Design of spatial infrared freeform optical system with large field of view

The demand for spatial infrared remote sensors with high spatial resolution and wide imaging swatch becomes more and more urgent. Optical system is an important constraint on the performance of spatial infrared remote sensors. In this paper, a novel off-axis catadioptric optical system configuration with intermediate image is proposed. The imaging principle and the initial configuration solution method are analyzed. And an off-axis catadioptric freeform optical system is designed with the spectrum of 7.8-10.2μm, the aperture of 435 mm, the focal length of 1038 mm, and the field of view (FOV) of 9×1.1°. The modulation transfer function (MTF) value is better than 0.316@25lp/mm. The maximum relative distortion is -0.27%. And this optical system has good image-side telecentricity and image illumination consistency. The results show that the spatial infrared off-axis catadioptric freeform optical system has good imaging quality and engineering feasibility.