Positioning method for arc surface screen printing process of mobile phone shell

Abstract

The application relates to the technical field of visual positioning, in particular to a positioning method for a mobile phone shell arc surface screen printing process, which adjusts the installation mode of two cameras, adjusts the position of a matched light source, calibrates the camera and a motion device, collects images by the two cameras, captures feature points, calculates deviation, guides the positioning of the motion device, judges whether alignment is achieved, returns to the previous step if alignment is not achieved, and completes positioning if alignment is achieved. Compared with the prior art, the positioning method for the mobile phone shell arc surface screen printing process decomposes unstable arc surface features into planar linear features, imaging is more stable and reliable, and image processing and target feature capturing are modified from template matching to linear edge feature capturing, which is more stable and reliable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of visual positioning, in particular to a positioning method for a mobile phone shell curved surface screen printing process.

BACKGROUND TECHNIQUE

[0002] The positioning method for the mobile phone shell curved surface in the prior art is as follows: a clamp is installed on a positioning platform, and the mobile phone shell is fixed in an inclined manner. A camera and a light source observe the curved surface of the mobile phone shell from top to bottom, an image processing method of contour matching is adopted, the deviation of the product position from the reference position is calculated, and the positioning platform is guided to complete positioning.

[0003] The prior art has the following defects:

[0004] 1. The 90-degree curved surface has a large height difference, and the depth of field of the existing lens cannot observe a larger area of the curved surface.

[0005] 2. The height difference of the curved surface is large, and the mobile phone product also has a tolerance, and the clamp is placed and fixed manually, which leads to poor consistency of imaging effect, so that the template matching cannot accurately capture the curved surface target, resulting in unstable XYθ.

[0006] 3. The positioning accuracy is difficult to meet the standard, is unstable, and the positioning time is long and the efficiency is low.

SUMMARY OF THE INVENTION

[0007] In order to overcome the above problems, the present application provides a positioning method for a mobile phone shell curved surface screen printing process which can effectively solve the above problems.

[0008] The present application provides a technical solution to solve the above technical problems: a positioning method for a mobile phone shell curved surface screen printing process is provided, comprising the following steps:

[0009] Step S1, adjust the installation mode of the two cameras, and adjust the position of the matching light source;

[0010] Step S2, calibrate the camera and the motion device;

[0011] Step S3, the two cameras collect images, capture feature points, calculate deviations, and guide the motion device to position;

[0012] Step S4, judge whether it is aligned, if not, return to step S3, if aligned, positioning is completed.

[0013] Preferably, in step S1, the following steps are included:

[0014] Step S11, camera A is perpendicular to the mobile phone panel and observes the long side of the mobile phone from front to back;

[0015] Step S12, camera B is perpendicular to the upper side of the mobile phone and observes the short side of the mobile phone from top to bottom;

[0016] Step S13, adjust the image processing method of camera A and camera B to capture the target feature, change from template matching to capture straight line edge feature.

[0017] Preferably, in the step S2, the following steps are included:

[0018] Step S21, the UVW positioning platform returns to zero position, and the Z direction rotation movement axis returns to zero position;

[0019] Step S22, trigger two cameras to collect image to capture edge feature, recorded as OrgLine;

[0020] Step S23, after the UVW positioning platform makes X direction movement, trigger two cameras to collect image to capture edge feature, recorded as XLine;

[0021] Step S24, after the UVW positioning platform makes Y direction movement, trigger two cameras to collect image to capture edge feature, recorded as YLine;

[0022] Step S25, after the UVW positioning platform makes rotation direction movement, trigger two cameras to collect image to capture edge feature, recorded as RLine;

[0023] Step S26, after the Z direction rotation movement axis makes rotation direction movement, trigger two cameras to collect image to capture edge feature, recorded as ZLine;

[0024] Step S27, according to the collected feature edge data, the system carries out calibration.

[0025] Preferably, in the step S3, the following steps are included:

[0026] Step S31, trigger camera A to collect image to capture object edge feature, and calculate Z direction angle and X direction deviation;

[0027] Step S32, trigger camera B to collect image to capture object edge feature, and calculate θ direction angle and Y direction deviation;

[0028] Step S33, according to X direction deviation, Y direction deviation, θ direction angle and Z direction angle, control the movement device to run, so as to realize positioning purpose.

[0029] Preferably, in the step S4, the following steps are included:

[0030] Step S41, judge whether the angle difference between object edge and reference edge in camera A reaches Z precision or not;

[0031] Step S42, judge whether the intersection point distance of the intersection point after the intersection of the diagonal edge and the reference edge with the camera center line in camera A reaches X precision or not;

[0032] Step S43, judging whether the angle difference between the object side and the reference side in the camera B reaches the angle precision theta.

[0033] Step S44, judging whether the intersection distance between the intersection points of the diagonal side and the reference side with the camera center line in the camera B reaches the Y precision.

[0034] Compared with the prior art, the positioning method of the cell phone shell arc surface silk printing process of the application decomposes the unstable arc surface features into planar straight line features; the camera acquisition method used in the application makes the lighting method simpler and the imaging more stable and reliable; the image processing target feature grabbing is modified from template matching to straight line edge feature grabbing, which is more stable and reliable; finally, the arc surface silk printing production efficiency is greatly improved, not only the production precision is improved, but also the positioning time is greatly reduced, and the equipment efficiency is improved. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The overall flowchart of the positioning method of the cell phone shell arc surface silk printing process of the application;

[0036] Figure 2 The step S1 flowchart of the positioning method of the cell phone shell arc surface silk printing process of the application;

[0037] Figure 3 The step S2 flowchart of the positioning method of the cell phone shell arc surface silk printing process of the application;

[0038] Figure 4 The step S3 flowchart of the positioning method of the cell phone shell arc surface silk printing process of the application;

[0039] Figure 5 The step S4 flowchart of the positioning method of the cell phone shell arc surface silk printing process of the application;

[0040] Figure 6 The calibration schematic diagram according to XLine of the positioning method of the cell phone shell arc surface silk printing process of the application;

[0041] Figure 7 The calibration schematic diagram according to YLine of the positioning method of the cell phone shell arc surface silk printing process of the application. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the application more clear, the application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application, and are not used to limit the application.

[0043] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the application are only relative positions on the specified view, and not absolute positions.

[0044] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0045] The positioning method for the curved surface screen printing process of mobile phone shells of the present invention requires a positioning device, including two image acquisition cameras A and B, and a light source matched with the cameras. Both the cameras and the light source are connected to a vision controller. It also includes a motion device, which is a 4-axis adjustment mechanism, including a UVW positioning platform that can realize XYθ movement on the horizontal plane. At the same time, a Z-axis rotational motion axis is installed on the motion plane of the UVW positioning platform, and the fixture is installed on the Z-axis rotational motion axis.

[0046] Please see Figures 1 to 7 The positioning method for the curved surface screen printing process of mobile phone casing of the present invention includes the following steps:

[0047] Step S1: Adjust the mounting method of the two cameras and adjust the position of the matching light source.

[0048] Step S1 includes the following steps:

[0049] Step S11: With camera A perpendicular to the phone panel, observe the long side of the phone from front to back. Here, a backlighting scheme can be used to make the image more stable and clear.

[0050] Step S12: Camera B is perpendicular to the upper side of the phone and observes the short side of the phone from top to bottom. The front lighting scheme is used here, which is more stable and reliable than the existing methods.

[0051] Step S13: Adjust the image processing method for capturing target features by camera A and camera B, changing it from template matching to capturing straight line edge features.

[0052] Backlighting scheme description: Camera A is positioned directly in front of the phone's long side, and a surface light source illuminates the phone from behind towards camera A. The long side of the phone is positioned between camera A and the surface light source. Frontlighting scheme description: The light source is a coaxial light source. Camera B observes the phone's short side through the square aperture of the coaxial light source. Since camera B and the coaxial light source are both on the same side of the phone's short side, this is called front lighting.

[0053] The step S13, the straight line edge feature includes the angle of straight line and the coordinate XY of a point on the straight line, the straight line is composed of many points, we fit the straight line we want by grabbing all the point coordinates, that is the straight line edge feature.

[0054] Step S2, calibrate the camera and the motion device.

[0055] The step S2 includes the following steps:

[0056] Step S21, the UVW positioning platform returns to zero position, the Z direction rotation motion axis returns to zero position;

[0057] Step S22, trigger two cameras to collect image and grab edge feature, marked as OrgLine;

[0058] Step S23, after the UVW positioning platform moves in X direction, trigger two cameras to collect image and grab edge feature, marked as XLine;

[0059] Step S24, after the UVW positioning platform moves in Y direction, trigger two cameras to collect image and grab edge feature, marked as YLine;

[0060] Step S25, after the UVW positioning platform moves in rotation direction, trigger two cameras to collect image and grab edge feature, marked as RLine;

[0061] Step S26, after the Z direction rotation motion axis moves in rotation direction, trigger two cameras to collect image and grab edge feature, marked as ZLine;

[0062] Step S27, according to the collected edge feature data, the system calibrates.

[0063]

XLine

[0064] Fx=Xmm / LxPixel;

[0065] Xmm is the distance of X direction movement of the UVW positioning platform; LxPixel is the distance of the intersection of OrgLine, XLine and the Y midline of camera A pixel coordinate system.

[0066] As shown in Figure 6 , wherein the range in the block is the field of view of the camera; the intersection of OrgLine and Y midline is OP; the intersection of XLine and Y midline is XP; LxPixel=L(OP, XP), L() is the distance operator of two points in space.

[0067] YLine is the straight line edge feature grabbed by camera B when the UVW positioning platform moves in Y direction, which is in translational relationship with its own OrgLine, so the pixel physical movement amount proportion relationship Fy of camera B and platform Y direction can be calculated;

[0068] Fy=Ymm / LyPixel;

[0069] Ymm is the Y direction distance of the UVW positioning platform movement; LyPixel is the distance of the intersection points of OrgLine, YLine and Y midline in camera B pixel coordinate system Y.

[0070] As shown in Figure 7 , wherein the range in the block is the field of view of the camera; the intersection point of OrgLine and Y midline is OP; the intersection point of YLine and Y midline is YP; LyPixel=L(OP, YP), L() is the distance operator of two points in space.

[0071] RLine is the straight line edge feature grabbed by camera B when the UVW positioning platform rotates, which is in rotational relationship with its own OrgLine, and theoretically OrgLine angle-RLine=α degrees (α is the actual rotation angle of the UVW positioning platform); due to engineering errors, the proportion of the angle representation amount of camera B and the actual rotation angle of the UVW positioning platform is Fr;

[0072] Fr=ABS(OrgLine.Angle-Rline.Angle) / α

[0073] In the above formula, ABS() is the absolute value operator; ABS(OrgLine.Angle-RLine.Angle) represents the absolute value of the difference between the OrgLine angle grabbed by camera B and the RLine angle. α is the rotation angle of the UVW positioning platform.

[0074] ZLine is the straight line edge feature grabbed by camera A after the Z direction rotation axis rotates, which is in rotational relationship with its own OrgLine, and theoretically OrgLine angle-ZLine=β degrees (β is the actual rotation angle of the Z direction rotation axis); due to engineering errors, the proportion of the angle representation amount of camera A and the actual rotation angle of the Z direction rotation axis is Fz;

[0075] Fz=ABS(OrgLine.Angle-Zline.Angle) / β

[0076] In the above formula, ABS() is an absolute value operator; ABS(OrgLine. Angle-Zline. Angle) represents the absolute value of the difference between the OrgLine angle captured by the camera A and the ZLine angle. β is the angle of rotation of the Z-rotation axis.

[0077] Step S3, two cameras capture images, capture feature points, calculate deviations, guide the motion device to position.

[0078] In the step S3, the following steps are included:

[0079] Step S31, trigger camera A to capture images to capture the object edge features, calculate the Z-direction angle and the X-direction deviation;

[0080] Step S32, trigger camera B to capture images to capture the object edge features, calculate the θ-direction angle and the Y-direction deviation;

[0081] Step S33, according to the X-direction deviation, the Y-direction deviation, the θ-direction angle and the Z-direction angle, control the motion device to run, realize the positioning purpose.

[0082] In the step S31, the position of the silk screen is fixed, that is, the mobile phone is adjusted to a fixed position by the motion device, which is called the reference position, and there is a reference straight line edge corresponding to the reference position. The Z-direction angle is the angle of the reference straight line edge minus the angle of the captured object straight line edge; the X-direction deviation is the straight line distance between PO1 and PS1, which are the intersection points of the reference straight line edge and the object straight line edge with the Y-midline of the camera (i.e. the angle is 0, the straight line passing through the point (0, 512), calculated based on the 130W pixel camera 1280*1024 resolution).

[0083] In the step S32, similar to the case in step S31, camera B also has a reference straight line. The θ-direction angle is the difference between the angle of the object straight line and the angle of the reference straight line; the Y-direction deviation is the straight line distance between PO2 and PS2, which are the intersection points of the reference straight line edge and the object straight line edge with the X-midline of the camera (i.e. the angle is 0, the straight line passing through the point (640, 0), calculated based on the 130W pixel camera 1280*1024 resolution).

[0084] Step S4, determine whether it is aligned, if not, return to step S3, if aligned, the positioning is completed.

[0085] In the step S4, the following steps are included

[0086] Step S41, determine whether the angle difference between the object edge and the reference edge in camera A reaches the Z-precision;

[0087] Step S42, judging whether the intersection distance of the diagonal edge and the reference edge, both of which are intersected with the camera center line, reaches X precision in the camera A;

[0088] Step S43, judging whether the angle difference of the object edge and the reference edge reaches θ precision in the camera B;

[0089] Step S44, judging whether the intersection distance of the diagonal edge and the reference edge, both of which are intersected with the camera center line, reaches Y precision in the camera B.

[0090] The object edge is the product edge newly put into the adjustment; and the reference edge is the straight line edge of the silk printing fixed position.

[0091] The X and Y precisions are within ±30 microns, and the Z and θ precisions are within ±0.05 degrees.

[0092] Compared with the prior art, the positioning method of the mobile phone shell arc surface silk printing process of the present application decomposes the unstable arc surface features into planar straight line features; the camera collection method used in the present application makes the lighting method simpler and the imaging more stable and reliable; the image processing target feature grabbing is modified from the template matching to the straight line edge feature grabbing, which is more stable and reliable; finally, the arc surface silk printing production efficiency is greatly improved, not only the production precision is improved, but also the positioning time is greatly reduced, and the equipment efficiency is improved.

[0093] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application, and any modification, equivalent replacement and improvement within the concept of the present application shall be included in the patent protection scope of the present application.

Claims

1. A positioning method for screen printing on the curved surface of a mobile phone casing, characterized in that, Includes the following steps: Step S1: Adjust the mounting method of the two cameras and adjust the position of the matching light source; Step S1 includes the following steps: Step S11: Camera A is perpendicular to the phone panel, and the long side of the phone is observed from front to back; Step S12: Camera B is perpendicular to the top side of the phone, observing the short side of the phone from top to bottom; Step S13: Adjust the image processing method for capturing target features by camera A and camera B, changing it from template matching to capturing straight line edge features; Step S2: Calibrate the camera and motion device; Step S2 includes the following steps: Step S21: The UVW positioning platform returns to the zero position, and the Z-axis rotation axis returns to the zero position. Step S22: Trigger the two cameras to capture images and extract edge features, which are denoted as OrgLine; Step S23: After the UVW positioning platform moves in the X direction, it triggers the two cameras to acquire images and capture the edge features, which are recorded as XLine. Step S24: After the UVW positioning platform moves in the Y direction, it triggers the two cameras to acquire images and capture the edge features, which are recorded as YLine. Step S25: After the UVW positioning platform rotates, it triggers the two cameras to capture images and capture the edge features, which are recorded as RLine. Step S26: After the Z-axis rotational motion is rotated, the two cameras are triggered to capture images and the edge features are recorded as ZLine. Step S27: The system performs calibration based on the collected feature edge data; Step S3: The two cameras acquire images, capture feature points, calculate the deviation, and guide the motion device to position itself. Step S4: Determine if the alignment is correct. If not, return to step S3 to complete the alignment.

2. The positioning method for the curved surface screen printing process of a mobile phone casing as described in claim 1, characterized in that, Step S3 includes the following steps: Step S31: Trigger camera A to acquire images and capture object edge features, and calculate the Z-direction angle and X-direction deviation; Step S32: Trigger camera B to acquire images and capture object edge features, and calculate the θ-direction angle and Y-direction deviation; Step S33: Control the motion device to operate based on the X-direction deviation, Y-direction deviation, θ-direction angle, and Z-direction angle to achieve the positioning purpose.

3. The positioning method for the curved surface screen printing process of a mobile phone casing as described in claim 1, characterized in that, Step S4 includes the following steps Step S41: Determine whether the angle difference between the object side and the reference side in camera A reaches the Z precision. Step S42: Determine whether the distance between the intersection points of the diagonal side and the reference side of camera A and the centerline of the camera reaches the precision X. Step S43: Determine whether the angle difference between the object side and the reference side in camera B reaches the accuracy θ. Step S44: Determine whether the distance between the intersection points of the diagonal side and the reference side of camera B and the centerline of the camera reaches the Y precision.

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