Halo-free Phase Contrast Microscopy

Abstract

We present a new approach for retrieving halo-free phase contrast microscopy (hfPC) images by upgrading the conventional PC microscope with an external interferometric module, which generates sufficient data for reversing the halo artifact. Acquiring four independent intensity images, our approach first measures haloed phase maps of the sample. We solve for the halo-free sample transmission function by using a physical model of the image formation under partial spatial coherence. Using this halo-free sample transmission, we can numerically generate artifact-free PC images. Furthermore, this transmission can be further used to obtain quantitative information about the sample, e.g., the thickness with known refractive indices, dry mass of live cells during their cycles. We tested our hfPC method on various control samples, e.g., beads, pillars and validated its potential for biological investigation by imaging live HeLa cells, red blood cells, and neurons.

Real-time halo correction in phase contrast imaging

“…To remove the gradient and highlight the edges otherwise submerged by the halo, we use a Hilbert transform to perform integration along the direction of the derivative. In the first approximation, the measured phase shift, φ m , can be described as the ideal phase, φ , from which a low-frequency version, , is subtracted[20], Equation 1 describes how portions of the measured image exhibit negative values. The key idea of our approach is to realize that since is a smooth function and, thus, its spatial derivative is negligible.…”

“…Fig. 4 shows a comparison between the proposed algorithm and a previous efforts [20], a runtime comparison is omitted as our method is implemented as an optimized GPU code, while the latter is written in MATLAB and runs on the CPU.…”

“…Finally, a method that combines both hardware and numerical processing was proposed in Ref. [20]. Using a full description of image formation with partially coherent light, this approach relies on iterative deconvolution steps to invert a nonlinear image formation model.…”

How neurons move during action potentials

“…6b. For a QPI imaging model, we incorporated the halo effect, an artifact due to the incomplete low-pass filtering of the reference beam 38,39 (See Supplementary Material). The measured and predicted deformation patterns, shown in Fig.…”

Local Optimization of Wave-fronts for optimal sensitivity PHase Imaging (LowPhi)

“…Wave-front shaping, the ability to digitally control the phase of incident light across large pixel arrays using MEMS or Liquid Crystal based technologies, has recently emerged as a powerful tool in microscopy and imaging. Various beam shaping techniques have been developed to enhance the capabilities of phase microscopes [13,14,15,16], mostly by tailoring phase masks in the diffraction plane. Recently, compressive phase imaging has been realized using a digital mirror device in an image plane [17].…”