大口径光学元件中频波前的检测

Measurement of mid-frequency wavefront for large-aperture optics

大口径光学元件中频波前的准确评价已成为高功率激光系统中关注的焦点,元件中频波前均方根值是重要评价指标之一。根据波前中频检测频段及波前检测设备频响特性,将波前的中频区域分为两个检测频段,分别采用干涉仪和光学轮廓仪实现了中频波前均方根值的检测。采用大口径干涉仪可实现全口径波前中频区域低频段波前的检测,通过比对大口径干涉仪和采用小口径干涉仪结合分块融合平均方法的检测结果,提出采用分块融合平均方法也可检测相应频段全口径波前均方根。采用光学轮廓仪通过离散采样的方法检测大口径元件中频区域高频段波前均方根,针对不同离散采样方式的实验结果表明:3×3的采样方式能满足对410mm×410mm口径元件中频区域高频段波前均方根的检测。

It has become more important for the accurate measurement of the mid-frequency wavefront of the large-aperture optics in high-power laser systems. The root mean square of mid-frequency wavefront is one of the most important specifications. According to the frequency range of mid-frequency wavefront and frequency response characteristics of the measurement devices, the mid frequency region can be divided into two separate bands, the low frequency band and the hlgh-frequency band. The wave front in different band can be measured by interferomter and optical profiler respectively. The full-aperture mid-frequency wave- front over the low frequency band can be measured by a large-aperture interferometer. Comparing measurement results of the large-aperture interferometer and the small-aperture interferometer, one method named synthesizing averaging sub-aperture wave fronts is proposed to measure the root mean square of the full-aperture wavefront in the same frequency region. Using discrete sampling method, the mid-frequency wavefront of large-aperture optics over the high frequency band can be measured by optical profiler. It is experimentally shown that the 3 × 3 sampling pattern is enough for the measurement of the wavefront with 410 mm × 410 mm size.