Lacey Ian, Geckler Ralf D, Just Andreas, Siewert Frank, Arnold Thomas, Paetzelt Hendrik, Smith Brian V, Yashchuk Valeriy V
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Germany.
Rev Sci Instrum. 2019 Feb;90(2):021717. doi: 10.1063/1.5058710.
Deflectometric profilometers based on industrial electronic autocollimators (ACs), as the ELCOMAT-3000, have become indispensable tools for precision form measurements of optical surfaces. A growing number of labs at synchrotron and free electron laser x-ray facilities are going for BESSY-II NOM-like versions of the AC-based profilometers. These tools have proven capable of characterizing state-of-the-art aspherical x-ray optics with an accuracy on the level of 100 nrad (root-mean-square) over the spatial frequency range limited by the size of the aperture used in the profilometer. Typically, a round aperture with a diameter of about 2.5 mm is used. Previous investigations have shown that with the optimally aligned 2.5-mm aperture, the spatial resolution of a NOM-like profilometer corresponding to the first zero-crossing of the optical transform function (OTF) is ∼1.2 mm. In this paper, we investigate the performance of an AC ELCOMAT-3000 for a slope profilometer with different aperture sizes and shapes. The results of angular calibration of the AC equipped with circular and rectangular apertures placed at different distances from the AC are discussed. The calibration was performed at the Physikalisch-Technische Bundesanstalt using the original experimental arrangements, also discussed in the paper. The OTF measurements with the specially developed test sample with chirped surface slope profiles were performed at the Advanced Light Source X-Ray Optics Laboratory (XROL) in application to a new optical surface measuring system under development at the XROL. In the OTF measurements, we have shown that application of a rectangular aperture with dimensions of 1.5 mm × 3 mm improves the spatial resolution in the tangential direction by a factor of ∼1.4 compared to that of the standard circular aperture of 2.5-mm diameter. We believe that the results of our investigations are crucial for reaching fundamental metrological limits in deflectometric profilometry utilizing state-of-the-art electronic autocollimators.
基于工业电子自准直仪（AC）的偏折轮廓仪，如ELCOMAT - 3000，已成为光学表面精密形状测量中不可或缺的工具。越来越多位于同步加速器和自由电子激光X射线设施的实验室正在采用类似BESSY - II NOM的基于AC的轮廓仪版本。这些工具已被证明能够在轮廓仪所用孔径大小限制的空间频率范围内，以100纳弧度（均方根）的精度表征最先进的非球面X射线光学元件。通常使用直径约为2.5毫米的圆形孔径。先前的研究表明，对于最佳对准的2.5毫米孔径，类似NOM的轮廓仪对应于光学传递函数（OTF）第一个过零点的空间分辨率约为1.2毫米。在本文中，我们研究了配备不同孔径尺寸和形状的AC ELCOMAT - 3000作为斜率轮廓仪的性能。讨论了配备圆形和矩形孔径且与AC距离不同的AC的角度校准结果。该校准是在德国物理技术研究院使用原始实验装置进行的，本文也对此进行了讨论。在先进光源X射线光学实验室（XROL），针对XROL正在开发的一种新型光学表面测量系统，使用具有啁啾表面斜率轮廓的专门开发的测试样品进行了OTF测量。在OTF测量中，我们表明，与直径2.5毫米的标准圆形孔径相比，应用尺寸为1.5毫米×3毫米的矩形孔径可使切向方向的空间分辨率提高约1.4倍。我们认为，我们的研究结果对于在利用最先进的电子自准直仪的偏折轮廓测量中达到基本计量极限至关重要。
