A digital hologram-optimizing method was proposed to improve the imaging quality of dual-wavelength digital holographic microscopy (DDHM) by reducing the phase noise level. In our previous work, phase noise reduction was achieved by dual-wavelength digital image-plane holographic microscopy (DDIPHM). In the optimization method in this paper, the phase noise was further reduced by enhancing the real-image term and suppressing effects of the zero-order term in the frequency spectrum of a digital hologram. Practically, the carrier frequency of the real-image term has the correspondence with interference fringes in the hologram. Mathematically, the first order intrinsic mode function (IMF1) in bidimensional empirical mode decomposition (BEMD) has similar characteristics to the grayscale values of ideal interference fringes. Therefore, with the combination of DDIPHM and BEMD, by utilizing the characteristics of IMF1, the digital hologram was optimized with purified interference fringes, enhancing the real-image term simultaneously. Finally, the validity of the proposed method was verified by experimental results on a microstep.

中文翻译：

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一种提高双波长数字全息显微成像质量的方法

提出了一种数字全息图优化方法，通过降低相位噪声水平来提高双波长数字全息显微镜（DDHM）的成像质量。在我们之前的工作中，相位噪声降低是通过双波长数字图像平面全息显微镜 (DDIPHM) 实现的。在本文的优化方法中，通过增强实像项和抑制数字全息图频谱中零阶项的影响，进一步降低了相位噪声。实际上，实像项的载波频率与全息图中的干涉条纹具有对应关系。在数学上，二维经验模式分解 (BEMD) 中的一阶本征模式函数 (IMF1) 与理想干涉条纹的灰度值具有相似的特性。所以，结合DDIPHM和BEMD，利用IMF1的特点，对数字全息图进行了优化，干涉条纹纯净，同时增强了实像项。最后，通过微步的实验结果验证了所提出方法的有效性。