基于半监督学习的SAR目标检测网络

现有的基于卷积神经网络(CNN)的合成孔径雷达(SAR)图像目标检测算法依赖于大量切片级标记的样本，然而对SAR图像进行切片级标记需要耗费大量的人力和物力。相对于切片级标记，仅标记图像中是否含有目标的图像级标记较为容易。该文利用少量切片级标记的样本和大量图像级标记的样本，提出一种基于卷积神经网络的半监督SAR图像目标检测方法。该方法的目标检测网络由候选区域提取网络和检测网络组成。半监督训练过程中，首先使用切片级标记的样本训练目标检测网络，训练收敛后输出的候选切片构成候选区域集；然后将图像级标记的杂波样本输入网络，将输出的负切片加入候选区域集；接着将图像级标记的目标样本也输入网络，对输出结果中的正负切片进行挑选并加入候选区域集；最后使用更新后的候选区域集训练检测网络。更新候选区域集和训练检测网络交替迭代直至收敛。基于实测数据的实验结果证明，所提方法的性能与使用全部样本进行切片级标记的全监督方法的性能相差不大。

SAR Target Detection Network via Semi-supervised Learning

The current Synthetic Aperture Radar (SAR) target detection methods based on Convolutional Neural Network (CNN) rely on a large amount of slice-level labeled train samples. However, it takes a lot of labor and material resources to label the SAR images at slice-level. Compared to label samples at slice-level, it is easier to label them at image-level. The image-level label indicates whether the image contains the target of interest or not. In this paper, a semi-supervised SAR image target detection method based on CNN is proposed by using a small number of slice-level labeled samples and a large number of image-level labeled samples. The target detection network of this method consists of region proposal network and detection network. Firstly, the target detection network is trained using the slice-level labeled samples. After training convergence, the output slices constitute the candidate region set. Then, the image-level labeled clutter samples are input into the network and then the negative slices of the output are added to the candidate region set. Next, the image-level labeled target samples are input into the network as well. After selecting the positive and negative slices in the output of the network, they are added to the candidate region set. Finally, the detection network is trained using the updated candidate region set. The processes of updating candidate region set and training detection network alternate until convergence. The experimental results based on the measured data demonstrate that the performance of the proposed method is similar to the fully supervised training method using a much larger set of slice-level samples.