Effect of Focusing Status on Dimension Measurement Accuracy in Micro Measurement System Based on CCD

Abstract

This paper adopted the photoelectric micro measurement system based on CCD which was independently developed by Laboratory of Process Automatic and Detection Harbin Institute of Technology to detect dimension of the small precise parts. Under the various focusing status, it was discovered that articulation of focusing has huge effect on the measurement of measurand. According to the characteristics of measurand, we adopted the entropy function as the evaluation function of automatic focusing, developed a special software to process entropy value of the picked images, and obtained the relationship of focusing evaluation function and measurement error through a large number of experiments. The experimental result effectively verified the effect of articulation of focusing on dimension measurement.