傅里叶变换光谱仪非线性光程差分析与校正

Analysis and Correction of Nonlinear Optical Path Difference of Fourier Transform Spectrometer

针对由非线性光程差恢复出的光谱会出现附加频率噪声而导致复原谱线加宽,严重影响光谱质量,为此提出一种仅对特征光源进行一次测量即能完成干涉图非线性光程差校正及波长定标的方法。通过对特征光源的单次测量可获得干涉图,计算干涉图中包含的非线性相位与大致中心频率,并计算相对光程差,进而获得光程差与采样点之间的非线性映射关系,最终通过二次采样实现非线性光程差的校正。以静态双折射傅里叶变换光谱仪为例,首先构建系统的非线性光程差模型,给出非线性光程差的校正方法及其原理,然后采用汞氩灯作为特征光源进行实验验证,通过获取的干涉图提取汞氩灯的特征谱线,分析出不同波长下其对非线性光程差的影响,最后对非线性光程差进行校正和波长定标。实验结果表明,经所提方法校正后,546.074 nm波长处谱线的半峰全宽由未校正的9.08 nm变为4.14 nm,说明所提方法有效提升了光谱仪的分辨率与准确度。

In view of the fact that the spectrum recovered by the nonlinear optical path difference will appear additional frequency noise,which will lead to the broadening of the restored spectral line and seriously affect the spectral quality,a method for interferogram nonlinear optical path difference correction and wavelength calibration is proposed by measuring the characteristic light source only once.By single measurement of the characteristic light source,the interferogram can be obtained,the nonlinear phase and approximate central frequency contained in the interferogram can be calculated,and the relative optical path difference can be calculated.Then,the nonlinear mapping relationship between the optical path difference and the sampling point can be obtained.Finally,the nonlinear optical path difference can be corrected by the secondary sampling.Taking the static birefringence Fourier transform spectrometer as an example,the nonlinear optical path difference model of the system is constructed,and the correction method and principle of nonlinear optical path difference are given.Then,the mercury argon lamp is used as the characteristic light source,the characteristic spectral lines of mercury argon lamp are extracted by the obtained interferogram,and the influence of different wavelengths on the nonlinear optical path difference is analyzed.Finally,the nonlinear optical path difference is corrected and wavelength is calibrated.The experimental results show that the half-peak full width of the spectral line at 546.074 nm changes from uncorrected 9.08 nm to 4.14 nm,indicating that the proposed method effectively improves the resolution and accuracy of the spectrometer.