为了研究被测目标在氧气A带的自发射光谱与透射率的关系, 根据透射率的计算方法, 提出了采用偏最小二乘回归法对氧气A带的光谱进行基线拟合, 搭建了实验系统, 验证了该方法拟合基线的准确度。首先, 以黑体辐射理论为依据, 给出氧气A带平均透射率计算方法, 以实际被测目标光谱为研究对象, 以带外数据为依据, 利用偏最小二乘法拟合被测目标在氧气A带的基线。为提高拟合精度, 剔除了测量奇异点, 并利用基线拟合不确定度来评价偏最小二乘回归法拟合基线的准确度。为了验证该方法的准确性, 以卤素灯为光源, 在0～130 m范围内, 获得不同距离处的光谱曲线, 以及相同距离不同分辨率下的光谱曲线, 将各种曲线分别进行基线拟合, 分析各自的标准偏差。结果表明, 同一距离处不同分辨率下的平均标准偏差为0.23%, 随着分辨率的降低, 基线拟合不确定度变小, 信噪比增大; 基线拟合不确定度还与测试设备的分辨率有关, 分辨率越高, 带外信息基线拟合不确定度越大, 反之, 带外基线拟合不确定度越小。

In order to research the relation between self-emission spectrum and transmittance of target at oxygen A-band, the method for fitting the baseline of oxygen A-band spectrum based on the partial least square regression (PLSR) is proposed according to the transmittance calculation method. The experimental system is set up to verify the accuracy of baseline fitting. Firstly, the calculation method of oxygen A-band average transmittance is given according to the blackbody radiation theory. The spectrum of the target to be measured is used as study object. The PLSR is used to fit the baseline of the target to be measured at oxygen A-band according to the out-of-band data. For the sake of improving the fitting accuracy, the singular point of measurement is eliminated. The baseline fitting uncertainty is used to evaluate the fitting accuracy of PLSR. In order to verify the accuracy of this method, the spectra with different distances and different resolutions at the same distance is measured in the range of ~130 m using the halogen light. These spectra are fitted and each standard deviation is analyzed. The results show that the average standard deviation is 0.23% with different resolutions at the same distance. The baseline fitting uncertainty becomes smaller and signal to noise ratio is increased with the resolution reducing. In addition, the baseline fitting uncertainty is related to the resolution of the test equipment. The higher the resolution is, the larger the uncertainty of out-of-band data baseline fitting becomes, whereas, the smaller the out-of-band baseline fitting becomes.