紧凑型红外模拟器的光机系统设计

Optical and mechanical system design of compact infrared simulator

为满足红外成像器的仿真需求,避免目前红外模拟器的光学系统因采用TIR棱镜和离轴抛物面镜进行分光造成的体积过大、能量利用率低、照明不均匀的问题,设计了二次成像的远心光路投影系统和黑体组合反射镜的临界照明系统,有效地压缩了系统的整体尺寸,提高了系统的均匀性。采用ZEMAX进行光路分析,设计结果表明,投影系统在36 lp/mm处MTF优于0.5、波像差小于0.076 7λ、畸变小于1%,照明系统的均匀性大于98%;采用ANSYS进行力学分析,表明一阶模态频率为212 Hz,最大应力满足要求。红外模拟器尺寸小于400 mm×300 mm×400 mm,将红外模拟器与红外成像器进行对接模拟测试,验证了系统可在中波波段提供稳定的红外动态场景模拟。

Objective With the rapid development of infrared imaging systems, target recognition of infrared images can achieve the determination of ultra long range targets and the guidance of long-range weapons. To accurately analyze the performance of infrared systems, it is necessary to improve the simulation ability of the infrared simulator itself to match high-resolution and high dynamic range infrared images. The research on domestic infrared dynamic scene simulators mainly focuses on small field of view, short exit pupil distance, and the projection system adopts a one-time imaging method, which can meet the requirements of low resolution MTF.The DMD type infrared simulator requires a light source for illumination as the DMD is a radiation modulation device. The illumination method mainly uses Kohler illumination, where the filament of the light source is imaged at the entrance of the optical system through a condenser and a variable aperture. Although it can improve the uniformity of the system, the lens composition and the system are more complex. The lighting system adopts TIR splitter prisms, which require complex splitter prism design and reduce energy utilization efficiency;Adopting an off-axis system can avoid interference and occlusion between the projection system and the lighting system.However, due to the characteristics of DMD itself, it requires a large aperture angle, resulting in a large size of the lighting system. Based on the current development status of DMD type infrared simulators, the optical mechanical system design of compact infrared simulators is carried out, which effectively reduces the size of the simulator, improves energy utilization efficiency, and improves lighting uniformity.Methods Due to the large exit pupil and field of view angle of the system, the infrared projection system in this article adopts the telecentric optical path method of secondary imaging(Fig.3);The splitting method did not adopt the design of splitting prisms and off-axis, but adopted the critical illumination method of blackbody combination mirrors for design. In the selection of light sources, a high-accuracy surface source blackbody with adjustable temperature and wide range was selected as the system's light source(Fig.8). On the premise of ensuring high resolution, two reflective mirrors are added to the optical path to compress the overall volume of the system(Fig.8). Due to the overall reduction of the system, the mechanical structure of the system has also been designed and analyzed to ensure that it can provide stable mid-wave infrared simulation(Fig.12-16).Results and Discussions This article designed a compact telecentric optical path projection system and a critical illumination method using a blackbody combination mirror, effectively compressing the overall size of the system and improving its uniformity. Using ZEMAX for optical path analysis, the design results show that the MTF of the projection system is better than 0.5 at 36 lp/mm(Fig.4), the wavefront aberration is less than0.076 7λ(Fig.5), and the distortion is less than 1%(Fig.7). The uniformity of the lighting system is greater than98%(Fig.9). Using ANSYS for mechanical analysis, it was found that the first-order modal frequency is 212 Hz(Fig.12), the maximum deformation of the radial X-direction medium wave simulator is 0.054 mm(Fig.13), and the maximum stress is 17.116 MPa(Fig.14). The maximum deformation of the radial Y-direction medium wave simulator is 0.028 mm(Fig.15), and the maximum stress is 5.27 MPa(Fig.16), which meets the requirements for use. Finally, an infrared simulator system was established, with a volume of less than 400 mm ×300 mm × 400 mm. By inputting images and using a thermal image for testing, it was shown that the overall design of the system is compact, the imaging quality is high, and stable infrared image simulation can be provided in the medium wave band.Conclusions This article designs the optomechanical system of a compact infrared simulator. Through analysis of current infrared simulators, in order to make the system more compact, reduce system size, and improve system uniformity, while ensuring high resolution, a compact telecentric optical path projection system is designed. The critical illumination method of a blackbody combination mirror is adopted, effectively reducing the volume of the system. Finally, an infrared simulator system was established, with a volume of less than 400 mm×300 mm×400 mm. By inputting images and using a thermal image for testing, it was shown that the overall design of the system is compact, the imaging quality is high, and stable infrared image simulation can be provided in the medium wave band.