采用国际前沿的大口径高温固定点黑体新技术,中国计量科学研究院NIM(National Institute of Metrology)组建了大口径钨碳-碳WC-C高温固定点黑体辐射源,在3 020.11 K的融化点温度,实现了250～2 500 nm光谱辐射照度、相关色温和分布温度基准的量值复现.这是国际上首次将大口径高温固定点黑体技术成功应用于光谱辐射度基准复现领域.针对大口径固定点黑体熔化温坪曲线的特点、以及测量期间温坪曲线中间部分缺失的问题,提出了固定点熔化温坪拐点温度计算新方法,重构了缺失的熔化温坪曲线.采用光谱比较法,通过双光栅光谱比较测量系统将黑体的量值传递至光谱辐射照度副基准灯组,完成光谱辐射照度基准量值的复现和保存.新的量值复现方法将黑体温度的测量不确定度减小为0.36 K,缩短了量传链,实现光谱辐射照度最佳测量不确定度0.25％(k=2).在250～2 500 nm,基于固定点新方法和传统变温黑体法进行量值复现的平均偏差为0.42％,将两种方法相结合,最终实现我国光谱辐射照度基准的测量不确定度(k=2)为:250～400 nm,Urel=1.9％～0.43％;400～1 000 nm,Urel=0.43％～0.25％;1 000～2 200 nm,Urel=0.25％～0.76％;2 200～2 500 nm,Urel=0.76％～2.4％.基于固定点黑体的光谱辐射照度量值复现技术已经应用于遥感仪器的辐射定标,用于提升仪器的测量准确度.
A New Method for Realization National Primary Scale of Spectral Irradiance Based on Large Area High Temperature Fixed Point Blackbody
With the new technology of large area high temperature fixed point,a 14 mm diameter WC-C high temperature fixed point blackbody source was established at NIM.National primary scales of spectral irradiance in the wavelength range from 250 to 2 500 nm,correlated color temperature and distribution temperature were realized at 3 020.11 K.This is the first time that the large area high temperature fixed point blackbody technology has been successfully applied to the field of spectral radiometry.A selective multiple fit methods for calculating the point of inflection temperature of fixed pointmelting temperature plateau was proposed to solve the fluctuation problems of large diameter fixed point blackbody temperature plateau curve.The Akima fitting method was used to restore the missing part of the melting plateau curve.Using a double grating spectral comparison measurement system,a halogen tungsten lamps realized and preserved the spectral irradiance scale.Measurement uncertainty of the temperature of the blackbody was reduced to 0.36 K using the new method,and the traceability chain was shortened.The best measurement uncertainty of spectral irradiance is 0.25％(k=2).Spectral irradiance was realized respectively based on fixed point and variable temperature blackbody,and the average divergence between the two methods is 0.42％from 250 to 2 500 nm.By combining the two methods based on fixed-point blackbody and variable temperature blackbody,the expanded uncertainty of spectral irradiance national primary scale was realized as 1.9％at 250 nm,0.43％at 400 nm,0.25％at 1 000 nm,0.76％at 2 200 nm,and 2.4％at 2 500 nm respectively.The spectral irradiance scale realization technology based on fixed point blackbody has been applied to improve the calibration accuracy of the remote sensing spectroradiometers.
Spectral irradianceFixed point blackbodyVariable temperature blackbodyNational primary standardMeasurement uncertainty
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