Quantitative phase imaging and complex field reconstruction by pupil modulation differential phase contrast.

Hangwen Lu,Xiaoze Ou,Jaebum Chung,Changhuei Yang

doi:10.1364/oe.24.025345

Abstract

Differential phase contrast (DPC) is a non-interferometric quantitative phase imaging method achieved by using an asymmetric imaging procedure. We report a pupil modulation differential phase contrast (PMDPC) imaging method by filtering a sample's Fourier domain with half-circle pupils. A phase gradient image is captured with each half-circle pupil, and a quantitative high resolution phase image is obtained after a deconvolution process with a minimum of two phase gradient images. Here, we introduce PMDPC quantitative phase image reconstruction algorithm and realize it experimentally in a 4f system with an SLM placed at the pupil plane. In our current experimental setup with the numerical aperture of 0.36, we obtain a quantitative phase image with a resolution of 1.73μm after computationally removing system aberrations and refocusing. We also extend the depth of field digitally by 20 times to ±50μm with a resolution of 1.76μm.

Highlights

While traditional microscopy only captures the intensity, an object’s phase information is highly desired in many situations
Quantitative phase imaging with microbeads A quantitative phase images of a 10μm polystyrene microbead sample is imaged to show pupil modulation differential phase contrast (PMDPC)’s quantitative phase reconstruction capability. 10μm microbeads are immersed in oil (n = 1.580) at room temperature
Quantitative high resolution phase images can be reconstructed with a minimum of one pair of phase gradient images captured with complimentary half-circle pupils

Summary

Introduction

While traditional microscopy only captures the intensity, an object’s phase information is highly desired in many situations. Used phase gradient methods such as Zernike phase contrast microscope [1] and Nomarski’s differential interference contrast (DIC) [2] are able to get qualitative phase contrast images. In both techniques, phase and intensity information are mixed in the images and the phase measurement is not quantitative. Holography [3,4,5,6,7] is another phase imaging method where the object’s wavefront interferes with a reference beam and the phase information is obtained from the recorded interference pattern. Limited spatial coherence negatively influences the absolute phase value accuracy

Methods

Results

Conclusion