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Study on Absolute Flatness Measurement of Silicon Single Crystalline Plane Mirrors Using Near-Infrared Interferometry

近红外干涉法测量硅单晶平面镜绝对平整度的研究

基本信息

批准号：
13650119
负责人：
UCHIKOSHI Junichi
金额：
$ 2.18万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

Single-crystalline silicon plane mirrors are widely used for the optical elements of synchrotron radiation. The purpose of this study is to measure the absolute flatness of those mirrors at nanometric accuracy by performing a three flat method with a near-infrared laser and a detector. Silicon is opaque to visible light, which prevents us from performing interference measurements with visible light and silicon as a transparent reference. We have developed the near-infrared phase-shifting Fizeau interferometer in which a near-infrared (λ =1315 nm) semiconductor laser and a near-infrared CCD camera is a source of light and a light detector, respectively. The near-infrared light is transparent to silicon, which enables us to observe interference fringes with a silicon plane mirror as a transparent reference. However, silicon has high refractive index even in the near-infrared region. A high reflectance induces a multiple-beam interference. This distorts interference fringes, which leads t … More o the measurement error of the phase-shifting method. Hence silicon dioxides acting as an anti-reflection film have been formed on the mirror in order to achieve a two-beam interference. As a result, we have confirmed that the distortion of interference fringes is suppressed. In order to investigate the measurement accuracy of a three flat method, the straightness of the center lines of three optical flats has been measured by the three flat method with visible light. And the accuracy of absolute straightness of each optical flat is 5 nm (peak-to-valley height). As a next step, flatness measurements have been performed by the near-infrared phase-shifting interferometry in which interference fringes changing with the scan of the reference along the light axis are recorded. In order to suppress the multiple-beam interference at silicon plane mirrors, we have paid attention to the fact that the contrast of fringes lowers as the cavity length becomes long. By controlling the cavity length, we have achieved a nearly ideal two-beam interference. And the reproducibility of the interferometry is 6.38 nm (peak-to-valley height) that is lower than λ/200. Less

单晶硅平面镜被广泛应用于同步辐射光学元件。这项研究的目的是通过使用近红外激光器和探测器执行三平面法，以纳米精度测量这些反射镜的绝对平面度。硅对可见光是不透明的，这使得我们无法用可见光和硅作为透明参照物进行干涉测量。我们研制了以近红外(λ=1315 nm)半导体激光器为光源，以近红外电荷耦合器件为光探测器的近红外相移菲索干涉仪。近红外光对硅是透明的，这使得我们能够用硅平面镜作为透明参照物来观察干涉条纹。然而，硅即使在近红外区也有很高的折射率。高反射率会引起多光束干涉。这会扭曲干涉条纹，从而导致t…移相法的测量误差较大。因此，为了实现双光束干涉，在反射镜上形成了二氧化硅减反射膜。结果表明，干涉条纹的失真得到了抑制。为了考察三平面法的测量精度，用可见光三平面法测量了三个光学平板的中心线直线度。每个光学平面的绝对直线度精度为5 nm(峰谷高度)。作为下一步，已经通过近红外相移干涉术进行平坦度测量，其中记录了随着基准沿光轴的扫描而变化的干涉条纹。为了抑制硅平面镜的多光束干涉，我们注意到随着腔长的增加，条纹的对比度降低。通过控制腔长，我们实现了近乎理想的双光束干涉。干涉测量的重复性为6.38 nm(峰谷高度)，低于λ/200.较少