等光程干涉仪中参考镜楔角最优补偿方式研究

Optimal compensation methods of wedge angle of reference mirror in equal optical path interferometers

在测量多表面平行样品时,多面干涉会影响测量结果。为了能改善多面干涉问题,介绍了等光程干涉仪,并研究了参考镜楔角的最佳补偿方式。在等光程干涉仪中,由于参考镜和分光镜的楔角和倾角的存在,测量结果中会带有回程误差。根据参考镜楔角的不同情况采用了不同的补偿,理论分析并确定了各种补偿的放置方式和补偿量,同时研究了倾角和楔角的大小对于要被遮拦光束高度和像方数值孔径NA的影响。再利用Zemax进行不同补偿方式下的干涉仪仿真,并根据仿真得到的干涉图PV值分析回程误差的大小。分析表明:选用最佳补偿方式,参考镜楔角为1′,回程误差优于0.003个波长。

When measuring multi-surface parallel samples, the multi-surface interference can affect the measurement results. To improve the multi-surface interference problem, an equal optical path interferometer was introduced and the optimal method to compensate for the wedge angle of reference mirror was studied. In an equal optical path interferometer, due to the existence of wedge angle and inclination angle of the reference mirror and beam splitter mirror, the retrace errors would occur in the measurement results. The different compensations were applied depending on the different cases of reference mirror wedge angle. The placement and compensation amount of the various compensations were theoretically analyzed and determined, and the effect of the size of inclination angle and wedge angle on the height of the beam to be blocked and the image square NA was studied. The interferometer simulations were then carried out using Zemax with different compensation methods, and the magnitude of the retrace error was analyzed according to the PV values of the interferograms obtained from the simulations. The analysis shows that the optimal compensation method is chosen, with a wedge angle of reference mirror of 1′ and the retrace error is better than 0.003 wavelengths.