Method and device for measuring thickness variation of target measured object

Abstract

The invention relates to the technical field of image processing, in particular to a method and device for measuring the thickness variation of a target measured object, and the method comprises the steps: obtaining a current frame image and a previous frame image of a reference object through a microscope, and calculating the definition variation between the two frames of images; the Z-axis movement of the microscope is adjusted according to the definition variable quantity and the preset threshold value to achieve accurate focusing of the reference object, the thickness variable quantity of the target measured object is determined according to the moving distance of the Z-axis of the microscope and the height variable quantity corresponding to the definition variable quantity, and non-contact and high-precision thickness change measurement is achieved.

Description

Technical Field

[0001] This application relates to the field of image processing technology, and in particular, to a method and device for measuring the thickness change of a target object to be measured. Background Art

[0002] Thickness / height measurement is an indispensable part of materials science and engineering applications. Traditional contact measurement methods, such as contact sensors, although to a certain extent can meet the basic measurement needs, their inherent contact characteristics must be in direct contact with the object to be measured during the measurement process. This not only may interfere with the surface state of the object to be measured, but may even cause mechanical damage to it, especially for materials with soft texture or easily damaged surfaces. In addition, the resolution of contact sensors is mostly above the micron level, which limits their application in the field of high-precision measurement, especially in cases where sub-micron level accuracy is required. In addition, some samples need to be tested in a specific atmosphere environment, and contact sensors are not applicable. Based on this, laser confocal sensors, as another common method for measuring thickness changes, although to a certain extent improve the measurement resolution, sacrifice the test range in order to achieve high resolution. In the high-resolution mode, due to the test range of the laser confocal sensor, it cannot be applied to samples with a large thickness change range, which limits the application of laser confocal sensors in the measurement of complex samples. Therefore, the existing thickness / height measurement methods have limitations and cannot meet the requirements of high-precision and non-contact measurement. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, the present invention provides a method and device for measuring the thickness change of a target object to be measured, realizing high-precision and non-contact measurement.

[0004] The first aspect of this application provides a method for measuring the thickness change of a target object to be measured, the method includes: Obtain the current frame image and the previous frame image of the reference object, and calculate the sharpness change amount between the current frame image and the previous frame image, the current frame image and the previous frame image are obtained through a microscope; Adjust the microscope Z-axis of the microscope according to the sharpness change amount and a preset threshold so that the microscope focuses on the reference object; Calculate the thickness change amount of the target object to be measured according to the moving distance of the microscope Z-axis of the sharpness change amount.

[0005] In an optional embodiment, the calculating the sharpness change amount between the current frame image and the previous frame image includes: Obtain the first sharpness score of the current frame image and the second sharpness score of the previous frame image; Determine the clarity score difference between the first clarity score and the second clarity score; Normalize the clarity score difference to obtain the clarity change amount.

[0006] In an alternative embodiment, the method further includes: Obtain the best focused image of the reference object and determine the clarity score corresponding to the best focused image as the highest clarity score; Obtain the blurred focused image of the reference object when the defocus distance of the microscope is equal to the depth of field of the objective lens used by the microscope, and determine the clarity score corresponding to the blurred focused image as the lowest clarity score; Obtain the first reference object images of the reference object in different defocus states to obtain a set of reference object images; Calculate the third clarity score of each first reference object image in the set of reference object images; Fit the functional relationship between the clarity change rate and the height change rate according to the highest clarity score, the lowest clarity score, and the third clarity score; Determine the functional relationship between the clarity change rate and the height change rate as the clarity-height mapping relationship.

[0007] In an alternative embodiment, the adjusting the microscope Z-axis of the microscope to focus on the reference object according to the clarity change amount and a preset threshold includes: Determine the height change amount corresponding to the clarity change amount according to the clarity-height mapping relationship; Compare the height change amount with the preset threshold; When the height change amount is greater than the preset threshold, determine to adjust the microscope Z-axis; After controlling the microscope Z-axis to move a preset step length in the first direction, obtain the second reference object image of the reference object after the movement and calculate the fourth clarity score of the second reference object image; When the fourth clarity score increases, determine that the thickness change direction of the target object to be measured is the same as the first direction, and control the microscope Z-axis to move according to the first direction to focus on the reference object; When the fourth clarity score decreases, control the microscope Z-axis to move in the second direction, and perform the operation of obtaining the second reference object image of the reference object after the movement, where the second direction is opposite to the first direction.

[0008] In an alternative embodiment, calculating the thickness change amount of the target object to be measured based on the clarity change amount and the moving distance of the microscope along the Z-axis includes: When it is determined that the height change amount is less than the preset threshold, determining the thickness change amount according to the height change amount; When it is determined that the height change amount is greater than the preset threshold, obtaining the moving distance of the microscope along the Z-axis; Determining the thickness change amount according to the height change amount and the moving distance of the microscope along the Z-axis.

[0009] In an alternative embodiment, determining the thickness change amount according to the height change amount and the moving distance of the microscope along the Z-axis includes: Determining a first moving distance of the microscope along the Z-axis in the first direction and a second moving distance in the second direction; Determining the total moving distance of the microscope along the Z-axis according to the first moving distance and the second moving distance; Determining the thickness change amount according to the total moving distance of the Z-axis and the height change amount.

[0010] In an alternative embodiment, the preset threshold is an adjustable parameter set according to system characteristic parameters, and the system characteristic parameters include the clarity-height mapping relationship and the minimum movable resolution of the microscope along the Z-axis.

[0011] In an alternative embodiment, the preset threshold conforms to the linear relationship interval of the clarity-height mapping relationship, and the preset threshold is greater than the minimum resolution of the Z-axis.

[0012] In an alternative embodiment, before obtaining the current frame image and the previous frame image of the reference object, the method further includes: placing the reference object at the center of the test area, placing the target object to be measured below the reference object and in contact with the lower surface of the reference object; aligning the microscope with the reference object to set the current focus reference of the microscope, so that the microscope obtains the current frame image based on the current focus reference.

[0013] A second aspect of the present application provides a device for measuring the thickness change amount of a target object to be measured. The device is used to place the target object to be measured and the reference object, and includes a relatively fixed lower base and a movable upper cover. The reference object is arranged on the upper cover, is in contact with the target object to be measured, and generates displacement as the thickness of the target object to be measured changes.

[0014] A third aspect of the present application provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the steps of the method for measuring the thickness change of the target object to be measured are implemented.

[0015] A fourth aspect of the present application provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method for measuring the thickness change of the target object to be measured are implemented.

[0016] In summary, the method and device for measuring the thickness change of the target object to be measured provided by the present application perform non-contact imaging through a microscope, indirectly measure the thickness by analyzing the change in image sharpness, and do not require physical contact with the sample. When the sharpness of the reference object image at the previous moment changes from that of the reference object image at the current moment, the Z-axis position of the microscope is dynamically adjusted according to the sharpness change amount and a preset threshold to maintain focus. The thickness change of the target object to be measured is inversely deduced by using the Z-axis displacement amount and the height change amount corresponding to the sharpness change amount, converting the thickness measurement into a displacement measurement, realizing non-contact measurement, and improving the measurement accuracy and flexibility. In addition, through the tiny change trend of the image sharpness, the sensitive capture of the thickness change of the object to be measured is realized, and the measurement accuracy is higher than the spatial resolution ability determined by the depth of field of a traditional electron microscope. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of a device for measuring the thickness change of a target object to be measured shown in an embodiment of the present application; Figure 2 is a schematic flowchart of a method for measuring the thickness change of a target object to be measured shown in an embodiment of the present application; Figure 3 is a schematic structural diagram of an electronic device shown in an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The present invention will be further described below with reference to the drawings and embodiments.

[0019] The concept, specific structure and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments and the drawings, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention. In addition, all the connection / linkage relationships involved in the patent do not refer only to the direct connection of components, but refer to the formation of a more optimal connection structure by adding or reducing connection accessories according to specific implementation situations. The various technical features in the present invention can be combined interactively without conflicting with each other.

[0020] Referring to Figure 1 As shown, it is a schematic structural diagram of a device for measuring the thickness change of a target object to be measured according to an embodiment of the present application.

[0021] The device for measuring the thickness change of the target object to be measured is used to place the target object to be measured and a reference object, and cooperate with a microscope system to collect the focal length change caused by the displacement of the reference object, so as to indirectly measure the thickness change of the object to be measured. The device for measuring the thickness change of the target object to be measured includes a relatively fixed lower base and a movable upper cover. The upper cover is provided with a sealed transparent window. The lower base includes a rigid component and remains stationary during the measurement of the thickness change. In addition, a target object to be measured and a reference object are placed in the device. The reference object is arranged on the upper cover, and the target object to be measured is placed below the reference object and contacts the lower surface of the reference object. As the thickness of the target object to be measured changes, that is, expands and contracts, it moves up and down.

[0022] In some embodiments, the device for measuring the thickness change of the target object to be measured can be placed on a temperature control platform, or a temperature control system can be integrated at the lower part of the sealed cavity.

[0023] In some embodiments, the present application also provides a system for measuring the thickness change of a target object to be measured. The system may include the device for measuring the thickness change of the target object to be measured and a microscope, which is used to collect the reference object image of the reference object and transmit the reference object image to an electronic device, so that the electronic device can determine the thickness change of the target object to be measured through the reference object image. Among them, the microscope can be a digital microscope or an optical microscope, which is not limited in the present application. The microscope may include an objective lens with a high numerical aperture (NA), for example, NA = 0.8. The depth of field (DOF) of the objective lens used in the microscope is obtained according to NA. In addition, the microscope also includes a high-precision Z-axis motor, and the stepping accuracy can be 20 nanometers, which supports precise adjustment of small thickness changes.

[0024] Wherein, the target object to be measured refers to the main body whose thickness change needs to be measured. In some embodiments, the target object to be measured may be a material, and the corresponding thickness change refers to the volume expansion change during heating or stress application. In other embodiments, the target object to be measured may be a battery electrode material, and the corresponding thickness change refers to the thickness change during the electrochemical charge and discharge process. Before measuring the thickness change, manual or automatic focusing is required to align the microscope with a reference object above the target object to be measured, where the reference object is located at the center of the test area.

[0025] For the convenience of understanding the inventive concept of the present application, the target object to be measured in the embodiments of the present application will be described by taking an electrode as an example to monitor the dynamic change of the electrode thickness during the charge and discharge process of the battery.

[0026] In some embodiments, the rigid component includes a bottom rigid component and an upper rigid component. The bottom rigid component is fixed to the lower base, can be connected to the pressure sensor, and has a flat and conductive inner surface to ensure full contact with the lower surface of the battery electrode. Moreover, the upper rigid component can move vertically freely, with the bottom fitting the upper surface of the battery electrode and the top being the reference object. Additionally, a high-precision guide rail or linear bearing can be used to ensure that the upper component only moves in the vertical direction to avoid tilting; and the electrode (such as a lithium-ion battery electrode sheet) is clamped between the two rigid components, and a slight pre-pressure (such as 1N to 5N) is applied to ensure contact but not limit expansion. Then, the central field of view of the microscope is aligned with the reference object.

[0027] Refer to Figure 2 As shown, it is a schematic flowchart of a method for measuring the thickness change of a target object to be measured shown in the embodiments of the present application. The method for measuring the thickness change of the target object to be measured includes the following steps.

[0028] S21, obtain the current frame image and the previous frame image of the reference object, and calculate the sharpness change amount between the current frame image and the previous frame image.

[0029] Wherein, the current frame image and the previous frame image are obtained through the microscope. In some embodiments, an image of the reference object at the current moment can be collected through the microscope, which is called the current frame image; similarly, at the previous moment of the current moment, the microscope also collected an image of the reference object, which is called the previous frame image. When the microscope collects the reference object image, the reference object image is transmitted to the electronic device in real time through active sending or passive transmission. After the electronic device obtains the current frame image and the previous frame image, it can calculate the sharpness change amount between the current frame image and the previous frame image.

[0030] In an alternative embodiment, the calculating the sharpness change amount between the current frame image and the previous frame image includes: Obtain the first sharpness score of the current frame image and the second sharpness score of the previous frame image; Determine the sharpness score difference between the first sharpness score and the second sharpness score; Perform normalization processing on the sharpness score difference to obtain the sharpness change amount.

[0031] In some embodiments, the electronic device first determines the sharpness score of the current frame image and the sharpness score of the previous frame image. For the sake of easy distinction, the sharpness score of the current frame image is referred to as the first sharpness score, and the sharpness score of the previous frame image is referred to as the second sharpness score. Among them, the electronic device can evaluate the sharpness score based on the texture details or edge information intensity of the reference object image, such as based on image gradient, image frequency components, and edge changes, etc. In the implementation of this application, the sharpness score is quantified by the gradient value or pixel intensity change of the image. Generally, on the premise of keeping the imaging system parameters unchanged, the change in image sharpness mainly reflects the change in the focus position. Specifically, the electronic device can use a sharpness evaluation algorithm, such as the Sobel gradient method or the Laplace operator method. First, calculate the horizontal and vertical gradients of the reference object area in the current frame image, then calculate the gradient amplitude of the corresponding pixel points through these gradients, and further sum the gradient amplitudes of all pixel points to determine the first sharpness score of the current frame image. Similarly, according to the same embodiment method for determining the first sharpness score, the second sharpness score can be determined.

[0032] When the second sharpness score of the previous frame image and the first sharpness score of the current frame image are determined, the sharpness score difference between the first sharpness score and the second sharpness score can be calculated, where the sharpness score difference = first sharpness score - second sharpness score, and then normalization processing is performed on the sharpness score to obtain the sharpness change amount (in percentage form), that is, the sharpness change percentage. Among them, the sharpness change amount = (sharpness score difference / second sharpness score) × 100%. Normalization processing is to unify numerical values of different magnitudes into a specific range (such as 0% to 100%) for subsequent comparison and calculation. Exemplarily, assuming the second sharpness score is 100 and the first sharpness score is 90, then the sharpness score difference = |first sharpness score - second sharpness score| = |90 - 100| = 10, and the sharpness change amount = sharpness score difference / second sharpness score × 100% = 10 / 100 × 100% = 10%.

[0033] For the convenience of understanding the inventive concept of this application, this application provides an embodiment with a tool code example as follows: # Calculate the sharpness change percentage def calculate_clearance(previous_score, current_score): if previous_score == 0: return 0# Or directly return a maximum value, such as 100%, depending on actual requirements change = abs(current_score - previous_score) change_percentage = (change / previous_score) * 100 return change_percentage In some embodiments, when obtaining the reference object images (including the previous frame image and the current frame image), the electronic device can preprocess the reference object images. For example, first convert the reference object images into black and white images to reduce the amount of calculation, and then use CUDA to perform Sobel convolution and gradient accumulation in parallel to improve the calculation speed.

[0034] S22. Adjust the microscope Z-axis of the microscope according to the clarity change amount and a preset threshold so that the microscope focuses on the reference object.

[0035] In some embodiments, when obtaining the clarity change amount, the corresponding height change amount of the clarity change amount can be determined, and the corresponding height change amount is compared with a preset threshold. When it is determined that the height change amount is greater than the preset threshold, the microscope Z-axis of the microscope is adjusted so that the microscope refocuses on the reference object. Specifically, the preset threshold conforms to the linear relationship interval of the clarity-height mapping relationship, and the preset threshold is greater than the minimum resolution of the Z-axis.

[0036] In an alternative embodiment, the method further includes: Obtain the best focused image of the reference object and determine the clarity score corresponding to the best focused image as the highest clarity score; Obtain the blurred focused image of the reference object when the defocus distance of the microscope is equal to the depth of field of the objective lens used by the microscope, and determine the clarity score corresponding to the blurred focused image as the lowest clarity score; Obtain the first reference object images of the reference object in different defocus states to obtain a set of reference object images; Calculate the third clarity score of each first reference object image in the set of reference object images; Fit the functional relationship between the clarity change rate and the height change rate according to the highest clarity score, the lowest clarity score, and the third clarity score; Determine the functional relationship between the clarity change rate and the height change rate as the clarity-height mapping relationship.

[0037] In some embodiments, the electronic device can pre-construct the clarity-height mapping relationship. When the clarity change amount is obtained through step S21, the clarity change amount can be converted based on the clarity-height mapping relationship into the height change amount of the reference object. Specifically, by placing the reference object at the optimal focusing position of the microscope and obtaining the clearest image of the reference object through the microscope, that is, the optimal focusing image. After obtaining the optimal focusing image, adjust the defocus distance of the microscope to be equal to the depth of field of the objective lens used (the edge of the depth of field). When the defocus distance is equal to the depth of field of the objective lens used, obtain the image of the reference object, that is, the blurred focusing image, which is relatively blurred. When the electronic device obtains the optimal focusing image and the blurred focusing image, it can perform clarity scoring on the optimal focusing image and the blurred focusing image according to the same embodiment method of calculating the clarity score as described above. The clarity score corresponding to the optimal focusing image is called the highest clarity score, and the clarity score corresponding to the blurred focusing image is called the lowest clarity score.

[0038] Furthermore, obtain the reference object images of the reference object in different defocus states through the microscope (for the sake of distinction, called the first reference object images), and obtain a set of reference object images. Among them, different and known heights can be moved up and down for the reference object to simulate different thickness situations that may be encountered in actual measurement. Place the reference object in the corresponding image acquisition area of the microscope, adjust the known different height change amounts, and obtain the first reference object images of the microscope in different defocus states to form a set of reference object images. The electronic device, by obtaining the set of reference object images, also determines the clarity score of each first reference object image in the set of reference object images according to the same implementation manner of calculating the clarity score as described above, which is called the third clarity score. Then, according to the highest clarity score, the lowest clarity score, and the third clarity score, fit the functional relationship between the clarity change rate and the height change rate. For example, methods such as linear regression and polynomial regression can be used. By analyzing the trend of the clarity score changing with height, a mathematical function expression can be obtained, which describes the corresponding relationship between the clarity change rate and the height change rate, and determine it as the clarity-height mapping relationship. Through the clarity-height mapping relationship, the electronic device can then determine the height change amount of the reference object corresponding to the clarity change amount between the current frame image and the previous frame image.

[0039] In other embodiments, when the clarity change amount is obtained, it can be directly compared with the new preset threshold. When it is determined that the clarity change amount is greater than the new preset threshold, the microscope Z-axis of the microscope is adjusted so that the microscope focuses on the reference object. Specifically, the electronic device can obtain the depth of field of the objective lens used by the microscope and the minimum movable resolution of the microscope Z-axis. The minimum movable resolution of the microscope Z-axis is its minimum controllable vertical displacement accuracy (for example, 0.02 μm), and the depth of field of the objective lens used by the microscope refers to the depth of field range of the currently used objective lens (for example, 0.6 μm). Among them, the preset threshold is an adjustable parameter set according to system characteristic parameters, including the clarity-height mapping relationship and the minimum movable resolution of the microscope Z-axis. Then, a clarity change threshold (hereinafter simply referred to as the new preset threshold) is determined according to the depth of field of the objective lens used by the microscope and the minimum movable resolution of the microscope Z-axis. Specifically, the new preset threshold is determined by the following formula: New preset threshold = minimum movable resolution / depth of field of the objective lens used.

[0040] When the clarity change amount is calculated, the height change corresponding to the clarity change amount is compared with the new preset threshold. If the clarity change amount is greater than the clarity change threshold, it means that the thickness change of the target object to be measured has exceeded the threshold, and the microscope Z-axis needs to be adjusted to refocus on the reference object. Specifically, the first clarity score and the second clarity score are compared. When it is determined that the first clarity score is higher than the second clarity score, it means that the clarity of the reference object increases, indicating that the focus deviates from the current value and the target object to be measured expands. Then, the microscope Z-axis can be adjusted to move upward, refocus on the reference object again, and determine the distance that the microscope Z-axis moves upward. Then, the thickness change amount of the expansion of the target object to be measured can be determined; when it is determined that the first clarity score is lower than the second clarity score, it means that the clarity of the reference object decreases, indicating that the focus moves away and the target object to be measured shrinks. Then, the microscope Z-axis can be adjusted to move downward, refocus on the reference object again, and determine the distance that the microscope Z-axis moves downward. Then, the thickness change amount of the shrinkage of the target object to be measured can be determined. Exemplarily, assuming that the minimum resolution of the microscope Z-axis movement is 0.1 μm and the depth of field of the objective lens used by the microscope is 0.6 μm, then the clarity change threshold = 0.1 / 0.6 = 1 / 6. When the clarity change amount is greater than 1 / 6, it means that the focus has changed slightly, and at this time, the microscope Z-axis needs to be adjusted to refocus.

[0041] To facilitate the understanding of the inventive concept of the present application, an embodiment of the present application provides a tool code example, and the code is as follows: # Automatic focusing algorithm def autofocus_z_axis(frames, z_resolution, dof): threshold = z_resolution / dof / 6 # Threshold for sharpness change (1 / 6 change) previous_score = sobel_gradient(frames[0]) # Sharpness score of the previous frame for i in range(1, len(frames)): current_score = sobel_gradient(frames[i]) # Calculate the percentage of sharpness change param = calculate_clearance(previous_score, current_score) # Determine whether the new preset threshold is exceeded if param>= threshold: # If the sharpness change exceeds the new preset threshold, trigger Z-axis adjustment if current_score>previous_score: move_z_axis('up') # If the sharpness increases, adjust upward else: move_z_axis('down') # If the sharpness decreases, adjust downward previous_score = current_score # Update the sharpness score of the previous frame It should be noted that the preset threshold and the new preset threshold can be automatically adjusted according to the actual changes in the microscope objective lens and the electrode thickness.

[0042] In an alternative embodiment, adjusting the microscope Z-axis of the microscope according to the amount of sharpness change and the preset threshold so that the microscope focuses on the reference object includes: Determining the height change amount corresponding to the amount of sharpness change according to the sharpness-height mapping relationship; Comparing the height change amount with the preset threshold; When the height change amount is greater than the preset threshold, determining to adjust the microscope Z-axis; After controlling the microscope Z-axis to move a preset step length in the first direction, obtain a second reference object image of the moved reference object, and calculate a fourth sharpness score of the second reference object image; When the fourth sharpness score increases, determine that the thickness change direction of the target object to be measured is the same as the first direction, and control the microscope Z-axis to move in the first direction to focus on the reference object; When the fourth sharpness score decreases, control the microscope Z-axis to move in the second direction, and perform the operation of obtaining the second reference object image of the moved reference object. The second direction is opposite to the first direction.

[0043] In some embodiments, when the sharpness change amount is obtained, the electronic device can input the sharpness change amount into the sharpness-height mapping relationship to output the corresponding height change amount. When it is determined that the height change amount is greater than the preset threshold, it is determined that the microscope Z-axis needs to be adjusted. When it is determined that the microscope Z-axis needs to be moved for adjustment, first control the microscope to move in the first direction (for example, downward) according to the preset step length (for example, 0.1 μm). After the microscope Z-axis moves to the preset step length, re-obtain the reference object image through the microscope, which is called the second reference object image, and send the second reference object image to the electronic device. After the electronic device obtains the second reference object image, determine the sharpness score of the newly obtained reference object image based on the above-described embodiment of calculating the sharpness score, which is called the fourth sharpness score. Then, compare the fourth sharpness score with the first sharpness score. When it is determined that the fourth sharpness score increases, it can be determined that the thickness change direction of the target object to be measured is the same as the moving direction of the microscope Z-axis, that is, the same as the first direction. Then control the microscope Z-axis to maintain the current moving direction and continue to control the microscope Z-axis to continue moving in the first direction to achieve re-focusing on the reference object. When it is determined that the fourth sharpness score decreases, it can be determined that the thickness change amount of the target object to be measured is inconsistent with the moving direction of the microscope Z-axis. Then control the microscope Z-axis to move in the second direction opposite to the first direction and move to the preset step length to achieve re-focusing on the reference object. When the microscope Z-axis moves in the second direction to re-focus, calculate the thickness change amount of the target object to be measured according to the moving distance of the microscope Z-axis. Among them, the first direction can be any one of the downward direction or the upward direction. When the first direction is the downward direction, the second direction is the upward direction; when the second direction is the upward direction, the second direction is the downward direction.

[0044] S23. Calculate the thickness change amount of the target object to be measured according to the sharpness change amount and the moving distance of the microscope Z-axis.

[0045] In some embodiments, the electronic device can determine whether the Z-axis of the microscope has moved. When it is determined that the Z-axis of the microscope has not moved, the electronic device can directly determine the corresponding height change amount based on the clarity change amount of the microscope, and determine the thickness change amount of the target object to be measured according to the height change amount. That is, after determining the height change amount of the reference object based on the clarity-height mapping relationship, the electronic device can determine the thickness change amount of the target object to be measured based on the height change amount of the reference object. Since the reference object is in contact with the target object to be measured, and the reference object is arranged on the upper surface of the target object to be measured, when it is determined that the height of the reference object changes upward, it is determined that the thickness of the target object to be measured changes upward, and when it is determined that the height of the reference object changes downward, it is determined that the thickness of the target object to be measured changes downward, and the corresponding thickness change amount is equal to the height change amount of the reference object. Exemplarily, assuming that the height of the reference object changes upward by 0.5 μm, then the thickness of the target object to be measured also changes upward by 0.5 μm accordingly.

[0046] In some embodiments, when adjusting the movement of the microscope Z-axis according to the height change amount corresponding to the clarity change amount and the preset threshold, the electronic device can obtain the movement distance of the microscope Z-axis, and determine the thickness change amount of the target object to be measured according to the height change amount corresponding to the clarity change amount and the movement distance of the microscope Z-axis. Specifically, when it is determined that the microscope Z-axis moves, the electronic device can determine whether the microscope Z-axis moves upward or downward and what the moving distance is, and send the moving data, including the moving direction and the moving distance, to the electronic device, and the electronic device can determine the thickness change amount of the target object to be measured according to the moving data. Specifically, determine the moving direction of the microscope Z-axis, and obtain the first moving distance of the microscope Z-axis in the first direction and the second moving distance in the second direction. Calculate the total Z-axis moving distance of the first moving distance and the second moving distance. The total Z-axis moving distance = |the first moving distance - the second moving distance|. Exemplarily, assuming that the microscope Z-axis first moves in the first direction (for example, moves downward), the first moving distance is 0.1 μm, and then moves in the second direction (for example, moves upward), the second moving distance is 0.3 μm, then the total Z-axis moving distance of the microscope Z-axis is 0.2 μm downward.

[0047] When determining the total moving distance of the microscope Z-axis, the sum of the total moving distance and the height change amount corresponding to the clarity change amount is determined as the thickness change amount of the target object to be measured, that is, the thickness change amount = the total moving distance + the height change amount.

[0048] In some embodiments, after determining the real-time thickness change amount of the target object to be measured, such as a battery, the electronic device can output a real-time thickness change amount-time curve, support data export (CSV / Excel format), which can be used for subsequent battery performance analysis and failure research.

[0049] In an alternative embodiment, the method further includes: When the thickness change amount cannot be determined based on the sharpness change amount, feature objects with different height features in the reference object are obtained. The number of feature objects with different height features is an integer greater than or equal to 3, and the feature heights of the different height features are determined by the depth of field of the objective lens used in the microscope or the minimum resolution of the Z-axis movement of the microscope; The thickness change amount is determined based on the second sharpness change amount of the feature objects with different height features.

[0050] To facilitate the distinction of different sharpness change amounts, the sharpness change amount between the current frame image and the previous frame image is referred to as the first sharpness change amount. In some embodiments, the reference object includes feature objects with different height features. The number of feature objects with different height features is an integer greater than or equal to 3, and the feature heights of the height features at different heights can be determined by the depth of field of the objective lens used in the microscope or the minimum resolution of the Z-axis movement of the microscope. Specifically, when the minimum resolution of the Z-axis movement of the microscope is greater than the depth of field of the objective lens used in the microscope, the feature heights of the different height features are set according to the depth of field of the objective lens used in the microscope. For example, they are set to the corresponding value of the depth of field of the objective lens used in the microscope or a multiple thereof; when the minimum resolution of the Z-axis movement of the microscope is less than the depth of field of the objective lens used in the microscope, the feature heights of the different height features are set according to the minimum resolution corresponding to the minimum resolution of the Z-axis movement of the microscope. For example, they are set to the corresponding value of the minimum resolution of the Z-axis movement of the microscope or a multiple thereof. It should be noted that the multiple setting can be either an integer multiple or a decimal multiple to ensure that the change in the Z-axis focal length of the microscope can reflect the height change of the sample.

[0051] Exemplarily, assume that the depth of field of the objective lens used in the microscope is 0.6 μm and the minimum resolution of the Z-axis movement of the microscope is 1.5 μm. Then the feature height is set according to the depth of field of the objective lens used in the microscope. When the number of features is 3, the feature object heights can be set to -0.6 μm, 0 μm, and 0.6 μm; assume again that the depth of field of the objective lens used in the microscope is 0.6 μm and the minimum resolution of the Z-axis movement of the microscope is 0.5 μm. Then the feature height is set according to the minimum resolution of the Z-axis of the microscope. When the number of features is 5, the feature object heights can be set to -1.0 μm, -0.5 μm, 0 μm, 0.5 μm, and 1.0 μm.

[0052] Since the feature objects have different height features, in the embodiments of the present application, the intermediate height feature among the different height features is referred to as the 0-height feature, and the feature height is 0 μm. When measuring the thickness change of the target object to be measured, the microscope focuses on the intermediate height feature among the different height features, that is, the 0-height feature, and sets the clarity corresponding to the 0-height feature as the focus reference (recorded as "0 position"), so that the microscope can acquire the reference object image based on this focus reference.

[0053] When it is determined that the thickness change of the target object to be measured cannot be determined according to the first clarity change amount, the electronic device acquires the reference object images including each height feature of different height features according to the same embodiment manner as above, including the previous frame image and the current frame image, and then determines the clarity score corresponding to each height feature of different height features according to the previous frame image and the current frame image. For the convenience of distinction, the clarity score of each height feature of the feature objects with different height features in the current frame image is referred to as the fifth clarity score, and the clarity score of each height feature of the feature objects with different height features in the previous frame image is referred to as the sixth clarity score. Specifically, according to the same embodiment manner of calculating the first clarity score as above, the electronic device can use the clarity evaluation algorithm, such as the Sobel gradient method or the Laplace operator method. First, calculate the horizontal gradient and vertical gradient corresponding to the different height features in the current frame image, then determine the gradient amplitude of each pixel point corresponding to the different height features in the current frame image through the horizontal gradient and vertical gradient, and then sum up the gradient amplitudes of all pixel points corresponding to the different height features in the current frame image, so as to determine the fifth clarity score corresponding to the different height features in the current frame image, and determine the sixth clarity score.

[0054] After determining the fifth clarity score and the sixth clarity score, the electronic device determines the clarity change amount of the feature objects with different height features based on the fifth clarity score and the sixth clarity score, which is referred to as the second clarity change amount, so as to determine the thickness change amount of the target object to be measured according to the second clarity change amount. Specifically, when it is determined that the clarity of the lower height feature among the different height features, that is, the first height feature, increases, it indicates that the focus deviates from the current value and the target object to be measured expands. Then, the microscope Z-axis can be adjusted to move upward, refocus on the 0-height feature, and determine the moving distance of the microscope Z-axis upward, so as to determine how much the thickness of the target object expands; when it is determined that the clarity of the higher height feature among the different height features, that is, the second height feature, increases, it indicates that the focus moves away and the target object to be measured shrinks. Then, the microscope Z-axis can be adjusted to move downward, refocus on the 0-height feature, and determine the moving distance of the microscope Z-axis downward, so as to determine how much the thickness of the target object shrinks.

[0055] Refer to Figure 3As shown, the embodiments of the present application show a schematic structural diagram of an electronic device 3. In a preferred embodiment, the electronic device 3 includes a memory 31, at least one processor 32, and at least one communication bus 33.

[0056] Those skilled in the art should be aware that Figure 3 the structure shown is only a schematic embodiment, and the structure of the electronic device 3 can adopt a bus type, star type or other topological structures, and the hardware and software modules can be increased or decreased according to actual needs, or the physical arrangement of each component can be adjusted.

[0057] In some embodiments, the electronic device 3 may include a processing unit for performing image analysis and thickness change calculation, and its hardware includes but is not limited to a microprocessor (CPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), and an embedded processor, etc. The electronic device 3 may also include a terminal device with a human-computer interaction function, such as a personal computer, a tablet computer, a smart phone, etc., and performs interactive operations through a keyboard, a mouse, a touch screen or a voice input device.

[0058] Each method, device, computer-readable storage medium, and electronic device described in the present application can be completed through different software and hardware implementation methods. For example, the module division is only a functional schematic, and in actual implementation, the modules can be physically integrated, split, or reorganized according to requirements. The connection relationship between the modules can be either directly coupled or realized through electrical, mechanical, or other physical connection methods.

[0059] The functional modules can be implemented by integrating in hardware form or can also be implemented by software functional modules in a computing device. When implemented in the form of a software product and sold or used separately, it can be stored in a computer-readable storage medium. When the computer program is executed by a processor, all or part of the steps of the method described in the present application are realized. The aforementioned storage medium includes but is not limited to: USB flash drives, mobile hard disks, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical discs and other media that can store program codes.

[0060] It should be noted that for ease of description, the above method embodiments use a series of action combinations for expression, but the execution order of each step is not limited thereto, and the order can be adjusted according to actual needs or executed in parallel. In addition, those skilled in the art should understand that the embodiments described in the specification are only preferred embodiments and are not limitations to the present invention. The functions and modules involved do not necessarily need to be all implemented. The above is a specific description of the preferred embodiments of the present invention, but the present invention is not limited to the described embodiments. Those skilled in the art can also make various equivalent deformations or substitutions without departing from the spirit of the present invention, and these equivalent deformations or substitutions are all included within the scope defined by the claims of the present application.

Claims

1. A method for measuring the thickness change of a target object to be measured, characterized in that, The method includes: Obtaining a current frame image and a previous frame image of a reference object, and calculating a sharpness change amount between the current frame image and the previous frame image, where the current frame image and the previous frame image are obtained through a microscope; Adjusting the microscope Z-axis of the microscope according to the sharpness change amount and a preset threshold so that the microscope focuses on the reference object; Calculating a thickness change amount of the target object to be measured according to the sharpness change amount and the moving distance of the microscope Z-axis.

2. The method for measuring the thickness change amount of the target object to be measured according to claim 1, characterized in that, The calculating the sharpness change amount between the current frame image and the previous frame image includes: Obtaining a first sharpness score of the current frame image and a second sharpness score of the previous frame image; Determining a sharpness score difference between the first sharpness score and the second sharpness score; Performing a normalization process on the sharpness score difference to obtain the sharpness change amount.

3. The method for measuring the thickness change amount of the target object to be measured according to claim 1, wherein, The method further includes: Obtaining an optimal focus image of the reference object and determining the sharpness score corresponding to the optimal focus image as the highest sharpness score; Obtaining a blurred focus image of the reference object when the defocus distance is equal to the depth of field of the objective lens used by the microscope, and determining the sharpness score corresponding to the blurred focus image as the lowest sharpness score; Obtaining first reference object images of the reference object in different defocus states to obtain a set of reference object images; Calculating a third sharpness score for each first reference object image in the set of reference object images; Fitting a functional relationship between the sharpness change rate and the height change rate according to the highest sharpness score, the lowest sharpness score, and the third sharpness score; Determining the functional relationship between the sharpness change rate and the height change rate as a sharpness-height mapping relationship.

4. The method for measuring the thickness change amount of the target object to be measured according to claim 3, wherein, The adjusting the microscope Z-axis of the microscope according to the sharpness change amount and a preset threshold so that the microscope focuses on the reference object includes: Determining a height change amount corresponding to the sharpness change amount according to the sharpness-height mapping relationship; Comparing the height change amount with the preset threshold; When the height change amount is greater than the preset threshold, determining to adjust the microscope Z-axis; After controlling the microscope Z-axis to move a preset step length in a first direction, obtaining a second reference object image of the reference object after the movement and calculating a fourth sharpness score of the second reference object image; When the fourth sharpness score increases, determining that the thickness change direction of the target object to be measured is the same as the first direction, and controlling the microscope Z-axis to move according to the first direction to focus on the reference object; When the fourth sharpness score decreases, controlling the microscope Z-axis to move in a second direction, and performing the operation of obtaining a second reference object image of the reference object after the movement, where the second direction is opposite to the first direction.

5. The method for measuring the thickness change amount of the target object to be measured according to claim 4, wherein, The calculating the thickness change amount of the target object to be measured according to the sharpness change amount and the moving distance of the microscope Z-axis includes: When it is determined that the height change amount is less than the preset threshold, determining the thickness change amount according to the height change amount; When it is determined that the height change amount is greater than the preset threshold, obtain the moving distance of the Z-axis of the microscope; Determine the thickness change amount according to the height change amount and the moving distance of the Z-axis of the microscope.

6. The method for measuring the thickness change amount of the target object to be measured according to claim 5, wherein The determining the thickness change amount according to the height change amount and the moving distance of the Z-axis of the microscope includes: Determine a first moving distance of the Z-axis of the microscope moving in the first direction and a second moving distance moving in the second direction; Determine the total Z-axis moving distance of the Z-axis of the microscope according to the first moving distance and the second moving distance; Determine the thickness change amount according to the total Z-axis moving distance and the height change amount.

7. The method for measuring the thickness change amount of the target object to be measured according to claim 1, characterized in that, The preset threshold is an adjustable parameter set according to system characteristic parameters, and the system characteristic parameters include the clarity-height mapping relationship and the minimum movable resolution of the Z-axis of the microscope.

8. The method for measuring the thickness change amount of the target object to be measured according to claim 7, characterized in that, The preset threshold conforms to the linear relationship interval of the clarity-height mapping relationship, and the preset threshold is greater than the Z-axis minimum resolution.

9. The method for measuring the thickness change amount of the target object to be measured according to claim 1, wherein Before obtaining the current frame image and the previous frame image of the reference object, the method further includes: placing the reference object at the center of the test area, placing the target object to be measured below the reference object and in contact with the lower surface of the reference object; aligning the reference object through the microscope to set the current focus reference of the microscope, so that the microscope obtains the current frame image based on the current focus reference.

10. A thickness change amount measuring device for a target object to be measured, characterized in that, The device for placing the target object to be measured and the reference object includes a relatively fixed lower base and a movable upper cover. The reference object is arranged on the upper cover, is in contact with the target object to be measured, and generates displacement as the thickness of the target object to be measured changes.

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