Gaussian coherent transfer function of partially coherent Fourier ptychographic microscopy

Fourier ptychographic microscopy (FPM) is a novel technique for coherent imaging with the advantages of high-resolution, wide field-of-view, quantitative phase contrast, and label-free imaging. However, the light source of most FPM systems is light-emitting diode (LED) arrays, which are not an ideal coherent point source and lead to deviations between theory and experiment. In this paper, the temporal and spatial coherence of the LED light source used in the FPM is reanalyzed by the Gaussian-Schell model, and a new spatial spectrum constraint is proposed, which is called Gaussian coherent transfer function (CTF). Through theoretical calculation, numerical simulation, and experimental reconstruction, the imaging recovery quality of FPM is improved by introducing the Gaussian CTF constraint. The proposed Gaussian CTF is applicable to other coherent imaging techniques based on LED light sources.