近红外多普勒差分干涉仪稳定性结构研究

Stable Structure of a Near-infrared Doppler Asymmetric Spatial Heterodyne Interferometer

针对现有结构无法满足大尺寸差分干涉仪稳定性固定,以星载近红外差分干涉仪稳定性结构为研究目标,优化选择光学材料实现实体差分干涉仪的热补偿,提高了光学元件温度稳定性;以支撑结构的最大结构应力和光机粘接面处最大剪切应力小于许用应力为优化目标,建立数学模型,优化设计支撑结构参数,调节组件基频,提高了组件的力学稳定性。有限元分析支撑结构最大应力65.56 MPa,小于材料的抗拉强度,光机粘接面最大剪切应力3.4 MPa;环境温度变化5℃,分光棱镜面形RMS最大变化量1.671 nm,热应力带来的干涉图畸变可忽略。力学振动试验前后,光学测试干涉条纹频率(50个条纹数)未发生变化,差分干涉仪结构满足星载力学环境条件。该方法也适用于棱镜式干涉仪稳定性支撑结构。

The mounting for a space-borne Doppler Asymmetric Spatial Heterodyne(DASH)interferometer,which is a key part of the space-borne DASH wind instrument,should be able to withstand the mechanical and thermal conditions of being space-borne.As spectral resolution increases,the size of the DASH interferometer increases.The stable rugged support structure for a large-sized interferometer has become a key issue.By far,the vast majority of the vibrational energy is produced at lower frequencies.Therefore,in order to improve mechanical performance,an effort can be made to ensure that the lowest natural frequency of the mounting structure is as high as possible.In existing approaches,the natural frequency of the assembly can be increased by increasing the adhesive area.However,the(metal-to-glass)gluing surface tension breaks during the vibration tests because of the lower natural frequency.In this paper,a novel,and stable support structure is proposed,with its effectiveness exemplified for a Near-Infrared(NIR)DASH interferometer.Based on the principle of DASH interferometer technique,the materials and dimensions of the optical components were selected to compensate for the phase shift at the fringes as the arms expand with temperature,which improves the optical components′thermal stability.The mathematical model of a structure was established,and the detail optimization process was designed.Parameters affecting the spring constants were analyzed.The parameters of the structure were optimized by requiring the maximum mechanical stress of the structure and maximum shear stress at the gluing surface to be less than the strength value.The spring constants were designed to adjust the natural frequency of the DASH interferometer assembly and improve the mechanical stability.The mathematical model results show that the lower spring is much stiffer than the top spring.The maximum shear stress of the structure was 48 MPa.The maximum shear stress at the gluing surface was 1.4 MPa.The bending deformations of the gluing surfaces were less than 1μm.The Finite Element Analysis(FEA)results show that the maximum stresses of mechanical components and optical components were 65.56 MPa and 0.56 MPa,which are less than the tensile strength of the material.The maximum shear stress at metal-to-glass gluing surfaces was 3.4 MPa.The safety margin was 3.4.The maximum shear stress at the glass-to-glass gluing surface was 0.16 MPa.The safety margin was 83.3.All values have a high safety margin.The FEA results were consistent with the model calculation results.As the DASH interferometer is thermally stabilized about 5℃above the wind instrument temperature,the Finite Element Model(FEM)of the DASH interferometer assembly was established to analyze the thermal stability.Under the environmental temperature change of 5℃,the Surface Shape Error(RMS)of beam splitters was 1.671 nm.The interferogram distortion caused by thermal stress can be ignored.The vibration test results indicate that the relative error of natural frequencies between the FEM and sine sweep test was less than 4%.The results from FEA and vibration tests agree with the model calculation results.The optical results indicate that the fringe frequency did not change(the number of fringes is 50)before and after the vibration test,which directly reveals that there was no breakage in the gluing surfaces(metal-to-glass gluing and glass-to-glass gluing),and the interferometer assembly remained undamaged.The phase shift was caused by the location accuracy of the DASH interferometer assembly in the optical system.Compared with existing methods,the mechanical performance was improved.The proposed structure can meet the requirements of the launch environment.Moreover,the proposed design of the stable support structure can be used in other interferometers.And the structure was used to mount a short infrared wave DASH interferometer,which is larger than NIR DASH interferometer.