Fourier ptychographic microscopy (FPM) is a recently developed computational microscopy approach that can produce both wide field-of-view and high-resolution intensity and phase image of the sample. Traditionally, a periodic LED array is used as the illumination source. The frequency spectrum is a grid structure that is sparse in the low-middle frequency region and dense in the high-frequency region. However, for most biological samples, the useful information is mostly concentrated in the low-middle frequency region. So the traditional sampling method may lead to distortion in the reconstructed images because of insufficient sampling. Therefore, we propose a convenient and feasible method to continuously improve the sampling conditions without increasing the LED units and changing the pitch, termed double-height illumination FPM. The LED array is moved from one plane to another to achieve the sample illuminations at two different heights and the low-resolution intensity images are totally utilized to reconstruct the high-resolution complex amplitude image. Both simulation results and experimental results illustrate that the proposed method not only improves the reconstruction accuracy and efficiency, but also has strong robustness under noisy conditions. Furthermore, the rule of choosing the two illumination heights is discussed, and the physical insight of the proposed method is analyzed from the view of the data redundancy. In addition, a wave vector correction method is employed to reduce the artifacts of the reconstructed image at the edge of the large full field of view.

中文翻译：

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使用双高度照明增强傅立叶 ptychographic 显微镜的图像重建

傅里叶 ptychographic 显微镜 (FPM) 是最近开发的一种计算显微镜方法，它可以产生样品的宽视场和高分辨率强度和相位图像。传统上，使用周期性 LED 阵列作为照明源。频谱是中低频区域稀疏，高频区域密集的网格结构。然而，对于大多数生物样本而言，有用的信息大多集中在中低频区域。因此，传统的采样方法可能会因采样不足而导致重构图像失真。因此，我们提出了一种方便可行的方法，在不增加 LED 单元和改变间距的情况下不断改善采样条件，称为双高度照明 FPM。LED阵列从一个平面移动到另一个平面以实现两个不同高度的样品照明，并且完全利用低分辨率强度图像来重建高分辨率复振幅图像。仿真结果和实验结果都表明，所提出的方法不仅提高了重建精度和效率，而且在噪声条件下具有很强的鲁棒性。此外，讨论了选择两个照明高度的规则，并从数据冗余的角度分析了所提出方法的物理洞察力。此外，采用波矢量校正方法减少重建图像在大全视场边缘的伪影。