Point diffraction interference system for the optical element evaluation of the extreme wavelength in the next generation

用于下一代极端波长光学元件评估的点衍射干涉系统

• 批准号: 11650048
• 负责人: KAKUNAI Satoshi
• 金额: $ 2.37万
• 依托单位: Himeji Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11650048/
• 关键词: Point diffraction interferometry; Spherical wave; Absolute measurement; Phase shifting; Optical fiber; 超精密形状計測

Recently, the technological innovation using the extreme ultraviolet wavelength with high brightness of synchrotron radiation is actively advanced.In order to effectively utilize such light, it is important to develop the technology that produces and evaluates the optical element with surface accuracy over the 2 digits compared to conventional visible light. In the conventional interferometer, the aberration between the test surface and the standard reference surface is measured. Therefore the accuracy of standard surface determines the measurement accuracy. To achieve the absolute measurement accuracy, it is necessary to develop a new interferometer that has inherent very high accuracy The point diffraction interferometer is based on diffraction, which permits the generation of a perfect spherical wavefront over a specific numerical aperture by using a circular aperture with a radius comparable to the wavelength of light. Reading accuracy of the interference fringe is remarkably improved by the fringe scanning.This report describes the point diffraction interference system, which consisted of single-mode optical fiber and the fringe scanning using the laser source of visible light. The following conclusions can be drawn.(1) A perfect spherical wavefront from the single mode optical fiber was obtained.(2) By using optical fiber, the optical system with many degrees of freedom with small detecting element was constructed.(3) Reading accuracy of the interference fringe was improved by the fringe scanning.(4) The aberration from perfect spherical surface of a commercial spherical mirror was measured at the accuracy of the number nm.

近年来，利用同步辐射的高亮度极紫外线波长的技术革新正在积极推进，为了有效地利用这种光，重要的是开发与以往的可见光相比面精度超过2位数的光学元件的制造和评价技术。在传统的干涉仪中，测量被测表面与标准参考表面之间的像差。因此，标准面的精度决定了测量精度。为了达到绝对测量精度，有必要开发一种新的干涉仪，具有固有的非常高的精度。点衍射干涉仪是基于衍射，它允许通过使用半径与光波长相当的圆孔在特定的数值孔径上产生完美的球面波前。本文介绍了一种用单模光纤和可见光激光光源组成的点衍射干涉系统，该系统采用条纹扫描法，可显著提高干涉条纹的阅读精度。可以得出以下结论。(1)从单模光纤中获得了理想的球面波阵面。(2)利用光纤构成了多自由度、小探测元件的光学系统。(3)条纹扫描提高了干涉条纹的阅读精度。(4)测量了一种商品化球面镜的理想球面像差，测量精度为nm。