基于微偏振片阵列的动态点衍射干涉检测技术

In point-diffraction interferometer, ideal spherical wave is obtained by point diffraction theory and used as the reference wavefront, to achieve a resolution of diffraction-limited performance. This interferometer overcomes the disadvantage of the Twyman-Green interferometer and Fizeau interferometer that the measurement accuracy is limited by the surface accuracy of reference mirror, and is widely used in the fields of lithographic projection system, large astronomical telescope, aerospace, defense industry, and so on. However, the point-diffraction interferometer can’t achieve dynamic measurement which is limited by the traditional phase shifting technique, thus high-precision vibration isolation and environment control is required. In this project, point-diffraction interferometric technique and micro-polarizer array technique are combined to achieve dynamic measurement. To verify the feasibility of the scheme above, this project includes the parts of system design and building, software development, error analysis and comparison test. This method reduces the demand of vibration isolation, and the contrast of fringe pattern is adjustable. Above all, this project solves the key scientific problem that traditional method can’t achieve dynamic measurement, and can provide technical support for the further development of related industrial prototype.

点衍射干涉仪采用点衍射原理获得理想球面波，并将其作为参考波前，能够达到衍射极限性能的分辨率，克服了传统Twyman-Green型和Fizeau型球面干涉仪检测精度受限于参考标准镜面形精度的问题，广泛应用于光刻机投影物镜、大型天文望远镜、航空航天和国防军工等高科技前沿领域的球面镜检测。然而，受传统相移测量方法限制，已有的点衍射干涉仪不能实现动态检测，对隔振和环境控制要求很高。本项目拟结合点衍射干涉技术和国际研究较热的微偏振片阵列技术，开展动态点衍射干涉系统设计与搭建、配套软件开发、误差分析和比对实验等工作，以验证采用微偏振片阵列实现动态点衍射干涉检测方案的可行性，降低系统隔振要求，并实现干涉条纹对比度可调，解决传统测量方法不能实现动态检测的关键科学问题。本项目可填补国内外在该方面研究的空白，为进一步开发相关产业化样机提供技术支持。

衍射干涉仪采用点衍射原理获得理想球面波，并将其作为参考波前，能够达到衍射极限性能的分辨率，克服了传统球面干涉仪检测精度受限于参考标准镜面形精度的问题，广泛应用于高精度球面光学元件的检测。然而，受传统相移测量方法限制，已有的点衍射干涉仪不能实现动态检测，对隔振和环境控制要求很高。本项目完成了基于微偏振片阵列的点衍射干涉理论研究，分析了影响衍射波前的关键因素，设计了偏振移相的光学系统，搭建了实验研究平台以及开发了测量配套软件，建立了动态点衍射干涉检测方法。通过调节参考光和检测光的分光比值，实现了干涉条纹对比度可调，解决了不同反射率球面元件检测的问题。完成了点衍射干涉系统测量面形误差的比对实验研究，与现有Zygo球面干涉仪测量结果PV值的最大偏差为4.14nm，RMS值的最大偏差为0.34nm，证明了动态点衍射干涉系统的测量准确性。采用口径25mm、曲率半径500mm以内的凹面反射镜开展了测量重复性实验研究，实验结果表明面形误差的PV值和RMS值的重复性精度分别优于0.005λ和0.001λ(λ=632.8nm)。本项目的研究成果可以扩大点衍射干涉技术的应用范围，为进一步开发动态点衍射干涉仪产业化样机提供技术支撑。