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传统一元定标法测量红外天空亮度,面临诸多困难,如测量易受环境温度变化影响、仪器动态范围不足等。提出增加积分时间为自变量的二元定标模型,解决了仪器动态范围不足的问题;然后通过改变环境温度的系列实验,掌握了二元定标模型中仪器辐射随环境温度变化的规律;基于此,提出再增加环境温度为自变量的三元定标模型。实验数据表明,三元模型与实测数据拟合程度很高,相关系数为1.000,模型参数a、b、d,95%置信度的相对不确定度均小于0.82%,当环境保持某一温度不变时,三元模型退化为二元模型,各模型参数稳定,其相对偏差小于0.6%。最后,通过红外天空亮度实测,验证并比较了三元和二元定标模型;结果表明,三元模型定标测量法使用条件宽泛,既扩大了仪器动态范围,又不受环境温度变化影响;更重要的是,不再需要现场定标,提高了测量精度和测试效率。
The traditional univariate calibration method to measure the brightness of infrared sky faces many difficulties, such as the measurement of the impact of changes in ambient temperature, lack of dynamic range of the instrument. A binary calibration model is proposed to increase the integral time as an independent variable, which solves the problem of insufficient dynamic range of the instrument. Then, the series of experiment of changing the ambient temperature is used to grasp the law of the instrument radiation variation with the ambient temperature in the binary calibration model. In this case, a ternary calibration model with increasing ambient temperature as an independent variable is proposed. The experimental data show that the fitting degree between the ternary model and the measured data is very high, and the correlation coefficient is 1.000. The relative uncertainties of model parameters a, b, d, 95% confidence are all less than 0.82%. When the environment keeps a certain temperature When changing, the ternary model degenerates into a binary model, the parameters of each model are stable, and the relative deviation is less than 0.6%. Finally, the ternary and binary calibration models were validated and compared by measuring the brightness of the infrared sky. The results showed that the calibration conditions of the ternary model were wide and not only expanded the dynamic range of the instrument but also not affected by the change of ambient temperature. More importantly, on-site calibration is no longer needed, improving measurement accuracy and testing efficiency.