Optical design of a static LWIR Fourier-transform imaging spectrometer with high throughput

Abstract

A LWIR Fourier-transform imaging spectrometer based on the static Michelson interferometer with high throughput is presented. Advantages and disadvantages of some common structures of imaging spectrometer are analyzed. Some selection of optimum configurations for imaging spectrometer is proceeded. The interferogram is acquired over the whole field of the camera while the scene of interest scans the path difference range, and vignetting should be strongly limited while keeping the size of the interferometer as small as possible for manufacturability and practicability reasons. The key point is to put the entrance pupil of the imaging lens inside the interferometer. The design of optical system is proposed. The field of view(FOV) is 10°.The operating wavelength range is from 8 to 12μm, F number is 2 and the working temperature range is -20°C～40°C. Optical system with 100% cold shield efficiency is good adaptability to wide environment temperature change. The spectrometer system has low utilization of solar energy in the infrared band, so to ensure its transmittance, and it is necessary to use a small amount of lenses as possible, so here the method of the active electromechanical athermalisation just uses four lenses in the system. Modulation transfer function (MTF), aberrant and distortion etc of optical system are analyzed. The results show that an excellent performance and image performance are obtained despite the simple structure.