White-light diffraction phase microscopy at doubled space-bandwidth product.

Mingguang Shan,Mikhail E Kandel,Viorel Nastasa,Hassaan Majeed,Gabriel Popescu

doi:10.1364/oe.24.029033

Abstract

White light diffraction microscopy (wDPM) is a quantitative phase imaging method that benefits from both temporal and spatial phase sensitivity, granted, respectively, by the common-path geometry and white light illumination. However, like all off-axis quantitative phase imaging methods, wDPM is characterized by a reduced space-bandwidth product compared to phase shifting approaches. This happens essentially because the ultimate resolution of the image is governed by the period of the interferogram and not just the diffraction limit. As a result, off-axis techniques generates single-shot, i.e., high time-bandwidth, phase measurements, at the expense of either spatial resolution or field of view. Here, we show that combining phase-shifting and off-axis, the original space-bandwidth is preserved. Specifically, we developed phase-shifting diffraction phase microscopy with white light, in which we measure and combine two phase shifted interferograms. Due to the white light illumination, the phase images are characterized by low spatial noise, i.e., <1nm pathlength. We illustrate the operation of the instrument with test samples, blood cells, and unlabeled prostate tissue biopsy.

Highlights

Quantitative phase imaging (QPI) has been receiving intense scientific interest as a new modality for label-free biomedical optical imaging [1]
Since the optical phase delay introduced by the specimen depends on both its thickness and refractive index, which essentially represents density, QPI has been used in a variety of applications, including topography and volume try of red blood cells [11, 12], cell membrane fluctuations [13, 14], cell growth [15, 16], intracellular mass transport [17,18,19], cancer diagnosis in biopsies [20,21,22]
Note that for all values of F, the spatial phase noise is lower for the phase shifting method (Figs. 3(a)-3(h)). These results indicate that for F ≥ 0.5, the wDPM suffers from aliasing, which becomes severe for F = 1.0

Summary

Introduction

Quantitative phase imaging (QPI) has been receiving intense scientific interest as a new modality for label-free biomedical optical imaging [1]. Quantitative Phase Imaging of Cells and Tissues (McGraw-Hill, 2011). “Parallel on-axis holographic phase microscopy of biological cells and unicellular microorganism dynamics,” Appl. Wattellier, “Enhanced 3D spatial resolution in quantitative phase microscopy using spatially incoherent illumination,” Opt. Express 22(7), 8654–8671 (2014).

Results

Conclusion