台阶法标定干涉仪频率响应函数

大口径移相干涉仪在检测空间频率为毫米甚至亚毫米量级的相位误差时, 存在部分空间频率的相位误差失真效应。因此, 必须对大口径移相干涉仪的频率响应函数进行标定,以保证检测数据的真实性。引用评价参数-功率谱密度, 重点研究了干涉仪频率响应函数的实验标定。在理论上建立标定干涉仪频率响应函数的数学模型, 讨论了两种标定方法—正弦相位光栅法和台阶法, 分析其各自的优缺点, 综合比较后确定台阶法作为实验方案。深入研究台阶样品可以作为标定用标准台阶的条件, 即台阶阶跃的陡峭程度与台阶信噪比的选择, 探讨了台阶法标定干涉仪频率响应函数的可行性; 设计、制作了高精度的台阶相位板, 结合实验对干涉仪的频率响应函数进行标定测量, 给出有关曲线; 最后分析了几种误差源对干涉仪频率响应函数标定结果的影响及其消除方法。

Calibration of the Frequency-response Function for Interferometer Based on Step-Phase Comparing Method

When the phase wavefront is measured by a large aperture interferometer, there are anamorphic effects on the wavefront power spectral density (PSD) with high spatial frequency. So it’s necessary to calibrate the frequency-response function of the large aperture interferometer to guarantee the precision of the testing process. In this paper, the calibration principle of the frequency-response function is mainly discussed by adopting the wavefront PSD through the theoretical and experimental methods. After the calculation model of the frequency-response function is setup, the calibration methods such as sinusoidal phase grating method and step-phase comparing method are pointed out respectively. Depending on comparison between the advantages and disadvantages of these two methods, reasonable experiment method with a step is confirmed, which feasibility to calibrate an interferometer is also discussed thoroughly, and two necessary conditions for a step sample used to do calibration are given. Based on the principle of phase comparing, a standard phase object that contained a step phase is designed and fabricated. The frequency-response function is obtained by comparing the theoretical values and the measured value of the PSD. The experiment results and curves are also given in this paper. At last, the main error sources appeared in the testing process and their influences are systemically analyzed.