Yan Liping, Chen Benyong, Zhang Enzheng, Zhang Shihua, Yang Ye
Nanometer Measurement Laboratory, Zhejiang Sci-Tech University, Hangzhou 310018, China.
Rev Sci Instrum. 2015 Aug;86(8):085111. doi: 10.1063/1.4928159.
A novel method for the precision measurement of refractive index of air (n(air)) based on the combining of the laser synthetic wavelength interferometry with the Edlén equation estimation is proposed. First, a n(air_e) is calculated from the modified Edlén equation according to environmental parameters measured by low precision sensors with an uncertainty of 10(-6). Second, a unique integral fringe number N corresponding to n(air) is determined based on the calculated n(air_e). Then, a fractional fringe ε corresponding to n(air) with high accuracy can be obtained according to the principle of fringe subdivision of laser synthetic wavelength interferometry. Finally, high accurate measurement of n(air) is achieved according to the determined fringes N and ε. The merit of the proposed method is that it not only solves the problem of the measurement accuracy of n(air) being limited by the accuracies of environmental sensors, but also avoids adopting complicated vacuum pumping to measure the integral fringe N in the method of conventional laser interferometry. To verify the feasibility of the proposed method, comparison experiments with Edlén equations in short time and in long time were performed. Experimental results show that the measurement accuracy of n(air) is better than 2.5 × 10(-8) in short time tests and 6.2 × 10(-8) in long time tests.
提出了一种基于激光合成波长干涉测量法与埃德尔恩方程估计相结合的高精度测量空气折射率(n(air))的新方法。首先，根据低精度传感器测量的环境参数，利用修正的埃德尔恩方程计算出(n(air_e))，其不确定度为(10^{-6})。其次，根据计算出的(n(air_e))确定与(n(air))对应的唯一积分条纹数(N)。然后，根据激光合成波长干涉测量法的条纹细分原理，可获得与(n(air))对应的高精度分数条纹(\varepsilon)。最后，根据确定的条纹(N)和(\varepsilon)实现对(n(air))的高精度测量。该方法的优点在于，它不仅解决了(n(air))测量精度受环境传感器精度限制的问题，而且避免了在传统激光干涉测量法中采用复杂的抽真空操作来测量积分条纹(N)。为验证该方法的可行性，进行了与埃德尔恩方程的短期和长期对比实验。实验结果表明，在短期测试中(n(air))的测量精度优于(2.5×10^{-8})，在长期测试中优于(6.2×10^{-8})。
