Measurement Method of Inner Surface Size of Hole Based on Distortion Correction of Endoscopic Image

Qiang Sheng; Jianming Zheng; Ting Chen; Xiuxiu Yang; Xianming Gao

doi:10.3788/AOS221502

Acta Optica Sinica, Volume. 43, Issue 3, 0312006(2023)

Measurement Method of Inner Surface Size of Hole Based on Distortion Correction of Endoscopic Image

Qiang Sheng^1,2、*, Jianming Zheng^1、**, Ting Chen¹, Xiuxiu Yang³, and Xianming Gao²

¹School of Mechanical and Precision Instrument Engineering, Xi′an University of Technology, Xi′an, 710048, Shaanxi, China

²College of Mechanical and Electrical Engineering, Shaanxi University of Science and Technology, Xi′an, 710021, Shaanxi, China

³School of Economics and Management, Xi′an University of Technology, Xi′an710054, Shaanxi, China

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Figures & Tables(16)

Fig. 1. Endoscopic imaging principle. (a) Spatial coordinate system; (b) phase plane coordinate system

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Fig. 2. Coordinate system of corrected endoscopic image

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Fig. 3. Principle of axial correction. (a) Distortion effect; (b) correction process

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Fig. 4. Measurement scheme and equipment. (a) Measurement scheme; (b) calibration broad; (c) endoscopic probe sleeve; (d) endoscopic image

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Fig. 5. Preprocessing and center detection results. (a) Preprocessed result; (b) edge detection result; (c) center detection result

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Fig. 6. Circumferential correction result

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Fig. 7. Axial correction result

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Fig. 8. MSE of network model

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Fig. 9. 3D surface fitting result

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Fig. 10. Experimental process and shooting results. (a) Endoscopic image of Φ18 hole with trunking; (b) endoscope image of M18 thread hole; (c) Φ18 hole; (d) simulated defect; (e) endoscopic image of Φ18 hole

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Fig. 11. Correction and edge detection results. (a) Correction result of experiment 1; (b) contour information of experiment 1; (c) correction result of experiment 2; (d) contour information of experiment 2; (e) defect local amplification of experiment 3; (f) correction result of experiment 3; (g) contour information of experiment 3

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Table 1. Calibration block width statistics
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Table 1. Calibration block width statistics
Line number 1 2 3 4 5 6 7 8 9
After circumferential correction 37.33 37.67 37.83 38.17 38.17 38.33 38.33 38.17 37.67

Table 2. Calibration block height statistics

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Table 2. Calibration block height statistics

Correction method

Height

Mean value

Standard deviation

Line number 1

Line number 2

Line number 3

Line number 4

Line number 5

Line

number

Line number 7

Line number 8

Line number 9

Before axial correction

21.33

18.50

16.00

13.50

11.83

10.67

10.17

9.47

9.16

13.40

4.322

After axial correction

21.25

20.96

20.81

20.37

20.75

20.92

21.57

21.35

21.67

21.07

0.421

Table 3. Experimental results of different apertures
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Table 3. Experimental results of different apertures
Image Φ12 Φ16 Φ21 Φ25 Φ28 Φ32
Original images
Corrected image

Table 4. Pixel position and measurement error statistics

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Table 4. Pixel position and measurement error statistics

Parameter	Vertex coordinate	Edge length pixel distance /pixel	Mean value /pixel	Standard deviation	Unit pixel size / （mm×mm）	Measuring result /mm	Real size /mm	Error /%
Φ12	（1569，46），（1910，287），（1776，678），（1373，684），（1248，274）	665.04，667.82， 664.83，667.43， 662.13	665.45	2.05	0.0182×0.0182	12.11	12	0.92
Φ16	（1596，15），（1836，197），（1728，496），（1458，491），（1353，210）	498.78，478.87， 471.62，495.60， 483.17	485.61	10.20	0.0250×0.0250	12.14	12	1.17
Φ21	（1557，237），（1904，518），（1761，978），（1327，972），（1183，503）	768.57，734.20， 748.14，770.15， 721.16	748.44	19.10	0.0328×0.0328	24.55	25	1.80
Φ25	（1619，51），（1970，295），（1836，713），（1418，724），（1278，294）	696.66，699.10， 697.80，702.37， 692.00	697.59	3.39	0.0368×0.0368	25.67	25	2.68
Φ28	（1614，23），（1927，208），（1822，579），（1451，582），（1322，216）	593.63，605.35， 617.87，582.28， 605.05	600.84	12.04	0.0424×0.0424	25.48	25	1.92
Φ32	（1653，19），（1914，205），（1817，524），（1502，530），（1398，227）	530.96，524.76， 513.59，532.84， 516.47	523.72	7.64	0.0462×0.0462	24.20	25	3.20

Table 5. Pixel position and error statistics

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Table 5. Pixel position and error statistics

Experiment

Sample size

Mean value

of pixel

distance /pixel

Standard

deviation of

pixel distance

Unit pixel size /

（mm×mm）

Measuring

result /mm

Real size /mm

Error /%

Experiment 1

268

111.51

4.92

0.1095×0.1095

12.21

13.14

7.08

Experiment 2

479

48.43

2.42

0.1095×0.1095

5.30

5.00

6.06

Experiment 3

60.40

5.46

0.0323×0.0323

1.95

2.10

7.10

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Qiang Sheng, Jianming Zheng, Ting Chen, Xiuxiu Yang, Xianming Gao. Measurement Method of Inner Surface Size of Hole Based on Distortion Correction of Endoscopic Image[J]. Acta Optica Sinica, 2023, 43(3): 0312006

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