移动特征靶标的摄像机径向畸变标定

针对成像测量系统中镜头径向畸变影响测量精度的问题，提出了一种基于物面移动同心圆特征靶标的径向畸变标定方法。该方法先将固定在二维精密平台上的同心圆靶标置于垂直物面的特定位置，然后采集靶标图像，同时用最小二乘法以拟合得到的圆直径为条件，按一定方式移动特征靶标，直到拟合值达到极值或者在一定误差范围内。记录该幅图像，则其拟合得到的圆心坐标便是畸变中心，同时利用该幅图像，根据等差值半径和摄像机成像模型的半径的成像关系求出其畸变多项式系数。为提高特征靶标的移动效率，提出了坐标轮换最优化移动的方案。实验结果表明，该方法对畸变中心的标定精度可达0.6 pixel,畸变多项式系数有效数字重复误差小于0.02,并可实现两者的一靶标定,且利用该法获得的参数能实现对畸变图像的准确校正。

Abstract

In order to reduce the measurement error caused by camera radial distortion in measurement system based on image, a new distortion calibration method is designed, resorting to characteristic concentric circles target. A character target rode on a two-dimensional fine platform is situated in a known position of the object side which is vertical to the optical axis, then the target images are collected and processed. A least square arithmetic is introduced to compute the fitting radius according to which the characteristic target is moved in a scheduled mode until the radius is maxim or in the demanded range. At the very time the center of the concentric circles is the camera distortion center, the coefficients of the distortion polynomial are gotten recurring to relation of arithmetical radius and imaging model radius of the camera. To find the distortion center coordinate rapidly, a coordinate alternating optimization arithmetic is applied. Experimental results show that the precision of the camera radial distortion center location demarcating can reach 0.6 pixel, and the repeated error of significant figures for polynomial coefficients is less than 0.02, and all can be realized with one character target. The distorted image can be corrected perfectly.

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