In recent years, deep learning has been used widely to solve a variety of digital microscopy problems. We present ZEUS as a method to correct out of focus aberrations and denoise light-sheet microscopy images. First, a convolutional neural network is used to estimate the aberrations in terms of Zernike coefficients. Then those values are used to train a UNET that outputs corrected images from noisy and aberrated ones. With this approach, we can access scanning frequencies and image qualities equivalent to the most advanced LSM systems without the need for costly equipment and complex optical setups.
FORMA (force reconstruction via maximum-likelihood-estimator analysis) addresses the need to measure the force fields acting on microscopic particles. Compared to alternative established methods, FORMA is faster, simpler, more accurate, and more precise.
Furthermore, FORMA can also measure non-conservative and out-of-equilibrium force fields.
Here, after a brief introduction to FORMA, I will present its use, advantages, and limitations.
I will conclude with the most recent work where we exploit Bayesian inference to expand FORMA's scope of application.
FORMA (force reconstruction via maximum-likelihood-estimator analysis) addresses the need of measuring the force fields acting on microscopic particles. Compared to alternative established methods, FORMA is faster, simpler, more accurate, and more precise. Furthermore, FORMA can also measure non-conservative and out-of-equilibrium force fields. Here, after a brief introduction to FORMA, I will present its use, advantages and limitations. I will conclude with some recent work where we exploit Bayesian inference to expand the scope of application of FORMA.
A beam of light may possess both spin and orbital angular momentum. In non-paraxial conditions part of the spin converts into orbital angular momentum through the spin-orbit angular momentum conversion phenomenon. This effect has important consequences at the nanoscale, particularly in nano-manipulation and nano-photonics. In this work, we thoroughly analyze the rotation of microscopic beads subjected to a tightly focused Laguerre-Gaussian beam. Particularly, we observe the rotation of particles along circular trajectories that will depend strongly on the combination of topological charges and the state of polarization. Based on Richard and Wolf theory for non-paraxial beam focusing, we found a very good agreement between the experimental results and the theoretical model based on calculation of the optical forces using the generalized Lorenz-Mie theory.
The methods used to measure force fields have not changed in the last 30 years; their disadvantages have limited the possibility of measuring nanoscopic forces in many potential applications, such as experiments with non-conservative force fields and out-of-equilibrium conditions. We propose a new powerful, simpler, robust, and faster algorithm to measure force fields, Force Reconstruction via Maximum-likelihood-estimator Analysis(FORMA). FORMA has allowed us to retrieve the conservative and non-conservative components
of a force field acting on a Brownian particle from the analysis of its displacements, proving to have essential advantages over established techniques.
The accurate measurement of microscopic force fields is crucial in many branches of science and technology, from biophotonics and mechanobiology to microscopy and optomechanics. These forces are often probed by analysing their influence on the motion of Brownian particles. Here we introduce a powerful algorithm for microscopic force reconstruction via maximum-likelihood-estimator analysis (FORMA) to retrieve the force field acting on a Brownian particle from the analysis of its displacements [1]. FORMA estimates accurately the conservative and non-conservative components of the force field with important advantages over established techniques, being parameter-free, requiring ten-fold less data and executing orders-of-magnitude faster. We demonstrate FORMA performance using optical tweezers, showing how, outperforming other available techniques, it can identify and characterise stable and unstable equilibrium points in generic force fields. Thanks to its high performance, FORMA can accelerate the development of microscopic and nanoscopic force transducers for physics, biology and engineering.
[1] García, Laura Pérez, Jaime Donlucas Pérez, Giorgio Volpe, Alejandro V. Arzola, and Giovanni Volpe. "High-performance reconstruction of microscopic force fields from Brownian trajectories." Nature Communications 9, no. 1 (2018): 5166. https://doi.org/10.1038/s41467-018-07437-x
It is well known that speckle fields exhibit a multitude of vortex-type phase dislocations with unitary topological charge and opposite helicities, such that the average angular momentum is null. We tackle this problem the other way around: What is the minimum vortex number embedded in a carrier beam to produce a disordered pattern and what are the necessary conditions in terms of their initial distribution and topological charges? When studying this problem, we found interesting dynamical behavior of vortices in propagation through a focal region where they are forced to interact, depending on the initial conditions, that in some cases resemble the behavior of a system of particles with an effective repulsive interaction.
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