低温辐射计光功率修正因子测试与分析

Optical Power Correction Factor Test and Analysis of Cryogenic Radiometer

为了确保低温辐射计测量准确度,开展了低温辐射计光功率修正因子的研究。介绍了低温辐射计测试系统光路结构和光功率的测量过程。分析了影响低温辐射计光电加热等效替代的四个主要因素。利用搭建的影响因子测试装置,对布儒斯特窗口透过率、杂散光和黑体腔吸收率三个影响因子进行了测试;采用有限元分析方法,对光电加热不等效性因子进行了仿真计算。测试和仿真计算了自主研制低温辐射计光电加热等效替代修正因子,结果显示,布儒斯特窗口在632.8 nm处的透过率为0.996817,杂散光修正因子为0.999013,黑体腔吸收率为0.999950,光电不等效性修正因子为1.009240±0.000010。该研究结果可用于低温辐射计的修正,对低温辐射计各功能模块的设计、测量不确定度的提高以及低温辐射计的研制具有一定参考价值。

Optical radiation measurement generally refers to the use of basic measurement technology to establish a direct or indirect connection between the measured optical radiation or photometric parameters and the fundamental physical constants or physical quantities with low measurement uncertainty,so as to improve the reproducibility or measurement level.In the actual substitution process,in order to ensure the measurement accuracy,the factors affecting the equivalent substitution of photoelectric heating need to be corrected.At present,most relevant studies at home and abroad only test and simulate the factors affecting the equivalent substitution of photoelectric heating of cryogenic radiometer from a single aspect,and the technical means adopted have some defects.The 41st Research Institute of China Electrics Technology Group Corporation has developed cryogenic radiometers.In order to ensure the measurement accuracy of cryogenic radiometer,the research on the optical power correction factor of cryogenic radiometer is carried out.The optical path structure of the cryogenic radiometer test system and the measurement process of optical power are introduced.The four main factors affecting the equivalent substitution of photoelectric heating of cryogenic radiometer were analyzed.Brewster window transmittance,stray light,absorbing cavity absorptivity and photoelectric heating non-equivalence are considered to be important sources of uncertainty of cryogenic radiometer.Brewster window transmittance,stray light and blackbody cavity absorption the three influencing factors were tested by using the influencing factor test facility,and the photoelectric heating non-equivalence factor is simulated and calculated by finite element analysis.Aiming at the transmittance and stray light correction factor of Brewster window,the beam alignment and test chamber are used for on-line measurement.With the test chamber,the stray light radiation is indirectly calculated by testing the transmittance of the incident light through the off-axis parabolic mirror,which is similar to the transmittance test of the Brewster window.The ratio of the power of the front and the rear of the parabolic mirror is the stray light correction factor.Because through hole diameter of the parabolic mirror is smaller than the blackbody cavity diameter,all the light that does not pass through the through hole is regarded as stray light,and all the light that passes through the through hole will enter the absorption cavity.At the same time,the Gaussian beam energy distribution after spatial filtering is analyzed.It is proposed to obtain the stray light distribution and energy by measuring the transmittance of incident light through off-axis parabolic mirror.Finally,the transmittance of Brewster window is 0.996817,stray light correction factor 0.999013.In addition,the spectral absorptivity of the black body cavity is analyzed and tested,and the factors affecting the absorptivity of the black body cavity are analyzed.The simulated and measured results are consistent.The absorptivity of the black body cavity at 632.8 nm is 0.999950.Additionally,the heat transfer model of blackbody cavity is constructed by finite element analysis method.Firstly,the three-dimensional mathematical model of blackbody cavity assembly is constructed by SolidWorks,and the thermodynamic characteristic parameters of materials at temperature of 6.5 K are added,and then the established mathematical model is imported into SolidWorks simulation for thermodynamic simulation.The heating power,between 100μW to 1 mW,stepped 100μW,is applied to the light heating area and the electric heating area,respectively.The photoelectric heating non-equivalence of cryogenic radiometer under different heating power is simulated and analyzed.The simulation results show that the difference of photoelectric heating non-equivalence of cryogenic radiometer under different heating power is slight,and the photoelectric non-equivalence factor of the cryogenic radiometer is 1.009240±0.000010.The research results provide certain references for the optimization design and correction factor test of each functional module of cryogenic radiometer.