Search results for "noise reduction"
showing 10 items of 71 documents
Four channels multi-illumination single-holographic-exposure lensless Fresnel (MISHELF) microscopy
2018
Abstract MISHELF microscopy [Opt. Express 23, 21352 (2015)] has been recently reported as the background technology of a new concept of compact, cost-effective and field-portable lensless microscope [Sci. Rep. 7, 43291 (2017)] based on wavelength multiplexing and a fast and robust algorithm for twin image minimization and noise reduction. In this manuscript, MISHELF microscopy is expanded beyond its actual configuration by considering 4 illumination/detection channels while retaining its working principle concerning single-shot, twin image mitigation and noise averaging. Proof of principle validation of the proposed improvement is conducted through experiments with a resolution test target …
Hilbert-Huang single-shot spatially multiplexed interferometric microscopy.
2018
Hilbert-Huang single-shot spatially multiplexed interferometric microscopy (H2S2MIM) is presented as the implementation of a robust, fast, and accurate single-shot phase estimation algorithm with an extremely simple, low-cost, and highly stable way to convert a bright field microscope into a holographic one using partially coherent illumination. Altogether, H2S2MIM adds high-speed (video frame rate) quantitative phase imaging capability to a commercially available nonholographic microscope with improved phase reconstruction (coherence noise reduction). The technique has been validated using a 20×/0.46 NA objective in a regular Olympus BX-60 upright microscope for static, as well as dynamic…
Frequency influence on the hot-electron noise reduction in GaAs operating under periodic signals
2008
A Monte Carlo study of the role of the frequency on the hot-electron intrinsic noise reduction in an n-type GaAs bulk driven by two mixed cyclostationary electric fields is presented. Previous numerical results showed the possibility to reduce the diffusion noise under specific wave-mixing conditions. In this work the variations of the noise properties are investigated by computing and integrating the spectral density of the velocity fluctuations. We found that the effect of reduction of the noise level due to the addition of a second field at twice frequency is almost independent of the frequency.
Total-variation-based methods for gravitational wave denoising
2014
We describe new methods for denoising and detection of gravitational waves embedded in additive Gaussian noise. The methods are based on Total Variation denoising algorithms. These algorithms, which do not need any a priori information about the signals, have been originally developed and fully tested in the context of image processing. To illustrate the capabilities of our methods we apply them to two different types of numerically-simulated gravitational wave signals, namely bursts produced from the core collapse of rotating stars and waveforms from binary black hole mergers. We explore the parameter space of the methods to find the set of values best suited for denoising gravitational wa…
Active reduction of fluctuations in fourth-order modulation instability
2012
International audience; We experimentally study the fluctuation properties of a scalar fourth-order modulation instability process obtained by pumping a photonic crystal fiber in the normal dispersion region. We observe large wavelength-dependant pulse-to-pulse fluctuations which cannot be significantly reduced by stimulating the process with a single seed. Their reduction requires two seeds slightly detuned from the maximum gain frequency in order to also stimulate the second-order modulation instability process cascaded from the fourth-order one. This concept is validated by experiments and numerical simulations.
Multi-illumination single-holographic-exposure lensless Fresnel (MISHELF) microscopy using 4 channels
2021
MISHELF microscopy is generalized by considering 4 illumination/detection channels while retaining single-shot working principle, twin image mitigation and noise averaging. Proof of principle validation is included considering a resolution test target.
Ultrasonic characterisation of poroux materials
2017
International audience; Acoustic models of the acoustics of porous and perforated media involve a set of physical parameters. Some of the parameters, the tortusity, the viscous and thermal characteristic lengths are defined for a perfect incompressible and inviscid fluid saturating the porous medium. It is shown that ultrasonic propagation in air-saturated materials can be used to determine these parameters. A basic method involving air-coupled ultrasonic transducers is presented. Variants of this method and a practical implementation of one of these is proposed.
Objective improvement of the visual quality of ion microscope images
2013
The need to operate with low ion beam fluences implies the images obtained using ion microscope (IM) are often grainy and have poor visual quality compared to what can be obtained using e.g. confocal microscopy. This results from the Poissonian distribution of counts in pixels. Here we report work on some different approaches for objectively improving the visual quality of IM images. In this work we present (i) dramatic improvement in the visual image quality of off-axis and direct-scanning transmission ion microscopy (STIM) images by suppression of zero-pixels; (ii) denoising of PIXE images using wavelet filtering and (iii) use of the feature preserving characteristics of wavelet filtering…
Multivariate denoising methods combining wavelets and principal component analysis for mass spectrometry data
2010
The identification of new diagnostic or prognostic biomarkers is one of the main aims of clinical cancer research. In recent years, there has been a growing interest in using mass spectrometry for the detection of such biomarkers. The MS signal resulting from MALDI-TOF measurements is contaminated by different sources of technical variations that can be removed by a prior pre-processing step. In particular, denoising makes it possible to remove the random noise contained in the signal. Wavelet methodology associated with thresholding is usually used for this purpose. In this study, we adapted two multivariate denoising methods that combine wavelets and PCA to MS data. The objective was to o…
A method for extracting subspace of deterministic sources from EEG data
2008
In this paper, an algorithm for separating linear subspaces of time-locked brain responses and other noise sources in multichannel electroencephalography data is proposed. The search criterion used by method discriminates time-locked brain components and noise components on the basis of the assumed deterministic behavior that the time-locked brain sources obey. The comprehensive derivation of the method is given together with the description and the analysis of the results of the method's application to simulated and real EEG data sets. The possibilities of improving the results are also discussed.