为了避免平行平晶测量时前后表面干涉的影响, 基于点源异位同步移相原理, 提出一种均匀性绝对测量方法.测量分为平行平晶前后表面干涉测量、平晶透射波前测量、干涉仪空腔测量三步.每步通过在同一时刻抓拍的四幅移相干涉图恢复波前, 最终由三次测量结果计算平行平晶的均匀性分布.在非抗振平台上测试了一块厚度为60mm的光学平行平晶, 被测样品均匀性偏差的峰谷值为ΔnPV=3.32×10－6, 均方根值为ΔnRMS=2.63×10－7.检测结果与波长调谐干涉仪测量结果的峰谷值偏差为ΔPV=5×10－7, 均方根值偏差为ΔRMS=－7×10－9, 具有较高的一致性.所提方法在环境振动条件下对平行平晶均匀性检测精度可达1×10－6.

In order to avoid the influence of the interference noise introduced by the front and rear surfaces while measuring the parallel plate, an absolute measurement method for the optical homogeneity was proposed based on the principle of phase shifting by lateral displacement of the point source. Three steps of the proposed method are as follows: the front and rear surfaces of the parallel plate interference measurement, the transmission wavefront through the parallel plate measurement and the empty cavity of the interferometer measurement. The wavefront is recovered by four phase-shifting interferograms captured at the same time and the homogeneity distribution of the parallel plate could be calculated according to the measurement results. An optical parallel plate with a thickness of 60mm was tested on a vibration non-isolated platform and the measurement result indicates that the peak-to-valley value is ΔnPV=3.32×10－6 and root-mean-square value is ΔnRMS=2.63×10－7. Compared with the results obtained by the wavelength tuning interferometer, the deviation of the peak-to-valley value is ΔPV=5×10－7 and the deviation of the root-mean-square value is ΔRMS=－7×10－9. The measurement results are in good agreement with those obtained by wavelength tuning interferometer. The measurement accuracy of homogeneity obtained by the proposed method is 1×10－6 under vibration conditions.