采用机械补偿法变焦型式, 建立两组元连续变焦光学系统模型, 在该模型的制导下, 针对中波640×512、像素尺寸15 μm制冷型焦平面阵列探测器, 设计了一款立体布局的高变倍比连续变焦光学系统。该系统工作波段为3.5 μm~4.8 μm, 焦距范围覆盖30 mm~500 mm, 工作温度范围覆盖-40℃~+60℃, 变焦过程中F数恒定为4, 系统变焦全过程具有100%冷光阑效应。设计过程中对系统冷反射进行了详细分析, 对凸轮曲线进行优化设计。设计结果表明: 该系统在08视场内, 全温度范围的光学调制传递函数在33 lp/mm处大于0.25, 在25 lp/mm处大于0.4; 全视场公差作用下系统传递函数在33 lp/mm处大于0.13。该系统具有变焦轨迹平滑, 冷反射抑制特性优良, 成像质量佳, 环境适应性好等优点。

By using the mechanical compensation method,a two-component continuous zooming optical system model was established. Under the guidance of this model, a high zoom ratio continuous zooming optical system with tridimensional distribution was designed for the cooled focal plane array detector with mid-wave infared (MWIR) of 640×512 and pixel size of 15 μm. The working wave band of the system was 3.5 μm~4.8 μm, the focal range covered 30 mm to 500 mm, and the working temperature range covered -40℃~+60℃. In the zooming process, the F number was fixed at 4, and with 100% cold diaphragm effect. In the design process, the cold reflection of the system was analyzed in detail, and the cam curve wasdesigned optimally. The design results show that in the 0.8 field of view(FOV), the optical modulation transfer function(MTF) in whole temperature range is greater than 0.25 at 33 lp/mm and greater than 0.4 at 25 lp/mm. And in the full FOV tolerance, the MTF is greater than 0.13 at 33 lp/mm. This system has the advantages of smooth zooming track, excellent cold reflection suppression characteristics, good imaging quality and good environmental adaptability.