An improved clarity evaluation function for precise focusing and its application on vision measuring machine

Article type: Research Article

Authors: Zou, Huadong^* | Jia, Ruiqing

Affiliations: School of Mechanical Electronic and Information Engineering, China University of Mining and Technology, Beijing, China

Correspondence: [*] Corresponding author: Huadong Zou, School of Mechanical Electronic and Information Engineering, China University of Mining and Technology, Beijing, China. E-mail: zou_huadong@163.com.

Abstract: Four clarity evaluation functions are introduced. Their merits and deficits in sensitivity and speed were tested by using four photos with different clarity. Based on the test, a new evaluation function was proposed, which is adopted by Fourier spectrum evaluation function. Test results show that the new function has the better sensitivity on clarity evaluation compared to the Fourier spectrum evaluation function. This new function was applied to the vision measuring machine for clarity evaluation. Gauss curve fitting method is used to get the exact focusing position after acquiring the evaluation value of each position. It’s shown that the new evaluation function has good performance on machine’s auto-focusing action. It’s suitable to be used for the precise focusing situation.

Keywords: Precise focusing, clarity evaluation function, fourier spectrum function, gauss curve fitting

DOI: 10.3233/JCM-180802

Journal: Journal of Computational Methods in Sciences and Engineering, vol. 18, no. 2, pp. 469-478, 2018