相机标定的外界影响因素分析

针对相机标定结果易受外界因素干扰的问题，为了提高标定准确度，利用已有的摄像机针孔成像模型，采用自适应角点检测算法提取靶标图像中的特征点，标定结果以重投影横纵像素误差的平均值作为性能指标，对均匀光源的照度、标定图片数量以及标定靶标上棋盘格尺寸3个影响因子做了相应的分组对比实验。研究结果表明，选择亮度高的光源提升标定准确度达到38%以上；特征点数目156个时，仅需18张～22张标定图片；相对较小的棋盘格尺寸可以使得标定准确度提高50%。以上结果充分说明了光源、图片数量和棋盘格尺寸对于提高相机标定准确度具有重要意义。

Analysis of external influence factors in camera calibration

As camera calibration results can be influenced by external factors easily, to improve the accuracy of calibration results, the pin-hole camera imaging model was utilized, and the adaptive corner detection method was adopted to pick up the feature points in calibration images, then the mean value of re-projection error in the coordinates was introduced as the performance index, a series of experiments were designed correspondingly for the three external factors including the number of image, the luminance of light and the size of square in calibration board. The experiments results indicate that choosing brighter light source can improve the calibration accuracy above 38%; given 156 points feature, only 18~22 calibration pictures are needed, and also, smaller square size can increase the results- accuracy about 50%. All mentioned above show the importance of light source, number of pictures and square size in camera calibration accuracy-improving.