全景环带二次成像红外光学系统设计

Design of the Infrared Optical System for Panoramic Girth Secondary Imaging

传统全景环带光学系统由单透镜全景块和中继透镜系统组成,无中间像面,多用于可见光波段,不仅无法通过视场光阑限制成像视场外的杂散光,未经头部单元反射或在头部单元内多次反射后的光线也可到达像面;同时由于红外透射材料的特殊性,其应用于红外谱段将面临透过率偏低、折射率温度稳定性低等一系列问题,影响成像质量。为了解决上述问题,文章采用了以两反射镜为头部单元的二次成像全景环带光学系统结构,为引入杂散光抑制的视场光阑创造了条件。首先基于像差理论讨论了两反射镜头部单元全景环带光学系统的初始结构设计方法,并引入Q型非球面面型描述方式作为头部单元优化的重要变量,按上述思路设计了视场角(50°~70°)×360°、焦距7.5 mm、F数1.5、工作谱段8~10μm的两反射镜头部单元二次成像全景环带红外光学系统。像质评价结果表明,系统在奈奎斯特频率(20线对/mm)处调制传递函数优于0.5,成像质量良好,对光学设计视场外杂散光能够进行有效抑制,满足实际应用需求。

The traditional panoramic ring optical system is composed of a single lens panoramic block and a relay lens system,without an intermediate image plane and mostly used in the visible light band.It can not limit the stray light outside the imaging field of view through the field of view diaphragm,and the light can reach the image plane without reflection of the head unit or after multiple reflections in the head unit.At the same time,due to the particularity of infrared transmission materials,its application in the infrared spectrum will face a series of problems such as low transmittance and low refractive index temperature stability,which will affect the imaging quality.To solve these problems,the secondary imaging panoramic ring optical system with two mirrors as the head unit is adopted in this paper to create the conditions for the introduction of the aperture of the field of view for the suppression of stray light.Based on the aberration theory,the initial structural design method of the panoramic ring optical system with two-reflection lens unit is discussed.The Q-type aspherical surface profile description is introduced as an important variable in head element optimization.A panoramic band infrared optical system was designed with field of view(50°~70°)×360°,focal length 7.5 mm,F-number 1.5 and working spectrum 8~10μm.The design results show that the modulation transfer function of the system is better than 0.5 at the Nyquist frequency(20 lp line pair/mm),and the imaging quality is good.The stray light outside the designed field of view can be effectively suppressed to meet the needs of practical applications.