[1] Chen Y B[M]. Modern laser welding technology, 1-4(2005).

[2] You D Y, Gao X D. Studies and prospect of laser welding technology[J]. Welding Technology, 37, 5-9(2008).

[3] Xu E J, Gao X D, Xiao Z L et al. Sensing methods of seam tracking in laser welding process[J]. Electric Welding Machine, 46, 28-35(2016).

[4] Qi X B. State-of-arts of visual sensing technology to monitor laser welding process[J]. Transactions of the China Welding Instruction, 108-112, 118(2008).

[5] Xu Y, Fang G, Chen S et al. Real-time image processing for vision-based weld seam tracking in robotic GMAW[J]. The International Journal of Advanced Manufacturing Technology, 73, 1413-1425(2014). http://link.springer.com/article/10.1007/s00170-014-5925-1

[6] Chen H, Liu K, Xing G et al. A robust visual servo control system for narrow seam double head welding robot[J]. The International Journal of Advanced Manufacturing Technology, 71, 1849-1860(2014). http://link.springer.com/article/10.1007/s00170-013-5593-6

[7] Chen Y B, Li L Q, Chen F D et al. Application and prospect of image processing in welding[J]. Materials Science & Technology, 11, 106-112(2003).

[8] Gao X, Chen Y. Detection of micro gap weld using magneto-optical imaging during laser welding[J]. The International Journal of Advanced Manufacturing Technology, 73, 23-33(2014). http://link.springer.com/article/10.1007/s00170-014-5811-x

[9] Shao W J, Huang Y, Zhang Y. A novel weld seam detection method for space weld seam of narrow butt joint in laser welding[J]. Optics & Laser Technology, 99, 39-51(2018). http://adsabs.harvard.edu/abs/2018OptLT..99...39S

[10] Wang P J, Shao W J, Gong S H et al. High-precision measurement of weld seam based on narrow depth of field lens in laser welding[J]. Science and Technology of Welding and Joining, 21, 267-274(2016). http://www.tandfonline.com/doi/abs/10.1080/13621718.2015.1104094

[11] Qu Z G. Chong A Y B, Chacon J L F, et al. Study on the laser-based weld surface flaw identification system employing wavelet analysis methodology[J]. Research in Nondestructive Evaluation, 27, 137-154(2016).

[12] You D Y, Gao X D, Katayama S. Review of laser welding monitoring[J]. Science and Technology of Welding and Joining, 19, 181-201(2014). http://www.tandfonline.com/doi/abs/10.1179/1362171813Y.0000000180

[13] Zhao J, Lin S B. Introduction to laser sensors for automated welding[J]. Electric Welding Machine, 40, 1-5(2010).

[14] Wang H, Wang X H. An improved adaptive median filter based on noises detection[J]. Journal of China University of Metrology, 22, 382-385(2011).

[15] Papoulis A, Pillai S U. Probability,random variables, and stochastic processes[M]. 3 ^rd ed. New York: McGraw-Hill, Inc. (1991).