折反式超短焦投影镜头设计

Design of catadioptric ultra-short focal projection lens

针对国内外市场对近距离、大屏幕投影系统中需降低投影镜头加工难度及成本的要求,该文设计了一款超短焦投影镜头。设计过程中选用折反式结构,利用物、像关系原理,结合物方视场计算反射镜面型参数,得出反射镜面型。该方法便于校正大视场畸变、抵消折射镜组的像散和场曲,整个光学系统包括15片球面透镜和一片非球面反射镜,系统总长286 mm,投影距离500 mm,投射画面尺寸254 cm(100英寸),系统投射比0.22,相对照度大于85%,MTF(modulation transfer function)在0.4 lp/mm时大于0.5,水平TV畸变小于0.55%,垂直TV畸变小于0.65%。该系统的多项设计指标均优于市面上现有的产品指标,采用同轴球面设计易于加工、装调,可有效降低生产成本。

To meet the requirements of short-range and large-screen projection system in domestic and foreign markets, it is necessary to reduce the processing difficulty and cost of projection lens. In this case, an ultrashort focal projection lens was designed. The catadioptric structure was selected, the principle of the relationship between object and image was used, the mirror surface type parameters were calculated by combining the object field of view, and finally the mirror surface type was obtained. This method was convenient to correct the distortion of large field of view and counteract the astigmatism and field curvature of refraction lens group. The whole optical system consists of 15 spherical lenses and one piece of aspheric mirror, with a total length of 286 mm, projection distance of 500 mm, projection screen size of 254 cm(100 inch), and projection ratio of 0.22. The relative illumination is greater than 85%, the MTF is greater than 0.5 at 0.4 lp/mm, the horizontal TV distortion is less than 0.55%, and the vertical TV distortion is less than 0.65%.Many design indexes of the system are better than that of the existing products on the market, and its coaxial spherical surface design is easy to process and adjust, which can effectively reduce the production cost.