Infrared Image And Spectral Information Processing Of Stepped Micro-mirror Imaging Fourier Transform Spectrometer

Imaging spectroscopy technology organically combines optical imaging technology,spectroscopy technology,precision machinery,electronic technology and computer technology.It can simultaneously obtain three-dimensional information(two-dimensional spatial information and one-dimensional spectral information)of the target.It is Cutting-edge technology and important means in the field of the visible light and infrared remote sensing technology.In the mid-and long-wave infrared bands,Fourier transform imaging spectrometers are widely used due to their multichannel and high-throughput advantages.The static Fourier transform imaging spectrometer based on the stepped micro-mirror(SIFTS)developed by our research group realizes the acquisition of optical path difference by using the stepped micromirror manufactured based on the MOEMS(Micro Opto Electro Mechanical System)technology to replace the high-precision moving mirror in the Michelson interference instrument,and has the advantages of multi-channel,high-throughput and high stability.It can have broad application prospects in resource exploration,environmental monitoring,disaster reduction forecasting,meteorological observation,space remote sensing,military target detection and other fields.Image and spectral information processing is the basis of imaging spectrometer applications.For the static Fourier transform infrared imaging spectrometer based on the stepped micro-mirror,there are two major difficulties in its image and spectral information processing.First,the signal modulation of the instrument is unique,making the processing flow of the image and spectral information processing different from that of the traditional Fourier transform imaging spectrometer,which needs to combine the structure and principle of the instrument and propose the image and spectral information processing method suitable for SIFTS on the basis of the existing methods.Secondly,the special device in the instrument interference system—the stepped micro-mirror manufactured based on MOEMS technology,its inevitable machining accuracy error and assembly error will introduce multiple dimensional compound errors in the image and spectral information.In addition,the mid-wive infrared band signal is relatively weak and the background noise is large,which can bring great difficulty in extract effective information and further processing.In view of the problems of infrared spectrum information processing brought by the above characteristics and specific application requirements,this thesis carried out the research on the image and spectral information processing of the static Fourier transform infrared imaging spectrometer based on the stepped micro-mirror.The research work of this thesis mainly includes the following five parts:1.By analyzing the working principle of SIFTS,combined with the unique structure of the stepped micro-mirror in the interference system,a corresponding scene image reconstruction algorithm was proposed.Using image morphology operations and wavelet decomposition to enhance the edge information of the image unit,which solved the problem of interference of the background image information on the edge information detection of the image unit.And using the feature match stitching,which improved the registration accuracy of image units.The image fusion based on frequency domain filtering is performed on the stitched scene image,which solved the problem of stitching gaps in the scene image.In order to verify the scene image reconstruction algorithm,an outfield experiment of the principle prototype was designed and carried out,and a high-quality image of the target scene was successfully obtained.2.Through the analysis of the special structure of the stepped micro-mirror and its modulation effect on the spectra,combined with the spectrum reconstruction process of the traditional Fourier transform spectrometer,the corresponding spectrum reconstruction algorithm was proposed,which can extract spectral information of any target in the data cube.In addition,a non-uniform sampling correction algorithm of the optical path difference in spatial domain was proposed for the sub-step height error of the stepped micro-mirror.Combined with the step height error test data of the stepped micro-mirror,the least square fitting was used in the optical path difference domain to correct the non-uniform sampling of the optical path difference,and the wave number drift and phase error caused by it in the frequency domain were corrected.3.The spectra and radiation calibration of the instrument have been completed.The systematic errors in the interference core of the instrument which has the greatest influence on the interferogram and the reconstructed spectrum was analyzed,and the conversion between the system errors such as the adjustment errors of each dimension of the interference core device and the distortion of the interference fringe in the space domain and the wavenumber shift in the frequency domain was derived in detail,then an error propagation model was established.According to the error transfer model of the interference core system,a spectral radiation calibration method suitable for SIFTS is proposed.Spectral radiation calibration experiments were designed and carried out to verify the effectiveness of the spectral radiation calibration method.4.The performance of SIFTS is evaluated from four aspects: spatial resolution,spectral resolution,signal-to-noise ratio,qualitative identification and quantitative analysis performance.The theoretical spatial resolution of the instrument was calculated and verified by using external field experimental data.The theoretical spectral resolution of the instrument was calculated verified by the spectral resolution measurement experiment.A theoretical model of the interferogram signal-to-noise ratio of the instrument was established according to the parameters of the instrument's various optical components and the parameters of the detector,and the conversion relationship between the interferogram signal-to-noise ratio and the spectral signal-tonoise ratio were derived in detail.On the basis,the theoretical model of the signal-tonoise ratio was verified by the experimental results of the standard radiation source measurement.The qualitative identification experiments of liquid acetonitrile and the quantitative analysis experiments of CO2 gas in the laboratory was designed and carried out.The qualitative identification and quantitative analysis capabilities of the instrument have been verified.