To improve the positioning precision of the projected point for a spherical target center
the imaging theory of spherical target and positioning method of the spherical target center were investigated. By establishing the imaging model of spherical target and combining spatial analytic geometry theory
the perspective projection properties of spherical target were verified and an exact expression for the position of projection point of sphere center was deduced. Finally
by combining with an actual measurement
the precision positioning method for the projected point of spherical target center was given. Furthermore
an error model for projected spherical central distortion was established on the basis of the simulation experiment
and corresponding effect factors were analyzed. With the use of a ceramic standard ball
calibration experiments of the pose parameters of a vision system were implemented. It shows that the re-projected error of the spherical target center from the proposed method has less 36% averagely than that of the traditional method
and the stability of the pose parameters is increased by 40% relatively. These results verify that the proposed positioning method for the projected point of spherical target center has high precision and robustness
and it can be widely used in visual calibration or measurement based on spherical targets.
ZHANG Y P, HE T, WEN CH J, et al. Applications and research of machine vision in industrial measurement [J]. Opt. Precision Eng., 2001, 9(4): 324-329.(in Chinese)
ZHAO Y T, SUN J H, CHEN X, et al. Camera calibration from geometric feature of spheres[J]. Journal of Beijing University of Aeronautics and Astronautics, 2014, 40(4): 558-563.(in Chinese)
HUANG F SH, QIAN H F. Camera calibration technology driven by three-coordinate measuring machine [J]. Opt. Precision Eng., 2010, 18(4): 952-957. (in Chinese)
SHEN E, HORNSEY R. Multi-camera network calibration with a non-planar target[J]. IEEE Sensors Journal, 2011, 1(10): 2356-2364.
ZHANG H, WONG K Y, ZHANG G. Camera calibration from images of spheres[J]. Pattern Analysis & Machine Intelligence IEEE Transactions on, 2007, 29(3): 499-503.
LIU SH G, YU F, HAN ZH H. Collision detection of virtual coordinate measuring machine based on OpenCasCade [J]. Nanotechnology and Precision Engineering, 2016: 10.13494/j.npe.20150133.(in Chinese)
ZHAO Y J, WANG J L, MA X H, et al. Coordinate measuring machine intelligence technology[J]. Acta Metrologica Sinica, 2001, 22(3): 164-167. (in Chinese)
WEI ZH ZH, ZHANG G J. A distortion error model of the perspective projection of ellipse center and its simulation[J]. Chinese Journal of Scientific Instrument, 2003, 24(2): 160-164. (in Chinese)
GU F F, ZHAO H, BU P H, et al. Analysis and correction of projection error of camera calibration ball[J]. Acta Optica Sinica, 2012(12): 209-215. (in Chinese)
LIU Y, WANG W H, LI ZH G, et al. Parameter measurement system of PCR chip based on sub-pixel edge detection[J]. Instrument Technique and Sensor, 2014(2): 65-67. (in Chinese)
ZHANG H, DA F P, XING D K. Algorithm of center location of ellipse in optical measurement[J]. Journal of Applied Optic, 2008, 29(6): 905-911. (in Chinese)
LIU SH G, JIANG ZH ZH, DONG Y H, et al. Self-calibration of probe tip center for 3D vision coordinate measuring system in portable light pen[J]. Opt. Precision Eng., 2014, 22(2): 259-265. (in Chinese)