Measurement of the radius of curvature of a mini spherical surface with virtual grating phase shift technique
Measurement of the radius of curvature of a mini spherical surface with virtual grating phase shift technique
复制标题
DOI：
10.1117/12.870686
复制
发表时间：
2010-11
期刊：
影响因子：
--
通讯作者：
Yongxiang Xu
中科院分区：
文献类型：
--
作者：
Yongxiang Xu
从球面上看，小直径光学元件在许多领域都有广泛的应用。曲率半径(ROC)是一个重要参数，它决定了它们的光学特性。为了测量微小球面的ROC，采用了虚拟光栅相移技术(VGPT)，拍摄了静态显微载波干涉图。利用计算机产生了四个虚拟光栅，它们的参考频率与测试干涉图的载波频率相同，它们的调制相位分别为0、π/2、π和3π/2。通过将测试干涉图分别与四个虚栅在强度上相乘，得到四幅莫尔条纹图像。通过傅里叶变换和低通滤波，得到一组四幅无载波相移条纹图像。最后，应用四步相移算法和最小二乘法(LSF)，得到被测球面的ROC。计算结果与标称值和Zygo干涉仪的测量结果吻合较好。这表明采用VGPT测量微小球面的ROC是可行的，且具有较高的精度。
Spherically optical components of small diameters have found wide applications in many fields. Radius of curvature (ROC) is an important parameter as it determines their optical characteristics. For measuring the ROC of a mini spherical surface, a static microscopic carrier interferogram is taken, and virtual grating phase shift technique (VGPT) is adopted in this paper. By using the computer, four virtual gratings are generated, their reference frequency being the same as the carrier frequency of the test interferogram, and their modulation phases being 0, π/2, π and 3π/2, respectively. By multiplying the test interferogram separately with the four virtual gratings in intensity, four moiré fringe images are obtained. By applying Furrier transform and low pass filtering, a set of four carrier-free phase shift fringe images are obtained. And finally by applying four step phase shifting algorithm and least square fitting (LSF), the ROC of the test spherical surface is obtained. Furthermore, the result agrees well with its nominal value and measurement result by Zygo interferometer. This indicates that adopting VGPT for measuring ROCs of mini spherical surfaces is practicable and has relatively a high accuracy.