Study Of Hyperspectral Imaging Spectrometer Based On The Improved Dyson Structure

This thesis focuses on the urgent need of high-performance and miniaturized hyperspectral imaging equipment for small aerospace platforms(such as UAV,Cubesat),the laboratory,field test and the vehicle platform.A new Dyson hyperspectral imaging technology has been completed and the prototype has been developed under the assist of the Key laboratory fund of the Chinese Academy of sciences.This technique has the advantages of large relative aperture,compact structure,small size and light weight.While ensuring the high signal-to-noise ratio of the instrument,effectively eliminate the smile and the keystone.In this paper,the design idea of object-image separation is proposed innovatively.The traditional Dyson structure is improved and optimized,which effectively solves the problem of spatial overlapping of the key components.Engineering difficulties of the traditional Dyson hyperspectral imaging system is overcome.Based on this design idea,a high performance hyperspectral imaging system with a relative aperture of 1/1.5,a spectral resolution of 1.67 nm and a field angle of view of 36.87° was designed.In order to validate the correctness of the new Dyson hyperspectral imaging technology proposed in this paper,the principle prototype has been developed.The designed spectral resolution of this prototype is 1.6nm and has a large relative aperture of 1/2.5 and a high spatial resolution of 0.22 mrad.The prototype volume is only 96mm×120mm×260mm,weighs only 1.7kg.At the same time,the spectral calibration,outdoor sweep experiment and field flight experiment of the prototype have been done.The calibration results show that the average spectral resolution is 1.62 nm,the keystone is 0.1% and the smile is 4?m,which is consistent with the theoretical design.The flight experiment results show that the new Dyson hyperspectral imaging system has the advantages of good stability,high spectral resolution,small size,light weight,regular shape,low power consumption and easy interface with the platform.The dissertation includes the following sections:i.Introduce the background and significance of this topic and the main application fields of spectral imaging technology.Based on this,the trend of spectral imaging technology toward large field of view,high signal-to-noise ratio or high resolution,miniaturization is summarized.It is pointed out that the Dyson structure Spectral imaging technology meet the above direction.ii.The basic principle and realization of spectral imager are discussed.The principle of filter type,interference type and dispersion type spectral imaging technology is introduced emphatically.Through the comparison of various principles and performance,it is pointed out that the hyperspectral imaging technology based on Dyson structure is the most suitable form for the miniaturization of high performance spectral imaging instruments.iii.The optical characteristics of Dyson structure and the aberration characteristics of Dyson spectral imager are analyzed.It is proved that the Seidel aberration of Dyson structure is zero and has good optical properties.The influence of grating spectral aberration was introduced into the system for analysis,and it was concluded that grating with parallel etching at equal intervals would not introduce additional aberrations.The formula deduction is completed,which provides the theoretical basis for the design of Dyson hyperspectral imager.iv.The idea of object-image separation was proposed.The Dyson hyperspectral imaging system was improved and optimized to solve the problem of components overlap caused by the compact structure of traditional Dyson hyperspectral imaging technology.With this design,the compact layout and rapid construction of a miniaturized hyperspectral imager can be accomplished with a common industrial camera.And based on this design idea,a new type of Dyson hyperspectral imaging system is designed to realize the purpose of spectrum imaging with large field of view,large relative aperture and hyperspectral resolution.v.Developed the prototype of the new Dyson hyperspectral imager.In the development,a large relative aperture,moderate focal length and field of view,telecentric objective lens is designed.The lens with high resolution imaging capabilities(the MTF at 76lp/mm are still near the diffraction limit)is extremely suitable for spectral imaging system based on small Pixel CMOS device.At the same time,an integrated design method of Dyson hyperspectral imaging technology is proposed,and the system imaging quality is obviously improved.The signal to noise ratio of the prototype system is analyzed,which fully proves the superiority of the design.vi.Spectra,radiation calibration,outdoor sweep test and flight test were carried out on the new Dyson hyperspectral imaging prototype.And in the test good spectral image data is obtained,which fully validated the superiority and stability of the new Dyson hyperspectral imaging prototype.