摘要
为研究热红外光学系统中深低温下多形式、窄边框透镜的支撑问题,以星载热红外高光谱成像系统为载体,采用正交设计和有限元分析相结合的方法,设计了一套透镜柔性支撑结构,解决了从常温到约70 K的大温差环境下受支撑结构影响而出现透镜面型退化和光学基准不稳定的难题。试验表明,在多形式、窄边框透镜柔性支撑的设计分析中,柔性块的宽度决定了支撑结构与透镜间的应力大小。进行了力学振动试验验证及真空低温试验测试,结果表明,力学振动试验后带有柔性支撑环的光学系统仍可稳定可靠地工作在约70 K的环境中,且光学系统调制传递函数(MTF)优于0.4,满足指标优于0.15的要求,为多形式、窄边框透镜的支撑结构设计提供了依据。
Objective During thermal infrared hyperspectral imaging detection,the thermal background radiation caused by the optical-mechanical structure of the detection load itself will directly cause the annihilation of the detection signal,making it impossible to obtain an excellent signal-to-noise ratio.Designing deep cryogenic environment for the optical-mechanical structure is the only way to achieve an excellent detection effect.However,in order to ensure that the single components do not need to be adjusted during the transition from room temperature assembly to deep cryogenic operation of the lens group,the impacts of the thermal forces on the lens assembly under large temperature differences must be reduced,and the offset of the displacement caused by the thermal deformation of the single component must be further reduced to enhance the reliability and stability of the system.Hence,these issues pose huge challenges in the design of optical mirror support structures.Therefore,we aim to design a flexible support structure that can not only adapt from normal operations at normal temperature to operations at deep hypothermia of 70 K but also withstand rocket launch vibration tests.We also aim to reduce the time required to seal the single mirror and assembly as well as adjust the components.Methods According to the“zero”expansion design principle,the structural design of the optical system is carried out by individually sealing each lens and forming a lens group with multiple such single lenses.In designing and selecting materials,we consider using materials with similar thermal expansion coefficients for structures that directly match the mirror.For the lens support base and spectrometer base plate,“zero”thermal expansion coefficient materials are used(Table 1).After the materials are determined,a finite element simulation is used to obtain the test sample simulation results,and the thermal deformation and thermal stress of the single component are controlled through parameter adjustments.These data are combined with a range analysis of the test results to quickly identify changing trends of the effect curves of influencing factors,improve the design efficiency of single components,and ultimately form the global optimal design(Fig.3).Results and Discussions For the design of the flexible support ring,it is identified that the length L,thickness a,width b,and gap c of the flexible block are the key influencing factors on the design of the flexible block(Table 2).According to the results of the range analysis of the orthogonal test,the corresponding ranges of b,a,L,and c decrease in turn(Table 3).According to the finite element analysis results,the maximum thermal deformation of the optical mirror of the long-wave spectrometer during the transition from room temperature assembly to deep cryogenic operation of the lens group occurs on lens 1,which is 79 nm and thereby meets the requirement of the surface shape being less thanλ/6.The maximum thermal stress occurs at the connection between the grating and the adhesive layer with a value of 12.8 MPa(Fig.8),which meets the requirement of a safety margin greater than 0.25.The mechanical vibration results show that the inherent fundamental frequency of the thermal infrared long-wave spectrometer component is 376 Hz,the fundamental frequency drift before and after the test is less than 1%,and the system modulation transfer function(MTF)change before and after mechanics is 0.01(Table 4),which meets the usage requirements.A system test platform is built for performance testing.The results show that the vacuum degree is better than 8.6×10^(-5) Pa,the final temperature is approximately 70 K,the temperature uniformity is better than 2.9 K(Fig.11),and the system MTF is better than 0.4(Table 5),thereby meeting the requirement of a product index MTF value greater than 0.15.Conclusions This paper studies and solves the problem that the flexible support structure of the lens can easily cause damage to the lens and cause the surface shape of the lens to degrade under large temperature differences.The results show that the optimal design parameters of a single flexible block are a=1 mm,b=3.5 mm,c=0.3 mm,and L=11 mm.Additionally,the minimum bonding area of the glue layer is 207.96 mm2,and the safety margin coefficient is 1.39.In a vacuum environment with an operating temperature of approximately 70 K,the MTF of the thermal infrared long-wave spectrometer imaging system is greater than 0.4,which meets the usage requirements.The designed flexible support structure also considers the role of optical reference transmission.It is a thermal infrared multi-lens structure in the context of large temperature differences.The lens support structure form provides the design basis.
作者
刘国庆
马超
张宗存
刘书锋
康怀镕
张耀辉
李云端
Liu Guoqing;Ma Chao;Zhang Zongcun;Liu Shufeng;Kang Huairong;Zhang Yaohui;Li Yunduan(State Key Laboratory of Infrared Physics,Shanghai Institute of Technical Physics,Chinese Academy of Sciences,Shanghai 200083,China;Shanghai Institute of Satellite Engineering,Shanghai 201109,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2024年第17期290-298,共9页
Chinese Journal of Lasers
基金
国家自然科学基金重大项目(42192582)
国家重点研发计划(2022YFB3902000)
中国科学院青年创新促进会(2020242,2023246)
中国科学院战略性先导科技专项(XDB0580000)
民用航天技术预先研究项目(D010206)。
关键词
热红外光谱仪
低温光学
大温差
透镜柔性支撑
thermal infrared spectrometer
cryogenic optics
large temperature difference
flexible support of lens
