针对长焦距、折反射式连续变焦望远系统的设计，提出了一种新的光学结构形式。该结构形式将可变光阑放置于球面主反射镜附近，避免了在变焦部分中使用浮动的可变光阑；然后利用二次成像结构和场镜减小变焦组元的径向尺寸，系统变焦部分仅包含变倍组与补偿组，无需前固定组与后固定组，同时无需使用特种光学材料校正二级光谱，极大降低了系统变焦部分的复杂程度。利用该光学结构形式对一台焦距600~3000 mm、最大口径300 mm、工作在可见光波段的变焦望远系统进行优化设计，该系统在60 lp/mm的调制传递函数（MTF）设计值在所有焦距和视场内均大于0.3。设计结果表明该系统像质良好、制造成本低，适用于工作在可见光波段的长焦距、变焦成像光学系统。

A new lens designed for the long focal length, catadioptric zoom telescope is presented. By setting the variable diaphragm near the primary mirror, there is no necessity to use a floating variable diaphragm in the zoom part. Then using the re-imaging form and field lens, the zoom part only contains variator and compensator, without focus unit and primelens as usual and there is no unusual partial dispersion glass used for the correction of secondary spectrum, so the complexity of zoom part is greatly reduced. By using this new lens form, a catadioptric zoom telescope working in the visible wavelength band with variable focal length between 600 and 3000 mm, 300 mm maximum aperture is designed and then optimized. The modulation transfer function (MTF) of this optimized lens is greater than 0.3 at 60 lp/mm across all the focal lengths and field of view. The result indicates that this lens reaches good image quality and is cost-effective for manufacture, so this new lens is very suitable for the long focal length, visible zoom imaging system.