一种红外相机径向畸变和非线性响应的校正方法。

Shu Shuangbao, Fu Yufeng, Liu Shenglin, Zhang Yuzhong, Zhang Tengda, Wu Tianqi, Gao Xinyu

Anhui Province Key Laboratory of Measuring Theory and Precision Instrument, School of Instrument Science and Opto-electronics Engineering, Hefei University of Technology, Hefei 230009, China.

Rev Sci Instrum. 2024 Mar 1;95(3). doi: 10.1063/5.0187807.

The key feature of non-contact temperature measurement provided by infrared (IR) cameras underpins their versatility. However, the accuracy of temperature measurements with IR cameras depends on imaging quality due to their non-contact nature, such as the lens, body temperature, and measurement environment. This paper addresses the correction of radial distortion and nonlinear response issues in IR cameras. To address radial distortion, we have designed a passive checkerboard calibration board specifically for infrared cameras. This board is used to calibrate the IR camera and derive the necessary camera parameters. Subsequently, these parameters are applied during the actual measurement process to rectify radial distortion effectively. Building on the radial distortion correction method mentioned above, we propose a multi-point segmented calibration approach that considers different temperature ranges and imaging regions. This method alleviates the issue of reduced temperature measurement accuracy due to variations in camera responses by computing gain and offset coefficient matrices for each temperature range. Experimental results demonstrate the effectiveness of the calibration board in correcting radial distortion in IR cameras, with a mean reprojection error of less than 0.16 pixels. Regarding the nonlinear response problem, the introduced method significantly reduces the relative error in temperature measurement. In the verification phase, spanning from 100 to 500 °C, the average relative error in temperature measurement decreases by 0.49% from 1.61% before and after correction, which highlights a substantial improvement in temperature measurement accuracy. This work gives a useful reference to improve the imaging quality and temperature measurement accuracy using infrared cameras.

红外（IR）摄像机提供的非接触式温度测量的关键特性支撑了其多功能性。然而，由于其非接触性质，红外摄像机温度测量的准确性取决于成像质量，如镜头、体温和测量环境。本文探讨了红外摄像机中的径向畸变校正和非线性响应问题。为了解决径向畸变问题，我们专门为红外摄像机设计了一个被动棋盘格校准板。该板用于校准红外摄像机并导出必要的摄像机参数。随后，在实际测量过程中应用这些参数，以有效地校正径向畸变。基于上述径向畸变校正方法，我们提出了一种考虑不同温度范围和成像区域的多点分段校准方法。该方法通过计算每个温度范围的增益和偏移系数矩阵，缓解了由于相机响应变化导致温度测量精度降低的问题。实验结果表明，该校准板在校正红外摄像机径向畸变方面是有效的，平均重投影误差小于0.16像素。对于非线性响应问题，所引入的方法显著降低了温度测量中的相对误差。在100至500°C的验证阶段，温度测量的平均相对误差从校正前的1.61%下降了0.49%，这突出了温度测量精度的大幅提高。这项工作为利用红外摄像机提高成像质量和温度测量精度提供了有益的参考。