超光谱成像仪的精细光谱定标

Precise spectral calibration for hyperspectral imager

为了精细标定棱镜色散超光谱成像仪1024×80光谱像元的中心波长和响应带宽,建立了一套光谱定标装置,提出了实现1nm光谱定标精度的定标方法。首先,介绍了产生谱线弯曲与谱线倾斜的原因,确定了精细光谱定标的方法和数据处理算法;然后,利用光谱定标装置测定了全部光谱响应像元的离散单色光响应值,利用高斯方程拟合了相对光谱响应曲线;最后,建立了中心波长矩阵表和带宽矩阵表,采用多项式拟合算法确定了空间视场像元的色散方程和光谱通道谱线弯曲方程,实验测定了温度变化谱线漂移结果。另外,还对光谱定标精度对辐射定标精度的影响进行了分析。光谱定标结果表明:超光谱成像仪的光谱定标精度达到了±1nm,各谱段带宽平均为8.75nm;色散方程及谱线弯曲与设计结果相符,谱线弯曲值为14～19nm,平均值为17nm;1nm的定标精度对辐射定标精度的影响分别小于1%(3000K黑体)和0.25%(6000K黑体),满足超光谱成像仪1nm光谱定标精度的要求。

In order to precisely calibrate the center wavelength and bandwidth of 1024 ×80 spectral pixels of a prism-dispersive hyperspectral imager, a spectral calibration facility is established, and a spectral calibration method to realize 1 nm wavelength accuracy is presented. Firstly, the spectral line bend and spectral line tilt are introduced, and the precise spectral calibration method and data processing algorithms are determined. After the discrete monochrome response values of all spectral pixels are measured with the spectral calibration facility, the relative spectral response curves are fitted with Gauss function. Finally, the center wavelength matrix and bandwidth matrix are established, the dispersive equations of different spatial pixels and the spectral line bend equations of different spectral channels are given with a polynomial fitting, and the spectral line deviation with circumstance temperature variation is experimentally measured. Furthermore, the effect of spectral calibration accuracy on the radio metric calibration accuracy is discussed. Experimental results indicate that the spectral calibration accuracy reaches 1nm,and the average bandwidth of all pixels is 8.75 nm. The dispersive equation and the spectral line bend are coincident with design values well, in which the spectral line bend value is between 14 and 19 nm and the average is 17 nm. Moreover,the 1 nm center wavelength accuracy can cause less than 1% radiometric calibration deviation for a 3 000 K blackbody calibration source, and 0.25% for a 6 000 K blackbody calibration source. These results can satisfy the spectral calibration requirements of 1 nm wavelength accuracy.