Three-dimensional high-precision fixed-point printing method and device

Abstract

This invention discloses a method and apparatus for three-dimensional high-precision fixed-point printing. The printer prints a specified calibration pattern on the printing bed. A 3D camera is used to capture a two-dimensional image and a 3D point cloud. The camera and printer are calibrated to obtain a transformation matrix between the printer coordinate system and the camera coordinate system. The point cloud in the camera coordinate system is converted to the printer coordinate system based on external parameters. The printing mechanism of the printing device performs printing function according to the coordinate parameters provided by the computer vision mechanism. According to the user's printing needs, the 3D coordinates are converted to the printer coordinate system to accurately print at the target position. The pattern can be flexibly printed on the target object according to the actual position of the target object, eliminating the need for manual measurement and adjustment, significantly improving speed and accuracy. Furthermore, if the printer encounters a positioning error, the device can automatically detect the error and prevent losses due to operation under the error condition.

Description

[Technical Field]

[0001] The present application relates to the field of three-dimensional printing technology, and more particularly to a method and apparatus for three-dimensional high-precision fixed-point printing. [Background technology]

[0002] Conventional printers can achieve relatively high positioning accuracy within their own printing coordinate system, but cannot print accurately within the world coordinate system. This is due to problems with the printing positioning principle.

[0003] The two coordinate systems that determine the actual printing position are the printer operating range coordinate system and the print target coordinate system.

[0004] The printer operating range coordinate system refers to the printer's mechanical starting position (x0, y0, z0) to (xMax, yMax, zMax). Under the same operating conditions, the printer can repeatedly position itself with high accuracy within its own coordinate system. However, after long-term operation, positioning errors may occur in the X, Y, and Z axes. These errors can be caused by mechanical wear, aging, or soiling of the positioning device. For example, the grid commonly used in industry for X-axis positioning can easily become contaminated by ink splashes or dust, resulting in positioning errors. In such a situation, changes occur in the printer operating range coordinate system, causing printing positioning errors and preventing normal operation.

[0005] The target coordinate system refers to the coordinate system of the object being printed. Taking an A4 sheet of paper as an example, it runs from the upper left corner (x0, y0) (the z-axis is fixed and not limited here) to the lower right corner (xMax, yMax). The target coordinate system and the printer operating area coordinate system are obviously not the same coordinate system. In conventional printing systems, the target coordinate system does not exist or is implicitly assumed to be perfectly aligned with the printer operating area coordinate system. The positioning and layout of conventional print data are determined entirely based on the printer operating area coordinate system. Therefore, in actual operation, the paper is positioned using supporting alignment marks to ensure the relative accuracy of the printing position. The accuracy of such printing position is very low and is determined by the correspondence between the two coordinate systems when the target (paper) is positioned. The closer the correspondence, the higher the positioning accuracy. Summary of the Invention [Problem to be solved by the invention]

[0006] From the above description, the problems with conventional printing system registration become apparent.

[0007] Problem 1: It is difficult for printers to print the same pattern in the same position on different printing objects.

[0008] Problem 2: If a printer hardware problem causes a positioning error, it will directly cause a printing error.

[0009] While the above problem is acceptable to some extent in the traditional printing scene, it becomes a serious problem in the nail art scene. Users will never accept that nail art effects are printed on parts other than the nail. For this reason, the printing system requires extremely high positioning accuracy within the world coordinate system. [Means for solving the problem]

[0010] To solve the above technical problems, the present invention provides a three-dimensional high-precision fixed-point printing method, which first installs a computer vision system above the printing system and also installs several specific marking points on the top of the print carriage to support print carriage positioning by the 3D camera. A 3D camera coordinate system is introduced to unify the coordinate systems of the entire system. The relationship between the three coordinate systems is as follows: the 3D camera coordinate system includes the printer working range coordinate system, and the printer working range coordinate system includes the printing target coordinate system. The above three-dimensional high-precision fixed-point printing method is performed by a printer and includes the following steps:

[0011] S1: The printer prints the specified calibration pattern on the printing bed.

[0012] S2: Take a photo using a 3D camera to obtain two-dimensional images and 3D point clouds.

[0013] S3: Calibrate the camera and printer to obtain a transformation matrix between the printer coordinate system and the camera coordinate system.

[0014] S4: Based on the external parameters, the point cloud in the camera coordinate system is transformed into the printer coordinate system.

[0015] Preferably, the specific steps of the printer calibration method are as follows:

[0016] 1): Manually place the proof paper into the printer.

[0017] 2): Move the printer to the machine's starting position and stop it.

[0018] 3): Photographed by a 3D camera, the position T1 in the 3D coordinate system of the carriage is identified by a mark point on the top of the printing carriage, where T1 is the starting position of printing.

[0019] 4): The printer starts printing a specific pattern.

[0020] 5): Take a picture with a 3D camera, identify the printed pattern, and at the same time, identify the complete pattern. Use the pattern data to calculate the coordinate transformation matrix A according to the external parameters of the camera.

[0021] 6): Calibration is completed.

[0022] Preferably, the specific steps of the printer calibration self-diagnosis method are as follows:

[0023] 1): Move the print carriage to the print start position and stop it.

[0024] 2): Photographed by a 3D camera, the position nT1 of the carriage in the 3D coordinate system is identified by a mark point on the top of the print carriage.

[0025] 3): Compare nT1 with T1 recorded in the shipping calibration, and perform maintenance action if the difference between the two exceeds a predetermined threshold.

[0026] 4) After the maintenance operation is completed, perform the calibration self-diagnosis again. If it fails again, set the machine to fault status and have the repair person handle it.

[0027] Preferably, the printer has three degrees of freedom, being movable in the X, Y and Z axes, and the printing bed plane is parallel to the plane of the nozzles of the inkjet printer.

[0028] Preferably, the calibration pattern in S1 includes a checkerboard or a dot pattern.

[0029] Preferably, in step S2, the printer prints when the Z-axis coordinate is 0, and the printer initial position coordinates (x=0, y=0, z=0) are set as the origin of the printer coordinate system.

[0030] According to the three-dimensional high-precision fixed-point printing device, the printing mechanism in the printing device performs the printing function according to the coordinate parameters provided by the computer vision mechanism, and includes a frame, on which a computer vision mechanism, a hand placement groove and a printing mechanism are mounted, and the computer vision mechanism is installed directly above the hand placement groove.

[0031] Preferably, the computer vision mechanism comprises a camera, a structured light component, a vision control module, an auxiliary lighting component, and a movement module.

[0032] Preferably, the printing mechanism is connected to an X-axis movement module, a Y-axis movement module and a Z-axis movement module, and the printing mechanism moves in the X-axis, Y-axis and Z-axis directions.

[0033] Preferably, the X-axis moving module includes a drive motor, the drive motor is connected to a drive wheel, the drive wheel is connected to a driven wheel via a transmission belt, and the driven wheel is attached to the other end of the frame.

[0034] Preferably, an ink absorbing unit is attached to a portion of the frame below the printing mechanism, the ink absorbing unit including an ink absorbing sponge and a sponge bracket, the sponge bracket being fixed to the bracket.

[0035] Preferably, an ink receiving box is attached to one side of the ink absorbing unit, and an opening is provided at the top of the ink receiving box, and a through hole is provided at the bottom of the ink receiving box. [Effects of the Invention]

[0036] The technical effects and advantages of the present invention are as follows:

[0037] According to the user's printing needs, 3D coordinates can be converted into the printer coordinate system to accurately print at the target position, and patterns can be flexibly printed on the target object according to the target object's actual position, eliminating the need for manual measurement and adjustment, greatly improving speed and accuracy. Calibration and self-diagnosis effectively prevent user losses caused by positioning errors that occur during nail art. In addition, if a positioning error occurs in the printer, the device will automatically detect the error and prevent losses caused by operation under the error state. [Brief explanation of the drawings]

[0038] [Figure 1] FIG. 1 is a schematic diagram showing the structure of calibration in the three-dimensional high-precision fixed-point printing method provided in the embodiment of the present application. [Figure 2] 1 is a schematic diagram showing the structure of a three-dimensional high-precision fixed-point printing device provided in an embodiment of the present application. [Figure 3] 3 is an enlarged schematic diagram showing the structure of part A in FIG. 2 in a three-dimensional high-precision fixed-point printing device provided in an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0039] The present invention will now be described in more detail with reference to the drawings and specific embodiments. The examples of the present invention are provided for purposes of illustration and description and are not intended to be exhaustive or to limit the invention to the disclosed form. Many modifications and variations will be apparent to those skilled in the art. The selection and description of the examples is intended to better explain the principles and practical applications of the present invention and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for particular applications.

[0040] Referring to FIG. 1, this embodiment provides a three-dimensional high-precision fixed-point printing method, which is implemented by a printer.

[0041] The printer has three degrees of freedom, it can move in the X, Y and Z axes, and the printing bed plane is parallel to the plane of the inkjet printer nozzle.

[0042] It includes the following steps:

[0043] S1: The printer prints the specified calibration pattern on the printing bed.

[0044] Here, the calibration pattern includes a checkerboard or a dot pattern.

[0045] The printer prints when the Z-axis coordinate is 0, and the printer initial position coordinates (x=0, y=0, z=0) are set as the origin of the printer coordinate system.

[0046] The calibration pattern is A6 size and contains 44 circles, the relative coordinates of the center of each circle are known, as shown in Figure 1. The coordinates of the points in the printer coordinate system are (xp1, yp1, zp1) to (xp44, yp44, zp44).

[0047] The coordinates of the center of each printed circle are known in the printer coordinate system.

[0048] S2: Photograph using a 3D camera to obtain two-dimensional images (grayscale or color) and a 3D point cloud.

[0049] S3: Calibrate the camera and printer to obtain the transformation matrix between the printer coordinate system and the camera coordinate system (the relationship between the rotation and translation of the external parameters).

[0050] The center of each circle in the 2D image can be found and detected using findCirclesGrid or SimpleBlobDetector in the OpenCV vision library. Note that there may be a point cloud for that pixel point at the corresponding pixel point. In the camera coordinate system, the coordinates are taken to be (xc1, yc2, zc2) to (xc1, yc2, zc2). Since there may not be a point cloud for that point, a threshold T is set to 40, and the number of detected circle centers is set to 0 to 44. For calibration accuracy, if the number of detected point cloud coordinates is greater than T, proceed to the next calculation step and obtain the extrinsic parameters using the PNP solution.

[0051] S4: Based on the external parameters, the point cloud in the camera coordinate system is transformed into the printer coordinate system.

[0052] The projection equation of the three-dimensional high-precision fixed-point printing method of the present invention is as follows:

number

[0053] Here, K is the internal parameter matrix of the camera, which is known.

[0054] Based on the external parameters, the point cloud in the camera coordinate system is transformed into the printer coordinate system.

[0055] After converting the 3D point cloud into the printer coordinate system, each point cloud is converted to the printing plane.

[0056] The actual printed dimensions of an image are determined by both the pixels and resolution of the image. Pixels refer to the small color dots that make up an image, and resolution (in DPI units) refers to the number of pixels per inch, which can be thought of as the distribution density of these small color dots. For the same number of pixels, the higher the resolution, the greater the pixel density, which results in a smaller actual printed dimension and a more detailed image.

[0057] Actual dimensions (inches) = pixels / resolution, where 1 inch = 2.54 centimeters. For example, if an image is 600 pixels wide and the resolution is 300, the actual print width will be 600 / 300 = 2 inches, or about 5 centimeters.

[0058] Based on the above formula, if we don't consider the z-axis, we can convert the points in the printer coordinate system to the image's pixel coordinate system (with u representing the horizontal direction and v representing the vertical direction). If the coordinates of one point are (25.4mm, 250.4mm, Z), then u = (25.4 / 25.4) * 300 = 300, and v = (250.4 / 25.4) = 3000. Therefore, in the image coordinate system, the pixel coordinates of that point are (300, 3000).

[0059] Here, the factory calibration is used to determine the transformation relationship between the 3D camera coordinate system and the printing coordinate system. The specific steps of the printer calibration method are as follows:

[0060] 1): Manually place the proof paper into the printer.

[0061] 2): Move the printer to the machine's starting position and stop it.

[0062] 3): Photographed by a 3D camera, the position T1 in the 3D coordinate system of the carriage is identified by a mark point on the top of the printing carriage, where T1 is the starting position of printing.

[0063] 4): The printer starts printing a specific pattern.

[0064] 5): Take a picture with a 3D camera, identify the printed pattern, and at the same time, identify the complete pattern. Use the pattern data to calculate the coordinate transformation matrix A according to the external parameters of the camera.

[0065] 6): Calibration is completed. Through the factory calibration, the transformation matrix A between the printer working range coordinate system and the 3D camera coordinate system is obtained.

[0066] Nail art process

[0067] 1: Take a picture with a 3D camera and use a series of algorithms to obtain the coordinate B of the nail in the 3D camera coordinate system.

[0068] 2: Then, coordinate B is transformed into coordinate C in the printer operation range coordinate system using transformation matrix A.

[0069] 3: Send coordinate C to the printer and execute the printing operation.

[0070] Calibration self-diagnosis

[0071] To ensure accurate positioning for every nail art operation, the system can perform calibration self-diagnosis according to needs to detect positioning failures caused by various reasons.

[0072] 1): Move the print carriage to the print start position and stop it.

[0073] 2): Photographed by a 3D camera, the position nT1 of the carriage in the 3D coordinate system is identified by a mark point on the top of the print carriage.

[0074] 3): Compare nT1 with T1 recorded in the shipping calibration, and perform maintenance action if the difference between the two exceeds a predetermined threshold.

[0075] 4) After the maintenance operation is completed, perform the calibration self-diagnosis again. If it fails again, set the machine to fault status and have the repair person handle it.

[0076] The calibration self-diagnosis can effectively prevent the user from being harmed by positioning errors that may occur due to various reasons during nail art.

[0077] As shown in FIG. 2, this embodiment provides a three-dimensional high-precision fixed-point printing device, in which the printing mechanism of the printing device performs printing function according to coordinate parameters provided by a computer vision mechanism 2. It includes a frame 1, on which a computer vision mechanism 2 is attached, which is installed directly above a hand placement groove 3. The computer vision mechanism 2 is composed of a camera, a structured light component, a vision control module, an auxiliary lighting component, and a movement module. Two cameras are installed on the left and right, and they take photos. The structured light component and auxiliary lighting component are used to support the cameras and improve shooting accuracy. The computer vision mechanism 2 processes the captured photos using an algorithm to calculate point cloud information in the three-dimensional space of the hand. The height and tilt angle of each finger are further calculated based on the point cloud, allowing the hand placement groove 3 to perform adjustments.

[0078] A printing mechanism 4 is attached to the side edge of the computer vision mechanism 2 of the frame 1. The printing mechanism 4 is connected to an X-axis movement module, a Y-axis movement module, and a Z-axis movement module, allowing it to move in the X-axis, Y-axis, and Z-axis directions. The printing mechanism 4 includes a printing nozzle module 401, which includes a printing nozzle and a housing. The printing nozzle is connected to a raw material chamber via an ink passage, which is used to store ink. A flexible sensor 402 is attached to the side wall of the housing. The X-axis movement module includes a driving motor 403, which is connected to a driving wheel 404, which is connected to a driven wheel 5 via a transmission belt. The driven wheel 5 is attached to the other end of the frame 1 and drives the driving motor 403 to rotate the driving wheel 404. The transmission belt rotates the driven wheel 5, causing the printing nozzle module 401 to move along the X-axis direction. The rear of the printing nozzle module 401 is connected to the Y-axis movement module, which is an elevation module that moves the printing nozzle module 401 up and down and adjusts the height of the printing nozzle module 401. The combined structure of the X-axis movement module, Y-axis movement module, and printing nozzle module 401 is connected to the Z-axis movement module 406. The Z-axis movement module 406 is a lead screw module that is driven by a servo motor to move the X-axis movement module, Y-axis movement module, and printing nozzle module 401 back and forth.

[0079] Furthermore, an ink absorption unit 7 is attached to the frame 1 below the printing mechanism 4, and includes an ink absorption sponge and a sponge bracket. The sponge bracket is fixed to the bracket 1. The ink absorption sponge is kept moist, and when the printing nozzle module 401 is not in use, the bottom of the nozzle is in close contact with the ink absorption sponge, thereby keeping the nozzle constantly wet and preventing the nozzle from drying out due to exposure to the environment. An ink receiving box 6 is attached to one side of the ink absorption unit 7, and an opening is provided at the top of the ink receiving box 6 and a through-hole is provided at the bottom of the ink receiving box 6. Before operating the print nozzle module 401, the Z-axis movement module 406 is driven to move the print nozzle module 401 above the ink receiving box 6, the Y-axis movement module 405 is driven to move the print nozzle module 401 downward so that the nozzle enters the ink receiving box 6 and the print nozzle module 401 is operated to eject ink from the nozzle, the Y-axis movement module 405 is driven to lift the print nozzle module 401, and the drive motor 403 is driven to rotate the drive wheel 404 and driven wheel 5 so that the print nozzle module 401 moves above the hand placement slot 3. A printing process is performed on the nail placed in the hand placement slot 3, and after the printing operation is completed, the X-axis movement module, Y-axis movement module 405, and Z-axis movement module 406 are driven to return the print nozzle module 401 to its origin.

[0080] In this invention, 3D coordinates are converted into the printer coordinate system according to the user's printing needs, allowing for accurate printing at the target position, and patterns can be flexibly printed on the target according to the actual position of the target, eliminating the need for manual measurement and adjustment, thereby significantly improving speed and accuracy.

[0081] Apparently, the described embodiments are only some of the embodiments of the present invention and do not cover all the embodiments. All other embodiments that can be obtained by a person skilled in the art or with ordinary technical knowledge in the relevant field based on the embodiments of the present invention without any creative efforts fall within the scope of protection of the present invention. Structures, devices, or operation methods not specifically described or explained in the present invention are implemented according to ordinary means in the relevant field unless otherwise specified or limited. [Explanation of symbols]

[0082] 1: Frame 2: Computer Vision Mechanism 3: Hand placement groove 4: Printing mechanism 401: Printing nozzle module 402: Flexible sensor 403: Drive motor 404: Drive wheel 405: Y-axis movement module 406: Z-axis movement module 5: Driven wheel 6: Ink receiving box 7: Ink absorption unit

Claims

1. S1: The printer prints a specified calibration pattern on the printing bed; S2: Taking a photograph using a 3D camera to obtain a two-dimensional image and a 3D point cloud; S3: Calibrate the camera and the printer to obtain a transformation matrix between the printer coordinate system and the camera coordinate system; S4: Transforming the point cloud in the camera coordinate system into the printer coordinate system based on the external parameters; Three-dimensional high-precision fixed-point printing method.

2. The specific steps of the printer calibration method are as follows: 1): Manually placing a proof sheet into the printer; 2): Move the printer to the machine's starting position and stop it; 3): Taking a picture with a 3D camera, identify the position T1 in the 3D coordinate system of the carriage by a mark point on the top of the print carriage, where T1 is the starting position of printing; 4): The printer starts printing a specific pattern; 5) Taking a picture with a 3D camera, identifying the printed pattern and at the same time identifying the complete pattern, and using the pattern data to calculate a coordinate transformation matrix A according to the external parameters of the camera; 6): Calibration is completed, The three-dimensional high-precision fixed-point printing method according to claim 1.

3. The specific steps of the printer calibration self-diagnosis method are as follows: 1): Moving the print carriage to the print start position and stopping it; 2): Identifying the position nT1 in the 3D coordinate system of the carriage by a mark point on the top of the print carriage photographed by a 3D camera; 3): Comparing nT1 with T1 recorded in the shipping calibration, and performing maintenance operations if the difference between them exceeds a predetermined threshold; 4) After the maintenance operation is completed, perform the calibration self-diagnosis again, and if it fails again, set the machine to a fault state and have the repair person handle it. The three-dimensional high-precision fixed-point printing method according to claim 1.

4. the printer has three degrees of freedom, moving in the X, Y and Z axes, and the printing bed plane is parallel to the plane of the inkjet printer nozzles; The three-dimensional high-precision fixed-point printing method according to claim 1.

5. In the step S1, the calibration pattern includes a checkerboard or a dot pattern; The three-dimensional high-precision fixed-point printing method according to claim 1.

6. In step S2, the printer prints when the Z-axis coordinate is 0, and the printer initial position coordinates (x=0, y=0, z=0) are set as the origin of the printer coordinate system. The three-dimensional high-precision fixed-point printing method according to claim 1.

7. An apparatus using the three-dimensional high-precision fixed-point printing method according to any one of claims 1 to 6, The printing mechanism of the device performs printing function according to coordinate parameters provided by a computer vision mechanism (2), and includes a frame (1), to which a computer vision mechanism (2), a hand placement groove (3) and a printing mechanism (4) are attached, and the computer vision mechanism (2) is installed directly above the hand placement groove (3); 3D high precision fixed point printing device.

8. The computer vision mechanism (2) is composed of a camera, a structured light component, a vision control module, an auxiliary lighting component and a movement module; The three-dimensional high-precision fixed-point printing device according to claim 7.

9. The printing mechanism (4) is connected to an X-axis moving module, a Y-axis moving module and a Z-axis moving module, and moves in the X-axis, Y-axis and Z-axis directions. The three-dimensional high-precision fixed-point printing device according to claim 8.

10. The X-axis moving module includes a driving motor (403), the driving motor (403) is connected to a driving wheel (404), the driving wheel (404) is connected to a driven wheel (5) via a transmission belt, and the driven wheel (5) is attached to the other end of the frame (1); The three-dimensional high-precision fixed-point printing apparatus according to claim 9.

11. An ink absorbing unit (7) is attached to a portion of the frame (1) below the printing mechanism (4), and the ink absorbing unit (7) includes an ink absorbing sponge and a sponge bracket, and the sponge bracket is fixed to the bracket (1). The three-dimensional high-precision fixed-point printing device according to claim 10.

12. An ink receiving box (6) is attached to one side of the ink absorbing unit (7), and an opening is provided at the top of the ink receiving box (6) and a through hole is provided at the bottom of the ink receiving box (6). The three-dimensional high-precision fixed-point printing apparatus according to claim 11.

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