Wang Yuwei, Chen Xiangcheng, Tao Jiayuan, Wang Keyi, Ma Mengchao
Appl Opt. 2016 Oct 1;55(28):7964-7971. doi: 10.1364/AO.55.007964.
For conventional camera calibration methods, well-focused images are necessary to detect features accurately. However, this requirement causes practical inconveniences to image acquisition for long- and short-distance photogrammetry. In this study, three active phase-shift circular grating (PCG) arrays are used as calibration patterns. The PCGs' centers are regarded as feature points that can be accurately extracted by ellipse fitting of 2π-phase points even though patterns are substantially blurred. In the experiments, Gaussian filters are utilized to blur pattern images, and different standard deviations are set for different fuzzy degrees. Pattern images with different defocusing degrees are also captured. The period and number of PCGs and noise are considered. Experimental results indicate that our method is accurate, reliable, and insensitive to image defocusing.
对于传统的相机校准方法，需要清晰聚焦的图像才能准确检测特征。然而，这一要求给长距离和短距离摄影测量的图像采集带来了实际不便。在本研究中，三个有源相移圆形光栅（PCG）阵列被用作校准图案。即使图案严重模糊，PCG的中心也被视为可以通过对2π相位点进行椭圆拟合来准确提取的特征点。在实验中，利用高斯滤波器对图案图像进行模糊处理，并针对不同的模糊程度设置不同的标准差。还采集了具有不同散焦程度的图案图像。考虑了PCG的周期、数量和噪声。实验结果表明，我们的方法准确、可靠，并且对图像散焦不敏感。
