An arrayed flying ink droplet visual scanning detection device based on scanning objective lens-galvanometer

Abstract

The present invention belongs to the field of new display-related technologies, and discloses an arrayed flying ink droplet visual scanning detection device based on a scanning objective lens-galvanometer, comprising a motion platform, a light source, a scanning objective lens, a two-dimensional scanning galvanometer, an imaging lens, and a camera. The optical axes of the light source, the scanning objective lens, and the two-dimensional scanning galvanometer are collinear, and the optical axis direction is the Z axis. A nozzle array is placed between the light source and the scanning objective lens: the light source illuminates the flying ink droplets, the row direction of the nozzle array is the X axis, and the running direction of the flying ink droplets is parallel to the Y axis; the scanning objective lens collects parallel light after passing through the flying ink droplets, and the light beams at different positions of the scanning objective lens have the same focal length; the two-dimensional scanning galvanometer is independently adjustable on the X axis and the Y axis; the imaging lens is used to magnify the light passing through the two-dimensional scanning galvanometer, and then be collected by the camera to complete the scanning imaging of the flying ink droplets. The above detection device designed by the present invention can avoid frequent movement of the nozzle array and achieve efficient and accurate measurement.

Description

Technical Field

[0001] The present invention belongs to the field of new display-related technologies, and more specifically, relates to an arrayed flying ink droplet visual scanning and detection device based on a scanning objective lens-galvanometer. Background Art

[0002] As one of the key development areas of this emerging industry, new display technologies aim to achieve the goal of low-cost production of ultra-high-resolution, large-size, lightweight, and flexible display devices. Traditional technologies such as vacuum evaporation present a number of challenges, including high energy consumption, significant material waste, and complex processes. In contrast, inkjet printing technology utilizes functional raw materials formulated into inks, which are then printed on demand onto rigid or flexible substrates to create organic or inorganic electronic devices. This technology offers advantages such as adaptability to large-scale production, strong material adaptability, high utilization rate, low cost, and green manufacturing, making it a key development direction for the future of the new display industry.

[0003] During the inkjet printing process, a range of abnormalities can occur, including nozzle blockage, deflected droplet flight, satellite droplets, tailing, and excessive droplet volume and velocity, due to process parameters such as the nozzle state in the nozzle array, ink properties, and the printing atmosphere. These abnormalities can cause defects such as missed drops, connections, scattering, and uneven ink volume when the droplets ultimately land on the substrate, thereby affecting the quality of the display. Furthermore, when inkjet printing on large substrates, it is often necessary to use multiple nozzles in the nozzle array simultaneously. Due to the large number of nozzles to be inspected, efficient detection of the ejected droplet parameters is necessary to ensure effective printing.

[0004] Existing inkjet printing droplet measurement methods can effectively complete the precise measurement of multiple parameters of ink droplets, but are limited by the low field of view caused by high magnification. Conventional vision systems can usually only capture ink droplet images of a single nozzle or a few adjacent nozzles at a time, and can only rely on the overall movement of the nozzle module to switch the nozzle to be observed, which makes it difficult to further improve the image acquisition efficiency. When the detection speed needs to be increased, the nozzle module with heavy mass, large size and large motion inertia will enter a high-frequency movement, stop, and movement cycle, which is easy to interfere with the flight stability of the ink droplets ejected by the nozzle module and affect the detection effect.

[0005] Therefore, designing a new detection device to achieve efficient and accurate measurement of nozzle arrays has become a key technical demand that needs to be urgently addressed in this field. Summary of the Invention

[0006] In response to the above defects or improvement needs of the prior art, the present invention provides an arrayed flying ink droplet visual scanning and detection device based on a scanning objective lens-galvanometer, the purpose of which is to achieve efficient and accurate measurement of the nozzle array.

[0007] To achieve the above objectives, according to one aspect of the present invention, a device for visual scanning and detecting arrayed flying ink droplets based on a scanning objective lens and a galvanometer is provided. The device comprises a motion platform, a light source, a scanning objective lens, a two-dimensional scanning galvanometer, an imaging lens, and a camera carried on the motion platform. The optical axes of the light source, the scanning objective lens, and the two-dimensional scanning galvanometer are collinear, and the direction of the optical axis is the Z axis. The area between the light source and the scanning objective lens is used to place a nozzle array.

[0008] The light source is used to form uniform parallel light to illuminate the flying ink droplets ejected from the nozzle array. The row direction of the nozzle array is the X axis. The running direction of the flying ink droplets is parallel to the Y axis. The X axis, Y axis and Z axis are orthogonal to each other.

[0009] The scanning objective lens is used to collect parallel light after passing through the flying ink droplets, and the light beams at different positions of the scanning objective lens have the same focal length;

[0010] The two-dimensional scanning galvanometer is independently adjustable along the X-axis and the Y-axis to receive light passing through different positions of the scanning objective lens. When scanning along the X-axis, it is used to scan flying ink droplets from different nozzles in the same row. When scanning along the Y-axis, it is used to scan the state changes of the same flying ink droplet at different heights.

[0011] The imaging lens is used to magnify the light passing through the two-dimensional scanning galvanometer mirror and then collect it by the camera to complete the scanning imaging of the flying ink droplets;

[0012] The motion platform is independently adjustable on the X-axis and the Z-axis.

[0013] In some embodiments, when the two-dimensional scanning galvanometer scans along the X axis, the scanning linear speed v of the two-dimensional scanning galvanometer is scan , the spacing Δl between adjacent nozzles in the same row of the nozzle array and the camera frame rate f satisfy: v scan =Δl*f, so that each frame image of the camera matches a nozzle.

[0014] In some embodiments, the ejection time of the first nozzle in the row to be scanned of the nozzle array is later than the start time of the movement of the two-dimensional scanning galvanometer mirror. The first nozzle starts ejecting after the two-dimensional scanning galvanometer mirror is in a uniform speed scanning state.

[0015] In some embodiments, for an image of any nozzle, the exposure time of the camera is later than the ejection time of the nozzle matched by the image, so that the captured flying ink droplets are located in the center area of ​​the field of view.

[0016] In some embodiments, the camera performs multiple flashes within the exposure time of each frame to record multiple ink droplet projection images of the same flying ink droplet at multiple consecutive moments.

[0017] In some embodiments, when entering the working state, the device sequentially scans different detection areas of the nozzle array. After the scanning of the previous detection area is completed, the nozzle array is moved to scan the next detection area.

[0018] When scanning any detection area: the device scans the current detection area line by line. When the scanning of the current row of nozzles is completed, the motion platform moves along the Z axis to scan the next row of nozzles. When scanning any row, the two-dimensional scanning galvanometer scans along the X axis to scan different nozzles in the same row.

[0019] In some embodiments, an image analysis module is further included for processing images captured by the camera, and the image analysis module includes:

[0020] The image classification unit is used to classify the images corresponding to the nozzle holes into categories including normal, spray deviation, scattered, jet, tail, out of range and no spray.

[0021] In some embodiments, the image analysis module further comprises:

[0022] The volume calculation unit is used to calculate the volume V of the flying ink droplet corresponding to any normal nozzle. In each image, N ink droplet projection images of the same flying ink droplet at different heights are collected through multiple exposures. The process of calculating the volume V includes:

[0023] Perform image enhancement processing on the current image to achieve denoising and improve resolution, and obtain a clear ink drop projection image; calculate the peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM) of each ink drop projection image in the current image before and after the image enhancement processing;

[0024] Calculate the clarity evaluation index G of each ink droplet projection image in the current image:

[0025] G = w·SSIM + (1-w)·PSNR

[0026] In the formula, w represents the set weight parameter, which takes values ​​in the range of [0,1];

[0027] Normalize the clarity evaluation index of all ink droplet projection images in the current image to obtain the normalized evaluation index ε i , i is the index of the ink droplet projection image, i∈{1,2,…,N};

[0028] Determine the weighting coefficient λ of each ink droplet projection image i :

[0029]

[0030] Discrete each clear ink droplet projection image into M slices with a thickness of △h in the height direction, and calculate the flying ink droplet volume V of the corresponding nozzle:

[0031]

[0032] Where, d j Represents the diameter of the cross section of the jth slice layer of the ink droplet of the i-th ink droplet projection image, j∈{1,2,…,M}.

[0033] In some embodiments, the image analysis module further comprises:

[0034] The flight speed calculation unit is used to calculate the representative speed of the flying ink droplet in the image corresponding to any normal nozzle. In each image, N ink droplet projection images of the same flying ink droplet at different heights are collected through multiple exposures. The process of calculating the speed S includes:

[0035] Perform image enhancement processing on the current image to achieve denoising and improve resolution, and obtain a clear ink drop projection image;

[0036] The clear ink drop projection image is segmented into ink drop contour lines, and the corresponding coordinates of the ink drop contour lines are determined in the camera image coordinate system R Cam The centroid coordinates of the N ink droplet contour lines under: (x1,z1), (x2,z2), (x3,z3),…, (x N ,z N ); where (x i ,z i ) is the centroid coordinate of the ink droplet contour of the i-th ink droplet projection image;

[0037] Determine the velocity weighting coefficient ρ of the projection images of two adjacent ink droplets i :

[0038]

[0039] Where λ i ,λ i+1 Respectively represent the weighting coefficients of the projection images of two adjacent ink droplets above and below;

[0040] Calculate the representative speed S of the flying ink droplet corresponding to the nozzle:

[0041]

[0042] Where Δt is the flash interval between multiple flash signals applied by the camera to the same ink droplet.

[0043] In some embodiments, the image analysis module further comprises:

[0044] The flight angle calculation unit is used to calculate the flight angle of a flying ink droplet in an image corresponding to any normal nozzle. In each image, N ink droplet projection images of the same flying ink droplet at different heights are collected through multiple exposures. The process of calculating the flight angle γ includes:

[0045] Perform image enhancement processing on the current image to achieve denoising and improve resolution, and obtain a clear ink drop projection image;

[0046] The clear ink drop projection image is segmented into ink drop contour lines, and the corresponding coordinates of the ink drop contour lines are determined in the camera image coordinate system R Cam The centroid coordinates of the N ink droplet contour lines under: (x1,z1), (x2,z2), (x3,z3),…, (x N ,z N ); where (x i ,z i ) is the centroid coordinate of the ink droplet contour of the i-th ink droplet projection image;

[0047] The flight trajectories of N ink droplets in the camera observation direction are fitted by polynomials;

[0048] The flight angle γ is calculated based on the fitted flight trajectory.

[0049] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0050] 1. The arrayed flying ink drop visual scanning detection device based on the scanning objective lens-galvanometer provided by the present invention ensures that the light beam maintains the focal position during the scanning process through the scanning objective lens. The light beams at different positions of the scanning objective lens will be focused on the same focal plane to form a flat imaging plane, and the focal length will not change due to the different angles of the light beam during the galvanometer scanning process, thereby ensuring clear imaging of the camera. Since the two-dimensional scanning galvanometer is independently adjustable on the X-axis and Y-axis, the motion platform is independently adjustable on the X-axis and Z-axis, and the nozzle array is independently adjustable on the X-axis and Z-axis, when detecting the flying ink drop area of ​​a certain row of nozzles, it is only necessary to adjust the two-dimensional scanning galvanometer to achieve clear imaging of the flying ink droplets of multiple nozzles; when it is necessary to scan the flying ink drop area of ​​the next row, it is only necessary to adjust the motion platform to align with the next row for scanning. When the motion platform is adjusted to the limit, the scanning area can also be changed by adjusting the nozzle array. Therefore, the flying ink drop visual scanning detection device designed by the present invention can avoid frequent movement of the nozzle array and achieve efficient and accurate measurement.

[0051] 2. The arrayed flying ink droplet visual scanning and detection device based on the scanning objective lens-galvanometer provided by the present invention introduces a scanning objective lens and a two-dimensional scanning galvanometer. The scanning galvanometer is independently adjustable on the X-axis and the Y-axis, and can continuously change the detection position within the imaging plane. Compared with conventional single-degree-of-freedom scanning, the present invention fixes the galvanometer in the X-axis direction. When the galvanometer is controlled to scan vertically along the ink droplet flight direction (corresponding to the Y-axis direction), the field of view of the detection device in the vertical direction can be expanded to observe the state changes of the ink droplets currently ejected from the nozzle at different heights. Since the galvanometer has a small inertia and a fast speed, the vertical scanning speed of the galvanometer along the ink droplet flight direction (corresponding to the Y-axis direction) can be set to be similar to the speed of the high-speed ink droplets, thereby realizing continuous imaging and detection of the same high-speed ink droplet within the entire vertical direction (corresponding to the Y-axis direction) scanning range, tracking its motion trajectory and morphological changes. Compared with conventional flying ink droplet detection schemes, this scheme makes up for the deficiency of only being able to detect at a fixed height and not being able to continuously track ink droplet state changes, thereby improving the reliability of the detection results.

[0052] 3. In a specific embodiment, a strategy for dividing the scanning detection area is proposed for the detection of arrayed flying ink droplets. The size of the scanning detection area is determined according to the rotatable amplitude of the two-dimensional scanning galvanometer and the arrangement of the nozzles, and each nozzle array is divided into multiple scanning detection areas. In a local scanning detection area, the target can be quickly scanned and observed by adjusting the deflection angle of the two-dimensional scanning galvanometer; when switching the local scanning detection area, the position of the entire visual detection device or / and the nozzle array can be adjusted by the mechanical auxiliary system. Compared with the conventional flying ink droplet detection scheme, due to the small volume and motion inertia of the two-dimensional scanning galvanometer component, the visual detection device can quickly switch the detection target within a large range by its rapid movement within a small range, which makes up for the lack of lengthy movement time when aiming at the next nozzle after detecting the current nozzle, and effectively improves the observation efficiency. Since the nozzle array does not need to move during the entire process of the visual detection device performing scanning and detection on a single local scanning detection area, the ink droplet ejection state is more stable, which is conducive to improving the image acquisition quality and thus increasing the detection accuracy.

[0053] 4. In a specific embodiment, a design is adopted in which multiple flashes are applied to the same ink droplet within a single exposure time of a camera, so that projection images of the flying ink droplet at multiple moments can be obtained in a single frame image, and the flash interval time is adjustable. This image acquisition method of the visual system can calculate the flying speed and angle of the ink droplet using a single frame image. Compared with the conventional detection scheme of collecting multiple frames of images at a certain interval and then comparing and calculating the flying ink droplet speed and angle, it significantly reduces the measurement time and saves detection steps.

[0054] 5. In a specific embodiment, the image corresponding to each nozzle is classified into categories such as normal, spray deviation, scatter, jet, tail, out of range, and no spray. Only the flying ink droplet images in the normal state are subjected to subsequent ink droplet parameter detection. This greatly reduces unnecessary image processing tasks, lowers computing overhead, effectively improves the ink droplet image processing speed, and facilitates the realization of online real-time detection.

[0055] 6. In a specific embodiment, the calculation of ink droplet volume involves first using a multiple-flash method to capture projection images of the same ink droplet at multiple moments. Based on this, the peak signal-to-noise ratio and structural similarity index of each projection image region before and after enhancement are calculated to determine the clarity evaluation index of the projection image and obtain the corresponding volume weighting coefficient. A nonlinear saturation activation function is then used to reduce the volume calculation weight of ink droplets corresponding to blurry image contours, thereby fully utilizing all projection image information identified as ink droplets in the image and improving the sampling rate and reliability of the volume measurement results.

[0056] 7. In a specific embodiment, regarding the calculation of ink droplet flight velocity, the velocity of the ink droplet at multiple moments before and after can be determined based on the positions and flash intervals of multiple ink droplet projections within a single-frame image. On this basis, the weight calculation method used to calculate the volume of the ink droplet is referenced to determine the velocity weighting coefficients corresponding to the two adjacent ink droplet projections above and below. The representative velocity of the ink droplet ejected from this nozzle at the current nozzle can be obtained. This method can obtain multiple velocities over a period of time and fully utilizes the information of all areas in the image identified as ink droplet images rather than only selecting a local image with clear parts to calculate the ink droplet velocity, thereby improving the sampling rate and accuracy of the velocity measurement.

[0057] 8. In a specific embodiment, regarding the calculation of the flight angle of the jetted ink droplet, compared with only using the two centroid coordinates of a single ink droplet at two moments before and after, the method of the present invention utilizes the projected centroid coordinate data of all ink droplets identified in the image, and at the same time uses a nonlinear model to fit the flight trajectory of the jetted ink droplet, thereby reducing the fitting error and improving the sampling rate and accuracy of angle detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 Schematic diagram of the structure of an arrayed flying ink droplet visual scanning and detection device based on a scanning objective lens-galvanometer mirror in one embodiment of the present invention;

[0059] Figure 2 3D diagram of the structure of an arrayed flying ink droplet visual scanning and detection device based on a scanning objective lens-galvanometer mirror in one embodiment of the present invention;

[0060] Figure 3 is a schematic structural diagram of a nozzle array in one embodiment of the present invention;

[0061] Figure 4 is a timing diagram of control signals of a detection device in one embodiment of the present invention;

[0062] Figure 5 1 is a schematic diagram of flying ink droplet segmentation in one embodiment of the present invention;

[0063] Figure 6 is a flowchart of a detection device in one embodiment of the present invention;

[0064] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0065] 10 is a camera, 11 is an imaging lens, 12 is a two-dimensional scanning galvanometer, 13 is a scanning objective lens, 14 is a telecentric light source, 20 is a nozzle array having multiple rectangular detection areas, 30 is a motion platform, 40 is a control module, and 50 is an ink collection device. DETAILED DESCRIPTION

[0066] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0067] like Figure 1 FIG. 1 is a schematic structural diagram of an arrayed flying ink droplet visual scanning and detection device based on a scanning objective lens-galvanometer mirror in one embodiment of the present invention. Figure 2 FIG. 1 is a three-dimensional structural diagram of an arrayed flying ink droplet visual scanning and detection device based on a scanning objective lens-galvanometer mirror in one embodiment of the present invention. Figure 3 FIG2 is a schematic diagram of the structure of the nozzle array in one embodiment of the present invention, wherein the X2 axis is parallel to the X axis, the Y2 axis is parallel to the Y axis, and the Z1 axis and the Z2 axis are parallel to the Z axis.

[0068] refer to Figures 1 to 3As shown, the detection device includes a motion platform 30 and a light source 14, a scanning objective lens 13, a two-dimensional scanning galvanometer 12, an imaging lens 11 and a camera 10 carried on the motion platform 30. The optical axes of the light source 14, the scanning objective lens 13 and the two-dimensional scanning galvanometer 12 are collinear, and the direction of the optical axis is the Z axis. The area between the light source 14 and the scanning objective lens 13 is used to place the nozzle array 20. The light source 14 is used to form uniform parallel light to illuminate the flying ink droplets 21 dripped from the nozzle array 20. The row direction of the nozzle array 20 is the X axis, and the flight direction of the ink droplets 21 is parallel to the Y axis. The X axis, Y axis and Z axis are orthogonal to each other. The scanning objective lens 13 is used to collect parallel light after passing through the flying ink droplets 21. The light beams at different positions of the scanning objective lens 13 have the same focal length. The two-dimensional scanning galvanometer 12 is independently adjustable along the X and Y axes to receive light from different positions of the scanning objective lens 13. When scanning along the X axis, it is used to scan flying ink droplets 21 from different nozzles in the same row. When scanning along the Y axis, it is used to scan the state changes of the same flying ink droplet at different heights or to adjust the detection of ink droplets at different heights. The imaging lens is used to magnify the light passing through the two-dimensional scanning galvanometer 12 before it is captured by the camera 10, completing the scanning and imaging of the flying ink droplets 21. The motion platform 30 is independently adjustable along the X and Z axes, and the nozzle array 20 is independently adjustable along the X and Z axes.

[0069] It can be understood that the system has a motion axis, a support arm and a control module. The motion axis, the support arm and the motion platform constitute a mechanical auxiliary module. Under the control of the control module 40, the various components are moved and positioned through the mechanical auxiliary module, wherein the support arm is used to suspend the nozzle array, and the nozzle array can be independently adjusted along the X-axis, Y-axis and Z-axis.

[0070] Specifically, the light source 14 can use a stroboscopic telecentric backlight light source, and adopt the backlight uniform illumination stroboscopic exposure method to realize the image acquisition and detection of the ink droplets ejected from the nozzle array. The light source module can use a pulsed laser, cooperate with an external modulator and a light source controller, and output a flash signal with a specified pulse width and time interval as needed.

[0071] The camera 10, lens 11, two-dimensional scanning galvanometer 12, scanning objective 13, and light source 14 are mounted on a motion platform 30 and can move with the motion platform 30. The motion platform 30 has two mutually perpendicular degrees of freedom of motion, X and Z. An ink collection device 50 is placed in the area between the light source 14 and the scanning objective 13 to collect flying ink droplets 21 ejected from the nozzles of the nozzle array 20. The size of the ink collection device 50 should be larger than the ejection range of the corresponding nozzle array 20 to be inspected. Specifically, the optical axes of the two-dimensional scanning galvanometer 12, scanning objective 13, and light source 14 are at the same height and collinear, and are several millimeters higher than the upper end surface of the ink collection device 50. When performing a scanning inspection, the nozzle array 20 is positioned above the ink collection device 50 by adjusting the support arm, and the optical axis of the visual inspection device is positioned below the nozzle and close to the lower surface of the nozzle, so as to collect ink droplets 21 in a relatively stable flying state.

[0072] The control module 40 is connected to the nozzle array 20, the camera 10, the two-dimensional scanning galvanometer 12, the light source 14 and the motion platform 30, and includes a motion controller, a synchronous trigger controller and a nozzle controller, wherein the nozzle controller is used to control the opening and closing of the nozzle, thereby controlling the nozzle injection and outputting an injection trigger signal to the synchronous trigger controller; the synchronous trigger controller receives the injection trigger signal and delays the triggering of the arrayed flying ink droplet visual detection device to work, thereby performing real-time scanning and detection of the flying ink droplets including volume, speed and angle, and switching to the next nozzle observation position after the scanning is completed; wherein the motion controller is used to control the position of the moving parts in each degree of freedom.

[0073] In practice, the flying ink droplets 21 ejected from the multiple nozzles within the nozzle array 20 are scanned and imaged to obtain information such as the droplet volume, velocity, and angle. Therefore, the camera 10 must be able to convert pixel coordinates to world coordinates for images captured by different targets. This necessitates calibration of the camera 10. For example, a high-precision calibration sphere is first placed at the working distance of the camera 10. The camera 10 is then controlled to capture images. The conversion relationship between pixel coordinates and world coordinates is obtained based on the pixel coordinates in the image and the size of the calibration sphere, completing the calibration of the camera 10.

[0074] In the present invention, a light source is set on one side of the arrayed flying ink droplet area to form a uniform backlight area to illuminate the flying ink droplets to be detected; a scanning objective lens is set on the other side of the arrayed flying ink droplet area, and the parallel light on the optical axis of the light source is collected by the scanning objective lens after passing through the flying ink droplets, ensuring that the light beam maintains the focal position during the scanning process. The light beams at different positions of the scanning objective lens will be focused on the same focal plane to form a flat imaging plane, and the focal length will not change due to the different angles of the light beam during the scanning process of the galvanometer, thereby ensuring clear imaging of the camera; a two-dimensional scanning galvanometer is set to make the light collected by the scanning objective lens pass through the galvanometer, which includes galvanometers that can be adjusted independently in the X and Y directions, and controls the direction along the nozzle array in one direction. The horizontal scanning (X) in the direction of the cloth and the vertical scanning (Y) along the flying direction of the ink droplets are controlled in the other direction to realize the rapid and precise control of the position of the light beam on the two-dimensional plane. The galvanometer is fixed in the Y direction and only scans in the horizontal direction (X) to continuously observe different nozzles. The galvanometer is fixed in the X direction and controls the vertical scanning of the galvanometer along the flying direction of the ink droplets (Y) to expand the field of view of the detection device in this direction and observe the state changes of the ink droplets ejected from the current nozzle at different heights. The imaging lens and industrial camera are arranged at the other end of the galvanometer, so that the light passes through the galvanometer and is magnified by the imaging lens before being collected by the camera to complete the scanning imaging. After image processing, the visual measurement of the flying ink droplets is completed.

[0075] This embodiment proposes to introduce a scanning objective lens and a two-dimensional scanning galvanometer during visual observation. The scanning objective lens ensures that the light beam maintains its focal position during the scanning process. The light beams at different positions of the scanning objective lens will be focused on the same focal plane to form a flat imaging plane. The focal length will not change due to the different angles of the light beam during the galvanometer scanning process, thereby ensuring clear imaging of the camera. When detecting the flying ink droplet area of ​​a small array of nozzles, there is no need to adjust the motion platform and / or nozzle position as a whole. Only the rotation angle of the two-dimensional scanning galvanometer needs to be adjusted to achieve clear imaging of flying ink droplets from multiple nozzles and efficient visual measurement of flying ink droplets.

[0076] During the inspection, the parameters of the camera 10, the two-dimensional scanning galvanometer 12 and the nozzle can be optimized. When the two-dimensional scanning galvanometer 12 scans along the X axis, the scanning linear speed v of the two-dimensional scanning galvanometer 12 is scan , the spacing Δl between adjacent nozzles in the same row of the nozzle array 20 and the frame rate f of the camera 10 satisfy: v scan=Δl*f, so that each frame of the camera 10 image matches a single nozzle. The first nozzle in the row to be scanned in the nozzle array 20 begins ejecting after the start of the two-dimensional scanning mirror 12. Once the two-dimensional scanning mirror 12 enters a uniform scanning state, the first nozzle begins ejecting. For any nozzle image, the camera 10's exposure time is delayed after the ejection time of the nozzle that matches the image, ensuring that the captured flying ink droplet is located in the center of the field of view. The camera 10 flashes multiple times within the exposure time of each frame to record multiple droplet projection images of the same flying ink droplet at multiple consecutive moments.

[0077] like Figure 4 The figure shows the timing diagram of the control signal of the detection device in one embodiment of the present invention. The motion platform 30 or the nozzle position is adjusted so that the nozzle row to be scanned is located in the imaging plane of the detection device. The galvanometer starts to move at time t2 before the nozzle starts to spray. After a period of acceleration, the galvanometer enters a linear uniform speed scanning state. The scanning linear speed v scan It is determined by the array nozzle spacing Δl and the camera 10 frame rate f, that is, v scan =Δl*f, so that each frame image of the camera 10 matches a nozzle; when the arrayed nozzles start to spray at a certain frequency according to the spray signal, the spray signal delay t1 allows the ink droplets collected by the camera 10 to enter the central area of ​​the field of view, triggering the camera 10 to start exposure of the image acquisition signal; within the exposure time t3 of each frame of the camera 10, the light source is triggered to perform two or more nanosecond flashes at a certain time interval, and the sum of the multiple flash pulse widths plus the pulse intervals is less than the exposure signal width of the camera 10, which is reflected in the same frame image. The projection image of the same ink droplet at multiple consecutive moments can continuously track the flight trajectory and shape of the ink droplet; set the nozzle spray frequency f j It is an integer M times the camera's 10 frame rate f, that is, f j =M*f, the ejection of the Mth ink droplet by the nozzle triggers the timing of the next camera 10 image acquisition delay t1, ensuring that the images of ink droplets ejected by the subsequent nozzles of the camera 10 are all located in the center area of ​​the camera 10's field of view. Among them, the camera 10 delay t1, ejection delay t2, exposure time t3, as well as the flash pulse width, flash pulse interval, and flash lag time are all independently adjustable in the control module. After completing the acquisition of ink droplet images ejected from all nozzles within the scanning range of the scanning objective lens, the galvanometer stops moving and prepares for the next round of scanning.

[0078] In a specific embodiment, when entering the working state, the device scans different detection areas of the nozzle array 20 in sequence. After the scanning of the current detection area is completed, the nozzle array 20 is moved to scan the next detection area. When scanning any detection area: the device scans the current detection area line by line. After the scanning of the current row of nozzles is completed, the motion platform 30 moves along the Z axis to scan the next row of nozzles. Among them, when scanning any row, the two-dimensional scanning galvanometer 12 scans along the X axis to scan different nozzles in the same row.

[0079] The arrayed flying ink droplet area corresponding to each nozzle array 20 is divided into multiple rectangular detection areas, wherein the maximum lateral size of each rectangular detection area is determined by the scanning range of the scanning objective lens, the number of nozzles L detected in each scanning can be selected according to actual needs, and the maximum longitudinal size is determined by the linear freedom stroke of the motion platform 30 or the motion stroke of the nozzle array 20; the flying ink droplets ejected by the array nozzles in each detection area are scanned and detected line by line, wherein, after completing the current nozzle row scan, the motion platform 30 or the nozzle is adjusted according to the coordinates of the currently detected nozzles and the nozzle coordinates of the next row of nozzles, so that the next row of nozzles in the detection area is located in the imaging plane of the detection device, and the next scan is performed until the ink droplet detection of all nozzles in the current local scanning detection area is completed; according to the nozzle coordinate array of the next area to be detected, the nozzle position is moved, and the scanning of the next detection area is performed until the ink droplet detection of all nozzles is completed.

[0080] Specifically, if Figure 6 As shown, the working process of the detection device is as follows:

[0081] (a) First, positioning: A control module is used to simultaneously cause the nozzles in the first row of the nozzle array in the area to be inspected to eject ink droplets. The nozzle array 20 is moved in the X and Y directions, and the motion platform 30 is moved in the X and Z directions. The ink droplets ejected from this row of nozzles are moved to the imaging plane of the visual inspection device. The galvanometer mirror begins to move, and after reaching a uniform speed, the camera observes the ink droplets ejected from the initial nozzles in the area to be inspected.

[0082] (b) The camera captures images and performs real-time visual detection of the ink droplets ejected by the current nozzle, including volume, speed, angle, and trajectory;

[0083] (c) Using a control module to make the galvanometer scan at a constant speed, when the galvanometer continuously moves to the next nozzle observation position; repeating step (b), sequentially traversing the remaining nozzles in the current scanning range, until the ink droplets ejected by all nozzles in the current scanning range are detected, and the galvanometer stops scanning;

[0084] (d) Repeat steps (a), (b), and (c) based on the nozzle coordinate array of the next row of nozzles in the area to be inspected, and traverse the remaining nozzles in the current area to be inspected in sequence until the ink droplets ejected by all nozzles in the current local scanning inspection area are detected.

[0085] (e) Repeat steps (a), (b), (c), and (d) according to the nozzle coordinate array of the next area to be inspected, and traverse all areas to be inspected in sequence until the ink droplets ejected by all nozzles are detected.

[0086] The synchronous scanning detection method for ink droplets ejected from a nozzle array designed by the present invention introduces a scanning objective lens and a two-dimensional scanning galvanometer. By adjusting the galvanometer in the horizontal (X) and vertical (Y) directions, the detection position can be continuously changed within the imaging plane. Compared with conventional single-degree-of-freedom scanning, the present invention fixes the galvanometer in the X direction. When controlling the galvanometer to scan vertically along the ink droplet flight direction (Y), the field of view of the detection device in the vertical direction can be expanded to observe the state changes of the ink droplets currently ejected from the nozzle at different heights. Due to the small inertia and high speed of the galvanometer, the vertical scanning speed of the galvanometer along the ink droplet flight direction (Y) can be set to be similar to the speed of the high-speed ink droplets, thereby achieving continuous imaging and detection of the same high-speed ink droplet within the entire vertical (Y) scanning range, tracking its motion trajectory and morphological changes. Compared with conventional flying ink droplet detection solutions, this method overcomes the shortcomings of only being able to detect at a fixed height and not being able to continuously track ink droplet state changes, thereby improving the reliability of the detection results.

[0087] The synchronous scanning detection method for ink droplets ejected from a nozzle array designed in the present invention adopts a design of applying multiple flashes to the same ink droplet within a single exposure time of a camera. Projected images of flying ink droplets at multiple moments can be obtained in a single frame picture, and the flash interval time is adjustable. This image acquisition method of the visual system can use a single frame image to calculate the flying speed and angle of the ink droplet. Compared with the conventional detection scheme of collecting multiple frames of images at a certain interval and then comparing and calculating the flying ink droplet speed and angle, it significantly reduces the measurement time and saves detection steps.

[0088] In one embodiment, the detection device further includes an image analysis module for processing images captured by the camera. The image analysis module includes an image classification unit for classifying images corresponding to the nozzle holes into types including normal, spray deviation, scattered points, jet, tailing, out of range, and no spray.

[0089] Specifically, within the camera's exposure time for each frame, each ejected ink droplet is subjected to two or more nanosecond flashes at a predetermined interval to capture images. This captures images of the same ink droplet at two or more preceding and following moments, with the top-to-bottom ink droplet images corresponding to the states of the ink droplet at the preceding and following flashes within the camera's single exposure time. Based on the images corresponding to each nozzle, the MobileNet classification algorithm is used to classify each nozzle image into categories such as normal, deflected spray, scattered, stream, tailing, out-of-range, and non-spray. For images of normal flying ink droplets, the Single Shot Multibox Detector (SSD) algorithm is used to perform target detection, outputting bounding boxes for all ink droplets in the image. The image regions within each bounding box are then subjected to deep learning-based image enhancement processing such as joint denoising, deblurring, and super-resolution, outputting denoised, high-resolution, and clear ink droplet images. That is, subsequent ink droplet target detection is performed only on the flying ink droplet images in normal state, and joint image enhancement is performed only on the image area within the bounding box detected as ink droplets. This greatly reduces unnecessary image processing tasks, lowers computing overhead, effectively improves the ink droplet image processing speed, and is conducive to realizing online real-time detection.

[0090] In one embodiment, the image analysis module further includes a volume calculation unit for calculating the volume V of a flying ink droplet in an image corresponding to any normal nozzle. In each image, N ink droplet projection images of the same flying ink droplet at different heights are collected through multiple exposures. The process of calculating the volume V includes:

[0091] Perform image enhancement processing on the current image to achieve denoising and improve resolution, and obtain a clear ink drop projection image; calculate the peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM) of each ink drop projection image in the current image before and after the image enhancement processing;

[0092] Calculate the clarity evaluation index G of each ink droplet projection image in the current image:

[0093] G = w·SSIM + (1-w)·PSNR

[0094] Where w represents the set weight parameter, which is used to balance the contribution of SSIM and PSNR, and takes values ​​in the range of [0,1].

[0095] Normalize the clarity evaluation index of all ink droplet projection images in the current image to obtain the normalized evaluation index ε i , i is the index of the ink droplet projection image, i∈{1,2,…,N};

[0096] Determine the weighting coefficient λ of each ink droplet projection image i :

[0097]

[0098] like Figure 5 As shown in the figure, each clear ink droplet projection image is discretized into M slices with a thickness of △h in the height direction, and the flying ink droplet volume V of the corresponding nozzle is calculated:

[0099]

[0100] Where, d j Represents the diameter of the cross section of the jth slice layer of the ink droplet of the i-th ink droplet projection image, j∈{1,2,…,M}.

[0101] This method uses a multiple-flash method to collect projection images of the same ink droplet at multiple moments. On this basis, the peak signal-to-noise ratio and structural similarity index of each projection image region before and after enhancement processing are calculated to calculate the clarity evaluation index of the projection image and obtain the corresponding volume weighting coefficient. A nonlinear saturation activation function is used to reduce the volume calculation weight of the ink droplet corresponding to the blurry image contour. This method fully utilizes the projection image information of all ink droplets in the image, thereby improving the sampling rate and reliability of the volume measurement results.

[0102] In one embodiment, the image analysis module further includes a flight speed calculation unit for calculating a representative speed of a flying ink droplet in an image corresponding to any normal nozzle. In each image, N ink droplet projection images of the same flying ink droplet at different heights are collected through multiple exposures. The process of calculating the speed S includes:

[0103] Perform image enhancement processing on the current image to achieve denoising and improve resolution, and obtain a clear ink drop projection image;

[0104] The clear ink drop projection image is segmented into ink drop contour lines, and the corresponding coordinates of the ink drop contour lines are determined in the camera image coordinate system R Cam The centroid coordinates of the N ink droplet contour lines under: (x1,z1), (x2,z2), (x3,z3),…, (x N ,z N ); where (x i ,z i ) is the centroid coordinate of the ink droplet contour of the i-th ink droplet projection image;

[0105] Determine the velocity weighting coefficient ρ of the projection images of two adjacent ink droplets i :

[0106]

[0107] Where λ i ,λ i+1 Respectively represent the weighting coefficients of the projection images of two adjacent ink droplets above and below;

[0108] Calculate the velocity S(i) of the flying ink droplets at different height positions in the image and the representative velocity S of the flying ink droplets corresponding to the nozzle:

[0109]

[0110] Where Δt is the flash interval between multiple flash signals applied by the camera to the same ink droplet.

[0111] Based on the positions and flash intervals of multiple ink droplet projections within a single-frame image, this method can derive the velocity of the ink droplet at multiple moments before and after. On this basis, the weight calculation method used to calculate the volume of the ink droplet is referenced to determine the velocity weighting coefficients corresponding to the projections of two adjacent ink droplets above and below. This method can derive the representative velocity of the ink droplet ejected from this nozzle at the current nozzle. This method can obtain multiple velocities over a period of time and fully utilizes all information in the image that is identified as an ink droplet image, rather than only selecting a local image with a clear portion to calculate the ink droplet velocity, thereby improving the sampling rate and accuracy of the velocity measurement.

[0112] In one embodiment, the image analysis module further includes a flight angle calculation unit for calculating the flight angle of a flying ink droplet in an image corresponding to any normal nozzle. In each image, N ink droplet projection images of the same flying ink droplet at different heights are collected through multiple exposures. The process of calculating the flight angle γ includes:

[0113] Perform image enhancement processing on the current image to achieve denoising and improve resolution, and obtain a clear ink drop projection image;

[0114] The clear ink drop projection image is segmented into ink drop contour lines, and the corresponding coordinates of the ink drop contour lines are determined in the camera image coordinate system R Cam The centroid coordinates of the N ink droplet contour lines under: (x1,z1), (x2,z2), (x3,z3),…, (x N ,z N ); where (x i ,z i ) is the centroid coordinate of the ink droplet contour of the i-th ink droplet projection image;

[0115] The flight trajectories of N ink droplets in the camera observation direction are fitted by polynomials. The fitting formula is:

[0116] f(x)=a n z n +a n-1 z n-1 +…a1z+a0

[0117] Where n is the order of the polynomial function;

[0118] Calculate the flight angle γ based on the fitted flight trajectory:

[0119] γ(x)=tan -1 f ′ (x).

[0120] In general, the efficient visual measurement method of array ink droplets based on scanning galvanometers proposed in the present invention, and the corresponding system for executing the method, can realize rapid scanning and accurate detection of arrayed ink droplets ejected from the nozzle array. Compared with the longer detection interval and fixed-point detection limitations of existing detection methods, it effectively expands the field of view, can realize continuous detection of the same ink droplet during flight, and improves the reliability of the detection results; at the same time, the detection method provided by the present invention can realize that the nozzle array does not need to move during the entire scanning detection process, making the ink droplet ejection state more stable, and at the same time adopts artificial intelligence-based image classification, ink droplet detection and image enhancement algorithms, which are conducive to improving image quality and reducing computing load, thereby increasing detection accuracy and speed. In addition, the detection method provided by the present invention can effectively realize high-precision measurement of multiple parameters such as the volume, speed, flight trajectory, and injection angle of arrayed flying ink droplets.

[0121] The technical features of the above embodiments can be combined in any manner. To simplify the description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. It should be noted that the phrases "in one embodiment", "for example", "and another example", etc. of the present invention are intended to illustrate the present invention and are not intended to limit the present invention.

[0122] The above embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. An arrayed flying ink drop visual scanning and detection device based on a scanning objective lens-galvanometer mirror, characterized in that: It includes a motion platform and a light source, a scanning objective lens, a two-dimensional scanning galvanometer, an imaging lens and a camera carried on the motion platform. The optical axes of the light source, the scanning objective lens and the two-dimensional scanning galvanometer are collinear, and the direction of the optical axis is the Z axis. The area between the light source and the scanning objective lens is used to place the nozzle array: The light source is used to form uniform parallel light to illuminate the flying ink droplets ejected from the nozzle array. The row direction of the nozzle array is the X axis. The running direction of the flying ink droplets is parallel to the Y axis. The X axis, Y axis and Z axis are orthogonal to each other. The scanning objective lens is used to collect parallel light after passing through the flying ink droplets, and the light beams at different positions of the scanning objective lens have the same focal length; The two-dimensional scanning galvanometer is independently adjustable along the X-axis and the Y-axis to receive light passing through different positions of the scanning objective lens. When scanning along the X-axis, it is used to scan flying ink droplets from different nozzles in the same row. When scanning along the Y-axis, it is used to scan the state changes of the same flying ink droplet at different heights. The imaging lens is used to magnify the light passing through the two-dimensional scanning galvanometer mirror and then collect it by the camera to complete the scanning imaging of the flying ink droplets; The motion platform is independently adjustable on the X-axis and the Z-axis.

2. The arrayed flying ink droplet visual scanning and detection device based on scanning objective lens and galvanometer according to claim 1, characterized in that: When the two-dimensional scanning galvanometer scans along the X axis, the scanning linear speed v of the two-dimensional scanning galvanometer is scan , the spacing Δl between adjacent nozzles in the same row of the nozzle array and the camera frame rate f satisfy: v scan =Δl*f, so that each frame image of the camera matches a nozzle.

3. The arrayed flying ink droplet visual scanning and detection device based on scanning objective lens and galvanometer as claimed in claim 1, characterized in that: The ejection time of the first ejection hole in the row to be scanned of the ejection hole array is later than the start time of the movement of the two-dimensional scanning galvanometer mirror. The first ejection hole starts ejecting after the two-dimensional scanning galvanometer mirror is in a uniform scanning state.

4. The arrayed flying ink droplet visual scanning and detection device based on scanning objective lens and galvanometer as claimed in claim 1, characterized in that: For the image of any nozzle, the exposure time of the camera is later than the ejection time of the nozzle matched by the image, so that the collected flying ink droplets are located in the center area of ​​the field of view.

5. The arrayed flying ink droplet visual scanning and detection device based on scanning objective lens and galvanometer as claimed in claim 1, characterized in that: The camera flashes multiple times within the exposure time of each frame to record multiple ink droplet projection images of the same flying ink droplet at multiple consecutive moments.

6. The arrayed flying ink droplet visual scanning and detection device based on scanning objective lens and galvanometer as claimed in claim 1, characterized in that: When entering the working state, the device scans different detection areas of the nozzle array in sequence. After the scanning of the current detection area is completed, the nozzle array is moved to realize the scanning of the next detection area; When scanning any detection area: the device scans the current detection area line by line. When the scanning of the current row of nozzles is completed, the motion platform moves along the Z axis to scan the next row of nozzles. When scanning any row, the two-dimensional scanning galvanometer scans along the X axis to scan different nozzles in the same row.

7. The arrayed flying ink droplet visual scanning and detection device based on scanning objective lens and galvanometer as claimed in claim 1, characterized in that: It also includes an image analysis module for processing the image captured by the camera, and the image analysis module includes: The image classification unit is used to classify the images corresponding to the nozzle holes into categories including normal, spray deviation, scattered, jet, tail, out of range and no spray.

8. The arrayed flying ink droplet visual scanning and detection device based on scanning objective lens and galvanometer according to claim 7, characterized in that: The image analysis module also includes: The volume calculation unit is used to calculate the volume V of the flying ink droplet corresponding to any normal nozzle. In each image, N ink droplet projection images of the same flying ink droplet at different heights are collected through multiple exposures. The process of calculating the volume V includes: Perform image enhancement processing on the current image to achieve denoising and improve resolution, and obtain a clear ink drop projection image; calculate the peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM) of each ink drop projection image in the current image before and after the image enhancement processing; Calculate the clarity evaluation index G of each ink droplet projection image in the current image: G = w·SSIM + (1-w)·PSNR In the formula, w represents the set weight parameter, which takes values ​​in the range of [0,1]; Normalize the clarity evaluation index of all ink droplet projection images in the current image to obtain the normalized evaluation index ε i , i is the index of the ink droplet projection image, i∈{1,2,…,N}; Determine the weighting coefficient λ of each ink droplet projection image i : Discrete each clear ink droplet projection image into M slices with a thickness of △h in the height direction, and calculate the flying ink droplet volume V of the corresponding nozzle: Where, d j Represents the diameter of the cross section of the jth slice layer of the ink droplet of the i-th ink droplet projection image, j∈{1,2,…,M}.

9. The arrayed flying ink droplet visual scanning and detection device based on scanning objective lens and galvanometer according to claim 7, characterized in that: The image analysis module also includes: The flight speed calculation unit is used to calculate the representative speed of the flying ink droplet in the image corresponding to any normal nozzle. In each image, N ink droplet projection images of the same flying ink droplet at different heights are collected through multiple exposures. The process of calculating the speed S includes: Perform image enhancement processing on the current image to achieve denoising and improve resolution, and obtain a clear ink drop projection image; The clear ink drop projection image is segmented into ink drop contour lines, and the corresponding coordinates of the ink drop contour lines are determined in the camera image coordinate system R Cam The centroid coordinates of the N ink droplet contour lines under: (x1,z1), (x2,z2), (x3,z3),…, (x N ,z N ); where (x i ,z i ) is the centroid coordinate of the ink droplet contour of the i-th ink droplet projection image; Determine the velocity weighting coefficient ρ of the projection images of two adjacent ink droplets i : Where λ i ,λ i+1 Respectively represent the weighting coefficients of the projection images of two adjacent ink droplets above and below; Calculate the representative speed S of the flying ink droplet corresponding to the nozzle: Where Δt is the flash interval between multiple flash signals applied by the camera to the same ink droplet.

10. The arrayed flying ink drop visual scanning and detection device based on scanning objective lens and galvanometer according to claim 7, characterized in that: The image analysis module also includes: The flight angle calculation unit is used to calculate the flight angle of a flying ink droplet in an image corresponding to any normal nozzle. In each image, N ink droplet projection images of the same flying ink droplet at different heights are collected through multiple exposures. The process of calculating the flight angle γ includes: Perform image enhancement processing on the current image to achieve denoising and improve resolution, and obtain a clear ink drop projection image; The clear ink drop projection image is segmented into ink drop contour lines, and the corresponding coordinates of the ink drop contour lines are determined in the camera image coordinate system R Cam The centroid coordinates of the N ink droplet contour lines under: (x1,z1), (x2,z2), (x3,z3),…, (x N ,z N ); where (x i ,z i ) is the centroid coordinate of the ink droplet contour of the i-th ink droplet projection image; The flight trajectories of N ink droplets in the camera observation direction are fitted by polynomials; The flight angle γ is calculated based on the fitted flight trajectory.

Images