Spectrum aliasing minimization for Fourier ptychographic microscopy based on annular illumination optimization

Abstract

We present a spectrum aliasing minimization scheme for Fourier ptychographic microscopy (FPM) based on annular illumination pattern optimization. Normally, the Nyquist sampling criterion under the coherent illumination case is required due to the quasi-coherent illumination system used in the conventional FPM technique. However, the spatial sampling criterion changes with the oblique illumination angles. When the illumination NA matches the objective NA, the spatial sampling criterion should be reconsidered under the incoherent case, since the phase information is lost during intensity imaging. In this paper, an optimal annular illumination based Fourier ptychographic microscopy (OAIFPM) method is proposed. After investigating the spectrum aliasing characteristic of different spatial sampling rates and establishing an objective cost function related to the spectrum aliasing percentage and reconstruction error, the reconstruction accuracy can be improved while the incoherent spatial sampling criterion is not satisfied. The results suggest that our OAIFPM system could be a powerful imaging technique for various high-throughput microscopic applications, such as drug discovery, cellular phenotypes characterization, and identification of disease mechanisms.