High-resolution transport-of-intensity quantitative phase microscopy with annular illumination

Abstract

For quantitative phase imaging (QPI) based on transport-of-intensity equation (TIE), partially coherent illumination provides speckle-free imaging, compatibility with brightfield microscopy, and transverse resolution beyond coherent diffraction limit. Unfortunately, in a conventional microscope with circular illumination aperture, partial coherence tends to diminish the phase contrast, exacerbating the inherent noise-to-resolution tradeoff in TIE imaging, resulting in strong low-frequency artifacts and compromised imaging resolution. Here, we demonstrate how these issues can be effectively addressed by replacing the conventional circular illumination aperture with an annular one. The matched annular illumination not only strongly boosts the phase contrast for low spatial frequencies, but significantly improves the practical imaging resolution to near the incoherent diffraction limit. By incorporating high-numerical aperture (NA) illumination as well as high-NA objective, it is shown, for the first time, that TIE phase imaging can achieve a transverse resolution up to 208 nm, corresponding to an effective NA of 2.66. Time-lapse imaging of in vitro Hela cells revealing cellular morphology and subcellular dynamics during cells mitosis and apoptosis is exemplified. Given its capability for high-resolution QPI as well as the compatibility with widely available brightfield microscopy hardware, the proposed approach is expected to be adopted by the wider biology and medicine community.

Resolution Analysis in a Lens-Free On-Chip Digital Holographic Microscope

“…In this subsection, we adopt the weak object approximation to simplify the mathematical formulation and linearize the phase retrieval problem [46,47]. The complex transmittance of a weak object can be represented as…”

“…Supposing that the central wavelength λ, the spectrum width ∆λ, the spectral distribution S λ (λ i ) are the predetermined parameters, and other system parameters are close to ideal values (do not affect the imaging resolution). If we further invoke the paraxial approximations [47], the two transfer functions Eqs. (5) and (6) can be simplified as AT F p ≈ 2a 0 cos πz 2 λ|u| 2 , PT F p ≈ −2a 2 0 sin πz 2 λ|u| 2 .…”

High-speed in vitro intensity diffraction tomography

“…Quantitative phase imaging (QPI) [1,4] is one such technique that measures an incident field's phase shifts induced by the sample to recover the sample's physical properties without staining or labeling. Both interferometry [5][6][7][8] and non-interferometry based [9][10][11][12][13] QPI techniques have been developed to recover a sample's phase map in two-dimensions (2D). A single 2D integrated phase image, however, is insufficient for characterizing 3D heterogeneous samples.…”

Three-dimensional tomographic microscopy technique with multi-frequency combination with partially coherent illuminations

“…The conventional off-axis digital holographic microscopy (DHM) [3][4][5] has been developed to measure the total phase delay quantitatively, and some other interferometric methods based on common path geometries have been also proposed to improve the imaging quality and spatial resolution of the phase measurement by using spatial light modulator (SLM) or white-light sources. 6,7 In addition, there are also numerous variants of non-interferometric phase retrieval approaches, like transport of intensity equation (TIE) [8][9][10][11][12][13] and differential phase contrast (DPC), 14 which provide promising QPI results under coherent illumination and partially coherent illumination.…”