为了实现某一大孔径定焦投影镜头作为初始结构,经过优化设计后成为大孔径变焦投影镜头,根据设计目标的DMD对角线尺寸,利用AUTOCAD对选择的定焦距系统的初始结构尺寸进行测绘,初步选择各镜材料,规划成5组元变焦系统,利用各种操作数对镜头的基本参数和外形尺寸进行限制,并合理利用2个非球面,在光学设计软件Zemax与CODE V中往返优化,得到一款在可见光波段内,短焦距为14.61 mm、视场角为60°、F数为1.5,长焦距为29.31 mm、视场角为30°、F数为1.6的变焦投影镜头。设计结果表明：各视场的传递函数(MTF)值在截至频率60 lp/mm处不低于0.46,各焦距处的弥散角不超出1.6′,镜头具有良好的像质。该镜头系统由11块透镜和1块平行平板组成,其中透镜2使用了非球面镜,该镜头片数较少,透镜折射率不高,材料容易选择。

In order to obtain a large aperture zoom projection lens after optimizing a large aperture fixed focal length projection lens as the initial structure, a reasonable initial structure of fixed focal length lens was selected.According to DMD diagonal size,the dimension mapping of initial structure was done using AUTOCAD, the material of each lens was initially selected, and 5 zoom components were programmed in this system. The design was carried out by limiting the basic parameters and dimensions of lens with various operations, and 2 aspheric surfaces were used reasonably. After the optimization by using the optical design software ZEMAX and CODE V,a zoom projection lens system in visible light band was obtained. The system has a short focal length of 14.61 mm with 60° field of view(FOV) and 1.5 F number ,while it has a long focal length of 29.31 mm with 30° FOV and 1.6 F number. The design results show that the modulation transfer function (MTF) of each FOV at each focal length is not less than 0.46 at the cut-off frequency 60 lp/mm. The dispersion angle at each focal length is not more than 1.6′. The projection lens achieves high quality of image. This lens system consists of 11 pieces of lenses and 1 piece of parallel plate, and the lens 2 uses aspheric surface. The system has less chips of lenses with low refractive index, and the material of each lens is easy to choose.