Measurement Of Phase Distribution Research Articles

Laser Vibrometry of Shear Waves in a Layer of a Gel-Like Medium

Abstract—A laser scanning vibrometer was used to measure the amplitudes and phases of the vibrational velocity of shear waves excited by a one-dimensional source in the form of a narrow rectangular bar in a gellike medium. The vibrations of 26 plates reflecting the laser beam and located inside an optically transparentphantom along a segment with a length of 84.5 mm at a distance of 20 mm from the source were measured.The angular distributions of the amplitude and phase of shear waves at discrete frequencies from 59 to 500 Hz were measured in continuous mode. In pulsed mode, the vibrator excited a pulse in the medium with a durationof 1.5 periods of the 300 Hz frequency. The amplitudes and phases of shear waves were calculated by fastFourier transform of the time profile of the vibration velocity of the plates with a duration of 50 ms. The angular amplitude distributions measured in the pulsed and continuous modes are qualitatively the same. At all frequencies, the distributions are symmetrical with respect to the vertical axis. The maximum oscillation amplitude is observed at angles close to ±45°. The velocity of shear waves, calculated from the measured phase distributions, increases from 2 to 2.5 m/s with a change in frequency from 50 to 500 Hz. It is shown that this velocity behavior is well described by a relaxation model of the medium with one relaxation time equal to 0.3 ms. Shear wave attenuation depends on frequency and exceeds 1 cm-1 for waves with frequencies above250 Hz. The maximum attenuation per wavelength is observed near the relaxation frequency of the medium in the 300–400 Hz range. The results can be used to optimize devices for measuring the elasticity of soft tissues.

Measurement of the longitudinal bunch-shape distribution for a high-intensity negative hydrogen ion beam in the low-energy region

A bunch-shape monitor (BSM) is a useful device for performing longitudinal beam tuning using the pointwise longitudinal phase distribution measured at selected points in the beam transportation. To measure the longitudinal phase distribution of a low-energy negative hydrogen (${\mathrm{H}}^{\ensuremath{-}}$) ion beam, highly oriented pyrolytic graphite (HOPG) was adopted for the secondary-electron-emission target to mitigate the thermal damage due to the high-intensity beam loading. The HOPG target enabled the measurement of the longitudinal phase distribution at the center of a 3-MeV ${\mathrm{H}}^{\ensuremath{-}}$ ion beam with a high peak current of about 50 mA. The longitudinal bunch width was measured using HOPG-BSM at the test stand, which was consistent with the beam simulation. The correlation measurement between the beam transverse and longitudinal planes was demonstrated using HOPG-BSM. The longitudinal Twiss and emittance measurement with the longitudinal Q-scan method was conducted using HOPG-BSM. The measured longitudinal emittance is consistent with the beam simulation using the radio-frequency quadrupole design input.

Simultaneous high-accuracy measurements of local heat transfer and phase distribution during convective condensation using non intrusive diagnostic tools

An experimental setup was built to measure simultaneously the profiles of the phase distribution and the heat transfer coefficient in a minitube during convective condensation of HFE7000 at low mass velocities. The aim is to overcome the lack of measurements available in the literature in these conditions, mainly due to the difficulty to measure accurately heat transfer and phase distribution simultaneously. The metrology combines two high-precision measurement techniques allowing accurate measurement of the condenser wall temperature by infrared method and the thickness of the liquid film flowing inside the condenser by interferometric or confocal method. A specific protocol was developed to reduce the uncertainty on the wall temperature down to 0.08 °C. The flow regime varies from smooth annular to wavy annular with mean thickness of the liquid film less than 100 μm when the mass velocity is increased from 5 to 30 kg m−2 s−1. The heat transfer coefficient increases locally by up to 30% as the mass velocity increases. These profiles were than compared to the ones of both Nusselt theory and 5 correlations selected from the literature. None of them allow an accurate prediction of the heat transfer coefficient obtained experimentally.

Measurements of phase distributions of optical vortices based on the sinusoidal phase modulation method

Vortex beams (VBs), a type of light beam with a spiral wavefront, have unique properties, such as the orbit angular momentum (OAM), and diverse applications in optical communications and optical trapping and tweezers. Therefore, accurate measurements and estimations of the phase distribution and topological charge are essential for their applications to ensure VB quality. In this paper, we employed a sinusoidal phase modulation (SPM) interferometry to measure the phase distributions of VBs and the topological charge of VBs were estimated by mean of a method of the process of unwrapped phase. The phase measurement of optical vortices generated by a spatial light modulator (SLM) demonstrated that the SPM interferometry-based technique had a high measurement accuracy with a simplified configuration. The estimation errors of the topological charges for various orders of VBs were within approximately 4%. The fluctuation in the surface of the SLM leading to the flatness of the wavefront was estimated to be 0.06 rad by 10 consecutive measurements

Spectral phase-front diagnostics for ultrashort laser pulses via quasi-self-referenced interferometry

We present a novel, to the best of our knowledge, design for the spectrally resolved wavefront diagnostics of ultrashort laser pulses. The design uses quasi-self-referenced interferometry (qSRI), is completely achromatic, and avoids dispersion. The qSRI utilizes a perfect reference beam enabling an absolute measurement of the near-field spatial phase distributions for the different spectral components of ultrashort laser pulses. For this, a Mach–Zehnder geometry is coupled with a spatial filter. Combining the qSRI with a reflective grating allows for the measurement of phase fronts in the whole spectrum of a broadband laser pulse without any calibration.

Simultaneous High-Accuracy Measurements of Local Heat Transfer and Phase Distribution During Convective Condensation Using Non Intrusive Diagnostic Tools

Simultaneous High-Accuracy Measurements of Local Heat Transfer and Phase Distribution During Convective Condensation Using Non Intrusive Diagnostic Tools

Geochemical characterization of dust from arsenic-bearing tailings, Giant Mine, Canada

Dust from uncovered mine tailings at Giant mine, an abandoned mine in northern Canada, has been a concern for nearby residents. We have utilized microanalytical mineralogical analysis combined with quantitative measurements of phase distribution and bulk concentration to fully characterize the dust currently generated from the Giant mine tailings. Surface tailings material was sampled from three tailings impoundments on site and sieved to <63 μm as a proxy for dust, and total suspended particulate (TSP) samples were collected continuously over two months to represent the airborne material that is generated from the tailings. Inductively coupled plasma-optical emission spectrometry (ICP-OES) and -mass spectrometry (ICP-MS) show elevated concentrations of As, Sb, Zn, Pb, Cu and Ni in all samples; comparison of results for sieved and unsieved samples show that As is more concentrated in the <63 μm fraction of the tailings. The X-ray absorption near edge structure (XANES) results for the tailings indicate that the As in the samples is a mixture of As1−, As5+ and As3+. Scanning electron microscope-based mineral liberation analysis (SEM-MLA) results show that roaster-generated iron-oxides (i.e., maghemite), calcium-iron arsenate (i.e., yukonite), and arsenopyrite comprise the majority of the As-bearing particles in the surface tailings; of these three solid phases, calcium-iron arsenate poses the greatest risk to human health as it exhibits the highest relative bioaccessibility. A rare lead arsenate phase, which may be bioaccessible, was also detected in minor quantities in the surface tailings; this phase was identified as mimetite through μXRD analysis. Very little arsenic trioxide was found in the surface tailings samples, and no arsenic trioxide was found in the TSP samples; this is because the tailings that were exposed to arsenic trioxide-bearing roaster stack emissions during the 1950s and 1960s have been buried by more recent tailings. Soils near the Giant mine tailings have been found to contain arsenic trioxide from historic stack emissions, which indicates that the mine-impacted environmental media surrounding a tailings impoundment could in some cases pose a greater risk to environmental and human health than the tailings themselves.

Measurement of real phase distribution of a vortex beam propagating in free space based on an improved heterodyne interferometer

This paper proposes an improved heterodyne interferometer to measure the real phase distribution of vortex beams propagating in free space. The fundamental mode Gaussian beam passes through the vortex phase plate and has one or more phase transitions of 2π along the angular direction. Such vortex beams undergo phase distortion during transmission, and their complex phase distribution is difficult to measure. The improved heterodyne interferometer proposed in this study successfully measures the phase distortion, demonstrating high spatial resolution and phase measurement accuracy. Both the theoretical and the experimental results show that in the process of free space propagation, the phase jump intersection boundary transforms from a straight line into a twisted line and that the phase distribution gradually becomes a spiral phase distribution followed by a ring intensity distribution corresponding to further increase in the propagation distance. The proposed method is estimated to be capable of predicting the variation of the vortex beams based on the research conducted on the interaction between the vortex beams and the atmospheric turbulence.

Phase characterisation of metalenses

Metalenses have emerged as a new optical element or system in recent years, showing superior performance and abundant applications. However, the phase distribution of a metalens has not been measured directly up to now, hindering further quantitative evaluation of its performance. We have developed an interferometric imaging phase measurement system to measure the phase distribution of a metalens by taking only one photo of the interference pattern. Based on the measured phase distribution, we analyse the negative chromatic aberration effect of monochromatic metalenses and propose a feature size of metalenses. Different sensitivities of the phase response to wavelength between the Pancharatnam-Berry phase-based metalens and propagation phase-reliant metalens are directly observed in the experiment. Furthermore, through phase distribution analysis, it is found that the distance between the measured metalens and the brightest spot of focusing will deviate from the focal length when the metalens has a low nominal numerical aperture, even though the metalens is ideal without any fabrication error. We also use the measured phase distribution to quantitatively characterise the imaging performance of the metalens. Our phase measurement system will help not only designers optimise the designs of metalenses but also fabricants distinguish defects to improve the fabrication process, which will pave the way for metalenses in industrial applications.

Accurate phase analysis of interferometric fringes by the spatiotemporal phase-shifting method

Phase-shifting interferometry (PSI) has been widely applied in the field of accurate optical methodology. However, the fluctuation of background and amplitude intensities due to the instability of laser source, and phase-shifting error or vibration are significant problems for the PSI. In this study, the spatiotemporal phase-shifting method (ST-PSM) (Ri S et al 2019 J. Opt. 21 095702), which is a highly accurate and robust phase analysis method using spatial and temporal intensities information simultaneously, is first applied to laser interferometry to achieve a stable measurement. Through several simulations, three effects of fluctuations in background and amplitude intensities, phase-shifting error were investigated. As a result, we clarified that the periodic phase error with fundamental or second harmonic frequencies occurs in the conventional PSM method, whereas no periodic error occurs in the ST-PSM. Besides, the ST-PSM is also robust to the noise either for uniform or distorted interference fringe images. In the Michelson laser interferometer experiment, the ST-PSM realizes a much more stable measurement of phase and phase gradient distributions than the PSM. We have revealed the excellent performance and the striking advantage that ST-PSM is entirely free of periodic errors in a similar manner to the simulations. Therefore, laser interferometry using the ST-PSM can be expected to apply to various applications, including the extremely accurate non-contact shape and deformation measurement, as well as thickness measurement of transparent materials in life and material sciences.

Dual-channel interferometer for vibration-resistant optical measurement

A dual-channel interferometer (DCI) is proposed for vibration-resistant optical measurement. The DCI employs a dual-channel interference optical path design, wherein an assistant channel is used to generate dense fringe patterns by introducing a spatial carrier frequency, and the coefficients of the vibration tilt phase plane are then extracted. The sparse fringe patterns of the main channel are combined with the coefficients of the tilt phase plane to calculate the measured phase distribution. This study reports the optical path and principles of the interference system. Simulations are performed using the proposed DCI phase extraction algorithm. To verify the DCI performance, phase measurements are carried out in a vibrating environment, and the results obtained using the proposed method are compared with those obtained using spatial phase-shifting interferometry (SPSI). The experimental results demonstrate that the DCI can effectively overcome the effect of vibration. Unlike spatial carrier frequency interferometry, although the spatial carrier frequency is also introduced in the assistant channel in the proposed DCI method, the dual-channel information extraction algorithm helps eliminate the calibration process of the retrace error before measurement, making this a calibration-free measurement. Moreover, the DCI utilizes environmental vibration to generate a ‘phase shift’, thus not only eliminating the need for a vibration isolation platform but also the need for a precise phase shifting device, with advantages such as structural simplicity, ease of operation, and low cost.

Generation of Bessel beams with 3D‐printed lens

In this article, the 3D-printed dielectric lens is proposed to generate Bessel beam in millimeter-wave band. The dielectric lens is made of many square unit cells with the side length of a half wavelength. The unit cells with different thicknesses generate different insertion phase shift to the transmitted millimeter wave. The insertion phase distribution of the lens is calculated by comparing the phase distributions of the incident Gaussian beam and the desired output Bessel beam. Three types of lenses are simulated and fabricated using 3D printing technology with Nylon. The measured magnitude and phase distributions of zero-order Bessel beam agree with the simulated results very well and the measured phase distributions of the first-order Bessel beam carry orbital angular momentum.

Full-field characterization of helical Bloch modes guided in twisted coreless photonic crystal fiber.

It was recently reported that a photonic crystal fiber (PCF) with no structural core guides light if a permanent chiral twist is introduced by spinning the fiber preform during the draw. The intriguing guidance mechanism behind this novel effect has many remarkable features; for example, it intrinsically supports circularly polarized helical Bloch modes (HBMs) that carry multiple optical vortices, making twisted PCFs of interest in fields such as optical micro-manipulation, imaging, quantum optics, and optical communications. Here we report for the first time, to the best of our knowledge, that a twisted coreless PCF supports not just one but a family of guided HBMs, each member of which has a unique transverse field distribution and harmonic spectrum. By making detailed interferometric measurements of the near-field phase and amplitude distributions of HBMs, and expanding them as a series of Bessel beams, we are able to extract the amplitude of each azimuthal and radial HBM harmonic. Good agreement is found with the numerical solutions of Maxwell's equations. The results shed light on the properties of this curious new optical phenomenon.

New technique for simultaneous measurement of the local solid and gas holdup by using optical fiber probes in the slurry bubble column

Design and scale-up of the slurry bubble columns, as popular multiphase reactors, is complicated because of the complexity of the hydrodynamics of these types of reactors. In fact, to have a good design, precise information about the local hydrodynamic parameters are required. In this study, a new method is developed for simultaneous measuring of the local solid, gas and liquid holdup in the slurry bubble column. Optical fiber probes were used to measure phase distribution inside the bubble column. Our specific calibration procedure enables probes to measure solid concentration in the slurry phase as well. In order to examine the proposed measurement method, a cylindrical plexiglass column with 270 cm height and 29.2 cm diameter was utilized as the slurry column which contained water, glass beads, and air. The mean diameter of the glass beads is 35 µm and the experiments were done with 1% and 3% solid loading (volume solid/volume slurry). To cover both homogeneous and heterogeneous flow regime in the bubble column, air with a wide range of superficial gas velocity (0–22 cm/s) was injected into the slurry phase. The obtained results showed that the axial distribution of the solid particles is not uniform along the column, and a local minimum concentration observed in the middle of the column. In the homogeneous regime, the local solid concentration increased by raising the superficial gas velocity while solid particle distribution was independent of the gas velocity in the heterogeneous flow regime.

Measurement of phase distributions on the surface in subcooled pool boiling of FC-72

Experimental work using IR thermometry was undertaken to obtain phase distributions on the heated surface during subcooled pool boiling of FC-72 at atmospheric pressure. The time-averaged wetted area fraction (WF), the contact line length density (CLD), the frequency between dry-out events, the lifetime of the dry patches, and the dry patch size distributions on the surface were characterized through the observed data. The results confirmed that subcooling of the bulk liquid results in smaller bubbles and increased WF for a given superheat and thus higher critical heat flux (CHF). The subcooled boiling curve could be computed according to the heat flux through the liquid area weighted on WF, and CHF occurred when the WF decreased faster than the increase in heat transfer through the liquid area. CHF mechanisms that have been proposed in the literature were evaluated against the observations.

Object plane detection and phase-amplitude imaging based on transport of intensity equation

By using transport of intensity equation (TIE), phase distribution of an object is retrieved from through-focus intensity images. This technique allows simple and robust phase imaging compared with an interferometric approach. However, it is hard to measure phase distribution when a dynamic object moves in the direction of an optical axis. To clear this problem, autofocusing TIE which is based on local statistics is proposed. The proposed technique achieves the detection of the object plane and the retrieval of a focused object phase distribution simultaneously. In this approach, an object plane is determined by the focusing techniques based on local statistics such as variance, gradient, and Laplacian of amplitude distribution, after phase distribution in an image sensor plane is retrieved by the TIE. The performance of these three statistics is evaluated in numerical and optical experiments, and a suitable focus value is determined for precise phase imaging.

Diffractive triangulation of radiative point sources

We describe a general method to determine the location of a point source of waves relative to a two-dimensional single-crystalline active pixel detector. Based on the inherent structural sensitivity of crystalline sensor materials, characteristic detector diffraction patterns can be used to triangulate the location of a wave emitter. The principle described here can be applied to various types of waves, provided that the detector elements are suitably structured. As a prototypical practical application of the general detection principle, a digital hybrid pixel detector is used to localize a source of electrons for Kikuchi diffraction pattern measurements in the scanning electron microscope. This approach provides a promising alternative method to calibrate Kikuchi patterns for accurate measurements of microstructural crystal orientations, strains, and phase distributions.

Identification of dysregulated microRNA expression and their potential role in the antiproliferative effect of the essential oils from four different Lippia species against the CT26.WT colon tumor cell line

In spite of advances in colorectal cancer treatments, approximately 1.4 million new global cases are estimated for 2015. In this sense, Brazilian plant diversity offers a multiplicity of essential oils as prospective novel anticancer compounds. This study aimed to evaluate the antiproliferative effect of the essential oils from four Lippia species in CT26.WT colon tumor cells, as a measurement of cell cycle phase distribution and microRNA expression. CT26.WT showed cell cycle arrest at G2/M phase after treatment with 100μg/ml of Lippia alba (Mill.) N.E.Br. ex Britton & P. Wilson, Lippia sidoides Cham., and Lippia lacunosa Mart. & Schauer, Verbenaceae, essential oils and, at the same concentration, Lippia rotundifolia Cham. essential oil caused an augment of G0/G1 phase. The miRNA expression profiling shows change of expression in key oncogenic miRNAs genes after treatment. Our findings suggest growth inhibition mechanisms for all four essential oils on CT26.WT cells involving direct or indirect interference on cell cycle arrest and/or oncogenic miRNAs expression.

Three-Dimensional Phase Evaluation in ESPI by Using a Non-Cube Beam-Splitter

Simultaneous measurement of three-dimensional phase distributions by Electronic Speckle Pattern Interferometry (ESPI) is presented using a Non-Cube Beam-Splitter (NCBS). By using the NCBS light from a tested object and from a reference surface can be combined and recorded by a CCD camera. Three carrier patterns are introduced by tilting the reference surface a small angle. The tested object images are recorded before deformation, after titling the reference surface, and then after deformation when three laser beams illuminate the test object and the reference surface at different incident angles respectively. Three carrier patterns and three modulated carrier patterns are obtained by image subtraction. Then three phase maps can be demodulated by using Fourier transform, from which the phase distributions in x, y and z direction are separated respectively. The principle is presented and a typical three-point bending experiment is completed. Experimental results are offered.

Measurement of in-plane strain with dual beam spatial phase-shift digital shearography

Full-field in-plane strain measurement under dynamic loading by digital shearography remains a big challenge in practice. A phase measurement for in-plane strain information within one time frame has to be achieved to solve this problem. This paper presents a dual beam spatial phase-shift digital shearography system with the capacity to measure phase distribution corresponding to in-plane strain information within a single time frame. Two laser beams with different wavelengths are symmetrically arranged to illuminate the object under test, and two cameras with corresponding filters, which enable simultaneous recording of two shearograms, are utilized for data acquisition. The phase information from the recorded shearograms, which corresponds to the in-plane strain, is evaluated by the spatial phase-shift method. The spatial phase-shift shearography system realizes a measurement of the in-plane strain through the introduction of the spatial phase-shift technique, using one frame after the loading and one frame before loading. This paper presents the theory of the spatial phase-shift digital shearography for in-plane strain measurement and its derivation, experimental results, and the technique’s potential.