Abstract
We propose a two-dimensional (2-D) space-scale analysis of fringe patterns collected from a diffraction phase microscope based on the 2-D Morlet wavelet transform. We show that the adaptation of a ridge detection method with anisotropic 2-D Morlet mother wavelets is more efficient for analyzing cellular and high refractive index contrast objects than Fourier filtering methods since it can separate phase from intensity modulations. We compare the performance of this ridge detection method on theoretical and experimental images of polymer microbeads and experimental images collected from living myoblasts.
Highlights
During the past century, the attraction of biophysicists for observing and characterizing living matter at cellular and subcellular levels has been the prime mover for developing sophisticated microscopic devices
Even if the concept of diffraction-limited imaging and interferometry principles[1] was established for a long time, the actual development of microscopic devices based on interferometric contrast was achieved in the first part of the 20th century by Zernike[2] and Nomarski and Weill[3] and further developed by Gabor,[4] who pioneered the principle of holographic microscopy
A living cell is not a homogeneous medium, but is made of compartments surrounded by lipid membranes with high refractive index and highly dynamic proteic fiber network
Summary
The attraction of biophysicists for observing and characterizing living matter at cellular and subcellular levels has been the prime mover for developing sophisticated microscopic devices. To retrieve the phase image associated with the sample object, different methods have been proposed, including Hilbert transform followed by phase unwrapping,[28,29] derivative methods,[30] and Fourier filtering to avoid unwrapping problems.[31] All these phase retrieval algorithms rely on the assumption that the object phase does not alter the fringe carrier pattern, allowing a quasi one-dimensional analysis of interference patterns To improve this approach and delineate more precisely the validity of this assumption, we propose here to generalize Fourier filtering methods using a two-dimensional (2-D) space-scale analysis based on Morlet wavelet transform.[32] We first introduce the DPM principle and illustrate it on simple physical objects, such as micron-size particles. Martinez-Torres et al.: Diffraction phase microscopy: retrieving phase contours on living cells
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