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摘要:以新一代同步辐射光源和全相干X射线自由电子 为代表的先进光源已成为众多学科领域中一种不可或缺的研究工具。先进光源技术不断进步,驱动超精密光学制造快速发展,先进光源中关键聚焦光学元件K-B镜的面形精度是影响光源性能的重要指标,要求其在几十纳弧度以下。然而,高精度K-B镜面形检测技术依然存在较大技术挑战,一直是国内外研究热点。本文介绍了反射式轮廓测量技术即长程轮廓仪(LTP)、纳米测量仪(NOM)以及拼接干涉检测技术等典型K-B镜面形检测技术的基本原理,对比分析了其技术特点,综述了国内外K-B镜面形检测技术的研究现状和最新进展,对发展趋势进行了展望。Abstract:The advanced light source represented by the new generation of the diffraction limit synchrotron radiation source and the full-coherent X-ray free-electron laser has become an indispensable research tool in many fields. The continuous development of advanced light sources drives the rapid progress of ultra-precision optical manufacturing. The surface precision of a K-B mirror, a key focusing optical element in advanced light sources, is an important factor, which should be less than tens of nano radians. However, high precision K-B mirror surface metrology still has great technical challenges and is now a research hotspot in the scientific community. This paper introduces typical K-B mirror surface metrology, including reflection profile measuring technology such as the Long Trace Profiler (LTP), the Nanometer Optical component Measuring (NOM), and stitching interference metrology. Current K-B mirror surface shape technologies are summarized and the upcoming research progress is prospected.
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表 1LTP/NOM技术典型参数
Table 1.Specifications of LTP/NOM
类型 LTP NOM 工作距离/mm 100~1100 300~1300 斜率/mrad ±5 ±5 扫描速率/(mm·s−1) 5~10 2~4 精度(RMS)/nrad 平面: ~50
曲面: ~250平面: ~50
曲面: ~500空间分辨率/mm ~1 2.5~5 表 2国内外典型LTP/NOM技术参数
Table 2.Technical specifications of typical LTP/NOM technologies at home and abroad
类型 机构/装置 设备 时间 测量范围 性能 备注 LTP 日本JASRI/SPring-8 Laser-LTP 2014 3.6 mrad 0.2 μrad
重复精度60 nrad校准测头误差
分辨率30 nradLTP 2016 ~1 m 5 nm 新型斜率传感器;
空间分辨率<1 mm美国LBNLALS LTP-II+ 2014 1 m
±2.5 mrad平面:<80 rad rms
曲面(>15 m): 250 nrad rms校正K-B位置误差 中国台湾NSRRC NLTP 2013 1.2 m 测量重复精度50 nrad 定位基准为衍射暗线;
光束定位精度高中国SSRF上海光源 LTP 2016 1 m 平面:<50 nrad
曲面(>38 m): 0.27μrad支持快速测量 中国IHEP高能所 FSP 2019 1 m 平面:25 nrad rms
曲面(3 mrad): 32 nrad rms空间分辨率优于1 mm NOM 巴西LNLS NOM 2017 1.5 m 平面:50 nrad rms 横向分辨率大 德国BESSY-II Diamond-NOM 2014 1.5 m
±5 mrad平面:50 nrad rms
曲面:200 nrad rms (±24μrad)
500 nrad rms (±5 mrad)曲率测量范围大 美国BNL DLTP 2014 1 m
±4.6 mrad平面:60 nrad rms
曲面(>15 m): 200 nrad rms曲面测量受限 OSMS 2017 1.2 m 平面:<50 nrad rms
曲面(>60 m): 100 nrad rms实现二维测量 日本JASRI/SPring-8 AC-NOM 2014 9.7 mrad ±1.2μrad ±0.24μrad (48μrad)
重复精度100 nrad rms校准扫描俯仰误差; 扫描速度慢分辨率24.2 nrad 中国SSRF上海光源 NOM 2015 1100 mm
±5 mrad0.08μrad rms (±50μrad)
0.25μrad rms (±5 mrad)空间采样频率在1~10 mm
重复精度50 nrad rms主动角控制拼接干涉仪
控制算法+精密转台测角拼接干涉仪
测角系统(RADSI)测角辅助拼接干涉仪
测角辅助装置+拼接算法大口径、小曲率长焦K-B镜
300~1000 mm; <20 mrad小口径、大曲率短焦K-B镜
100~300 mm; >20 mrad平面镜、小曲率椭圆柱镜(探索阶段) 平面优于0.30 nm rms
曲面优于0.30 μrad rms
步进单孔径测量(干涉仪尺寸)平面优于0.2 nm rms
曲面优于2 nm rms
步进单孔径测量: 2 mm×2 mm重复精度1.5 nm rms
步进单孔径量: 2 mm×2 mm结构相对简单,测量口径范围大,
测量效率高 测量频段有限,
测量精度受待测面曲率影响大测量频段宽,测量精度高,
曲率测量范围大,结构复杂,
易受环境影响,测量口径范围受限结构简单,动态范围大,测量精度高
有待进一步完善具体结构表 4国内外典型拼接干涉仪技术参数
Table 4.Technical parameters of typical stitching interferometer at home and abroad
机构/装置 设备 时间 技术性能 备注 欧洲ERSF Fizeau-SI 2019 平面镜:优于0.30 nm rms
椭面镜:优于0.30 μrad rms
球面镜:优于0.25 μrad rms主镜法校正参考误差需弥补球面低频信息空间分辨率: 80 μm MSI 2019 平面: 0.2 nm rms
横向分辨率: (2.5倍) 16 μm; (1倍) 40 μm适合于平面或强弯短镜;
存在拼接伪影美国BNL MSI 2017 残余斜率偏差: 2 μrad rms 采用曲率拼接技术 ASI-AMS 2018 平面:重复精度0.5 nm rms
椭球面:重复精度2 nm rms可以减小回程误差; 子孔径重叠
面积小,测量速度快日本大阪大学 MSI-RADSI 2016 面型高度误差:3 nm rms
重复精度:0.51 nm rms可测极端曲率面形以及椭面镜;
测量范围有限法国SOLEIL Mich-SI 2019 重复精度:0.2 nm rms 可测20 mm−1频段面形信息 复旦大学 RADSI 2017 平面镜:重复精度0.5 nm rms
球面镜:曲率偏差为2.3%验证了RADSI球面测量能力 国防科技大学 DST 2018 测量PV值8 nm;
重复精度达到1.5 nm rms一维测量;双扫描间隔; 减小回程
误差及参考误差 -
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