CN108592948B - Automatic measurement method for bubble offset of pipe level - Google Patents

Abstract

The invention discloses a method for automatically measuring the bubble offset of a tube level. The specific implementation content is as follows: the method of the invention adopts the method of automatically determining the region of interest to operate the gray image of the original tube level to obtain the image of the region of interest. Determine the offset position of the bubble in the image of interest. If the bubble enters the fixed area of the calculated offset and the center of the bubble crescent is far from the center of the fixed area, roughly calculate the bubble offset; if the center of the bubble crescent is far from the center of the fixed area When it is close, the offset of the bubble is accurately calculated, and finally the measurement of the offset of the bubble in the vial is realized according to the image calibration result. The method of the present invention uses machine vision to effectively solve the time-consuming and labor-intensive problems of human-eye recognition and large errors. The method uses the horizontal distance value between the center of the bubble and the center of the rectangle surrounded by two black lines to represent the actual offset. The algorithm has Innovative and robust, yet simple and practical with high precision.

Description

A method for automatic measurement of bubble offset in tube vial

technical field

The invention relates to the technical field of machine vision measurement, and relates to a method for automatically measuring the bubble offset of a tube level.

Background technique

In many industrial manufacturing activities, people often need to check the flatness of the surface of the measured object. Therefore, some measuring instruments with tube levels (for example: spirit levels, etc.) are usually used to complete this type of precision measurement. The most widely used method is to judge whether the surface of the measured object is level by measuring the bubble offset in the tube level. There are many measuring instruments with tube levels on the market today, which are used to test the flatness of the surface of the measured object. Bubbles in the level are detected and calibrated. The general calibration method is to place the measuring instrument with a tube level on a standard level detection platform, and judge whether the factory-made measuring instrument is qualified according to the degree of deviation of the air bubbles in the tube level from the center. Measuring instruments with different precisions have different allowable error ranges during detection. At present, the commonly used detection methods for the bubble offset in the tube vial in China are as follows:

(1) The displacement of the air bubbles in the vial is recognized by human eyes to judge whether the measuring instrument is qualified or not. Calibration of the product is only a way of manually adjusting the vial. Obviously, this method not only has large errors, but also Also consume a large amount of manpower and material resources, product precision is difficult to be improved.

(2) Measure the bubble offset based on Canny edge detection and weighted least squares. Although this method has strong robustness for poor quality images, the calculated bubble offset found by this method The fixed bounding area of is not precise enough, resulting in significant errors in the final calculated bubble offset.

(3) Use the method of local gray gradient average curve and sub-pixel precision positioning to measure the bubble offset. Although this method has a high accuracy for extracting the edge point of the bubble outline, it is difficult to measure the corrected tube level in the actual measurement. During the process of air bubbles, it will be affected by the vibration of the motor. When the air bubbles are adjusted, their contour shape will change slightly. Therefore, if only the left and right endpoints of the air bubbles are extracted for offset measurement during the continuous adjustment process, it will seriously affect to the measurement accuracy of the entire measurement process.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a method for automatically measuring the bubble offset of a vial, which adopts the method of automatically determining the region of interest, and when the center of the bubble just enters the center of the fixed area for calculating the bubble offset , using a rough measurement method; when the center of the bubble is close to the center of the fixed area where the bubble offset is calculated, an accurate measurement method is used; the measurement accuracy is improved, and at the same time, it can be used for machines to replace human beings to correct measuring instruments with tube levels and solve the problem It solves the problems of human eye recognition, manual tapping, time-consuming and labor-intensive, and large errors.

The technical solution adopted in the present invention is a method for automatically measuring the bubble offset of a tube level, which is specifically implemented according to the following steps:

Step 1: Read the original grayscale image of the bubble in the vial;

Step 2: Perform binarization and median filtering on the original grayscale image;

Step 3: Perform contour detection on the binary image after median filtering, and calculate the ratio of the area of the area surrounded by each contour to the area of the smallest circumscribing rectangle of each contour and the length of the long side of the smallest circumscribing rectangle of each contour;

Step 4: Determine whether there is a fixed area in the image for calculating the bubble offset by the ratio of the area enclosed by each contour to the area of the smallest circumscribing rectangle of each contour and the length of the long side of the smallest circumscribing rectangle of each contour;

Step 5: If there is a fixed area for calculating the bubble offset, then expand the fixed area for calculating the bubble offset to obtain the region of interest;

Step 6: Obtain the inclination angle of the smallest circumscribed rectangle of the fixed area for calculating the bubble offset, and the ratio of the area enclosed by the outline of the fixed area to the area of the smallest circumscribed rectangle of the outline of the fixed area, and judge the bubble according to the inclination and ratio offset position;

Step 7: If the bubble enters the fixed area where the bubble offset is calculated, calculate the horizontal physical distance between the center of the smallest circumscribed rectangle of the crescent-shaped area generated by the reflection of the bubble and the center of the smallest circumscribed rectangle of the fixed area, and roughly measure the offset of the bubble;

Step 8: If the horizontal physical distance between the center of the smallest bounding rectangle of the crescent-shaped area and the center of the smallest bounding rectangle of the fixed area where the offset of the bubble is calculated is very small, then calculate the center of the bounding rectangle surrounding the largest contour of the perimeter of the bubble and the center of the smallest bounding rectangle of the fixed area The horizontal physical distance of , accurately measure the offset of the bubble.

The beneficial effect of the present invention is that, according to the different positions of the bubbles in the vial, the image processing technology is used to calculate the distance between the center of the crescent-shaped area of the bubble or the center of the overall area of the bubble deviating from the center of the fixed area of the vial, so as to realize the bubble offset of the vial Measurement. The method of the present invention can effectively solve the problems of time-consuming, laborious and large errors when using human eyes to identify, and the method of using the horizontal distance value between the center of the bubble and the center of the rectangle surrounded by two black lines replaces the left and right edge points of the bubble outline and the two black lines The method of the horizontal distance value of the contour center calculates the actual offset. The former algorithm is more robust, simple and practical, and has high precision.

Description of drawings

Fig. 1 is a flow chart of the steps of the inventive method;

Fig. 2 is the initial image that the inventive method obtains;

Fig. 3 is the binarized median filter image that the inventive method obtains;

Fig. 4 is the contour detection image that the inventive method obtains;

Fig. 5 is the actual surrounding contour image of the fixed area obtained by the method of the present invention;

Fig. 6 is the circumscribed rectangular image of the fixed region obtained by the method of the present invention;

Fig. 7 is the region of interest image obtained by the method of the present invention;

Fig. 8 is the region-of-interest binary image obtained by the method of the present invention after eliminating short 0 strokes;

Fig. 9 is the minimum circumscribed rectangle image marked with a bubble crescent-shaped region obtained by the method of the present invention;

Fig. 10 is the inverse image of the bubble binarization obtained by the method of the present invention;

Fig. 11 is an image of a circumscribed rectangle marked with the largest perimeter of the bubble contour acquired by the method of the present invention.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing.

As shown in Figure 1, the step of the inventive method is:

Step 1: Read the original grayscale image of the tube vial bubble

Read the original grayscale image of the bubble in the vial to be measured for the bubble offset, and the result is shown in Figure 2

Step 2: Binarize and median filter the original grayscale image

The original grayscale image src is binarized and segmented by the OTSU method to obtain the binarized image BI; the 5X5 window is used to remove the noise by the median filter for BI, and the filtered image I _filt is obtained, as shown in Fig. 3 .

Step 3: Perform contour detection on the binary image after median filtering, and calculate the ratio of the area enclosed by each contour to the area of the smallest circumscribing rectangle of each contour and the length of the long side of the smallest circumscribing rectangle of each contour

Contour detection is performed on the filtered image I _filt , and the obtained contour detection image is shown in FIG. 4 . Calculate the ratio R i of the actual enclosing area Area _i of each contour C _i in the median filtered image I _filt to the area of the smallest circumscribing rectangle R _i , and the length of the long side L _i of the smallest circumscribing rectangle, where i=1,2,3, ..., N, N is the number of contours in the image I _filt after median filtering.

Step 4: Determine whether there is a fixed area in the image for calculating the bubble offset through the ratio of the area enclosed by each contour to the area of the smallest circumscribing rectangle of each contour and the length of the long side of the smallest circumscribing rectangle of each contour.

Limit the ratio R i of the area enclosed by each contour obtained in step 3 to the area of the smallest circumscribed rectangle of each contour R _i and the length L _i of the smallest circumscribed rectangle of each contour. When the ratio R _i is greater than a certain value T _R and the length When the side length L _i is within a fixed range [L ₁ , L _h ], that is:

R _i >T _R and L ₁ ≤L _i ≤L _h (1)

Then it is determined that there is a fixed region Rect for calculating the bubble offset in the image I _filt after median filtering, and the contour satisfying the formula (1) is set as the contour C _R of the fixed region Rect, and the subsequent processing is continued; otherwise, it is judged as medium After value filtering, there is no fixed area outline for calculating the bubble offset in the image I _filt , and the message "bubble is not in the current image" will be given, and no subsequent processing will be performed.

Step 5: If there is a fixed area for calculating the bubble offset, then expand the fixed area for calculating the bubble offset to obtain the region of interest

If there is a fixed region contour C _R for calculating the bubble offset in the image I _filt after median filtering, first obtain the circumscribed rectangle R _Max of the fixed region contour C _R , as shown in FIG. 6 . Then expand the rectangle R _Max upwards, downwards, leftwards and rightwards by a certain distance iOffset to obtain the rectangle R _N . The region image I roi contained in the median-filtered image I _filt of the rectangle R _N is extracted from the median-filtered image _{I filt} as the region-of-interest image, and the region-of-interest image I _roi is shown in FIG. 7 . At the same time, let the coordinates of the first pixel in the upper left corner of the region of interest image I _roi in the original grayscale image src be (TL _x , TL _y ).

Step 6: Calculate the inclination angle of the smallest circumscribed rectangle of the fixed area for calculating the bubble offset, and the ratio of the area enclosed by the outline of the fixed area to the area of the smallest encircled rectangle of the outline of the fixed area, and judge the bubble according to the inclination and ratio offset of

Calculate the inclination angle θ of the minimum circumscribed rectangle MER of the fixed region contour _C R and the ratio R of the area actually enclosed by the fixed region contour C _R to the area of the minimum circumscribed rectangle, and judge the current position of the bubble. If R is greater than a certain value T _RN , Then it is determined that the bubble is outside the fixed area where the bubble offset is calculated; when the bubble is outside, it can be determined according to the inclination angle of the fixed area where the bubble offset is calculated. Determine which side the bubble is on; if θ<-45°, the bubble is on the left side outside the fixed area where the bubble offset is calculated, and a message prompt "bubble is on the left side of the fixed area" is given; otherwise, the bubble is in the calculation bubble On the right side outside the fixed area of the offset, the information prompt "bubble is on the right side of the fixed area" is given.

Step 7: If the bubble enters the fixed area where the bubble offset is calculated, calculate the horizontal physical distance between the center of the smallest circumscribed rectangle of the crescent-shaped area generated by the reflection of the bubble and the center of the smallest circumscribed rectangle of the fixed area, and roughly measure the offset of the bubble

If the bubble starts to enter the fixed area Rect where the bubble offset is calculated, first look for the crescent-shaped area R _M caused by the reflection of the bubble; in the region of interest image I _roi , perform 0 strokes in order from left to right and from top to bottom The search of , where the 0-stroke is a pixel segment composed of consecutive pixels whose pixel values are 0 in each row; if the length RL of a certain 0-stroke satisfies a certain interval [Th ₁ ,Th _h ], that is:

Th ₁ ≤ RL ≤ _{Th h} (2)

Then eliminate this short 0 stroke, that is, all black pixels in this stroke will be changed into white pixels. After all the short 0-strokes satisfying the formula (2) are eliminated, the image bI _roi is obtained, as shown in FIG. 8 . Contour detection is performed in the image bI _roi , if the long side length W _f of the smallest circumscribed rectangle of the contour satisfies the formula (3), and there is only one such contour, then it is determined that there is a crescent-shaped region R _M :

W ₁ <W _f <W _h (3)

Among them, W ₁ and W _h are the lower limit and upper limit of the length of the long side of the smallest circumscribed rectangle of the outline in the image of interest.

If there is a contour C _M of the crescent-shaped region R _M , then the minimum circumscribed rectangle M _m of the crescent-shaped region R _M is calculated, as shown in Figure 9, the center of the minimum circumscribed rectangle M _m of the crescent-shaped region is set as M _c , The abscissa of M _c in the region of interest image I _roi is set to MC _x , then the abscissa M _x of the center M _c of the smallest circumscribed rectangle of the crescent-shaped area in the original grayscale image src is:

M _x =MC _x +TL _x (4)

Among them, TL _x is the abscissa of the first pixel in the upper left corner of the region of interest image I _roi in the original grayscale image src.

The center of the minimum circumscribed rectangle MER of the fixed area Rect for calculating the bubble offset is ME _c , and the abscissa of ME _c in the original grayscale image src is ME _x ; use the minimum circumscribed rectangle of the fixed area for calculating the bubble offset The difference between the central abscissa ME _x and the abscissa M _x of the center of the circumscribed rectangle of the crescent-shaped area in the original grayscale image src is the difference △X ₁ , which represents the offset of the bubble in the image, and the unit is pixel:

△X ₁ ＝ME _x -M _x (5)

If △X>0, the bubble is to the left; otherwise, the bubble is to the right. According to the image calibration result Res, the unit is mm/pixel, roughly calculate the bubble physical offset dR ₁ , the unit is mm:

dR ₁ =|△X ₁ |×Res (6)

Where |△X ₁ | represents the absolute value of △X ₁ ;

If △X ₁ >0, give the information prompt of "the bubble is XX mm to the left"; otherwise, give the information prompt of "the bubble is XX mm to the right", where XX is the value of dR ₁ .

Step 8: If the horizontal physical distance between the center of the smallest circumscribing rectangle of the crescent-shaped area and the center of the smallest circumscribing rectangle of the fixed area where the offset of the bubble is calculated is less than 1mm, calculate the center of the circumscribing rectangle surrounding the largest contour of the perimeter of the bubble and the center of the smallest circumscribing rectangle of the fixed area The horizontal physical distance of , accurately measure the offset of the bubble

If the horizontal distance between the minimum circumscribed rectangle center M _c of the crescent-shaped area and the minimum circumscribed rectangle center ME _c of the fixed area for calculating the bubble offset is less than a certain threshold dT, that is, |dR ₁ |<dT, then the median filtered image In I _filt , intercept the image of the area corresponding to the circumscribed rectangle _{R Max} of the contour CR of the fixed area and perform an inversion operation on it to obtain the inverse image I _sub , as shown in Figure 10; perform contour detection on the image I _sub , and extract Get the contour C _B with the largest perimeter, and the contour C _B is the bubble contour; calculate the circumscribed rectangle R _B of the bubble contour C _B , as shown in Figure 11, the abscissa of the center MB _c of the circumscribed rectangle R _B of the bubble contour is set to MB _x , then the abscissa M _b of the center MB _c of the circumscribed rectangle of the bubble outline in the original grayscale image src is:

M _b =MB _x +TL _N (7)

Wherein, TL _N is the abscissa of the first pixel in the upper left corner of the image I _sub in the original grayscale image src .

The bubble offset is represented by the difference △X ₂ between the abscissa ME _x of the center of the circumscribed rectangle of the fixed area for calculating the bubble offset and the abscissa M _b of the center of the circumscribed rectangle of the bubble outline in the original grayscale image src, and the unit is pixel :

△X ₂ =ME _x -M _b (8)

According to the image calibration result Res, the unit is mm/pixel), accurately calculate the bubble physical offset dR ₂ , the unit is mm:

dR ₂ =|△X ₂ |×Res (9)

where |△X ₂ | represents the absolute value of △X ₂ .

If dR ₂ >0, give the information prompt of "the bubble is XX mm to the left"; otherwise, give the information prompt of "the bubble is XX mm to the right"; where XX is the absolute value of dR ₂ ; when |dR ₂ |<TP , it is determined that the bubble is in the center of the vial, and a "qualified" message is given, where TP is the maximum allowable error of the given bubble offset.

Claims (8)

1. A method for automatically measuring the bubble offset of a pipe level is characterized by comprising the following steps:

step 1, reading an original gray image of a bubble of a pipe level;

step 2: carrying out binarization and median filtering processing on the original gray level image;

and step 3: carrying out contour detection on the binary image after median filtering, and calculating the ratio of the area of the region surrounded by each contour to the minimum circumscribed rectangle area of each contour and the length of the long side of the minimum circumscribed rectangle of each contour;

and 4, step 4: judging whether a fixed region for calculating the bubble offset exists in the image or not by limiting the ratio of the area of the region surrounded by each outline to the area of the minimum circumscribed rectangle of each outline and the length of the long side of the minimum circumscribed rectangle of each outline;

and 5: if a fixed area for calculating the bubble offset exists, carrying out external expansion on the fixed area for calculating the bubble offset to obtain an interested area;

step 6: calculating the inclination angle of the minimum circumscribed rectangle of the fixed region for calculating the bubble offset, and the ratio of the area of the region surrounded by the outline of the fixed region to the area of the minimum circumscribed rectangle of the outline of the fixed region, and judging the offset position of the bubble according to the inclination angle and the ratio;

and 7: if the bubbles enter the range of the fixed area for calculating the bubble offset, calculating the horizontal physical distance between the center of the minimum external rectangle of the crescent area generated by reflecting light of the bubbles and the center of the minimum external rectangle of the fixed area, and roughly measuring the offset of the bubbles;

and 8: and if the horizontal physical distance between the center of the minimum external rectangle of the crescent area and the center of the minimum external rectangle of the fixed area for calculating the bubble offset is very small, calculating the horizontal physical distance between the center of the external rectangle surrounding the maximum outline of the bubble perimeter and the center of the minimum external rectangle of the fixed area, and accurately measuring the offset of the bubble.

2. The method for automatically measuring the bubble offset of the pipe level according to claim 1, wherein the step 2 is specifically performed according to the following procedures:

carrying out binarization segmentation processing on the original gray level image src by adopting an OTSU method to obtain a binarization image BI; median filtering is carried out on the BI by adopting a 5 multiplied by 5 window to remove noise, and a filtered image I is obtained _filt 。

3. The method for automatically measuring the bubble offset of the pipe level according to claim 1, wherein the step 3 is specifically performed according to the following steps:

for filtered image I _filt Contour detection is carried out, and a median filtered image I is calculated _filt Of each contour C _i Actual Area of enclosure Area of _i The ratio R of the minimum circumscribed rectangular area _i And length L of the long side of the minimum bounding rectangle _i Wherein I =1,2, 3.. And N, N is the median filtered image I _filt The number of the middle outlines.

4. The method for automatically measuring the bubble offset of the pipe level according to claim 1, wherein the step 4 is specifically performed according to the following procedures:

the ratio C of the area surrounded by each contour obtained in the step 3 to the minimum circumscribed rectangle area of each contour _i And length L of long side of minimum circumscribed rectangle of each outline _i Limiting when the ratio C is _i Greater than a certain constant value T _R And the length L of the long side _i Within a certain fixed range [ L ₁ ,L _h ]When the internal pressure is within the range:

R _i >T _R and L is ₁ ≤L _i ≤L _h (1)

It is determined as the median filtered image I _filt There is a fixed region Rect in which to calculate the bubble offset, and the contour satisfying the formula is set to the contour C of the fixed region Rect _R Continuing to perform subsequent processing; otherwise, judging the image I after median filtering _filt The contour of a fixed area for calculating the bubble offset does not exist, and the information prompt of 'the bubble is not in the current image' is given, so that the subsequent processing is not performed any more.

5. The method for automatically measuring the bubble offset of the pipe level according to claim 1, wherein the step 5 is specifically performed according to the following steps:

if the median value is filtered image I _filt In which there is a fixed area contour C for calculating the amount of bubble offset _R Then, first, the contour C of the fixed region is obtained _R Is a circumscribed rectangle R _Max Then, the rectangle R is put _Max Extending a certain distance iOffset upwards, downwards, leftwards and rightwards to obtain a rectangle R _N Will be rectangular R _N Image I after median filtering _filt Area image I contained in _roi Median filtered image I as region of interest image _filt Extracting; meanwhile, setting a region of interest image I _roi The coordinate of the first pixel point at the top left corner in the original gray level image src is (TL) _x ,TL _y )。

6. The method for automatically measuring the bubble offset of the pipe level according to claim 1, wherein the step 6 is specifically performed according to the following steps:

calculating a fixed region contour C _R And the minimum circumscribed rectangle MER and the constant area profile C _R The ratio R of the Area actually surrounded to the minimum circumscribed rectangle Area of the Area is used for judging the current position of the bubble, and if R is larger than a certain fixed value T _RN If so, judging that the air bubble is outside the fixed area for calculating the air bubble offset; when the air bubble is on the outer side, the air bubble on which side is positioned can be judged according to the inclination angle of the fixed area for calculating the offset of the air bubble; if theta is greater than theta<45 degrees, the air bubble is on the left side outside the fixed area for calculating the air bubble offset, and an information prompt that the air bubble is on the left side of the fixed area is given; otherwise, the bubble is outside the fixed area of the calculated bubble offset and is on the right side, and an information prompt that the bubble is on the right side of the fixed area is given.

7. The method for automatically measuring the bubble offset of the pipe level according to claim 1, wherein the step 7 is specifically performed according to the following steps:

if the bubble begins to enter the fixed area Rect for calculating the bubble offset, firstly, a crescent area R caused by bubble reflection is searched _M (ii) a In a region of interest image I _roi The 0 stroke is searched from left to right and from top to bottom, wherein the 0 stroke is a pixel segment formed by continuous pixels of which the pixel values of each row are 0; if a certain 0 lineThe length of the range RL satisfies the requirement of belonging to a certain interval Th ₁ ,Th _h ]When, namely:

Th ₁ ≤RL≤Th _h (2)

the short 0 stroke is eliminated, namely all black pixels in the stroke are changed into white pixels; all short 0 strokes satisfying the formula (2) are eliminated to obtain an image bI _roi (ii) a In the image bI _roi If the length W of the long side of the minimum bounding rectangle of the contour is detected _f Satisfying equation (3), and such contours have only 1, it is determined that the crescent-shaped region R exists _M ：

W ₁ <W _f <W _h (3)

Wherein, W _f And W _h The lower limit value and the upper limit value of the length of the long side of the outline minimum circumscribed rectangle in the interested image are set;

if there is a crescent shaped region R _M Is (C) _M Then, the crescent-shaped region R is obtained _M Minimum circumscribed rectangle M of _m The minimum external rectangle M of the crescent area _m Is set as M _c ，M _c In a region of interest image I _roi The abscissa of (A) is set as MC _x Then the center M of the minimum circumscribed rectangle of the crescent area _c Abscissa M in original grayscale image src _x Comprises the following steps:

M _x ＝MC _x +TL _x (4)

wherein, TL _x For an image I of a region of interest _roi The abscissa of the first pixel point at the top left corner in the original gray level image src;

setting the center of the minimum circumscribed rectangle MER of the fixed region Rect for calculating the bubble offset as ME _c ，ME _c The abscissa in the original grayscale image src is ME _x (ii) a With minimum circumscribed rectangle center abscissa ME of fixed area for calculating bubble offset _x An abscissa M of a center of a rectangle circumscribed to the crescent region outline in the original gray level image src _x Difference value DeltaX between ₁ To indicate the amount of displacement of the bubble in the image, in units of pixel：

△X ₁ ＝ME _x -M _x (5)

If Δ X>0, the bubble is left; otherwise, the bubble is deflected to the right; roughly calculating the physical bubble offset dR according to the image calibration result Res in mm/pixel ₁ In mm:

dR ₁ ＝|△X ₁ |×Res (6)

wherein |. DELTA.X ₁ | represents Δ X ₁ Absolute value of (d);

if Δ X ₁ >0, giving an information prompt of 'the air bubble is deviated from the left by XX mm'; otherwise, giving an information prompt of 'the air bubble is deviated from right XX mm'; wherein XX is dR ₁ The value of (c).

8. The method as claimed in claim 1, wherein the step 8 is performed according to the following steps:

if the minimum external rectangle center M of the crescent area _c ME (minimum bounding rectangle center) of fixed region for calculating bubble offset _c Is less than a threshold value dT, i.e. | dR ₁ |<dT, then image I filtered from the median _filt Middle cut fixed area outline C _R Is a circumscribed rectangle R _Max The image of the corresponding area is inverted to obtain an inverted image I _sub (ii) a For image I _sub Detecting the contour and extracting the contour C with the maximum perimeter _B Contour C _B Namely the bubble profile; calculating the bubble profile C _B Is a circumscribed rectangle R _B The outline of the bubble is circumscribed by a rectangle R _B Center MB of _c The abscissa of (a) is set as MB _x The outline of the bubble circumscribes the center MB of the rectangle _c Abscissa M in original grayscale image src _b Comprises the following steps:

M _b ＝MB _x +TL _N (7)

wherein, TL _N Is an image I _sub The first pixel point at the top left corner of the original gray image src sits transverselyMarking;

fixed region circumscribed rectangle center abscissa ME for calculating bubble offset _x Abscissa M of the center of the rectangle circumscribing the bubble outline in the original grayscale image src _b Difference of (A) Δ X ₂ To represent the bubble offset, in pixel:

△X ₂ ＝ME _x -M _b (8)

accurately calculating the physical bubble offset dR according to the image calibration result Res in mm/pixel ₂ In mm:

dR ₂ ＝|△X ₂ |×Res (9)

wherein |. DELTA.X ₂ | represents Δ X ₂ Absolute value of (d);

if dR ₂ >0, giving an information prompt of 'the air bubble is deviated from the left by XX mm'; otherwise, giving an information prompt of 'the air bubble is deviated from the right by XX mm', wherein XX is dR ₂ Absolute value of (d); when | dR ₂ |<And at TP, judging that the air bubble is positioned at the center of the tube level, and giving a qualified information prompt, wherein TP is the maximum allowable error of the given air bubble offset.

Images