Opt Lett. 2021 Apr 1;46(7):1740-1743. doi: 10.1364/OL.422095.
As a well-established deterministic phase retrieval approach, the transport of intensity equation (TIE) is able to recover the quantitative phase of a sample under coherent or partially coherent illumination with its through-focus intensity measurements. Nevertheless, the inherent paraxial approximation limits its validity to low-numerical-aperture imaging and slowly varying objects, precluding its application to high-resolution quantitative phase imaging (QPI). Alternatively, QPI can be achieved by phase deconvolution approaches based on the coherent contrast transfer function or partially coherent weak object transfer function (WOTF) without invoking paraxial approximation. But these methods are generally appropriate for "weakly scattering" samples in which the total phase delay induced by the object should be small. Consequently, high-resolution high-accuracy QPI of "nonweak" phase objects with fine details and large phase excursions remains a great challenge. In this Letter, we propose a mixed-transfer-function (MTF) approach to address the dilemma between measurement accuracy and imaging resolution. By effectively merging the phases reconstructed by TIE and WOTF in the frequency domain, the high-accuracy low-frequency phase "global" profile can be secured, and high-resolution high-frequency features can be well preserved simultaneously. Simulations and experimental results on a microlens array and unstained biological cells demonstrate the effectiveness of MTF.
作为一种成熟的确定性相位恢复方法，强度传输方程（TIE）能够通过其聚焦强度测量来恢复相干或部分相干照明下样品的定量相位。然而，其固有的傍轴近似限制了其在低数值孔径成像和缓慢变化物体中的有效性，排除了其在高分辨率定量相位成像（QPI）中的应用。或者，可以通过基于相干对比度传递函数或部分相干弱物体传递函数（WOTF）的相位反卷积方法来实现 QPI，而无需调用傍轴近似。但是，这些方法通常适用于“弱散射”样品，其中物体引起的总相位延迟应该较小。因此，对于具有精细细节和大相位偏移的“非弱”相位物体的高分辨率高精度 QPI 仍然是一个巨大的挑战。在这封信中，我们提出了一种混合传递函数（MTF）方法来解决测量精度和成像分辨率之间的困境。通过在频域中有效地合并 TIE 和 WOTF 重建的相位，可以确保高精度低频相位“全局”轮廓，同时很好地保留高分辨率高频特征。微透镜阵列和未经染色的生物细胞的模拟和实验结果证明了 MTF 的有效性。
