Quantitative phase imaging using a combination of flat fielding and windowed Fourier filtering demodulated by a graph cuts algorithm for screening opaque and transparent objects

Abstract

In this paper, quantitative phases of opaque and transparent objects are measured precisely using a combination of flat fielding and windowed Fourier filtering demodulated by graph cuts algorithm. The modulated interferogram is corrected first by flat fielding to remove dust particles and adjust inhomogeneity of the interferogram intensity. The corrected interferogram is then convolved by windowed Fourier filtering to produce an interferogram free from speckle noise. The obtained interferogram is reconstructed by the Fourier transform method, or the wavelet method, or the angular spectrum method to extract the wrapping phase of the object. A graph cuts algorithm is used to unwrap the wrapping phase to remove the 2π ambiguity. Experimental results show that quantitative phases of the objects being screened are precisely measured by the proposed method. Moreover, the lateral resolution, which is represented by slope of the roll-off is slightly improved without applications of digital filters. Furthermore, shapes of the echinocytes of the cancerous blood cells which have the sharpest spatial features are seen clearly by the proposed method.