Hardware method for zero optical path difference position detection of FTIR spectrometer

Abstract

This paper presents a method for accurately controlling the position of the zero optical path difference in the transformation process from interferogram of Fourier transform infrared (FTIR) spectrometer to spectrogram. This position has a significant impact on the position, consistency, and repeatability of spectral lines in restored spectrograms. The proposed method, known as the double-slit photoelectric aiming and triggering method (DS-PATM), can be used to precisely control the zero optical path difference position, as well as the starting and ending positions of sampling, thereby ensuring identical optical path difference in the spectrometer system. The working principle of DS-PATM is elaborated in detail, followed by a description of the optical structure of the photoelectric aiming detector and the photoelectric aiming trigger circuit. Subsequently, a displacement detection system of the spectrometer moving mirror is developed. The system is experimentally validated through displacement aiming and triggering experiments of the moving mirror of the FTIR spectrometer, conducted under standard measurement environment. The results demonstrate that using the proposed method, the standard deviation of zero optical path difference position can be measured with a confidence probability (math.) of 99.7% and a resolution of 0.1 cm−1 for Fourier transform spectrometer, yielding a value of 0.08 μm. This confirms the effectiveness of the detection system and its ability to meet the requirements of sampling interferogram with high resolution.