DESIGN OF MWIR CONTINUOUS ZOOM WITH LIGHT WEIGHT

Abstract. A thermal imaging continuous zoom system is developed with light weight for airborne optoelectronic detection and tracking apparatus. The continuous zoom system provides 4× zoom range from the focal of 37.5 mm to 150 mm. Based on the cool 640 × 512 detector with staring focal plane array (FPA), an optical system of middle infrared continuous zoom system is designed for airborne optoelectronic detection and tracking apparatus. The system is composed of a zoom system, a secondary imaging system and two reflectors. In order to improving the system performance, the whole system is adding four aspheric surfaces. The design results prove that the system worked at 3.7–4.8 μm has achieved the zoom of 37.5–150 mm, large zoom ratio of 4× and F number of 4, which can obtain the cold shield efficiency of 100% and the MTF more than 0.4 at the spatial frequency of 32 lp/mm closing to the diffraction limit. The overall lens length is 280 mm and the weight is 197 g. The optical system has the advantages of small volume, high image quality and simple structure.