同轴超短焦距折反式投影系统设计

Design of coaxial short focal length catadioptric projection system

为了缩短超短焦距投影仪的机械总长,克服传统离轴超短焦距投影系统的装调困难,降低系统的设计难度,设计了一种同轴的超短焦距投影系统。首先,通过分析像差与系统总长的关系,证明了需要保证系统总长的必要性。然后,通过镂空非球面反射镜中心部分,利用平面或球面反射镜折转光路,提出了一种新的设计超短焦距投影仪的方法。在保证光学总长的同时缩短了机械总长,提高了空间利用率,解决了同轴折反系统中存在挡光的问题。最后设计的系统总长为215mm,投射尺寸为100in。系统的投射比为0.17,物方NA为0.2,焦距为1.66mm。各个视场传递函数在内奎斯特频率处达到0.5以上,各指标都满足了投影系统的要求。同时,在透镜个数相同的情况下,系统的性能都优于传统的投影仪。

A new type of coaxial ultra short focal projector was designed in order to reduce the alignment difficulty, reduce the difficulty of system design and shorten the total length. Firstly, by analyzing the relationship between the system＇s total length and the aberration, the necessity of ensuring a long system＇s total length is proved. Then, through hollowing the central portion of an aspherical mirror and using a plane or spherical mirror to deflecting the optical path, a new design method for ultra short focal length projector is presented. It solves the blocking problem existing in the coaxial catadioptric optical system and improves the space utilization rate by ensuring a long total optical length and shortening the overall machinery length. Finally, the system＇s screen size is 100 in and the total length of 215 mm. The focal length is 1.66 mm and the object NA is 0.2 with 0.17 throw ratio. The MTFs of every field are over 0.5 at the Nyquist Frequency. All of the indexes meet the demand of the projective system. Meanwhile, in the case of the same number of lenses, the system＇s performance is better than the conventional projector.