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

Abstract

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

Description

Technical Field

[0001] The invention relates to a portable measuring device and method for crack width of cement products based on a digital microscope, and belongs to the field of digital microscope optical detection. Background Art

[0002] Cracks are a common problem in cement-based products, such as concrete structures, precast components, and mortar layers, during use. Cracks not only indicate changes in stress intensity within the cement but also pose a significant threat to durability and safety. Cracks can also accelerate corrosion and damage, ultimately leading to structural instability, functional failure, and shortened service life. Therefore, measuring crack width is crucial for engineering construction.

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

[0004] 1. Defects such as large subjective error, low accuracy, and inability to record data.

[0005] 2. Affected by ambient light and lens distortion, long-term use is prone to cumulative errors;

[0006] 3. Poor dynamic adaptability: The objective lens needs to be manually focused, which makes it difficult to quickly adapt to different crack sizes;

[0007] There are also many limitations when using reticles. Traditional reticles are mostly used in optical aiming devices, but they have low light transmittance (usually <70%) and the scales are easily reflective, which can easily lead to a decrease in image contrast in microscopic imaging and cannot adapt to different magnification requirements. Summary of the Invention

[0008] Based on the problem described in the background, the problem to be solved by the present invention is: to provide a portable measurement device and method for the width of cracks in cement products based on a digital microscope. In view of the limitations of the existing technology such as large errors, low precision, difficulty in recording data, and large environmental impact of visual inspection and reading microscopes, an improved physical graticule 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 transmittance, dynamic adaptation and error control are solved.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solutions: a portable device for measuring the width of cracks in cement products based on a digital microscope is provided, comprising a portable device body, a telescopic cover, a dust cover, a digital microscopic imaging module, a lens barrel, a graticule module and an automatic focusing module. The portable device body is a long strip with a vertical projection in the shape of a water droplet. The telescopic cover and the dust cover are installed on the upper part and the front end of the portable device body. There are bosses on both sides of the telescopic cover 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 graticule 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 telescopic cover can adjust the field of view by telescoping to meet the detection requirements of different sizes and fields of view. Bosses are designed on both sides of the upper cover of the telescopic cover, and the concave and convex structure of the bosses can be used to control the limit to prevent the cover from being too long to present a clear real image.

[0011] Preferably, the digital microscopic imaging module includes: 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 graticule module includes a pull-out card slot fixing seat and a graticule, the pull-out card slot fixing seat is installed at the rear end of the lens barrel and in front of the CMOS sensor of the digital microscope imaging module, the graticule is installed in the pull-out card slot fixing seat, and the graticule 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 reticle is located between the objective lens and the CMOS sensor, 2-5 mm from the objective lens's rear focal plane (the specific value is adjusted according to the objective lens' focal length), ensuring precise superposition of the objective lens image and the reticle scale. The scale lines on the reticle directly block light at corresponding positions through a light-shielding layer, forming a superimposed image of the object image and the reticle scale on the CMOS sensor. The reticle also adopts a dynamic adaptive design, adding a reticle replacement mechanism and a pull-out card slot fixed structure. It supports a variety of reticle specifications (such as 0.05 mm / grid, 0.1 mm / grid, etc.), improving calibration flexibility. It also supports custom scales to adapt to different industry standards.

[0014] At the same time, the graticule adopts a composite design. By adding special materials and coatings to the graticule, the light transmittance of the graticule is increased, while the surface flatness is increased and the problems such as refraction that affect the crack width measurement are reduced.

[0015] Preferably, the automatic focusing module includes 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 to the synchronous belt, and the synchronous belt is used in conjunction with the lens barrel.

[0016] Specifically, the stepper motor and the objective lens structure group are connected through a synchronous belt to drive the objective lens to move (stroke 0-15 mm). By replacing the graticule with different scale designs, an adjustable multi-field range can be achieved to adapt to different crack length requirements.

[0017] The present application also provides a portable method for measuring crack width of cement products based on a digital microscope, comprising the following steps:

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

[0019] (2) Coarse focusing stage;

[0020] (3) Fine focusing stage;

[0021] (4) After focusing is completed, the crack width is identified using a dual-mode calibration method.

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

[0023] (2.1) The objective lens is moved by a stepper motor to collect images;

[0024] (2.2) Calculate the maximum resolution F1 of the captured image and record the position P1;

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

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

[0027] (3.2) Determine the optimal focal length F2 based on the decrease in clarity;

[0028] (3.3) The motor stops and the objective lens position is locked, and the focusing is completed.

[0029] Specifically, the aforementioned autofocus method can automatically adjust the objective lens to achieve a clear field of view, providing greater convenience and accuracy. The objective lens moves, capturing an image each time it moves within a certain range. The image clarity is calculated, and after adjusting to a certain threshold, the maximum clarity within the adjustment range is obtained. The focal length corresponding to this maximum clarity is then determined, achieving automatic focusing. Simultaneously, the cover plate's telescopic structure adjusts the cover plate to the focal length of the field of view and locks the cover plate's length.

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

[0031] (4.1) Reticule scale calibration;

[0032] (4.2) Pixel size calibration.

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

[0034] (4.1.1) Place the standard micrometer;

[0035] (4.1.2) Adjust the objective lens until the scale is clear;

[0036] (4.1.3) Adjust the equipment so that the reticle is aligned with the scale lines;

[0037] (4.1.4) Align the left end scale line and find the coincidence point;

[0038] (4.1.5) Calculate the actual physical dimensions corresponding to the scale of the reticle;

[0039] (4.1.6) Store calibration parameters.

[0040] Specifically, to calibrate the actual physical dimensions corresponding to the reticle graduations, follow the same calibration procedures as for a reading microscope. Place a high-precision standard ruler under the digital microscope's field of view, rotate the device so that the reticle graduations are parallel to the standard ruler graduations, align one end of the graduations, and find the overlapping graduations. Since the physical dimensions of the standard ruler are known, the ratio of the standard ruler graduations to the reticle graduations can be used to calculate the actual physical dimensions corresponding to the reticle graduations. This calibration provides a basis for comparing crack widths to the human eye.

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

[0042] (4.2.1) Place the standard grid board;

[0043] (4.2.2) Automatically adjust the focus until the grid is clear;

[0044] (4.2.3) Denoise the image by morphological filtering;

[0045] (4.2.4) Hough transform to detect grid intersections;

[0046] (4.2.5) Calculate pixel physical size;

[0047] (4.2.6) Store calibration parameters.

[0048] Specifically, the actual physical size corresponding to image pixels is determined by placing a ruler with a standard pattern (such as grid lines) under the field of view of a digital microscope. The objective lens is adjusted to make the standard ruler pattern clear in the field of view. An image is captured within the field of view, and the algorithm automatically identifies specific grid lines, calculates the number of pixels within them, and determines the actual physical size of individual pixels based on the physical size of the grid lines. This calibration ensures that the algorithm can automatically identify and calculate crack widths.

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

[0050] (4.2.7) Identify reticle lines in an image based on the actual physical dimensions of the reticle scale;

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

[0052] (4.2.9) Store calibration parameters.

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

[0054] 1. The reticle is placed between the objective lens and the CMOS sensor to ensure that the objective lens image and the reticle scale are accurately superimposed. The reticle is equipped with a pull-out card slot fixed seat structure to support a variety of reticle specifications and improve calibration flexibility. At the same time, special materials and coatings are added to the reticle to increase the light transmittance of the reticle, while improving the surface flatness and reducing refraction and other issues that affect crack width measurement.

[0055] 2. The telescopic cover can adapt to the detection needs of different sizes and different fields of view, and the limit control by the boss can prevent the cover from being too long to present a clear real image, thereby enhancing practicality.

[0056] 3. The stepper motor is connected to the lens barrel through a synchronous belt, which can drive the objective lens to move. By replacing the graticule with different scale designs, it can achieve an adjustable multi-field range to adapt to different crack length requirements.

[0057] 4. 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 dual-mode calibration methods 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 the crack width. The pixel size calibration process can ensure that the algorithm can automatically identify and calculate the crack width with high accuracy, reduce errors, and reduce environmental factors. The corresponding data can be stored and recorded. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0061] Figure 3 Schematic diagram of the process of the present invention;

[0062] Figure 4 This is a flow chart of the reticle scale calibration method of the present invention;

[0063] Figure 5 This is a flowchart of pixel size calibration of the method of the present invention;

[0064] In the figure: 1 is the portable device body; 2 is the retractable cover; 3 is the dust cover; 4 is the digital microscope imaging module; 5 is the lens barrel; 6 is the reticle module; 7 is the autofocus 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 reticle; 71 is the micro motor; 72 is the timing belt. DETAILED DESCRIPTION

[0065] The embodiments of the present invention are further described below with reference to the accompanying drawings:

[0066] Example 1

[0067] like Figure 1 and Figure 2 As shown, the present invention provides a portable measuring device for the width of cracks in cement products based on a digital microscope, comprising a portable device body 1, a telescopic cover 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 a long strip with a vertical projection in the shape of a water droplet. The telescopic cover 2 and the dust cover 3 are installed on the upper part and the front end of the portable device body 1. Bosses are provided on both sides of the telescopic cover 2 to control the limit. The lens barrel 5 is installed in the portable device body 1, and 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, and the automatic focusing module 7 is installed on one side of the lens barrel 5.

[0068] Specifically, the telescopic cover 2 can adjust the field of view by telescoping to meet the detection requirements of different sizes and fields of view. Bosses are designed on both sides of the upper cover of the telescopic cover 2, and the limit can be controlled by the concave and convex structure of the bosses to prevent the telescopic cover 2 from being too long to present a clear real image.

[0069] The digital microscopic imaging module 4 includes: 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, and the LED ring light source 43 is installed at the front end of the objective lens 41.

[0070] The reticle module 6 includes a pull-out card slot fixing seat 61 and a reticle 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 microscope imaging module 4. The reticle 62 is installed in the pull-out card slot fixing seat 61. The reticle 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 reticle 62, as a core component for optical calibration, must meet the requirements of high light transmittance, low distortion, and wear resistance. It is mainly made of a quartz glass substrate with a light transmittance of ≥92%. It is cut into a circular substrate with a diameter suitable for optical microscopes, and the edges are slightly chamfered to prevent chipping and cuts. The surface of the reticle 62 is coated in the following order:

[0072] Light-shielding layer: Black chromium oxide (Cr2O3) coating, thickness 50±5 nm, covering the scale area, ensuring a light-shielding rate of ≥99% and ensuring that the scale lines can be superimposed and contrasted;

[0073] Anti-reflection coating: MgF2 multilayer film (central wavelength 550 nm), covering the non-scale area to improve overall transmittance;

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

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

[0076] Standard type: 0.05 mm / grid (total length 5 mm, 100 grids in total), suitable for cracks of 0.02-1 mm;

[0077] Extended type: 0.1 mm / grid (total length 10 mm, 100 grids in total), suitable for 1-5 mm cracks;

[0078] Customized: supports user-defined scale (such as 0.02 mm / division);

[0079] At the same time, for the scale layout, the main scale line is required to be 1 mm long and the spacing is set according to the specifications; an extension line (1.5 mm long) is set every 5 grids of the auxiliary scale line, and numbers are marked every 10 grids; concentric circle calibration rings are used for installation and centering calibration.

[0080] The scale lines on the reticle 62 directly block the light at the corresponding position through the light shielding layer, forming a superimposed image of the object image plus the scale of the reticle 62 on the CMOS sensor 42.

[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 to the synchronous belt 72 , which is used in conjunction with the lens barrel 5 .

[0082] When using this device, first install the objective lens 41 at the front end of the lens barrel 5, and fix the CMOS sensor 42 at the rear end of the lens barrel 5. And add a telescopic cover plate 2 that can be used to adjust the field of view to the objective lens 41, restricting the distance between the observed object and the objective lens 41 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 magnified real image on the CMOS sensor 42 through the objective lens 41;

[0083] Then insert the reticle 62 into the draw-type card slot fixing seat 61, align the optical axis of the objective lens 41 through the concentric calibration ring on the reticle 62, and lock the draw-type card slot fixing seat 61 to ensure that the reticle 62 is parallel to the CMOS sensor 42;

[0084] For the installation and replacement of the reticle 62, first pull out the reticle 62 from the draw-type card slot fixing seat 61, then insert a new reticle 62, push the new reticle 62 into the draw-type card slot fixing seat 61, set the model of the reticle 62 in the software. For the structure of the reticle 62 equipped with magnetic marks and Hall sensors, the Hall signal can be automatically read by the system to identify the model of the reticle 62;

[0085] Next, install the LED ring light source 43 at the front end of the objective lens 41, and place the polarizer between the LED ring light source 43 and the objective lens 41. Light up the LED ring light source 43, observe the clarity of the scale line in the image of the CMOS sensor 42, finely adjust the angle of the reticle 62 until the scale line is parallel to the image edge, and check the image uniformity (the brightness difference between the center and the edge ≤ 5%);

[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 autofocus module 7 adds a micro motor 71 and a synchronous belt 72 for controlling the automatic calculation of the focal length;

[0087] Among them, first adjust the telescopic cover plate 2 so that its length can match the current field of view, clamp the whole measuring device on the measured object or the focusing object, push and pull the telescopic cover plate 2 to form a relationship of f < u < 2f between the object distance u of the objective lens 41 and the focal length f of the objective lens 41, that is, adjust the telescopic cover plate 2 within the focal length range from f to 2f;

[0088] Then start the focusing program, control the rotation of the micro motor 71, the micro motor 71 drives the synchronous belt 72 to move, and drives the objective lens 41 to extend, so that a clear inverted and magnified 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 drive the objective lens 41 to move to the optimal focal length position and stop moving, and then stores the side beam marks of the gap according to the dual-mode calibration method.

[0090] Embodiment 2

[0091] like Figure 3 As shown, the present application also provides a portable method for measuring the width of cracks in cement products based on a digital microscope, comprising the following steps:

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

[0093] (2) Coarse focusing stage;

[0094] (3) Fine focusing stage;

[0095] (4) After focusing is completed, the crack width is identified using a dual-mode calibration method.

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

[0097] (2.1) The objective lens is moved by a stepper motor to collect images;

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

[0099] (2.2) Calculate the maximum resolution F1 of the captured image and record the position P1;

[0100] Specifically, the clarity F of the captured image is calculated, and the clarity evaluation function is defined as follows:

[0101]

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

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

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

[0105] Specifically, based on the obtained P1, within the range of P1±0.5 mm, the objective lens movement step is reduced to 0.02 mm, and one frame of image is collected each time it moves.

[0106] (3.2) Determine the optimal focal length F2 based on the decrease in clarity;

[0107] Specifically, when the clarity F drops three times in a row, it stops and the maximum value position is taken as the optimal focal length F2.

[0108] (3.3) The motor stops and the objective lens position is locked, and the focusing is completed.

[0109] Specifically, the motor stops moving, locks the objective lens position, and transmits a "focusing completed" mark signal.

[0110] The dual-mode calibration method in step (4) includes the following steps:

[0111] (4.1) Reticule scale calibration;

[0112] (4.2) Pixel size calibration.

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

[0114] (4.1.1) Place the standard micrometer;

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

[0116] (4.1.2) Adjust the objective lens until the scale is clear;

[0117] Specifically, the micrometer scale is Adjust the objective lens so that the standard scale is clear.

[0118] (4.1.3) Adjust the equipment so that the reticle is aligned with the scale lines;

[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 coincidence point;

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

[0122] (4.1.5) Calculate the actual physical dimensions corresponding to the scale of the reticle;

[0123] Specifically, look to the right for the first overlapping scale line, and record the scale values ​​of the scale plate and the micrometer that overlap. The scale value of the scale plate that overlaps is , the micrometer coincidence scale value is ; Calculate the actual physical size corresponding to the scale of the reticle:

[0124]

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

[0126] (4.1.6) Store calibration parameters.

[0127] like Figure 5As shown, the step (4.2) includes:

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

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

[0130] (4.2.2) Automatically adjust the focus until the grid is clear;

[0131] (4.2.3) Denoise the image by morphological filtering;

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

[0133] (4.2.4) Hough transform to detect grid intersections;

[0134] Specifically, the horizontal and vertical lines are detected by Hough transform in image processing, and the intersection coordinate matrix is ​​fitted.

[0135] (4.2.5) Calculate pixel physical size;

[0136] Specifically, a segment of grid line is randomly selected and identified, and the number of grid segments contained in the segment of grid line is =18, calculate the pixel distance it contains through image recognition (ie, the number of pixels), and the physical size of each grid is =0.2mm, then the actual physical size of the image pixel corresponds to for:

[0137] (4.2.6) Store calibration parameters.

[0138] 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; Specifically, based on the calibrated , identify the scale lines of the reticle in the image.

[0139] (4.2.8) Measure and calculate the number of pixels between scale lines; Specifically, measure the number of pixels between scale lines ,calculate

[0140] (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). 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 position 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).

2. A portable cement product crack width measuring device based on a digital microscope according to claim 1, characterized in that: 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).

3. The 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.

4. 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).

5. A portable measurement method for crack width of cement products based on a digital microscope, characterized in that: The following steps are involved: (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.

6. A portable method for measuring crack width of cement products based on a digital microscope according to claim 5, 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.

7. A portable method for measuring crack width of cement products based on a digital microscope according to claim 5, characterized in that: The dual-mode calibration method in step (4) includes the following steps: (4.1) Reticule scale calibration; (4.2) Pixel size calibration.

8. The portable measurement method for crack width of cement products based on a digital microscope according to claim 5, characterized in that: 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) Store calibration parameters.

9. The portable method for measuring crack width of cement products based on a digital microscope according to claim 5, characterized in that: 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.

10. A portable method for measuring crack width of cement products based on a digital microscope according to claim 9, 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.

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