Calibration Method Of Coded Aperture Imaging Spectrometer

Coded aperture imaging spectrometers are kinds of new-invented optical instruments with some advantages,including high illumination efficiency,high signal-to-noise ratio,and rapid exposure speed.The imaging spectrometer becomes so popular that many teams making a specialty of it created prototypes.And the wavelength calibration and the radiometric calibration are both necessary for a prototyping imaging spectrometer.However,coded-aperture imaging spectrometer distinguishes those typical ones for its design method and the principle of imaging.That means the calibration shall improve to couple with the coded aperture imaging spectrometer.Unfortunately,few surveys base on this.In this paper,we creatively calibrate a prototyping coded-aperture imaging spectrometer,and tips are listed as follows:Firstly,a coded aperture imaging spectrometer based on an Offner system,equipped with a convex blazed grating,is designed and introduced.To be more detailed,it includes the optical design and necessary elements.Further,it invents a simplified construction to better survey the spatial and wavelength resolution.Moreover,it puts forward a method that integrates the macro-and micro-design of the optical system.This method can apply to design and optimize the convex blazed grating with high diffraction efficiency.The design results indicate that the Offner imaging spectrometer has good imaging quality;The average diffraction efficiency of the-1st diffraction order of the convex-blazed grating in the spectral coverage 3–5 μm is 82.24%.Secondly,the section on wavelength calibration declares that the coded-aperture algorithm and its model determine the spectral resolution.And the wavelength calibration shall concentrate those above.As a result,the decoded pictures show at the end of this section.Last is the section on radiometric calibration.It declares that the distribution of intensity is non-uniform when rays arriving on the plane of the image,especially those introduced by DMD.That is nonnegligible when widening the field of view for better illumination efficiency and exposure time.And these uniformities have been necessarily corrected when operating the process of non-uniformity calibration.After that,the reactions of different pixels on the focus plane array are equal.The spectral coverage of the imaging spectrometer is mid-wave infrared radiation.Thus,the blackbody is a suitable source and standard.The absolute radiometric calibration with blackbody shows the function between the radiance and the digital number is linear.