弹光调制干涉图最大光程差的稳定性及检测技术研究

为了提高弹光调制傅里叶变换光谱仪(PEM-FTs)中复原光谱的准确度和稳定性，有必要对弹光调制干涉图的最大光程差的稳定性和检测技术进行研究。弹光调制干涉图的最大光程差是一个不确定量，与弹光调制器的谐振状态、频率温漂特性以及驱动电压等因素有关。因此，本课题在研究弹光调制干涉仪工作机理基础上，建立弹光调制器的频率温漂模型和光程差变化关系;提出以驱动信号为基准，对激光干涉信号过零计数的方式实现干涉图的最大光差检测，且将双通道的高速比较器与FPGA相结合，实现正弦波到方波转换、快速的过零计数和误差补偿。经试验验证，采用670.8 nm的激光为参考光源，通过过零计数的方式，能实现最大光程差77.471 μm的检测，其测量误差小于0.167 nm，复原的红外黑体光谱的最大峰值波长偏差小于2 nm。

The Stability and Measuring Technology of the Maximum Optical Path Difference of Photo-Elastic Modulator Interferograms

In order to improve the accuracy and stability of the rebuilt spectrums, it is necessary that stability analysis and nicety measuring of the maximum optical path difference of interferograms in the photo-elastic modulator Fourier transform spectrometers(PEM-FTS). The maximum optical difference of interferograms is uncertain parameter，and it is relate to the resonant state, characteristic of frequency-thermal drift and driving voltage of PEM. Therefore, based on the principle of photo-elastic modulator Fourier transform interferometer, the model of the freguency-thermal drift is built, and the variety of the maximum optical path difference is analyzed; A measuring method of the maximum optical path difference is put forward, which is zero-crossing counting of laser’s interference signal when the driving signal of PEM is as the standard. In the method the dual channel high-speed comparator and FPGA are used to transform sine wave to square wave, to realize zero-crossing trigger counting and errors compensation. On the condition that the 670.8 nm laser is as the power source to produce the reference interferograms by the PEM interferometer，the 77.471 μm maximum optical path difference could be measured by the zero-crossing counting. the measuring errors is less than 0.167 nm, the rebuilt spectral peak wavelength errors of the infrared blackbody is less than 2 nm. the result is content with PEM-FTS.