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一种基于伪标签的机载SAR深度学习去噪方法

A deep learning denoising method based on pseudo labels for airborne SAR images

  • 摘要: 合成孔径雷达(Synthetic Aperture Rader,简称SAR)成像因其分辨率高、穿透性强、全天候工作等优点,被广泛应用于资源监测、地貌测绘等领域。作为一种干涉测量技术,SAR的成像过程利用多个回波信号的相干叠加增强图像的横向分辨率,但回波信号的相位波动会带来与信号相关的噪声(即散斑噪声),SAR图像的去噪工作一直是领域内的研究重点。SAR的采集平台现主要为星载SAR和机载SAR。在机载条件下,由于物体与平台相对运动更加明显,在同视野的时间帧之间,成像物体位置相比星载条件下有更大的改变,因此,以多时间帧平均生成低噪声图像为指导的去噪方法效果不佳。本文针对机载SAR图像的噪声特点,提出了一种多个零样本子网络模型蒸馏方法实现自监督去噪,一方面充分利用子网络的优秀自适应能力,另一方面通过下采样方法降低SAR图像相邻像素噪声之间存在的相关性,结合一致性损失,保持神经网络对下采样前图像的去噪性能。经验证,此方法相比领域内典型的DIP和ZS-N2N方法,对单帧图像获得了更好的去噪效果。

     

    Abstract: Synthetic Aperture Radar (SAR) imaging is widely used in fields such as resource monitoring and topographic mapping due to its high resolution,strong penetration and all-weather adaptability. As an interferometric measurement technique, SAR utilizes the coherent superposition of multiple reflected signals to enhance the cross-range resolution of images. However, the phase fluctuation of the reflected signal can bring signal-dependent noise, namely speckle noise. The denoising of SAR images has been a hot research focus in the field. The current SAR acquisition platforms mainly include spaceborne SAR and airborne SAR. Under airborne conditions, relative motion between objects and the platform is more obvious, leading to more significant positional changes of imaged objects between time frames in the same field of view. Therefore, the denoising method guided by generating low-noise images by averaging multiple time frames is not suitable. In this paper, we propose a multiple-expert model distillation framework for self-supervised denoising. We leverage the adaptive capacity of multiple experts while mitigating noise correlation between neighboring pixels in SAR images through downsampling. A consistency loss is incorporated to preserve the denoising performance of the original on the original,higher-resolution image. Experimental results demonstrate that this method achieves superior denoising results on airborne SAR images compared to representative methods DIP and ZS-N2N.

     

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