| The rise of hyperspectral remote sensing is one of the major achievements in the development of remote sensing technique in the 1980 s,and it is the cutting-edge technique of current remote sensing.Because hyperspectral remote sensing has the characteristics of high spectral resolution,large number of spectral bands,and abundant information,it can be widely used in geological exploration,marine research,agricultural production and many other fields.It has been favored at home and abroad.Compared with the space spectrometer,the airborne spectrometer has the advantages of low cost,convenient use and good maneuverability.The development technology of airborne spectrometers abroad has developed earlier.At present,many mature products occupy the market,such as AVIRIS in the United States,HyMap in Australia,CASI,SASI,TABI in Canada.In China,there are also significant advances in the field of hyperspectral imaging instruments in the aerospace industry,but there are no mature products.It is difficult to meet the application requirements of hyperspectral imaging technology,which seriously hinders the application and promotion of hyperspectral imaging technology.Therefore,the research on airborne sweeping hyperspectral imager with high efficiency,good stability and environmental adaptability has important engineering significance and value.In this dissertation,the airborne sweeping hyperspectral imager is the research object.In order to meet the requirements of the airborne sweeping hyperspectral imager for the sweep frequency,the optical system surface shape error and the system dynamics performance,the high-frequency sweeping method,the integrated optimization method of the mirror component for face error and the design theory and optimization method of the main structure for the system MTF are studied.The main research work is as follows:Firstly,it introduces the application requirements of the geology and minerals industry for airborne spectral imaging instruments,and completes the overall parameter design.It determines the imaging mode of the instrument as the sweeping imaging,introduces the instrument composition and the main role of the pre-optical system.The initial design and specifications of the pre-optical system provide guidance for the subsequent optimization design of the optomechanical system.Secondly,aiming at the high requirements of the scanning speed of the mirror and the elimination of the high rotational speed of the sweeping mechanism,the high-frequency sweeping method is studied from the aspects of sweeping motion,mirror angle,number of reflectors and lightweight means.The sweeping motion scheme is determined by analyzing the common sweeping mechanism.By calculating the relationship between the reflection area of the mirror and the deviation of the rotating axis,and analyzing the volume and mass of the different number of reflecting surfaces,a oscillating mirror structure with three mirrors arranged around the axis of rotation is designed.The structure is symmetrical about the axis of rotation,which can effectively reduce the difficulty of static balance and dynamic balance correction of the high-speed oscillating mirror,and improve the angular utilization during the scanning period,thereby effectively improving the proportion of imaging time in the cycle.Through the optimization of topology and optomechanical optimization,the maximum precision of the mirroring accuracy is ensured while the mirror surface accuracy is ensured;the proposed high-frequency sweeping method can achieve 30 Hz scanning.The frequency is much higher than the existing research level,and it also has the advantages of high surface precision,low quality and good mechanical properties.Then,aiming at the problem that the mirror surface shape of the mirror is greatly affected by gravity and assembly stress,the research on the optical machine integration optimization method of the mirror and its flexible supporting structure is completed,and how to optimize the integration through the optical machine is introduced in detail.This method reduces the influence of the self-weight deformation of the mirror and the assembly stress on the shape error of the mirror surface.The key parameters of the mirror surface and its flexible support structure are determined by theoretical analysis.The parametric modeling method is used to realize the rapid modification of the key parameters of the model.The optimization function of the mirror assembly is established.The solution of the optimization function is such that the RMS value of the folded mirror meets the requirement of 1/20λ under the influence of gravity load and assembly stress.Finally,aiming at the low quality of the main structure and strong dynamic environment,the structural design theory and multivariable integrated optimization method for the MTF of airborne vibration environment are studied.The verification method is proposed by calculating the optical MTF using the sensitivity matrix method and finite element method duringthe vibration environment.The structure of the frame combined with the thin-walled tubular structure is proposed.The hood and the thin-walled tube structure are integrated to ensure the rigidity and space saving.The design is strong and can be applied to off-axis optics.The main structure of the system is optimized by multi-variable integrated optimization method.It can improve the mode under the condition that the quality is basically unchanged.The theoretical calculation method proves that the vibration environment of the airborne platform has little effect on the system MTF;The applicable scope of the structure shows that the structure can be applied to airborne systems with pixel size greater than 10μm.Finally,the correctness and effectiveness of the main structure optimization design method can be proved by experiments,which can meet the application requirements of aerial spectrum remote sensing.This project has completed the research on the high-frequency sweeping method,the mirror assembly and the optomechanical integrated optimization design method of the main structure.Research conclusions can be used to provide the method and reference for the optimal design of the structure,which have great significance forthe development and application of airborne swept imaging spectrometer with high efficiency,good stability and strong environmental adaptability. |
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