光谱移位对成像光谱仪辐射测量的影响

Effects of spectral position offset on radiance measurement of imaging spectrometer

棱镜色散成像光谱仪由于光谱弯曲或者装调等原因会使探测器上产生一定的光谱移位,为了研究光谱移位对系统采集到的光谱辐射能量的影响,首先给出探测器像元采集辐射能量的表达式。再结合棱镜色散成像光谱仪在短波红外(1.0～2.5μm)谱段的光谱采样特性,计算当光谱偏离量为0.01d、0.1d和0.5d(d为探测器像元尺寸)时,系统采集到的辐射能量与没有光谱偏离情况下系统采集到的辐射能量的归一化差值。结果表明:探测器上的光谱偏离导致系统辐射测量精度发生变化,与没有光谱偏离的情况相比,系统采集到的光谱辐射能量在大气吸收带的边缘出现了明显的偏差,且差值随光谱偏离量的增大而增大。当光谱分辨率提高时,一些较弱的吸收峰附近也会出现明显的辐射能量偏差。光谱分辨率为10nm,对于0.1d的光谱偏离量,归一化的辐射能量偏差PV值达到0.011;对于0.5d的光谱偏离量,归一化的光谱偏离量PV值达到0.04。相对能量偏差达到50%以上。实际应用中必须校正由于光谱移位给辐射能量采集带来的偏差,以满足成像光谱仪光谱辐射测量一致性的要求。

Spectral curvature brings the position offset of spectral line on focal plane array detector, which affects the acquired radiant signal by imaging spectrometer with prism dispersion.The expression of acquired signal by detector pixel was given,the normalized error of acquired signal was calculated, and the dispersive spectrumsampling characteristics of imaging spectrometer was combined to calculate the normalized error of acquired signal between with 0.01d, 0.1d, 0. 05d offset （d is pixel dimension）,and without spectral curvature offset in SWIR （1.0-2.5 μm）. The results indicate that spectrum offset of detector results in changed measurement accuracy, compared with no spectral curvature,the scene radiant signal acquired by imaging spectrometer with spectral curvature exhibits distinct error at the edges of atmospherical absorption bands.And the normalized signal errors increase along with the spectral offset. When spectral resolution increases,there is distinct signal errors near some weak atmospherical absorption peaks.When the spectral resolution was 10 nm, for O.ld spectral offset, the PV of the normalized error of the measured signal was 0.011; for the 0.5d spectral offset, the PV of the normalized error of the measured signal was 0.04, the relative error of the measured signal could be above 50%. In the actual application, the radiance error induced by spectral position offset must be adjusted to satisfy the requirement of the consistency of spectral radiance measured by imaging spectrometer.