五棱镜扫描技术检测大口径平面镜的误差分析

Error analysis of scanning pentaprism system in optical testing on large aperture flat mirror

五棱镜扫描检测具有结构简单、检测周期短等优点,可以实现大口径平面镜低阶像差的高精度检测,是指导大口径平面镜光学加工过程的一种有效途径。为使大口径平面镜检测系统中的五棱镜扫描技术更加完善,通过理论分析和计算模拟,对五棱镜检测系统中的主要误差源,包括五棱镜制造误差、温度梯度的影响、元件位置误差、光束定位误差、自准直仪测量误差等进行研究,形成了比较完善的误差分析的数理结果。计算结果表明,在当前实验室技术条件下,五棱镜扫描检测系统在单个测量点处的测量不确定度达到230 nrad,其中影响五棱镜检测系统测量精度的主要因素为自准直仪的测量精度与温度的影响。研究结果给出了工程实际中提高五棱镜扫描系统检测精度与减小测量误差的注意事项,并可用于指导系统设计时的误差分析及精度分配。

The scanning pentaprism system has advanta ge of simple structure, quick optical testing and providing precise measurement of low order aberrations, it is an effective method for guiding optical manufacturing of large aperture flat mirror. In order to improve the scanning pentaprism technology, this letter makes detailed analysis on the error sources include pentaprism manufacturing error, thermal effect,components′ position motion, mapping error, autocollimator measurement uncertainty in the scanning pentaprism system, and derives their exact influence on the system. The analysis results show that the system′ s measurement uncertainty on single testing point can be about 230 nrad under current laboratory environment, and the accuracy of scanning pentaprism system is mainly limited by the measurement uncertainty of the autocollimator and the thermal effect, which providing the proceedings that should be cared for improving the system performance. This study also gives an important reference for the error analysis and precision distribution in design of the scanning pentaprism system.