Magneto-Optical Imaging Restoration Method for Damaged Characters with Orthogonal Excitation

Fei Gao; Xueyong Li; Shuo Zhang; Changhou Lu

doi:10.3788/LOP220483

Laser & Optoelectronics Progress, Volume. 60, Issue 10, 1011003(2023)

Magneto-Optical Imaging Restoration Method for Damaged Characters with Orthogonal Excitation

Fei Gao^1,2, Xueyong Li^1,2、*, Shuo Zhang^1,2, and Changhou Lu^1,2

¹Key Laboratory of High Efficiency and Clean Mechanical Manufacture, Ministry of Education, School of Mechanical Engineering, Shandong University, Jinan 250061, Shandong , China

²National Demonstration Center for Experimental Mechanical Engineering Education, Shandong University, Jinan 250061, Shandong , China

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Figures & Tables(11)

Fig. 1. Magnetic field change at characters. (a) Character magnetic coupling model; (b) x-axis direction; (c) y-axis direction

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Fig. 2. Principle of magneto-optical imaging

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Fig. 3. Magnetic field distribution in the iron core

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Fig. 4. Results of simulation. (a) Three-dimensional finite element model; (b) plot of magnetic induction field; (c) horizontal excitation; (d) vertical excitation

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Fig. 5. Magneto-optical imaging recovery system for damaged characters

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Fig. 6. Enhancement result of different algorithms. (a) LHE; (b) BPDHE; (c) CLAHE

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Fig. 7. Grayscale curve obtained by different algorithms. (a) Grayscale value of horizontal excitation 220th row pixel; (b) grayscale value of vertical excitation 140th column pixel

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Fig. 8. Magncto-optical imaging result of damaged characters. (a) Character E; (b) character F; (c) character H; (d) character D

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Fig. 9. Result of different fusion algorithms. (a) Proposed method; (b) average weighting; (c) wavelet transform

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Table 1. Results of magneto-optical imaging appearances for different characters
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Table 1. Results of magneto-optical imaging appearances for different characters
Before grinding After grinding Character Horizontal excitation Vertical excitation
“E”
“F”
“H”
“D”

Table 2. Objective evaluation result of the three fusion algorithms

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Table 2. Objective evaluation result of the three fusion algorithms

Fusion character	Information entropy			Variance
Fusion character	method Proposed	Average weighting	Wavelet transform	method Proposed	Average weighting	Wavelet transform
“E”	7.1993	6.9471	6.9449	1387.0	933.18	1011.40
“F”	7.0772	6.8333	6.8460	1246.4	820.89	900.48
“H” “D”	7.2358	6.9729	6.9172	1509.4	968.98	898.36
“H” “D”	7.1766	6.9479	6.9603	1323.0	926.28	978.92

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Fei Gao, Xueyong Li, Shuo Zhang, Changhou Lu. Magneto-Optical Imaging Restoration Method for Damaged Characters with Orthogonal Excitation[J]. Laser & Optoelectronics Progress, 2023, 60(10): 1011003

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