Spectral Radiometric Calibration System And Application Using Supercontinuum Laser

The quantitative application of optical remote sensors with wide spectral range and high spectral resolution in the field of atmospheric environment monitoring has promoted the development of laboratory spectrally resolved scanning calibration technology.High spectral resolution calibration technology requires a tunable light source with a wide tuning range,narrow output bandwidth,and high radiant flux.At present,the main tunable light sources commonly used in the solar reflection spectrum(350 nm to 2500 nm)are the monochromator and the tunable laser.Limited by the spectral flux of the halogen lamp and the relative aperture of the monochromator,the spectral radiation flux of the monochromator light source is about 100 nW nm-1 to 1 ?W nm-1,which limits the signal-to-noise ratio and accuracy during calibration.Tunable lasers have extremely high wavelength accuracy,but the coverage spectrum of a single tuning laser is limited,generally between several nanometers to several hundred nanometers,and the debugging process is complicated,the operating environment is strict,generally used in the highest precision primary radiation standard system.In order to meet the application requirements of remote sensor calibration,an absolute spectral radiometric calibration system based on the supercontinuum laser and monochromator was proposed,using the wide spectral range and high power density of the supercontinuum laser source,as well as the fast tuning and spectral resolution adjustable characteristics of the monochromator,an efficient coupling optical path from the supercontinuum laser to the monochromator was designed to realize the continuous tuning output of the monochromatic light in a wide spectral range.The output spectral bandwidth is adjustable in the range of pm?nm,and the spectral flux is 1 mW nm-1?10 mW nm-1,by introducing monochromatic light into the integrating sphere,the system level calibration of spectral radiance/irradiance responsivity of optical remote sensor can be realized.In this paper,the spectral radiometric parameters of SCM calibration system were evaluated.The deviation between the output wavelength of monochromatic light and the set value of monochromator in a wide spectral range is better than 1 nm,and the wavelength accuracy is in the order of pm.The experimental device for measuring the instability and non-uniformity of the integrating sphere light source was set up.The results show that the instability of the light source was less than 0.5%/h,and the spatial plane and angle non-uniformity were less than 0.4%(?21 mm)and 0.57%(±20°)respectively.Using the spectral polarization analyzer,the linear polarization degree and polarization orientation angle of the output light were obtained.In order to verify the absolute spectral radiometric calibration ability of SCM calibration system,the comparison experiments between different calibration systems are carried out.The absolute spectral radiance responsivity of two radiometers was obtained by SCM and tunable laser respectively.The experimental results show that in the range of 700 nm to 900 nm,the maximum deviation of the absolute spectral radiance responsivity was 0.6%,the maximum deviation of the in-band spectral radiance responsivity was 0.4%,and the maximum deviation of the in-band integral responsivity was 0.1%.The calibration uncertainty of the two calibration systems was 1.8%and 0.53%(k=2),respectively.The deviation of the comparison results was within the scope of the calibration uncertainty,which verifies that the SCM calibration system has good system level calibration ability.In the application of SCM calibration system,the relative spectral calibration experiment for polarization remote sensor was set up,the influence factors in the relative spectral responsivity calibration of the remote sensing device were analyzed,the theoretical model of spectral calibration was derived,the system-level calibration method was proposed,the defect of polarization remote sensor spectral calibration is optimized in the traditional mode,and the in-band response non-conformity results obtained in system-level mode are better than 0.6%.The SCM calibration system was successfully applied to the laboratory calibration of the on-board atmospheric corrector,the absolute spectral radiance responsivity and the calibration coefficient in the seven spectral bands of the atmospheric calibrator have been measured.The maximum uncertainty of the whole calibration process is evaluated to be 2.05%,which is better than the 3%-5%uncertainty of using the monochromator in the traditional mode.The results of this paper verify that the SCM calibration system has good system-level calibration ability,and has the advantages of adjustable output spectral bandwidth,more convenient use and maintenance,which can meet the high-precision spectral radiometric calibration requirements of optical remote sensors in the solar reflection spectrum.