Assa A, Betser A A, Politch J
Appl Opt. 1977 Sep 1;16(9):2504-13. doi: 10.1364/AO.16.002504.
A diffraction grating shearing interferometer is presented which, depending on the recording procedure, can be used to measure directly the slopes and curvatures of specularly reflecting flexed plates. Three system arrangements are described: two for slope measurement and one for curvature. One slope arrangement yields results in real time but, in general, does not compensate for initial model curvature. The second requires an additional spatial filtering step but does compensate for the initial curvature. A diffraction theory approach is used to arrive at expressions for the complex field amplitude of the light at the output plane. This leads to expressions for the fringe values. Experimental results for three types of model are also presented. Errors of 2-4% were found for the various system arrangements. In addition, an analytical expression is derived and verified experimentally, which shows that when the system is used for measuring slope, the curvature of the model limits the measuring sensitivity. The theoretical analysis shows that this is a fundamental property of grating interferometers in general. This property is then exploited as the basis of the curvature measuring technique.
本文介绍了一种衍射光栅剪切干涉仪，根据记录过程，它可用于直接测量镜面反射挠曲板的斜率和曲率。文中描述了三种系统配置：两种用于斜率测量，一种用于曲率测量。一种斜率测量配置可实时得出结果，但一般来说，它不能补偿初始模型曲率。第二种配置需要额外的空间滤波步骤，但能补偿初始曲率。采用衍射理论方法得出输出平面处光的复场振幅表达式，进而得到条纹值的表达式。文中还给出了三种模型的实验结果。发现不同系统配置的误差为2 - 4%。此外，推导并通过实验验证了一个解析表达式，该表达式表明当系统用于测量斜率时，模型的曲率会限制测量灵敏度。理论分析表明，这一般是光栅干涉仪的一个基本特性。然后利用这一特性作为曲率测量技术的基础。
