一种基于单目定焦相机免标定的尺寸测量方法
周明聪,樊庆文*,裴宏亮,熊良胤,董香平,孙峰辉
(四川大学 机械工程学院,四川 成都 610065)
摘要:机器视觉以其非接触式测量、精度高、实时性好、成本低等优点,越来越广泛的被应用于工件和产品的尺寸测量中,其中利用单目相机测量零件的几何尺寸是机器视觉的重要部分。在利用单目相机测量时,当被测物在相机光轴方向移动后需要重新对焦,获得被测物的清晰图像,并重新标定相机参数,再根据像素坐标计算被测物体尺寸。针对单目定焦相机测量时需要频繁对焦标定的问题,提出了一种直接根据相机对焦环刻度值计算被测物体尺寸的方法。在不同物距下,调整相机对焦环获得清晰图像,并记录对焦环刻度值t,计算不同物距下物体像素尺寸与实际尺寸的比值k,拟合t值与比值k的函数关系,不需要重新标定相机,即根据像素尺寸直接进行物体尺寸测量。实验表明,该测量方法操作简单,避免了复杂的相机标定,相对误差小于2%。具有一定的实用价值。
关键词:单目视觉;尺寸测量;相机标定;曲线拟合 
中图分类号:TP242 文献标志码:A doi:10.3969/j.issn.1006-0316.2022.04.010
文章编号:1006-0316 (2022) 04-0057-06
A Calibration-free Size Measurement Method Based on Monocular Cameras
ZHOU Mingcong,FAN Qingwen,PEI Hongliang,XIONG Liangyin,DONG Xiangping,SUN Fenghui
( School of Mechanical Engineering, Sichuan University, Chengdu 610065, China )
Abstract: Machine vision is widely used in the dimensional measurement of workpieces and products for the advantages of non-contact measurement, high precision, good real-time performance and low cost. And measuring the geometric dimension of the parts with monocular cameras is an important part of machine vision. In the measurement with a monocular camera, when the measured object moves in the direction of the camera optical axis, it’s necessary to refocus to obtain a clear image of the object, recalibrate the camera parameters, and then calculate the size of the measured object according to the pixel coordinates. For the problem of frequent focus and calibration in the measurement with monocular cameras, a method to calculate the size of the measured object directly according to the scale value of the camera's focus ring is proposed. At different object distances, the focus ring of the camera is adjusted to obtain a clear image, the scale value t of the focus ring is recorded, the ratio k between the pixel size and the actual size of the object are calculated , and the functional relationship between the t value and the ratio k is fitted. The size of the object is calculated directly according to the pixel size without the recalibration of the camera. The experiment shows that the measurement method is simple without complex camera calibration, and the relative error is less than 2%, which provides certain practical value.
Key words:monocular vision;size measurement;camera calibration;curve fitting
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收稿日期:2021-09-09
基金项目:四川省苗子工程项目(2020JDRC0029);四川省重点研发项目(22ZDYF2983)
作者简介:周明聪(1995-),男,湖北随州人,硕士研究生,主要研究方向为机器视觉,E-mail:1594678615@qq.com。*通讯作者:樊庆文(1966-),男,山东济宁人,研究员,主要研究方向为人机工程、机电工程,E-mail:fanqingwen@scu.edu.cn。
 

 

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