Absolute measurement device and method for dynamic crack change parameters

Abstract

The present invention discloses an absolute measurement device and method for dynamic crack change parameters. The device comprises a sensor body (9) and two photoelectric targets arranged on both sides of a crack to be measured on a structure, wherein the connection line between the two photoelectric targets is perpendicular to the direction of the crack; the sensor body comprises a housing (7) and an optical lens (1), an image sensor (2) and a core control unit (3) arranged inside the housing (7); the optical lens (1) aims at the photoelectric target, and a position-switching narrow-band filter (23) is arranged between the optical lens (1) and the image sensor (2); the transmission wavelength of the narrow-band filter matches the emission wavelength of the photoelectric target. The present invention obtains a first target image of a single target in the same field of view and a second target image of the entire crack in the field of view by time-sharing switching of the filter and controlling the opening and closing of the photoelectric target, thereby realizing the measurement of the absolute width of the crack in the field of view and its change over time.

Description

Technical Field

[0001] The invention belongs to the field of structural measurement, and in particular relates to an absolute measurement device and a crack measurement method for crack measurement of a large structure and crack dynamic change parameters. Background Art

[0002] In large infrastructure such as bridges, tunnels, and dams, cracks are one of the most serious diseases caused by environmental erosion, material aging, and long-term loads. Due to long-term effects, cracks may further develop and cause catastrophic accidents. Real-time, long-term, and accurate measurement of the change process of cracks is of great significance for the safety assessment, healthy operation, and preventive reinforcement of large facilities.

[0003] At present, the methods used for crack measurement mainly include: manual regular measurement, monitoring instrument inspection, and installation of traditional crack meters for long-term monitoring. These monitoring methods have different disadvantages. The efficiency of manual detection is low, and there are hidden dangers to personnel safety. Instrument inspection can only obtain data at that time, and the measurement accuracy is low. The installation of traditional crack meters requires connection and fixation with the main body of the structure at both ends of the crack. When the structure is subjected to external forces, such as bridges under vehicles and dams under water pressure, the structure will deform, and the sensors fixed on the structure will also deform, resulting in a decrease in measurement accuracy. In the field environment, changes in temperature and humidity are inevitable factors. Traditional sensors will deform due to the thermal instability of the material itself, which will also cause a decrease in measurement accuracy. The development and changes of cracks are related to real-time conditions. Traditional sensors have a slow response speed, making it difficult to obtain dynamic monitoring data, and cannot reflect the changes in cracks under special conditions.

[0004] With the development of image sensor imaging technology and image processing technology, various sensors based on image recognition have been widely used in the fields of displacement measurement, structural dimension detection, etc. The Chinese patent application number 201010240543.2, "A method and device for measuring the width of cracks in tunnel lining", discloses a method and device for measuring the width of cracks in tunnel lining, including collecting crack images with digital image sensors, image grayscale conversion, edge extraction, minimum distance calculation, etc. These methods of measuring surface cracks of structures using image recognition can improve measurement accuracy, response speed, realize non-contact measurement, and reduce the influence of the external environment. They are effective means to solve the problems existing in current measurement methods. However, image measurement gives the relative change of crack width in principle, and absolute measurement still needs series calibration. In addition, the image processing algorithm is complex and time-consuming, making it difficult to achieve fast and high-precision absolute measurement of crack changes.

[0005] Another patent applied for by our company - Crack dynamic change sensor and crack measurement method based on multi-target image processing (201811632196.0), discloses a method of setting multiple LED targets on both sides of the crack to perform absolute measurement of the crack width, realizing absolute measurement of single-point positions on both sides of the crack. The current measurement accuracy reaches 0.01mm and the response frequency is 10Hz. However, the problem is that it can only measure the relative change of the crack, but cannot obtain the absolute width of the crack and its change over time. Summary of the invention

[0006] The present invention proposes an absolute measurement device and method for the dynamic change parameters of cracks. By switching filters in time and measuring the target images when the target is turned on and off, a separate target image and a crack image in the field of view are obtained. The two are fused and calculated to obtain the absolute width of the crack in the field of view and its change with time.

[0007] The technical solution of the present invention is as follows:

[0008] An absolute measurement device for crack dynamic change parameters, characterized in that: it comprises a sensor body and two photoelectric targets arranged on both sides of a crack to be measured on a structure, and the connection line between the two photoelectric targets is perpendicular to the direction of the crack; the sensor body comprises a housing and an optical lens, an image sensor and a core control unit arranged inside the housing, the optical lens aims at the photoelectric target, and a position-switching narrow-band filter is arranged between the optical lens and the image sensor; the transmission wavelength of the narrow-band filter matches the emission wavelength of the photoelectric target;

[0009] A switching mechanism is installed on the casing to drive the narrow-band filter to switch its position; the core control unit controls the switch and switching mechanism of the photoelectric target, so that the image sensor acquires the first target image when the narrow-band filter is in front of the image sensor and the photoelectric target is turned on, and the second target image when the narrow-band filter is not in front of the image sensor and the photoelectric target is turned off, and then calculates the dynamic change value of the absolute width of the crack in the target field of view.

[0010] In the above-mentioned absolute measurement device for the dynamic change parameters of cracks, the switching mechanism is composed of an electromagnet and a mounting substrate. The electromagnet includes an electromagnetic coil, a spring and an armature. The electromagnetic coil drives the armature to extend and retract, thereby driving the mounting substrate to switch positions. The narrow-band filter is fixed on the mounting substrate.

[0011] In the above-mentioned absolute measurement device for the dynamic change parameters of cracks, a narrow-band filter and a substrate that transmits a wide spectrum are installed on the mounting substrate. When acquiring the second target image, the substrate is located between the image sensor and the optical lens.

[0012] In the above-mentioned absolute measurement device for dynamic change parameters of cracks, the sensor body further comprises a remote communication unit, and the remote communication unit transmits the processing result to a remote data center under the control of the core control unit.

[0013] In the above-mentioned absolute measurement device for dynamic crack change parameters, the sensor body also includes a power management unit, which, under the control of the core control unit, realizes the switching of the photoelectric target and the power-on and power-off of the electromagnetic coil.

[0014] In the above-mentioned absolute measurement device for the dynamic change parameters of cracks, a white light lamp is arranged at one end of the casing close to the structure to achieve target illumination.

[0015] In the above-mentioned absolute measurement device for the dynamic change parameters of cracks, the target is an LED lamp or a light emitting diode, and the output spectrum of the LED lamp or the light emitting diode is in the near-infrared band.

[0016] In the above-mentioned absolute measurement device for dynamic crack change parameters, the housing is fixed to the surface of the structure on one side of the slit through a fixing bracket, and the fixing bracket is provided with a long hole for fixing the sensor body to achieve the adjustment of the distance between the optical lens and the target.

[0017] A method for absolute measurement of crack dynamic change parameters comprises the following steps:

[0018] 【1】Parameter preset;

[0019] 【2】The measuring device is switched to the second target imaging mode: the optoelectronic target is turned off and the narrow-band filter is not in front of the image sensor;

[0020] 【3】Read the first frame of image data and perform image processing;

[0021] 【4】Obtain the position coordinates of the corresponding pixel points of the two edges of the crack on the image sensor;

[0022] [5] The measuring device is switched to the first target imaging mode: the optoelectronic target is turned on and the narrow-band filter is placed in front of the image sensor;

[0023] 【6】Read the second frame image data and perform image processing;

[0024] 【7】Calculate the coordinates of the target spot center position, determine the crack measurement line and its position at the pixel point of the image sensor;

[0025] 【8】Compare with the first frame image to obtain the pixel coordinate position of the intersection of the crack measurement line and the crack edge;

[0026] 【9】According to the target distance, the pixel coordinates of the target and the intersection, the absolute width of the crack is obtained;

[0027]

[10] Repeat steps [5] to [9] to obtain the absolute width values ​​of the cracks in frames 2 to n, which are the dynamic change values ​​of the absolute width of the cracks.

[0028] In the above-mentioned absolute measurement method of the dynamic change parameters of the crack, steps [1] to

[10] are repeated after each set period of time.

[0029] The technical effects of the present invention are as follows:

[0030] 1. The present invention acquires the first target image of a single target in the same field of view and the second target image of the entire crack in the field of view by switching the filter and controlling the opening and closing of the photoelectric target in time-sharing, and uses the absolute dynamic change value of the target spacing in the first target image as the absolute calibration of the relative value of the crack width in the second target image. The conditions and parameters of the secondary optical imaging remain consistent, thereby realizing the measurement of the absolute width of the crack in the field of view and its change over time. After each interval of several frames of the first target image, a frame of the second target image is acquired for data fusion processing to ensure the time resolution and sufficient accuracy of the entire system. The device has the characteristics of compact structure, easy installation, good stability, high measurement accuracy, fast time response, etc., and is suitable for real-time online precise measurement of cracks on the surface of structures.

[0031] 2. When acquiring the first target image, the present invention sets two photoelectric targets on both sides of the crack, and measures the distance between the set targets to replace the width of the crack to be measured, thereby obtaining the dynamic change parameters of the crack, which has the characteristics of high measurement accuracy and fast time response. When the photoelectric target is turned on, the narrow-band filter is used to filter the optical signal of the image sensor, thereby overcoming the influence of external background light on the background signal of the image sensor and the measurement result, and improving the dynamic range of the measurement signal.

[0032] 3. When acquiring the second target image, the present invention switches the narrow-band filter to a substrate that can transmit a wide spectrum while the photoelectric target is turned off, compensating for the effect of the thickness of the substrate where the narrow-band filter is coated on the image distortion, ensuring the consistency of the first target image and the second target image. At the same time, a white light lamp for compensating illumination is set at one end of the housing, so that clear crack images can be obtained both during the day and at night, ensuring the measurement accuracy of the crack.

[0033] 4. The present invention adopts a remote communication unit module to realize remote control of the sensor. The data is transmitted to the data center through a 4G wireless network or a broadband limited network. It can work around the clock in the wild without human supervision to realize remote systematic management. At the same time, the core control unit and storage processing unit are developed based on the DSP and ARM systems, making the entire system compact in structure, stable and reliable in performance, and suitable for remote long-term online measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the composition of the crack measuring device of the present invention;

[0035] Figure 2 It is a schematic diagram of the composition of a crack measuring device with a fill light in a specific embodiment;

[0036] Figure 3 This is a schematic diagram of the composition principle of the sensor circuit module of the present invention;

[0037] Figure 4 A schematic diagram of the principle of a second target image acquired by the image sensor of the present invention;

[0038] Figure 5 A schematic diagram of the principle of a first target image acquired by the image sensor of the present invention;

[0039] Figure 6 It is a schematic diagram of the fixing structure of the fixing bracket and the sensor body of the present invention;

[0040] Figure 7 It is a schematic diagram of the switching mechanism of the present invention;

[0041] Figure 8 It is a schematic diagram of the switching mechanism structure when the armature is extended according to the present invention;

[0042] Fig. 9 It is a schematic diagram of the switching mechanism structure when the armature is contracted in the present invention;

[0043] Fig.10 This is a flow chart for measuring and calculating the absolute width of a crack and its dynamic changes according to the present invention.

[0044] The accompanying drawings are marked as follows: 1—optical lens; 2—image sensor; 3—core control unit; 4—processing and storage unit; 5—power management unit; 6—remote communication unit; 7—housing; 9—sensor body; 10—crack; 11—structure; 12—target base; 13—fixed bracket; 15—field of view; 16—long hole; 20—switching mechanism; 21—electromagnetic coil; 22—armature; 23—narrowband filter; 24—substrate; 25—mounting substrate; 26—spring; 30—white light lamp; 81—first target; 82—second target. DETAILED DESCRIPTION

[0045] like Figures 1 to 3As shown, the crack dynamic change rapid measurement sensor of the present invention comprises a sensor body 9 and two photoelectric targets arranged on both sides of the crack to be measured on the structure, namely, a first target 81 and a second target 82. The connection line between the two photoelectric targets is perpendicular to the direction of the crack; the sensor body 9 comprises a housing 7 and an optical lens 1, an image sensor 2 and a core control unit 3 arranged inside the housing 7, and the optical lens 1 aims at the photoelectric target. The above is the basic composition of the existing crack measurement system.

[0046] The feature of the present invention is that a position-switching narrow-band filter 23 is arranged between the optical lens 1 and the image sensor 2; the transmission wavelength of the narrow-band filter matches the emission wavelength of the photoelectric target, and is used to filter out background light when the sun is irradiated during daytime operation, reduce the background signal of the image sensor 2, and ensure the dynamic range of the signal.

[0047] Figure 1 and Figure 2 The middle housing 7 is provided with a switching mechanism 20, which drives the narrowband filter 23 to switch positions and filter out background light. The core control unit 3 controls the switch of the photoelectric target and the switching mechanism 20, so that the image sensor 2 acquires the first target image when the narrowband filter 23 is in place and the photoelectric target is turned on, and the second target image when the narrowband filter 23 is not in place and the photoelectric target is turned off. The first target image obtains the dynamic change absolute parameter at the specific point position of the crack by processing the real-time absolute value of the position of the target light; the second target image obtains the image of the entire crack in the field of view, and then obtains the pixel position of the crack edge in the image sensor through the conventional image processing algorithm, and then calculates the absolute width value of the crack in the target field of view through the data fusion processing of the first target image and the second target image, and then obtains the absolute value of the dynamic change of the crack absolute width parameter over time through the processing and calculation of several frames of images. Since it takes a long time to process the second target image, a frame of the second target image is obtained after a certain interval of several frames of the first target image for data fusion processing to ensure the time resolution of the entire system.

[0048] Figure 2 As a specific implementation, a white light lamp 30 is provided at one end of the housing 8 close to the structure 11 to achieve target illumination. Its purpose is to provide fill light at night or when the sunlight is not bright enough, so as to obtain a clear second target image. At this time, the photoelectric target is turned off, and the image sensor captures the image of the crack. The purpose of using white light fill light is that the white light lamp is a wide-spectrum light source, and a clear color crack image can be obtained after fill light irradiation. If a narrow-spectrum LED lamp is used for fill light, the chromaticity deviation of the image will appear (similar to the color cast image captured by an infrared camera at night), resulting in unclear crack images, poor processing accuracy and poor measurement results.

[0049] Figure 3In the embodiment, the sensor circuit module includes an image sensor 2, a core control unit 3, a processing and storage unit 4, a power management unit 5 and a remote communication unit 6. The image sensor 2 adopts a CMOS or CCD sensor, and its pixel resolution is selected according to the measurement target. The sensor has a large measurement range and high measurement accuracy. The core control unit 3 controls the image sensor 2 to collect images of the target and the crack, and stores the data in the processing and storage unit 4. The processing and storage unit 4 processes the distance change value between the targets or the crack image, and displays it locally or transmits the processing result to a remote data center through the remote communication unit 6 to directly display the crack parameters; or according to the on-site implementation conditions, the core control unit 3 directly transmits the collected image data to the remote data center through the remote communication unit 6 for image processing, calibration and calculation and display of the dynamic parameters of the crack.

[0050] The core control unit 3 is the core unit of the image recognition crack sensor, which is constructed by DSP+ARM processor, including sensor trigger and timing control module, image data acquisition module, which is used to control image storage and processing, remote command implementation and data transmission. It has high integration, compact structure, high computing efficiency, stability and reliability, so that the sensor has the characteristics of fast time response.

[0051] Under the control of the core control unit 3, the processing storage unit 4 stores the image acquired by the image sensor 2 in the Flash memory, reads each frame of the spot image data in the memory through the 32-bit ARM processor, and identifies the center position of the target or the crack edge after graying the image, and finally calculates and gives the dynamic change parameters of the crack width.

[0052] The remote communication unit 6 is used for transmitting images and data and receiving remote control instructions. The remote communication unit 6 receives remote control instructions through a 4G mobile network or a wired broadband network, and sends the processed data to a remote data center to achieve remote measurement in an unmanned field environment.

[0053] The power management unit 5 is used for power supply control of the image sensor 2, the core control unit 3, the processing storage unit 4, the remote communication unit 6, and the peripheral components of the electromagnetic coil 21, the first target 81, the second target 82, and the white light lamp 30. The power management unit 6 can be controlled by the remote communication unit 6 command, and the power supply of each power supply unit is set and allocated according to the measurement time requirement to reduce the power consumption of the sensor.

[0054] Figure 4 and Figure 5Schematic diagrams of imaging of the image sensor field of view for the second target image and the first target image are given respectively. In the second target imaging mode, the photoelectric target is turned off, and the switching mechanism 20 switches the substrate 24 to before the image sensor 2. At this time, the image sensor field of view images the entire crack and the target shell image. If necessary, a clear crack image is obtained by supplementing the light with white light, and then the pixel position of the crack edge on the image sensor is obtained according to the conventional image algorithm.

[0055] In the first target imaging mode, the photoelectric target is powered on and the switching mechanism 20 switches the narrow-band filter 23 to the image sensor 2 to filter the background light. Due to the high brightness of the target, by adjusting the gain and threshold processing, only the image of the target is displayed on the image sensor, and the image of the crack is not displayed. The position change between the targets is obtained by image processing and calculation. Since the distance between the two installed targets is known, it is the absolute value of the specific position of the crack.

[0056] Figure 4 and Figure 5 A and B are the centroid positions of the two targets, AB is the crack measurement line, and C and D are the intersection positions of the line connecting the two points AB and the crack edge. When installing the target, the AB line should be as perpendicular as possible to the direction of the crack, and the target should be set at a position where the crack width changes slowly as much as possible. In this way, the change between CD can represent the change in crack width in the small area of ​​the target field of view. Since the change of cracks on large structures is manifested as the expansion and contraction of cracks, the distance change value between AB is equivalent to the distance change value between CD. Since the positions of points A and B can be accurately measured during installation and are known parameters, the absolute distance between CD can be obtained through the pixel positions of points A, B, C, and D on the image sensor. If the absolute change value between CD is fused into the image of the entire crack, and through the analysis and calculation of several frames of images, the absolute width change of the entire crack in the field of view can also be obtained.

[0057] The photoelectric target of the present invention adopts a light-emitting tube or infrared LED with an output spectrum in the near-infrared band, preferably an LED with a wavelength of 850nm. The central wavelength of the narrow-band filter is 850nm, and the half-width is 20-50nm. The narrow-band filter is optically coated on a glass substrate. In actual image processing, the thickness of the glass substrate will have a certain refraction effect on the image, thereby causing slight image distortion. In order to maintain the consistency between the first target image and the second target image, when acquiring the second target image, the present invention switches the narrow-band filter to a substrate that is transparent to a wide spectrum while the photoelectric target is turned off. The substrate is a glass substrate that is not coated with a narrow-band optical film, and its thickness and material are consistent. This solution compensates for the distortion effect of the thickness of the narrow-band filter coating substrate on the image, ensuring the consistency between the first target image and the second target image.

[0058] like Figure 6 As shown, after the target is installed, the base of the fixing bracket 13 is installed on one side of the crack 10. The fixing bracket 13 does not affect the change of the crack itself. Then the crack sensor body 9 is installed on the fixing bracket 13. The sensor body 9 can be fixed on the long hole 16 of the fixing bracket 13 by screws. Changing the position of the screws can adjust the distance between the optical lens and the target, and then adjust the field of view of the image sensor according to the field application. At the same time, by adjusting the focal length of the optical lens, ensure that the monitored crack 10 and the target are both included in the field of view area 15, and obtain a clear image, connect the power supply and remote communication cable, the sensor enters the working state, and sends the crack measurement data to the remote data terminal.

[0059] like Figure 7-9 As shown, the switching mechanism 20 is composed of an electromagnet and a mounting substrate 25. The electromagnet is a finished product purchased from a company in Nantong, including an electromagnetic coil 21, an armature 22 and a spring 26. The armature 22 can be extended and retracted up and down in the through hole inside the electromagnetic coil 21 by the action of the electromagnetic force and the spring. The head of the armature 22 is connected to the mounting substrate 25, and the connection method is bonding or other methods. When the armature 22 is extended and retracted, it drives the mounting substrate 25 to move up and down synchronously. A narrow-band filter 23 and a substrate 24 are installed on the mounting substrate 25. When the electromagnet is powered on, the armature 22 overcomes the force of the spring 26 and shrinks, so that the substrate 24 is facing the position of the image sensor to obtain the second target image; when the electromagnet is powered off, the spring 26 drives the armature 22 to extend, so that the narrow-band filter 23 is facing the position of the image sensor to obtain the first target image; this method has a simple and reliable structure, and it is convenient to realize the state switching of the two modes. The switching mechanism can also use other methods such as electromagnet plus lever to realize the position switching of the narrow-band filter. These are conventional mechanism changes and are not given examples here.

[0060] like Fig.10 and Figure 4 As shown, the steps for measuring the absolute crack width change value of the present invention are as follows:

[0061] 【1】Parameter preset;

[0062] It mainly presets the image sensor, target distance and calibration parameters in the processor.

[0063] 【2】The imaging system switches to the second target imaging mode: the optoelectronic target is turned off and the narrow-band filter is not in place;

[0064] Including closing the target, the switching mechanism switches the wide spectrum substrate to the front of the image sensor.

[0065] 【3】Read the first frame of image data and perform image processing;

[0066] Image processing includes traditional grayscale processing, binary segmentation and noise filtering.

[0067] 【4】Obtain the position coordinates of the corresponding pixel points of the two edges of the crack on the image sensor;

[0068] refer to Figure 4 , that is, the coordinate positions of the two edge curves on the sensor are obtained and stored for later processing.

[0069] 【5】The imaging system switches to the first target imaging mode: the optoelectronic target is turned on and the narrow-band filter is in place;

[0070] 【6】Read the second frame image data and perform image processing;

[0071] Image processing includes traditional grayscale processing, etc.

[0072] 【7】Calculate the coordinates of the target spot center position, determine the crack measurement line and its position at the pixel point of the image sensor;

[0073] refer to Figure 4 , AB is the crack measurement line. By calculation, the pixel coordinate position corresponding to each point on the AB line can be obtained.

[0074] 【8】Compare with the first frame image to obtain the pixel coordinate position of the intersection of the crack measurement line and the crack edge;

[0075] That is, the pixel coordinate position corresponding to the CD point is obtained.

[0076] 【9】According to the target distance, the pixel coordinates of the target and the intersection, the absolute width of the crack is obtained;

[0077] refer to Figure 4 , assuming that the pixel coordinates of points A, B, C, and D on the image sensor are (x a ,y a )、(x b ,y b )、(x c ,y c )、(x d ,y d ), p is the distance between the two targets AB known in advance, then the distance q1 between CD to be measured can be expressed as:

[0078]

[0079]

[10] Repeat steps [5] to [9] to obtain the absolute width values ​​of the cracks q2 to q2 for frames 2 to n. n , which is the dynamic change value of the absolute width of the crack;

[0080] As a further implementation method, steps [1] to

[10] are repeated every time interval T to perform mutual calibration between the first target image and the second target image, and the measured dynamic change value is corrected. Subsequent measurement results are calculated according to the new calibration parameters to improve measurement accuracy. The interval T can be 24 hours. At present, this measurement method and results can meet the existing monitoring requirements for cracks on large structures.

Claims

1. An absolute measurement device for dynamic crack change parameters, characterized in that: The sensor body comprises a sensor body (9) and two photoelectric targets arranged on both sides of a crack to be detected on a structure, wherein the connection line between the two photoelectric targets is perpendicular to the direction of the crack; the sensor body comprises a housing (7) and an optical lens (1), an image sensor (2) and a core control unit (3) arranged inside the housing (7); the optical lens (1) aims at the photoelectric target, and a position-switching narrow-band filter (23) is arranged between the optical lens (1) and the image sensor (2); the transmission wavelength of the narrow-band filter matches the emission wavelength of the photoelectric target; A switching mechanism (20) is installed on the housing (7) to drive the narrowband filter (23) to achieve position switching; the core control unit (3) controls the switch of the photoelectric target and the switching mechanism (20), so that the image sensor (2) acquires a first target image when the narrowband filter (23) is in front of the image sensor (2) and the photoelectric target is turned on, and a second target image when the narrowband filter (23) is not in front of the image sensor (2) and the photoelectric target is turned off, and then calculates the dynamic change value of the absolute width of the crack in the target field of view.

2. The absolute measurement device for crack dynamic change parameters according to claim 1, characterized in that: The switching mechanism (20) is composed of an electromagnet and a mounting substrate (25). The electromagnet includes an electromagnetic coil (21), a spring (26) and an armature (22). The electromagnetic coil (21) drives the armature (22) to expand and contract, thereby driving the mounting substrate (25) to switch positions. The narrowband filter (23) is fixed on the mounting substrate (25).

3. The absolute measurement device for crack dynamic change parameters according to claim 2, characterized in that: A narrowband filter (23) and a substrate (24) transmitting a wide spectrum are mounted on the mounting substrate (25); when acquiring a second target image, the substrate (24) is located between the image sensor (2) and the optical lens (1).

4. The absolute measurement device for crack dynamic change parameters according to any one of claims 1 to 3, characterized in that: The sensor body also includes a remote communication unit (6), which transmits the processing results to a remote data center under the control of the core control unit (3).

5. The absolute measurement device for crack dynamic change parameters according to any one of claims 1 to 3, characterized in that: The sensor body also includes a power management unit (5) which, under the control of the core control unit (3), realizes the switching of the photoelectric target and the power-on and power-off of the electromagnetic coil (21).

6. The absolute measurement device for crack dynamic change parameters according to any one of claims 1 to 3, characterized in that: A white light lamp (30) is arranged at one end of the casing (7) close to the structure (11) to achieve target illumination.

7. The absolute measurement device for crack dynamic change parameters according to any one of claims 1 to 3, characterized in that: The target is an LED lamp or a light emitting diode, and the output spectrum of the LED lamp or the light emitting diode is a near infrared band.

8. The absolute measurement device for crack dynamic change parameters according to any one of claims 1 to 3, characterized in that: The housing (7) is fixed to the surface of the structure (11) on one side of the slit via a fixing bracket (13), and the fixing bracket (13) is provided with a long hole for fixing the sensor body, so as to adjust the distance between the optical lens (1) and the target.

9. A method for absolutely measuring a crack dynamic change parameter using the absolute measurement device for crack dynamic change parameter according to any one of claims 1 to 8, comprising the following steps: 【1】Parameter preset; 【2】The measuring device is switched to the second target imaging mode: the optoelectronic target is turned off and the narrow-band filter is not in front of the image sensor; 【3】Read the first frame of image data and perform image processing; 【4】Obtain the position coordinates of the corresponding pixel points of the two edges of the crack on the image sensor; [5] The measuring device is switched to the first target imaging mode: the optoelectronic target is turned on and the narrow-band filter is placed in front of the image sensor; 【6】Read the second frame image data and perform image processing; 【7】Calculate the coordinates of the target spot center position, determine the crack measurement line and its position at the pixel point of the image sensor; 【8】Compare with the first frame image to obtain the pixel coordinate position of the intersection of the crack measurement line and the crack edge; 【9】According to the target distance, the pixel coordinates of the target and the intersection, the absolute width of the crack is obtained; [10] Repeat steps [5] to [9] to obtain the absolute width values ​​of the cracks in frames 2 to n, which are the dynamic change values ​​of the absolute width of the cracks.

10. The absolute measurement method of crack dynamic change parameters according to claim 9, characterized in that: Repeat steps [1] to [10] after a set period of time.

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