大视场光学系统像面照度均匀性优化

为提高大视场光学系统像面照度的均匀性,从理论上分析了光学系统像面照度的影响因素,提出使用中心遮拦产生的轴外斜光束截面积与轴上光束截面积之比对像面照度进行优化的思路。以理想系统建立数学模型,得到了中心圆形遮拦影响下不同视场角光束截面积比值的变化规律,并分析了遮拦对调制传递函数(MTF)的影响。进一步提出采用Zemax与Matlab软件动态数据交换(DDE)进行像面照度自动计算优化的方法。以某焦距56mm,相对孔径=1/5.6,视场角2ω=80°的航测镜头为例进行了优化,通过在光学系统第5表面上增加半径为4.384mm的中心遮拦,像面照度的不均匀性由优化前的22.3%降低至3.5%,均匀性明显改善。在优化实例中讨论了MTF曲线的变化,指出采用中心遮拦后的传函指标仍满足CCD探测器成像使用要求。

Illumination Uniformity Optimization of Wide-Viewing-Field Optical System

To increase the uniformity of image illumination of wide-viewing-field optical systems, influencing factors are analyzed theoretically. Idea of optimizing image illumination uniformity by contrast of axial rays′ section area and oblique rays′ section area is raised. Mathematic model is established in ideal optical system. The law that ratio of rays section area changed with viewing-field angle influenced by central circular obscurations is acquired. Degeneration of modulation transfer function (MTF) caused by obscuration is analyzed. Optimization approach through dynamic data exchange (DDE) between software Zemax and Matlab is put forward. A focal length 56 mm, relative oparture 1/5.6, 2ω=80°air-survey camera lens is taken as an example to perform the optimization, and result shows its non-uniformity of image illumination decrease to 3.5% from 22.3% by adding a central obscuration on fifth surface, whose outer radius is 4.384 mm. The change of MTF is discussed in this example, and the MTF values with obscuration can satisfy the CCD imaging requirements.