针对传统相机标定方法精度和灵活性不高的缺点,提出了一种基于相位标靶的相机标定方法。该方法首先将液晶显示屏作为相位标靶(LCD)产生红、蓝正交的正弦条纹图案,通过傅里叶变换和空间相位展开算法从一幅条纹图中得到水平和垂直两个方向上的展开相位图;然后将相位标靶任意摆放在相机景深范围内的几个不同的位置,建立世界坐标与像素坐标之间的精确的映射关系;最后标定相机的内部参数,并利用重投影误差评价标定结果的精度。实验结果表明:所提方法在每个标靶位置只需采集一幅条纹图即可得到两个方向的展开相位图,与现有方法相比简化了标定步骤,并且重投影误差仅为0.042 pixel。

To overcome the drawbacks of low accuracy and flexibility of the traditional camera calibration methods, a camera calibration method based on the phase target is proposed. First, the liquid crystal display (LCD) is used as the phase target to generate the orthogonal sinusoidal fringe patterns in red and blue channels. Only one fringe pattern is used to obtain the unwrapped phase map in both the horizontal and vertical directions via the Fourier transform and the spatial phase unwrapping algorithm. Then, the phase target is arbitrarily placed at several different positions within the depth field of this camera to establish an accurate mapping relationship between the world coordinate and the pixel coordinate. Finally, the intrinsic parameters of this camera are calibrated and the accuracy of calibration results is evaluated by means of the re-projection errors. The experimental results show that we can obtain the unwrapping phase map of two directions at each phase target position by collecting only one fringe pattern with the proposed method. Compared with those in the existing methods, not only the calibration steps in the proposed method are simpler, but also the re-projection error is only 0.042 pixel.