非均匀扩展光源辐射定标特性分析

Study on the Characteristics of Radiance Calibration Using Nonuniformity Extended Source

积分球和漫反射板是定标常用的扩展光源,其非均匀性在不同条件下会对定标产生不同的影响。该文根据辐射传输理论和定标原理,建立数学模型,以均匀性比较差的灯-板定标系统为例,计算CCD不同像元上的辐照度和定标系数,并以理想情况和非理想情况下定标系数矩阵的相关性作为评价函数,分析非均匀性对定标的影响。结果表明,由于扩展光源的非均匀性,观测角度和光轴与漫反射板交点的位置对定标系数的影响比较大,而观测距离的影响比较小;在不同观测角度下,可以找到一个偏离值使得定标结果最接近理想结果。因此用灯-板定标系统标定成像光谱仪时根据观测角度选择合适的偏离值,可以减小定标误差。

Integrating sphere and diffuser are always used as extended source, and they have different effects on radiance calibra- tion of imaging spectrometer with parameter difference. In the present paper, a mathematical model based on the theory of radia- tive transfer and calibration principle is founded to calculate the irradiance and calibration coefficients on CCD, taking relatively poor uniformity lights-board calibration system for example. The effects of the nonuniformity on the calibration was analyzed, which makes up the correlation of calibration coefficient matrix under ideal and unideal situation. The results show that the non- uniformity makes the viewing angle and the position of the point of intersection of the optical axis and the diffuse reflection plate have relatively large effects on calibration, while the observing distance＇ s effect is small; under different viewing angles, a devia- tion value can be found that makes the calibration results closest to the desired results. So, the calibration error can be reduced by choosing appropriate deviation value.