Verkouteren Jennifer R, Steel Eric B, Windsor Eric S, Phelps John M
National Institute of Standards and Technology, Gaithersburg, MD 20899.
J Res Natl Inst Stand Technol. 1992 Nov-Dec;97(6):693-705. doi: 10.6028/jres.097.033.
Errors in the double variation teclinique of refractive index measurement are analyzed using a new approach. The ability to measure matching wavelength is characterized, along with the effect on the calculated refractive index. Refractive index accuracy and precision are very dependent on the specifics of each calibration set, particularly the difference in dispersion between the liquid and solid. Our best precision (±1 or 2×10) is attained only when the difference in dispersion between liquid and solid is small, and is dependent on an individual operator's ability to perceive changes in relief. This precision is impossible to achieve for the other glass/liquid combinations, where we are limited by a precision of approximately 1 nm in the selection of matching wavelength. A bias in the measurement of matching wavelength exists that affects the accuracy of the calculated refractive indices. The magnitude of the bias appears to be controlled by the bandpass of the graded interference filter. The errors in refractive index using a graded interference filter with a bandpass of 30 nm FWHM (full width at half maximum intensity) are an order of magnitude larger than the errors using a filter with a bandpass of 15 nm FWHM.
采用一种新方法分析了折射率测量双变量技术中的误差。对测量匹配波长的能力进行了表征，并探讨了其对计算出的折射率的影响。折射率的准确性和精密度在很大程度上取决于每个校准集的具体情况，特别是液体和固体之间的色散差异。只有当液体和固体之间的色散差异很小时，我们才能获得最佳精密度（±1或2×10），并且这还取决于操作人员感知浮雕变化的能力。对于其他玻璃/液体组合，由于在选择匹配波长时精度约为1 nm，因此无法达到这种精密度。匹配波长测量中存在偏差，这会影响计算出的折射率的准确性。偏差的大小似乎由渐变干涉滤光片的带通控制。使用半高宽（FWHM）为30 nm的渐变干涉滤光片时，折射率误差比使用半高宽为15 nm的滤光片时大一个数量级。
