High-precision online thickness measuring device and thickness measuring method

Abstract

The invention belongs to the technical field of online steel plate thickness measurement application, and discloses a high-precision online thickness measuring device and a thickness measuring method. When a detected steel plate passes through a detection area, the TOF laser distance measuring sensor is firstly used for carrying out preliminary measurement and positioning, the thickness value of the detected steel plate is roughly determined, then according to the measured thickness value, the industrial camera with the measurement range covering the thickness value is selected for shooting, and small-range accurate measurement is carried out in combination with the point light source. Therefore, the requirement for high-precision measurement of the thickness of the steel plate is met. The device and the method have higher measurement precision and wider detection range, and particularly during high-temperature steel plate measurement and steel plate measurement with larger warping amplitude, the longer measurement distance can play a better role in protecting equipment instruments, so that the service life of the device is prolonged, and the reliability of the device is indirectly improved.

Description

Technical Field

[0001] The invention relates to the technical field of online steel plate thickness measurement applications, and in particular to a high-precision online thickness measuring device and a thickness measuring method. Background Art

[0002] In the field of steel plate processing and manufacturing, online steel plate thickness measurement is an indispensable inspection process, which mainly plays the following roles:

[0003] 1) Thickness specification calibration. Compare the measured thickness with the set thickness issued by the production plan to check whether the actual information is consistent with the planned information and confirm whether the tolerance range meets the standard.

[0004] 2) Overlapping measurement. Due to crane hoisting and other reasons, there are multiple steel plates stacked together, which will lead to substandard production and processing technology. In serious cases, the steel plates will get stuck in the equipment, causing equipment damage and affecting production. The thickness measurement can detect the overlap.

[0005] 3) Warp measurement. Steel plates with warping may get stuck when entering some processing equipment due to excessive warping, which seriously affects the production rhythm and equipment life. Through thickness measurement, it can be determined whether the maximum height of the steel plate warping exceeds the maximum setting value allowed by the equipment, thereby avoiding accidents.

[0006] At present, the thickness measurement of online steel plates mainly adopts the non-contact measurement method based on laser distance measurement sensors: a group of laser distance measurement sensors are set up at the gap between the production rollers, and the upper and lower laser distance measurement sensors are used to shoot each other. Then, the thickness of the steel plate is calculated by converting the range feedback from the sensors. The effect diagram is shown in the figure below. Figure 1 As shown, the length of A is pre-calibrated, and then when the steel plate passes through the detection area, the upper and lower opposing measuring devices start detection, and the feedback range readings are: B1, B2, and the thickness of the steel plate H = A-(B1+B2).

[0007] Laser ranging sensors generally use two technical principles:

[0008] One is TOF (Time of Flight) laser ranging. In the time flight measurement method, a laser pulse is emitted by a laser, and the emission time is recorded by a timer. The return light is received by a receiver, and the return time is recorded by a timer. The flight time of the light is obtained by subtracting the two times. The speed of light is constant, so the distance can be calculated when the speed and time are known. The main advantage of TOF laser ranging is that the measurement range is large, ranging from millimeters to kilometers. When the measurement distance changes, the measurement accuracy is less affected by the change; the disadvantage is that the accuracy is limited. At present, the highest accuracy of the measurement equipment using this method can only reach the millimeter level.

[0009] The other is laser triangulation distance measurement. This is a measurement method that calculates the coordinates of each point on the surface of the target object by measuring the incident angle and reflection angle of the light beam and combining the principles of geometric trigonometry. This method usually uses the reflection relationship between the laser beam and the target surface to determine the position of each point on the target object by observing the angle between the incident beam and the reflected beam. The advantage is high accuracy at close distances, and the disadvantage is that it is affected by angle changes and the depth of field of the sensor. Usually, the higher the detection accuracy required, the smaller the measurement range. If you want to ensure micron-level measurement accuracy, the maximum measurement range can only be tens of millimeters.

[0010] At present, the thickness specifications of steel plates that can be produced by steel plate production lines are usually between 2mm-150mm. The warping of the steel plates must also be considered. The measurement height range generally needs to meet 0mm-200mm, while also ensuring the micron-level measurement accuracy requirements.

[0011] If the TOF-based laser ranging method is used, the accuracy can only reach the millimeter level, the measurement error is large, the accuracy is low, and it cannot meet the required measurement accuracy requirements; if the laser triangulation ranging method is used, the measurement range is short and cannot meet the measurement range requirements.

[0012] In response to the above problems and current situation, the present invention proposes a high-precision online steel plate thickness measurement device and method, which combines the advantages of the above two measurement methods to realize online, large-range, fast, micron-level precision steel plate thickness measurement, and is suitable for steel plate production application scenarios with high measurement accuracy requirements. Summary of the invention

[0013] The present invention provides a high-precision online thickness measuring device and a thickness measuring method, which realize a large-range, online and high-precision steel plate thickness measurement based on the coordinated work of TOF laser ranging and triangulation laser ranging.

[0014] The technical solution of the present invention is as follows: a high-precision online thickness measuring device, comprising a support frame 1 and a measuring instrument 2;

[0015] The support frame 1 is a C-shaped frame structure, including a column and two crossbeams; the crossbeams are respectively located on the upper and lower sides of the roller table reference horizontal plane 3, and are used to fix the measuring instrument 2;

[0016] The measuring instrument 2 includes a TOF distance measuring sensor 4, a point laser light source 5 and a plurality of industrial cameras 6; the industrial cameras 6 cover the measurement work of different thickness ranges; the total measurement thickness range requirement is M, the number of industrial cameras 6 is N, and the measurement range equally divided by each industrial camera 6 is P, P=M / N;

[0017] The TOF distance measuring sensor 4 is vertically placed on the surface of the object to be measured, and is used to preliminarily determine the thickness range of the object to be measured;

[0018] The point laser light source 5 emits a laser light source of point light, which is vertically hit on the surface of the object to be measured to form a small light spot, and cooperates with the industrial camera 6 to perform distance measurement;

[0019] The two sets of measuring instruments 2 are arranged symmetrically, and the two are respectively projected from top to bottom and from bottom to top to obtain distance measurement values, which are combined with calibration information to convert into final thickness values.

[0020] The industrial cameras 6 are grouped into camera groups and arranged at the same tilt angle and the same horizontal spacing; the industrial cameras 6 are numbered C1, C2, ..., C from left to right. N The industrial cameras 6 in the camera group use area array cameras of the same specifications and models, and the lenses use telephoto lenses. The focal lengths of the lenses of the industrial cameras 6 increase in sequence to ensure that when shooting objects at different heights, they have similar imaging areas and clarity.

[0021] The industrial camera 6 meets the following object distance requirements, depth of field requirements and field of view requirements;

[0022] The object distance requirements are as follows: the object distance refers to the straight-line distance between the lens surface of the industrial camera 6 and the object to be measured; the distance between the lower surface of the measuring instrument 2 and the maximum measuring height is S, and the angle between the laser selected by the triangulation laser measurement method and the industrial camera 6 is θ, then the object distance u of each industrial camera 6 is described as:

[0023]

[0024] Where n represents the camera number;

[0025] The depth of field requirements are as follows: the depth of field refers to the range of distances before and after the object to be photographed that can be measured by obtaining a clear image when the industrial camera 6 photographs the target object; the depth of field is determined by the selection of the camera lens and the adjustment of the aperture, and the description formula of the depth of field d is:

[0026]

[0027] The field of view requirements are as follows: Considering the field of view of the industrial camera 6 in the height direction, the illumination area coverage P is satisfied, and at the same time, margins are left at the upper and lower ends in the height direction to avoid point light sources appearing at the edge position; the camera's field of view in the height direction is reflected in the camera lens's viewing angle in the height direction. The viewing angle in the height direction is set to α, and α needs to satisfy:

[0028]

[0029] Among them, F n is the horizontal distance between the industrial camera numbered n and the point laser light source.

[0030] The greater than symbol is used in the above formula to ensure that the camera field of view is larger than the detection range, to avoid the laser spot appearing as the edge of the camera image, which may cause loss of accuracy due to incomplete imaging of the light spot. The effect is shown in the attached figure. Figure 5 shown.

[0031] Additional explanation: The TOF laser ranging sensor will also generate a laser spot on the object being measured. The significance of using a point laser light source alone as the laser light source for the triangulation method is that: usually, the laser emitted by the TOF laser ranging sensor presents a large spot diameter on the steel plate being measured, and using this spot will affect the measurement accuracy.

[0032] A thickness measuring method of a high-precision online thickness measuring device, the specific steps are as follows:

[0033] Step 1. Before the steel plate arrives at the measurement area, start the high-precision online thickness measuring device and enter the standby state;

[0034] Step 2. After the roller drives the steel plate into the measuring area, the measurement begins;

[0035] The distance measured by the upper surface TOF distance measuring sensor 4 to the upper surface of the steel plate is M w According to the factory-calibrated measurement range of each industrial camera, obtain the measurement range including M w The camera number is defined as x;

[0036] The distance measured by the bottom surface TOF distance measuring sensor 4 to the bottom surface of the steel plate is M w2 According to the factory-calibrated measurement range of each industrial camera, obtain the measurement range including M w2 The camera number is defined as y;

[0037] Turn off the TOF ranging sensor 4 and perform the following image processing on the two groups of devices on the upper and lower surfaces respectively:

[0038] 2.1) The system server connects to the industrial camera numbered x and obtains a frame of image data;

[0039] 2.2) Performing median filtering on the image data to remove noise interference, and then performing binarization processing to obtain a light spot;

[0040] 2.3) Obtain the area where the light spot is located and obtain the minimum bounding box. According to the minimum bounding box, obtain the coordinates of the intersection of the diagonal lines of the bounding box rectangle i, j, which are the center coordinates of the laser point, where i is the horizontal coordinate and j is the vertical coordinate;

[0041] 2.4) Convert the two-dimensional coordinates into the actual height value M RU , in millimeters, the specific formula is:

[0042] M RU =M xs-(h xs -j)×(M xs -M xf ) / (h xs -h xf )

[0043] Among them, h xs 、h xf are the vertical starting pixel height and ending pixel height in the imaging of camera x, respectively. The interval between the two is the measurement range of camera x. xs With h xs Correspondingly, it expresses that at pixel height h xs The actual measured height is M xf With h xf Correspondingly, it expresses that at pixel height h xf , the actual measured height.

[0044] 2.5) The system server connects to the industrial camera numbered y and obtains a frame of image data;

[0045] 2.6) Perform median filtering on the image data to remove noise interference, and then perform binarization to obtain a light spot; (the method is the same as 2.2)

[0046] 2.7) Obtain the area where the light spot is located and obtain the minimum bounding box. According to the minimum bounding box, obtain the coordinates of the intersection of the diagonal lines of the bounding box rectangle i, j, which are the center coordinates of the laser point, where i is the horizontal coordinate and j is the vertical coordinate; (the method is the same as 2.3)

[0047] 2.8) Convert the two-dimensional coordinates into the actual height value M RD , in millimeters, the specific formula is:

[0048] M RD =M ys -(h ys -j)×(M ys -M yf ) / (h ys -h yf )

[0049] Among them, h ys 、h yf are the vertical starting pixel height and ending pixel height in the camera y imaging, and the interval between the two is the measurement range of the camera y. ys With h ys Correspondingly, it expresses that at pixel height h ys The actual measured height is M yf With h yf Correspondingly, it expresses that at pixel height j yf , the actual measured height.

[0050] Step 3. After the above steps, the formula for calculating the actual thickness T of the steel plate is as follows:

[0051] T=M t -(M RU +M RD );M t =M U -1+M d ;

[0052] M U M is the preset height from the upper detection instrument 2 to the upper surface of the steel plate; d The preset height from the lower detection instrument to the lower surface of the steel plate.

[0053] The parameter settings of the lower measuring instrument are the same as those of the upper surface. The lower measuring instrument is fixedly projected on the bottom of the steel plate, and the height change of the steel plate during the operation on the roller is small, so the lower measuring instrument usually contains fewer industrial cameras.

[0054] The high-precision online thickness measuring device is subjected to factory calibration and on-site system calibration before measurement;

[0055] The standards for factory calibration are as follows:

[0056] 1. The TOF distance sensor 4 and the point laser light source 5 are both perpendicular to the beam; the industrial cameras 6 in the camera group have the same spacing and the same tilt angle; the camera lens is calibrated to ensure clear imaging within the measurement range;

[0057] 2. Camera group parameter calibration;

[0058] The high-precision online thickness measuring device is fixed horizontally, and a precision displacement lifting platform is arranged directly below it. A test steel plate is fixed on the surface of the precision displacement lifting platform. The precision displacement lifting platform is lowered so that the distance between the detection instrument 2 and the steel plate surface is equal to the preset height M. U , start fine-tuning calibration from the camera with the largest camera group number. The specific steps are as follows:

[0059] 1) Turn on the point laser light source 5 and project it onto the surface of the test steel plate;

[0060] 2) Observe the image captured by the camera, and use the pixel height of the laser center point as the starting position. The current camera number is C n , then record the pixel height h ns The actual measured height M ns The mapping relationship h ns ->M ns , this mapping relationship describes C n The starting position of the camera measurement;

[0061] 3) Gradually raise the low-precision displacement lifting platform to a height of P, record the pixel height position of the center point of the laser light spot in the camera image, and record the mapping relationship h at this time nf ->M nf , this mapping relationship describes C n The end position of the camera measurement;

[0062] 4) After steps 1) to 3), determine the camera C n The measurement range and the mapping relationship between pixels and actual measurement values; continue to increase the height of the lifting platform and obtain the industrial camera C n-1 , C n-2 The measurement mapping relationship is established until all industrial cameras are calibrated and the obtained mapping data is recorded in the measurement system for retrieval and selection during actual measurement.

[0063] The process of the on-site system calibration is as follows:

[0064] 1. Calibrate the upper and lower sets of detection instruments 2 perpendicular to the z-axis;

[0065] 2. Take a calibration plate with a standard thickness of 1 mm as the basic calibration plate, and place it horizontally on the front and rear rollers of the gap where the measuring device is located, so that the bottom of the basic calibration plate is close to the roller reference horizontal surface 3;

[0066] 3. Fine-tune the height of the upper beam so that the distance from the detection instrument 2 to the upper surface of the calibration plate is equal to M. u -1, and adjust the height of the lower beam in the same way so that the distance from the lower detection instrument to the lower surface of the calibration plate is equal to M d , the M d The preset height of the lower surface detection instrument from the steel plate surface;

[0067] 4. Calibrate the TOF ranging sensor to match the M u 、M d The error value is within the required range; the calibration is now completed.

[0068] The measurement principle of the present invention is as follows: when the steel plate to be measured passes through the detection area, the TOF laser ranging sensor is first used for preliminary measurement and positioning to roughly determine the thickness value of the steel plate to be measured. Then, based on the measured thickness value, an industrial camera whose measurement range covers the thickness value is selected for shooting, and a point light source is used to perform precise measurement in a small range, thereby achieving the demand for high-precision measurement of the steel plate thickness.

[0069] The beneficial effects of the present invention are as follows:

[0070] 1. Compared with the traditional single TOF rangefinder for thickness measurement, it has higher measurement accuracy;

[0071] 2. Compared with the traditional single triangulation distance meter for thickness measurement, it has a wider detection range;

[0072] 3. The measuring device does not need to be close to the steel plate, is insensitive to the vertical distance between the measured object, and can be customized, so it has good applicability, especially when measuring high-temperature steel plates and steel plates with large warping amplitudes. The longer measuring distance can better protect the equipment and instruments, increase the service life of the device, and indirectly improve the reliability of the device;

[0073] 4. The whole device has a simple layout and low maintenance cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 This is a schematic diagram of a traditional steel plate thickness gauge;

[0075] Figure 2 Schematic diagram of the measurement device layout;

[0076] Figure 3 This is a schematic diagram of the internal structure of the measuring instrument;

[0077] Figure 4 Description of measurement range and main parameters;

[0078] Figure 5 This is a schematic diagram illustrating the effective area of ​​the camera's field of view;

[0079] Figure 6 A schematic diagram showing the relationship between the laser center position of a single camera image and the actual measured height;

[0080] Figure 7 Schematic diagram of the image processing process.

[0081] In the figure: 1-support frame; 2-measuring instrument; 3-roller reference horizontal plane; 4-TOF distance sensor; 5-point laser light source; 6-industrial camera. DETAILED DESCRIPTION

[0082] This measuring device is as follows Figure 2 As shown, the x-axis is the width direction of the steel plate, the y-axis is the roller running direction, which is also the production direction, and the z-axis is the height direction, where:

[0083] Support frame 1: It is a C-shaped measuring device support frame. The upper and lower beams are located at the upper and lower ends of the roller horizontal plane respectively, and are used to fix the measuring instrument 2. The columns and beams are made of steel structure to ensure sufficient rigidity and avoid deflection that affects the accuracy.

[0084] Measuring instrument 2: It consists of a set of TOF distance measuring sensors 4, a set of point laser light sources 5 and several industrial cameras 6. The internal structure is as shown in the attached figure. Figure 3As shown, when in use, a set of measuring instruments 2 is installed on the upper and lower beams of the support frame 1, and the installation positions are as shown in the attached Figure 2 As shown, two sets of measuring instruments 2 are respectively projected from top to bottom and from bottom to top, and the distance measurement values ​​obtained are combined with calibration information to be converted into final thickness values.

[0085] The internal components and structure of the measuring instrument 2 are described as follows:

[0086] TOF laser distance sensor 4: The TOF laser distance sensor is vertically projected onto the surface of the steel plate to be measured, which plays a role in preliminary measurement and positioning, and is used to determine the approximate thickness range of the steel plate being measured;

[0087] Point laser light source 5: A laser light source that can emit point light, which is vertically projected onto the surface of the steel plate to be measured to form a small light spot, and is used in conjunction with an industrial camera to achieve distance measurement using the triangulation method.

[0088] Industrial cameras 6: A group of industrial cameras are arranged at the same tilt angle and horizontal spacing, and are combined with a point laser light source 5 to perform high-precision measurement based on the triangulation laser method. Each industrial camera 6 is responsible for measuring a steel plate thickness interval. To facilitate the subsequent description of the measurement method, the cameras are numbered from left to right from small to large, and the numbers are C1, C2...C N The cameras in the camera group use area array cameras of the same specifications and models, and the lenses use telephoto lenses. The focal lengths of the camera lenses increase from left to right, ensuring similar imaging areas and clarity when shooting objects at different heights.

[0089] The image size of the industrial camera is set to w, h, where w is the image width and h is the image height.

[0090] The measuring instrument 2 is divided into an upper end and a lower end. The upper end is mounted on the upper beam of the supporting frame 1, and the lower end is mounted on the lower beam of the supporting frame 1. The number of industrial cameras 6 used depends on the requirements of the measuring range and accuracy.

[0091] Roller table reference horizontal plane 3: The upper surface of the roller table is set as the reference horizontal plane. During the operation of the roller table, the lower surface of the steel plate always fits the reference horizontal plane except for warping, buckling, etc. Therefore, the reference horizontal plane is defined as the reference position for thickness measurement.

[0092] The measuring instrument 2 is an integrated instrument as a whole, and the parameters of the internal components are calibrated when it is assembled at the factory.

[0093] In addition to the contents described in the layout diagram, this set of equipment also needs to have a measurement processing server to process the ranging signal of the TOF ranging sensor 4 and the image signal collected by the industrial camera 6, and finally calculate the measured value of the steel plate thickness and send it to the production control system in real time.

[0094] Example

[0095] Taking a certain implementation site as an example, the thickness range of the steel plate is 6mm-150mm, and the measurement accuracy is required to be ±0.1mm. After the steel plate is processed in the previous process, the plate shape is flat and has no warping. Therefore, the required height range for detection is slightly larger than the thickness range of the steel plate, and the measurement range of the detection device is 0mm-180mm. In addition, the TOF ranging sensor 4 used in the detection device has a ranging accuracy of ±2mm, a collection period of 0.1s, a spot diameter of the selected point laser <0.5mm, and a resolution of the industrial camera 6 of w=1080, h=1920, and the effective height is set to 1600, the starting point 160, and the end point 1760.

[0096] The upper measuring instrument 2 considers using 4 cameras to form a camera group, and each industrial camera is responsible for a measurement interval P of 180 / 4=45mm. Among them, industrial camera No. 4 is used to measure steel plates with a thickness range of 6mm to 45mm, industrial camera No. 3 is used to measure steel plates with a thickness range of 46mm to 90mm, and so on.

[0097] The lower measuring instrument 2 considers using two cameras to form a camera group. Taking into account the warping of the steel plate, the detection range starts from 30mm above the reference plane and ends at 60mm below the reference plane. The length of 0mm to 30mm above the reference plane and the length of 0mm to 60mm below the reference plane can be measured. This takes into account the situation where the lower surface of the steel plate is higher than the roller reference plane due to the warping of the steel plate, and also takes into account the situation where the lower surface of the steel plate is lower than the roller reference plane due to the steel plate buckle.

[0098] In addition, set the distance M from the upper detection instrument to the reference surface U =255mm, distance from lower detection instrument to reference surface M d =130mm.

[0099] Based on the above information, a lens that meets the requirements for object distance, depth of field and field of view is selected, and assembled and calibrated. In addition, the actual detection accuracy of this application example is: measurement interval / camera height direction field of view, which is approximately 45 / 1600=0.028mm, and the cumulative accuracy at the upper and lower ends is approximately 0.028+0.028=0.056mm, which is less than the required accuracy and meets the measurement requirements (in actual calibration, the camera field of view is affected by the installation accuracy and will fluctuate around 1600).

[0100] During the actual test, a steel plate with a thickness of 26.5 mm was placed in the test area for measurement:

[0101] 1. The TOF distance sensor 4 of the upper measuring instrument 2 measures the distance, and the distance value is 229mm. The current steel plate height is 255-229=33mm (with a 2mm error). According to the measurement method rules, this value is in the range of 0mm-45mm, which is the range of the camera numbered 4. The relevant parameters of the camera are: M ns =255mm,M nf =210mm,h ns =1745,h nf =162, after getting a frame of original image with laser spot, after processing, the center coordinate j of the light spot height direction is 687, and M is calculated according to the formula RU =255-(1745-687)*(255-210) / (1745-162)=224.924mm.

[0102] 2. The TOF ranging sensor 4 of the lower measuring instrument 2 measures the distance, and the distance value is 135mm. The distance between the lower surface of the steel plate and the reference plane is 135-130=5mm, which means that the lower surface of the steel plate at the current detection point is 5mm higher than the reference plane. This is a simple calculation. The lower detection instrument uses a camera with a number n of 2 for photo detection. The relevant parameters of the camera are: M ns =150mm,M nf =105mm,h ns =1758,h nf =160. After image processing, the light spot center coordinate height value j is 513. According to the company's calculation, M RD =130+30-(1758-817)*(150-105) / (1758-160)=133.501mm.

[0103] The final calculated thickness measurement value T is: 255+130-(224.924+124.940)=26.575mm. The measured thickness and the set thickness are less than the allowable error, and the detection is completed.

Claims

1. A high-precision online thickness measuring device, characterized in that: The high-precision online thickness measuring device comprises a supporting frame (1) and a measuring instrument (2); The support frame (1) is a C-shaped frame structure, comprising a column and two cross beams; the cross beams are respectively located on the upper and lower sides of the roller table reference horizontal plane (3) and are used to fix the measuring instrument (2); The measuring instrument (2) comprises a TOF distance measuring sensor (4), a point laser light source (5) and a plurality of industrial cameras (6); the industrial cameras (6) cover measurement work in different thickness ranges; the total measurement thickness range requirement is M, the number of industrial cameras (6) is N, and the measurement range equally divided by each industrial camera (6) is P, where P=M / N; The TOF distance measuring sensor (4) is vertically mounted on the surface of the object to be measured, and is used to preliminarily determine the thickness range of the object to be measured; The point laser light source (5) emits a laser light source of point light, which is vertically projected onto the surface of the object to be measured to form a small light spot, and cooperates with the industrial camera (6) to perform distance measurement; The two sets of measuring instruments (2) are arranged symmetrically, and the two are respectively projected from top to bottom and from bottom to top to obtain distance measurement values, which are combined with calibration information to convert into final thickness values.

2. The high-precision online thickness measuring device according to claim 1, characterized in that: The industrial cameras (6) are grouped into camera groups and arranged at the same tilt angle and the same horizontal spacing; the industrial cameras (6) are numbered C1, C2, ..., C from left to right. N The industrial cameras (6) in the camera group use area array cameras of the same specifications and models, and the lenses use telephoto lenses. The focal lengths of the lenses of the industrial cameras (6) increase in sequence to ensure that when shooting objects at different heights, they have similar imaging areas and clarity.

3. The high-precision online thickness measuring device according to claim 1 or 2, characterized in that: The industrial camera (6) meets the following requirements on object distance, depth of field and field of view; The object distance requirement is as follows: the object distance refers to the straight-line distance between the lens surface of the industrial camera (6) and the object to be measured; the distance between the lower surface of the measuring instrument (2) and the maximum measuring height is S, and the angle between the laser selected by the triangulation laser measurement method and the industrial camera (6) is θ, then the object distance u of each industrial camera (6) is described as: Where n represents the camera number; The depth of field requirement is as follows: the depth of field refers to the range of distances in front and behind the object measured by the industrial camera (6) to obtain a clear image when shooting the target object; the depth of field is determined by the selection of the camera lens and the adjustment of the aperture. The formula describing the depth of field d is: The field of view requirements are as follows: Considering the field of view of the industrial camera (6) in the height direction, the illumination area coverage P is satisfied, and at the same time, margins are left at the upper and lower ends in the height direction to avoid point light sources appearing at the edge position; the camera's field of view in the height direction is reflected in the camera lens's viewing angle in the height direction. The viewing angle in the height direction is set to α, and α must satisfy: Among them, F n is the horizontal distance between the industrial camera numbered n and the point laser light source.

4. A thickness measuring method according to any one of claims 1 to 3, characterized in that: Step 1. Before the steel plate arrives at the measurement area, start the high-precision online thickness measuring device and enter the standby state; Step 2. After the roller drives the steel plate into the measuring area, the measurement begins; The distance measured by the upper surface TOF distance measuring sensor (4) to the upper surface of the steel plate is M w According to the factory-calibrated measurement range of each industrial camera, obtain the measurement range including M w The camera number is defined as x; The distance measured by the bottom surface TOF distance measuring sensor (4) to the bottom surface of the steel plate is M w2 According to the factory-calibrated measurement range of each industrial camera, obtain the measurement range including M w2 The camera number is defined as y; Turn off the TOF ranging sensor (4) and perform the following image processing: 2.1) The system server connects to the industrial camera numbered x and obtains a frame of image data; 2.2) Performing median filtering on the image data to remove noise interference, and then performing binarization processing to obtain a light spot; 2.3) Obtain the area where the light spot is located and obtain the minimum bounding box. According to the minimum bounding box, obtain the coordinates of the intersection of the diagonal lines of the bounding box rectangle i, j, which are the center coordinates of the laser point, where i is the horizontal coordinate and j is the vertical coordinate; 2.4) Convert the two-dimensional coordinates into the actual height value M RU , in millimeters, the specific formula is: M RU =M xs -(h xs -j)×(M xs -M xf ) / (h xs -h xf ) Among them, h xs 、h xf are the vertical starting pixel height and ending pixel height in the imaging of camera x, respectively. The interval between the two is the measurement range of camera x. xs With h xs Correspondingly, it expresses that at pixel height h xs The actual measured height is M xf With h xf Correspondingly, it expresses that at pixel height h xf The actual measured height when 2.5) The system server connects to the industrial camera numbered y and obtains a frame of image data; 2.6) Performing median filtering on the image data to remove noise interference, and then performing binarization processing to obtain a light spot; 2.7) Obtain the area where the light spot is located and obtain the minimum bounding box. According to the minimum bounding box, obtain the coordinates of the intersection of the diagonal lines of the bounding box rectangle i, j, which are the center coordinates of the laser point, where i is the horizontal coordinate and j is the vertical coordinate; 2.8) Convert the two-dimensional coordinates into the actual height value M RD , in millimeters, the specific formula is: M RD =M ys -(h ys -j)×(M ys -M yf ) / (h ys -h yf ) Among them, h ys 、h yf are the vertical starting pixel height and ending pixel height in the camera y imaging, and the interval between the two is the measurement range of the camera y. ys With h ys Correspondingly, it expresses that at pixel height h ys The actual measured height is M yf With h yf Correspondingly, it expresses that at pixel height h yf The actual measured height; Step 3. After the above steps, the formula for calculating the actual thickness T of the steel plate is as follows: T=M t -(M RU +M RD );M t =M U -1+M d ; M U M is the preset height from the upper detection instrument (2) to the upper surface of the steel plate; d The preset height from the lower detection instrument to the lower surface of the steel plate.

5. The thickness measurement method according to claim 4, characterized in that: The high-precision online thickness measuring device is subjected to factory calibration and on-site system calibration before measurement; The standards for factory calibration are as follows:

1. The TOF distance measuring sensor (4) and the point laser light source (5) are both perpendicular to the beam; the industrial cameras (6) in the camera group have the same spacing and the same tilt angle; the camera lens is calibrated to ensure clear imaging within the measurement range; 2. Camera group parameter calibration; The high-precision online thickness measuring device is fixed horizontally, and a precision displacement lifting platform is arranged directly below it. A test steel plate is fixed on the surface of the precision displacement lifting platform. The precision displacement lifting platform is lowered so that the distance between the detection instrument (2) and the surface of the steel plate is equal to the preset height M. U , start fine-tuning calibration from the camera with the largest camera group number. The specific steps are as follows: 1) Turn on the point laser light source (5) and project it onto the surface of the test steel plate; 2) Observe the image captured by the camera, and use the pixel height of the laser center point as the starting position. The current camera number is C n , then record the pixel height h ns The actual measured height M ns The mapping relationship h ns ->M ns , this mapping relationship describes C n The starting position of the camera measurement; 3) Gradually raise the low-precision displacement lifting platform to a height of P, record the pixel height position of the center point of the laser light spot in the camera image, and record the mapping relationship h at this time nf ->M nf , this mapping relationship describes C n The end position of the camera measurement; 4) After steps 1) to 3), determine the camera C n The measurement range and the mapping relationship between pixels and actual measurement values; continue to increase the height of the lifting platform and obtain the industrial camera C n-1 , C n-2 The measurement mapping relationship is established until all industrial cameras are calibrated and the obtained mapping data is recorded in the measurement system for retrieval and selection during actual measurement.

6. The thickness measurement method according to claim 5, characterized in that: The process of the on-site system calibration is as follows:

1. Calibrate the upper and lower sets of detection instruments (2) perpendicular to the z-axis; 2. Take a calibration plate with a standard thickness of 1 mm as the basic calibration plate, and place it horizontally on the front and rear rollers of the gap where the measuring device is located, so that the bottom of the basic calibration plate is close to the reference horizontal surface of the roller (3); 3. Fine-tune the height of the upper beam so that the distance from the measuring instrument (2) to the upper surface of the calibration plate is equal to M. u -1, and adjust the height of the lower beam in the same way so that the distance from the lower detection instrument to the lower surface of the calibration plate is equal to M d , the M d The preset height of the lower surface detection instrument from the steel plate surface; 4. Calibrate the TOF ranging sensor to match the M u 、M d The error value is within the required range; the calibration is now completed.

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