针对长波用320×240元非制冷焦平面阵列探测器,设计了8～12 μm波段折射/衍射混合红外连续变焦光学系统,其相对孔径大,F数为1.3,系统变焦倍率为8。变焦系统采用锗和硫化锌两种材料,通过引入二元面和非球面校正系统色差和轴外像差,在空间频率18 lp/mm处,全焦距范围内调制传递函数(MTF)均在0.5以上,接近衍射极限;系统在接收半径为17.5 μm的探测器敏感元内,能量透过率大于78%,表明该变焦系统具有良好的成像质量。

A set of 8～12 μm infrared (IR) hybrid refractive-diffractive continuous zoom lenses is designed,based on long-wave 320×240 element uncooled thermal IR focal plane arrays (FPA) detector. The continuous zoom system has a large relative aperture,the F# is 1.3, and the zoom ratio is 8. Ge and ZnS are used in the continuous zoom system. A diffractive surface and an aspheric surface are used for correcting the system color aberration and off axis aberration. The modulation transfer function (MTF) is above 0.5 in all focal distance at the spatial frequency of 18 lp/mm, and the MTF approaches the diffraction limit. The energy permeance ratio is greater than 78% when the system receiving radius in the detection sensor is smaller than 17.5 μm, which shows that the imaging quality of the continuous zoom system is very good.