CN107462301A - Liquid level monitoring method - Google Patents

Abstract

A liquid level monitoring method is applied to a liquid level monitoring system, and the liquid level monitoring system comprises a light-emitting module, a data acquisition module and a data processing module. The light emitting module projects a planar laser beam to a wall surface and the liquid level of the liquid, and a plurality of light line segments sharing an intersection point are formed at the junction of the wall surface and the liquid level. The data acquisition module shoots each light line segment to generate an original image. The data processing module strengthens and monitors the original image and obtains the image coordinates of the common intersection point of the light ray segments. And then, converting the image coordinate into an actual space coordinate, wherein the space coordinate is the liquid level position.

Description

Liquid level monitoring method

technical field

The present invention relates to a liquid level monitoring method, in particular to a method for projecting a planar laser beam onto a wall and a liquid surface, at least three light segments that form a common intersection point at the junction of the wall and the liquid surface, and image The processing method obtains the liquid level monitoring method of the spatial position of the common intersection point.

Background technique

China's Taiwan is located in the main path of typhoons in the northwest Pacific region, which is a high disaster risk area and is extremely vulnerable to natural disasters. In view of this, urban areas are likely to be flooded due to a large amount of rainwater that cannot be removed in a short period of time or the area cannot be drained in time, which seriously threatens the safety of people's lives and property. Accordingly, the liquid level monitoring and early warning of the river water level has always been the primary goal of disaster prevention; and in order to achieve the above goals, it is preferable to adopt a liquid level monitoring method to monitor the position of the liquid level. In addition, the liquid level monitoring method can also be widely used in various other fields, such as related fields such as chemistry or medicine. For example, in experiments related to chemistry, the measurement of various liquid chemical raw materials involves the configuration of different concentrations of various chemical raw materials, so the measurement accuracy of the dosage is very important. At the same time, in the field of medicine, for the monitoring of the dosage of the medicament used to treat patients, for example, if the medicament in the drip bottle is lower than the critical value when administering an infusion, it is necessary to remind the medical staff to replenish the medicament or stop administering the infusion.

The above-mentioned liquid level monitoring method can be an existing liquid level measurement method, which is to measure the liquid level position of the liquid by taking an image of the surface of the liquid, and its embodiment can be referred to as "Taiwan No. 201024687" Laser optical image water level measurement device and its method" patent application. In the method of the above-mentioned patent application, the light emitted by two laser light sources is used to form two laser spots on the surface of a water body. Then, a water body image including the two laser spots is captured and obtained by an image capture device, and the water body image is sent to the image processing device for analysis. The analysis method of the image processing device uses the correction regression curve to calculate the distance between the two laser light spots, thereby obtaining the water level height of the water body.

However, the two laser light spots need to be generated by the two laser light sources, and subsequent calculations are performed to obtain the water level of the water body. In view of this, in order to simplify the hardware requirements of the above-mentioned liquid level measurement method, the present invention provides a liquid level monitoring method, which only needs to project a planar laser beam onto a wall surface and a liquid surface, and the wall surface and the liquid surface At least three ray segments of a common intersection are formed at the junction, and the position of the common intersection is analyzed to accurately measure and obtain the position of the liquid surface.

Contents of the invention

The object of the present invention is to provide a liquid level monitoring method, a planar laser beam is projected onto a wall surface and a liquid surface by a light-emitting module, at least three ray segments of a common intersection are formed at the junction of the wall surface and the liquid surface, And analyzing the position of the common intersection point to accurately measure and obtain the position of the liquid level.

A liquid level monitoring method is applied to a liquid level monitoring system to monitor the liquid level position of a liquid in a liquid storage device. The liquid level monitoring system includes a data processing module, and the method includes: using the data processing module to read input an original image; use the data processing module to monitor at least three ray segments forming a common intersection in the original image; use the data processing module to calculate the image coordinates of the common intersection; and use the data processing module to convert the image coordinates into A spatial coordinate, which is the liquid level position of the liquid.

Wherein, the liquid holding device has a wall, and the wall is in contact with the liquid, so that the liquid surface of the liquid meets the wall to form an intersection line, and the liquid level monitoring system additionally includes a light emitting module and a data acquisition module , the data processing module is coupled to the light-emitting module and the data acquisition module. Before the data processing module reads the original image, the method uses the light-emitting module to project a planar laser beam toward the intersection line, so as to The wall surface and the liquid surface of the intersection line form the at least three ray segments, and the common intersection point is located on the intersection line, and the data acquisition module is used to shoot toward the at least three ray segments and generate the original image.

Wherein, the planar laser beam forms a first light segment and a second light segment on the wall surface and the liquid surface respectively, and the second light segment forms a third light segment on the wall surface, and the third light segment forms a third light segment on the wall surface. The liquid surface forms a fourth light segment, and the at least three light segments include at least three light segments among the first light segment, the second light segment, the third light segment and the fourth light segment.

Wherein, the method for monitoring the at least three ray segments includes performing edge monitoring and morphological processing on the original image to generate a binary image, and performing line segment monitoring on the binary image.

Wherein, the morphological processing performs morphological filling and skeletonization on the original image.

Wherein, when the at least three ray segments include at least one curved line segment, the data processing module performs straight line monitoring and curve monitoring on the original image.

Wherein, when the wall is a curved wall, the at least three light segments include at least one curved line segment, and the data processing module performs straight line monitoring and curve monitoring on the original image.

Wherein, the method used by the data processing module to calculate the image coordinates of the co-intersection point is the least square method.

Wherein, the method used by the data processing module to convert the image coordinates into the space coordinates is a direct linear conversion method.

Description of drawings

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Figure 1: A schematic diagram of the system architecture of an embodiment of the liquid level monitoring method of the present invention;

Fig. 2: the hardware operation flowchart of the liquid level monitoring method embodiment of the present invention;

Fig. 3: the software operation flowchart of the liquid level monitoring method embodiment of the present invention;

Figure 4: Schematic diagram of light segment monitoring in an embodiment of the liquid level monitoring method of the present invention.

Explanation of reference signs

1 Data processing module 2 Light emitting module

3 Data acquisition module 4 Database module

S1 Pre-processing program S11 Parameter calibration steps

S12 Image reading steps S13 Grayscale processing steps

S2 Feature Enhancer

S21 Edge detection step S22 Morphological processing step

S3 Image Analysis Program S31 Line Segment Monitoring Steps

S32 Common point calculation step S33 Liquid level estimation step

L liquid S liquid level

W Wall A Original image

T Flat laser beam U First ray segment

Y second ray segment Z third ray segment

X Fourth ray segment G Image gradient value

E image boundary value ω threshold.

detailed description

In order to make the above-mentioned and other objects, features and advantages of the present invention more comprehensible, the following is based on the preferred embodiments of the present invention and is described in detail as follows in conjunction with the accompanying drawings:

The "Coupled Connection" mentioned in the present invention refers to two electronic devices communicating with each other through wired or wireless technology, but it is not limited thereto and can be understood by those of ordinary skill in the technical field of the present invention.

"Pixels" as mentioned throughout the present invention refers to the smallest unit of an image, which is used to represent the resolution of the image. For example, if the resolution of the image is 1024×768, it represents the resolution of the image. There are 1024×768 pixels in total, which can be understood by those of ordinary skill in the technical field of the present invention.

The "Color Level" mentioned in the present invention refers to the intensity of the color component or brightness displayed by the pixel, for example: the red (R), green (G) and blue (B) components of the color image The color scales range from 0 to 255; alternatively, the color scale range of the Luminance of the grayscale image can be from 0 to 255, which can be understood by those skilled in the art of the present invention.

Please refer to FIG. 1 , which is a schematic diagram of the system architecture of an embodiment of the liquid level monitoring method of the present invention, including: a data processing module 1 , a light emitting module 2 and a data acquisition module 3 . Wherein, the light emitting module 2 and the data acquisition module 3 are coupled to the data processing module 1 . The system can be applied to monitor the liquid level S position of the liquid L in a liquid holding device (for example: a water channel or a container). Wherein, the liquid holding device includes two side walls, a bottom wall and an accommodating space, the accommodating space is formed by the two side walls and the bottom wall, and the accommodating space is used for containing the liquid L. Specifically, one of the two side walls has a wall W facing the accommodating space, the wall W can be a planar wall or a curved wall, and the wall W has opposite top and bottom ends. In addition, when the liquid container contains the liquid L, the liquid L contacts the wall W, and the liquid surface S contacts the wall W to form an intersection line. In addition, the data processing module 1 can preferably be coupled to a database module 4, such as: MySql, Oracle and other databases, the database module 4 can be used to store the original image A taken by the data acquisition module 3, and can also be processed by the data Module 1 receives an image as the original image A, and uses it for subsequent image processing and analysis.

Please refer to FIG. 2 , which is a hardware operation flowchart of an embodiment of the liquid level monitoring method of the present invention. Wherein, the light emitting module 2 projects a planar laser beam T toward the intersection line, and the planar laser beam T preferably covers the connection direction from the bottom end of the light emitting module 2 and the wall W to the light emitting module 2 and the wall W The range formed by the online directions at the top of the . Also, the planar laser beam T is not parallel to the intersection line. Thereby, when the liquid L is contained in the liquid holding device, the planar laser beam T can form at least three light segments on the wall surface W and the liquid surface S adjacent to the intersection line, and the at least three light segments are in the Intersecting lines form a common intersection point. In this embodiment, the planar laser beam T forms a first light segment U and a second light segment Y on the wall W and the liquid surface S respectively, and the second light segment Y forms a third light segment Y on the wall W. A ray segment Z, the third ray segment Z forms a fourth ray segment X on the liquid surface S, and the at least three ray segments include the first ray segment U, the second ray segment Y, the third ray segment Z and There are at least three ray segments in the fourth ray segment X. In addition, the wall W takes the wall of a channel side wall as an example for subsequent description. Meanwhile, the light emitting module 2 can be a laser fog lamp (Laser Emitter with Prism Lens), or a laser pointer can be used to project a beam of light onto a prism, thereby forming the plane laser beam T. However, the embodiment of the light-emitting module 2 and the container to which the monitoring method is applied are not limited to the above forms.

Please refer to FIG. 2 again, the data acquisition module 3 (for example: surveillance camera, network camera or infrared camera, etc.) can be coupled to the data processing module 1 (for example: computer host, file server or cloud server, etc.) as a system Execution architecture. In this embodiment, the data acquisition module 3 can be arranged beside the light emitting module 2, and obtain an original image A (Original Image) including the at least three light segments, for example: single (Single) or continuous (Continued) images, etc., the original image A can be a color or grayscale image. The data processing module 1 can receive the original image A from the data acquisition module 3, and execute the software operation process disclosed in the embodiment of the liquid level monitoring method of the present invention to measure the position of the liquid level, but not limit. In detail, the above-mentioned liquid level position is the water level of the liquid L. In addition, the original image A takes a color image as an example for subsequent description, but it is not limited thereto, and so on, it can be applied to the measurement of the liquid level position of black and white or continuous images, which is common in the technical field of the present invention. Those skilled in the art can understand, and need not go into details here.

Please refer to FIG. 3 , which is a flowchart of the software operation of the embodiment of the liquid level monitoring method of the present invention, which may include a pre-processing program S1, a feature enhancement program S2 and an image analysis program S3, respectively described as follows.

The pre-processing procedure S1 may include a parameter calibration step S11, an image reading step S12 and a grayscale processing step S13. Wherein, in the parameter calibration step S11 , at least four external control points can be set by the data processing module 1 to obtain the external parameters of the data acquisition module 3 . The data processing module 1 calculates the internal parameters of the data capturing module 3 based on the external parameters of the data capturing module 3 , a plane calibration plate and a calibration formula. In this embodiment, the data capture module 3 is a video camera. The internal parameters of the camera can be used to correct the radiation distortion (Radial Distortion) of the lens, which can be understood by those of ordinary skill in the technical field of the present invention, and will not be repeated here. Wherein, the correction formula may refer to "a correction method for solving image distortion provided by Holland et al. (1997)". In addition, the calculation method of the internal parameters of the data acquisition module 3 can be understood by those of ordinary skill in the technical field of the present invention, and will not be repeated here.

In the image reading step S12, the data processing module 1 can read the original image A from the data capture module 3, but not limited thereto. Wherein, the original image A may include images of the wall W, the liquid L and the at least three light segments.

In the grayscale processing step S13, the data processing module 1 can perform grayscale processing on the original image A. The main principle is to convert the original image A The hue of the average is converted to lightness on a scale ranging from 0 to 255.

However, the parameter calibration step S11 and the gray scale processing step S13 can be selectively executed, for example: when the internal and external parameters of the data acquisition module 3 do not need to be calibrated, the parameter calibration step S11 can be omitted; meanwhile, The color scale of the pixels of the original image A ranges from 0 to 255, so the gray scale processing step S13 can be omitted, which can be understood by those skilled in the art of the present invention, and no limitation is imposed here.

The main purpose of the feature enhancement procedure S2 is to enhance the features of the light segments included in the original image A, which may include an edge detection step S21 and a morphological processing step S22. Wherein, in the edge monitoring step S21, the data processing module 1 can monitor the edge features of the original image A, and the monitoring method can be a gradient operator edge search method, for example: Canny Edge Detection or Sobel Edge detection (Sobel Edge Detection), etc. In this embodiment, Kenny edge detection is used as an example for follow-up description, but it is not limited thereto. The main principle is to calculate the image gradient (Gradient) value G of each pixel in the original image A, and based on the image The gradient value G calculates the image boundary value E of each pixel. In detail, the original image A can be a binary image in image processing after the edge detection step S21 is performed, but it is not limited thereto. Wherein, the image boundary value E is 1 or 0, respectively representing that a pixel is a boundary or not a boundary. The calculation formulas of the image gradient value G and the image boundary value E are shown in the following formulas (1)-(3):

Among them, f(x, y) is the gray scale value when the pixel of the original image A is (x, y), and 0≤x<M and 0≤y<N; G _x represents the horizontal direction of the original image A The gradient value of ; G _y represents the gradient value of the original image A in the vertical direction; ω is a threshold. If the image gradient value G of the pixel (x, y) of the original pixel A is greater than the threshold ω, then set the image boundary value E(x, y) of the pixel (x, y) to 1; if the original pixel When the image gradient value G of the pixel (x, y) of A is not greater than the threshold ω, the image boundary value E(x, y) of the pixel (x, y) is set to be 0. In this embodiment, the data processing module 1 monitors the edge features of the original image A through the gradient operator edge search method, so as to obtain the wall surface, the liquid surface, and the at least three lines in the original image A whose boundary value is 1. segment of light.

In the morphological processing step S22, the data processing module 1 can use the morphological image processing method of filling (Fill) and skeletonization (Skeletonizing) on the original image A, so that the characteristics of the at least three light segments can be generated in the original image A . After performing the morphological processing step S22, the original image A can be a binary image in image processing, but not limited thereto. For example, after the data processing module 1 uses the fill-in morphological image processing method on the original image A, it will fill the edge features of at least three light segments included in the original image A. When the at least three ray segments are all straight lines, the at least three ray segments are all mxn quadrilaterals, where m represents the pixel value of the width of the quadrilateral, and m≧1; n represents the pixel value of the length of the quadrilateral, and n≧ 1; when the at least three ray segments include a curve, the pixel value of the width of the curve is m, and m≧1. However, when the pixel value of the width or length of the at least three ray segments is greater than 1, it may cause misjudgment in the subsequent image processing step, so the data processing module 1 uses skeletonized morphological image processing on the original image A method, converting the pixel value of one of the width or length of the at least three ray segments into 1 pixel. Thereby, the accuracy and image processing efficiency of subsequent image processing steps are improved.

Please also refer to FIG. 4 , the image analysis program S3 may include a line segment monitoring step S31 , a common point calculation step S32 and a liquid level estimation step S33 . Wherein, in the line segment monitoring step S31, the data processing module 1 monitors at least three light segments included in the original image A. In this embodiment, when the wall W is the planar wall, the Hough Transform method can be used to monitor at least three ray segments included in the original image A with reference to "Hough (1962)", the main principle of which is It is to convert the x and y coordinates of each point of each line segment in the original image A into ρ (rho) and θ (theta) polar coordinates. The conversion formula is shown in the following formulas (4) to (5):

According to the Hough transformation method, the line segments in the same direction in the original image A have the characteristic of intersecting at the same point on the ρ and θ polar coordinate diagrams. Therefore, the point with the largest amount of intersection can be taken out, and ρ and θ are close to the best The line segment of the value is the monitored ray segment.

However, when the wall W is the curved wall, the at least three ray segments may include at least one curved line segment, therefore, the data processing module 1 may perform straight line monitoring and curve monitoring on the original image A.

In the common point calculation step S32, the data processing module 1 can obtain the line segment equations of the at least three ray segments. In this embodiment, the data processing module 1 can arbitrarily select the minimum required number of pixel coordinate points that make up the at least three ray segments in the original image A (for example: at least two pixel coordinate points are required to generate a straight line equation or at least Three pixel coordinate points are required to generate a curve equation) to generate the line segment equation of the at least three ray segments. In addition, when the at least three ray segments are all straight line segments, the data processing module 1 can represent the respective line segment equations of the at least three ray segments in a vector representation. Subsequently, a matrix equation can be generated by the data processing module 1 according to the above-mentioned line segment equation, and the matrix equation can be calculated by the data processing module 1 through the joint method or the least squares method (Generalized Least Squares) to obtain the at least three ray segments The image coordinates of the co-intersection points of . In this embodiment, the data processing module 1 uses the least square method to operate the line segment equation, but it is not limited thereto, and the operation method of the least square method can be understood by those of ordinary skill in the relevant technical fields of the present invention , which will not be repeated here.

For example, when the wall is the planar wall, the data processing module 1 can detect two straight line segments L1, L2 in the original image A. Wherein, the image coordinates of any two points of the straight line segment L1 are respectively (248,216), (276,538); the image coordinates of any two points of the straight line segment L2 are respectively (260,387), (523,825). The vector expression of the straight line segment is shown in the following formula (6):

a _i +tn _i ,-∝＜t＜∝ (6)

Among them, a _i is the matrix expression of the pixel coordinates of the i-th straight line segment, and n _i is the unit vector of the i-th straight line segment, then the respective unit vectors of the two straight line segments L1 and L2 are [0.0866 0.9962] ^T and [0.5148 0.8573] ^T . Subsequently, the data processing module 1 calculates by the least square method to obtain the image coordinates of the co-intersection point of the two straight line segments L1, L2, wherein the calculation method of the least square method is shown in the following formulas (7)-(9) :

p = R ^-1 q (7)

Wherein, p is the coordinates of the co-intersection point, j (j=1,2,...,J) is the jth straight line segment, I is the unit matrix, and nj is the unit vector of the _jth straight line segment, is the transition matrix of the unit vector of the jth straight line segment, and a _j is the vector expression of the jth straight line segment. And obtain the image coordinates of the co-intersection point as (263,392).

In the liquid level estimating step S33 , the data processing module 1 converts the image coordinates into spatial coordinates of the junction between the wall and the liquid level, thereby estimating the position of the liquid level. In this embodiment, the conversion of the space coordinates preferably can adopt the direct linear transformation method (Direct Linear Transformation), and its formula is shown in the following formula (10):

Among them, (u, v) are the image coordinates of the common intersection point, (X, Y, Z) are the spatial coordinates of the junction of the wall and the liquid surface, L _i (i=1,2,...,11) is the external parameter of the data acquisition module 3 . Since the data capture module 3 photographs the wall W of the side wall of the channel as an example, it is assumed that the distance between the data capture module 3 and the channel prevents the data capture module 3 from considering the influence of the depth of field. Therefore, the data processing module 1 can set the Y-axis of the spatial coordinates to be zero, so as to reduce the time required for the calculation of the liquid level estimation step S33 and improve the "image processing efficiency". Therefore, the formula of the direct linear conversion method can be modified as shown in the following formula (11):

Among them, (u, v) are the image coordinates of the common intersection point, (X, Y, Z) are the spatial coordinates of the junction of the wall and the liquid surface, L _i (i=1,3,4,5,7,8 ,9,11) are the external parameters of the data acquisition module 3 .

To sum up, the liquid level monitoring method of the present invention sets the four external control points for the data processing module 1 in the image pre-processing procedure S1 to obtain the external parameters of the data acquisition module 3 . The data processing module 1 uses the external parameters, the plane calibration plate and the calibration formula to generate the internal parameters of the data acquisition module 3 . Subsequently, the data processing module 1 reads in the original image A from the data capture module 3, and performs image processing on the original image A by executing the feature enhancement program S2. Furthermore, the data processing module 1 executes the image analysis program S3 to monitor the characteristics of the at least three ray segments included in the original image A, and calculates the image coordinates of the co-intersection points of the at least three ray segments, so as to estimate the relationship between the wall and the The spatial coordinates of the liquid surface junction, and obtain the liquid surface position. Accordingly, the liquid level monitoring and measuring method of the present invention can achieve the purpose of accurately measuring the liquid level position.

Claims (9)

1. A liquid level monitoring method is characterized in that, being applied to a liquid level monitoring system, to monitor the liquid level position of the liquid in a liquid holding device, the liquid level monitoring system comprises a data processing module, the method comprising: Read in an original image with the data processing module; Using the data processing module to monitor at least three ray segments forming a common intersection point in the original image; Using the data processing module to calculate the image coordinates of the common intersection point; and The image coordinates are converted into a space coordinate by the data processing module, and the space coordinate is the liquid surface position of the liquid. 2. The liquid level monitoring method according to claim 1, wherein the liquid holding device has a wall, the wall is in contact with the liquid, the liquid surface of the liquid meets the wall to form an intersection line, the The liquid level monitoring system additionally includes a light emitting module and a data acquisition module, the data processing module is coupled to the light emitting module and the data acquisition module, the method uses the light emitting module before the data processing module reads in the original image Projecting a planar laser beam toward the intersection line to form the at least three light segments on the wall and liquid surface adjacent to the intersection line, and the common intersection point is located on the intersection line, and the data acquisition module is directed towards the at least three Segments of light are captured to produce this raw image. 3. The liquid level monitoring method according to claim 2, wherein the planar laser beam forms a first light segment and a second light segment on the wall surface and the liquid surface respectively, and the second light segment is at the The wall surface forms a third light segment, and the third light segment forms a fourth light segment on the liquid surface, and the at least three light segments include the first light segment, the second light segment, the third light segment and the At least three ray segments in the fourth ray segment. 4. The liquid level monitoring method according to claim 2, wherein when the wall is a curved wall, the at least three light segments include at least one curved line segment, and the data processing module performs linear monitoring and Curve monitoring. 5 . The liquid level monitoring method according to claim 1 , wherein when the at least three light segments include at least one curved line segment, the data processing module performs straight line monitoring and curve monitoring on the original image. 6. The liquid level monitoring method as claimed in claim 1, characterized in that, the monitoring method of the at least three ray segments performs edge monitoring and morphological processing on the original image to generate a binary image, and the binary image The image performs line segment detection. 7. The liquid level monitoring method according to claim 6, wherein the morphological processing performs morphological filling and skeletonization on the original image. 8 . The liquid level monitoring method according to claim 1 , wherein the data processing module calculates the image coordinates of the common intersection point using a least square method. 9 . The liquid level monitoring method according to claim 1 , wherein the data processing module converts the image coordinates into the space coordinates by a direct linear conversion method. 10 .