Fig. 1. Schematic diagram of OCT welding depth monitoring system

Fig. 2. Experimental setup. (a) Laser welding system; (b) SD-OCT system

Fig. 3. Spectral interferogram and axial depth diagram. (a) Spectral interferogram; (b) axial depth diagram

Fig. 4. OCT welding depth measurement result

Fig. 5. Micrograph of weld seam. (a) Top surface; (b) longitudinal section; (c) actual welding depth curve

Fig. 6. Comparison of OCT welding depth measurement result with longitudinal cross section

Fig. 7. Interaction of OCT measuring beam with keyhole^[29]. (a) Keyhole bottom; (b) multi-reflection inside keyhole; (c) keyhole wall

Fig. 8. Measurement results of two groups of experiments. (a) Group 1; (b) group 2

Fig. 9. Local comparison between welding depth extracted by percentile filter and actual welding depth under different p

Fig. 10. Global comparison of welding depth extracted by percentile filter and actual welding depthat p=96

Fig. 11. Influencing factors of average error. (a) Relationship between average error and percentile; (b) relationship between average error and window length; (c) relationship among average error, percentile and window length

Fig. 12. Weld depth extraction result based on LOF and maximum filter. (a) Detection result; (B) extraction result

Fig. 13. Average error comparison of method based on LOF and maximum filter with percentile filter algorithm

Fig. 14. Detection, extraction and average error comparison results. (a)(d) Detection result; (b)(e) extraction result; (c)(f) average error