Fine optical focusing of 1610 nm channel of CO₂ spectrometer

In order to establish the best focal plane for the 1610nm channel of CO₂ spectrometer and install the HgCdTe detector accurately, the fine focusing system, which consists of tunable laser, integrating sphere, collimator and processing software, etc, is adopted in a assembly and adjusting method based on focus energy concentricity. The focusing evaluation function of the system is based on the full width at half maximum(FWHM) of instrument line shape(ILS). During the experiment, the orientation of the detector is adjusted search to the minimum value of the focusing evaluation function, and this minimum is as final evaluation basis of positive focal plane, and fine focusing works of the spectrometer is completed finally. The results show that the average value of FWHM of ILS is 0.128 1 nm, which coincides with the theoretical number. The focusing system is simple, compact and precise, which can provides experimental guarantee for the spectral calibration.