| In order to meet the application requirements of high resolution,high quantification,high signal-to-noise ratio,and wide field of view,infrared imaging spectrometers needs to improve the spectral accuracy and detection sensitivity,urgently.Infrared imaging spectrometers usually works at low temperature to suppress its internal stray radiation.Because the temperature is extremely low,the design and analysis methods of the infrared spectrometers at low temperature are different from that of the spectrometers at room temperature.In order to achieve the high spectral accuracy,it is nessesary to study the infrared spectrometer with high image quality and low spectral distortion with wide field of view and the cryogenic optical assembly.In order to achieve the high detection sensitivity,it is nessesary to reduce the size of the spectrometer and study the high accuracy analysis method of infrared internal stray radiation.In this paper,the current state of the infrared imaging spectrometers and the infrared internal radiation are studied and discussed.The basic theories of the infrared radiation transmission and infrared spectrometer are studied.This paper focused on the Litttrow infrared imaging spectrometer,the spectrometers with high image quality,low spectral distortion,small size and wide field of view,the residual correction method of calculation of the image plane location at low temperature,and the internal stray radiation analysis method were studied in depth.The main research results of are as follows:1)For the requirements of small volume,high image quality,and low smile and keystone distortion of the infrared spectrometers with the wide field of view,an infrared spectrometer based on sub-field splicing is proposed.Compared with other 10 kinds of spectrometers which were studied in this paper,the optimal volume and performance were achieved.The 150 mm field of view and ultra-compact volume and high optical performance are achieved by splicing six sub-field optical systems.2)For calculation residual error of the image plane location at low temperature,a modification method is proposed.The calculation and modification formulas of residual errors caused by using the thermal expansion coefficients of the single temperature,and nonlinear errors of refractive index at low temperature,and the thermal lens parameters of the aspheric surface are derived.In order to verify the accuracy of the proposed method,a modulation transfer function test apparatus was set up to test the image plane locations of the telecentric objective of the Littrow spectrometer at different temperatures.The test results are consistent with the design.The feasibility of this method was verified.3)For the lack of a fast and accurate calculation method in the analysis of internal stray radiation of the Littrow spectrometer,an analytical method based on the view factor is proposed.The calculation models of the internal stray radiation of the sources of the Littrow spectrometer are established and derived.Based on the proposed method,the internal stray radiation of the Littrow spectrometer was calculated.The calculation results are consistent with the simulation results.To verify the proposed method,a designed experiment was conducted to test the internal stray radiation of the Littrow spectrometer.The internal stray radiation test results agree with the calculated and simulated results.The feasibility of this method was verified. |
