[1] [1] QIAO N Sh, YE Y T, MO Ch H, et al. Method for the detection of concentric circles of photoelectric image of circular hole in printed circuit board[J]. Acta Optica Sninica,2010,30(1):75-78(in Chin-ese).

[2] [2] XIE G W, ZHONG Zh Zh, ZHONG Sh K, et al. Research on position-ing method of circular mark in PCB based on machine vision[J]. Computer Knowledge and Technolgy,2013,9(32):7340-7344(in Chinese).

[3] [3] DONG M. Object multi-mark recognition algorithm based on machine learning and image processing[J]. Computer & Digital Engineering,2016,44(12):2488-2492(in Chinese).

[4] [4] WANG M H, CHEN J B. A fast and robust template matching algorithm[J]. Industrial Control Computer,2019,32(3):45-48(in Chin-ese).

[5] [5] DING X Y, WANG T. Image template matching algorithm based on cross-check ORB and MCC[J]. Journal of Electronic Measurement and Instrument,2019,33(5):39-45(in Chinese).

[6] [6] BAI C B, QI Ch, SONG F M, et al. Fast detection of circular pcb mark using Hough transform[J]. Opto-Electronic Engineering,2005,32(9): 75-78(in Chinese).

[7] [7] XIONG G J, MA Sh Y, LIU R Zh. Fast precise positioning of circular mark in PCB inspection[J]. Computer Engineering,2012,38(11):211-216(in Chinese).

[8] [8] XIAO J H, XIANG X J. Design of measurement system for steel ruler end face based on Halcon[J]. Journal of Zhejiang University of Science and Technology,2018,30(6):488-495(in Chinese).

[9] [9] GONG P L, LV X Sh. Skills on bar code recognition based on halcon[J]. Computer and Modernization,2013,1(4):73-76(in Chinese).

[10] [10] LI X, JIANG M Sh. A comparison of sharpness functions based on microscopes[J]. Optical Instruments,2018,40(1):28-38 (in Ch-inese).

[11] [11] GAO Sh Sh, WANG Y J, JIN W Q, et al. Objective image sharpness metric based on perceptual contrast[J]. Optical Techniques,2015,41(5):396-399(in Chinese).

[12] [12] BRAGA-NETO U, GOUTSIAS J. Object-based image analysis using multiscale connectivity[J]. IEEE Transactions on Pattern Analysis and Machine Intelligence,2005,27(6):892-907.

[13] [13] MA Y F. Research on image processing technology applied to infrared and lidar compound system[D]. Shanghai: Shanghai Jiao Tong University,2012: 11-36(in Chinese).

[14] [14] ZENG J Q, WANG J, CHEN Y, et al. Multi-color-image compression and encryption by using discrete wavelet transform in Fresnel transform domain[J]. Laser Technology, 2018, 42(6): 733-738(in Chinese).

[15] [15] ZHOU Y T. Multi-sensor image fusion[C]//Proceedings of IEEE 2001 International Conference on Image Processing. New York,USA:IEEE,2001:846-849.

[16] [16] LI Y, QIAO B, LU Y P. Circle fitting algorithm based on clustering[J]. Computer Applications, 2013, 33(22) :206-208(in Chin-ese)

[17] [17] SONKA M, HLAVAC V, CENG R B D M. Image processing ,ana-lysis and machine vision[M]. Belmont,USA:Thomson Learning,2008: 685-686.

[18] [18] FU Z M, WANG J W, ZHANG S H, et al. Workpiece size and defect detection in metal forming based on HALCON[J]. Tool Techno-logy, 2019,53(2):134-137 (in Chinese).

[19] [19] SHI Y L, MEI L L. Edge detection technologies research based on PCB locating hole[J]. Printed Circuit Information,2012(11):53-57(in Chinese).

[20] [20] XU Y L, MA Y. An edge detection algorithm based on improved canny operator[J]. Journal of Fujian Computer,2019,35(5):5-7(in Chinese).

[21] [21] CHEN M J, FANG Y M, CHEN J. Fitting of circular curve based on least square method and iterative method[J]. Science of Surveying and Mapping,2016,41(1):194-197(in Chinese).