为了匹配不同类型和规格的工程数字投影机的投影球形幕, 提出了设计通用型投影变焦鱼眼镜头的基本方法。首先, 基于投影鱼眼镜头自身特性和通用性特点, 确定了目标系统采用的光学结构类型; 通过优选配置二组元变焦核初始条件参数, 对补偿组的位移曲线进行了线性改造, 从而使两条凸轮曲线可同步构造为标准螺旋线。之后, 通过合理控制前固定组球差及后固定组焦距, 使变焦过程中的像面保持稳定。设计结果表明, 光学系统采用二运动组元机械补偿式正组变倍负组补偿结构, 在变焦过程中可以保持全视场角160°和孔径F#为2基本不变。通过合理控制过程参量, 可以使系统适配光学引擎中棱镜的有效光学厚度为16.5~26 mm, 满足1LCD、3LCD和1DMD常见技术类型、16~24 cm(0.63~0.95 in)芯片尺寸及16∶9和4∶3两种芯片长宽比的数字工程投影机使用, 像面位移量控制在±0.03 mm以内。该设计可以满足投影鱼眼镜头的常规投影及通用性要求, 结构简单, 工艺性强。

To match the projecting images on dome screens from different types and specs of mainstream digital engineering projectors, a basic design method for a general projection fisheye zoom lens was presented. First, based on the characteristics and universality of the projection fisheye lens, the optical structure used in the final system was defined. By configuring the initial parameters of moving unit bestly, the moving path of compensating group was linearized to construct synchronously two cam curves to be standard helical lines. Then, image surface position was kept steady during a zooming process by controlling the spherical aberration of front fixed group and the focal length of back fixed group. The final design indicates that the optical system can always keep a full field angle of view of 160° and a F# of 2.0 as it uses two moving components that contain a positive zooming group and a negative compensating group. By controlling parameters reasonably, the system can match prisms of different effective optical thicknesses from 16.5 mm to 26 mm in several kinds of digital projector engines, and also can match digital engineering projectors by using 1LCD, 3LCD and 1DMD technologies with the chip sizes from 16-24 cm (0.63-0.95 in) and the length-width ratio of chip in 16∶9 and 4∶3 when the image shift is within ±0.03 mm. The design can fulfill the requirements of common and general projections with its simpler structure and good technology.