为了实现在短距离内投射出大视场、高清画面, 降低超短焦投影的加工成本和装调难度, 设计了一款不含非球面折射透镜的折反式超短焦变焦投影镜头。系统使用16.76mm(0.66in)DMD微透镜显示芯片, 16片球面折射透镜和一片非球面反射镜, 非球面反射镜能有效校正系统的畸变、抵消折射透镜组的场曲和像散。光学总长为250mm, 投影距离是424~509mm, 投射画面尺寸是2.286~2.794m(90~110in), 视场角150°, 投射比为0.21, 水平、垂直TV畸变小于0.25%, 相对照度大于90%, MTF在0.48lp/mm时大于0.5。样机测试结果显示各项指标满足系统设计要求, 全玻璃透镜的设计易于加工和生产, 有效降低超短焦投影系统的加工装配成本。

In order to project large field of view and high definition picture within a short distance, and reduce the processing cost and difficulty of setting and adjusting ultra-short focal length zoom projection, a catadioptric ultra-short focal length zoom projection without aspheric refraction lens was designed. The system includes a 16.76mm(0.66in) digital micromirror device, 16 spherical refractive lenses and an aspheric reflector, which can effectively correct the distortion of the system and offset the curvature and astigmatism of the refractive lens group. The total optical length is 250mm, the projection distance is 424~509mm, the size of projection screen is 2.286-2.794m(90~110in), the field of view is 150 degrees, the throw ratio is 0.21, the horizontal and vertical TV distortion is less than 0.25%, the relative illumination is more than 90%, modulation transfer function is greater than 0.5 at 0.48lp/mm for all zoom condition. Test results of the prototype show that the indicators meet the system design requirements. The design of the all-glass lens is easy to process and produce, which effectively reduces the processing and assembly cost of the ultra-short focal projection system.