Study On Key Technology For Snapshot Short-wave Infrared Spectral Imager Used In Plume Radiation Characteristic Measurement

With the constant improvement of spectral imaging technology,how to get the three-dimensional image information of the target quickly has become one of key research points at home and abroad.The compressed sensing theory and the theoretical model of coded aperture snapshot spectral imager(CASSI)have brought great theoretical support for it,which is expected to break through the shortcomings of traditional spectral imaging technology and comprehensively improve the spatial resolution,spectral resolution and temporal resolution.Combined with the research background of optical measurement in shooting range,this dissertation studies the key technologies of dual camera coded aperture snapshot shortwave infrared spectral imager.The main work and innovation points are as follows:1.The traditional optical measurement in shooting range can only obtain the space attitude and angle of the target.After studying the spectral radiation characteristics of solid engine plume,a dual camera coded aperture snapshot shortwave infrared spectral imager is proposed to measure it.In this way,not only the space attitude and angle information of the rocket can be obtained,but also the solid engine plume spectral imaging information of the rocket can be obtained,which effectively enriches the measurement data of the target.And it is of great significance to monitor the engine in real time and judge its working state correctly.Then,mathematical modeling is carried out for the dual camera coded aperture snapshot shortwave infrared spectral imaging system,which provides the whole modulation process of the proposed system to the measured target light field information,which lays a theoretical foundation for the subsequent research.Finally,the theoretical temperature measurement accuracy of the dual camera coded aperture snapshot shortwave infrared spectral imaging system is simulated in detail.2.In this dissertation,the spectroscopic system of dual camera coded aperture snapshot shortwave infrared imaging spectrometer is studied.Based on the theoretical calculation model of Offner spectroscopic system,the theoretical calculation model of Offner-Wynne spectroscopic system is established,and the Offner-Wynne spectroscopic system and Offner-Wynne spectroscopic system are analyzed and compared.The simulation results show that the Offner-Wynne spectroscopic system can allow a larger incidence angle and a smaller F number under the premise of good imaging quality.Therefore,it is proposed that the Offner-Wynne spectroscopic system is more suitable for the optical system of dual camera coded aperture snapshot shortwave infrared imaging spectrometer.In the further optical design of the Offner-Wynne spectroscopic system,a calculation method of the initial structure of the Offner-Wynne spectroscopic system is derived based on the theoretical calculation model of the Offner-Wynne spectroscopic system,which has a certain guiding significance for the design of the Offner-Wynne spectroscopic system.In addition,based on the high requirement of the uniformity precision of the optical axis of the reflecting optical elements in the Offner-Wynne spectroscopic system,a design method of the mirror cylinder with the uniformity fine-tuning structure of the optical axis is proposed.The method can be applied to any optical system with two reflecting elements,which is beneficial to improve the uniformity and stability of the optical axis of the system,providing important support for the engineering of Offner-Wynne spectroscopic system.3.Based on the optical system characteristics of dual camera coded aperture snapshot shortwave infrared imaging spectrometer,and combined with the research background,an optimized optical system of dual camera coded aperture snapshot shortwave infrared imaging spectrometer was proposed.The optical system of the designed dual camera coded aperture snapshot shortwave infrared imaging spectrometer based on co-aperture design method ranges from 900 nm to 1700 nm,and the focal length is 1200 mm.It consists of two parts: the shortwave infrared imaging system and the single-dispersion coded aperture snapshot shortwave infrared imaging system.The key technical parameters of the two parts are the same and there is no visual axis difference.Therefore,in theory,shortwave infrared multispectral image fusion can be performed without image alignment in the next step.This design method can effectively improve the real-time performance,optical transmittance and compactness of the dual camera coded aperture snapshot shortwave infrared imaging spectrometer,which is conducive to the application in optical measurement scenes in the shooting range.4.According to the characteristics of dual camera coded aperture snapshot shortwave infrared imaging spectrometer,a shortwave infrared multispectral image fusion algorithm based on non-subsampled shearwave transform and improved pulse-coupled neural network model is proposed.The fusion rules of regional variance maximization and weighted average are adopted for the low frequency subband coefficients of shortwave infrared images and shortwave infrared multispectral images,and the fusion rules of improved pulse-coupled neural network model and regional variance are used for the high frequency subband coefficients.Experimental results show that the proposed shortwave infrared multispectral image fusion algorithm has good robustness and is superior to other commonly used fusion methods in objective evaluation indexes.