Research On Broadband Spatial Heterodyne Spectrometer

Spatial heterodyne spectrometer is an interferometric spectrometer based on Fourier transform,which has the advantages of hyperspectral resolution,high optical flux and high signal-to-noise ratio.However,the spectral range is limited by the hyperspectral resolution and the limited number of detector pixels.And the single measurement spectral range of the general hyperspectral spatial heterodyne spectrometer is less than 10 nm.In some applications,the disadvantage of the mutual limitation between the spectral range and the hyperspectral resolution of the spatial heterodyne spectrometer is amplified,especially in the ultraviolet band,the spectral range is narrower.Therefore,it is of great significance to study the spatial heterodyne spectroscopy with broadband and hyperspectral resolution.At present,the echelle grating type and the total reflection type are the two main ways to broaden the spectral range of spatial heterodyne spectrometer,but most of the research prototypes work in the visible light band.The former uses the multi-order diffraction of echelle grating to realize the differential interference,thus broadening the spectral range.The latter can expand the spectral range by rotating the foldable reflection mirror to scann the blazed wavelength.However,the fabrication process of grating used in both methods is complicated.The multi-order diffraction overlapping of the echelle grating makes the design of optical system and the spectrum recovery hard.The system space layout of total reflection type is not compact and the adjustments are complex,which limits the development of broadband spatial heterodyne spectroscopy.Because of this,the broadband spatial heterodyne spectroscopy technique based on the principle of dual-grating synchronous scanning was studied in this paper.The wavelength of the spectrometer can be changed through the wavelength scanning structure.So that the spectral band can be tuned and the spectrum coverage can be widened.The spectral system design was simple,the optical elements were easy to obtain and the spectral inversion was easy to realize.In this paper,this broadband spatial heterodyne spectroscopy was systematically studied,and the main research contents were as follows:1.A tunable broadband spatial heterodyne spectroscopy technique was realized by the wavelength scanning structure based on double grating synchronous rotation.In the case of retaining the traditional static spatial heterodyne structure,a biaxial wavelength scanning system was designed and then the spectral range can be widened.2.The theory of spatial heterodyne interference spectroscopy and spectral inversion algorithm were studied.A complete process of spatial heterodyne spectral data inversion was established and successfully applied to the processing of spatial heterodyne spectral data.3.A 250-550nm tunable spatial heterodyne spectrometer was designed,adjusted and tested.The optical design,mechanical structure design,component selection,instrument adjustment and and spectral test results were described in detail.4.The error analysis and simulation of spatial heterodyne spectrum system were carried out.It included the analysis of adjustment error,interference modulation efficiency and nonlinear interference error,which provided theoretical basis for the design,adjustment and wavelength calibration of high-precision spatial heterodyne spectrometer.