为了满足刑侦过程中紫外光学系统远距离搜索、近距离拍照的需求,采用二元衍射元件和非球面元件,设计了一种日盲紫外机械补偿变焦光学系统,其中焦距为40mm～80mm,F数为4,工作波段为0.24μm～ 0.28μm。选用S88440909型2.54cm紫外CCD,像元尺寸为24μm×24μm,对应视场角为6°～12°。系统由7块透镜组成,结构简单、体积小巧。结果表明,在整个变焦范围内,后截距10mm处,截止空间频率21cycles/mm时,各视场的光学调制传递函数均在0.7以上,接近衍射受限曲线,畸变小于5%,像质优良,像面稳定。该设计能满足光学系统的总体设计要求。

In order to search at long distance and take photos at short distance in criminal investigation, a mechanicalcompensation solar blind ultraviolet zoom lens system was designed with binary diffractive elements and aspherical elements. Its zooming region was 40mm～80mm with F number of 4, operating at 0.24μm～ 0.28μm wavelength. The 2.54cm S88440909 ultraviolet CCD was selected as a sensor with pixel size of 24μm×24μm and corresponding field of view of 6°～12°. The optical system was composed of seven lenses with simple structure and small size. The results show that in full zooming range, MTF over all fields of view is above 0.7 at back focus length of 10mm and cut off frequency of 21cycles/mm, close to the diffractionlimited curve. The distortion is less than 5%. The zoom lens system has good image quality and stable image plane, and meets the overall design requirements of the optical system.