Two-step phase unwrapping based on swin-UNet-denoise and least square method
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摘要: 相位解包裹在众多领域应用中都占有重要地位,但总会受到噪声的影响,尤其是散斑噪声。为了去除散斑噪声对包裹相位图的影响,并从中恢复出实际的相位值,采用两步法进行了理论分析和实验论证,从不同程度散斑噪声包裹的相位中恢复出绝对相位。以swin-UNet-denoise网络为基础,将swin block中的归一化层后置,并用余弦相似度计算注意力值,然后将相对位移偏移替换为对数位置偏移,并在上采样模块融合反卷积层以此提升网络的去噪能力;将去噪结果通过最小二乘法解包裹,再通过中值滤波获得绝对相位。结果表明,结构相似度为99.77%,峰值信噪比为39.98,均方根误差为0.4864,平均绝对误差为0.4302。所有网络只在300组仿真数据集上进行训练验证,证明即使在小样本的条件下,该研究也能为更快速、更高效、更准确地实现带有散斑噪声的相位解包裹提供参考。Abstract: Phase unwrapping plays an important role in many applications, but it is always affected by noise, especially speckle noise. In order to remove the effect of speckle noise on the wrapping phase diagram, the actual phase value was recovered from it. The two-step method was used to make theoretical analysis and experimental demonstration, and the absolute phase was recovered from the phase covered by speckle noise in different degrees. In the first step, based on the swin-UNet-denoise network, the normalized layer in swin block was set back, and the attention value was calculated by cosine similarity. Then, the relative displacement offset was replaced by logarithmic position offset, and the deconvolution layer was fused in the upsampling module to improve the denoising ability of the network. In the second step, the denoising result was unwrapped by least square method, and then the absolute phase was obtained by median filtering. The results show that the structural similarity is 99.77%, the peak signal-to-noise ratio is 39.98, the root-mean-square error is 0.4864, and the average absolute error is 0.4302, respectively. In addition, all the networks are only trained and verified on 300 simulation data sets, which proves that the research can provide a reference for faster, more efficient and accurate phase unwrapping with speckle noise even under the condition of small samples.
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Keywords:
- holography /
- phase unwrapping /
- deep learning /
- least square method
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表 1 3种网络对测试集的评价指标的平均值
Table 1 Average value of the evaluation indexes of the three networks on the test set
mean SSIM PSNR RMSE MAE V1+origin 0.8803 20.4403 0.6196 0.1582 V2+origin 0.9211 22.2151 0.5053 0.1054 V2+up 0.9241 22.3827 0.4951 0.1005 表 2 不同方法得到的解包裹结果的评价指标
Table 2 Evaluation indexes of unwrapping results obtained by different methods
SSIM PSNR RMSE MAE least square 0.5344 9.6771 13.5715 12.0839 PU-GAN 0.9309 23.7721 3.0579 2.1431 DLPU-Net 0.9504 23.6297 3.0464 2.5411 propose 0.9977 39.9847 0.4864 0.4302 -
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