自校准型光谱辐亮度标准光源研究

With the development of ground based, aeronautics-based, aerospace-based solar/atmospheric high precision spectral quantitative remote sensing and quantitative spectroscopy, broad-band standard light source based on blackbody radiation and narrow-band standard light source based on standard detector have been unable to fully meet the requirements in precision or facilitating the application. Therefor, a new concept of self-calibrated spectral radiance standard light source is presented and apply for the development of self-calibrated spectral radiance standard light source. This light source consists of Xenon lamp, spectral tuner, light guide, integrating sphere, Gershun-tube radiometers, etc. The light emitted from the light source is dispersed by the first spectrometer of spectral tuner after passing through the entrance slit. Spectrum is formed on micromirror array. Then the light is dedispersed by the second spectrometer of spectral tuner. Uniform radiance source is realized after introducing the light into integrating sphere with light guide. This standard light source configures both narrow-band and broad-band operating modes through the wavelength selection of the micromirror array, enabling it to be calibrated with narrow-band mode, then use in broad-band mode. The key technical issues to be resolved include the development of spectral tuner using a digital micromirror device (DMD) to select wavelength, the spectral radiance long-term stability of system, the establishment of the narrow-band to broad-band spectral radiance calibration theoretical model, high-precision radiometric calibration, etc. Calibration accuracy of spectral radiance standard light source to be developed is expected to be developed in 0.2%, and the light source spectral radiance uncertainty is expected to be 1%.

随地基、空基、天基太阳/大气高精度光谱定量遥感及定量光谱学的发展，基于黑体辐射的宽带标准光源及基于标准探测器的窄带标准光源在精度或方便应用方面已无法完全满足需要。为此，提出自校准标准光源新概念并申请研制自校准光谱辐亮度标准光源。该光源由氙灯、光谱调谐器、光导、积分球和Gershun管辐射计等组成。光源发出的光，经入射狭缝进入光谱调谐器的第一台谱仪色散，在微镜阵列上形成光谱，再经光谱调谐器的第二台谱仪消色散，经光导引入积分球，形成均匀辐亮度源。通过微镜阵列的波长选择，该标准光源兼有窄带和宽带工作模式，在窄带模式下采用标准探测器定标，在宽带模式下使用。拟解决采用数字微镜装置（DMD）进行波长选择的光谱调谐器的研制、系统光谱辐亮度长期稳定、窄带至宽带模式光谱辐亮度定标理论模型的建立及高精度辐射定标等关键技术问题。拟研制的光谱辐亮度标准光源预期定标精度在0.2%，光源光谱辐亮度不确定度预期为1%。

随地基、空基、天基太阳/大气高精度光谱定量遥感及定量光谱学的发展，基于黑体辐射的宽带标准光源及基于标准探测器的窄带标准光源在精度或方便应用方面已无法完全满足需要。为此，提出自校准标准光源新概念并开展了自校准光谱辐亮度标准光源的研究工作。本项目在国家自然科学基金支持下，完成了自校准标准光源系统的总体方案设计，构建了光谱调谐器实验装置，确定了可编程控制的DMD应用方案。通过微镜阵列的波长选择，自校准标准光源具有窄带和宽带两种工作模式，在窄带模式下采用Gershun管辐射计和CAS光谱辐射计定标，在宽带模式下用于遥感仪器高精度辐射定标。研制了采用单凹面光栅DMD光谱调谐器的自校准标准光源原理样机。该原理样机中氙灯或超连续激光光源发出的光，经前置光学系统汇聚到以单凹面光栅平像场谱仪为主体的DMD光谱调谐器的入射狭缝，经色散在DMD表面形成光谱，经微镜阵列反射后选取的光汇集至积分球内，形成均匀光谱辐亮度光源。研制了采用双平面光栅色散相减Ebert-Fastie型DMD光谱调谐器的自校准标准光源原理样机，具有低杂散光的优点。该原理样机中光源发出的光经聚光镜汇聚于光谱调谐器的入射狭缝，经第一凹面镜准直，经第一平面光栅色散，再经第一凹面镜将入射狭缝光谱像形成于DMD表面。由DMD反射的光再经第二凹面镜准直，经第二平面光栅消色散，再经第二凹面镜将消色散的光聚焦于出射狭缝处。出射狭缝输出的光通过液体光导引入积分球，形成均匀的光谱辐亮度光源。光谱分辨率可达7 nm。研制了Gershun管辐射计和CAS光谱辐射计，开展了自校准光源光谱辐亮度定标研究，进行了不确定度分析。表明自校准光源光谱辐亮度不确定度小于1%，实现了预期的高精度。自校准型光谱辐亮度标准光源可实现在大气光谱辐亮度水平下为遥感仪器定标，为地基、空基和天基定量光谱遥感仪器高精度辐射定标的应用奠定了技术基础。