CHEN Fang, ZHANG Cun-ji, HAN Yan-xiang etc. Fast focus on simple images[J]. Editorial Office of Optics and Precision Engineering, 2014,22(1): 220-227 DOI: 10.3788/OPE.20142201.0220.
To quickly realize the autofocus of a simple image and further improve the efficiency of automated part fabrication
a novel fast focusing algorithm was proposed according to the characters of images with single and clear backgrounds and foregrounds. Firstly
a series of part images including their position information were acquired. Then
all variance grey span values of target edges in each image were calculated automatically and the minimum span value of the clearest image was found quickly. Finally
the position information of the clearest image was feedbacked to a hardware driving system tocomplete the autofocus.An experiment on severalparts with different shapes or materials was performed and obtained results were compared with that of the classic optimal focus function.The experimental resultson those images added with salt-and-pepper noisesdemonstrate that the new algorithm is not only more sensitive but also has stronger unimodality and stronger anti-noise ability than those of classic optimum algorithms.Moreover
its computing speed is more than 30% faster than that of the fastest absolute gradient function. It concludes that the novel algorithm is robust and can be better used for a fast focus on simple scenes.
关键词
Keywords
references
SHEN H, LI S X, GU D Y, et al.. Bearing defect inspection based on machine vision [J]. Measurement, 2012, 45(4): 719-733.
SHAHABI H H, RATNAM M M. Noncontact roughness measurement of turned parts using machine vision [J]. Int J Adv Manuf Technol, 2010, 46(1-4):275-284.
WANG X P, LIU ZH H, CHEN T N. Design of bonding quality testing system for micro device made of transparent materials [J]. Opt. Precision Eng., 2013, 21(1):69-76.(in Chinese)
LIU J W, LIANG J, LIANG X H, et al.. Industrial vision measuring system for large dimension work-pieces [J]. Opt. Precision Eng., 2010, 18(1): 126-134 . (in Chinese)
GADELMAWLA E S. Computer vision algorithms for measurement and inspection of spur gears [J]. Measurement, 2011, 44(9): 1669-1678.
PARK J B, LEE J G, LEE M K, et al.. A glass thickness measuring system using the machine vision method [J]. International Journal of Precision Engineering and Manufacturing, 2011, 12(5): 769-774.
SUN Y, DUTHALER S, NELSON B J.Auto-focusing in computer microscopy:selecting the optimal focus algorithm [J].Microscopy Research and Technique, 2004, 65(3):139-149.
VU P V, CHANDLER D M. A fast wavelet-based algorithm for global and local image sharpness estimation [J]. IEEE Signal Processing Letters, 2012, 19(7): 423-426.
ZONG G H, SUN M L, BI S S, et al.. Research on wavelet based autofocus evaluation in micro-vision [J]. Chinese Journal of Aeronautics, 2006, 19 (3): 239-246.
LI M M, WANG X S, LI J. Comparative study on the auto-focus definition function based on the image processing [J]. Infrared and Laser Engineering, 2010, 39(Supp.): 244-248.(in Chinese)
LIU Y P, JIN J, WANG Q, et al.. Phases measure of image sharpness based on quaternion wavelet [J]. Pattern Recognition Letters, 2013, 34(9):1063-1070.
DONG D, LIU R, SUN M L, et al.. Auto-focusing algorithm based on cross correlation [J]. Journal of Beijing University of Aeronautics and Astronautics, 2006, 32(3):306-310. (in Chinese)
WANG Q, SONG E M, XU X Y, et al.. Auto-focusing function for microscope image based on weighted neighborhood correlation [J]. Opt. Precision Eng., 2008, 16(1): 166-171. (in Chinese)
RUDNAYA M E, TER MORSCHE H G, MAU-
BACH J M L, et al.. A derivative-based fast autofocus method in electron microscopy [J].J Math Imaging Vis., 2012, 44(1):38-51.
ZHANG Y T, JI SH P, WANG Q F, et al.. Definition evaluation algorithm based on regional contrast [J]. Journal of Applied Optics, 2012, 33(2): 293-299. (in Chinese)
ZHANG X D, WANG J F, CHENG Y Q. Design of multifunctional and integrative analog camera system [J]. Chinese Journal of Liquid Crystals and Displays, 2009, 24(1): 116-120. (in Chinese)
ZHANG B, ZHANG G, CHENG Y Q. Design of video processor with auto-focusing [J]. Chinese Journal of Liquid Crystals and Displays, 2010, 25(3): 396-400. (in Chinese)