光学系统是在线高精度视觉测量系统的重要模块,其中远心镜头的引入导致对焦不准、系统复杂度和成本大大提高等问题.文章以实验室搭建的视觉测量系统为平台,采用平行背光源,分别用远心镜头和普通镜头对数控铣刀进行了直径测量.根据清晰度比率、灵敏度、局部极值因子等评价指标对两类镜头环境下的Tenengrad 函数特性进行对比分析.结果显示,非远心镜头在灵敏度、分辨率和鲁棒性更占优势,高达35%左右,而远心镜头具有更好的曲线性,超出30%左右.考虑到该在线测量系统应用于复杂工业环境中,应选择分辨率、灵敏度和鲁棒性均占优势,且成本更低的非远心镜头.%The optical system is an important module of the online high-precision visual measurement sys-tem,in which the introduction of telecentric lens leads to problems such as inaccurate focusing, increased system complexity and greatly increased cost. In this paper,the visual measurement system built in the labo-ratory is introduced as a platform,and the diameter of the NC milling cutter is measured by using the parallel backlight. According to the evaluation indexes such as definition ratio, sensitivity and local extremum fac-tor,the Tenengrad function characteristics of two kinds of lens environment are compared and analyzed. The results show that telecentric lens has the advantages of sensitivity, resolution and robustness, which is as high as 35%,while the telecentric lens has better curve,which is more than 30%.Considering that the on-line measurement system is applied in complex industrial environment,the non-telecentric lens with the ad-vantages of high resolution,sensitivity and robustness and low cost is selected.
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