Examination of the structural poperties of the H3O+(H2O)n clusters in the (?PT) Grand Canonical ensemble, by employing a new many-body potential-energy function

Journal URL: http://jcp.aip.org/jcp/staff.js

Lensless hyperspectral imaging by Fourier transform spectroscopy for broadband visible light: phase retrieval technique

A novel phase retrieval algorithm for broadband hyperspectral phase imaging from noisy intensity observations is proposed. It utilizes advantages of the Fourier Transform spectroscopy in the self-referencing optical setup and provides, additionally beyond spectral intensity distribution, reconstruction of the investigated object's phase. The noise amplification Fellgett's disadvantage is relaxed by the application of sparse wavefront noise filtering embedded in the proposed algorithm. The algorithm reliability is proved by simulation tests and results of physical experiments on transparent objects which demonstrate precise phase imaging and object depth (profile) reconstructions.Comment: 12 pages, 8 figure

Deep convolutional neural network-based lensless quantitative phase retrieval

In this paper, we employ a deep convolutional neural network for the solution of the phase retrieval problem in a lensless optical system from a single observation. We utilize U-net-like structured DCNN to reconstruct phase from the amplitude images at the sensor plane, and after applying computational backpropagation, the complex objects’ amplitude is reconstructed at the object plane. Results are demonstrated by simulation experiments.publishedVersionPeer reviewe

Phase Retardation Analysis in a Rotated Plane-Parallel Plate for Phase-Shifting Digital Holography

In this paper, we detail a phase-shift implementation in a rotated plane-parallel plate (PPP). Considering the phase-shifting digital holography application, we provide a more precise phase-shift estimation based on PPP thickness, rotation, and mutual inclination of reference and object wavefronts. We show that phase retardation uncertainty implemented by the rotated PPP in a simple configuration is less than the uncertainty of a traditionally used piezoelectric translator. Physical experiments on a phase test target verify the high quality of phase reconstruction.publishedVersionPeer reviewe

Hyperspectral phase imaging based on denoising in complex-valued eigensubspace

A new denoising algorithm for hyperspectral complex domain data has been developed and studied. This algorithm is based on the complex domain block-matching 3D filter including the 3D Wiener filtering stage. The developed algorithm is applied and tuned to work in the singular value decomposition (SVD) eigenspace of reduced dimension. The accuracy and quantitative advantage of the new algorithm are demonstrated in simulation tests and in the processing of the experimental data. It is shown that the algorithm is effective and provides reliable results even for highly noisy data

Power-Balanced Hybrid Optics Boosted Design for Achromatic Extended-Depth-of-Field Imaging via Optimized Mixed OTF

The power-balanced hybrid optical imaging system is a special design of a diffractive computational camera, introduced in this paper, with image formation by a refractive lens and Multilevel Phase Mask (MPM). This system provides a long focal depth with low chromatic aberrations thanks to MPM and a high energy light concentration due to the refractive lens. We introduce the concept of optical power balance between the lens and MPM which controls the contribution of each element to modulate the incoming light. Additional unique features of our MPM design are the inclusion of quantization of the MPM's shape on the number of levels and the Fresnel order (thickness) using a smoothing function. To optimize optical power-balance as well as the MPM, we build a fully-differentiable image formation model for joint optimization of optical and imaging parameters for the proposed camera using Neural Network techniques. Additionally, we optimize a single Wiener-like optical transfer function (OTF) invariant to depth to reconstruct a sharp image. We numerically and experimentally compare the designed system with its counterparts, lensless and just-lens optical systems, for the visible wavelength interval (400-700)nm and the depth-of-field range (0.5-$\infty$m for numerical and 0.5-2m for experimental). The attained results demonstrate that the proposed system equipped with the optimal OTF overcomes its counterparts (even when they are used with optimized OTF) in terms of reconstruction quality for off-focus distances. The simulation results also reveal that optimizing the optical power-balance, Fresnel order, and the number of levels parameters are essential for system performance attaining an improvement of up to 5dB of PSNR using the optimized OTF compared with its counterpart lensless setup.Comment: 18 pages, 14 figure

Lensless hyperspectral phase retrieval via alternating direction method of multipliers and spectral proximity operators

We propose a hyperspectral broadband phase retrieval technique with spectrally varying object and modulation phase masks. The technique is based on a complex domain version of the alternating direction method of multipliers (ADMM) and the Spectral Proximity Operators derived for Gaussian and Poisson intensity observations, which are considered as a sum of separate spectral diffractive patterns. The proximity operators filter noisy observations compromising between noisy intensity observations and their predicted counterparts and retrieve the complex-domain spectral components of the object from these filtered observations. The simulation and physical tests confirm that the broadband hyperspectral phase retrieval in the proposed formulation is resolved.Peer reviewe

Chemical potential of quadrupolar two-centre Lennard-Jones fluids by gradual insertion

The gradual insertion method for direct calculation of the chemical potential by molecular simulation is applied in the NpT ensemble to different quadrupolar two-centre Lennard-Jones fluids at high density state points. The results agree well with Widom's test particle insertion but show at very high densities significantly smaller statistical uncertainties. The gradual insertion method, which is coupled here with preferential sampling, extends the density range where reliable information on the chemical potential can be obtained. Application details are reported

Millimeter Wave Scattering from Neutral and Charged Water Droplets

We investigated 94GHz millimeter wave (MMW) scattering from neutral and charged water mist produced in the laboratory with an ultrasonic atomizer. Diffusion charging of the mist was accomplished with a negative ion generator (NIG). We observed increased forward and backscattering of MMW from charged mist, as compared to MMW scattering from an uncharged mist. In order to interpret the experimental results, we developed a model based on classical electrodynamics theory of scattering from a dielectric sphere with diffusion-deposited mobile surface charge. In this approach, scattering and extinction cross-sections are calculated for a charged Rayleigh particle with effective dielectric constant consisting of the volume dielectric function of the neutral sphere and surface dielectric function due to the oscillation of the surface charge in the presence of applied electric field. For small droplets with (radius smaller than 100nm), this model predicts increased MMW scattering from charged mist, which is qualitatively consistent with the experimental observations. The objective of this work is to develop indirect remote sensing of radioactive gases via their charging action on atmospheric humid air.Comment: 18 pages, 8 figure