使用红外干涉仪测量锗材料折射率均匀性

介绍了运用工作波长为10．6μm的红外干涉仪测试红外光学材料(锗晶体)的折射率均匀性的方法。运用传统的干涉法检验光学材料的折射率均匀性时，由于锗晶体太软，表面不易加工。其表面面形难以满足测试要求。为了消除面形偏差对折射率均匀性偏差测试的影响，使用可见光移相式数字平面干涉仪精确测试被测样品的面形偏差，该干涉仪具有很高的测试精度，其测量不确定度可以达到λ／50(λ=0．633μm)。然后在红外干涉图数据处理中将样品的面形偏差扣除，得到样品折射率的偏差分布。对锗单晶材料进行了实际测试。

Measurement of the Homogeneity of Refractive Index of the Germanium Crystal Using IR Interferometer

The method is presented to measure the homogeneity of the refractive index of infrared optical material, germanium crystal, using infrared interferometer with 10.6 μm wavelength laser as light source. Using traditional interferometric method, as the germanium material is too soft to process, the surface form of the test piece may not meet the requirement for the measurement. The digital phase-shifting interferometer with visible light source is an accurate instrument of which uncertainty is within λ/50 (λ=0.633 μm). The surface distributions of test piece are accurately obtained using the phase-shifting interferometer with visual light source and surface errors are subtracted during the data processing to reduce the affection from the surface form deviation during the interference test. A piece of germanium crystal is tested and the deviation distribution of the refractive index is presented.