The advantages of quantitative phase microscopy (QPM) such as label-free imaging with high spatial sensitivity, live cell compatibility and high-speed imaging makes it viable for various biological applications. The measurement accuracy of QPM strongly relies on the shape of the recorded interferograms, whether straight or curved fringes are recorded during the data acquisition. Moreover, for a single shot phase recovery high fringe density is required. The wavefront curvature for the high-density fringes over the entire field of view is difficult to be discerned with the naked eye. As a consequence, there is a quadratic phase aberration in the recovered phase images due to curvature mismatch. In the present work, we have implemented sampling moiré method for real-time sensing of the wavefront curvature mismatch between the object and the reference wavefronts and further for its correction. By zooming out the interferogram, moiré fringes are generated which helps to easily identify the curvature of the fringes. The wavefront curvature mismatch correction accuracy of the method is tested with the help of low temporal coherent light source such as a white light (temporal coherence ∼ 1.6 µm). The proposed scheme is successfully demonstrated to remove the quadratic phase aberration caused due to wavefront mismatch from an USAF resolution target and the biological tissue samples. The phase recovery accuracy of the current scheme is further compared with and found to better than the standard method called principle component analysis. The proposed method enables recording of the corrected wavefront interferogram without needing any additional optical components or modification and also does not need any post-processing correction algorithms. The proposed method of curvature compensation paves the path for a high-throughput and accurate quantitative phase imaging.

中文翻译：

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采样莫尔条纹法：一种用于检测二次相位畸变的工具及其校正工具，用于精确的定量相位显微镜

定量相显微镜（QPM）的优势，例如具有高空间灵敏度的无标记成像，活细胞相容性和高速成像，使其在各种生物学应用中都具有可行性。QPM的测量精度在很大程度上取决于记录的干涉图的形状，无论是在数据采集期间记录直线还是弯曲条纹。此外，对于单次喷射相恢复，需要高条纹密度。肉眼很难分辨出整个视场中高密度条纹的波前曲率。结果，由于曲率失配，在恢复的相位图像中存在二次相位像差。在目前的工作中，我们已经实现了采样莫尔条纹方法，用于实时检测物体与参考波阵面之间的波阵面曲率不匹配，并对其进行校正。通过缩小干涉图，可生成莫尔条纹，这有助于轻松识别条纹的曲率。该方法的波前曲率失配校正精度是在诸如白光之类的低时间相干光源（时间相干度约为1.6 µm）的帮助下进行测试的。该方案被成功证明可以消除USAF分辨率目标和生物组织样本中由于波前失配而引起的二次相位像差。进一步比较了当前方案的相恢复精度，发现其优于称为主成分分析的标准方法。所提出的方法能够记录校正后的波前干涉图，而无需任何附加的光学组件或修改，并且也不需要任何后处理校正算法。提出的曲率补偿方法为高通量和精确的定量相位成像铺平了道路。