硫系玻璃在无热化长波红外广角镜头中的应用

Application of Chalcogenide Glass in Designing a Long Wavelength Infrared Athermalized Wide-angle Lens

设计了一种工作波段为8~12μm、有效焦距为5mm、F数为2、视场角为110°的无热化长波红外广角镜头.根据红外无热化光学设计的基本原理,用了常规红外材料硫化锌、硒化锌和硫系玻璃材料制备的六片镜片,通过合理地分配各个镜片的光焦度以及相互间空气间隔等参量,在全视场角为110°的范围内实现接近衍射极限的成像效果.为了更好地控制系统像差,设计利用了硫系玻璃易于精密模压制备非球面的优点,在两片硫系玻璃镜片上设计了3处非球面.设计结果显示：系统在-40℃~60℃的温度范围内均可实现品质良好的红外成像,光学调制函数全视场内均大于0.4,同时在110°视场角时畸变控制在5%以下;实现了在较大视场角条件下控制红外广角镜头的畸变以及系统无热化等设计要求.该系统体积紧凑、质量较轻,整体设计符合民用红外车载镜头的使用要求.

A Long Wavelength Infrared（LWIR） wide-angle lens whose Field Of View（FOV） is 110° was proposed. The operating wavelength of the lens is a range from 8 to 12 μm, the operating temperature range is -40℃ -60℃, the effective focal length is 5mm, and the F number is 2. This design utilizes a combination of 6 lens elements that are made of chalcogenide glass materials, Zinc Sulfide, and Zinc Selenide. The optical powers of the lens elements as well as their locations were carefully calculated and optimized to simultaneously eliminate the chromatic and thermal aberrations for the designed wavelength/ temperature range. Taking advantage of the superior molding capability of chalcogenide glasses, the proposed design incorporates three aspherical surfaces on lens elements fabricated with chalcogenide glasses, such that optical aberrations can be furtherly corrected. According to the design results, the proposed system can produce thermal images with a close to diffraction limited performance for the temperature range from -40℃ to 60℃. At the spatial frequency of 15 lp/mm, the Modulation Transfer Function（MTF） values of the proposed system are higher than 0.4 for the entire FOV, and at the same time, system distortion is controlled below 5 %.