具有大视场小F数的自由曲面离轴反射式成像系统设计

wuweichen

具有大视场小F数的自由曲面离轴反射式成像系统设计
Optical design of the freeform reflective imaging system with wide rectangular FOV and low F-number

摘要：近年来，自由曲面越来越多地应用于离轴反射式成像系统，实现了许多具有高性能的成像系统。其中短焦距的红外相机在车载避障系统和监控安防系统中有着重要的应用。本文提出了一种视场扩展构建的自由曲面系统的设计方法，利用已有的小F数小矩形视场系统作为初始系统，通过反复构建得到了一个同时具有大矩形视场和小F数的初始结构，最终经过优化得到了一个自由曲面离轴反射式红外相机。该系统焦距为9.34mm，F数为1.39，视场达到40°×30°，最大畸变控制在5.5%并具备接近衍射极限的成像性能。另外，该系统的加工原型也得到展示，测试结果表明该系统的实际成像性能同样良好。
关键词：自由曲面系统，宽视场，小F数，视场扩展构建。
Abstract：Inrecent years, freeform optical surfaces have been used increasingly in avariety of off-axis reflective imaging systems with high performance levels.However, it is a difficult and challenging task to design an off-axisreflective imaging system that has a low F-number and a wide rectangularfield-of-view (FOV) simultaneously. In this paper, the field extensionconstruction (FEC) design method is proposed to design a freeform imagingsystem with both a low F-number and a wide rectangular FOV. When using anexisting normal system with a small rectangular FOV as the input, an initialconfiguration that simultaneously has both a low F-number and a wide rectangularFOV can be obtained after several system construction attempts. A freeformreflective infrared camera is then successfully designed after optimization andhas a focal length of 9.3 mm, an F-number of 1.39, and a wide rectangular FOVof 40°×30°. The image quality is close to the diffraction-limited level in thefar infrared band and the maximum relative distortion is 5.5%. In addition, thesystem prototype is presented after fabrication and its good practical imagingperformance is demonstrated.
Keywords：Freeform imaging system, Wide field-of-view, Low F-number, Field extension construction