A method for measuring vertical coordinates based on structured light images

Abstract

The present invention relates to the technical field of structural deformation monitoring, and specifically to a vertical coordinate measurement method based on structured light images, which is composed of a structured light image acquisition module, an image processing and coordinate analysis method, wherein the structured light image acquisition module includes a digital camera, a line laser, a suspension line and a background plate, wherein the digital camera and the line laser are installed on a bracket together, and the suspension line is located between the digital camera and the background plate, and the image processing and coordinate analysis method includes the following steps: calibrating the camera, determining the camera imaging ratio k, and the camera vertical field angle a, determining the object distance d, the object distance d is the vertical distance from the camera focal plane to the device background plate, powering the digital camera and the line laser, and the line laser emits a horizontal laser line to the device background plate. By using a monocular camera in combination with a line laser generator, real-time measurement of the lateral displacement of the two axial directions of the horizontal plane of the suspension line is achieved, with high precision, low cost, easy deployment, and anti-interference.

Description

Technical Field

[0001] The present invention relates to the technical field of structural deformation monitoring, and in particular to a vertical line coordinate measurement method based on structured light images. Background Art

[0002] At present, the monitoring of horizontal lateral displacement of engineering structures at home and abroad generally adopts the vertical coordinate method. The devices for measuring the horizontal lateral displacement of engineering structures by the vertical coordinate method mainly include capacitive and CCD photoelectric vertical coordinate meters, which have the following shortcomings:

[0003] 1. The CCD photoelectric vertical coordinate measuring machine has high requirements on the optical environment of the object being measured. Dust, mist and light will affect the measurement accuracy. In addition, the sensor is always in working state after being powered on, which seriously damages the service life of the photoelectric sensor.

[0004] Second, capacitive sensors are mostly differential measurements, which require high instrument installation accuracy; and shielded cables produce parasitic capacitance, making it difficult to guarantee the durability of capacitive sensing components.

[0005] 3. The sight can only be read manually, and the moving parts of the traditional stepping coordinate measuring machine have the problem of accumulated errors.

[0006] In summary, the existing vertical coordinate method has low measurement accuracy when measuring the horizontal lateral displacement of engineering structures, and the equipment is difficult to deploy during the measurement process, resulting in high costs and difficulty in large-scale promotion and use. Summary of the invention

[0007] In view of this, the purpose of the present invention is to propose a vertical coordinate measurement method based on structured light images to solve the problems that the existing vertical coordinate method has low measurement accuracy when measuring the horizontal lateral displacement of engineering structures and the equipment is difficult to deploy during the measurement process.

[0008] Based on the above purpose, the present invention provides a vertical line coordinate measurement method based on structured light image, which is composed of a structured light image acquisition module, an image processing and coordinate analysis method;

[0009] The structured light image acquisition module includes a digital camera, a line laser, a hanging line and a background plate, wherein the digital camera and the line laser are installed on a bracket, and the hanging line is located between the digital camera and the background plate;

[0010] The image processing and coordinate analysis method comprises the following steps:

[0011] S1. Calibrate the camera to determine the camera imaging ratio k and the camera vertical field of view angle a;

[0012] S2. Determine the object distance d, which is the vertical distance from the camera focal plane to the device background plate;

[0013] S3, powering the digital camera and the line laser, the line laser emitting a horizontal laser line onto the background plate;

[0014] S4, a digital camera captures a target image, and the target image includes a laser line, a background plate and a hanging line;

[0015] S5, identifying and extracting the hanging line image in the target image, and determining the horizontal pixel position X0 of the center line of the hanging line;

[0016] S6, based on S3, detecting and identifying the laser spot on the suspension line, and determining the pixel position Y1 of the spot in the vertical direction;

[0017] S7, identifying and extracting the horizontal laser line in the target image, and determining the vertical pixel position Y0 of the center line of the laser line;

[0018] S8, based on S5, detecting and identifying the breakpoint position of the horizontal laser line, the breakpoint is caused by the suspension line blocking the laser line, causing the background plate laser line to be disconnected, and determining the horizontal pixel position X1 of the disconnection position;

[0019] S9. Calculate the height offset and horizontal offset first:

[0020] S10, calculating the vertical coordinates according to the offset.

[0021] Preferably, the structured light image acquisition module further includes a timer and a power supply, and the power supply and the timer are used to power the digital camera and the line laser.

[0022] Preferably, the digital camera can be configured to capture structured light images in real time or at a fixed time.

[0023] Preferably, the line laser emits a horizontal laser line to the background plate, the length of the laser line can be adjusted by a laser lens, and the length of the horizontal laser line on the background plate exceeds the measuring range of the equipment by 10CM.

[0024] Preferably, the timer is set to three modes: normally open, normally closed, and periodically open to ensure periodic image acquisition.

[0025] Preferably, in step S9, the height offset h=k*(Y1-Y0), and the horizontal offset c=k*(X1-X0).

[0026] Preferably, in step S10, the coordinate calculation formula of the vertical line is as follows:

[0027] x = dh / tg(a / 2))

[0028] y=c*x / d=cc*hd*tg(a / 2).

[0029] The beneficial effects of the present invention are as follows: a line laser generator is used to emit a horizontal laser line to illuminate the vertical line, a camera is used to obtain a horizontal laser line image with vertical line position information, and then image analysis technology is used to detect and extract the laser line profile and the vertical line profile position information, and the vertical line X-axis and Y-axis position information is obtained after calculation, so that a single camera can measure the two axial lateral displacements of the horizontal plane of the vertical line in real time, with high accuracy, low cost, easy deployment, and anti-interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 This is a schematic diagram of the structure of a structured light image acquisition module according to an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of imaging of the hanging line, laser line and background plate according to an embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the imaging of the background plate laser line and the suspension line spot in an embodiment of the present invention;

[0034] Figure 4 This is a schematic diagram of a suspension line shielding a laser line according to an embodiment of the present invention.

[0035] In the figure: 1. digital camera; 2. line laser; 3. suspension line; 4. background board; 5. timer; 6. power supply. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0037] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not represent any order, quantity or importance, but are only used to distinguish different components. "Including" or "comprising" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connecting" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0038] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, a vertical line coordinate measurement method based on structured light image is composed of a structured light image acquisition module, image processing and coordinate analysis method;

[0039] The structured light image acquisition module includes a digital camera 1, a line laser 2, a suspension line 3 and a background plate 4. The digital camera 1 and the line laser 2 are installed on a bracket, and the suspension line 3 is located between the digital camera 1 and the background plate 4.

[0040] The structured light image acquisition module further includes a timer 5 and a power supply 6 . The power supply 6 and the timer 5 are used to supply power to the digital camera 1 and the line laser 2 .

[0041] The digital camera 1 can be set to collect structured light images in real time or at a fixed time.

[0042] The line laser 2 emits a horizontal laser line to the background plate 4. The length of the laser line can be adjusted by the laser lens, and the length of the horizontal laser line on the background plate 4 exceeds the measuring range of the equipment by 10CM.

[0043] Timer 5 is set to three modes: normally open, normally closed, and periodically open to ensure periodic image acquisition.

[0044] The image processing and coordinate analysis method comprises the following steps:

[0045] S1. Calibrate the camera to determine the camera imaging ratio k and the camera vertical field of view angle a.

[0046] S2. Determine the object distance d, which is the vertical distance from the camera focal plane to the device background plate.

[0047] S3, power the digital camera and the line laser, and the line laser emits a horizontal laser line onto the background plate.

[0048] S4. The digital camera captures a target image, and the target image includes a laser line, a background plate, and a hanging line.

[0049] S5. Identify and extract the hanging line image in the target image, and determine the horizontal pixel position X0 of the center line of the hanging line.

[0050] S6. Based on S3, detect and identify the laser spot on the suspension line, and determine the pixel position Y1 of the spot in the vertical direction.

[0051] S7. Identify and extract the horizontal laser line in the target image, that is, the projection line of the laser line on the background plate, and determine the vertical pixel position Y0 of the center line of the laser line.

[0052] S8. Based on S5, detect and identify the breakpoint position of the horizontal laser line. The breakpoint is caused by the suspension line blocking the laser line, resulting in the disconnection of the background plate laser line. Determine the horizontal pixel position X1 of the disconnection position.

[0053] S9, first calculate the height offset and the horizontal offset.

[0054] In step S9, the height offset h=k*(Y1-Y0), and the horizontal offset c=k*(X1-X0).

[0055] The pixel coordinates in the picture can be viewed through the "Paint" software. Open the picture through the "Paint" software that comes with the computer. By moving the mouse, you can view the pixel coordinates of a certain point in the image in the lower left corner. You can also use programming languages ​​​​(such as Python, JavaScript, etc.) to achieve this function.

[0056] S10, calculating the vertical coordinates according to the offset.

[0057] In step S10, the coordinate calculation formula of the vertical line is as follows:

[0058] x = dh / tg(a / 2))

[0059] y=c*x / d=cc*hd*tg(a / 2).

[0060] Here, tg represents the tangent value in mathematical function.

[0061] In addition, after a cycle time has passed, the process returns to step S3 to recalculate new vertical coordinates x', y'.

[0062] The present invention uses a line laser generator to emit a horizontal laser line to illuminate the suspension line, and a camera is used to obtain a horizontal laser line image with vertical line position information. Then, image analysis technology is used to detect and extract the laser line profile and the vertical line profile position information, and the vertical line X-axis and Y-axis position information is obtained after calculation, thereby realizing high-precision measurement of two axes by a single camera.

[0063] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0064] The embodiments of the present invention are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring vertical coordinates based on structured light images, characterized in that: It consists of a structured light image acquisition module, image processing and coordinate analysis methods; The structured light image acquisition module comprises a digital camera (1), a line laser (2), a suspension line (3) and a background plate (4); the digital camera (1) and the line laser (2) are mounted on a bracket, and the suspension line (3) is located between the digital camera (1) and the background plate (4); The image processing and coordinate analysis method comprises the following steps: S1. Calibrate the camera to determine the camera imaging ratio k and the camera vertical field of view angle a; S2. Determine the object distance d, which is the vertical distance from the camera focal plane to the device background plate; S3, powering the digital camera and the line laser, the line laser emitting a horizontal laser line onto the background plate; S4, a digital camera captures a target image, and the target image includes a laser line, a background plate and a hanging line; S5, identifying and extracting the hanging line image in the target image, and determining the horizontal pixel position X0 of the center line of the hanging line; S6, based on S3, detecting and identifying the laser spot on the suspension line, and determining the pixel position Y1 of the spot in the vertical direction; S7, identifying and extracting the horizontal laser line in the target image, and determining the vertical pixel position Y0 of the center line of the laser line; S8, based on S5, detecting and identifying the breakpoint position of the horizontal laser line, the breakpoint is caused by the suspension line blocking the laser line, causing the background plate laser line to be disconnected, and determining the horizontal pixel position X1 of the disconnection position; S9, first calculate the height offset and the horizontal offset; S10, calculating the vertical coordinates according to the offset.

2. The method for measuring vertical coordinates based on structured light images according to claim 1, characterized in that: The structured light image acquisition module further comprises a timer (5) and a power supply (6), wherein the power supply (6) and the timer (5) are used to supply power to the digital camera (1) and the line laser (2).

3. The method for measuring vertical coordinates based on structured light images according to claim 2, characterized in that: The digital camera (1) can be configured to collect structured light images in real time or at a fixed time.

4. The method for measuring vertical coordinates based on structured light images according to claim 2, characterized in that: The line laser (2) emits a horizontal laser line to the background plate (4); the length of the laser line can be adjusted by a laser lens, and the length of the horizontal laser line on the background plate (4) exceeds the measuring range of the device by 10 cm.

5. The method for measuring vertical coordinates based on structured light images according to claim 2, characterized in that: The timer (5) is set to three modes: normally open, normally closed, and periodically open, so as to ensure periodic image acquisition.

6. The method for measuring vertical coordinates based on structured light images according to claim 1, characterized in that: In step S9, the height offset h=k*(Y1-Y0), and the horizontal offset c=k*(X1-X0).

7. The method for measuring vertical coordinates based on structured light images according to claim 6, characterized in that: In step S10, the coordinate calculation formula of the vertical line is as follows: x = dh / tg(a / 2)) y=c*x / d=cc*hd*tg(a / 2).

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