Method, device, equipment and medium for measuring displacement field and strain field of screen surface

Abstract

This invention provides a method, apparatus, device, and medium for measuring the displacement and strain fields of a screen surface, relating to the field of screen measurement technology. The measurement method includes steps S1 to S6. S1: Pre-processing the TFT-LCD screen to coat its surface with a randomly distributed speckle pattern. S2: Placing the TFT-LCD screen sample on a stage. S3: Adjusting the initial position of the indenter of the universal testing machine, setting the indenter's descent rate, and the pressing plan. S4: Debugging the three-dimensional digital image correlation measurement system and performing a compression test on the TFT-LCD screen to obtain test data. S5: Calibrating the CCD camera of the three-dimensional digital image correlation measurement system to obtain the transformation model between the world coordinate system and the camera coordinate system. S6: Calculating the displacement and strain fields of the TFT-LCD screen under external load based on the test data and the transformation model.

Description

Technical Field

[0001] The present invention relates to the field of screen measurement technology, and in particular to a method, device, equipment and medium for measuring displacement field and strain field on a screen surface. Background Art

[0002] TFT-LCD (Thin Film Transistor Liquid Crystal Display) has a wide range of applications, such as mobile devices, televisions, and computer monitors, and its mechanical properties have a direct impact on user experience. However, current research on the mechanical properties of TFT-LCD mainly relies on experimental testing and numerical simulation. The experimental measurement method usually uses contact measurement, which has the problems of non-full-field measurement, non-real-time monitoring, and restrictions on sample size and shape, making it difficult to meet certain testing requirements. In addition, although the numerical simulation method can provide theoretical support, it requires powerful computer hardware support for the complex TFT-LCD screen model, and may produce errors because the model cannot fully reflect the complexity and uncertainty of the actual system, so reliable experimental data is needed as a basis.

[0003] Existing surface mechanics measurement methods are mainly divided into two categories: contact and non-contact. Contact measurement methods, such as mechanical instruments and scanning probes, can measure the extrusion displacement of the TFT-LCD screen surface, but due to its insufficient full-field measurement characteristics and susceptibility to rigid body displacement, errors will be caused in the measurement results. Non-contact measurement methods, including interferometric measurement technology and non-interferometric technology, have lower requirements on light sources, a wider range of applications, and reduce the impact of external factors on measurement results. However, interferometric measurement technologies such as holographic interferometry and speckle interferometry usually require the use of coherent light sources, complex optical paths, and are easily disturbed by environmental factors such as external vibrations, which limits their scope of application.

[0004] As a non-interference, non-contact, full-field observation technology, digital image correlation has been deeply studied and applied in the fields of material mechanics, structural engineering, biomechanics, etc. However, this technology still faces challenges in the measurement of mechanical properties of TFT-LCD screens, especially in achieving full-field, real-time monitoring and improving measurement accuracy. Therefore, it is necessary to develop a new measurement method to overcome the shortcomings of existing technologies and provide more accurate and comprehensive measurement of mechanical properties of TFT-LCD screens. Summary of the invention

[0005] The present invention provides a method, device, equipment and medium for measuring displacement field and strain field on a screen surface, so as to improve at least one of the above-mentioned technical problems.

[0006] In a first aspect, the present invention provides a method for measuring displacement field and strain field on a screen surface, which comprises steps S1 to S6.

[0007] S1. Pre-processing the TFT-LCD screen to cover a layer of randomly distributed speckle pattern on its surface.

[0008] S2. Place the TFT-LCD screen sample on the stage.

[0009] S3. Adjust the initial position of the pressure head of the universal material testing machine, set the pressure head drop rate, and the pressure plan.

[0010] S4. Debug the three-dimensional digital image correlation measurement system, and perform extrusion test on the TFT-LCD screen to obtain test data.

[0011] S5. Calibrate the CCD camera of the three-dimensional digital image correlation measurement system to obtain a conversion model between the world coordinate system and the camera coordinate system.

[0012] S6. Calculate the displacement field and strain field of the TFT-LCD screen under the action of external load according to the test data and the conversion model.

[0013] In an optional implementation, step S1 specifically includes steps S11 to S13.

[0014] S11. Apply a layer of white matte paint on the surface of the TFT-LCD screen to serve as the background color.

[0015] S12. Wait for the white matte paint layer to evaporate and obtain a stable base color.

[0016] S13. Spray black matte paint evenly on the screen surface to form granular randomly distributed spots, wherein the size of each spot is 2 pixels.

[0017] In an optional implementation, step S2 specifically includes step S21 to step S22.

[0018] S21, placing the pre-processed TFT-LCD screen on a stage, wherein the stage is hollowed out in the center, and the hollowed-out diameter is 30 mm.

[0019] S22. Place carrier blocks on both side edges of the TFT-LCD screen to fix the screen and prevent it from sliding.

[0020] In an optional implementation, step S3 specifically includes steps S31 to S34.

[0021] S31, determining the application position of the external load, and moving the TFT-LCD screen to the corresponding position.

[0022] S32, lift the indenter of the universal material testing machine to the external load action area observable by the three-dimensional DIC measurement system, and set the current position as the initial position. The indenter of the testing machine adopts a rigid indenter or a soft indenter.

[0023] S33. Set the drop rate of the indenter of the universal material testing machine to within 30 mm / min.

[0024] S34, when the pressure head contacts the TFT-LCD screen, it stays for 5 seconds and then returns to the initial position.

[0025] In an optional implementation, step S4 specifically includes steps S41 to S43.

[0026] S41. Align the intersection of the camera optical axes of the 3D DIC measurement system with the pressing center of the indenter, and ensure that all CCD cameras can capture the affected area of ​​the TFT-LCD screen.

[0027] S42, adjusting the aperture and focal length of the CCD camera so as to present a clear target area in the image processing program. The CCD camera is connected to the computer through a data transmission line and a synchronous trigger and the image acquisition software is started.

[0028] S43, turning on the switch on the test machine control panel to apply a load, and performing an extrusion test on the TFT-LCD screen under the action of the load.

[0029] In an optional implementation, step S5 specifically includes steps S51 to S53.

[0030] S51. Allow the CCD camera to collect images from eight calibration plates in different orientations.

[0031] S52, calibrate the CCD camera according to the content captured by the CCD camera, and establish a conversion model between the world coordinate system and the camera coordinate system. The conversion model is:

[0032] ;

[0033] In the formula, is the relevant proportionality coefficient, and are the coordinates of the two directions in the camera coordinate system, and are the pixel sizes in two directions in the camera coordinate system, , are the horizontal and vertical coordinates of the image center in the camera coordinate system, is the focal length of the camera, The rotation matrix from the world coordinate system to the built camera coordinate system, is the translation vector from the world coordinate system to the camera coordinate system, , and They are the coordinates of the three directions in the world coordinate system.

[0034] S53. Based on the conversion model, the two-dimensional coordinates in the camera can be restored to three-dimensional coordinates in the world coordinate system by performing matching calculations using image processing software.

[0035] In an optional implementation, step S6 specifically includes steps S61 to S66.

[0036] S61 , taking the image of the initial state of the TFT-LCD screen captured by the CCD camera as a reference image, and taking the image after the load is applied as a target image.

[0037] S62. Select a region of interest where the indenter acts on an image processing program on a computer.

[0038] S63, determine the relevant calculation sub-area, determine the target area at the corresponding position in the target image, set the reference point on the area of ​​interest The coordinates of , target point on the region of interest The coordinates of , the reference point on the target area The coordinates of , the target point is at the target corresponding point on the target area The coordinates of .

[0039] Reference Points and target point The relationship between them, and the reference point Corresponding point to the target It can be expressed as:

[0040] ;

[0041] In the formula, As reference point and target point Between Distance of direction, As reference point and target point Between Distance of direction, As reference point Corresponding point to the target Between Distance of direction, As reference point Corresponding point to the target Between Distance in direction.

[0042] The reference point and the target point are spread into the reference area and the target area, and the relationship between the reference area and the target area can be expressed as:

[0043] ;

[0044] ;

[0045] In the formula, represents the region of interest of the reference image, is the gray value distribution function of the reference area, Represents the target area, is the gray value distribution function of the target area, is the deformation mapping function, is the deformation parameter.

[0046] S64. Based on the zero-mean normalized minimum distance square criterion, correlation calculation is performed using images taken by the CCD camera before and after the load is applied:

[0047] ;

[0048] In the formula, is the correlation coefficient, is the boundary range of the area of ​​interest, for The target point number of the direction, for The target point number of the direction, The target point is The coordinates of the direction, The target point is The coordinates of the direction, is the value of the target point, is the mean of all target points in the region of interest on the reference image, The target corresponding point is The coordinates of the direction, The target corresponding point is The coordinates of the direction, is the value of the target corresponding point, is the mean of all target corresponding points in the target area.

[0049] S65. The position with the smallest correlation coefficient after the full-field search is the position where the target area is most likely to move to after deformation. The displacement vector of the reference point under the action of external force can be obtained by calculating the coordinate difference between the front and rear positions. .in, , for Displacement in direction, for Displacement in direction.

[0050] S66. Calculate the displacement information and strain information of the region of interest according to the displacement vector.

[0051] Step S66 includes step S661 to step S662.

[0052] S661. Calculate the gradient of the displacement according to the displacement vector , express exist The rate of change of direction, express exist The rate of change of direction, express exist The rate of change of direction, express exist The rate of change of direction. The rate of change is the degree of deformation of the object in different directions.

[0053] S662: Calculate the strain tensor according to the gradient , Indicates transpose. After expansion, the components are:

[0054] ;

[0055] ;

[0056] ;

[0057] in, for The normal strain in the x-direction represents tension or compression. for The normal strain in the y direction represents the tension or compression. is the shear strain, which represents the in-plane shear deformation.

[0058] In a second aspect, the present invention provides a device for measuring displacement field and strain field on a screen surface, which includes a preprocessing module, a placement module, a setting module, a debugging module, a calibration module and a calculation module.

[0059] The pre-processing module is used for pre-processing the TFT-LCD screen so as to cover a layer of randomly distributed speckle pattern on the surface of the screen.

[0060] The placement module is used to place the TFT-LCD screen sample on the stage.

[0061] The setting module is used to adjust the initial position of the pressure head of the universal material testing machine, set the pressure head drop rate, and the pressure plan.

[0062] The debugging module is used to debug the 3D digital image correlation measurement system and perform extrusion test on the TFT-LCD screen to obtain test data.

[0063] The calibration module is used to calibrate the CCD camera of the three-dimensional digital image correlation measurement system and obtain the conversion model between the world coordinate system and the camera coordinate system.

[0064] The calculation module is used to calculate the displacement field and strain field of the TFT-LCD screen under the action of external load according to the test data and the conversion model.

[0065] In a third aspect, the present invention provides a device for measuring displacement field and strain field on a screen surface, comprising a processor, a memory, and a computer program stored in the memory. The computer program can be executed by the processor to implement a method for measuring displacement field and strain field on a screen surface as described in any paragraph of the first aspect.

[0066] In a fourth aspect, the present invention provides a computer-readable storage medium. The computer-readable storage medium includes a stored computer program, wherein when the computer program is executed, the device where the computer-readable storage medium is located is controlled to execute a method for measuring a displacement field and a strain field on a screen surface as described in any paragraph of the first aspect.

[0067] By adopting the above technical solution, the present invention can achieve the following technical effects:

[0068] The present invention provides a method for measuring displacement field and strain field of a screen surface, which can provide measurement data close to the actual result, and has a wider measurement range and is more convenient to operate. Compared with the traditional contact measurement method, the non-contact measurement technology adopted by the present invention eliminates the influence of the error caused by the rigid body displacement on the measurement result, making the measurement result more accurate and reliable.

[0069] In addition, the measurement method also has the advantage of providing reliable experimental data for numerical simulation, which is of great significance for improving the overall mechanical properties of the TFT-LCD screen and studying the failure behavior of the screen during the test. By combining numerical simulation analysis, the present invention can not only provide experimental data, but also deeply analyze the mechanical properties of the TFT-LCD screen, thereby providing strong technical support for the design and optimization of the screen. The application value of this method lies in that it can improve the stability and durability of the TFT-LCD screen, reduce the cost of maintenance and replacement, and ultimately improve the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the specific implementation methods of the present invention. It should be understood that the following drawings only show certain specific implementation methods of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0071] Figure 1 The present invention is a flow chart of a method for measuring displacement field and strain field on a screen surface.

[0072] Figure 2 It is an overall schematic diagram of the testing device of the present invention.

[0073] Figure 3 It is a top view schematic diagram of the testing device of the present invention.

[0074] Figure 4 It is a side schematic diagram of the measuring device of the present invention.

[0075] Figure 5 This is a schematic diagram of the target area search and matching of the present invention.

[0076] Markings in the figure: 1-testing machine, 2-pressing head fixing fixture, 3-pressing head, 4-testing machine control panel, 5-testing machine trigger device, 6-stage, 7-carrying block, 8-TFTLCD screen, 9-CCD camera, 10-light source, 11-data transmission line, 12-camera support frame, 13-synchronous trigger, 14-computer. DETAILED DESCRIPTION

[0077] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0078] Example 1, please refer to Figures 1 to 5 The first embodiment of the present invention provides a method for measuring displacement field and strain field on a screen surface, which can be performed by a device for measuring displacement field and strain field on a screen surface (hereinafter referred to as a measuring device). In particular, the method is performed by one or more processors in the measuring device to implement steps S1 to S6.

[0079] S1, pre-processing the TFT-LCD screen to coat its surface with a layer of randomly distributed speckle pattern. Preferably, step S1 adopts a speckle spraying method with black dots on a white background. It includes steps S11 to S13.

[0080] S11. Apply a layer of white matte paint on the surface of the TFT-LCD screen 8 to make it serve as the background color.

[0081] S12. Wait for the white matte paint layer to evaporate and obtain a stable base color.

[0082] S13. Spray black matte paint evenly on the screen surface to form granular randomly distributed spots. To ensure the accuracy of matching, the size of each spot is preferably controlled to about two pixels.

[0083] The speckle spraying method of white background with black dots can ensure that the image has a sharp contrast and a high image recognition accuracy. It is understandable that the surface of the TFT-LCD screen 8 to be measured needs to have a sufficiently random texture in order to be measured. However, the screen surface is smooth and lacks natural texture and cannot produce enough feature points. Therefore, it is necessary to artificially cover the surface to be tested with speckles before the experiment starts to produce enough feature points.

[0084] S2, placing the TFT-LCD screen sample on the stage. Preferably, step S2 specifically includes steps S21 to S22.

[0085] S21, placing the pre-processed TFT-LCD screen 8 on the stage 6. The stage 6 is hollowed out in the center, and the hollowed-out diameter is 30 mm.

[0086] S22. Place carrier blocks 7 (heavy objects) on both side edges of the TFT-LCD screen 8 to fix the screen to prevent it from sliding.

[0087] S3, adjusting the initial position of the pressure head of the universal material testing machine, setting the pressure head drop rate, and the pressure plan. Preferably, step S3 specifically includes steps S31 to S34.

[0088] S31, determine the application position of the external load, and move the TFT-LCD screen 8 to the corresponding position.

[0089] S32, lift the indenter 3 of the universal material testing machine 1 to the external load action area observable by the three-dimensional DIC measurement system, and set the current position as the initial position. The indenter 3 of the testing machine is a rigid indenter or a soft indenter.

[0090] S33, setting the drop rate of the indenter 3 of the universal material testing machine 1 to within 30 mm / min. Specifically, since the screen material is relatively fragile, a too high drop rate may easily cause the screen to break, so the drop rate of the indenter needs to be controlled within a certain range.

[0091] S34, when the pressure head 3 contacts the TFT-LCD screen 8, it stays for 5 seconds and then returns to the initial position.

[0092] In addition, the universal material testing machine 1 further comprises a pressure head fixing fixture 2 for fixing the pressure head 3. The universal material testing machine 1 is provided with a testing machine triggering device 5 for controlling the universal material testing machine 1.

[0093] S4, debug the three-dimensional digital image correlation measurement system, and perform a squeeze test on the TFT-LCD screen to obtain test data. Preferably, step S4 specifically includes steps S41 to S43.

[0094] S41, aligning the intersection of the camera optical axes of the three-dimensional DIC measurement system (ie, three-dimensional digital image correlation measurement system) with the extrusion center of the indenter 3, and ensuring that all CCD cameras 9 can capture the affected area of ​​the TFT-LCD screen 8, that is, the surface of the TFT-LCD screen.

[0095] S42, adjusting the aperture and focal length of the CCD camera 9 so as to present a clear target area in the image processing program. The CCD camera 9 is connected to the computer 14 via the data transmission line 11 and the synchronization trigger 13 and the image acquisition software is started.

[0096] S43, turning on the switch of the testing machine control panel 4 to apply a load, and performing an extrusion test on the TFT-LCD screen 8 under the action of the load.

[0097] Specifically, the light source 10 is installed on the camera support frame 12. To maximize the acquisition accuracy, the surface of the TFT-LCD screen 8 is maximized within the imaging range of the two cameras and covers the entire field of view, so that the frame of each camera can cover most of the area of ​​the TFT-LCD screen 8.

[0098] S5, calibrate the CCD camera of the three-dimensional digital image correlation measurement system to obtain a conversion model between the world coordinate system and the camera coordinate system. Preferably, step S5 specifically includes steps S51 to S53.

[0099] S51, allowing the CCD camera 9 to collect images from eight calibration plates in different orientations.

[0100] S52: Calibrate the CCD camera 9 according to the content captured by the CCD camera 9, and establish a conversion model between the world coordinate system and the camera coordinate system. The conversion model is:

[0101] ;

[0102] In the formula, is the relevant proportionality coefficient, and are the coordinates of the two directions in the camera coordinate system, and are the pixel sizes in two directions in the camera coordinate system, , are the horizontal and vertical coordinates of the image center in the camera coordinate system, is the focal length of the camera, The rotation matrix from the world coordinate system to the built camera coordinate system, is the translation vector from the world coordinate system to the camera coordinate system, , and They are the coordinates of the three directions in the world coordinate system. It is called the normalized focal length on the coordinate axis. The focal length unit is usually mm.

[0103] S53. Based on the conversion model, the two-dimensional coordinates in the camera can be restored to three-dimensional coordinates in the world coordinate system by performing matching calculations using image processing software.

[0104] Before calculating the displacement field and the strain field, the CCD camera 9 needs to be calibrated. The present invention adopts an eight-step calibration method for calibration. The calibration process is: any point on the calibration plate can be expressed in the world coordinate system as , and the coordinates in the image captured by the CCD camera 9 are expressed as , then the relationship between the world coordinates and the pixel coordinates can be expressed as: .

[0105] S6, calculating the displacement field and strain field of the TFT-LCD screen under the external load according to the test data and the conversion model. Preferably, step S6 specifically includes steps S61 to S66.

[0106] Specifically, the 3D DIC measurement system continuously takes a series of photos to record the digital speckle images of the TFT-LCD screen surface under the corresponding load. The collected digital images under a series of loads are used to perform correlation matching calculations using a digital image correlation matching algorithm to obtain the full-field displacement and strain information of the TFT-LCD screen under the load applied by the universal material testing machine indenter.

[0107] The steps of the digital image correlation matching calculation algorithm are as follows:

[0108] S61 , taking the image of the initial state of the TFT-LCD screen captured by the CCD camera 9 as a reference image, and taking the image after the load is applied as a target image.

[0109] S62 , selecting a region of interest where the indenter 3 acts on the image processing program on the computer 14 .

[0110] S63, determine the relevant calculation sub-area, determine the target area at the corresponding position in the target image, set the reference point on the area of ​​interest The coordinates of , target point on the region of interest The coordinates of , the reference point on the target area The coordinates of , the target point is at the target corresponding point on the target area The coordinates of .in, Figure 5 Middle reference point and reference point Between The distance in the direction is ,exist The distance in the direction is .

[0111] Reference Points and target point The relationship between them, and the reference point Corresponding point to the target It can be expressed as:

[0112] ;

[0113] In the formula, As reference point and target point Between Distance of direction, As reference point and target point Between Distance of direction, As reference point Corresponding point to the target Between Distance of direction, As reference point Corresponding point to the target Between Distance in direction.

[0114] The reference point and the target point are spread into the reference area and the target area, and the relationship between the reference area and the target area can be expressed as:

[0115] ;

[0116] ;

[0117] In the formula, represents the region of interest of the reference image, is the gray value distribution function of the reference area, Represents the target area, is the gray value distribution function of the target area, is the deformation mapping function, is the deformation parameter.

[0118] S64, based on the zero-mean normalized minimum distance square standard, correlation calculation is performed using the images captured by the CCD camera 9 before and after the load is applied:

[0119] ;

[0120] In the formula, is the correlation coefficient, is the boundary range of the area of ​​interest, for The target point number of the direction, for The target point number of the direction, The target point is The coordinates of the direction, The target point is The coordinates of the direction, is the value of the target point, is the mean of all target points in the region of interest on the reference image, The target corresponding point is The coordinates of the direction, The target corresponding point is The coordinates of the direction, is the value of the target corresponding point, is the mean of all target corresponding points in the target area.

[0121] S65. The position with the smallest correlation coefficient after the full-field search is the position where the target area is most likely to move to after deformation. The displacement vector of the reference point under the action of external force can be obtained by calculating the coordinate difference between the front and rear positions. .in, , for Displacement in direction, for Displacement in direction.

[0122] S66, calculating the displacement information and strain information of the region of interest according to the displacement vector. Preferably, step S66 includes steps S661 to S662.

[0123] S661. Calculate the gradient of the displacement according to the displacement vector , express exist The rate of change of direction, express exist The rate of change of direction, express exist The rate of change of direction, express exist The rate of change of direction. The rate of change is the degree of deformation of the object in different directions.

[0124] S662: Calculate the strain tensor according to the gradient , Indicates transpose. After expansion, the components are:

[0125] ;

[0126] ;

[0127] ;

[0128] in, for The normal strain in the x-direction represents tension or compression. for The normal strain in the y direction represents the tension or compression. is the shear strain, which represents the in-plane shear deformation.

[0129] The present invention discloses a method for measuring displacement field and strain field of a screen surface, which is a method based on a three-dimensional digital image correlation method. The method obtains the displacement and strain data of the entire TFT-LCD screen surface under the external load by performing a speckle marking process to simulate texture and an optical measurement method. Since non-contact measurement is adopted, the test is simple, and the error influence of the rigid body displacement generated under contact measurement on the measurement result is eliminated, so that the measurement result is closer to the actual value, and the measurement range is wider and the operation is convenient.

[0130] This method can obtain the displacement and strain curves of the TFT-LCD screen surface under external loads over time. It provides reliable experimental data for numerical simulation, which is used to analyze the overall mechanical properties of the screen and study the failure behavior of the screen during the test. It provides a reference for analyzing and improving the overall mechanical properties of the TFT-LCD screen by combining numerical simulation, which has great practical significance.

[0131] Embodiment 2: The present invention provides a device for measuring displacement field and strain field on a screen surface, which includes a preprocessing module, a placement module, a setting module, a debugging module, a calibration module and a calculation module.

[0132] The pre-processing module is used for pre-processing the TFT-LCD screen so as to cover a layer of randomly distributed speckle pattern on the surface of the screen.

[0133] The placement module is used to place the TFT-LCD screen sample on the stage.

[0134] The setting module is used to adjust the initial position of the pressure head of the universal material testing machine, set the pressure head drop rate, and the pressure plan.

[0135] The debugging module is used to debug the 3D digital image correlation measurement system and perform extrusion test on the TFT-LCD screen to obtain test data.

[0136] The calibration module is used to calibrate the CCD camera of the three-dimensional digital image correlation measurement system and obtain the conversion model between the world coordinate system and the camera coordinate system.

[0137] The calculation module is used to calculate the displacement field and strain field of the TFT-LCD screen under the action of external load according to the test data and the conversion model.

[0138] Embodiment 3: The present invention provides a device for measuring displacement field and strain field on a screen surface, comprising a processor, a memory, and a computer program stored in the memory. The computer program can be executed by the processor to implement a method for measuring displacement field and strain field on a screen surface as described in any paragraph of Embodiment 1.

[0139] Embodiment 4: The present invention provides a computer-readable storage medium. The computer-readable storage medium includes a stored computer program, wherein when the computer program is executed, the device where the computer-readable storage medium is located is controlled to execute a method for measuring a displacement field and a strain field on a screen surface as described in any paragraph of Embodiment 1.

[0140] In several embodiments provided in the embodiments of the present invention, it should be understood that the disclosed apparatus and method can also be implemented in other ways. The apparatus and method embodiments described above are merely schematic. For example, the flowcharts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the apparatus, method and computer program product according to multiple embodiments of the present invention. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, program segment or a part of the code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0141] In addition, the functional modules in the various embodiments of the present invention may be integrated together to form an independent part, or each module may exist independently, or two or more modules may be integrated to form an independent part.

[0142] If the function is implemented in the form of a software function module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions to enable a computer device (which can be a personal computer, an electronic device, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program code. It should be noted that in this article, the term "include", "include" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements inherent to such process, method, article or device. Without more constraints, an element defined by the phrase "comprising a..." does not exclude the existence of other identical elements in the process, method, article or apparatus comprising the element.

[0143] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0144] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0145] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0146] The "first\second" mentioned in the embodiments is only to distinguish similar objects, and does not represent a specific order for the objects. It is understandable that the "first\second" can be interchanged with the specific order or sequence where permitted. It should be understood that the objects distinguished by "first\second" can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than those illustrated or described herein.

[0147] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for measuring displacement field and strain field on a screen surface, characterized in that: Comprising steps S1 to S6; S1, pre-processing the TFT-LCD screen to cover a layer of randomly distributed speckle pattern on its surface; S2, placing the TFT-LCD screen sample on the stage; S3, adjust the initial position of the pressure head of the universal material testing machine, set the pressure head drop rate, and the pressure plan; S4. Debug the three-dimensional digital image correlation measurement system, and perform extrusion test on the TFT-LCD screen to obtain test data; S5, calibrating the CCD camera of the three-dimensional digital image correlation measurement system to obtain a conversion model between the world coordinate system and the camera coordinate system; S6. Calculating the displacement field and strain field of the TFT-LCD screen under the external load according to the test data and the conversion model; Step S1 specifically includes steps S11 to S13; S11. Apply a layer of white matte paint on the surface of the TFT-LCD screen to make it serve as the background color; S12. Wait for the white matte paint layer to evaporate and obtain a stable base color; S13, spraying black matte paint evenly on the screen surface to form granular randomly distributed spots; wherein the size of each spot is 2 pixels; Step S3 specifically includes steps S31 to S34; S31, determining the application position of the external load, and moving the TFT-LCD screen to the corresponding position; S32, lifting the indenter of the universal material testing machine to the external load action area observable by the three-dimensional DIC measurement system, and setting the current position as the initial position; wherein the indenter of the testing machine adopts a rigid indenter or a soft indenter; S33. Set the drop rate of the indenter of the universal material testing machine to within 30 mm / min; S34, when the pressure head contacts the TFT-LCD screen, it stays for 5 seconds and then returns to the initial position; Step S4 specifically includes steps S41 to S43; S41, align the intersection of the camera optical axis of the 3D DIC measurement system with the pressing center of the indenter, and ensure that all CCD cameras can capture the affected area of ​​the TFT-LCD screen; S42, adjusting the aperture and focal length of the CCD camera so as to present a clear target area on the image processing program; wherein the CCD camera is connected to the computer through a data transmission line and a synchronization trigger and the image acquisition software is started; S43, turning on the switch of the test machine control panel to apply a load, and performing an extrusion test on the TFT-LCD screen under the action of the load; Step S6 specifically includes steps S61 to S66; S61, taking the image of the initial state of the TFT-LCD screen captured by the CCD camera as a reference image, and taking the image after the load is applied as a target image; S62, selecting a region of interest where the indenter acts on an image processing program on a computer; S63, determine the relevant calculation sub-area, determine the target area at the corresponding position in the target image, set the reference point on the area of ​​interest The coordinates of , target points on the region of interest The coordinates of , the reference point on the target area The coordinates of , the target point is at the target corresponding point on the target area The coordinates of ; Reference Points and target point The relationship between them, and the reference point Corresponding point to the target It can be expressed as: ； In the formula, As reference point and target point Between Distance of direction, As reference point and target point Between Distance of direction, As reference point Corresponding point to the target Between Distance of direction, As reference point Corresponding point to the target Between Distance of direction; The reference point and the target point are spread into the reference area and the target area, and the relationship between the reference area and the target area can be expressed as: ； ； In the formula, represents the region of interest of the reference image, is the gray value distribution function of the reference area, Represents the target area, is the gray value distribution function of the target area, is the deformation mapping function, is the deformation parameter; S64. Based on the zero-mean normalized minimum distance square criterion, correlation calculation is performed using images taken by the CCD camera before and after the load is applied: ； In the formula, is the correlation coefficient, is the boundary range of the area of ​​interest, for The target point number of the direction, for The target point number of the direction, The target point is Direction coordinates, The target point is Direction coordinates, is the value of the target point, is the mean of all target points in the region of interest on the reference image, The target corresponding point is Direction coordinates, The target corresponding point is Direction coordinates, is the value of the target corresponding point, is the mean of all target corresponding points in the target area; S65. The position with the smallest correlation coefficient after the full-field search is the position where the target area is most likely to move to after deformation. The coordinate difference between the front and rear positions is calculated to obtain the displacement vector of the reference point under the action of the external force. ;in, , for Displacement in direction, for Displacement in direction; S66. Calculate the displacement information and strain information of the region of interest according to the displacement vector.

2. A method for measuring displacement field and strain field on a screen surface according to claim 1, characterized in that: Step S2 specifically includes step S21 to step S22; S21, placing the pre-treated TFT-LCD screen on a stage; wherein the stage is hollowed out in the center, and the hollowed-out diameter is 30 mm; S22. Place carrier blocks on both side edges of the TFT-LCD screen to fix the screen and prevent it from sliding.

3. The method for measuring displacement field and strain field of a screen surface according to claim 1, characterized in that: Step S5 specifically includes steps S51 to S53; S51, allowing the CCD camera to collect images from eight calibration plates in different orientations; S52, calibrate the CCD camera according to the content captured by the CCD camera, and establish a conversion model between the world coordinate system and the camera coordinate system; the conversion model is: ； In the formula, is the relevant proportionality coefficient, and are the coordinates of the two directions in the camera coordinate system, and are the pixel sizes in two directions in the camera coordinate system, , are the horizontal and vertical coordinates of the image center in the camera coordinate system, is the focal length of the camera, The rotation matrix from the world coordinate system to the built camera coordinate system, is the translation vector from the world coordinate system to the camera coordinate system, , and They are the coordinates of three directions in the world coordinate system; S53. Based on the conversion model, the two-dimensional coordinates in the camera can be restored to three-dimensional coordinates in the world coordinate system by performing matching calculations using image processing software.

4. The method for measuring displacement field and strain field of a screen surface according to claim 1, characterized in that: Step S66 includes step S661 to step S662; S661. Calculate the gradient of the displacement according to the displacement vector ; , where: express exist The rate of change of direction, express exist The rate of change of direction, express exist The rate of change of direction, express exist The rate of change of direction; the rate of change is the degree of deformation of the object in different directions; S662: Calculate the strain tensor according to the gradient ; , represents transpose; After expansion, the components are: ； ； ； in, for The normal strain in the x-direction represents tension or compression. for The normal strain in the y direction represents the tension or compression. is the shear strain, which represents the in-plane shear deformation.

5. A device for measuring displacement field and strain field on a screen surface, characterized in that: It comprises a processor, a memory, and a computer program stored in the memory; the computer program can be executed by the processor to implement a method for measuring displacement field and strain field of a screen surface as described in any one of claims 1 to 4.

6. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored computer program, wherein when the computer program is executed, the device where the computer-readable storage medium is located is controlled to execute a method for measuring a displacement field and a strain field on a screen surface as described in any one of claims 1 to 4.

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