Affiliations: [a] AnHui Province Key Laboratory of Simulation and Design for Electronic Information System, Hefei Normal University, Hefei, Anhui, China | [b] Hefei Fuhuang Agile Device Co. Ltd., Hefei, Anhui, China | [c] University of Science and Technology of China, Hefei, Anhui, China
Correspondence:
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Corresponding author: Yuan Shen, AnHui Province Key Laboratory of Simulation and Design for Electronic Information System, Hefei Normal University, Hefei, Anhui 230601, China. E-mail: shenyuan@ustc.edu.cn.
Abstract: Traditional vision measurement algorithms have many shortcomings, such as complex process, multi-parameter adjustment and the integer pixel accuracy. To solve these problems, a sub-pixel displacement measurement algorithm based on Taylor expansion is proposed. The displacement vector between adjacent frames is modeled in the first step, and then shift equation of the template image is constructed based on assumptions of constant brightness and spatial consistency. After performing a first-order Taylor series approximation, the displacement vector is obtained by least squares estimation. Finally, through iteratively updating the position of template image, displacement is rapidly extracted. In order to verify the accuracy and effectiveness of the Taylor expansion algorithm, the accuracy test of the grating ruler platform in the presence of the target and the vibration measurement experiment on vibration motor in the absence of the target are designed. Experimental results show that, compared with template matching algorithm based on normalized cross correlation, for the experiments mentioned in this paper, the proposed algorithm can control the calculation time for one frame in less than 1 ms, and achieve higher sub-pixel computation accuracy. Compared with the actual set frequency of 10.78 Hz, the measured frequency of the motor is very consistent with a relative error of 1.1%. It also verifies that the Taylor expansion algorithm proposed in this paper is a reliable and effective non-contact measurement method with important practical application value for vibration measurement.
Keywords: Vision measurement, Taylor expansion, sub-pixel accuracy, remote measurement
