基于自适应动量估计优化器与空变最小熵准则的SAR图像船舶目标自聚焦算法

李志远; 郭嘉逸; 张月婷; 黄丽佳; 李洁; 吴一戎

doi:10.12000/JR21159

基于自适应动量估计优化器与空变最小熵准则的SAR图像船舶目标自聚焦算法

DOI: 10.12000/JR21159

李志远^{1, 2, 3},
郭嘉逸^{1, 2, 3, ,},
张月婷^{1, 2, 3},
黄丽佳^{1, 2, 3},
李洁^{1, 2, 3},
吴一戎^{1, 2, 3}

1.
中国科学院空天信息创新研究院北京 100190
2.
中国科学院空间信息处理与应用系统技术重点实验室北京 100190
3.
中国科学院大学电子电气与通信工程学院北京 100049

基金项目: 国家自然科学基金(61991421)

详细信息

作者简介:
李志远(1997–)，男，山东人，中国科学院空天信息创新研究院博士研究生，2019年获北京理工大学信息与电子学院学士学位。主要研究方向为深度学习、SAR图像处理与图像质量提升等

郭嘉逸(1989–)，男，河北人，博士，现任中国科学院空天信息创新研究院助理研究员，研究方向为SAR图像深度学习应用、SAR图像与遥感图像复原应用，发表SCI论文10余篇

张月婷(1983–)，女，河北人，博士，现任中国科学院空天信息创新研究院副研究员，研究方向为SAR目标特性、SAR图像与遥感图像应用，发表SCI论文10余篇

黄丽佳(1984–)，女，辽宁人，博士，研究员。2011年在中国科学院电子学研究所获得博士学位，现任中国科学院空天信息创新研究院研究员。主要研究方向为合成孔径雷达信号处理与图像分析

李　洁(1996–)，女，山东人，中国科学院空天信息创新研究院博士研究生，2019年获北京理工大学信息与电子学院学士学位。主要研究方向为微波成像理论与技术、稀疏信号处理等

吴一戎(1963–)，男，安徽人，博士，中国科学院院士，博士生导师，国家杰出青年基金获得者，“百千万工程”国家级人选入选者。主要研究方向为微波成像理论与技术、雷达信号处理与雷达系统等

通讯作者:
郭嘉逸 jyguo@mail.ie.ac.cn

责任主编：杨淑媛 Corresponding Editor: YANG Shuyuan
中图分类号: TN958; TP391
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出版历程
- 收稿日期: 2021-10-28
- 修回日期: 2022-01-05
- 网络出版日期: 2022-01-21
- 刊出日期: 2022-02-28

A Novel Autofocus Algorithm for Ship Targets in SAR Images Based on the Adaptive Momentum Estimation Optimizer and Space-variant Minimum Entropy Criteria

LI Zhiyuan^{1, 2, 3},
GUO Jiayi^{1, 2, 3
, ,},
ZHANG Yueting^{1, 2, 3},
HUANG Lijia^{1, 2, 3},
LI Jie^{1, 2, 3},
WU Yirong^{1, 2, 3}

1.
Aerospace Information Research Institute, Chinese Academy of Science, Beijing 100190, China
2.
Key Laboratory of Technology in Geo-spatial Information Processing and Application System, Chinese Acodemy of Sciences, Beijing 100190, China
3.
School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China

Funds: The National Natural Science Foundation of China (61991421)

More Information

Corresponding author: GUO Jiayi, jyguo@mail.ie.ac.cn

摘要

摘要: 在SAR散焦船舶图像中，部分船舶目标的散焦现象具有沿距离向空变的特性。针对此类散焦船舶目标，该文提出了一种基于自适应动量估计优化器与空变最小熵准则的SAR图像船舶目标自聚焦算法，该算法直接对复图像进行处理，可以实现对任意阶次相位误差的补偿。在仿真数据和GF-3数据上的实验结果表明，所提算法可以有效地实现SAR图像空变散焦船舶目标自聚焦，聚焦后的船舶图像在图像熵与对比度上都有所改善，且算法聚焦速度有很大提升。
- 合成孔径雷达 /
- 船舶目标 /
- 自适应动量估计优化器 /
- 空变最小熵 /
- 自聚焦算法
Abstract: In SAR defocused ship images, the defocusing phenomenon of some ship targets is space-variant along the distance. In this context, a novel autofocus algorithm combining the adaptive momentum estimation optimizer and space-variant minimum entropy criteria is proposed to address these defocused ship targets. The algorithm can directly process complex images and compensate for any order phase errors. The effectiveness of the proposed method is proved by the experimental results on the simulation data and GF-3 data. Moreover, the entropy and contrast of the refocused image have been improved, and the focusing speed of the algorithm has been greatly enhanced.
- Synthetic Aperture Radar (SAR) /
- Ship target /
- Adaptive momentum estimation optimizer /
- Space-Variant Minimum Entropy (SVME) /
- Autofocus algorithm

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图 1 添加不同阶次相位误差时方位回波信号压缩结果

Figure 1. The compression results of azimuth echo signal when adding different order phase error

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图 2 GF-3 空变散焦船舶目标

Figure 2. GF-3 space-variant defocused ship target

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图 3 算法流程图

Figure 3. Flowchart of the proposed algorithm

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图 4 空变散焦数据仿真算法流程图

Figure 4. Flowchart of space-variant defocused data simulation algorithm

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图 5 仿真空变散焦船舶图像

Figure 5. Simulated space-variant defocused ship images

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图 6 GF-3空变散焦船舶图像

Figure 6. GF-3 space-variant defocused ship images

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图 7 在仿真数据上的自聚焦结果(a1—d1：GF-3原始船舶图像，a2—d2：仿真的空变散焦船舶图像，a3—d3：算法1船舶图像聚焦结果，a4—d4：算法2船舶图像聚焦结果，a5—d5：算法3船舶图像聚焦结果，a6—d6：算法4船舶图像聚焦结果，a7—d7：算法5船舶图像聚焦结果)

Figure 7. Autofocus results on simulated data (a1—d1: the ground truth obtained in GF-3UFS mode, a2—d2: the simulated space-variant defocused ship images, a3—d3: the ship images refocused by algorithm 1, a4—d4: the ship images refocused by algorithm 2, a5—d5: the ship images refocused by algorithm 3, a6—d6: the ship images refocused by algorithm 4, a7—d7: the ship images refocused by algorithm 5)

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图 8 仿真数据自聚焦结果图像熵与对比度可视化

Figure 8. Visualization of image entropy and contrast of autofocus results on simulated data

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图 9 在GF-3数据上的自聚焦结果(a1—d1：GF-3超精细条带模式下获得的空变散焦船舶图像，a2—d2：算法1船舶图像聚焦结果，a3—d3：算法2船舶图像聚焦结果，a4—d4：算法3船舶图像聚焦结果，a5—d5：算法4船舶图像聚焦结果，a6—d6：算法5船舶图像聚焦结果)

Figure 9. Autofocus results on GF-3 data (a1—d1: the space-variant defocused ship images obtained in GF-3UFS mode, a2—d2: the ship images refocused by algorithm 1, a3—d3: the ship images refocused by algorithm 2, a4—d4: the ship images refocused by algorithm 3, a5—d5: the ship images refocused by algorithm 4, a6—d6: the ship images refocused by algorithm 5)

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图 10 GF-3数据自聚焦结果图像熵和对比度可视化

Figure 10. Visualization of image entropy and contrast of autofocus results on GF-3 data

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图 11 算法3中补偿的相位误差

Figure 11. The compensated phase error by algorithm 3

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表 1 使用Adam优化器估计相位误差系数伪代码

Table 1. Pseudo code for estimating phase error coefficients using Adam optimizer

输入：图像I 　输出：自聚焦图像$ f\left( {\boldsymbol I, \boldsymbol \alpha } \right) $
初始化：学习率$ \varepsilon $，矩估计的指数衰减速率$ {\gamma _{\text{1}}} $, $ {\gamma _{\text{2}}} $，相位误差系　　　　　数$\boldsymbol \alpha = \left[ { {\alpha _{\text{1} } },{\alpha _{\text{2} } },\cdots,{\alpha _{{i} } } } \right]$，用于数值稳定的小常数$ \delta $，梯度　　　　　1阶矩和2阶矩变量$ {\boldsymbol s}, {\boldsymbol r} $，迭代次数$ t $。
While 图像熵未收敛 do
计算图像熵梯度：$\boldsymbol g \leftarrow {\nabla _\alpha }L\left( {f\left( { {\boldsymbol I}, {\boldsymbol \alpha} } \right)} \right)$
更新有偏1阶矩估计：$ {\boldsymbol s} \leftarrow {\gamma _1}{\boldsymbol s} + \left( {1 - {\gamma _1}} \right){\boldsymbol g} $
更新有偏2阶矩估计：$ {\boldsymbol r} \leftarrow {\gamma _2}{\boldsymbol r} + \left( {1 - {\gamma _2}} \right){\boldsymbol g} \cdot {\boldsymbol g} $ (‘$ \cdot $’: 逐元素　　　相乘) 　　　修正1阶矩偏差：$\hat {\boldsymbol s}{\rm{ = } }\displaystyle\frac{\boldsymbol s}{ {1 - \gamma _1^t} }$
修正2阶矩偏差：$\hat {\boldsymbol r}{\rm{ = } }\displaystyle\frac{\boldsymbol r}{ {1 - \gamma _2^t} }$
更新相位误差系数：${\boldsymbol \alpha} = {\boldsymbol \alpha} - \displaystyle\frac{\varepsilon }{ {\sqrt {\hat {\boldsymbol r} } + \delta } }\hat {\boldsymbol s}$
end while

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表 2 GF-3超精细条带图像参数

Table 2. The detailed information of GF-3 UFS SAR images

参数	值
成像模式	UFS
产品类型	SLC
产品级别	L1A
轨道模式	ASC
极化方式	HH/HV
地距分辨率(m)	2.5～5.0
方位向分辨率(m)	3
幅宽(km)	30
像元间距[Rg×Az](m)	1.124～1.728
入射角(°)	39.51～41.08

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表 3 仿真数据上的算法速度对比

Table 3. Algorithm speed comparison on simulation data

算法	运行时间(s)
算法	图像a	图像b	图像c	图像d
算法1	101.35	81.25	96.25	94.35
算法2	32.16	21.53	32.45	32.49
算法3	2.31	1.73	1.75	2.36
算法4	0.69	0.69	0.57	0.68
算法5	0.25	0.23	0.25	0.18

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表 4 GF-3数据上的算法速度对比

Table 4. Algorithm speed comparison on GF-3 data

算法	运行时间(s)
算法	图像a	图像b	图像c	图像d
算法1	92.25	81.11	205.56	170.38
算法2	10.73	10.73	42.39	32.28
算法3	1.75	1.76	4.61	2.88
算法4	0.71	0.69	0.70	0.73
算法5	0.23	0.24	0.23	0.24

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