干涉法实时测量浅度非球面技术

Testing of weak aspheric surface by real-time interferometry

提出了一种实时干涉检测非球面的新方法,该方法无需补偿器、计算全息图等辅助元件就能实现对浅度非球面的测量。对非球面度较小的非球面,直接利用标准球面镜作为参考表面,通过数字干涉仪可以测得全孔径位相分布,将所得的数据剔除参考球面波相对理论非球面的偏差,并运用最小二乘拟合求得机构定位误差,消去此误差,即可获得真实的面形信息。利用该方法对一口径为350 mm的浅度双曲面进行了测量,通过数据分析和处理得到面形误差的PV值和RMS值分别为0.387λ和0.048λ(λ=632.8 nm),将该结果与零位补偿的检测结果相比较,两面形分布是一致的,其PV值和RMS值的偏差分别为0.033λ和0.006λ,说明该技术用于检测浅度非球面是切实可行的。

A real-time interferometric method for testing asphere was proposed to measure aspherical surface with small asphericity without other null optics. When the tested asphere was close to a sphere, a sphere mirror was used as the reference surface, the phase distribution can be obtained by the digital wavefront interferometer. The surface error was obtained by subtracting the theory wavefront error from the phase datum and eliminating the translation error through least-square fitting. Meanwhile a φ 350 mm aspheric mirror was measured by this method. As results, the PV and RMS of the surface error are 0. 387 λ and 0. 048 λ, respectively; the surface map and interferogram measured by proposed method are consistent with those tested by null compensation; and the differences of PV and RMS errors between them are 0. 033 λ and 0. 006λ, respectively. It concludes that this method is feasible and accurate.