为了进一步扩大视场,实现水平上下对称视场的全景环带成像,使用了一种新的利用非球面PMMA设计的全景环形透镜(PAL)。视场达到(-30°~+30°)×360°,并且缩小了中央处的盲区,提高了CCD的利用率。对全景环形透镜的视场和畸变控制方法进行了理论分析,介绍了非球面全景环带透镜的设计方法。设计了一套全非球面PMMA的全景环带系统。系统总长为53 mm,焦距为2.85 mm,PAL最大口径为62.4 mm,光谱范围为0.486~0.656 μm(可见光谱)。后继转像镜组由7片透镜构成,系统后焦距(BFL)为5.4 mm。分析结果证明系统像差校正良好,扩大了系统的应用范围。

A new improved design method of the panoramic annular lens (PAL) with aspheric surfaces is introduced. The structure is not only helpful to enlarge the field of view (FOV) of the system, but also helpful to make a horizontal symmetric field of view. The field of view reaches (-30°~+30°)×360° and distortion controlled to reduce blind zone in the center. The field of view and distortion of PAL are investigated theoretically and the method of aspheric surface design is also discussed. An aspheric PAL and its relay lens group are designed. The total length is 20.4 mm, and the focal length is 0.3 mm. To get bright and clear image, the aperture of the system is set to f/2.88, and the diameter is 16.6 mm. The spectral range is from 0.486~0.656 μm. The relay lens group is consisted of 8 pieces of lenses, with a back focal length (BFL) of 2 mm. MTF below 70 lp/mm of the system is above 0.5. The result shows that the aberrations are corrected well.