针对光谱仪在测量窄带宽光源的光谱分布时出现的光谱变形现象, 提出了一种带宽修正方法—七点修正方法。 首先, 利用泰勒级数和相关的导数公式, 得到了七点修正公式的数学解析式; 其次, 用光谱线型为正弦函数的模拟光谱对七点修正法进行验证, 采用正弦函数来模拟真实光谱, 通过光谱仪的带宽函数计算出测量值, 然后应用七点修正公式, 对测量值进行修正; 最后利用中心波长为365 nm的LED光源对七点修正法进行了实验验证, 用双光栅单色仪来测量LED光源的光谱辐射照度, 光谱仪带宽分别选为5与0.5 nm, 将七点修正公式应用于测量值, 得到修正值。 模拟结果表明: 在选定的模拟条件下, 修正后得到的中心波长处的峰值可以达到真实值的99%以上; 实验结果表明: 修正后中心波长处的峰值可以达到真实值的95%以上。 由模拟结果和实验结果可知, 七点修正法与三点修正法和五点修正法相比, 修正效果有明显提升, 这种带宽修正方法可以广泛应用在光谱测量领域。

The finite bandwidth of spectroradiometers always causes significant errors when the measured light source has a narrow bandwidth compared to that of spectroradiometers. In order to solve this problem, an improved correction approach which is called seven-point correction approach is proposed. Firstly, the seven-point correction formula is obtained with Taylor’s series and related derivative formula. Secondly, the effect of seven-point formula is validated through a simulated spectrum with a sine function shape. Considering the sine function as true spectrum, we calculate the measured spectrum with the bandpass function of spectroradiometers. We also correct the measured spectrum with the seven-point formula. At last, we validate the seven-point formula experimentally with a LED lamp whose center wavelength is 365 nm. Using a double grating monochromator, we measure the irradiance of LED lamp when the bandwidth of spectroradiometer is 5 and 0.5 nm. We also obtain the corrected spectrum by applying seven-point formula to measured spectrum. The simulated results show that, the corrected value at the center wavelength could be above 99% of the true value. The experimental results show that, the corrected value at the center wavelength could reach above 95% of the true value. Above all, the proposed seven-point approach has an improved correction effect compared with three-point and five point approach. This correction approach could be widely applied in the field of spectrum measurement.