Optical Design And Core Components Study For Static Fourier Transform Infrared Spectrometer

Fourier transform infrared spectrometers with advantages that high throughput, multimode and less stray light are widely used in basic sciences research fields including physics, chemistry and biology, and many engineering application fields including environmental engineering, remote sensing technology and meteorology detection. Recently, meeting the urgently necessary for real-time monitoring and compact infrared spectrometer in scientific and industrial development, miniature and static infrared spectrometer is widely researched by many groups at home and abroad.In this paper, a mid-infrared static Fourier transform spectrometer based on stepped mirrors is studied. The moving mirror and fixed mirror in the classical Michelson interferometer are replaced by two rectangular stepped mirrors in this spectrometer. The new interferometer system without moving components is compact and static and could realize the real-time sampling in space domain. It has significant advantages in stability, configuration, and repeatability.The work of this paper includes four parts:1. The influence of collimation lens’s field of view angle on spectral resolution is analyzed; the parameters of collimation lens are confirmed and the collimation lens based on two lenses structure is designed; the influence of thermal optics effect on recovered spectrum in the collimation lens is studied; the process for cooling infrared light source is proposed and implemented in order to solve the problem, which influences the recovered spectrum of the spectrometer, that athermalization is difficult in temperature non-uniform distribution in collimation lens.2. As the lithography-electroplating method, etching method, or conventional mechanical method, the surface quality, flatness and reproducibility of the steps will be declined, and cannot satisfy the high accuracy requirements of the Tall-stepped mirrors, a method, "slope splicing," is proposed. The structure parameters are tested and the combined effect of their errors on the recovered spectrum is analyzed. To weaken the effect of the non-uniform samples on the recovered spectrum, the spectrum is constructed by the least-squares approximation of cosine polynomials. In order to improve precision of tall steps-mirror, the method of slope splicing is developed by splicing glass with reverse order and equal angle and that is effectively reduce the production error.3. A expand lens based on objective telecentric structure with 100% cold stop efficiency was designed, which effectively solved the problem that the expand lens based on Kepler double telecentric structure has more lens and longer size, and it is useful for realization of a compact spectrometer. For further implementation of miniaturization and light-weight spectrometer, an expansion compound eye consist of three micro-lens arrays was proposed to replace the expand lens that based on classical lenses. The stop array for restrained the optical crosstalk between adjacent micro-lens optical channels is designed. With optical design software and optical analysis software, the system structure optimization, interferogram and spectrum recovery was finished.4. The construction of experiment platform and adjustment work of the static FTTR spectrometer is completed by the adjustment method that combines visible light with infrared. Furthermore, the integration and test experiments of principle sample machine were finished, the interferogram and recovered spectrum of infrared light source was successfully obtained.