Li Peng, Tang Feng, Wang Xiangzhao
Appl Opt. 2022 Jan 1;61(1):1-9. doi: 10.1364/AO.441092.
Lateral shearing based on the grating is one of the classical configurations when measuring the wavefront aberration of optical systems such as the lithographic projection lens. Because the wavefront under test is spherical, but a detector surface is a plane, the coordinate of the wavefront surface will be distorted on the detector surface. As the numerical aperture (NA) of the optics under test increases, the shear ratios at different positions within the shearing region are significantly different due to the coordinate distortion. Therefore, the reconstructed wavefront from the traditional lateral-shearing reconstruction method designed for a fixed shearing ratio will contain a non-negligible error. In this work, we use the ray-tracing method to calculate the shearing ratio distribution in the shearing region and propose a compensated differential Zernike fitting method to solve the coordinate distortion and shearing ratio variation problem. The relative error of the uncompensated result will increase as the NA increases. This error is around 1% for a 0.1 NA, 10% for a 0.3 NA, and over 100% for an NA above 0.7. Compensation for the shearing ratio variation is necessary when the NA is larger than 0.3. The proposed method has been validated by simulations and experiments.
基于光栅的横向剪切是测量光刻投影透镜等光学系统波前像差时的经典配置之一。由于被测波前是球面的，而探测器表面是平面的，波前表面的坐标在探测器表面会发生畸变。随着被测光学系统的数值孔径（NA）增大，由于坐标畸变，剪切区域内不同位置的剪切比会有显著差异。因此，采用为固定剪切比设计的传统横向剪切重建方法重建的波前将包含不可忽略的误差。在这项工作中，我们使用光线追迹方法计算剪切区域内的剪切比分布，并提出一种补偿差分泽尼克拟合方法来解决坐标畸变和剪切比变化问题。未补偿结果的相对误差会随着NA的增大而增加。对于0.1的NA，该误差约为1%；对于0.3的NA，为10%；对于大于0.7的NA，则超过100%。当NA大于0.3时，有必要对剪切比变化进行补偿。所提出的方法已通过模拟和实验验证。
