Fast Camera Research Articles

Non-Contact Vibration Detection Software and Hardware Design with Image Processing Method to Reveal Substantial Changes in Structures and Systems

Many types of equipment are used for vibration detection in buildings and systems. However, these systems have their own problems. In this article, a combined software and hardware system is designed for the solution of these problems. The system has been designed with the Motion Magnification Analysis (MMA) method, which stands out in the literature studies. C # language and .NET environment have been used as software. The Accord library was used for the image processing process. These libraries were also used for the analysis of subspaces and components of the image. During the study, three new algorithms that have not been applied in the past and not in the literature have been developed. The first of these is the derivative of the method known as Color Magnification, which analyzes the color space. The second is the derivative of the Motion Magnification method, which magnifies the vibration to the visible level. And the third one is the Frequency Determination algorithm, which enables frequency measurement. With this solution, it is provided to make an analysis of the images taken with devices with relatively slow cameras such as mobile phones/tablets as well as fast cameras. All results were compared with a touchable vibration analyzer for benchmarking and showed that the proposed method was successful.

Space-and time-resolved optical investigations on ns-laser produced plasmas on various geological samples

Experimental and theoretical investigations were performed on transient plasmas generated by ns-laser ablation on ten mineral samples. Space-and time-resolved optical emission spectroscopy and ICCD fast camera imaging were implemented to understand the kinetics of the ablated particles and how the samples physical properties can be reflected by those of the plasma plume. Strong correlations were found between the global and individual plasma velocity and the melting temperature of the geomaterials. The thermal energy of the plasma expressed through the excitation temperature of the ejected particle is correlated with the same target physical parameter, results corelated with the presence of strong thermal ejection mechanisms. To better understand the global empirical laws, we implemented the fractal model to interpret the results. The model manages to emulate the target-plasma correlations using a multifractal hydrodynamic approach and adequately calibrating the theoretical model on the empirical tools used to describe the laser produced plasmas.

Characterization of planar phosphorescence based oxygen sensors on a TCSPC-PLIM macro-imager

A set of phosphorescent materials were evaluated using a new macro-imager based on fast time-stamping Tpx3Cam camera with phosphorescent lifetime imaging (PLIM) capabilities. The near-infrared emitting O2-sensitive dye PtBP was embedded in several polymers having different permeability for O2 and applied as solid-state coatings on polyester film support. These sensor materials were placed on a temperature-controlled stage of the imager and imaged under pulsed excitation with a 627 nm LED. The resulting PLIM images showed good uniformity, accuracy and contrast of measured lifetime values for the different phosphorescent materials, and the anticipated lifetime changes with altered temperature or oxygenation conditions, proving the dynamic mechanism of quenching by O2. By imaging the coatings with decreasing dye concentration, stability and limits of sensitivity of the PLIM mode were determined and compared with intensity-based imaging. Several commercial O2 sensors were also imaged and compared with the hand-made sensors, while lifetime measurements on the new imager were compared with those performed on the confocal TCSPC-PLIM microscope.

Real-Time Video Imaging of Mechanical Motions of a Single Molecular Shuttle with Sub-Millisecond Sub-Angstrom Precision

Abstract Miniaturized machines have open up a new dimension of chemistry, studied usually as an average over numerous molecules or for a single molecule bound on a robust substrate. Mechanical motions at a single molecule level, however, are under quantum control, strongly coupled with fluctuations of its environment — a system rarely addressed because an efficient way of observing the nanomechanical motions in real time is lacking. Here, we report sub-millisecond sub-Å precision in situ video imaging of a single fullerene molecule shuttling, rotating, and interacting with a vibrating carbon nanotube at 0.625 milliseconds(ms)/frame or 1600 fps, using an electron microscope, a fast camera, and a denoising algorithm. We have achieved in situ observation of the mechanical motions of a molecule coupled with vibration of a carbon nanotube with standard error as small as 0.9 millisecond in time and 0.01 nm in space. We have revealed rich molecular dynamics, where motions are non-linear, stochastic and often non-repeatable, and a work and energy relationship at a molecular level previously undetected by time-averaged measurements or microscopy. The molecular video recording at a 1600-fps rate exceeds by 100 times the previous records of continuous recording of molecular motions.

Machining of Aluminums Alloys with the Addition of Reinforced Carbide Phase

This paper presents the results of the processes of treating aluminum matrix casting materials with the addition of a ceramic phase. The matrix of the composite material was an Al-Si7 casting alloy with addition of 2 mass% Mg. The volume fraction of the reinforcing phase in the form of silicon carbide ranged from 5 to 15 vol.%. Preliminary machining tests were carried out at the Mori Seiki NL2000SY turning and milling center. The cutting properties were evaluated during longitudinal turning. Cutting tests were carried out using tools made of polycrystalline diamond, regular boron nitride, and cemented carbides. The nature of VBB wear was checked in accordance with PN-ISO 3685:1996. The influence of machining parameters (cutting speed, feed, cutting depth) on the value of cutting tools temperature was determined. An analysis of the chip shaping mechanism during machining was performed at various cutting parameters. The tests were carried out using the FLIR A655 thermal imaging camera and the fast Phantom MIRO M310 fast camera. Cast composite materials were also subjected to the processes of waterjet cutting, EDM cutting, and EDM drilling (EDM electro discharge machining).

SiamAtt: Siamese attention network for visual tracking

Visual attention has recently achieved great success and wide application in deep neural networks. Existing methods based on Siamese network have achieved a good accuracy–efficiency trade-off in visual tracking. However, the training time of Siamese trackers becomes longer for the deeper network and larger training data. Further, Siamese trackers cannot predict the target location well in fast motion, full occlusion, camera motion, and similar object scenarios. Due to these difficulties, we develop an end-to-end Siamese attention network for visual tracking. Our approach is to introduce an attention branch in the region proposal network that contains a classification branch and a regression branch. We perform foreground–background classification by combining the scores of the classification branch and the attention branch. The regression branch predicts the bounding boxes of the candidate regions based on the classification results. Furthermore, the proposed tracker achieves the experimental results comparable to the state-of-the-art tracker on six tracking benchmarks. In particular, the proposed method achieves an AUC score of 0.503 on LaSOT, while running at 40 frames per second (FPS).

Evaluation of a position-sensitive prototype detector unit for fast neutron imaging and spectroscopy

A novel fast neutron scatter camera with capabilities of neutron imaging and spectroscopy is under development. The detection principle is based on multiple neutron–proton (n–p) elastic scattering interactions in organic scintillator. In order to improve position measurement accuracy of recoil protons, a position-sensitive prototype detector unit has been designed and characterized experimentally. The presented detector unit consisted of a plastic scintillator sheet of 10 cm × 10 cm × 1 cm dimensions and two groups (6 × 2) of wavelength-shifting fibers with orthogonal directions embedded into grooves on two opposite scintillator surfaces. Scintillation signals were read out by silicon photomultipliers (SiPMs). A collimated Sr-90 radioactive source was utilized for system calibration and position resolution measurement. Light output of the unidimensional six fiber channels from one side of the detector unit was calibrated to be 14.45 photoelectrons per MeVee. Position resolution of the detector unit was measured to be 0.35–0.44 times fiber pitch, corresponding to 5.48 mm for proton recoil energy interval of 1.63–2.60 MeV, and 4.60 mm for proton recoil energy interval of 4.82–5.50 MeV. Energy threshold for recoil proton localization was estimated to be 1.18 MeV. The results shown satisfy basic requirements of the scatter camera, while space exists for further improvements. The positioning performance optimization consists of three aspects. The first one is to increase the fiber diameter so as to reduce signal loss. The second one is to depress dark rate of the SiPMs. The last one is to decrease the number of channels involved in position reconstruction by narrowing the scintillation signal distribution function of the detector unit.

Fast Camera Analysis of Plasma Instabilities in Hall Effect Thrusters Using a POD Method under Different Operating Regimes

Even after half a century of development, many phenomena in Hall Effect Thrusters are still not well-understood. While numerical studies are now widely used to study this highly non-linear system, experimental diagnostics are needed to validate their results and identify specific oscillations. By varying the cathode heating current, its emissivity is efficiently controlled and a transition between two functioning regimes of a low power thruster is observed. This transition implies a modification of the axial electric field and of the plasma plume shape. High-speed camera imaging is performed and the data are analysed using a Proper Orthogonal Decomposition method to isolate the different types of plasma fluctuations occurring simultaneously. The low-frequency breathing mode is observed, along with higher frequency rotating modes that can be associated to rotating spokes or gradient-induced instabilities. These rotating modes are observed while propagating outside the thruster channel. The reduction of the cathode emissivity beyond the transition comes along with a disappearance of the breathing mode, which could improve the thruster performance and stability.

An experimental study of water BLEVE

A boiling liquid expanding vapour explosion (BLEVE) is a physical explosion caused by a sudden rupture of a vessel containing superheated liquid. A BLEVE can occur with many types of fluids and is not an exclusive phenomenon for flammable liquefied gases such as propane or butane. Other superheated liquids suffering a fast depressurization at high temperature may entail a BLEVE, such as water in steam generation systems. Several pieces in literature suggest that superheated water may produce a BLEVE, but little experimental data can be found on that topic.The aim of this work was to perform water BLEVE tests with a 14 L pressure vessel designed on purpose to produce high superheated liquid water (290 °C; 75 bar) and to trigger a BLEVE through calibrated rupture disks. Pressure sensors were set in the vessel to measure the internal phase change pressure dynamics and other aerial overpressure sensors were put around the relief rupture disk to capture the blast wave. Temperature of water was also recorded, and a fast camera (Phantom V2512) was used to see the phenomenon.Data show clearly the pressure recovery due to rapid boiling in the vessel. Explosive boiling did not add additional internal pressure force on the containment. Two main blast waves were observed, they were strongly related with outlet orifice area but little dependant on filling ratio. The two phase jet reached a 20 m range.

Subjective Evaluation of User Quality of Experience for Omnidirectional Video Streaming

This paper reports on the results of subjective testing of user Quality of Experience (QoE) for omnidirectional video (ODV) streaming quality. The test was conducted among 20 test subjects who watched three ODVs using a Head Mounted Display (HMD) system. The length of the videos was between two and three minutes. The first video was used for training purposes and contained no quality degradations. The quality of the other two ODVs was degraded by manipulating the resolution or by introducing different frame drop patterns. While watching the pre-prepared videos the subjects indicated if they noticed the changes in the quality and then rated it. After watching each video, the subjects completed a separate questionnaire, which evaluated their level of enjoyment and discomfort with the video. The results showed that the degradation of both objective parameters (video resolution and frame rate) impacted the subjects’ perception of quality; however, the impact was somewhat alleviated in ODV which contained dynamic scenes and fast camera movements.

First speckle interferometric measurements of binary stars at the Observatorio Astrofísico Guillermo Haro

ABSTRACT In this paper, we present the first multiband speckle interferometric measurements of binary stars performed using the 2.1 m telescope of the Observatorio Astrofísico Guillermo Haro, Cananea, Sonora, México. We describe here FICCO: Fast Imaging Camera for Cananea Observatory, a new instrument developed to perform speckle observations from the Northern Hemisphere. We tested this new instrument with objects from the Washington Double Star Catalog, that were observed during three runs allocated in 2019. We report 480 astrometric measurements of 138 pairs, with angular separations ranging from 0.06 to 5.76 arcsec, including 347 measurements with separations smaller than 1 arcsec. We estimated a mean error in separation of 14 mas, 1.6° in position angle, and 0.45 mag for the magnitude difference. We confirmed 12 double stars discovered by Hipparcos. Finally, we present a correction to four previously published orbital solutions of visual binaries.

Laser-generated Cu plasma in vacuum and in nitrogen gas

A pulsed ns IR laser at about 1010 W/cm2 intensity is employed to irradiate a Cu target placed in a vacuum and in nitrogen gas. The produced plasma is characterized in terms of emitted ions and photons as a function of the nitrogen pressure in the chamber. The mechanisms of ion gas interactions are investigated in terms of Cu ion energy loss and X-ray attenuation using an ion collector and a SiC detector. A fast CCD camera in the visible region has produced the collision images of the ions with the nitrogen molecules. A plasma temperature of about 44 eV, an emission of soft X-rays up to about 100 eV, an ablation yield of about 2.4 × 1015 atoms/pulse, a maximum Cu ion acceleration of 1.4 keV and a maximum ionization up to Cu9+ were measured in high vacuum.

Cathodoluminescent screen imaging system for seeded blob detection in toroidal plasma experiment.

We designed and built a diagnostic based on a cathodoluminescent screen for the detection of turbulent plasma structures with high spatial resolution. The screen is coated with a low threshold energy cathodoluminescent powder that emits light when exposed to a plasma. The emitted light is imaged with a fast frame camera combined with an image intensifier and an optical bandpass filter. The diagnostic is used to study turbulent structures and seeded blobs. The results are analyzed with pattern recognition algorithms to track the turbulent structures and study their evolution in time.

Imaging 55Fe electron tracks in a GEM-based TPC using a CCD readout

Images of resolved 5.9 keV electron tracks produced from 55Fe X-ray interactions are presented for the first time using an optical readout time projection chamber (TPC) . The corresponding energy spectra are also shown, with the FWHM energy resolution in the 30–40% range depending on gas pressure and gain. These tracks were produced in low pressure carbon tetrafluoride (CF4) gas, and imaged with a fast lens and low noise CCD camera system using the secondary scintillation produced in GEM/THGEM amplification devices. The GEM/THGEMs provided effective gas gains of ≳ 2 × 105 in CF4 at low pressures in the 25–100 Torr range. The ability to resolve such low energy particle tracks has important applications in dark matter and other rare event searches, as well as in X-ray polarimetry. A practical application of the optical signal from 55Fe is that it provides a tool for mapping the detector gain spatial uniformity.

In vivo imaging of the human cornea with high-speed and high-resolution Fourier-domain full-field optical coherence tomography.

Corneal evaluation in ophthalmology necessitates cellular-resolution and fast imaging techniques that allow for accurate diagnoses. Currently, the fastest volumetric imaging technique is Fourier-domain full-field optical coherence tomography (FD-FF-OCT), which uses a fast camera and a rapidly tunable laser source. Here, we demonstrate high-resolution, high-speed, non-contact corneal volumetric imaging in vivo with FD-FF-OCT that can acquire a single 3D volume with a voxel rate of 7.8 GHz. The spatial coherence of the laser source was suppressed to prevent it from focusing on a spot on the retina, and therefore, exceeding the maximum permissible exposure (MPE). The inherently volumetric nature of FD-FF-OCT data enabled flattening of curved corneal layers. The acquired FD-FF-OCT images revealed corneal cellular structures, such as epithelium, stroma and endothelium, as well as subbasal and mid-stromal nerves.

Cylindrical image mosaic method based on fast camera calibration in multi-scene

A cylindrical image mosaic method based on fast camera calibration in multi-scene is proposed to solve the problems of scene limitation and complex calibration process in image mosaic using camera calibration parameter. Firstly, the accurate corner feature of checkerboard calibration board is used to make it in the overlapping field of view of two adjacent images. Then, the image sequence is pre-processed by corner extraction, precision and matching, so that the registration parameters between the images to be stitched can be solved accurately and quickly. After that, the cylindrical projection is used to maintain the visual consistency of the images, and the multi-band fusion is used to retain the details of the images. Subsequently, the images are stitched using registration parameters obtained by calibration. Finally, the whole system is built on a low-power embedded platform to accomplish fast calibration and mosaic process based on calibration parameters in multi-scene. The experiment results show that the proposed method can accomplish camera calibration quickly and accurately in indoor and tunnel scenarios, and the image mosaic process is time-consuming. Meanwhile, it can ensure better stitching accuracy and imaging effect, and has strong robustness.

Fast camera spatial characterization of photonic polarization entanglement

Scalable technologies to characterize the performance of quantum devices are crucial to creating large quantum networks and quantum processing units. Chief among the resources of quantum information processing is entanglement. Here we describe the full temporal and spatial characterization of polarization-entangled photons produced by Spontaneous Parametric Down Conversions using an intensified high-speed optical camera, Tpx3Cam. This novel technique allows for precise determination of Bell inequality parameters with minimal technical overhead, and for new characterization methods for the spatial distribution of entangled quantum information. The fast-optical camera could lead to multiple applications in Quantum Information Science, opening new perspectives for the scalability of quantum experiments.

Application of dynamic mode decomposition to rotating structures in detached linear plasmas

Dynamic mode decomposition (DMD) was applied to time-series snapshots of dynamic behavior in detached plasmas with a fast framing camera in the linear plasma device NAGDIS-II. The DMD extracted radial plasma ejection and Er×B rotation structures, which are associated with blob-like plasma structures. Besides, we investigated the influences from neutral gas pressure on the growth rates of the DMD modes. By increasing the neutral gas flow rate in the detached plasma, the growth rate of rotation mode became larger while the frequency decreased. The results indicated that the ejected plasma existed for a longer time in the periphery region. It is likely due to the fact that the ratio of the radial velocity to the rotation velocity of the ejected plasma decreased.

Generation and Diagnostics of Pulse Plasma Flows

Pulsed plasma accelerators are widely used for the production of high-temperature pulsed plasma flows for fundamental and practical applications. The basic parameters of pulsed plasma accelerators are the characteristics of the external electric and magnetic circuits, as well as the structural and energy properties of the plasma flow. This work aims to characterize an IPU-30 pulsed plasma accelerator. The triple Langmuir probe method, calorimetric plasma energy density measurements, Rogowski coil, and high-speed visible imaging with a Phantom VEO710S fast camera are used to diagnose the pulsed plasma obtained in the IPU-30. The local plasma parameters such as electron temperature and density, the energy density of the pulsed plasma flow, pulsed plasma current, and also discharge current are experimentally obtained at different discharge voltages and air pressure in the chamber. The typical waveforms of the triple probe and Rogowski coil are presented in the form of oscillograms. The images of plasma formation in the discharge gap are obtained and the velocity of a pulsed plasma flow is measured.

Determination and validation of Karagozian-Case Concrete constitutive model parameters for numerical modeling of dolomite rock

The paper presents a methodology for the calibration of a Karagozian-Case Concrete (KCC) constitutive model for the simulation of dolomite rock. A series of basic experiments are performed under static and dynamic loading conditions, including uniaxial compression tests, triaxial compression tests at different confining pressures, and Brazilian tests for determining indirect tensile strength. A step-by-step procedure for determining the failure surface, the equation of state and damage parameters is proposed. The acquired data are validated using numerical simulations under loading conditions corresponding to those used in the experimental tests. A mesh sensitivity study is briefly discussed. Quantitative and qualitative comparisons of the numerical outcomes and experimental data reveal a good correlation. The KCC model reliably reproduces the rock behavior, including increased strength due to stress triaxiality and kinematic hardening with an increased strain rate. The damage evolution in the material is similar to that recorded by a fast camera during the experiments. The validated model will be used for modeling borehole blasting in further investigations.