Portable device and method for measuring crack width of cement product based on digital microscope

Abstract

The application relates to a digital microscope-based portable cement product crack width measuring device and method, and belongs to the field of digital microscope optical detection. The device comprises a portable device body, a telescopic cover plate, a dustproof cover, a digital microscopic imaging module, a lens barrel, a scale plate module and an automatic focusing module. The telescopic cover plate and the dustproof cover are installed on the portable device body. The lens barrel is installed in the portable device body. The digital microscopic imaging module is installed on the lens barrel. The scale plate module is installed at the bottom of the lens barrel. The automatic focusing module is installed on one side of the lens barrel. The crack width is identified through an automatic focusing method and a double-mode calibration method. In view of the limitations of the prior art, such as large visual and reading microscope error, low precision, difficulty in recording data, large environmental influence and the like, an improved physical scale plate is combined with a digital microscopic imaging system. Through mechanical structure innovation and algorithm optimization, double-mode calibration of the crack width is realized, and the problems of light transmission, dynamic adaptation and error control are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to a digital microscope-based portable cement product crack width measuring device and method, belonging to the field of digital microscope optical detection. BACKGROUND

[0002] Cement-based products such as concrete structures, prefabricated components, mortar layers, etc. have a common problem of cracks during use. Cracks not only show changes in the internal stress intensity of cement, but also pose a major threat to durability and safety. Moreover, cracks can accelerate the process of corrosion and destruction, ultimately leading to structural instability, failure to achieve the corresponding function, and shortened service life. Therefore, the measurement of crack width is crucial for engineering construction.

[0003] Existing crack width measurement mainly relies on manual visual inspection combined with a graduated magnifying glass, and is mainly achieved through a reading microscope with an optical source and a magnification of 80 times or more. However, there are the following problems:

[0004] 1. Large subjective error, low precision, and inability to record data.

[0005] 2. Affected by environmental light and lens distortion, and prone to cumulative error over long-term use.

[0006] 3. Poor dynamic adaptability: manual focusing of the objective lens makes it difficult to quickly adapt to different crack sizes.

[0007] Moreover, there are many limitations when using a graduated plate. Traditional graduated plates are mainly used for optical sighting equipment, but their light transmission rate is low (usually <70%) and the scale is prone to reflection, which can cause a decrease in image contrast in microscopic imaging and cannot adapt to different magnification requirements. SUMMARY

[0008] According to the problems described in the background, the present application aims to solve the problem of providing a digital microscope-based portable cement product crack width measuring device and method. In view of the limitations of existing technologies such as large visual and reading microscope error, low precision, difficulty in recording data, and large environmental impact, the improved physical graduated plate is combined with a digital microscopic imaging system. Through mechanical structure innovation and algorithm optimization, dual-mode calibration of crack width is achieved, and the problems of light transmission, dynamic adaptation, and error control are solved.

[0009] To achieve the above object, the application provides the following technical scheme: a portable cement product crack width measuring device based on a digital microscope, comprising a portable device body, an extension cover plate, a dust cover, a digital microscopic imaging module, a lens barrel, a scale plate module and an automatic focusing module, the portable device body is in a long strip style with a vertical projection in the shape of a water droplet, the upper part and the front end of the portable device body are provided with the extension cover plate and the dust cover, the extension cover plate is provided with bosses on both sides to control the limit, the lens barrel is installed in the portable device body, the digital microscopic imaging module is installed on the lens barrel, the scale plate module is installed at the bottom of the lens barrel, and the automatic focusing module is installed on one side of the lens barrel.

[0010] Specifically, the extension cover plate can adjust the field of view by extension, adapt to the detection requirements of different sizes and different field of view sizes, and the bosses on both sides of the extension cover plate can control the limit through the concave-convex structure of the bosses to prevent the cover plate from being too long to present a clear real image.

[0011] Preferably, the digital microscopic imaging module comprises an objective lens, a CMOS sensor and an LED ring light source, the objective lens is installed at the front end of the lens barrel, the CMOS sensor is installed at the rear end of the lens barrel, and the LED ring light source is installed at the front end of the objective lens.

[0012] Preferably, the scale plate module comprises a pull-out type clamping groove fixing seat and a scale plate, the pull-out type clamping groove fixing seat is installed at the rear end of the lens barrel and in front of the CMOS sensor of the digital microscopic imaging module, the scale plate is installed in the pull-out type clamping groove fixing seat, and the scale plate adopts a quartz glass substrate, and the surface is coated with a light shielding layer, an anti-reflection film and nano imprinting in sequence.

[0013] Specifically, the scale plate is located between the objective lens and the CMOS sensor, and the distance from the objective lens rear focal plane is 2-5 mm (the specific value is adjusted according to the focal length of the objective lens), so as to ensure that the imaging of the objective lens and the scale of the scale plate are accurately superimposed. The scale line on the scale plate directly blocks the light at the corresponding position through the light shielding layer, so as to form a superimposed image of the object image and the scale of the scale plate on the CMOS sensor, and the scale plate adopts a dynamic adaptation design, adds a scale plate replacement mechanism, is designed as a pull-out type clamping groove fixing seat structure, supports multiple scale plate specifications (such as 0.05 mm / grade, 0.1 mm / grade, etc.), improves the calibration flexibility, and can support custom scales, and adapts to different industry standards.

[0014] Meanwhile, the scale plate is a composite design, special materials and plating films are added on the scale plate to increase the light transmittance of the scale plate, increase the surface flatness, and reduce the problems of refraction and the like affecting the crack width measurement.

[0015] Preferably, the automatic focusing module comprises a micro motor and a synchronous belt, the micro motor is installed on one side of the lens barrel in the portable device body, the output end of the micro motor is connected with the synchronous belt, and the synchronous belt is used in cooperation with the lens barrel.

[0016] Specifically, the stepper motor is connected with the objective lens structure group through a synchronous belt to drive the objective lens to move (stroke 0-15 mm), and by replacing the reticle designed with different scales, an adjustable multi-view field range is realized to adapt to different crack length requirements.

[0017] The application also provides a cement product crack width portable measurement method based on a digital microscope, including the following steps:

[0018] (1) initializing the objective lens to the position closest to the CMOS;

[0019] (2) performing a coarse focusing stage;

[0020] (3) performing a fine focusing stage;

[0021] (4) after the focusing is completed, a double-mode calibration method is used to identify the crack width.

[0022] Preferably, the step (2) includes the following steps:

[0023] (2.1) moving the objective lens to collect images by the stepper motor;

[0024] (2.2) calculating the maximum sharpness F1 of the collected images and recording the position P1;

[0025] The step (3) includes the following steps:

[0026] (3.1) moving the objective lens according to the position P to collect images;

[0027] (3.2) determining the optimal focal length F2 according to the sharpness decrease;

[0028] (3.3) stopping the motor and locking the objective lens position, and the focusing is completed.

[0029] Specifically, the above automatic focusing method can automatically adjust the objective lens to achieve the effect of automatically presenting a clear view, which is more convenient and accurate. The objective lens moves, and image collection is performed once every certain range, and the sharpness of the image is calculated. After adjusting to a certain threshold, the maximum value of the sharpness in the adjustment range interval can be obtained, and the focal length corresponding to the maximum value of the sharpness is finally located to realize automatic focusing. At the same time, the cover plate extension structure adjusts the cover plate to adapt to the view field focal length and locks the cover plate length.

[0030] Preferably, the double-mode calibration method in the step (4) includes the following steps:

[0031] (4.1) reticle scale calibration;

[0032] (4.2) pixel size calibration.

[0033] Preferably, the step (4.1) comprises:

[0034] (4.1.1) placing a standard micrometer;

[0035] (4.1.2) adjusting the objective lens to make the scale clear;

[0036] (4.1.3) adjusting the device to align the scale with the reticle;

[0037] (4.1.4) aligning the left end scale and finding the overlapping point;

[0038] (4.1.5) calculating the actual physical size corresponding to the scale of the reticle;

[0039] (4.1.6) storing the calibration parameters.

[0040] Specifically, the actual physical size corresponding to the scale of the reticle is calibrated according to the calibration operation of the reading microscope. A high-precision standard ruler is placed in the field of view of the digital microscope. The device is rotated to make the scale of the reticle parallel to the scale of the standard ruler. The scale line at one end is aligned, and the scale line that overlaps each other is found. Since the physical size of the standard ruler is known, the actual physical size corresponding to the scale of the reticle can be calculated through the ratio of the scale of the standard ruler and the scale of the reticle. This calibration can provide a certain basis for the human eye to compare the crack width.

[0041] Preferably, the step (4.2) comprises:

[0042] (4.2.1) placing a standard grid;

[0043] (4.2.2) automatically focusing to make the grid clear;

[0044] (4.2.3) removing noise from the image through morphological filtering processing;

[0045] (4.2.4) detecting the intersection of the grid through Hough transformation;

[0046] (4.2.5) calculating the physical size of the pixel;

[0047] (4.2.6) storing the calibration parameters.

[0048] Specifically, the actual physical size corresponding to the pixel of the picture is calibrated. A standard pattern (such as a grid line) ruler is placed in the field of view of the digital microscope. The objective lens is adjusted to make the standard pattern ruler clear in the field of view. The picture in the field of view is collected. The specific grid line is automatically recognized through algorithm processing. The number of pixels is calculated. The actual physical size of a single pixel is determined through the physical size of the grid line. This calibration can ensure that the algorithm can automatically recognize and calculate the crack width.

[0049] Preferably, the step (4.2) is replaced with:

[0050] (4.2.7) Identify the reticle scale line in the image based on the actual physical size corresponding to the reticle scale;

[0051] (4.2.8) Measure the number of pixels between the scale lines and calculate;

[0052] (4.2.9) Store the calibration parameters.

[0053] The beneficial effects of the present application are:

[0054] 1. The reticle is located between the objective lens and the CMOS sensor, ensuring accurate superposition of the objective lens imaging and the reticle scale, and the reticle adds a pull-out clamping groove fixing seat structure, supporting multiple reticle specifications, improving calibration flexibility, and the reticle adds special materials and coating to increase the light transmittance of the reticle, while increasing the surface flatness, reducing the problem of affecting the crack width measurement caused by refraction, etc.

[0055] 2. The telescopic cover plate can adapt to detection requirements of different sizes and different field sizes, and the limit is controlled by the boss to prevent the cover plate from being too long to present a clear real image, enhancing the practicality.

[0056] 3. The stepper motor is connected to the lens barrel through a synchronous belt, which can drive the objective lens to move, and in the case of replacing reticles with different scale designs, it can realize adjustable multi-field range and adapt to different crack length requirements.

[0057] 4. The automatic focusing method can automatically adjust the objective lens to achieve the effect of automatically presenting a clear field of view, which is more convenient and accurate, and has high dynamic adaptability.

[0058] 5. The combination of the double-mode calibration method can solve the problems of light transmittance, dynamic adaptation and error control, the reticle scale calibration process can provide a certain basis for the human eye to compare crack width, the pixel size calibration process can ensure that the algorithm can automatically identify and calculate the crack width, the precision is high, the error is reduced, and the environmental factors are reduced, and the corresponding data can be stored and recorded. BRIEF DESCRIPTION OF DRAWINGS

[0059] Figure 1 is a structural schematic diagram of the device of the present application;

[0060] Figure 2 is a structural schematic diagram of the device of the present application;

[0061] Figure 3 is a flowchart of the method of the present application;

[0062] Figure 4 is a reticle scale calibration flowchart of the method of the present application;

[0063] Figure 5 Pixel size calibration flowchart for the method of the present application;

[0064] In the figure: 1 is the portable device body; 2 is the telescopic cover plate; 3 is the dust cover; 4 is the digital microscopic imaging module; 5 is the lens barrel; 6 is the graticule module; 7 is the automatic focusing module; 41 is the objective lens; 42 is the CMOS sensor; 43 is the LED ring light source; 61 is the pull-out card slot fixing seat; 62 is the graticule; 71 is the micro motor; 72 is the synchronous belt. DETAILED DESCRIPTION

[0065] The embodiments of the present application will be further described below with reference to the accompanying drawings:

[0066] Embodiment 1

[0067] As shown in Figure 1 and Figure 2 , the present application provides a portable cement product crack width measuring device based on a digital microscope, which comprises a portable device body 1, a telescopic cover plate 2, a dust cover 3, a digital microscopic imaging module 4, a lens barrel 5, a graticule module 6 and an automatic focusing module 7. The portable device body 1 is in the shape of a long strip with a vertical projection in the shape of a water droplet. The telescopic cover plate 2 and the dust cover 3 are installed on the upper part and the front end of the portable device body 1. The telescopic cover plate 2 has bosses on both sides to control the limit. The lens barrel 5 is installed in the portable device body 1. The digital microscopic imaging module 4 is installed on the lens barrel 5. The graticule module 6 is installed at the bottom of the lens barrel 5. The automatic focusing module 7 is installed on one side of the lens barrel 5.

[0068] Specifically, the telescopic cover plate 2 can adjust the field of view by telescoping to adapt to the detection needs of different sizes and different field of view sizes. The bosses designed on both sides of the telescopic cover plate 2 can control the limit through the concave-convex structure of the bosses to prevent the telescopic cover plate 2 from being too long to present a clear real image.

[0069] The digital microscopic imaging module 4 comprises an objective lens 41, a CMOS sensor 42 and an LED ring light source 43. The objective lens 41 is installed at the front end of the lens barrel 5. The CMOS sensor 42 is installed at the rear end of the lens barrel 5. The LED ring light source 43 is installed at the front end of the objective lens 41.

[0070] The graticule module 6 comprises a pull-out card slot fixing seat 61 and a graticule 62. The pull-out card slot fixing seat 61 is installed at the rear end of the lens barrel 5 and in front of the CMOS sensor 42 of the digital microscopic imaging module 4. The graticule 62 is installed in the pull-out card slot fixing seat 61. The graticule 62 adopts a quartz glass substrate, and the surface is coated with a light-shielding layer, an anti-reflection film and nano-imprinting in sequence.

[0071] The scale plate 62 as the optical calibration core component needs to meet the requirements of high light transmittance, low distortion and wear resistance. The quartz glass substrate is mainly used, the light transmittance is greater than or equal to 92%, the circular substrate with a diameter suitable for an optical microscope is cut, and the edge is slightly chamfered to prevent edge collapse and cutting hand; and the surface of the scale plate 62 is coated in sequence:

[0072] Light shielding layer: black chromium oxide (Cr2O3) plating film, thickness 50±5 nm, covering the scale area, ensuring that the light shielding rate is greater than or equal to 99%, and ensuring that the scale line can be superimposed and contrasted;

[0073] Antireflection film: MgF2 multilayer film (center wavelength 550 nm), covering the non-scale area, improving the overall light transmittance;

[0074] Nanoimprint process: etching scale lines on the light shielding layer to reduce light scattering;

[0075] For the scale design of the scale plate 62, it needs to adapt to the measurement requirements of different crack widths (assuming that the crack range is 0.02-5 mm), so it needs to meet three types of scale specifications:

[0076] Standard type: 0.05 mm / grade (total length 5 mm, 100 grades), suitable for 0.02-1 mm crack;

[0077] Extended type: 0.1 mm / grade (total length 10 mm, 100 grades), suitable for 1-5 mm crack;

[0078] Custom type: support user-defined scale (such as 0.02 mm / grade);

[0079] At the same time, for the scale layout, the main scale line is required to be 1 mm long, and the pitch is set according to the specification; the auxiliary scale line is provided with a lengthened line (1.5 mm long) every 5 grades, and a number is marked every 10 grades; the concentric circle calibration ring is used for installation and centering calibration.

[0080] The scale line on the scale plate 62 directly blocks the light at the corresponding position through the light shielding layer, and forms an overlay image of the object image on the CMOS sensor 42 and the scale of the scale plate 62,

[0081] The automatic focusing module 7 includes a micro motor 71 and a synchronous belt 72. The micro motor 71 is installed on one side of the lens barrel 5 in the portable device body 1. The output end of the micro motor 71 is connected with the synchronous belt 72. The synchronous belt 72 is used in cooperation with the lens barrel 5.

[0082] When using the device, first, the objective lens 41 is installed at the front end of the lens barrel 5, and the CMOS sensor 42 is fixed at the rear end of the lens barrel 5. A telescopic cover plate 2 that can be used to adjust the field of view is added to the objective lens 41, and the distance between the observed object and the objective lens 41 is limited to satisfy f<u<2f, where f represents the focal length of the objective lens 41, and u represents the object distance of the objective lens 41. Within this range, the observed object can form an inverted and enlarged real image on the CMOS sensor 42 through the objective lens 41;

[0083] Then, the reticle 62 is inserted into the pull-out clamping groove fixing seat 61, the optical axis of the objective lens 41 is aligned through the concentric circle calibration ring on the reticle 62, and the pull-out clamping groove fixing seat 61 is locked to ensure that the reticle 62 is parallel to the CMOS sensor 42;

[0084] For the installation and replacement of the reticle 62, first, the reticle 62 is pulled out of the pull-out clamping groove fixing seat 61, then a new reticle 62 is inserted, the new reticle 62 is pushed into the pull-out clamping groove fixing seat 61, and the type of the reticle 62 is set in the software. For the structure of the reticle 62 loaded with a magnetic mark and a Hall sensor, the type of the reticle 62 can be recognized through automatic reading of the Hall signal by the system;

[0085] Then, the LED ring light source 43 is installed at the front end of the objective lens 41, and a polarizer is placed between the LED ring light source 43 and the objective lens 41. The LED ring light source 43 is turned on, the scale line clarity in the image of the CMOS sensor 42 is observed, the angle of the reticle 62 is finely adjusted until the scale line is parallel to the image edge, and the image uniformity (the difference between the center and the edge brightness is ≤5%) is checked;

[0086] Then, the telescopic cover plate 2 adopts a push-pull sliding structure, and its length can be designed according to the detection range. The automatic focusing module 7 is added with a micro motor 71 and a synchronous belt 72 for controlling the automatic calculation of the focal length;

[0087] First, the length of the telescopic cover plate 2 is adjusted to match the current field of view, the whole measuring device is clamped on the measured object or the focusing object, the telescopic cover plate 2 is pushed and pulled, and the object distance u of the objective lens 41 and the focal length f of the objective lens 41 form a relationship of f<u<2f, that is, the telescopic cover plate 2 is adjusted within the focal length of f to 2f;

[0088] Then, the focusing program is started, the micro motor 71 is controlled to rotate, the micro motor 71 drives the synchronous belt 72 to move, and the objective lens 41 is extended so that a clear inverted and enlarged real image can be presented on the CMOS sensor 42;

[0089] When the focal length adjustment is completed, the system automatically controls the micro motor 71 to move the objective lens 41 to the best focal length position and stop moving, and then marks the gap according to the double-mode calibration method.

[0090] Embodiment 2

[0091] As Figure 3 shown, the application also provides a digital microscope-based portable measurement method for cement product crack width, comprising the following steps:

[0092] (1) initialize the objective lens to the position closest to the CMOS;

[0093] (2) perform a coarse focusing stage;

[0094] (3) perform a fine focusing stage;

[0095] (4) after focusing, identify the crack width by a dual-mode calibration method.

[0096] The step (2) comprises the following steps:

[0097] (2.1) collect images by moving the objective lens with a stepper motor;

[0098] Specifically, the stepper motor moves the objective lens at a constant speed (e.g., set to 1 mm / s), and collects one frame of image every 0.1 mm.

[0099] (2.2) calculate the maximum sharpness F1 of the collected images and record the position P1;

[0100] Specifically, calculate the sharpness F of the collected images, and define the sharpness evaluation function as follows:

[0101]

[0102] wherein, , is the Sobel operator gradient. Record the position P1 of the maximum value F1 of the current coarse focusing stage F.

[0103] The step (3) comprises the following steps:

[0104] (3.1) collect images by moving the objective lens according to the position P;

[0105] Specifically, based on the obtained P1, within the range of P1±0.5 mm, the objective lens moves with a step of 0.02 mm, and collects one frame of image each time.

[0106] (3.2) determine the optimal focal length F2 according to the sharpness decrease;

[0107] Specifically, when the sharpness F decreases continuously for 3 times, stop and take the maximum value position as the optimal focal length F2.

[0108] (3.3) stop the motor and lock the objective lens position, and the focusing is completed.

[0109] Specifically, the motor stops moving, the objective lens position is locked, and a "focusing complete" flag signal is transmitted.

[0110] The step (4) includes the following steps:

[0111] (4.1) reticle calibration;

[0112] (4.2) pixel size calibration.

[0113] As shown in Figure 4 , the step (4.1) includes:

[0114] (4.1.1) place a standard micrometer;

[0115] Specifically, a high-precision standard scale (such as a stage micrometer) is placed in the field of view of the reading microscope.

[0116] (4.1.2) adjust the objective lens to make the scale clear;

[0117] Specifically, the micrometer scale is Adjust the objective lens to make the standard scale clear.

[0118] (4.1.3) adjust the equipment to align the reticle with the scale line;

[0119] Specifically, rotate the reticle or digital microscope so that the reticle scale is parallel to the micrometer scale.

[0120] (4.1.4) align the left end scale line and find the overlapping point;

[0121] Specifically, move the micrometer or digital microscope so that the 0th grid on the left end of the reticle is aligned with the 0th grid on the micrometer.

[0122] (4.1.5) calculate the actual physical size corresponding to the reticle scale;

[0123] Specifically, find the first overlapping scale line to the right, and record the overlapping scale values of the reticle and the micrometer, respectively, with the reticle overlapping scale value being , and the micrometer overlapping scale value being ; calculate the actual physical size corresponding to the reticle scale:

[0124]

[0125] After calibration, the relative positions of the measured object, objective lens, reticle, and eyepiece are fixed, and the magnification is fixed. If the objective lens is adjusted, it must be recalibrated.

[0126] (4.1.6) store the calibration parameters.

[0127] As shown in Figure 5As shown, the step (4.2) comprises:

[0128] (4.2.1) Place the standard grid plate;

[0129] Specifically, the standard ruler is replaced by a standard grid plate with a known grid physical size.

[0130] (4.2.2) Auto focus to grid clear;

[0131] (4.2.3) Image denoising by morphological filtering processing;

[0132] Specifically, the image is collected, and morphological opening operation in image processing is performed on the collected image to remove noise and remove the interference of the scale.

[0133] (4.2.4) Hough transform detects grid intersection;

[0134] Specifically, the Hough transform in image processing is used to detect horizontal and vertical lines, and the intersection coordinate matrix is fitted.

[0135] (4.2.5) Calculate the physical size of the pixel;

[0136] Specifically, a recognized grid line is randomly selected, and the number of grid segments contained in the grid line is =18, the pixel distance (i.e. the number of pixels) contained in the grid line is calculated by image recognition, and the physical size of a straight grid is =0.2mm, then the actual physical size corresponding to the picture pixel is:

[0137]

[0138] (4.2.6) Store the calibration parameters.

[0139] The step (4.2) is replaced by:

[0140] (4.2.7) Identify the scale line of the scale plate in the image based on the actual physical size corresponding to the scale of the scale plate;

[0141] Specifically, based on the calibrated , the scale line of the scale plate in the image is identified.

[0142] (4.2.8) Measure the number of pixels between the scale lines and calculate;

[0143] Specifically, the number of pixels between the scale lines is measured, and

[0144]

[0145] (4.2.9) Store calibration parameters.

Claims

1. A portable device for measuring crack width of cement products based on a digital microscope, characterized in that: The portable device comprises a main body (1), a telescopic cover (2), a dust cover (3), a digital microscopic imaging module (4), a lens barrel (5), a reticle module (6) and an automatic focusing module (7), wherein the main body (1) of the portable device is a strip having a vertical projection in the shape of a water drop, the upper part and the front end of the main body (1) of the portable device are provided with a telescopic cover (2) and a dust cover (3), both sides of the telescopic cover (2) are provided with bosses for controlling the limit, the main body (1) of the portable device is provided with a lens barrel (5), the digital microscopic imaging module (4) is provided on the lens barrel (5), the reticle module (6) is provided at the bottom of the lens barrel (5), and the automatic focusing module (7) is provided on one side of the lens barrel (5); The digital microscopic imaging module (4) comprises: an objective lens (41), a CMOS sensor (42) and an LED annular light source (43), wherein the objective lens (41) is mounted at the front end of the lens barrel (5), the CMOS sensor (42) is mounted at the rear end of the lens barrel (5), and the LED annular light source (43) is mounted at the front end of the objective lens (41); The measuring method of the device comprises the following steps: (1) Initialize the objective lens to the position closest to the CMOS; (2) Coarse focusing stage; (3) Fine focusing stage; (4) After focusing is completed, the crack width is identified using a dual-mode calibration method; The dual-mode calibration method in step (4) includes the following steps: (4.1) Reticule scale calibration; (4.2) Pixel size calibration; The step (4.1) includes: (4.1.1) Place the standard micrometer; (4.1.2) Adjust the objective lens until the scale is clear; (4.1.3) Adjust the equipment so that the reticle is aligned with the scale lines; (4.1.4) Align the left end scale line and find the coincidence point; (4.1.5) Calculate the actual physical dimensions corresponding to the scale of the reticle; (4.1.6) Storage of calibration parameters; The step (4.2) includes: (4.2.1) Place the standard grid board; (4.2.2) Automatically adjust the focus until the grid is clear; (4.2.3) Denoise the image by morphological filtering; (4.2.4) Hough transform to detect grid intersections; (4.2.5) Calculate pixel physical size; (4.2.6) Store calibration parameters.

2. A portable cement product crack width measuring device based on a digital microscope according to claim 1, characterized in that: The graticule module (6) comprises a pull-out card slot fixing seat (61) and a graticule (62), wherein the pull-out card slot fixing seat (61) is mounted at the rear end of the lens barrel (5) and in front of the CMOS sensor (42) of the digital microscopic imaging module (4), and the graticule (62) is mounted in the pull-out card slot fixing seat (61), and the graticule (62) adopts a quartz glass substrate, and the surface is coated with a light shielding layer, an anti-reflection film and a nano-imprint.

3. The portable cement product crack width measuring device based on a digital microscope according to claim 1, characterized in that: The automatic focusing module (7) comprises a micro motor (71) and a synchronous belt (72). The micro motor (71) is mounted on one side of the lens barrel (5) in the portable device body (1). The output end of the micro motor (71) is connected to the synchronous belt (72), and the synchronous belt (72) is used in conjunction with the lens barrel (5).

4. The portable cement product crack width measuring device based on a digital microscope according to claim 1, characterized in that: The step (2) includes the following steps: (2.1) The objective lens is moved by a stepper motor to collect images; (2.2) Calculate the maximum resolution F1 of the captured image and record the position P1; The step (3) includes the following steps: (3.1) Move the objective lens according to position P to collect images; (3.2) Determine the optimal focal length F2 based on the decrease in clarity; (3.3) The motor stops and the objective lens position is locked, and the focusing is completed.

5. The portable cement product crack width measuring device based on a digital microscope according to claim 1, characterized in that: The step (4.2) is replaced by: (4.2.7) Identify reticle lines in an image based on the actual physical dimensions of the reticle scale; (4.2.8) Measure and calculate the number of pixels between scale lines; (4.2.9) Store calibration parameters.

Images