CN113124898B - Pipe level device position precision measuring method based on image processing - Google Patents
Pipe level device position precision measuring method based on image processing Download PDFInfo
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Abstract
The invention discloses a method for quickly measuring the position accuracy of a pipe level based on an image processing technology, which comprises the steps of capturing an original image of the pipe level by a camera, then performing image processing operation, filtering the image, performing threshold processing and performing expansion operation; then, searching inner side scale marks in the image, and cutting the whole image based on the searched scale mark pixel coordinate values to obtain a required bubble image; and then extracting the contour of the partitioned bubble image, further finding out pixel coordinate values of left and right end points of the outer contour of the bubble, calculating a pixel value of the offset of the bubble according to the pixel coordinate information of the left and right end points of the bubble and the pixel coordinate information of the scale mark, and finally calculating the position accuracy value of the tube level according to the pixel coordinate information of the left and right end points of the bubble and the pixel coordinate information of the scale mark. The method can be used for detecting products or components such as a level bar, a tube level assembly and the like which react the position precision through bubbles, and can also be used for detecting the horizontal precision, the vertical precision, the 45-degree position precision and the position precision of any angle of the products or the components.
Description
Technical Field
The invention belongs to the field of image processing, and particularly relates to a method for quickly measuring the position accuracy of a pipe level based on an image processing technology.
Background
The position precision measurement of the tube level is mainly carried out based on the offset of the air bubble, and whether a measured object is horizontal or not is judged by judging the offset of the air bubble relative to left and right scale marks in the tube level based on the principle of liquid level. The calibration of the prior level ruler mainly adopts manual operation and an operation mode of human eye aiming, and has the main problems of low efficiency and larger operation error. The chinese patent publication No. 108876860A discloses an image calibration method for measuring bubble offset of a tube level, which is improved on the conventional calibration method, realizes automatic calibration, converts image distance into an error value representing the actual position accuracy of bubbles, but directly extracts a contour of the whole binarized image, and then screens out a target contour by means of geometric information of the contour. The method has the problems of too many distinguishing objects and too many judging conditions, so that the bubble outline can be misjudged to a great extent, and the calculation result is wrong.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to overcome the defects in the prior art, and provides a tube level position accuracy measuring method based on image processing, which has better robustness and reliability and higher detection efficiency than the prior method.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
a tube level position precision measuring method based on image processing is implemented according to the following steps:
step 1: performing median filtering, threshold fixing and expansion processing on an original image captured by a camera, and searching a right row pixel coordinate P of a left inner side scale mark on the pipe level in a pixel traversal mode l1 And the left column pixel coordinate P of the right inner scale mark r1 And column pixel coordinate P of middle point of line width of left inner scale line CL And column pixel coordinate P of middle point of line width of right inner side scale mark CR ；
And 2, step: finding the line pixel coordinate value P of the top end of the cylindrical tube wall in the tube level t ；
And step 3: the right column pixel coordinate P based on the left inner scale mark detected in said step 1 l1 And the left column pixel coordinate P of the right inner scale mark r1 And the line pixel coordinate P of the top end of the cylindrical pipe wall detected in the step 2 t Performing image segmentation on the bubble image;
and 4, step 4: carrying out contour extraction operation on the segmented image obtained in the step 3 to obtain a contour with the longest contour curve perimeter, wherein the contour is the required bubble outer contour;
and 5: on the basis of acquiring the bubble outline in the step 4, calculating the column pixel coordinate values of the left end point and the right end point of the bubble in the image, and combining the column pixel coordinate values with the line width midpoint of the left inner scale mark detected in the step 1Pixel coordinate P CL And the column pixel coordinate P of the middle point of the line width of the right inner scale mark CR And calculating the pixel value of the air bubble offset, and then calculating the position precision of the tube level through a conversion formula.
Preferably, in said step 2, the row pixel values P of the top end of the cylindrical tube wall in the tube level are found respectively RL And P RR Taking the average value of the two as the actual line pixel coordinate value of the top end of the cylindrical tube wall in the tube level, namely
Preferably, in the step 5, on the basis of obtaining the bubble outer contour in the step 4, then traversing the point set representing the bubble outer contour, and finding the point with the minimum column pixel coordinate and the point with the maximum column pixel coordinate, that is, the column pixel coordinate P of the left end point of the bubble respectively 3 Column pixel coordinate P with bubble right end point 4 (ii) a And then combining the column pixel coordinate P of the line width midpoint of the left inner scale mark detected in the step 1 CL And column pixel coordinate P of middle point of line width of right inner side scale mark CR The formula for solving the pixel value P of the bubble offset is:
the distance between the inner scale marks of the pipe level in the horizontal ruler to be measured is assumed to be d l The circle radius corresponding to the radian of the bubble in the tube level gauge is d ρ Parameter d of l And d ρ Obtaining the model of the measured horizontal ruler by searching; then, the tube level position accuracy value e is calculated according to the following formula:
thereby obtaining a tube level position accuracy value e.
Preferably, the tube level position accuracy measuring method based on image processing of the invention is used for detecting products or components of a level, a tube level assembly and the like which reflect position accuracy through bubbles.
Preferably, the position accuracy of the product or assembly detected by the pipe level position accuracy measuring method based on image processing of the present invention includes at least one of horizontal accuracy, vertical accuracy, 45-degree position accuracy and position accuracy of any angle.
Compared with the prior art, the invention has the following obvious substantive characteristics and remarkable advantages:
1. the invention is innovative on the algorithm of image processing, and can quickly calculate the position precision of the level ruler with the bubbles between two scale marks;
2. according to the invention, the pixel coordinate information for segmenting the ROI (region of interest) is rapidly obtained in a pixel traversal mode, so that the bubble outline of the ROI is rapidly and accurately found and the column pixel coordinate values of the left end point and the right end point of the bubble outline are calculated, and therefore, the rapid and accurate calculation of the position precision of the pipe water level is realized, and the detection efficiency of the position precision of the level is greatly improved;
3. according to the invention, the bubble outline is directly positioned according to the outline length, so that the problem of bubble outline misdetection is avoided; on the other hand, the processing is carried out based on the ROI, the processing area range is small, the detection speed is higher, and the stability is higher;
4. the method has better robustness, reliability and higher detection efficiency.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
Figure 2 is an image of a tube level on a level according to the method of the present invention.
Fig. 3 is an original image obtained by the camera according to the method of the present invention.
FIG. 4 is an image of an original image obtained by the method of the present invention after filtering, thresholding and dilation.
The + symbol in the middle of fig. 5 represents the starting point of the pixel traversal when the method of the present invention is looking for the left and right inner scale lines.
Fig. 6 is an image of the ROI area obtained by the method of the present invention based on fig. 4.
FIG. 7 is a contour extracted by the method of the present invention from contour extraction of the ROI area of FIG. 6.
Detailed Description
The above-described scheme is further illustrated below with reference to specific embodiments, which are detailed below:
the first embodiment is as follows:
in the present embodiment, referring to fig. 1, a method for measuring the position accuracy of a pipe level based on image processing is implemented according to the following steps:
step 1: performing median filtering, threshold fixing and expansion processing on an original image captured by a camera, and searching a right row pixel coordinate P of a left inner side scale mark on the pipe level in a pixel traversal mode l1 And the left column pixel coordinate P of the right inner scale mark r1 And the column pixel coordinate P of the middle point of the line width of the left inner scale mark CL And column pixel coordinate P of middle point of line width of right inner side scale mark CR ；
And 2, step: finding the line pixel coordinate value P of the top end of the cylindrical tube wall in the tube level t ；
And 3, step 3: the right column pixel coordinate P based on the left inner scale mark detected in said step 1 l1 And the left column pixel coordinate P of the right inner scale mark r1 And the row pixel coordinate P of the top end of the cylindrical pipe wall detected in the step 2 t Performing image segmentation on the bubble image;
and 4, step 4: performing contour extraction operation on the segmented image obtained in the step 3 to obtain a contour with the longest contour curve circumference, namely the required bubble outer contour;
and 5: on the basis of acquiring the bubble outline in the step 4, calculating the column pixel coordinate values of the left end point and the right end point of the bubble in the image, and combining the column pixel coordinate P of the line width middle point of the left inner side graduation line detected in the step 1 CL And column pixel coordinate P of middle point of line width of right inner side scale mark CR Calculating the pixel value of the bubble deviation, and then passing through a conversion formulaThe positional accuracy of the tube level is calculated.
The embodiment is innovative on the algorithm of image processing, and can quickly calculate the position accuracy of the level ruler with the bubbles between two scale marks.
Example two:
this embodiment is substantially the same as the first embodiment, and is characterized in that:
in this embodiment, an embodiment of the image processing-based tube level position accuracy measuring method is used for detecting a product or assembly of a level or a tube level assembly which reflects position accuracy through bubbles.
In this embodiment, the position accuracy of the product or assembly detected by the tube level position accuracy measuring method based on image processing of the embodiment includes at least one of horizontal accuracy, vertical accuracy, 45-degree position accuracy and position accuracy at any angle.
The method can detect the position precision of a side including horizontal precision, vertical precision, 45-degree position precision and any angle, can be used for detecting products or components of a level bar and a pipe level assembly which reflect the position precision through bubbles, is wide in application, can solve the practical problems of low efficiency and large operation error, and has better robustness and reliability and higher detection efficiency.
Example three:
this embodiment is substantially the same as the previous embodiment, and is characterized in that:
in this embodiment, as shown in fig. 1, the tube level position accuracy measuring method based on image processing includes the steps of:
step 1: performing median filtering, threshold fixing and expansion processing on an original image captured by a camera, and searching a right row pixel coordinate P of a left inner side scale mark on the pipe level in a pixel traversal mode l1 And the left column pixel coordinate P of the right inner scale mark r1 And column pixel coordinate P of middle point of line width of left inner scale line CL And column pixel coordinate P of middle point of line width of right inner side scale mark CR (ii) a As labeled in fig. 3;
for the original image (Src)Removing noise in the image by line median filtering, as shown in fig. 3, then performing threshold operation based on a fixed value, converting the image into a binary image, and then performing dilation operation to further remove micro areas and useless corner defect image information in the image, so as to obtain a preprocessed image (DImg), as shown in fig. 4; then, performing pixel traversing operation on the image DImg, searching left and right inner side scale marks, wherein a traversing starting point is the middle point position of the whole image, such as the position of the plus sign shown in FIG. 5; in order to traverse the right and left inner side scale lines correctly, the relative position of the camera and the measured horizontal ruler is adjusted to ensure that the photographed tube level on the horizontal ruler is positioned in the middle of the whole image as much as possible, and FIG. 5 is that the middle position of the whole image is marked by a symbol on the basis of FIG. 4; the detailed traversal steps are as follows: assuming that the whole image has a height H and a width W, the position of the midpoint of the whole image, i.e., the center of the whole image
Finding black pixel points at the pixel coordinates to the left and the right in a pixel traversal mode, and respectively finding the pixel coordinates P of the right column of the left inner scale mark l1 And the left column pixel coordinate P of the right inner scale line r1 (ii) a In finding P l1 And P r1 Then, continuously traversing along the previous direction, this time searching for white pixel points, and sequentially searching for the left row pixel coordinate P of the left inner side scale mark l2 And the right column pixel coordinate P of the right inner scale mark r2 And respectively calculating the row pixel coordinate values of the respective line width midpoints of the left and right inner side scale lines according to the traversal result
And
and 2, step: on the basis of the image processed in the step 1, searching a line pixel coordinate value P of the top end of the cylindrical pipe wall in the pipe level t As indicated by the label in fig. 2;
since the left side is found in step 1Line pixel coordinate value of line width midpoint of inner scale mark
And the row pixel coordinate value of the middle point of the line width of the right inner side scale mark
From point
And
traversing pixels upwards, namely traversing upwards to find white pixel points in the interior of the scale mark, and when the white pixel points appear, indicating that the white pixel points reach the upper end point of the scale mark in the pipe level, as shown in fig. 5, wherein the upper end point of the scale mark is also the top end of the cylindrical pipe wall in the pipe level; thereby respectively finding the row pixel value P of the top end of the cylindrical pipe wall in the pipe level RL And P RR Taking the average value of the two as the actual line pixel coordinate value of the top end of the cylindrical tube wall in the tube level, namely
And 3, step 3: based on the right column pixel coordinate P of the left inner scale mark detected in step 1 l1 And the left column pixel coordinate P of the right inner scale mark r1 And the line pixel coordinate P of the top end of the cylindrical pipe wall detected in the step 2 t Performing image segmentation on the bubble image;
based on the right column pixel coordinate P of the left inner scale mark detected in step 1 l1 And the left column pixel coordinate P of the right inner scale mark r1 Calculating an ROI area (region of interest) to be divided, wherein pixel coordinate values of an upper left vertex and a lower right vertex of the ROI area in the image are (P) l1 ，P t ) And
then only the ROI area is neededProcessing is carried out without processing the whole image, so that a large number of useless contours can be avoided being extracted, the outer contour of the bubble can be conveniently and accurately positioned, and the detection efficiency is improved; the ROI area image is shown in FIG. 6;
and 4, step 4: carrying out contour extraction operation on the segmented image obtained in the step 3 to obtain a contour with the longest contour curve circumference, namely the required bubble contour;
according to the shape of the bubble in fig. 7, after the contour extraction algorithm is executed, at least two contours are extracted, one is an outer contour representing the outer side of the bubble, the other is an inner contour representing the inner side of the bubble, and other contour areas may exist in the bubble; by comparing the circumferences of the contour lines of the extracted contours, the longest contour line is the bubble contour, so that the target contour is determined;
and 5: calculating the column pixel coordinate values of the left and right end points of the bubble in the image on the basis of the acquired bubble outline in the step 4, and combining the column pixel coordinate values P of the line width midpoint of the left and right inner scale lines detected in the step 1 CL And P CR Calculating the pixel value of the bubble offset, and then calculating the position precision of the tube level through a conversion formula;
because the outer contour of the bubble is found in the step 4, the point set representing the outer contour of the bubble is traversed, and the point with the minimum column pixel coordinate and the point with the maximum column pixel coordinate, namely the column pixel coordinate P of the left end point of the bubble respectively, are found 3 Column pixel coordinate P with bubble right end point 4 (ii) a Combining the row pixel coordinate values P of the respective line width midpoints of the left and right inner side scale marks detected in the step 1 CL And P CR The formula for solving for the pixel value P (in pixels) of the bubble offset is:
the distance between the inner scale marks of the pipe level in the horizontal ruler to be measured is assumed to be d l mm, the radius of the circle corresponding to the radian of the bubble in the pipe level gauge is d ρ mm, parameter d l And d ρ The model of the measured horizontal ruler can be searched; then, the tube level position accuracy value e may be calculated according to the following equation:
therefore, the position accuracy of the pipe level gauge based on image processing is rapidly measured.
The embodiment is innovative on the algorithm of image processing, and can quickly calculate the position accuracy of the level ruler with the bubbles between two scale marks. The pixel coordinate information for segmenting the ROI (region of interest) is quickly obtained in a pixel traversal mode, so that the bubble outline of the ROI is quickly and accurately found, and the column pixel coordinate values of the left end point and the right end point of the bubble outline are calculated, so that the position accuracy of the pipe level is quickly and accurately calculated, and the detection efficiency of the position accuracy of the level is greatly improved.
To sum up, in the method for quickly measuring the position accuracy of the pipe level based on image processing in the above embodiment, the original image of the pipe level is captured by the camera, then the image processing operation is adopted to perform filtering, threshold processing and expansion operation on the image, on the basis, the inner scale mark in the image is searched, and the whole image is cut based on the searched scale mark pixel coordinate value to obtain the required bubble image. And then extracting the outline of the divided bubble image, further finding out pixel coordinate values of left and right end points of the outline of the bubble, calculating a pixel value of the offset of the bubble according to the pixel coordinate information of the left and right end points of the bubble and the pixel coordinate information of the scale mark, and finally calculating the position precision value of the bubble according to the pixel coordinate information of the left and right end points of the bubble and the pixel coordinate information of the scale mark. The above-described embodiment method can be used to detect products or components of levels, pipe level assemblies, and the like, which reflect positional accuracy by bubbles, and can also be used to detect the horizontal accuracy, vertical accuracy, 45-degree positional accuracy, and positional accuracy at arbitrary angles of these products or components.
The embodiments of the present invention have been described with reference to the accompanying drawings, but the present invention is not limited to the embodiments, and various changes and modifications can be made according to the purpose of the invention, and any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention shall be equivalent substitutions, as long as the purpose of the present invention is met, and the present invention shall fall within the protection scope of the present invention without departing from the technical principle and inventive concept of the present invention.
Claims (5)
1. A tube level position accuracy measuring method based on image processing is characterized by comprising the following steps:
step 1: carrying out median filtering, threshold value fixing and expansion processing on an original image captured by a camera, and searching the right column pixel coordinate P of the left inner side scale mark on the tube level in a pixel traversal mode l1 And the left column pixel coordinate P of the right inner scale mark r1 And column pixel coordinate P of middle point of line width of left inner scale line CL And column pixel coordinate P of middle point of line width of right inner side scale mark CR ；
And 2, step: finding the line pixel coordinate value P of the top end of the cylindrical tube wall in the tube level t ；
And step 3: the right column pixel coordinate P based on the left inner scale mark detected in said step 1 l1 And the left column pixel coordinate P of the right inner scale mark r1 And the row pixel coordinate P of the top end of the cylindrical pipe wall detected in the step 2 t Performing image segmentation on the bubble image;
and 4, step 4: performing contour extraction operation on the segmented image obtained in the step 3 to obtain a contour with the longest contour curve circumference, namely the required bubble outer contour;
and 5: calculating the column pixel coordinate values of the left and right end points of the bubble in the image on the basis of the acquired bubble profile in the step 4, and combining the column pixel coordinate P of the middle point of the line width of the left inner scale mark detected in the step 1 CL And column pixel coordinate P of middle point of line width of right inner side scale mark CR Calculating the pixel value of the bubble offset, and calculating the tube level by a conversion formulaThe position accuracy.
2. The image-processing-based tube level position accuracy measuring method according to claim 1, wherein in the step 2, the line pixel values P of the top end of the cylindrical tube wall in the tube level are respectively found RL And P RR Taking the average value of the two as the actual line pixel coordinate value of the top end of the cylindrical tube wall in the tube level, namely
3. The image-processing-based tube level position accuracy measuring method according to claim 1, wherein in the step 5, on the basis of the acquired bubble outer contour in the step 4, a point set representing the bubble outer contour is traversed to find a point with the minimum column pixel coordinate and a point with the maximum column pixel coordinate, namely, a column pixel coordinate P of a left end point of the bubble respectively 3 Column pixel coordinate P with bubble right end point 4 (ii) a And then combining the column pixel coordinate P of the middle point of the line width of the left inner scale mark detected in the step 1 CL And column pixel coordinate P of middle point of line width of right inner side scale mark CR The formula for solving the pixel value P of the bubble offset is:
assuming that the distance between the inner scale marks of the pipe level in the measured level ruler is d l The radius of the circle corresponding to the radian of the bubble in the pipe level gauge is d ρ Parameter d l And d ρ Obtaining the model of the measured pipe level by searching; then, the tube level position accuracy value e is calculated according to the following formula:
thereby obtaining a tube level position accuracy value e.
4. The image processing-based pipe level position accuracy measuring method according to claim 1, characterized in that: the method is used for detecting products or components of level bars and tube level gauge components which react to position accuracy through bubbles.
5. The image processing-based pipe level position accuracy measuring method according to claim 1, characterized in that: the position accuracy of the detected product or component comprises at least one of horizontal accuracy, vertical accuracy, 45-degree position accuracy and position accuracy of any angle.
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| CN103206947B (en) * | 2012-01-16 | 2016-09-28 | 中国科学院声学研究所 | A kind of inclination angle measurement method based on air level and device thereof |
| CN205449099U (en) * | 2016-04-01 | 2016-08-10 | 武汉大学 | Automatic anping surveyor's level compensating error of compensator detecting system |
| EP3516331B1 (en) * | 2016-09-25 | 2021-07-21 | Israel Aerospace Industries Ltd. | Method of calibrating a computerized leveling offset meter |
| CN108592948B (en) * | 2018-04-28 | 2023-03-14 | 中国计量大学 | Automatic measurement method for bubble offset of pipe level |
| CN108613630B (en) * | 2018-04-28 | 2022-03-11 | 中国计量大学 | Two-wire tube level bubble offset measurement method based on image processing technology |
| CN108876860B (en) * | 2018-04-28 | 2023-06-20 | 中国计量大学 | Image calibration method for measuring bubble offset of tube level |
| CN108534802B (en) * | 2018-04-28 | 2023-03-14 | 中国计量大学 | Tube level bubble deviation measurement method based on image processing technology |
| CN109883396B (en) * | 2018-10-09 | 2020-11-24 | 中国计量大学 | Leveling bubble reticle width measuring method based on image processing technology |
| CN109900302A (en) * | 2019-04-09 | 2019-06-18 | 中国计量大学 | A kind of more groove level tube bubbles error vision measuring method placed in the middle |
| CN210268631U (en) * | 2019-08-06 | 2020-04-07 | 苏州迈普工具有限公司 | Level bar convenient to discernment bubble |
| CN111862055B (en) * | 2020-07-23 | 2024-03-05 | 中国计量大学 | Bubble turning cavity defect detection method based on image processing |
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