A method and apparatus for positioning a printing device

Abstract

The application discloses a positioning printing device and method, which is used for positioning printing on the surface of a to-be-printed object. The positioning printing device comprises a conveying unit, an image collecting unit, a position detecting unit, a processing unit and a printing unit. The image collecting unit continuously collects surface images of the to-be-printed object in the relative motion process of the to-be-printed object. The position detecting unit detects the position of the to-be-printed object relative to the image collecting unit when each surface image is collected. The processing unit establishes the corresponding relationship between each surface image and the corresponding position, extracts the relief features of the surface of the to-be-printed object from the surface image, and determines the printing position of the target printing pattern according to the relief features and the corresponding relationship, and generates printing control data. The printing unit prints on the surface of the to-be-printed object according to the printing control data, so that the target printing pattern corresponds to the relief features of the surface of the to-be-printed object. Therefore, the accurate registration of the printing pattern and the pile surface can be realized on the to-be-printed object with the high-low relief three-dimensional pile surface texture.

Description

Technical Field

[0001] This invention relates to the field of inkjet printing, and in particular to a positioning printing device and method. Background Technology

[0002] Digital inkjet printing technology can spray ink directly onto the surface of a substrate according to a predetermined pattern to form a design. It has the advantages of convenient pattern changing and rich color expression, and is now widely used in surface printing of textiles such as carpets.

[0003] Some carpets are woven using a combination of high-pile and low-pile, loop pile and cut pile techniques, resulting in a surface that is not flat but rather features a three-dimensional pile texture with varying heights and depths. When printing patterns on these carpets, the printed pattern needs to correspond in position to the existing three-dimensional pile texture on the carpet surface, so that the pattern is distributed along the undulations of the pile, thus achieving a matching pattern between the pattern and the pile.

[0004] However, when using existing digital printing technology to print patterns on carpets with three-dimensional pile textures, it is often difficult to keep the printed pattern in the same position as the existing three-dimensional pile texture of the carpet. After printing, the pattern is easily misaligned relative to the pile texture, making it difficult to meet the requirements for pattern matching. Summary of the Invention

[0005] To address the problem of misalignment between the printed pattern and the three-dimensional texture of objects such as carpets with velvety surfaces when printing using existing technologies, this invention addresses this issue. During the relative movement of the object to be printed and the image acquisition unit, the image acquisition unit continuously acquires surface images of the object, aligning each surface image with the object's position at the time of acquisition. The invention then extracts the surface undulation features from these images and, based on these features and the correspondence between the images and positions, determines the printing position of the target printed pattern on the object's surface. Printing control data is then generated accordingly. When the object's surface moves to the printing unit, printing is performed according to the printing control data. This achieves positioning printing where the printed pattern corresponds to the surface undulation features of the object, reducing misalignment between the printed pattern and the three-dimensional texture.

[0006] To achieve the above objectives, the present invention provides a positioning printing device for positioning printing on the surface of an object to be printed, comprising:

[0007] The conveyor unit is used to carry and transport the objects to be printed.

[0008] An image acquisition unit, positioned above the conveying unit, is used to continuously acquire surface images of the object to be printed during the relative movement between the image acquisition unit and the object to be printed.

[0009] The position detection unit is used to detect the position of the object to be printed relative to the image acquisition unit when acquiring images of each surface;

[0010] The processing unit, communicatively connected to both the image acquisition unit and the position detection unit, establishes the correspondence between each surface image and the position detected by the position detection unit. It extracts the undulation features of the surface of the object to be printed from the surface images and determines the printing position of the target printed pattern on the surface of the object based on these undulation features and the corresponding relationship, thereby generating printing control data.

[0011] The printing unit, which is communicatively connected to the processing unit, is used to print on the surface of the object to be printed according to printing control data when the surface of the object to be printed moves to the printing unit along with the conveying unit.

[0012] The printing position is the position where the target printed pattern corresponds to the undulation features of the surface of the object to be printed.

[0013] In some embodiments, the conveying unit includes a continuously extending conveyor belt, and the object to be printed is carried on the upper surface of the conveyor belt; an image acquisition unit and a printing unit are arranged at intervals along the conveying direction of the conveyor belt, with the image acquisition unit located upstream of the printing unit; the image acquisition unit is capable of reciprocating relative to the conveyor belt along the width direction of the object to be printed, the width direction intersecting the conveying direction, and the relative motion includes the reciprocating movement of the image acquisition unit along the width direction and the movement of the object to be printed along the conveying direction with the conveyor belt.

[0014] In some embodiments, the image acquisition unit includes a line scan imaging unit, which acquires surface images of the object to be printed row by row during relative motion, and stitches the successively acquired row images together into a two-dimensional image along the direction of relative motion; the positioning printing device also includes an illumination unit, which is positioned toward the object to be printed and is used to form a linear illumination area on the rows acquired by the line scan imaging unit.

[0015] In some embodiments, the line scan imaging unit includes at least one photosensitive component, each photosensitive component including a plurality of photoelectric conversion elements arranged in a row along the same straight line, the row of photoelectric conversion elements forming a linear photosensitive array; when there are multiple photosensitive components, the multiple photosensitive components are arranged end to end along the width direction of the object to be printed.

[0016] In some embodiments, the linear photosensitive array described above is a charge-coupled device linear array or a complementary metal-oxide-semiconductor linear array.

[0017] In some embodiments, the illumination unit includes a line light source for emitting linear illumination light, the optical path of which coincides with or is parallel to the imaging optical path of the image acquisition unit; the illumination unit also includes a beam splitter located on the imaging optical path, the linear illumination light being deflected by the beam splitter and directed along the imaging optical path toward the object to be printed.

[0018] In some embodiments, the beam-splitting element is a beam splitter or a semi-transparent, semi-reflective mirror.

[0019] In other embodiments, the image acquisition unit may not be limited to the line scan imaging unit described above. For example, the image acquisition unit may include an area scan camera, which acquires images of the surface of the object to be printed line by line along a strip-shaped region of interest extending in a row, and stitches the images acquired in succession into a two-dimensional image; or the image acquisition unit may include a contact image sensor, which acquires surface images of the surface of the object to be printed line by line.

[0020] In some embodiments, the positioning printing device further includes a scanning main beam and a scanning head frame; the scanning main beam spans across the conveyor belt and extends along the width direction, the scanning head frame is slidably mounted on the scanning main beam along the width direction via a linear guide pair, and the image acquisition unit is fixed to the scanning head frame; the linear guide pair includes two linear guide rails extending along the width direction and spaced apart from each other, and the scanning head frame straddles the two linear guide rails; the positioning printing device further includes a servo motor, a reducer, a coupling, a driving synchronous pulley, a driven synchronous pulley, and a synchronous belt, the output shaft of the servo motor is connected to the driving synchronous pulley via the reducer and the coupling, the synchronous belt is tensioned between the driving synchronous pulley and the driven synchronous pulley, the scanning head frame is fixedly connected to the synchronous belt so that the servo motor drives the scanning head frame to reciprocate along the scanning main beam via the synchronous belt; a magnetic scale is provided on the scanning main beam along the width direction, a reading head is provided on the scanning head frame opposite to the magnetic scale, and an encoder is provided on the conveyor unit for detecting the displacement of the object to be printed along the conveying direction, the magnetic scale, the reading head, and the encoder together constitute a position detection unit.

[0021] The present invention also provides a positioning printing method, applied to the above-mentioned positioning printing device, comprising the following steps:

[0022] This creates a relative motion between the object to be printed and the image acquisition unit.

[0023] During the relative motion, the image acquisition unit continuously acquires surface images of the object to be printed, and each surface image corresponds to the position of the object to be printed relative to the image acquisition unit when the surface image is acquired;

[0024] Extract the surface undulation features of the object to be printed from the surface image;

[0025] The positional correspondence between the target printing pattern and the surface of the object to be printed is determined based on the undulation characteristics, and printing control data is generated by combining the correspondence between the surface images and the positions.

[0026] The surface of the object to be printed is moved to the printing unit, and the printing unit prints the pattern on the surface of the object according to the printing control data, so that the target print pattern corresponds to the undulation characteristics of the surface of the object to be printed.

[0027] In some embodiments, the step of continuously acquiring surface images of an object to be printed includes: acquiring surface images of the object to be printed row by row through a line scanning imaging unit during relative motion, and stitching the successively acquired row images into a two-dimensional image along the direction of relative motion; while acquiring each row image, projecting linear illumination light onto the row being acquired on the object to be printed through an illumination unit, wherein the illumination area formed by the linear illumination light corresponds to the row being acquired.

[0028] In some embodiments, the step of generating print control data includes: comparing the extracted undulation features with a pre-defined reference texture to obtain the overall positional deviation and local deformation of the actual texture of the surface of the object to be printed relative to the reference texture; translating, rotating, scaling and locally deforming the target printing pattern according to the overall positional deviation and local deformation to obtain a corrected pattern corresponding to the undulation features of the surface of the object to be printed; and generating print control data from the corrected pattern.

[0029] In some embodiments, the image acquisition unit and the printing unit are arranged at intervals along the transport direction of the object to be printed, and the image acquisition unit is located upstream of the printing unit; the transport displacement of the object to be printed along the transport direction is detected, and the time when the area to be printed on the surface of the object to be printed reaches the printing unit is determined based on the distance between the image acquisition unit and the printing unit along the transport direction and the transport displacement; when the area to be printed reaches the printing unit, the printing unit prints the area to be printed according to the printing control data.

[0030] Compared with the above-mentioned background technology, the present invention can achieve at least the following technical effects:

[0031] The actual position of the three-dimensional texture of the object to be printed on its surface is a prerequisite for the printed pattern to match the three-dimensional texture. When using existing printing technology, the printed pattern is often sprayed at a pre-agreed position, which does not correspond to the actual position of the three-dimensional texture on the surface of the object to be printed. Therefore, the printed pattern is prone to misalignment relative to the three-dimensional texture.

[0032] In this invention, a relative movement occurs between the image acquisition unit and the object to be printed. During this process, the image acquisition unit continuously acquires surface images of the object to be printed. The position detection unit detects the position of the object to be printed relative to the image acquisition unit when each surface image is acquired. Based on this, the processing unit establishes a correspondence between each surface image and its corresponding position. Thus, each acquired surface image reflects both the actual state of the surface of the object to be printed along the direction of relative movement and its corresponding position on the object, thereby providing an image associated with the actual position for subsequent determination of the printing position.

[0033] Furthermore, the processing unit extracts the surface undulation features of the object to be printed from the aforementioned surface image. Specifically, it extracts the actual distribution of three-dimensional textures such as pile, loop pile, and cut pile on the surface of the object, rather than relying on the outer edges, corners, or additional markings of the object. Subsequently, based on the extracted undulation features and the correspondence between the surface image and the position, the processing unit determines the printing position of the target printed pattern on the surface of the object, ensuring that the printing position falls corresponding to the surface undulation features, and generates printing control data accordingly.

[0034] When the surface of the object to be printed moves to the printing unit along with the conveying unit, the printing unit prints the pattern on the surface of the object according to the aforementioned printing control data. The printed pattern falls on the position corresponding to the three-dimensional texture of the object itself. Thus, the printed pattern is distributed according to the actual distribution of the surface undulations of the object, rather than being printed at a preset position, thereby reducing the degree of misalignment of the printed pattern relative to the three-dimensional texture of the object and improving the matching effect. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0036] Figure 1 This is an isometric view of the positioning printing device provided in an embodiment of the present invention; Figure 2 This is a front view of the positioning printing device provided in an embodiment of the present invention; Figure 3 This is a side view of the positioning printing device provided in an embodiment of the present invention; Figure 4 This is a top view of the positioning printing device provided in an embodiment of the present invention; Figure 5This is a schematic diagram of the inkjet printing apparatus provided in an embodiment of the present invention; Figure 6 This is a front view of the printing apparatus provided in an embodiment of the present invention; Figure 7 This is a top view of the printing apparatus provided in an embodiment of the present invention; Figure 8 This is a bottom view of the printing apparatus provided in an embodiment of the present invention; Figure 9 This is a front view of the scanned main beam provided in an embodiment of the present invention; Figure 10 for Figure 9 Enlarged view of section A; Figure 11 for Figure 9 Enlarged view of section B; Figure 12 This is an isometric view of the scanning head frame provided in an embodiment of the present invention; Figure 13 This is a front view of the scanning head frame provided in an embodiment of the present invention; Figure 14 This is a side view of the scanning head frame provided in an embodiment of the present invention; Figure 15 This is a bottom view of the scanning head frame provided in an embodiment of the present invention; Figure 16 for Figure 12 Enlarged view of section C; Figure 17 This is a schematic diagram of a camera mounting plate provided in an embodiment of the present invention; Figure 18 This is a schematic flowchart of the positioning printing method provided in an embodiment of the present invention.

[0037] Explanation of reference numerals in the attached figures: 10. Conveying unit; 20. Printing unit; 21. First printing module; 211. Valve-controlled jet head; 22. Second printing module; 2121. On-demand inkjet head; 23. Supply module; 231. First liquid storage container; 232. First liquid supply pipe; 233. First control valve; 234. Second liquid storage container; 235. Second liquid supply pipe; 236. Second control valve; 30. Scanning main beam; 31. Guide rail pair; 40. Scanning head frame; 41. Image acquisition unit; 42. Illumination unit; 43. Reading head; 44. Slider fixing plate; 45. First side plate; 46. Second side plate; 47. Camera mounting plate; 471. First waist hole; 472. Second waist hole; 48. Camera connector; 491. First lamp source connecting plate; 492. Second lamp source connecting plate; 51. Servo motor; 52. Reducer; 53. Coupling; 54. Driving synchronous pulley; 55. Driven synchronous pulley; 56. Synchronous belt; 60. Fixing component; 61. Toothed belt clamp; 62. Toothed belt clamp seat; 63. Adjusting fastener; 64. Adjusting screw; 71. Proximity switch; 72. Limit switch; 73. Mechanical limit component; 74. Buffer block; 81. Silent cable chain; 82. Cable chain support assembly; 83. Camera cable clamp; Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] To enable those skilled in the art to better understand the solution of this invention, the following is combined with... Figures 1 to 18 The positioning printing apparatus and positioning printing method provided in the embodiments of the present invention will be described in further detail below. It should be noted that the conveying direction in the following text refers to the direction in which the object to be printed travels with the conveying unit 10; the width direction refers to the direction that intersects with the conveying direction and is approximately parallel to the surface of the object to be printed; upstream and downstream are based on the order in which the object to be printed travels along the conveying direction.

[0040] This invention provides a positioning printing device for positioning printing on the surface of an object to be printed. In this embodiment, a carpet is used as an example. This carpet is woven using a combination of high-pile and low-pile, loop pile and cut pile techniques. Its surface is not flat, but rather features a three-dimensional pile texture with alternating pile surfaces of different heights and shapes. The actual distribution of these three-dimensional pile surfaces on the surface of the object to be printed constitutes the undulating feature referred to below, which is the benchmark for measuring whether the printed pattern matches the pile surface, i.e., whether pattern matching can be achieved. It is understood that the object to be printed is not limited to the carpet mentioned above; it can also be blankets, velvet, cut loop pile fabrics, jacquard fabrics, or other textiles or sheet-like objects with three-dimensional textures on their surfaces. Any object that requires the printed pattern to correspond positionally with its own three-dimensional texture can be used as the object to be printed in this embodiment, and will not be elaborated further below.

[0041] like Figures 1 to 4As shown, the positioning printing device mainly includes a conveying unit 10, an image acquisition unit 41, a position detection unit, a processing unit, and a printing unit 20. The conveying unit 10 carries and conveys the object to be printed. The image acquisition unit 41 is positioned above the conveying unit 10 and continuously acquires surface images of the object during relative movement between the image acquisition unit 41 and the object. The position detection unit detects the position of the object relative to the image acquisition unit 41 when each surface image is acquired. The processing unit is communicatively connected to both the image acquisition unit 41 and the position detection unit, establishing a correspondence between each surface image and the position detected by the position detection unit. It extracts the surface undulation features of the object from the surface images and determines the printing position of the target printing pattern on the surface of the object based on the undulation features and the aforementioned correspondence, thereby generating printing control data. The printing unit 20 is communicatively connected to the processing unit and prints on the surface of the object according to the printing control data when the surface of the object moves to the printing unit 20 with the conveying unit 10. The printing position is the position where the target printing pattern corresponds to the undulation features of the object's surface.

[0042] Specifically, such as Figures 1 to 4 As shown, the positioning printing device also includes a scanning main beam 30 spanning above the conveying unit 10, extending along the width direction. A scanning head frame 40 is slidably mounted on the scanning main beam 30 along the width direction via a guide rail pair 31. The image acquisition unit 41 and the illumination unit 42 are both mounted on the scanning head frame 40, allowing them to reciprocate along the width direction together with the scanning head frame 40. The printing unit 20 is located downstream of the scanning main beam 30 along the conveying direction and spans the conveying unit 10 as a whole. The printing unit 20 includes a printing device and an isolation cover covering the printing device. The printing device is located inside the isolation cover and above the conveying unit 10, with the printing side of the printing device facing the conveying unit 10. The lower part of the isolation cover forms a printing channel for the conveyor belt and the object to be printed to pass through. The outer side of the isolation cover is provided with an openable door panel for the installation, inspection, cleaning, and component replacement of the printing device.

[0043] It should be noted that, Figures 1 to 4 This mainly shows the overall structure of the positioning printing device and the external shape of the isolation cover. Most of the components of the printing device are located inside the isolation cover and therefore are not shown in the main display. Figures 1 to 4 They are shown one by one in the middle. Figures 5 to 8 The main focus is on the internal structure of the printing device, showing the first printing module 21, the second printing module 22, and the supply module 23 for easy observation. Figures 5 to 8 The isolation shield is omitted.

[0044] Please see Figures 5 to 8In this embodiment, the printing device 21 adopts a dual-mode digital printing structure, including a first printing module 21, a second printing module 22, and a supply module 23. The first printing module 21 uses a valve-controlled jet head 211 to control the discharge of a first coloring medium under pressure. After leaving the jet end, the first coloring medium moves into the thicker textured layer. The second printing module 22 uses an on-demand inkjet head 221 to form droplets according to printing control data, and controls the droplet formation time and ejection position to form pattern outlines and details in the low-textured area.

[0045] The first printing module 21 includes at least one printing unit. Each printing unit includes a fluid distribution seat and multiple valve-controlled nozzles 211, which are spaced apart from each other in the fluid distribution seat. The fluid distribution seat has a common liquid supply channel with an inlet and multiple outlets, each outlet communicating with a corresponding valve-controlled nozzle 211. The valve-controlled nozzle 211 has a valve for opening or closing the fluid passage. When the valve is open, the pressurized first coloring medium is ejected through the common liquid supply channel and the valve-controlled nozzle 211; when the valve is closed, the ejection stops.

[0046] The second printing module 22 includes at least one on-demand inkjet head 221. The on-demand inkjet head 221 includes a drive unit, a nozzle array, and an ink supply channel. The ink supply channel is connected to the nozzle array, and the drive unit is correspondingly positioned to the nozzle array. After receiving print control data, the drive unit changes the volume or pressure of the corresponding ejection chamber, causing the second coloring medium to form droplets from the corresponding nozzle and be ejected. The nozzle array may include a single row of nozzles or multiple rows of nozzles staggered together; multiple on-demand inkjet heads 221 may be connected or staggered along the width direction.

[0047] The supply module 23 includes a first supply unit and a second supply unit separated from each other. The first supply unit includes a first liquid storage container 231, a first liquid supply pipe 232, and a first control valve 233. One end of the first liquid supply pipe 232 is connected to the first liquid storage container 231, and the other end is connected to a common liquid supply channel. The first control valve 233 is disposed on the first liquid supply pipe 232. The second supply unit includes a second liquid storage container 234, a second liquid supply pipe 235, and a second control valve 236. One end of the second liquid supply pipe 235 is connected to the second liquid storage container 234, and the other end is connected to the ink supply channel of the on-demand inkjet head 221. The second control valve 236 is disposed on the second liquid supply pipe 235.

[0048] A filter element can be installed at the outlet of the first liquid storage container 231. The first liquid storage container 231 can also be connected to a pressure supply component to maintain the first coloring medium under pressure suitable for ejection from the valve-controlled nozzle 211. A filter element and an venting component can be installed on the second liquid supply pipe 235. The filter element is used to intercept impurities that may clog the nozzle, and the venting component is used to expel air bubbles in the second coloring medium. The first control valve 233 and the second control valve 236 respectively control the on / off state or flow rate of the two supply paths.

[0049] The printing device 21 may further include a printhead mounting plate, which is fixed to the support frame of the printing device 21. The first printing module 21 and the second printing module 22 are fixed to the printhead mounting plate at intervals. The ejection ends of the valve-controlled printhead 211 and the on-demand inkjet head 221 are both located on the side of the printhead mounting plate facing the object to be printed. The first printing module 21 and the second printing module 22 can be arranged front and back along the conveying direction, or side by side along the width direction. When the two types of printheads have different applicable ejection distances, the ejection ends of the two types of printheads can be located at different heights and maintain corresponding ejection distances to the surface of the object to be printed.

[0050] The first and second coloring media can have the same hue or different hues; they can use the same type of coloring components or use color pastes and inks suitable for valve-controlled inkjet head 211 and on-demand inkjet head 221 respectively. For the same pattern spanning high-textured and low-textured areas, the first printing module 21 and the second printing module 22 respectively spray the corresponding coloring media in the corresponding areas, so that the pattern is continuously distributed between areas with different textured heights.

[0051] Furthermore, such as Figure 1 and Figure 3 As shown, the conveying unit 10 includes a continuously extending conveyor belt and an active roller and a driven roller for tensioning the conveyor belt. The object to be printed is laid flat on the upper surface of the conveyor belt. The active roller is driven by a conveyor motor to drive the conveyor belt to rotate in a cycle, so that the object to be printed passes sequentially along the conveying direction through the acquisition station where the image acquisition unit 41 is located and the printing station where the printing unit 20 is located.

[0052] It should be explained that the positioning printing achieved by this invention adopts a sequence of first capturing and then printing. That is, the surface image and position of a certain area are recorded at the capture station, and the area is then moved to the printing station to be printed. If the area slips or sways relative to the conveyor belt during this process, the previously established correspondence between the image and the position will no longer be accurate. To address this, in some embodiments, the upper surface of the conveyor belt is provided with an anti-slip structure for stably supporting the object to be printed.

[0053] As an alternative implementation, the upper surface of the conveyor belt is covered with an adhesive layer, such as a reusable guide belt adhesive layer, which is lightly adhered and fixed after the object to be printed is laid on the adhesive layer. As another optional implementation, the conveyor belt is provided with multiple adsorption holes, and a negative pressure chamber is provided below the conveyor belt in the section between the collection station and the printing station. The negative pressure chamber is drawn by the fan to form a negative pressure at each adsorption hole, adsorbing the object to be printed onto the surface of the conveyor belt. As another optional implementation, the upper surface of the conveyor belt is provided with guide belt needles, which are needle-like objects installed on the surface of the guide belt. The guide belt needles are evenly arranged along the width direction and the direction of movement of the object to be printed. After the object to be printed is laid on the guide belt, it is firmly fixed by the needles to prevent the object to be printed from slipping, shifting or deforming during the conveying process.

[0054] As another optional implementation, a pressure roller is installed upstream of the acquisition station. This roller presses the object to be printed firmly onto the conveyor belt, expelling air between the object and the belt and eliminating wrinkles. The aforementioned anti-slip structures can be used individually or in combination. In this way, the object to be printed remains relatively stationary with respect to the conveyor belt throughout the entire process from acquisition to printing. The displacement of the conveyor belt represents the displacement of the object, thus ensuring that the correspondence between the image and position established during the acquisition phase remains valid during the printing phase.

[0055] Furthermore, such as Figure 3 and Figure 4 As shown, the image acquisition unit 41 and the printing unit 20 are arranged at intervals along the conveyor belt's transport direction. The image acquisition unit 41 is located upstream of the printing unit 20, and there is a preset distance between them along the transport direction. In this way, the object to be printed first completes surface image acquisition at the acquisition station. The processing unit uses the time it takes to travel from the acquisition station to the printing station to complete the extraction of undulation features and the generation of printing control data. The object to be printed then arrives at the printing station to receive the print. Acquisition and printing are sequential in time, divided into sections in space, and do not interfere with each other. The processing unit thus obtains a computation time window that matches the transport speed, which is beneficial for completing more complex image processing operations without reducing the transport speed.

[0056] Furthermore, the image acquisition unit 41 can reciprocate relative to the conveyor belt along the width direction of the object to be printed, and the width direction intersects with the conveying direction. In this embodiment, the two are perpendicular to each other.

[0057] Therefore, the relative motion between the image acquisition unit 41 and the object to be printed includes two motion components.

[0058] One is that the image acquisition unit 41 moves back and forth along the width direction with the scanning head frame 40, so that it can acquire images line by line across the entire width. Secondly, the object to be printed moves along the conveyor belt in the conveying direction, allowing it to be continuously fed into the acquisition station along its length. The combination of these two methods enables full-width coverage acquisition of the object's surface without the need for a full-width acquisition device, thus reducing device costs and facilitating adaptation to objects of different widths.

[0059] In some embodiments, the reciprocating movement of the scanning head 40 along the width direction adopts a bidirectional serpentine scanning method, that is, image acquisition is performed on both the outgoing and returning journeys, and the image strips acquired on the outgoing and returning journeys are sequentially connected along the transport direction.

[0060] Specifically, the entire travel of the scanning head 40 is divided into acceleration zones and deceleration zones at both ends, and a constant-speed acquisition zone in the middle. The constant-speed acquisition zone covers the entire width of the object to be printed in the width direction. The scanning head 40 accelerates to the set scanning speed in the acceleration zone, moves at a constant speed and acquires images in the constant-speed acquisition zone, and decelerates, stops and reverses direction in the deceleration zone. The processing unit retains only the image rows acquired in the constant-speed acquisition zone, and inverts the row order of the image strip acquired on the return trip along the width direction before splicing it with the image strip from the outgoing trip.

[0061] Thus, on the one hand, bidirectional acquisition allows the empty travel during reversal to be utilized, improving scanning efficiency compared to unidirectional acquisition; on the other hand, limiting acquisition to a uniform speed acquisition area and reversing the return line sequence can avoid uneven sampling intervals caused by acceleration and deceleration and image mirroring errors caused by inconsistent forward and backward directions, ensuring the geometric consistency of the stitched two-dimensional image.

[0062] Furthermore, the moving speed of the scanning head 40 along the width direction and the conveying speed of the conveyor belt satisfy a preset matching relationship, so that in the time it takes for the scanning head 40 to complete one single scan, the distance the object to be printed moves forward along the conveying direction is not greater than the width that the image acquisition unit 41 can cover in a single scan, thereby making two adjacent image belts connect or partially overlap in the conveying direction, and there are no missed areas on the surface.

[0063] In some embodiments, two adjacent image strips are set as an overlapping area with a preset width. During stitching, the processing unit aligns the images within the overlapping area according to their positions and performs weighted fusion. In this way, even if there is a slight synchronization error between the reversal time of the scanning head 40 and the transport displacement, the overlapping area can absorb it, and the texture of the velvet surface at the stitching point remains continuous, avoiding false undulating edges in subsequent feature extraction due to misalignment of the stitching seams.

[0064] In some embodiments, the image acquisition unit 41 includes a line scan imaging unit. During the aforementioned relative motion, the line scan imaging unit acquires surface images of the object to be printed line by line, and sequentially stitches together the successively acquired line images along the direction of relative motion to create a two-dimensional image reflecting the surface state of the object to be printed. Compared to area array imaging, which captures the entire image at once, the line scan imaging unit acquires only one line at a time, with identical acquisition conditions for each line. The resulting two-dimensional image does not exhibit the edge perspective distortion and illumination attenuation inherent in area array imaging across the entire image, and its line resolution can be higher, making it suitable for high-resolution imaging of objects moving continuously along a defined direction.

[0065] Specifically, the line scan imaging unit includes at least one photosensitive component, each of which includes multiple photoelectric conversion elements arranged in a row along the same straight line, forming a linear photosensitive array. The line scan imaging unit also includes a lens located on the light-receiving side of the photosensitive component, used to focus the image of the surface of the object to be printed onto the linear photosensitive array. The extension direction of the linear photosensitive array is consistent with the width direction, that is, each row acquired corresponds to a narrow and long area on the surface of the object to be printed. While the image acquisition unit 41 moves along the width direction, the object to be printed moves forward along the transport direction, so that the rows acquired successively are staggered, and after stitching, a two-dimensional image covering the entire image is obtained.

[0066] Furthermore, as an optional implementation, the linear photosensitive array can be a charge-coupled device (CCD) linear array or a complementary metal-oxide-semiconductor (CMOS) linear array. The former typically has higher sensitivity and lower noise, which is beneficial for obtaining a clear image even in areas with deep shadows on the textured surface; the latter typically has a higher line frequency and lower power consumption, which is beneficial for increasing scanning speed. Those skilled in the art can choose between the two based on the color depth of the object to be printed, the texture height, and the required scanning speed.

[0067] Furthermore, when there are multiple photosensitive components, they are arranged end-to-end along the width direction, with each linear photosensitive array collinearly connected to form an equivalent linear photosensitive array covering a wider width. Thus, even if the imaging width of a single photosensitive component is limited, multiple photosensitive components can be combined to accommodate a wider printing object without increasing the specifications of a single component, which helps to expand the acquireable width while maintaining resolution. In some embodiments, the field-of-view ends of two adjacent photosensitive components overlap by a predetermined number of pixels. The relative positional relationship between each photosensitive component is pre-calibrated at the factory or during installation. The processing unit then combines the image segments acquired by each photosensitive component into a complete line after removing overlaps according to this relationship. In this way, installation gaps and minor misalignments between photosensitive components are absorbed by calibration and overlap fusion, resulting in a continuous and seamless image at the stitching point, avoiding fixed-position image discontinuities at the boundaries of each photosensitive component.

[0068] It should be noted that the image acquisition unit 41 is not limited to the line scan imaging unit described above. As an optional implementation, the image acquisition unit 41 includes an area scan camera, which acquires images of the surface of the object to be printed line by line along a strip-shaped region of interest extending along a line and stitches them together to form a two-dimensional image. That is, by using the two-dimensional photosensitive array of the area scan camera, only one or several lines are taken as the effective acquisition area, which approximates the acquisition effect of line scan. Alternatively, the image acquisition unit 41 includes a contact image sensor, which is close to the surface of the object to be printed and acquires images line by line. The contact image sensor usually integrates the light source, lens and photosensitive array into one unit, which helps to reduce the size and weight of the image acquisition unit 41, thereby reducing the motion load of the scanning head 40.

[0069] In some embodiments, the line acquisition of the line scan imaging unit is synchronously triggered by the position signal of the position detection unit, rather than running freely at a fixed time frequency.

[0070] Specifically, when the scanning head 40 moves along the width direction, the position read by the reading head 43 (described later) changes by a preset increment, triggering the line scanning imaging unit to acquire one line; for the acquisition cycle along the conveying direction, the encoder (described later) outputs a preset number of pulses to trigger a corresponding acquisition action once.

[0071] In this way, the row acquisition is carried out at equal spatial intervals. Even if there are fluctuations in the speed of the scanning head 40 or the conveyor belt, the spacing between each row on the surface of the object to be printed remains constant. The stitched two-dimensional image will not be stretched or compressed and distorted along the direction of movement due to speed fluctuations. At the same time, each row of images is directly bound to a specific position reading the moment it is triggered for acquisition. The correspondence between the image and the position is guaranteed by the triggering mechanism itself, without relying on the conversion of software timestamps, thus avoiding the correspondence error introduced by transmission delay and system jitter.

[0072] The positioning printing device also includes an illumination unit 42, such as Figure 12 As shown, the illumination unit 42 is located at the bottom of the scanning head frame 40 and faces the object to be printed, and is used to form a linear illumination area on the lines acquired by the online scanning imaging unit.

[0073] Specifically, due to the height difference between high-pile and low-pile surfaces, if a normal surface light source or ring light source is used for illumination, the light will illuminate the velvet surface at an oblique angle. The high-pile surface will cast lateral shadows on the low-pile surface to the side, and the velvet surfaces with different orientations will produce messy reflections. These shadows and reflections appear in the image as abrupt changes in brightness that are unrelated to the real boundary of the velvet surface. They are easily misjudged as the edge of the velvet texture, thus interfering with the extraction of undulation features.

[0074] To eliminate the aforementioned lateral shadows and stray reflections, in some embodiments, the illumination unit 42 includes a line light source that emits linear illumination light. The optical path of the linear illumination light coincides with or is parallel to the imaging optical path of the image acquisition unit 41. The illumination unit 42 also includes a beam splitter located on the imaging optical path. The linear illumination light emitted by the line light source is deflected by the beam splitter and then directed along the imaging optical path toward the object to be printed, illuminating the surface of the object at a perpendicular or near-perpendicular angle. The light reflected from the surface of the object passes through the beam splitter again and returns along the imaging optical path to the line scan imaging unit for reception.

[0075] Specifically, since the illumination light is perpendicular to the textured surface along the imaging light path and returns along the same path, the high textured surface will not cast lateral shadows on the low textured surface, and the reflected light from the textured surface is also received along the imaging light path instead of being scattered elsewhere. Therefore, the acquired image has strong contrast between light and dark, and the outline of the textured surface is clear and complete.

[0076] As an optional implementation, the beam-splitting element can be a beam splitter or a semi-transparent mirror, both of which can deflect a portion of the illumination light and direct it toward the object to be printed, while allowing a portion of the reflected light to be transmitted back to the line scan imaging unit. Furthermore, a light-absorbing element, such as a light-absorbing cavity with an inner wall coated with an matting material, can be provided on the side of the beam-splitting element facing away from the object to be printed. This absorbs the remaining portion of the illumination light that passes through the beam-splitting element but does not reach the object to be printed, preventing it from being repeatedly reflected inside the scanning head 40 and mixing into the imaging light path to form stray light, thereby further improving the image signal-to-noise ratio.

[0077] Furthermore, line light sources can be implemented in various ways.

[0078] As an optional implementation, the line light source is an LED line light source, including a high-brightness LED array arranged in a row and a cylindrical lens group located on its light-emitting side to converge the light emitted by the array into a linear illumination beam; or, the line light source is a laser line generator, including a semiconductor laser diode and a Powell prism located on its light-emitting side to expand the laser beam into a linear laser with uniform energy distribution; or, the line light source is a common white light source combined with a slit aperture, where the slit aperture only forms a linear illumination beam through the portion passing through the slit. Compared to a surface light source, the above-mentioned line light source concentrates light energy on the row being collected, resulting in high energy utilization. Even for dark, light-absorbing, or highly reflective objects to be printed, sufficient and uniform illumination can be obtained on that row.

[0079] It should be noted that the arrangement of the illumination unit 42 is not limited to the coaxial illumination described above. As an optional implementation, the illumination unit 42 includes two line light sources disposed on either side of the line scanning imaging unit. These two light sources are tilted towards the line being captured at a preset angle (e.g., between 30° and 60°, such as 45°) to the vertical direction, so that the illumination from both sides overlaps and fills in the shadows cast by the textured surface. Alternatively, a light shield can be placed between the image acquisition unit 41 and the object to be printed to block ambient light, and this can be used in conjunction with the tilted line light sources. Any linear illumination area with uniform illuminance that suppresses textured shadows on the line being captured falls within the scope of this invention.

[0080] In some embodiments, the control unit integrated on the scanning head 40 is electrically connected to the illumination unit 42. Based on the brightness statistics of the image acquired by the line scan imaging unit (e.g., the average grayscale value or grayscale histogram of each line), it adjusts the driving current or dimming duty cycle of the line light source in real time, and / or adjusts the line exposure time of the line scan imaging unit, so that the brightness of the acquired image remains within a preset target range. Thus, even when faced with situations where dark light-absorbing velvet surfaces coexist with light-colored high-reflectivity velvet surfaces, or when different batches of objects to be printed have significantly different reflectivities, the contrast of the image is always within a suitable range for feature extraction, avoiding overexposure or underexposure that could lead to loss of velvet surface details, thereby ensuring the stability and consistency of undulating feature extraction.

[0081] In some embodiments, such as Figures 9 to 11 As shown, the scanning main beam 30 spans across the conveyor belt and extends along the width direction, with its two ends fixed by support columns; the scanning head frame 40 is slidably mounted on the scanning main beam 30 along the width direction via linear guide rail pair 31.

[0082] Specifically, the guide rail pair 31 includes two linear guide rails extending along the width direction and spaced apart from each other, and multiple sliders that slide in cooperation with the linear guide rails. The two linear guide rails are fixed parallel to each other on the side of the scanning main beam 30 facing the scanning head 40, and the scanning head 40 is straddled on the two linear guide rails via the multiple sliders. In this way, the scanning head 40 is supported by the two linear guide rails, maintaining stability during movement and avoiding pitching or twisting due to single guide rail support, thereby ensuring that the distance and orientation between the image acquisition unit 41 and the surface of the object to be printed remain constant.

[0083] Furthermore, such as Figure 9 and Figure 10 As shown, the positioning printing device also includes a servo motor 51, a reducer 52, a coupling 53, a driving synchronous pulley 54, a driven synchronous pulley 55, and a synchronous belt 56. The output shaft of the servo motor 51 is connected to the driving synchronous pulley 54 via the reducer 52 and the coupling 53. The driving synchronous pulley 54 is located at one end of the scanning main beam 30 along the width direction; as shown... Figure 11 As shown, the driven synchronous pulley 55 is located at the other end of the scanning main beam 30 along the width direction; the synchronous belt 56 is tensioned between the driving synchronous pulley 54 and the driven synchronous pulley 55 and extends along the width direction, and the scanning head frame 40 is fixedly connected to the synchronous belt 56. In this way, the rotational motion output by the servo motor 51 is reduced and amplified by the reducer 52, which drives the driving synchronous pulley 54 to rotate, and then converted into linear traction along the width direction by the synchronous belt 56, driving the scanning head frame 40 to reciprocate along the scanning main beam 30; the use of the servo motor 51 to drive the scanning head frame 40 allows for precise control of the moving speed and position of the scanning head frame 40 to meet the requirements of constant speed movement within the aforementioned uniform speed acquisition area.

[0084] Furthermore, such as Figure 13 and Figure 16 As shown, the scanning head frame 40 and the timing belt 56 are fixedly connected by a fixing assembly 60. Two sets of fixing assemblies 60 are provided, located on opposite sides of the scanning head frame 40 along its width and respectively clamping the timing belt 56. Each fixing assembly 60 includes a toothed belt clamping block 61, a toothed belt clamping seat 62, and a bolt. The toothed belt clamping block 61 and the toothed belt clamping seat 62 are arranged opposite each other, and at least one of their clamping surfaces has a toothed groove that meshes with the teeth of the timing belt 56. The timing belt 56 is clamped between the toothed belt clamping block 61 and the toothed belt clamping seat 62, and the bolt passes through the toothed belt clamping block 61 and the toothed belt clamping seat 62 so that they cooperate to clamp and fix the timing belt 56. Because the clamping surface meshes with the teeth of the synchronous belt 56, the clamping force is transmitted through the tooth surface, and the synchronous belt 56 will not slip or creep at the clamping point; the two sets of fixing components 60 are symmetrically subjected to force from both sides of the scanning head frame 40, which is equivalent to connecting the scanning head frame 40 in series in the loop of the synchronous belt 56. The elastic deformation of the synchronous belt 56 at the moment of reversal will not be converted into the idle stroke of the scanning head frame 40, which is conducive to ensuring the positioning consistency in both forward and reverse directions.

[0085] Furthermore, such as Figure 16 As shown, the fixing assembly 60 also includes an adjusting fastener 63 and an adjusting screw 64. The adjusting fastener 63 is fixed to the scanning head frame 40, and the adjusting screw 64 passes through the toothed belt clamp 61 and is threadedly connected to the adjusting fastener 63. By adjusting the screw-in amount of the adjusting screw 64, the distance between the toothed belt clamp 61 and the adjusting fastener 63 can be changed, thereby pulling the clamped synchronous belt 56 to adjust its tension. In this way, the elongation of the synchronous belt 56 due to long-term use can be easily compensated during assembly and subsequent maintenance, keeping its tension within the set range. With constant tension, the elastic hysteresis and backlash of the synchronous belt 56 are suppressed, and the positioning accuracy of the scanning head frame 40 along the width direction is maintained throughout the entire service life of the device.

[0086] In some embodiments, such as Figure 10As shown, the positioning printing device also includes a limiting component to limit the movable range of the scanning head 40 along the width direction and provide safety protection. Specifically, the limiting component includes a proximity switch 71, a limit switch 72, mechanical limiting components 73, and a buffer block 74. The proximity switch 71 is located at the beginning of the scanning stroke and is used to mark the starting scanning position of the scanning head 40, i.e., its mechanical origin along the width direction; the two limit switches 72 are respectively located at both ends of the scanning stroke and are used to send a stop signal to the control system when the scanning head 40 exceeds the normal stroke, forming a soft limit; the two mechanical limiting components 73 are respectively located at both ends of the scanning main beam 30 and outside the limit switches 72, and are equipped with buffer blocks 74 to buffer the scanning head 40 in case of accidents such as limit switch 72 failure, preventing it from rushing out of the scanning main beam 30, forming a hard limit. Thus, the proximity switch 71, the limit switch 72, and the mechanical limit component 73 respectively perform the functions of origin positioning, soft limit, and hard limit, ensuring the reliability and safety of the reciprocating movement of the scanning head 40 step by step.

[0087] Furthermore, in some embodiments, the scanning head 40 is controlled to move to the proximity switch 71 to perform a zero-return correction after each preset number of reciprocating strokes, so that the position reading of the position detection unit in the width direction is realigned with the mechanical origin; the above-mentioned zero-return correction is also performed every time the device is powered on for self-test. In this way, the position deviation accumulated by factors such as count loss and slight slippage that may occur during long-term continuous operation is periodically cleared to zero, and the absolute positioning accuracy of the scanning head 40 in the width direction does not deteriorate with the running time, ensuring the consistency of the image position reference between thousands of reciprocating scans.

[0088] Furthermore, such as Figure 9 and Figure 14 As shown, the positioning printing device also includes a cable chain system for storing and protecting the cables connecting the scanning head 40 to the external fixed end. Specifically, the cable chain system includes a silent cable chain 81, a cable chain support assembly 82, and a camera cable clamp 83. One end of the silent cable chain 81 moves with the scanning head 40, while the other end is fixed relative to the scanning main beam 30. It houses the power supply and data cables connecting the image acquisition unit 41, the illumination unit 42, and the control unit. The cable chain support assembly 82 is positioned below the silent cable chain 81 to support it and prevent it from collapsing under its own weight. The camera cable clamp 83 is positioned near the inlet / outlet end of the silent cable chain 81 close to the scanning head 40 and clamps and secures each cable, preventing them from tangling during high-speed reciprocating movement or being repeatedly stressed at the joints. In this way, each cable always moves with the scanning head 40 with a controlled bending radius, ensuring stable transmission of image data even under high-speed reciprocating conditions and preventing image loss due to cable fatigue or poor contact.

[0089] like Figures 11 to 15As shown, the scanning head frame 40 includes a slider fixing plate 44. The aforementioned slider, which cooperates with the guide rail pair 31, is fixed to the back side of the slider fixing plate 44 to achieve a sliding connection between the scanning head frame 40 and the guide rail pair 31. The scanning head frame 40 also includes a first side plate 45 and a second side plate 46 respectively fixed to both sides of the slider fixing plate 44 along the width direction. Together with the slider fixing plate 44, they form an installation space for accommodating and protecting the image acquisition unit 41. Figure 13 As shown, the slider fixing plate 44 is also provided with the reading head 43, which will be described later.

[0090] Furthermore, such as Figure 13 and Figure 17 As shown, the scanning head frame 40 also includes a camera mounting plate 47 and a camera connector 48. The camera mounting plate 47 is located between the first side plate 45 and the second side plate 46 and is parallel to the slider fixing plate 44. The image acquisition unit 41 is fixed to the front end of the camera mounting plate 47 via the camera connector 48.

[0091] For example, the camera mounting plate 47 has two first waist holes 471 along the vertical direction, and multiple first bolts pass through the first waist holes 471 and are threadedly connected to the slider fixing plate 44. When it is necessary to adjust the height of the image acquisition unit 41, loosening each of the first bolts allows the camera mounting plate 47, together with the image acquisition unit 41, to move vertically relative to the slider fixing plate 44. After adjustment, tighten each of the first bolts to fix it. Adjusting this height adjusts the object distance between the image acquisition unit 41 and the surface of the object to be printed, thereby changing the focus state and imaging field of view to adapt to objects of different thicknesses or lenses with different focal lengths.

[0092] Furthermore, such as Figure 17 As shown, the camera mounting plate 47 also has a second waist hole 472 along the width direction, and the image acquisition unit 41 is threaded with a second bolt passing through the second waist hole 472. When it is necessary to adjust the horizontal position of the image acquisition unit 41 along the width direction, loosening each of the second bolts will allow it to move relative to the camera mounting plate 47 along the width direction. After adjustment, tightening will fix it. In this way, through the cooperation of the first waist hole 471 and the second waist hole 472, the image acquisition unit 41 obtains the installation and adjustment capability of two degrees of freedom in the vertical direction and the width direction, which can both focus and achieve centering with the illumination area and the scanning stroke.

[0093] Furthermore, such as Figure 14 and Figure 15 As shown, the scanning head frame 40 also includes a first lamp source connecting plate 491 and a second lamp source connecting plate 492 located at its bottom. The first lamp source connecting plate 491 and the second lamp source connecting plate 492 are arranged opposite to each other, and the lighting unit 42 is adjustablely arranged on the first lamp source connecting plate 491 and the second lamp source connecting plate 492.

[0094] For example, both the first lamp source connecting plate 491 and the second lamp source connecting plate 492 have a third oblong hole along the vertical direction, and a third bolt threaded into the third oblong hole is threaded to the lighting unit 42. When it is necessary to adjust the height of the lighting unit 42, the third bolt can be loosened to move it vertically relative to the first lamp source connecting plate 491 and the second lamp source connecting plate 492. After adjustment, it can be tightened to fix it. In this way, the distance between the linear light source and the surface of the object to be printed can be adjusted through the third oblong hole, so that the width and illuminance of the linear illumination area can be adapted to the objects to be printed with different thicknesses and different texture heights. At the same time, the first lamp source connecting plate 491 and the second lamp source connecting plate 492, which are arranged opposite each other, also form a shielding effect on the acquisition area from both sides, which also has the function of suppressing ambient stray light from entering the imaging light path.

[0095] In some embodiments, such as Figure 11 and Figure 14 As shown, the upper part of the scanning head frame 40 forms a housing that covers the image acquisition unit 41. Ventilation vents and cooling fans are installed on the side panels of the housing. The cooling fans force external air into the housing through the vents, past the image acquisition unit 41 and the heat-generating parts of the control unit, and then exhaust it. In this way, during long-term continuous operation, the temperature of the photosensitive components, lens, and processing circuitry of the line scan imaging unit remains stable, preventing slow changes in focal plane position, imaging scale, or dark current noise caused by temperature drift. This ensures stable image quality and image-position correspondence during long-term continuous production. Furthermore, dust filters can be installed at the vents, and sealing strips can be installed at the seams of the housing to prevent ink mist and environmental dust that may escape from the printing station from accumulating on the surface of the lens or beam splitter, reducing the frequency of cleaning and maintenance of optical components.

[0096] In some embodiments, a control unit is also integrated on the scanning head 40. The control unit adjusts the brightness of the line light source according to the aforementioned closed-loop adjustment method, simultaneously acquires image data output by the line scanning imaging unit nearby, and transmits the image data to the processing unit via the cable in the silent cable chain 81. The control unit also receives the position signal from the position detection unit and executes the aforementioned synchronization logic for triggering line acquisition by position increment. Integrating the control unit nearby on the scanning head 40 can shorten the transmission path of high-speed image signals and reduce signal attenuation and interference caused by long-distance transmission.

[0097] It should be noted that the mechanism that enables relative movement between the image acquisition unit 41 and the object to be printed is not limited to the aforementioned method of the scanning head 40 reciprocating along the scanning main beam 30 in conjunction with the conveyor belt. As an optional implementation, a gantry-type dual-axis moving mechanism can be used, allowing the image acquisition unit 41 to move both along the width direction and along the length direction of the object to be printed, thereby completing full-width acquisition through its dual-axis movement when the object to be printed is stationary or being independently conveyed; or the independently set scanning main beam 30 and related mechanisms can be eliminated, and the image acquisition unit 41 and the illumination unit 42 can be directly integrated into the original movable print head of the printing unit 20, with the acquisition field of view located upstream of the printhead along the conveying direction, and the acquisition can be completed before printing begins or during its return stroke using the original movement mechanism of the print head, thereby simplifying the mechanical structure and reducing the footprint of the device along the conveying direction.

[0098] Furthermore, the driving method for the scanning head 40 is not limited to the aforementioned synchronous belt drive. As an optional implementation, a linear motor can be used to directly drive the scanning head 40 to move along the scanning main beam 30, which has no intermediate transmission links, no backlash, and higher dynamic response; alternatively, a lead screw and nut pair or a gear and rack pair can be used to convert the rotational motion of the servo motor 51 into linear motion along the width direction. Any transmission method capable of driving the scanning head 40 to reciprocate in a controlled manner along the width direction can be used in this invention.

[0099] In some embodiments, such as Figure 9 and Figure 13 As shown, a magnetic scale is provided on the scanning main beam 30 along the width direction, and a reading head 43 opposite to the magnetic scale is provided on the slider fixing plate 44 of the scanning head frame 40. An encoder for detecting the displacement of the object to be printed along the conveying direction is provided on the conveying unit 10. The magnetic scale, reading head 43 and encoder together constitute a position detection unit. Specifically, the reading head 43 moves along the magnetic scale with the scanning head frame 40 and reads the position of the image acquisition unit 41 along the width direction in real time; the encoder detects the operation of the conveyor belt and obtains the displacement of the object to be printed along the conveying direction; the combination of the two can determine the two-dimensional position of each row on the surface of the object to be printed along the width direction and the conveying direction when acquiring each row of images. Then, the processing unit establishes the correspondence between each row of images and the surface image formed by splicing each row and the corresponding position. It is worth noting that the magnetic scale and the reading head 43 directly measure the actual position of the scanning head frame 40 relative to the scanning main beam 30, rather than being calculated and estimated by the encoder at the end of the servo motor 51. Error factors such as the elastic deformation of the synchronous belt 56 and the transmission gap are not included in the position measurement result. This constitutes a fully closed-loop detection of the position of the scanning head frame 40, and the measured position can truly represent the actual location of the image acquisition unit 41.

[0100] As an optional implementation, the combination of the magnetic scale and the reading head 43 can be replaced by a combination of an optical scale and a corresponding reading head. The optical scale has higher resolution, while the magnetic scale is more resistant to oil and dust, and can be selected according to the usage environment. The encoder can be a rotary encoder installed on the shaft end of the drive or driven roller of the conveyor belt, or a measuring wheel encoder that directly presses against the belt surface, or a linear encoder or wire encoder that directly detects the displacement of the belt surface. The latter can avoid errors introduced by belt slippage. Any device that can detect the position of the object to be printed relative to the image acquisition unit 41 when acquiring images of each surface can be used to construct a position detection unit.

[0101] In some embodiments, the processing unit includes an industrial computer or embedded processor and an image acquisition card connected to the image acquisition unit 41. The processing unit is communicatively connected to the control unit, the position detection unit, and the inkjet controller of the printing unit 20. Further, the processing unit divides the surface of the object to be printed into multiple sequentially connected segments according to the conveying direction, and performs pipeline-style processing on each segment: when a segment has generated printing control data and entered printing, the next segment is undergoing undulation feature extraction and pattern correction, and the segment after that is being acquired; the image data corresponding to the segment that has been printed is released, and its storage space is used cyclically by subsequent segments. Thus, the acquisition, processing, and printing processes proceed in parallel on different segments, and computing and storage resources are reused segment by segment. The device can perform uninterrupted positioning printing on continuously supplied rolls of objects with unlimited length, without being limited by the overall image buffer capacity, meeting the needs of continuous industrial production.

[0102] In some embodiments, the processing unit further performs a calibration step in advance to establish a mapping relationship between the image coordinate system of the image acquisition unit 41 and the printing coordinate system of the printing unit 20. As an optional implementation, the calibration step includes: the printing unit 20 printing a calibration pattern containing multiple calibration marks on a calibration medium (e.g., a blank object to be printed or a special calibration base cloth) according to known calibration data; the calibration medium carrying the calibration pattern being acquired by the image acquisition unit 41; the processing unit identifying the position of each calibration mark in the acquired image and comparing it with the printing coordinates used during printing, thereby calculating the translation, rotation angle, and scaling factor between the two coordinate systems, as well as the actual distance between the image acquisition unit 41 and the printing unit 20 along the transport direction. Subsequently, when generating printing control data, the processing unit converts the printing position determined based on the surface image to the printing coordinate system according to this mapping relationship. In this way, systematic deviations such as the installation position error between the scanning main beam 30 and the printing unit 20, and the slight tilt of the image acquisition unit 41 relative to the width direction are all absorbed by the calibration relationship, and the requirements of the device for mechanical installation accuracy are reduced; after maintenance or replacement of parts, only one calibration is needed to restore the alignment accuracy, without the need for cumbersome mechanical adjustment.

[0103] Based on the above-described positioning printing device, this embodiment of the invention also provides a positioning printing method, which can be executed by the above-described positioning printing device. Figure 18 As shown, the positioning printing method includes the following steps S1 to S5.

[0104] Step S1 involves creating relative motion between the image acquisition unit 41 and the object to be printed. Specifically, the conveying unit 10 carries the object to be printed and moves it along the conveying direction, while the image acquisition unit 41 reciprocates along the width direction, thus creating a combined relative motion between the image acquisition unit 41 and the object to be printed along both the width and conveying directions. During this process, the object to be printed is stably fixed to the conveyor belt by the aforementioned anti-slip structure, ensuring that it remains relatively stationary with respect to the conveyor belt throughout the entire process from acquisition to printing.

[0105] In step S2, during the aforementioned relative motion, the image acquisition unit 41 continuously acquires surface images of the object to be printed, and the position detection unit detects the position of the object to be printed relative to the image acquisition unit 41 when acquiring each surface image, establishing a correspondence between each surface image and its corresponding position. Specifically, the line scan imaging unit acquires surface images row by row, with each row acquisition triggered by the position signal from the position detection unit at equal spatial increments. Each acquired row is then bound to its corresponding position reading. The processing unit sequentially stitches the successively acquired rows along the relative motion direction into a two-dimensional surface image and records the correspondence between each location on the image and the actual position on the surface of the object to be printed.

[0106] Step S3 involves extracting the undulation features of the surface of the object to be printed from the surface image. These undulation features characterize the actual distribution of three-dimensional pile surfaces, such as high-pile and low-pile, loop pile and cut pile, on the surface of the object to be printed. Specifically, step S3 includes the following sub-steps.

[0107] Sub-step S31 involves preprocessing the surface image. The processing unit filters and denoises the surface image, for example, using median filtering to suppress isolated noise points and Gaussian filtering to smooth the fine burrs on the textured surface; and performs row-by-row brightness equalization correction on the surface image to eliminate any unevenness in illumination along the width direction and brightness differences between rows caused by different acquisition times, so that textured surfaces of the same height present a consistent gray level throughout the image.

[0108] Sub-step S32 calculates the grayscale distribution characteristics of the surface image. Under the aforementioned coaxial vertical illumination, the high-textured area appears as a higher grayscale in the image because it is closer to the lens and receives stronger light, while the low-textured area appears as a lower grayscale because it is relatively concave and receives weaker light. Therefore, the grayscale level of the image can reflect the undulation of the textured surface. The processing unit calculates the grayscale gradient and spatial distribution of the grayscale in the surface image to distinguish between the high-textured area and the low-textured area.

[0109] Sub-step S33: Extract the ridges and contours of the suede texture. The processing unit extracts the ridges of the high-suede areas and the boundary contours between the high-suede and low-suede areas from the grayscale distribution above, as undulation features characterizing the suede surface undulations. Furthermore, considering that the suede texture of the surface of the object to be printed usually exhibits a certain periodicity or directionality, before extracting the ridges and contours, the processing unit can also perform frequency domain filtering on the surface image, that is, transform the surface image to the frequency domain, retain the frequency components corresponding to the periodicity of the suede texture while suppressing the other frequency components, so as to enhance the regularly arranged suede texture and weaken the interference of random distribution; the processing unit can also perform morphological processing on the extracted undulation features, for example, by using morphological opening operations to remove small false features caused by individual fallen suede heads or surface stains, and by using morphological closing operations to connect the ridges that are broken due to accidental occlusion, thereby obtaining complete, continuous and interference-resistant undulation features.

[0110] Step S4: Based on the undulation characteristics and the correspondence established in step S2, determine the printing position of the target printed pattern on the surface of the object to be printed, and generate printing control data accordingly. Specifically, step S4 includes the following sub-steps.

[0111] Sub-step S41 compares the extracted undulation features with the reference texture corresponding to the target printed pattern. The reference texture is the velvet texture used when designing the target printed pattern, such as the texture of the velvet pattern used as the base pattern, which records the velvet undulations that should originally correspond to each part of the target printed pattern. The processing unit registers the actually extracted undulation features with the reference texture to obtain the deviation between the two.

[0112] Sub-step S42: Adjust the target printed pattern according to the above deviation. The adjustment includes at least one of overall translation, rotation and scaling of the target printed pattern to compensate for the overall positional deviation of the object to be printed during transportation and placement; the adjustment also includes local deformation of the target printed pattern to compensate for local deformation of the object to be printed due to weaving tolerances, stretching and springback, etc.

[0113] Sub-step S43 generates printing control data based on the adjusted target printing pattern. The printing control data is used to control the printing unit 20 to print at the corresponding positions on the surface of the object to be printed, so that the target printing pattern corresponds to the undulation characteristics of the surface of the object to be printed, that is, the parts of the target printing pattern that should originally fall on the high pile actually fall on the high pile, and the parts that should originally fall on the low pile actually fall on the low pile, thereby achieving pattern matching with the pile surface.

[0114] It should be explained in detail that the above registration and adjustment can be carried out in a two-level manner, from the whole to the part.

[0115] In the first stage, the processing unit performs overall registration of the undulation features and the reference texture. For example, it uses a phase correlation-based method to determine the overall translation, rotation angle, and scaling ratio between the two. Based on this, it performs corresponding overall translation, rotation, and scaling on the target printed pattern to correct the overall positional deviation. The overall positional deviation mainly originates from the translation and deflection of the object to be printed relative to the ideal position when it is carried and laid out, as well as the overall differences in weaving width between different batches.

[0116] In the second stage, the processing unit divides the overall registered undulation features and reference texture into multiple grids, calculates the local displacements between corresponding grids one by one, obtains the displacement field reflecting the local deformation at each location, and uses the local displacements of each grid as control points to continuously deform the target printed pattern locally using methods such as thin-plate spline interpolation. The local deformation represents the stretching and twisting of the surface of the object to be printed relative to the reference texture, mainly originating from uneven weaving tension, local flattening of the pile, and local stretching and rebound during the bearing process.

[0117] Furthermore, for grids whose local displacement cannot be reliably determined due to surface soiling, obstruction, or other reasons, the processing unit does not use its own potentially distorted registration results. Instead, it calculates the displacement of the grid based on the local displacement interpolation of adjacent, reliably registered grids, thereby avoiding significant distortion caused by individual abnormal grids. In this way, by compensating for overall positional deviations through overall registration, compensating for local deformations through gridded local registration, and replacing invalid grids through interpolation, it ensures that the target printed pattern is macroscopically aligned with the object to be printed and microscopically conforms to the actual surface of the pile. This achieves good pattern matching accuracy even under actual production conditions with weaving tolerances and deformations.

[0118] Step S5: When the surface of the object to be printed moves to the printing unit 20 along with the conveying unit 10, the printing unit 20 prints on the surface of the object according to the printing control data. Specifically, the processing unit determines the time when the area to be printed on the object that has been captured arrives at the printing unit 20 based on the distance between the image acquisition unit 41 and the printing unit 20 along the conveying direction, and the conveying displacement of the object to be printed from the acquisition station along the conveying direction. When the area to be printed arrives at the printing unit 20, the processing unit triggers the printing unit 20 to print according to the printing control data corresponding to the area to be printed. Preferably, the distance is the actual distance between the image acquisition unit 41 and the printing unit 20 calculated in the aforementioned calibration step, so as to make the determination of the printing time more accurate.

[0119] In some embodiments, the printing unit 20 performs line-by-line printing, meaning that its printheads, arranged along the width direction, eject ink droplets line by line as the object to be printed moves along the transport direction. Alternatively, the object to be printed moves continuously, and the printheads print line-by-line according to the transport displacement signal provided by the encoder; or, the object to be printed moves in steps, printing one line at a time for each step, alternating between the two. The former is more efficient, while the latter offers more accurate positioning; the choice can be made based on the paper size and required precision.

[0120] In one printing process, the processing unit obtains the positions of high-pile and low-pile areas based on the undulation characteristics, and generates printing control data for the first printing module 21 and the second printing module 22 to execute, respectively, in conjunction with the target printing pattern. When the printing area reaches the printing unit 20, the valve-controlled jet head 211 corresponding to the high-pile area opens, causing the pressurized first coloring medium to be sprayed towards the high-pile area; the on-demand inkjet head 221 corresponding to the low-pile area forms droplets according to the printing control data and sprays them towards the low-pile area.

[0121] For the boundary between the high-pile and low-pile areas, the second printing module 22 can print the boundary outline, while the first printing module 21 prints the high-pile portion near the boundary. Alternatively, a transition area can be set on both sides of the boundary, reducing the operating time or number of times the first printing module 21 operates, and allowing the second printing module 22 to adjust the number of droplets, thereby enabling the two types of coloring media to connect near the boundary.

[0122] In some embodiments, the undulation feature also includes height values ​​at various points on the velvet surface. As an optional implementation, a structured light projector can be added to the image acquisition unit 41 to project structured light stripes onto the surface of the object to be printed. The line scan imaging unit acquires the stripe image, which is distorted by the velvet surface modulation, and the processing unit calculates the height values ​​at various points on the velvet surface accordingly. Accordingly, when generating print control data, the processing unit adjusts the ink jet amount or number of printing passes of the printing unit 20 at the corresponding points based on the height value. For example, it appropriately increases the ink jet amount or uses multiple printing passes for higher velvet areas, and appropriately reduces the ink jet amount for lower velvet areas to compensate for the difference in the flight distance of ink droplets from the printhead to the velvet surface, ensuring that the ink achieves a consistent coloring depth on velvet surfaces of varying heights, thereby further improving the visual uniformity of the printed pattern on the three-dimensional velvet surface.

[0123] In some embodiments, the image acquisition unit 41 includes two photosensitive components disposed on both sides of the scanning head 40, which image the same row of textured surface from different directions. Due to the different observation directions, the shadows cast by the same textured surface in the two images are located on different sides. The processing unit merges the two images, that is, the illuminated area in one image fills the shadow area in the other image, thereby further reducing the influence of textured surface shadows on the extraction of undulation features and obtaining a more complete textured surface contour.

[0124] In some embodiments, the image acquisition unit 41 is a color line scan imaging unit that acquires the color of the surface of the object to be printed while acquiring the undulations of the velvet surface. Accordingly, when generating print control data, the processing unit performs color compensation on the corresponding parts of the target print pattern according to the background color of each part of the surface. For example, it appropriately increases the ink volume or adjusts the ink ratio for areas with a darker background color, so that the final print color is not affected by the background color of the object to be printed, thereby obtaining accurate print colors even on objects with a background color.

[0125] In some embodiments, the positioning printing apparatus further includes a re-inspection image acquisition unit downstream of the printing unit 20 along the conveying direction, used to acquire surface images of the printed area. The processing unit compares the acquired printing result with the target printing pattern to assess the registration deviation of the actual printing position relative to the undulations of the pile surface, and feeds this deviation back to the printing control data generation stage to correct the printing position of the subsequent printing area. In this way, the apparatus forms a closed loop from acquisition, printing to re-inspection. Even if there is a systematic offset of ink droplet landing points or slow nozzle drift, continuous correction can be made through re-inspection feedback, so that the registration accuracy remains stable during long-term continuous production.

[0126] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "include," "contain," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0127] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A positioning printing device for positioning printing on the surface of an object to be printed, characterized in that, include: The conveyor unit is used to carry and transport the object to be printed. An image acquisition unit is disposed above the conveying unit and is used to continuously acquire surface images of the object to be printed during the relative movement between the image acquisition unit and the object to be printed. A position detection unit is used to detect the position of the object to be printed relative to the image acquisition unit when acquiring each of the surface images; The processing unit is communicatively connected to the image acquisition unit and the position detection unit, respectively, and is used to establish the correspondence between each of the surface images and the position detected by the position detection unit, extract the undulation features of the surface of the object to be printed from the surface image, and determine the printing position of the target printing pattern on the surface of the object to be printed according to the undulation features and the correspondence, thereby generating printing control data. and The printing unit is communicatively connected to the processing unit and is used to print on the surface of the object to be printed according to the printing control data when the surface of the object to be printed moves to the printing unit along with the conveying unit. The printing position is the position where the target printed pattern corresponds to the undulation features of the surface of the object to be printed.

2. The positioning printing device according to claim 1, characterized in that, The conveying unit includes a continuously extending conveyor belt, and the object to be printed is supported on the upper surface of the conveyor belt; The image acquisition unit and the printing unit are arranged at intervals along the conveying direction of the conveyor belt, with the image acquisition unit located upstream of the printing unit; The image acquisition unit is capable of reciprocating relative to the conveyor belt along the width direction of the object to be printed, the width direction intersecting the conveying direction, and the relative motion includes the reciprocating movement of the image acquisition unit along the width direction and the movement of the object to be printed along the conveying direction with the conveyor belt.

3. The positioning printing device according to claim 1 or 2, characterized in that, The image acquisition unit includes a line scan imaging unit, which acquires surface images of the object to be printed line by line during the relative motion, and stitches the successively acquired line images into a two-dimensional image along the direction of the relative motion. The positioning printing device also includes an illumination unit, which is positioned toward the object to be printed and is used to form a linear illumination area on the lines acquired by the line scan imaging unit.

4. The positioning printing device according to claim 3, characterized in that, The line scan imaging unit includes at least one photosensitive component, and each photosensitive component includes a plurality of photoelectric conversion elements arranged in a row along the same straight line, the row of photoelectric conversion elements forming a linear photosensitive array. When there are multiple photosensitive components, the multiple photosensitive components are arranged end to end along the width direction of the object to be printed.

5. The positioning printing device according to claim 3, characterized in that, The illumination unit includes a line light source, which is used to emit linear illumination light. The optical path of the linear illumination light coincides with or is parallel to the imaging optical path of the image acquisition unit. The illumination unit further includes a beam splitter located on the imaging optical path. The linear illumination light is deflected by the beam splitter and then directed along the imaging optical path toward the object to be printed.

6. The positioning printing device according to claim 2, characterized in that, It also includes the scanning main beam and the scanning head frame; The scanning main beam spans across the conveyor belt and extends along the width direction. The scanning head frame is slidably mounted on the scanning main beam along the width direction via a linear guide pair. The image acquisition unit is fixed to the scanning head frame. The linear guide pair includes two linear guide rails that extend along the width direction and are spaced apart from each other. The scanning head frame straddles the two linear guide rails. The positioning and printing device further includes a servo motor, a reducer, a coupling, a driving synchronous pulley, a driven synchronous pulley, and a synchronous belt. The output shaft of the servo motor is connected to the driving synchronous pulley via the reducer and the coupling. The synchronous belt is tensioned between the driving synchronous pulley and the driven synchronous pulley. The scanning head frame is fixedly connected to the synchronous belt so that the servo motor drives the scanning head frame to reciprocate along the scanning main beam via the synchronous belt. A magnetic scale is provided on the scanning main beam along the width direction, and a reading head is provided on the scanning head frame opposite to the magnetic scale. An encoder is provided on the conveying unit for detecting the displacement of the object to be printed along the conveying direction. The magnetic scale, the reading head and the encoder together constitute the position detection unit.

7. A positioning printing method, applied to the positioning printing apparatus as described in any one of claims 1 to 6, characterized in that, Includes the following steps: This causes relative motion between the object to be printed and the image acquisition unit; During the relative motion, the image acquisition unit continuously acquires surface images of the object to be printed, and each surface image corresponds to the position of the object to be printed relative to the image acquisition unit when the surface image is acquired. Extract the undulation features of the surface of the object to be printed from the surface image; The positional correspondence between the target printing pattern and the surface of the object to be printed is determined based on the undulation characteristics, and printing control data is generated by combining the correspondence between each surface image and the position. The surface of the object to be printed is moved to the printing unit, and the printing unit prints the image onto the surface of the object according to the printing control data, so that the target print pattern corresponds to the undulating features of the surface of the object to be printed.

8. The positioning printing method according to claim 7, characterized in that, The step of continuously acquiring surface images of the object to be printed includes: The surface image of the object to be printed is acquired row by row by the line scanning imaging unit during the relative motion, and the successively acquired row images are stitched together into a two-dimensional image along the direction of the relative motion. While acquiring images of each row, a linear illumination light is projected onto the row being acquired on the object to be printed through an illumination unit. The illumination area formed by the linear illumination light corresponds to the row being acquired.

9. The positioning printing method according to claim 7 or 8, characterized in that, The step of generating print control data includes: The extracted undulation features are compared with a pre-defined reference texture to obtain the overall positional deviation and local deformation of the actual texture of the object surface to be printed relative to the reference texture. The target printing pattern is translated, rotated, scaled, and locally deformed according to the overall positional deviation and the local deformation to obtain a corrected pattern corresponding to the undulation features of the surface of the object to be printed. The printing control data is generated from the modified pattern.

10. The positioning printing method according to claim 7, characterized in that, The image acquisition unit and the printing unit are arranged at intervals along the transport direction of the object to be printed, and the image acquisition unit is located upstream of the printing unit; The conveying displacement of the object to be printed along the conveying direction is detected, and the time when the area to be printed on the surface of the object to be printed reaches the printing unit is determined based on the distance between the image acquisition unit and the printing unit along the conveying direction and the conveying displacement. When the area to be printed reaches the printing unit, the printing unit prints the area according to the printing control data.

Images