Acta Metrologica Sinica  2023, Vol. 44 Issue (4): 521-526    DOI: 10.3969/j.issn.1000-1158.2023.04.05
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Auto-focusing Technology in Perpendicular Length Measurement of Video Measuring Machine
CHE Yi-feng1,YANG Guo-shun2,CHEN Li-guo1
1. School of Mechanical and Electrical Engineering, Soochow University, Suzhou, Jiangsu 215137, China
2. Aerospace Engineering Equipment Suzhou Co. Ltd, Suzhou, Jiangsu 215103, China
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Abstract  The higher the auto-focusing accuracy is, the smaller the perpendicular length measurement error of video measuring machine would be. The improved Tenengrad gradient evaluation function is selected by comparing the performance indexes of definition evaluation function.The full window is selected as the focus window. A search strategy combining rough and fine focus is proposed. In rough focus, mountain climbing search algorithm combined with binary search algorithm is used. And Gaussian curve fitting method combined with global search algorithm is used in fine focus. The experimental results show that the auto-focusing algorithm has good robustness and high accuracy which can reach 5μm (1/20 depth of field), and the average focusing time is 10 seconds which can meet the real-time requirements.
Key wordsmetrology      video measuring machine      perpendicular length measurement      auto-focusing technology      definition evaluation function      focus window      search strategy     
Received: 09 February 2022      Published: 18 April 2023
PACS:  TB92  
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CHE Yi-feng
YANG Guo-shun
CHEN Li-guo
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CHE Yi-feng,YANG Guo-shun,CHEN Li-guo. Auto-focusing Technology in Perpendicular Length Measurement of Video Measuring Machine[J]. Acta Metrologica Sinica, 2023, 44(4): 521-526.
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http://jlxb.china-csm.org:81/Jwk_jlxb/EN/10.3969/j.issn.1000-1158.2023.04.05     OR     http://jlxb.china-csm.org:81/Jwk_jlxb/EN/Y2023/V44/I4/521
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