结合亮度估计的航空相机曝光融合方法

Multi-exposure fusion based on illumination estimation for aerial cameras

航空相机CCD(charge coupled device)动态范围有限,在高动态范围场景下通过调节曝光量的方式不能保证图像中所有部分都准确曝光.为了解决这一问题,在复小波域内结合亮度估计对航空多曝光图像进行融合.首先,在相同高动态场景下调节曝光参数曝光多次,获得这一场景的多曝光图像序列,使用基于SURF(speeded up robust feature)算法的小范围快速配准策略对其配准.然后估计它们的亮度情况,在复小波域内,根据亮度情况分配权值对低频分量进行融合,采用加权的区域能量最大法对高频分量进行融合.最后,将融合后的低频分量和高频分量经逆变换得到结果.得到的结果在空间频率、图像清晰度、平均梯度和边缘信息保持度方面表现较好.实验结果表明:在复小波域内结合亮度估计的方法得到的图像亮度适宜,无重影现象且较好地保持了源图像中的细节信息,该方法可适用于多种高动态场景,满足航空相机的工作需求.

Due to the aerial camera CCD（ charge coupled device） existing limited dynamic range,it cannot reveal all the details in a high-dynamic range scene. To solve this problem,this paper presents a multi-exposure fusion method based on illumination estimation in complex wavelet domain. First,a set of multi-exposure images are obtained by multiple expose in the same scene,and register these images using the fast small-area registration strategy based on SURF（ speeded up robust feature）. Then the illumination of these images is estimated. In complex wavelet domain,weights according to the illumination are assigned to the low component for fusion; and weighted regional energy based fusion rule is adopted for high component fusing. Finally,fused image is acquired by subjecting the low and high component to inverse DT-CWT. The results obtained by this method are performing well in spatial frequency,figure definition,average gradient and edge preservation information. Experiments demonstrate that images obtained by this paper have appropriate brightness and preserve the details and edges effectively. It is suitable for varied high dynamic range scenes and conforms to the requirements of aviation investigation.