基于地-气间辐射模型的航天相机自动调光系统

Automatic Exposure System of Spaceborne Camera Based on Land-Atmosphere Radiative Transfer Model

在航天相机的成像过程中,拍摄场景的亮度随着地表目标和大气环境的变化而发生改变,为了保证航天相机输出理想的图像,提出了基于地-气间辐射模型的航天相机自动调光方法。根据地-气间辐射传输特性建立航天相机入瞳处辐照度模型,通过分析大气气溶胶对遥感成像的影响,对该模型进行了改进,并在此基础上提出了航天相机自动调光方法。航天相机自动调光首先根据总辐照度以及地面目标辐照度占总辐照度的比例对自动调光参数进行调节,目的是尽可能提高地面目标信息量,然后根据大气气溶胶光学厚度确定自适应拉普拉斯滤波的参数,增强遥感图像的细节。由实验结果可以看出,自动调光增加了遥感图像的信息量,增强了图像对比度,航天相机的成像质量得到了明显地提高。

In the process of spaceborne camera imaging, the brightness of the scene changes with atomosphere and ground target. In order to obtain ideal images, an automatic exposure method based on land-atmosphere radiative transfer model for spaceborne camera is proposed. The irradiance model is established at the pupil of spaceborne camera according to the land-atmosphere radiation transmission characteristics. After analyzing the influence of atmospheric aerosol in remote sensing image, improving the irradiance model, and on this basis an automatic exposure is proposed. Through calculating the total irradiance and the ratio of ground target irradiance in the total irradiance, and adjusting the automatic exposure parameter of spaceborne camera to improve ground targets information as much as possible. Then the adaptive Laplace filter parameters are determined according to the atmospheric aerosol optical thickness, in order to enhance the details of the remote sensing images. The experimental results shows that the quality of the remote sensing images are improved greatly, on account of promoting information and contrast of remote sensing images with the proposed method.