Fundamental aspects of resolution and precision in vertical scanning white-light interferometry
Fundamental aspects of resolution and precision in vertical scanning white-light interferometry
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DOI：
10.1088/2051-672x/4/2/024004
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发表时间：
2016-06-01
影响因子：
2.7
通讯作者：
Xie, Weichang
中科院分区：
文献类型：
--
作者：
Lehmann, Peter;Tereschenko, Stanislav;Xie, Weichang
本文讨论了垂直扫描白光干涉术（SWLI）的高度分辨率和横向分辨率。相对于干涉高度分辨率，相移干涉（PSI）被认为是提供最高的精度。然而，如果考虑SWLI相位评估和PSI算法的噪声依赖性，则可以显示SWLI测量更精确。相对于横向分辨率，SWLI信号的相干峰位置的确定似乎导致更好的结果相比，基于相位的干涉测量。这可以归因于众所周知的蝙蝠翼效应。由于蝙蝠翼是应用非线性滤波器（例如中值滤波器）的非线性效应，因此其显著减少它们。如果在条纹阶数确定和相位评估之前应用滤波，则可以在不改变相位的模数的情况下消除被称为鬼阶的伪影的数量。最后，我们讨论了测量的高度值的依赖表面坡度。我们表明，在干涉显微镜有更多的刚性相比，从物镜透镜的数值孔径所产生的最大表面倾斜角的额外的限制。因此，即使干涉信号的调制深度对于信号分析来说仍然足够好，测量精度也会在更陡的侧面的斜率变化处下降。
We discuss the height and lateral resolution that can be achieved in vertical scanning white-light interferometry (SWLI). With respect to interferometric height resolution, phase-shifting interferometry (PSI) is assumed to provide the highest accuracy. However, if the noise dependence of SWLI phase evaluation and PSI algorithms is considered, SWLI measurements can be shown to be more precise. With respect to lateral resolution, the determination of the coherence peak position of SWLI signals seems to lead to better results compared to phase based-interferometric measurements. This can be attributed to the well-known batwing effect. Since batwing is a nonlinear effect applying nonlinear filters, e.g. a median filter, it reduces them significantly. If filtering is applied prior to the fringe order determination and phase evaluation, the number of artefacts known as ghost steps can be eliminated without changing the modulus of the phase. Finally, we discuss the dependence of measured height values on surface slope. We show that in interference microscopy there are additional limitations which are more rigid compared to the maximum surface slope angle resulting from the numerical aperture of the objective lens. As a consequence, the measurement precision breaks down at slope changes of steeper flanks even if the modulation depth of the interference signals is still good enough for signal analysis.