White Light Phase-Shifting Interference Microscopy for Quantitative Phase Imaging of Red Blood Cells

Abstract

White light interference (WLI) microscopy is a non-contact and high-resolution quantitative imaging technique which has been utilized extensively for 3D-surface profilometry of industrial objects. Another important area for the utility of WLI is the quantitative imaging of biological samples, such as, human red blood cells (RBCs) [1] for the measurement of refractive index (RI) of RBCs at different wavelengths. The RI is a vital parameter to find out the state of biological cell, i.e., disease diagnosis non-invasively [1]. There has been various phase microscopic techniques such as, Fourier phase microscopy [2], Hilbert phase microscopy [3], digital holographic microscopy [4], diffraction phase microscopy[5] etc. In all these methods the RI profile is reconstructed for a single wavelength of illumination. But the RI is a function of wavelength. Multiple wavelength interferometry, such as, spectroscopic phase microscopy [6] and quantitative dispersion microscopy [7] etc are used to measure the RI of RBC at different wavelengths. But these techniques use white light with color filters or diffraction gratings and multi-color lasers to measure the RI at multiple wavelengths. We use WLI in conjunction with color fringe analysis to determine RI of RBC’s at multiple wavelengths using a single chip color CCD camera. Our technique does not require multiple color filters and multiple laser sources.