为了满足基于TIR棱镜的高分辨率工程投影机对高分辨率、高照度均匀性、长后工作距离及连续变焦投影的工作需求, 设计了一种基于TIR棱镜的高分辨率像方远心连续变焦投影镜头。该镜头焦距为25~32 mm, F#为2.4, 工作在可见光波段。该投影镜头具有靶面大、分辨率高、后工作距离长及照度均匀性高的设计难点, 通过选择反远距的双高斯结构, 控制像方远心度, 通过采用不同材料搭配, 并借助CODE V的玻璃专家优化功能, 反复迭代优化, 最终, 得到满足使用要求的连续变焦投影镜头。结果表明: 该镜头在连续变焦过程中各视场MTF值在72 lp/mm处不低于0.4, 各视场RMS弥散斑直径小于8.5 μm, 畸变小于2%, 短焦边缘视场照度均匀性大于95%。该连续变焦投影镜头采用全球面设计, 结构紧凑, 成像质量好, 畸变、垂轴色差和照度均匀性都得到了较好的控制, 可以很好地满足高分辨率工程投影机的投影需求。

To meet the requirements of high-resolution, high-illuminance uniformity, long working distance and continuous zoom projection of engineering projectors based on TIR prisms, a new method for continuous zoom and high-resolution telecentric projection lens design was proposed. The focal length of the designed projection lens with F/2.4 ranged from 25 mm to 32 mm, and the lens was specialized for the visible light application. The properties of the large target surface, high-resolution, long working distance and good illumination uniformity were the main difficulties in the projection lens design. The double Gaussian model with anti-distance was chosen as the initial structure. Then a specialized control strategy for image telecentric was employed. The whole design process was conducted in CODE V associated with the expert automatic optimization strategies, such as the choice of the types of different glasses. The results show that the value of MTF within the view fields is no less than 0.4 at 72 lp/mm, the diameters of RMS diffuser is less than 8.5 μm, the distortion is under 2%, and uniformity of field of view of the short focal edge is greater than 95%. The projection lens designed with spherical surfaces show the compact structure and well image quality. The key points, such as distortion, vertical axis chromatic aberration and illuminance uniformity, are also well controlled in this design, which demonstrates that the designed project lens can meet the requirements of high-resolution engineering projectors well.