大变倍比制冷型红外双波段变焦光学系统设计

Design of cooled infrared dual-band zoom optical system with large-magnification-ratio

第三代红外焦平面探测器的不断发展使得探测器可以同时对两个不同波段的红外辐射进行响应,从而输出双波段对应图像,双波段图像在目标探测和识别领域应用前景广阔。本文针对航空探测应用,采用320×256双色红外制冷型探测器,设计了一种工作波段在中波3.7~4.8μm和长波7.7~9.5μm的大变倍比制冷型红外双波段变焦光学系统,用于对目标的红外探测。该光学系统采用折射式和折反式结构相结合的方式,可实现光学四视场切换式大范围变焦,采用二次成像以达到100%冷光阑效率。该光学系统四视场焦距分别为32 mm、200 mm、800 mm、1600 mm,变倍比为50×。实验结果表明,该光学系统在双波段各变倍状态下,在调制传递函数特征频率为17 lp/mm时均接近衍射极限。该光学系统具有双波段、变倍范围大、大变倍比、快速切换多视场、结构简单紧凑、成像质量高等特征,将在搜索、侦察等安防领域中得到广泛应用。

The development of third-generation infrared focal plane detectors allows them to respond simultaneously to two different bands of infrared radiation,and the dual-band image brings significant benefits to target detection and identification.In this paper,a cooled infrared dual-band zoom optical system with largemagnification-ratio is designed for aerial detection applications.The system includes a 320×256 dual-color infrared-cooled detector.It operates in the bands of 3.7−4.8μm in mid-wave and 7.7−9.5μm in long-wave.The optical system adopts the combination of refractive and catadioptric structures to realize an optical fourfield-of-view switching wide-range zoom.In order to realize the 100%cold diaphragm efficiency,a secondary imaging mode is adopted.The four-field-of-view focal lengths of the optical system are 32 mm,200 mm,800 mm,and 1600 mm,and the zoom ratio is 50×.The experimental results show that the optical system is close to the diffraction limit at a modulation transfer function eigenfrequency of 17 lp/mm in each dual-band zoom state.The optical system has dual-band characteristics,extensive zoom ratio and large range,fast switching of multiple fields of view,simple and compact structure,and high-quality imaging,which will be useful in a wide range of security fields such as searching,reconnaissance,and so on.