereby adapting the infrared laser path to the target nozzle array. Through this synchronous translation method, the infrared laser path can sequentially correspond to nozzles at different positions in the nozzle array without requiring a separate detection structure for each nozzle. This ensures detection accuracy while reducing the complexity of the device structure and improving its adaptability to multiple nozzle arrays.

[0043] Furthermore, the blockage detection unit described in this application controls the movement of the infrared laser generation unit and the spot detection unit through the translation mechanism, so that the infrared laser path is located on a plane jointly defined by the array extension direction of the target nozzle array and the direction perpendicular to the array extension direction on the spray side, and the infrared laser path is parallel to the array extension direction, thereby spatially defining a stable detection area. This defined detection area ensures that the first spot signal acquired by the spot detection unit mainly originates from the spraying behavior of the designated nozzle, reducing interference from adjacent nozzle spraying or environmental factors on the detection results and improving the reliability of the detection results.

[0044] Meanwhile, since this application detects the working state of the specified nozzle based on the light spot signal formed by infrared laser on the detection plane, it does not require relying on printing test pages or manually observing the printing results, and it does not require the use of complex image acquisition and image processing algorithms. This makes it easy for the nozzle blockage detection unit to automatically control and judge the process, which is conducive to the automation of nozzle blockage detection.

[0045] In summary, this application achieves a relatively simple, reliable, adaptable to nozzle arrays, and easily automated printhead nozzle clogging detection device through the coordinated operation of the infrared laser path, detection plane, translation mechanism, and first spot signal acquisition timing. This overcomes the problems of insufficient nozzle clogging detection, complex structure, or low degree of automation in the prior art. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the structure of a nozzle clogging detection device for a printhead according to an embodiment of this application;

[0047] Figure 2 This is a schematic diagram of a spot image corresponding to a first spot signal according to an embodiment of this application;

[0048] Figure 3 This is a schematic diagram of a light spot image with dark spots corresponding to a first light spot signal according to an embodiment of this application;

[0049] Figure 4 This is a schematic diagram of a dark spot within the effective detection area according to an embodiment of this application;

[0050] Figure 5 This is a schematic diagram showing a dark spot not within the effective detection area according to an embodiment of this application.

[0051] Reference numerals: 1: Infrared laser generation unit; 2: Spot detection unit; 3: Print head; 4: Target nozzle array; 5: Infrared laser path; 6: Ink droplet; 7: Projection point of the specified nozzle position on the detection plane; 8: Center position; 9: Boundary ray; 61: Dark spot. Detailed Implementation

[0052] To better explain and facilitate understanding of this application, the following detailed description of the application is provided in conjunction with the accompanying drawings and specific embodiments.

[0053] In related technologies, detection device solutions for printhead nozzle clogging can be broadly categorized as follows:

[0054] The first type is the detection scheme based on print result analysis. This scheme typically involves printing a test page or a specific test pattern, and the user visually inspects it for broken lines, insufficient ink, or abnormal ribbon patterns to determine if the nozzles are clogged. Some improved schemes utilize scanning devices or image recognition algorithms to analyze the print results, achieving semi-automatic or automatic detection. However, this type of scheme is essentially a result-based detection method, as the detection occurs after printing is complete, making it impossible to obtain the true working status information of the nozzles during the transient printing phase. Furthermore, this scheme is highly dependent on the printing media, the printed content, and ambient lighting conditions, and the manual observation method is highly subjective, making it difficult to achieve stable, real-time, and high-precision automated detection.

[0055] The second category is droplet 6 trajectory detection based on optical imaging. This method captures the flight trajectory or morphological changes of droplets 6 in the ejection side space using a high-speed camera or dedicated optical system, and analyzes whether the nozzle is functioning properly using image processing algorithms. While this method can obtain relatively intuitive droplet 6 information during ejection and has relatively high detection accuracy, it typically requires complex optical imaging structures, high-speed image acquisition modules, and image processing algorithms with high computing power. The overall system structure is complex and costly, and it has strict requirements for installation space and system integration conditions, making it difficult to promote and apply in ordinary printing equipment.

[0056] The third category is detection schemes based on drive signals or electrical characteristic analysis. For piezoelectric printheads, the presence of nozzle blockage or ejection abnormalities can be indirectly determined by analyzing the changes in current and voltage waveforms or feedback signal characteristics of the driving piezoelectric element. However, this type of scheme is easily affected by factors such as individual circuit differences, temperature changes, and electromagnetic interference, resulting in limited stability of the detection results. Furthermore, this method is mainly applicable to specific types of printheads and lacks good versatility for thermal inkjet printheads, making it difficult to meet the application requirements of different printhead structures.

[0057] In summary, existing nozzle clogging detection solutions either rely on print result analysis, resulting in low automation and poor real-time performance; or employ complex optical imaging systems, leading to complex structures and high costs; or depend on indirect judgment using electrical signals, resulting in insufficient versatility and limited reliability. Therefore, the existing technology as a whole lacks a nozzle clogging detection solution that is relatively simple in structure, cost-controllable, capable of accurately detecting specific nozzles in the target nozzle array 4, and easy to automate.

[0058] Further analysis reveals a common flaw in existing nozzle clogging detection solutions: none can fully assess a nozzle's operational status using a single spray action. For methods based on printed test pages, multiple line segments or complete test patterns are typically printed continuously, with the cumulative results of multiple sprays determining whether broken lines or missing areas exist; a single droplet spray is insufficient for this assessment. For droplet trajectory detection based on optical imaging, continuous high-speed camera capture of droplet flight and multi-frame image fitting or morphological analysis are required, necessitating multiple sprays as analysis samples; a single spray action alone is insufficient for stable and reliable detection. Similarly, detection methods based on drive signals or electrical characteristics analysis rely on statistical characteristics of the drive waveform or multi-cycle comparisons, requiring data from multiple spray cycles for analysis; a single spray action alone is insufficient for accurately determining the nozzle's operational status.

[0059] Therefore, existing technologies rely on accumulated data from multiple injections or continuous sampling results, making it impossible to complete a comprehensive and reliable detection of the nozzle's working status when the target nozzle performs only one injection action. This not only increases detection time but may also lead to additional ink consumption, reduced printing efficiency, and adversely affect the printhead's lifespan. To address this, this application provides a nozzle clogging detection device and method for a printhead 3, and a printing device. An infrared laser generation unit 1 generates a parallel infrared laser beam along the extension line of the nozzle array of the printhead 3, and a spot detection unit 2 detects the spot signal formed by the infrared laser on a detection plane aligned with the normal direction of the target nozzle array 4. Simultaneously, a translation mechanism drives the infrared laser generation unit 1 and the spot detection unit 2 to synchronously translate along the nozzle array arrangement direction, adapting the infrared laser path 5 to the target nozzle array 4. When an injection command is issued to a designated nozzle in the target nozzle array 4, a first spot signal is acquired at a preset time interval after the injection command is issued, and the working status of the designated nozzle is detected based on the first spot signal. Since the spatial relationship between the detection plane and the infrared laser path 5 is predetermined, and the detection time precisely corresponds to the spraying action, the working state of the nozzle can be determined by the first spot signal after only one spraying action from the target nozzle, without the need for continuous spraying or multiple sampling. Therefore, this application achieves complete detection of the working state of a specified nozzle through a single spraying action, ensuring detection reliability while reducing detection time and resource consumption, and improving detection efficiency.

[0060] To better understand the above technical solutions, exemplary embodiments of this application will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this application can be understood more clearly and thoroughly, and that the scope of this application can be fully conveyed to those skilled in the art.

[0061] Figure 1 This is a schematic diagram of the nozzle clogging detection device for a printhead 3 according to an embodiment of this application. Figure 1 As shown, the nozzle clogging detection device for the printhead 3 includes:

[0062] Infrared laser generating unit 1 is used to generate a parallel infrared laser beam on the extension line of the nozzle array of the printhead 3; the unit includes an infrared laser that generates a laser with a wavelength of 750~3000nm and a lens group for laser focusing.

[0063] The spot detection unit 2 is used to detect the spot signal formed by the infrared laser on the detection plane that is aligned with the normal direction of the target nozzle array 4;

[0064] In practical implementation, the infrared laser generation unit 1 can employ an 850nm semiconductor infrared laser. A lens group is used to shape the emitted laser beam into a parallel beam, which then illuminates the printhead 3 along the extension line of the nozzle array. The spot detection unit 2 can employ a high-sensitivity photodetector or photodiode array to capture the spot signal formed by the infrared spot on a detection plane aligned with the normal direction of the target nozzle array 4. For example, when the target nozzle performs inkjet printing, the ejected ink droplets 6 may cause obstruction or diffraction of the infrared beam. The spot detection unit 2 can record the changes in spot intensity in real time, thereby obtaining the transient operating status information of the nozzle.

[0065] A translation mechanism is used to drive the infrared laser generating unit 1 and the spot detection unit 2 to translate synchronously along the nozzle array arrangement direction so that the infrared laser path 5 is adapted to the target nozzle array 4.

[0066] For example, the translation mechanism can use linear guides and stepper motors to drive the infrared laser generation unit 1 and the spot detection unit 2 to move synchronously along the nozzle array arrangement direction, ensuring that the infrared laser path 5 is completely aligned with different nozzle arrays, so that the detection plane covers the entire length of the nozzle array. The blockage detection unit, by controlling the translation mechanism and acquiring spot signals, can detect the working status of any specified nozzle in the target nozzle array 4. For example, after issuing a spray command to a specified nozzle, the blockage detection unit will acquire spot signals within a preset time interval and determine whether the nozzle is spraying normally or blocked based on the change in spot intensity.

[0067] A clogging detection unit is electrically connected to the printhead 3, the infrared laser generating unit 1, the spot detection unit 2, and the translation mechanism. The clogging detection unit controls the movement of the infrared laser generating unit 1 and the spot detection unit 2 through the translation mechanism, so that the infrared laser path 5 is located on a plane jointly determined by the array extension direction of the target nozzle array 4 and the direction perpendicular to the array extension direction on the spray side, and the infrared laser path 5 is parallel to the array extension direction. When the infrared laser generating unit 1 emits infrared laser and issues a spray command to a designated nozzle in the target nozzle array 4, the spot detection unit 2 acquires a first spot signal and detects the working state of the designated nozzle based on the first spot signal, wherein the first spot signal is obtained at a preset time interval after the spray command is issued.

[0068] In this application, the target nozzle array 4 is typically arranged in a regular pattern, with each nozzle ejecting droplets along a fixed spray direction. The array extension direction refers to the direction in which the nozzles are arranged, such as the direction of a row of nozzles. The direction perpendicular to the array extension direction on the spray side is not arbitrarily perpendicular within a plane, but rather refers to the downward direction along the nozzle spray direction, which is the direction in which the ink droplets 6 fall freely under gravity. This direction is perpendicular to the array extension direction, and therefore can jointly define a plane with the horizontal arrangement direction of the nozzle array.

[0069] See Figure 1 Taking a specific application scenario as an example, suppose there is a target nozzle array 4 on the printhead 3, where a nozzle is numbered N1. The clogging detection device sends a spray command to nozzle N1 through the clogging detection unit. Under standard atmospheric pressure, the delay time from when nozzle N1 receives the spray command to when it actually ejects ink droplet 6 is fixed, and the flight time of ink droplet 6 from leaving nozzle N1 to moving to the detection plane is also fixed. By sending a spray command to nozzle N1 in the nozzle array through the controller, the spray time of nozzle N1 can be accurately determined, and the time interval between ink droplet 6 reaching the center point of the infrared beam can be predicted.

[0070] During this time interval, the spot detection unit 2 collects the infrared laser spot on the detection plane. If the N1 nozzle is working normally, the ink droplet 6 will fly along a predetermined trajectory and reach the center region of the infrared beam, causing the spot signal to form a distinct dark spot 61 at that location, such as... Figure 2 As shown. This dark spot 61 corresponds to the transient signal change caused by the ink droplet 6 blocking the infrared beam. The first spot signal obtained by the blockage detection unit after analyzing the preset time interval after the ejection command can immediately determine that the nozzle is working normally. Conversely, if the N1 nozzle is blocked or has an ejection abnormality, the spot detection unit 2 will not detect the corresponding dark spot 61 or spot change signal after the preset time interval after the ejection command is issued to the N1 nozzle in the nozzle array. The blockage detection unit can then determine that the nozzle is blocked and identify the blockage location. The entire process only relies on one ejection action of the target nozzle to complete the detection of the nozzle's working status, without the need for repeated ejection or multiple sampling, thereby greatly improving detection efficiency, saving ink consumption, and reducing nozzle wear.

[0071] like Figure 4 As shown, in this embodiment, the preset time interval includes the jetting delay from when the printhead 3 receives the jetting command to when the ink droplet 6 is ejected, and the flight time required for the ink droplet 6 to move to the center position 8 of the infrared laser path 5 after being ejected from the nozzle.

[0072] For example, assuming a nozzle in printhead 3 is numbered N1, under standard operating conditions, its ejection delay is 3 milliseconds, meaning the time from when printhead 3 receives the ejection command to when droplet 6 is actually ejected from the nozzle is 3 milliseconds. After droplet 6 leaves the nozzle, assuming it requires a flight time of 7 milliseconds under standard atmospheric pressure to reach the center position 8 of the infrared laser path 5, the preset time interval for this nozzle is the ejection delay of 3 milliseconds plus the flight time of 7 milliseconds, totaling 10 milliseconds. In actual detection, when the clogging detection device sends an ejection command to nozzle N1, it will acquire the first spot signal through the spot detection unit 2 after the preset 10 millisecond time interval. If nozzle N1 is working properly, droplet 6 will accurately reach the center of the infrared laser path 5, causing the first spot signal to form a noticeable dark spot 61 or signal attenuation at that position. The clogging detection unit can determine that the nozzle is in normal condition based on the first spot signal. If nozzle N1 becomes clogged, spot detection unit 2 will also acquire a first spot signal within the same preset time interval. However, no dark spot 61 will appear in this first spot signal. The clogging detection unit can determine that the nozzle is clogged based on the first spot signal. The entire detection process can be completed with only one spray action from the target nozzle, without the need for repeated spraying or continuous sampling, thus achieving fast, accurate, and automated nozzle status judgment. By setting the preset time interval, the spray action of each nozzle and the time when the ink droplet 6 arrives at the detection position can be accurately matched, allowing a single spray to complete the entire detection. This avoids the problem of traditional methods relying on multiple sprays to accumulate data, while also reducing ink consumption and detection time.

[0073] In this embodiment, the infrared laser generated by the infrared laser generation unit 1 has a wavelength range of 750nm to 3000nm. The cross-section of the infrared laser is circular or rectangular, and the diameter of the light spot image formed by the infrared laser on the detection plane is larger than the maximum diameter of the ink droplet 6 ejected from the nozzle. For example, assuming the maximum diameter of the ink droplet 6 ejected from the nozzle is 50 micrometers, the diameter of the infrared light spot can be set to 100 to 1000 micrometers to ensure that the ink droplet 6 will inevitably block the central area of ​​the light spot during its flight, thereby generating a significant change in the light spot signal. In other words, the diameter of the light spot image is sufficient to cover the possible offset range of the ink droplet 6, ensuring that each ejection action can be accurately detected.

[0074] In practical applications, an infrared laser with a wavelength of 850nm can be selected for detection. This wavelength belongs to the near-infrared band, which can penetrate air and will not interfere with the printer's operating environment or ink composition. Furthermore, when the infrared laser has a circular beam cross-section, the light spot appears as a uniform circle on the detection plane; when the infrared laser has a rectangular beam cross-section, the light spot appears as a long strip on the detection plane.

[0075] Specifically, the blockage detection unit is further configured to determine the light spot signal intensity difference between the first light spot signal and the pre-acquired second light spot signal, and compare the light spot signal intensity difference with a preset threshold, wherein:

[0076] If the difference in light spot signal intensity is greater than the preset threshold, it is determined that an ink droplet 6 has passed through the infrared laser path 5, so as to determine that the designated nozzle is in normal inkjet state.

[0077] If the difference in light spot signal intensity is less than or equal to the preset threshold, the designated nozzle is determined to be in a blocked state.

[0078] The second spot signal is the spot signal formed on the detection plane by the infrared laser when no ink droplet 6 passes through the infrared laser path 5.

[0079] For example, the second spot signal is a reference spot signal formed on the detection plane when no ink droplet 6 passes through the infrared laser path 5. For instance, when all nozzles are not performing any ejection action, the infrared laser generation unit 1 continuously emits infrared laser light, and the stable spot signal collected by the spot detection unit 2 is used as the reference value. Assuming the detected spot signal intensity is 100 units, this value is the signal intensity of the second spot signal.

[0080] When the clogging detection unit sends a spray command to a designated nozzle (e.g., nozzle N1), it acquires the first spot signal at a preset time interval. If nozzle N1 sprays normally, the ink droplet 6 will reach the center position 8 of the infrared laser path 5 within the theoretical time window, blocking the infrared beam and forming a dark spot 61 at the center of the spot, corresponding to a decrease in the spot signal intensity. For example, if the spot signal decreases from the original reference value of 100 units to 60 units, the difference in spot signal intensity is 40 units. Assume a preset threshold of 20 units. When the difference in spot signal intensity is greater than 20 units, it indicates that the intensity of the spot signal has significantly decreased, indicating that ink droplet 6 has passed through the infrared laser path 5, and it can be determined that the designated nozzle is in normal ink spraying state. Conversely, if nozzle N1 is clogged or spraying abnormally, the ink droplet 6 fails to reach the detection area within the preset time interval, the infrared beam will not be blocked, and the spot signal intensity will remain basically near the reference value. For example, if the light spot signal changes only from 100 units to 95 units, the light spot signal intensity difference is 5 units, which is less than or equal to the preset threshold of 20 units. At this time, it can be determined that the specified nozzle is in a blocked state.

[0081] It is important to emphasize that this judgment logic can be completed based solely on the first spot signal corresponding to a single injection action. Since a stable second spot signal is pre-acquired as a benchmark, and the detection time window is precisely determined by combining the injection delay and flight time, the transient signal changes generated during a single injection can constitute a complete judgment basis. There is no need to continuously inject from the same nozzle or sample multiple times, thus achieving rapid and accurate blockage identification.

[0082] In some embodiments of this application, the blockage detection unit is further configured to acquire a corresponding spot image based on the first spot signal, see [link to relevant documentation]. Figure 2 And determine whether a dark spot 61 appears in the spot image of the first spot signal. If no dark spot 61 appears, determine that the designated nozzle is blocked. Figure 3 As shown. The dark spot 61 is a localized area of ​​reduced light intensity in the light spot image caused by the ink droplet 6 passing through the infrared laser path 5.

[0083] In this embodiment, since the spot image formed by the infrared laser on the detection plane has stable spatial distribution characteristics, when no ink droplet 6 passes by, the spot image exhibits a uniform brightness distribution, for example, presenting a circular or rectangular spot with basically uniform brightness. See [link to documentation]. Figure 3 When the designated nozzle is spraying normally, the ink droplet 6 reaches the center region of the infrared laser path 5 within a preset time interval, blocking part of the beam. This causes a momentary decrease in brightness in a local area of ​​the spot image, thus forming a noticeable dark spot 61 in the spot image. (See [link]). Figure 2 .

[0084] For example, assuming the grayscale value range of the light spot image is 0–255, when no ink droplet 6 passes through, the grayscale value in the central region of the light spot stabilizes at around 200. Figure 3 As shown. When the designated nozzle sprays normally, after the ink droplet 6 reaches the detection area according to the theoretical flight time, the gray value of the central area of ​​the spot may drop instantaneously to 120 or even lower, appearing as a noticeable dark spot 61 in the image, as shown. Figure 2 As shown, the clogging detection unit acquires the spot image through the image acquisition module and detects whether there are areas with local gray values ​​lower than a preset threshold (i.e., dark spots 61). If dark spot 61 is detected, it can be determined that ink droplet 6 has passed through the infrared laser path 5, thus confirming that the designated nozzle is in normal inkjet printing mode. Conversely, if the designated nozzle is clogged or has an abnormal spraying, ink droplet 6 will fail to reach the center area of ​​the infrared laser path 5 within a preset time interval, and the overall brightness distribution of the spot image will remain uniform, without any obvious local gray value reduction areas. In this case, the clogging detection unit determines that the designated nozzle is clogged because dark spot 61 does not appear in the spot image.

[0085] It should be noted that since the jetting delay and droplet flight time are predictable and stable, the clogging detection unit only needs to acquire a spot image once at a preset time interval after issuing the jetting command to the target nozzle to complete the detection of dark spot 61. Therefore, the working status of the nozzle can be determined by the first spot image formed by the single jetting action of the target nozzle, without the need for continuous jetting or multiple image sampling, thus achieving fast and efficient nozzle clogging detection.

[0086] Optionally, in some embodiments of this application, the blockage detection unit is further configured to, when a dark spot 61 appears in the spot image of the first spot signal, determine whether the designated nozzle has a spray direction offset based on the position of the dark spot 61 in the spot image and a preset effective detection area of ​​the spot image, wherein, see Figure 4 The line connecting the projection point 7 of the specified nozzle position on the detection plane and the center position 8 of the spot image formed by the infrared laser on the detection plane is used as the reference axis. Two boundary rays 9 extend from both sides of the reference axis at an angle not greater than the preset jet deviation angle. The effective detection area is the intersection of the area surrounded by the boundary rays 9 and the projection area of ​​the spot image on the detection plane.

[0087] In this embodiment, when a dark spot 61 is detected in the spot image corresponding to the first spot signal, the clogging detection unit not only determines whether an ink droplet 6 has passed through the infrared laser path 5, but also further determines whether the designated nozzle has a spray direction deviation based on the position of the dark spot 61 in the spot image. Specifically, the projection point 7 of the designated nozzle position on the detection plane is first determined. This projection point 7 can be pre-calibrated using the structural parameters of the printhead 3 and the geometric position of the nozzle array. Simultaneously, the spot image formed by the infrared laser on the detection plane has a fixed center position 8, which can be determined during system initialization using the spot image in a non-spraying state.

[0088] The line connecting the projection point 7 of the designated nozzle and the center position 8 of the light spot image is used as the reference axis. This reference axis represents the theoretical flight direction of the ink droplet 6 when it is ejected normally. When the nozzle is normal and there is no directional deviation, the ink droplet 6 should fly along the direction of this reference axis and form a dark spot 61 in the central area of ​​the light spot image.

[0089] Based on this, two boundary rays 9 extend from both sides of the reference axis, with an angle no greater than a preset spray deviation angle to the reference axis. For example, the preset spray deviation angle can be set to ±2°. These two boundary rays 9, together with the projection area of ​​the spot image on the detection plane, define a fan-shaped region. The effective detection area is the intersection of this fan-shaped region and the projection area of ​​the spot image.

[0090] For example, see Figure 4 Assume the light spot image is circular on the detection plane with a diameter of 100 micrometers, and the center position 8 is known; the theoretical projection point 7 of the specified nozzle is located 0.5 mm directly above the center of the light spot; the ejection deviation angle is ±2°. When the nozzle ejects normally, the ink droplet 6 should fly along the reference axis and form a dark spot 61 near the center position 8 of the light spot image, and the position of this dark spot 61 should fall within the aforementioned effective detection area. If the detected dark spot 61 is located within this effective detection area, the nozzle ejection direction is determined to be normal.

[0091] Conversely, see Figure 5 If dark spot 61 appears, but its position is significantly deviated from the reference axis, for example, exceeding the ±2° angle range and falling outside the effective detection area, it indicates that the flight trajectory of ink droplet 6 has deviated, and it can be determined that the specified nozzle has a spray direction deviation problem. At this time, even if the nozzle is not completely blocked, the abnormal spray accuracy can be identified, so that maintenance or correction can be performed in advance.

[0092] It should be noted that the above judgment is still based on the first spot image formed by a single spraying action. By acquiring a spot image at a preset time interval after issuing the spraying command to the target nozzle to obtain the position of the dark spot 61 generated by a single spray, it is possible to simultaneously determine whether the nozzle is blocked and whether there is a spraying direction deviation. In other words, it is possible to simultaneously complete the dual judgment of whether the nozzle is blocked and whether there is a spraying direction deviation in a single spraying action, without the need for trajectory statistical analysis of multiple sprays.

[0093] Optionally, in some embodiments of this application, the blockage detection unit is further configured to, when a dark spot 61 appears in the spot image of the first spot signal, extract image features from the spot image and input the extracted image features into a pre-trained image recognition model to determine the direction and angle of ink droplet 6 ejection, compare the ejection angle with a preset angle tolerance range, and determine that the specified nozzle has an ejection direction offset when the ejection angle exceeds the preset angle tolerance range; wherein, the image features include the coordinates of the center position 8 of the dark spot 61, the area parameter, and the local grayscale decrease amplitude, the local grayscale decrease amplitude being the difference between the average pixel grayscale value of the dark spot 61 and the average pixel grayscale value of the spot area other than the dark spot 61 in the spot image, and the image recognition model is configured to output the value of the corresponding ink droplet 6 ejection angle based on the image features in the spot image;

[0094] When the image recognition model is pre-trained using training data, the training data includes image features of the light spot images collected under different known spray angle conditions and the corresponding spray angle annotation information of the ink droplets 6.

[0095] For example, suppose the light spot image is a grayscale image with a resolution of 512×512 pixels. When no ink droplet 6 passes through, the average pixel grayscale value of the light spot area is 200. See [link / reference] Figure 2 When ink droplet 6 passes through, it forms a dark spot 61 in the light spot image. The average pixel grayscale value of the dark spot 61 region is 130. Therefore, the local grayscale decrease is 200 minus 130, which is 70. Simultaneously, the center position coordinates of dark spot 61 (e.g., (260, 248)) and the corresponding area parameters of dark spot 61 can be extracted using an image segmentation algorithm. For example, the number of pixels in dark spot 61 is 120. The aforementioned center position coordinates, area parameters, and local grayscale decrease together constitute the image features.

[0096] Subsequently, the extracted image features are input into a pre-trained image recognition model. This image recognition model can be a neural network model or other supervised learning model, and its output is the numerical value of the ejection angle of the corresponding ink droplet 6. For example, the model outputs an ejection angle of 1.8° for ink droplet 6 based on the input image features. Assume a preset angle tolerance range is set, for example, ±2°. When the ejection angle output by the model is within ±2°, the ejection direction of the specified nozzle is determined to be normal; when the ejection angle exceeds this preset angle tolerance range, for example, reaching 3.5°, it is determined that the specified nozzle has an ejection direction deviation.

[0097] Furthermore, when the image recognition model is pre-trained using training data, the training data includes image features of the light spot images acquired under different known spray angle conditions and the corresponding spray angle annotation information of the ink droplet 6. For example, during the experimental calibration stage, the nozzle installation angle can be adjusted or the spray direction controlled to allow the ink droplet 6 to be sprayed at different known spray angles such as 0°, ±1°, ±2°, and ±3°, and the corresponding light spot images can be acquired. Image features are then extracted, and a mapping relationship between image features and spray angles is established. Through the above training process, the image recognition model is able to output the spray angle value of the ink droplet 6 based on the image features.

[0098] It should be noted that the above image feature extraction and spray angle determination are both based on the first spot image formed by a single spray action of the specified nozzle. In other words, using only the image information of the dark spot 61 generated by a single spray, it is possible to determine the direction and spray angle of the ink droplet 6 after determining whether the ink droplet 6 exists, and to determine whether it exceeds the preset angle tolerance range. This achieves accurate determination of the spray direction deviation without the need for multiple consecutive sprays or trajectory statistical analysis.

[0099] Preferably, the blockage detection unit is further configured to, when a dark spot 61 appears in the light spot image of the first light spot signal, acquire the feature of the dark spot 61 in the light spot image, and determine whether the ink droplet 6 corresponding to the dark spot 61 is rotating based on the feature of the dark spot 61.

[0100] The features of the dark spot 61 in the light spot image include: the roundness of the outline of the dark spot 61, the aspect ratio, the smoothness of the edge of the dark spot 61, and the skewness of the edge curve.

[0101] The degree of skewness of the edge curve of the dark spot 61 is obtained in the following way:

[0102] Based on the edge curve coordinates of the dark spot 61 extracted from the spot image, the edge curve is fitted, and the angle between the edge curve and the reference axis from the nozzle position to the center of the spot image is calculated. The angle is then used as a quantified value of the skewness of the edge curve.

[0103] In this embodiment, the clogging detection unit is used not only to determine whether the designated nozzle is clogged and whether there is a jet direction deviation, but also to determine whether the ink droplet 6 rotates during the jetting process. It should be noted that when the rotating ink droplet 6 contacts the printing medium (e.g., paper, coating, or glossy plate), its contact area and shape will change. The ink droplet may exhibit a stringy, elliptical, or irregular shape, thus affecting print clarity and resolution. Therefore, determining whether the ink droplet 6 rotates is of great significance.

[0104] Specifically, when a dark spot 61 appears in the light spot image of the first light spot signal, the blockage detection unit acquires the feature of the dark spot 61 in the light spot image and determines whether the ink droplet 6 corresponding to the dark spot 61 is rotating based on the feature of the dark spot 61.

[0105] After the designated nozzle performs a spraying action, a spot image is acquired at a preset time interval after the spraying command is issued. If a dark spot 61 appears in the spot image, the region of the dark spot 61 is first segmented and its contour extracted to obtain the set of edge curve coordinates of the dark spot 61. The features of the dark spot 61 include the roundness of the dark spot 61 contour, its aspect ratio, the smoothness of the edge of the dark spot 61, and the skewness of the edge curve.

[0106] The roundness of the outline of dark spot 61 can be calculated using the formula "roundness = 4π × area ÷ perimeter²". When dark spot 61 is a regular circle, the roundness is close to 1; if dark spot 61 is stretched or deformed, the roundness is less than 1. For example, the roundness of dark spot 61 formed by a normal, non-rotating ink droplet 6 can be 0.95, while the roundness of dark spot 61 formed by a rotating or deformed ink droplet 6 may decrease to 0.78.

[0107] The aspect ratio is obtained by calculating the ratio of the length to the width of the smallest circumscribed rectangle of the dark spot 61. For example, the aspect ratio of the dark spot 61 of a normal ink droplet 6 is about 1.05; while the aspect ratio of the dark spot 61 of an ink droplet 6 with rotation or aerodynamic disturbance may reach 1.30 or higher.

[0108] The smoothness of the edge of the dark spot 61 can be quantified by the rate of change of edge curvature or the degree of edge gradient fluctuation. For example, by using the standard deviation of the gray-scale gradient of the pixels at the edge of the dark spot 61 as a smoothness parameter, the smoothness parameter of the edge of a normal dark spot 61 can be 5, while the smoothness parameter of the rotating ink droplet 6 may increase to 12 due to the irregular edge caused by the change in posture.

[0109] The degree of skewness of the edge curve of the dark spot 61 is obtained as follows: First, based on the coordinates of the edge curve of the dark spot 61 extracted from the spot image, the principal axis of the edge curve is fitted using the least squares method, for example, by fitting an ellipse to obtain the major axis direction; then, the line connecting the projection point 7 of the nozzle position on the detection plane to the center position 8 of the spot image is used as the reference axis; next, the angle between the fitted principal axis of the edge curve and the reference axis is calculated, and this angle is used as the quantitative value of the degree of skewness of the edge curve. For example, in the state of no rotation, the major axis direction of the dark spot 61 is basically coincident with the reference axis, and the angle can be 0.5°; if the ink droplet 6 rotates during flight, its aerodynamic forces are asymmetrical, and the dark spot 61 is tilted into an elliptical shape, then the angle between the fitted principal axis and the reference axis may reach 6° or 8°. When this angle exceeds a preset rotation judgment threshold (e.g., 3°), it can be determined that the ink droplet 6 corresponding to the dark spot 61 is rotating.

[0110] By extracting features of the dark spot 61, such as roundness, aspect ratio, edge smoothness, and skewness of the edge curve, quantitative analysis of the flight attitude of the ink droplet 6 was achieved. This expands the detection scope from simply determining the presence of the ink droplet 6 to determining whether it rotates, thus improving the detection dimensionality and information utilization. The skewness of the edge curve is quantified by fitting the edge curve and calculating its angle with the reference axis, providing a clear numerical basis for rotation judgment and avoiding reliance solely on human experience or subjective judgment, thereby improving the objectivity and repeatability of the judgment.

[0111] Meanwhile, the aforementioned rotation determination is still based on the first spot image, which originates from a single ejection action of a designated nozzle. In other words, under a single ejection action, it is possible not only to determine whether the nozzle is clogged and whether there is a deviation in the ejection direction, but also to further determine whether the ink droplet 6 is rotating, achieving multi-state synchronous detection without the need for additional detection hardware or multiple ejection sampling. Furthermore, by comprehensively analyzing the features of the dark spot 61, potential problems such as abnormal nozzle structure, unstable flow channels, or abnormal ink droplet 6 formation can be detected early, facilitating early warning, reducing printing defects, and improving print quality stability. Therefore, this embodiment achieves refined identification of the ink droplet 6's posture while maintaining a simple detection structure and fewer detection attempts, offering the advantages of rich detection information, high judgment accuracy, and high detection efficiency.

[0112] In this embodiment, the clogging detection unit is further configured to determine whether the ink droplet 6 corresponding to the dark spot 61 is rotating based on the characteristics of the dark spot 61, specifically including:

[0113] The feature of dark spot 61 is compared with the feature of dark spot 61 in normal state. The comparison includes: comparing the difference between the roundness of the outline of dark spot 61 and the roundness of the normal state with a preset roundness tolerance; comparing the difference between the aspect ratio of the outline of dark spot 61 and the aspect ratio of the normal state with a preset aspect ratio tolerance; comparing the difference between the smoothness of the edge of dark spot 61 and the smoothness of the normal state with a preset smoothness tolerance; and comparing the difference between the skewness of the edge curve of dark spot 61 and the skewness of the normal state with a preset skewness tolerance.

[0114] If the difference in any feature of dark spot 61 exceeds the corresponding preset tolerance, it is determined that the ink droplet 6 of the specified nozzle is rotating;

[0115] If all dark spot 61 features are within the corresponding preset tolerance range, it is determined that the ink droplet 6 of the specified nozzle is not rotating;

[0116] In detail, in this embodiment, determining whether the ink droplet 6 corresponding to the dark spot 61 is rotating based on the feature of the dark spot 61 specifically includes comparing the acquired feature of the dark spot 61 with the feature of the dark spot 61 in the normal state, and making a determination based on the comparison result.

[0117] The dark spot 61 in the normal state is characterized by standard feature parameters obtained in advance through calibration experiments under the condition that the nozzle is working normally and the ink droplet 6 is not rotating. These parameters include normal state roundness, normal state aspect ratio, normal state smoothness, and normal state skewness. The preset roundness tolerance, preset aspect ratio tolerance, preset smoothness tolerance, and preset skewness tolerance are allowable deviation ranges preset according to the actual equipment accuracy and printing requirements. Specific comparison methods include:

[0118] First, the difference between the roundness of the contour of dark spot 61 and the roundness in the normal state is compared with a preset roundness tolerance. For example, the normal roundness is 0.95, and the preset roundness tolerance is ±0.05; if the actual detected roundness of dark spot 61 is 0.88, the difference is 0.07, which is greater than the preset roundness tolerance of 0.05, thus the roundness feature is determined to be abnormal. Second, the difference between the aspect ratio of the contour of dark spot 61 and the aspect ratio in the normal state is compared with a preset aspect ratio tolerance. For example, the normal aspect ratio is 1.05, and the preset aspect ratio tolerance is ±0.10; if the actual detected aspect ratio is 1.22, the difference is 0.17, which is greater than the preset aspect ratio tolerance, thus the aspect ratio feature is determined to be abnormal. Third, the difference between the smoothness of the edge of dark spot 61 and the smoothness in the normal state is compared with a preset smoothness tolerance. For example, the smoothness parameter in the normal state is 5, and the preset smoothness tolerance is ±3. If the detected value is 10, the difference is 5, which is greater than the tolerance of 3, so the smoothness feature is judged to be abnormal. Furthermore, the difference between the skewness of the edge curve of dark spot 61 and the skewness in the normal state is compared with the preset skewness tolerance. For example, the skewness in the normal state is 0.5°, and the preset skewness tolerance is ±2°. If the detected value is 4°, the difference is 3.5°, which exceeds the preset skewness tolerance range, so the skewness feature is judged to be abnormal. In the above comparison process, as long as the difference of any feature of dark spot 61 exceeds the corresponding preset tolerance range, it can be determined that the ink droplet 6 of the specified nozzle is rotating. That is to say, this embodiment adopts the judgment logic of "any feature exceeding the tolerance determines rotation", thereby improving the sensitivity to the abnormal posture of ink droplet 6. Conversely, if all features of the dark spot 61 are within the corresponding preset tolerance range—that is, if the roundness, aspect ratio, edge smoothness, and edge curve skewness of the dark spot 61 outline do not exceed their respective tolerance ranges—then it is determined that the ink droplet 6 of the specified nozzle has not rotated. Through the aforementioned multi-feature comparison mechanism, a comprehensive determination of whether the ink droplet 6 rotates is achieved, rather than relying solely on a single feature, thereby improving the accuracy and reliability of the judgment. Since a rotating ink droplet 6 may exhibit different morphological changes under different operating conditions, such as reduced roundness but minimal change in aspect ratio, or increased skewness but minimal change in roundness, the use of multi-parameter parallel comparison can effectively avoid missed or false judgments. Simultaneously, this judgment is still based on the first light spot image, which originates from a single spraying action of the specified nozzle. Therefore, in a single spraying action, not only can it be determined whether the nozzle is clogged or whether there is a spray direction deviation, but it can also be further determined whether the ink droplet 6 rotates, achieving multi-dimensional synchronous detection of the nozzle's operating state without the need for multiple sprays or additional detection devices.

[0119] Alternatively, determining whether the ink droplet 6 corresponding to the dark spot 61 is rotating based on the characteristics of the dark spot 61 specifically includes:

[0120] The dark spot 61 feature of the light spot image is input into a pre-trained rotation recognition model, and the recognition result of whether the ink droplet 6 corresponding to the dark spot 61 is rotated is output.

[0121] The rotation recognition model is obtained by training with ink droplet 6 training data, which includes:

[0122] Features of dark spot 61 and annotation information of non-rotated ink droplet 6 in the corresponding nozzle spot image collected under normal conditions;

[0123] The feature of dark spot 61 and the annotation information of ink droplet 6 rotation in the corresponding nozzle spot image collected under abnormal conditions.

[0124] For example, in this embodiment, determining whether the ink droplet 6 corresponding to the dark spot 61 is rotating based on the feature of the dark spot 61 specifically includes inputting the acquired feature of the dark spot 61 in the spot image into a pre-trained rotation recognition model, and the rotation recognition model outputting the recognition result of whether the ink droplet 6 corresponding to the dark spot 61 is rotating. The rotation recognition model is obtained through pre-training using ink droplet 6 training data, which includes two types of annotation information: the first type is training data under normal conditions, that is, when the nozzle is working normally and the ink droplet 6 is not rotating, the feature of the dark spot 61 in the spot image of the corresponding nozzle is collected and labeled as "ink droplet 6 is not rotating"; the second type is training data under abnormal conditions, that is, when the nozzle is rotating or spraying abnormally, the feature of the dark spot 61 in the spot image of the corresponding nozzle is collected and labeled as "ink droplet 6 is rotating". After training, the rotation recognition model can automatically determine whether the ink droplet 6 is rotating based on the input feature of the dark spot 61, thereby achieving accurate recognition of the nozzle spraying state. This method allows for the determination of the rotation state of ink droplets 6 based on the first spot image generated by a single jetting action, eliminating the need for additional high-speed cameras or multiple jetting samples. This improves detection efficiency, reduces detection costs, and enhances the real-time performance and automation level of nozzle status detection while ensuring detection accuracy.

[0125] The printhead nozzle clogging detection device provided in this application achieves rapid and accurate detection of the target nozzle status through the coordinated operation of the infrared laser generation unit 1, the spot detection unit 2, the translation mechanism, and the clogging detection unit. After issuing a single injection command to the target nozzle, the device acquires spot signals and spot images based on a preset time interval between the injection delay and the ink droplet 6 flight time. This allows for a comprehensive determination of whether the nozzle is clogged, the injection direction and angle of the ink droplet 6, and whether the ink droplet 6 is rotating. By comparing the intensity difference between the spot signal obtained during injection and the reference spot signal, it can accurately determine whether the ink droplet 6 has passed through the detection area, thereby quickly identifying nozzle clogging. Simultaneously, by analyzing the position and characteristics of the dark spot 61 in the spot image, and combining it with the preset effective detection area and reference axis, it can accurately determine whether the injection direction deviation and injection angle exceed the tolerance range. Furthermore, based on the roundness, aspect ratio, edge smoothness, and edge curve skewness of the dark spot 61, it can be determined whether the ink droplet 6 rotates during injection. This device can complete multi-dimensional judgments based solely on the transient signal and dark spot 61 image generated from a single spray, eliminating the need for repeated spraying or cumulative sampling. This significantly improves detection efficiency, reduces ink consumption, minimizes nozzle wear, and enables rapid, automated, and low-cost nozzle condition detection.

[0126] It should be noted that in this embodiment, the nozzle clogging detection of the printhead 3 is performed within the printer's internal maintenance station. The maintenance station is a dedicated area in the printer's design for cleaning, calibrating, and testing the printhead 3. This area is located in the printer's non-printing working area and has a specific spatial layout that ensures the printhead 3 can move freely during maintenance, while also facilitating the implementation of various testing and maintenance operations. Specifically, the maintenance station space is large enough to accommodate the translational movement of the print head 3 along the nozzle array direction, while allowing the infrared laser generating unit 1 and the spot detection unit 2 to move synchronously in the extension direction of the nozzle array and in the direction perpendicular to it, so as to achieve effective coverage of the entire nozzle array. The maintenance station is equipped with support and guiding mechanisms to fix the position of the print head 3 and ensure its stability during the detection process, thereby ensuring the accurate relative position between the infrared light path and the nozzle array and avoiding spot signal acquisition errors caused by print head 3 shaking or offset. The maintenance station is usually equipped with a nozzle spray interface or test liquid path to issue spray commands to designated nozzles during the detection, while ensuring that droplet spray does not contaminate the detection light path or interfere with spot signal acquisition. Therefore, by moving the print head 3 into the maintenance station and combining the translational operation of the infrared laser generating unit 1 and the spot detection unit 2 along the nozzle array direction, the accurate detection of the nozzle working status can be completed within the maintenance station space, ensuring the reliability of blockage detection.

[0127] In addition, this application embodiment also provides a printing device, including: a print head 3, and a nozzle clogging detection device for the print head 3 in the above embodiment.

[0128] This application also provides a method for detecting nozzle clogging in a printing device, including the following steps:

[0129] The infrared laser generating unit 1 and the spot detection unit 2 are driven to translate along the nozzle array arrangement direction so that the infrared laser path 5 is adapted to the target nozzle array 4.

[0130] The infrared laser generating unit 1 is controlled to emit infrared laser, such that the infrared laser path 5 is located on a plane jointly determined by the array extension direction of the target nozzle array 4 and the direction that forms a perpendicular relationship with the array extension direction on the spray side, and the infrared laser path 5 is parallel to the array extension direction.

[0131] A spraying command is issued to a designated nozzle in the target nozzle array 4;

[0132] The first spot signal is obtained by the spot detection unit 2, and the first spot signal is obtained at a preset time interval after the spray command is issued;

[0133] The working status of the designated nozzle is detected based on the first light spot signal.

[0134] The nozzle clogging detection method of the printing device in this embodiment achieves precise alignment between the infrared laser path 5 and the target nozzle array 4 by controlling the infrared laser generation unit 1 and the spot detection unit 2 to synchronously translate along the nozzle array direction. This allows for coverage of the entire nozzle array without the need for additional complex mechanical adjustments. Secondly, by acquiring the first spot signal at a preset time interval after a single injection command, the working state of the specified nozzle can be quickly determined without repeated injections, greatly improving detection efficiency while reducing ink consumption and nozzle wear. Furthermore, this method can accurately identify nozzle clogging by utilizing the transient changes in the spot signal and further determine the nozzle injection direction and ink droplet state by combining the dark spot features 61 of the spot image. This enables comprehensive and accurate nozzle state detection with a single injection. This "single injection, multi-parameter determination" capability is unattainable by existing technologies, significantly improving the automation monitoring level and efficiency of the printing device.

[0135] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0136] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that they are in indirect contact through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0137] In the description of this specification, the terms "one embodiment," "some embodiments," "embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0138] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make modifications, alterations, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A nozzle clogging detection device for a printhead, characterized in that, include: An infrared laser generating unit is used to generate a parallel infrared laser beam along the extension line of the nozzle array in the printhead. A spot detection unit is used to detect the spot signal formed by the infrared laser on a detection plane that is aligned with the normal direction of the target nozzle array. A translation mechanism is used to drive the infrared laser generating unit and the spot detection unit to translate synchronously along the nozzle array arrangement direction so that the infrared laser path is adapted to the target nozzle array. A clogging detection unit is electrically connected to the printhead, the infrared laser generating unit, the spot detection unit, and the translation mechanism. The clogging detection unit controls the movement of the infrared laser generating unit and the spot detection unit through the translation mechanism, so that the infrared laser path is located on a plane jointly determined by the array extension direction of the target nozzle array and the direction perpendicular to the array extension direction on the spray side, and the infrared laser path is parallel to the array extension direction. When the infrared laser generating unit emits infrared laser and issues a spray command to a designated nozzle in the target nozzle array, the spot detection unit acquires a first spot signal and detects the working state of the designated nozzle based on the first spot signal, wherein the first spot signal is obtained at a preset time interval after the spray command is issued.

2. The nozzle clogging detection device for the printhead according to claim 1, characterized in that, The preset time interval includes the jetting delay from when the printhead receives the jetting command to when the ink droplet is ejected, and the flight time required for the ink droplet to move to the center of the infrared laser path after being ejected from the nozzle.

3. The nozzle clogging detection device for the printhead according to claim 2, characterized in that, The infrared laser generating unit generates infrared lasers with wavelengths ranging from 750nm to 3000nm. The cross-section of the infrared laser is circular or rectangular. The diameter of the spot image formed by the infrared laser on the detection plane is larger than the maximum diameter of the ink droplets ejected from the nozzle.

4. The nozzle clogging detection device for a printhead according to any one of claims 1-3, characterized in that, The blockage detection unit is further configured to determine the light spot signal intensity difference between the first light spot signal and the pre-acquired second light spot signal, and compare the light spot signal intensity difference with a preset threshold, wherein: If the difference in light spot signal intensity is greater than the preset threshold, it is determined that an ink droplet has passed through the infrared laser path, so as to determine that the designated nozzle is in normal inkjet state; If the difference in light spot signal intensity is less than or equal to the preset threshold, the designated nozzle is determined to be in a blocked state. The second spot signal is the spot signal formed on the detection plane by the infrared laser when no ink droplet passes through the infrared laser path.

5. The nozzle clogging detection device for a printhead according to any one of claims 1-3, characterized in that, The blockage detection unit is further configured to acquire a corresponding spot image based on the first spot signal, and determine whether a dark spot appears in the spot image of the first spot signal. If no dark spot appears, the specified nozzle is determined to be in a blocked state. The dark spot is a local light intensity reduction area caused by the ink droplet passing through the infrared laser path in the spot image.

6. The nozzle clogging detection device for the printhead according to claim 5, characterized in that, The blockage detection unit is further configured to, when a dark spot appears in the spot image of the first spot signal, determine whether the designated nozzle has a spray direction deviation based on the position of the dark spot in the spot image and the preset effective detection area of ​​the spot image. The line connecting the projection point of the designated nozzle position on the detection plane and the center position of the spot image formed by the infrared laser on the detection plane is used as the reference axis. Two boundary rays with an angle not greater than a preset spray deviation angle extend from both sides of the reference axis. The effective detection area is the intersection of the area surrounded by the boundary rays and the projection area of ​​the spot image on the detection plane.

7. The nozzle clogging detection device for the printhead according to claim 5, characterized in that, The blockage detection unit is further configured to, when a dark spot appears in the spot image of the first spot signal, extract image features from the spot image and input the extracted image features into a pre-trained image recognition model to determine the direction and angle of ink droplet ejection, compare the ejection angle with a preset angle tolerance range, and determine that the specified nozzle has an ejection direction offset when the ejection angle exceeds the preset angle tolerance range; wherein, the image features include the center position coordinates, area parameters, and local grayscale decrease magnitude of the dark spot, the local grayscale decrease magnitude being the difference between the average pixel grayscale value of the dark spot and the average pixel grayscale value of the spot area other than the dark spot in the spot image, and the image recognition model is configured to output a value corresponding to the ink droplet ejection angle based on the image features in the spot image; When the image recognition model is pre-trained using training data, the training data includes image features of light spot images collected under different known spray angle conditions and corresponding ink droplet spray angle annotation information.

8. The nozzle clogging detection device for a printhead according to claim 5, characterized in that, The blockage detection unit is further configured to, when a dark spot appears in the light spot image of the first light spot signal, acquire the dark spot features of the light spot image, and determine whether the ink droplet corresponding to the dark spot is rotating based on the dark spot features; The dark spot features of the light spot image include: the roundness of the dark spot outline, the aspect ratio, the smoothness of the dark spot edge, and the skewness of the edge curve. The degree of skewing of the edge curve of the dark spot is obtained in the following way: Based on the coordinates of the edge curve of the dark spot extracted from the spot image, the edge curve is fitted, and the angle between the edge curve and the reference axis from the nozzle position to the center of the spot image is calculated. The angle is then used as a quantitative value of the skewness of the edge curve.

9. A printing device, characterized in that, include: Print head; The nozzle clogging detection device for the printhead according to any one of claims 1-8.

10. A method for detecting nozzle clogging in a printing device according to claim 9, characterized in that, Includes the following steps: The infrared laser generating unit and the spot detection unit are driven to translate along the nozzle array arrangement direction so that the infrared laser path is adapted to the target nozzle array. The infrared laser generating unit is controlled to emit infrared laser, such that the infrared laser path is located on a plane jointly determined by the array extension direction of the target nozzle array and the direction perpendicular to the array extension direction on the spray side, and the infrared laser path is parallel to the array extension direction. A spray command is issued to a designated nozzle in the target nozzle array; The first spot signal is obtained by the spot detection unit, and the first spot signal is obtained at a preset time interval after the spray command is issued; The working status of the designated nozzle is detected based on the first light spot signal.

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