基于时空域退偏的数字全息成像去噪研究

为了抑制全息记录过程中的散斑噪声，采用一种通过降低相干光源相干性的方法，并进行了理论分析和实验验证。利用旋转二元波片进行退偏，在10s内记录70幅全息图进行平均化降噪; 同时利用毛玻璃对相干光进行空间退相干，降低了光源的相干性从而降低了散斑噪声。将单独采用时间退偏操作的重建图像与单独采用空间退偏操作的重建图像以及两者相结合的重建图像进行了对比。通过实验验证了所提方法的可行性，通过分析频谱比较证实了几种方法，利用信噪比直观地证实了几种方法的有效性。结果表明，时间、空间退偏结合对散斑噪声的抑制有着明显的优势，空间退偏的重建像的信噪比为0.4459，时间退偏的重建像信噪比为1.5155，而两者结合后的信噪比为1.7162，采用时间退偏以及空间退偏叠加的方式有效地抑制了相干噪声。该实验为研究数字全息成像的过程中由于光源相干度过高带来的散斑噪声干扰的问题提供了一个有效的抑制方法。

Research on digital holographic imaging denoising based on time-space domain depolarization

In order to suppress speckle noise during holographic recording, a coherence method by reducing the coherent light source was used, and the theoretical analysis and experimental verification were performed. A rotating binary wave plate was used for depolarization, and 70 holograms were recorded in 10s for average noise reduction. At the same time, ground glass was used for spatial decoherence of the coherent light, which reduces the coherence of the light source and thus the speckle noise. The reconstructed image with the temporal depolarization operation alone was compared with the reconstructed image with the spatial depolarization operation alone, and the reconstructed image combining the two. The feasibility of the proposed method was verified by experiments, and several methods were confirmed by analyzing the frequency spectrum comparison. The signal-to-noise ratio was used to directly confirm the effectiveness of several methods. The experimental results show that the combination of time and space depolarization has obvious advantages in suppressing speckle noise. The signal-to-noise ratio of the reconstructed image with spatial depolarization is 0.4459, the reconstructed image with time depolarization is 1.5155, and the combined image with time depolarization is 1.7162. The method of time decrement and space decrement stack is used to suppress the coherent noise effectively. This experiment provides an effective method for the study of speckle noise caused by the over-high coherence of light source in the process of digital holographic imaging.