中文摘要：

针对高变焦比连续变焦光学系统，提出了一种双双组联动型变焦系统的设计方案，完成了变焦方程的推导。采用非球面技术，运用所推导出的变焦方程，完成了变焦比为40倍、F数为4、工作波段为3.7．4.8μm的中波红外连续变焦光学系统的设计。光学系统由八片透镜组成，引入了四个非球面，可以实现10～400mm连续变焦，满足冷光阑效率为100％，变焦曲线平滑无拐点。在不同的变焦位置，光学系统的奈奎斯特频率处（16lp／mm）MTF值均大于0.3，RMS点斑半径均小于22μm。系统具有成像质量高、镜片数量少和结构紧凑等特点。

英文摘要：

For the continuous zoom system with large zoom range, a design method named double two-group zoom system was introduced and the correspondent formulas were derived in this paper. Then a MWIR continuous zoom system with zoom range of 40 was designed. The system consisted of 8 elements with 4 aspheric surfaces, and worked in the wave band of 3.7-4.8μm. It performed with 100% cold shield efficiency in the continuous zoom range of 10-400 mm. The F/number was 4 and the zoom paths were smooth. The MTF value in Nyquist limit （16 lp/mm） was more than 0.3 and the RMS radius of the spot diagram was less than 22μm over the full zoom range. The system is of high image quality and compact in structure.