海天背景多光谱成像特性仿真

采用红外传感器观测海面,若观测天顶角较大,则视场中会同时出现海面与天空背景.通过计算传感器每一像素单元接收的辐射强度,可以得到海天背景多谱段光学图像.为了计算假定海况条件下海面随观测方向变化的反射辐射,基于几何光学原理修正了传统海面辐射特性模型.由于路径长度随传感器垂直视场变化,此时大气对辐射传输的影响十分显著.天光及水平路径辐射采用改进的大气辐射传输模型计算.该模型具有更高的光谱分辨率,适用于多谱段成像仿真.基于给出的海面辐射特性模型和大气辐射传输模型,分别仿真了不同时刻不同观测角下可见光、中波红外和长波红外的海天背景辐射图像.仿真结果符合物理原理,与实测图像的对比验证了新模型的可靠性.

Multispectral imaging simulation of sea-sky background scene

When an infrared sensor observes sea surfaces at a high zenith angle of the sensor, both sea and sky backgrounds are in the field of view (FOV). By calculating the radiance received by each pixel of the sensor, multispectral optical images of sea-sky background can be obtained. To calculate the reflected radiance of sea surfaces varying with viewing direction under given sea conditions, traditional sea surface radiative characteristic model was modified based on geometrical optics theory. Since the length of transmission path varies with vertical FOV, the effects of atmosphere on radiative transfer are obvious. The radiance of sky light and horizontal path was calculated using a modified atmospheric radiative transfer model. The modified model has higher spectral resolution and is suitable for multispectral imaging simulation. With the improved models, several sea-sky background images were simulated at different time and viewing angles covering the visible up to long wavelength infrared spectral bands, separately. Simulation results are coincident with physical principles. The comparison between simulated and measured images validates the reliability of the new model.