High-speed CMOS Camera Research Articles

Ultrafast Streaming Camera Platform for Scientific Applications

X-ray computer tomography is a powerful method for nondestructive investigations in many fields. Three-dimensional images of internal structure are reconstructed from a sequence of two-dimensional projections. The polychromatic high density photon flux of modern synchrotron light sources offer hard X-ray imaging with spatio-temporal resolution up to the micrometer and micrometers range. Existing indirect X-ray image detection systems can be adapted for fast image acquisition by high-speed visible-light cameras. In this paper, we present a platform for custom high-speed CMOS cameras with embedded field-programmable gate array (FPGA) processing. This modular system is characterized by a high-throughput PCI Express (PCIe) interface and efficient communication blocks. It has been used to develop a novel architecture for a self-event trigger that increases the effective image frame rate and reduces the amount of received data. Thanks to a low-noise design, high frame rates in the kilohertz range, and high-throughput data transfer, this camera is well suited for ultrafast synchrotron-based X-ray radiography and tomography. The camera setup is accomplished by high-throughput Linux drivers and a seamless integration in our GPU computing framework.

Two-dimensional surface temperature diagnostics in a full-metal engine using thermographic phosphors

An optical system consisting of a rigid borescope was developed to measure surface temperatures inside full-metal internal combustion engines. The measurement principle is predicated on lifetime-based phosphor thermometry of the material Gd3Ga5O12: Cr. The system is designed to resolve the luminescence decay of thermographic phosphors temporally and two-dimensionally by the use of a CMOS high-speed camera. The device allows the visualization of the temperature distribution in an area of 9 mm in diameter. An application of this optical system inside an internal combustion engine is demonstrated, yielding temperature maps under fired and motored conditions in a full-metal engine for the first time.

Extraction of the Geometric Features from the Vacuum Switching Arc Images

Vacuum circuit breaker is one of the major critical components that controls and protects the power system. The breaking capability of the vacuum switch directly affects the safety of the power system. However, the breaking capability of the vacuum switch is determined by the morphological characteristics of the vacuum arc images. In this paper, in order to research the variation of the vacuum arc, a high-speed CMOS camera system is used to collect the vacuum arc images within a short gap (7mm), the morphological characteristics of the vacuum arc images are extracted based on the digital image processing. At last, the variation of the arc is analyzed.

Schlieren measurements in the round cylinder of an optically accessible internal combustion engine

This paper describes the design and experimental application of an optical system to perform schlieren measurements in the curved geometry of the cylinder of an optically accessible internal combustion engine. Key features of the system are a pair of cylindrical positive meniscus lenses, which keep the beam collimated while passing through the unmodified, thick-walled optical cylinder, and a pulsed, high-power light-emitting diode with narrow spectral width. In combination with a high-speed CMOS camera, the system is used to visualize the fuel jet after injection of hydrogen fuel directly into the cylinder from a high-pressure injector. Residual aberrations, which limit the system's sensitivity, are characterized experimentally and are compared to the predictions of ray-tracing software.

Hydrodynamic characteristics and related mass-transfer properties in open-channel flows with rectangular embayment zone

Consecutive groynes and embayments form dead water zones, where sedimentation and high concentrations of pollutants are often observed. It is thus very important to understand the mass and momentum exchange between the main channel and side cavities in rivers and hydraulic engineering structures. The spanwise gradient of the streamwise velocity near the junction produces small-scale turbulent vortices because of shear instability. Furthermore, large-scale horizontal circulation is also generated in the cavity zone. These coherent turbulent structures play a significant role in mass and sediment transfer at the boundary between the mainstream and embayment. However, the relation between turbulence and mass transfer is poorly understood. In this study, we performed particle image velocity and laser-induced fluorescence experiments using a laboratory flume, laser light sheets and a high-speed CMOS camera. We examined the exchange properties of a dye as a function of bed configuration and sedimentation effect. Both primary and secondary gyres were observed in the flat bed and downward-sloping bed, whereas the primary gyre was prevalent in the upward-sloping bed. Moreover, the horizontal circulation strongly affected the mass-transfer properties between the mainstream and side cavity.

Instantaneous 2D imaging of temperature in an engine cylinder with flame combustion

To improve internal combustion engines, it is critical to measure the temperature distribution of their walls. However, only a few studies have quantitatively visualized the instantaneous temperature distribution of a wall exposed to flames. Lifetime-based temperature imaging was performed using a simple measurement system consisting of a non-intensified high-speed CMOS camera, a pulsed UV laser, and a phosphor coated quartz glass covered with a thin metal film. The uncertainty in the temperature measurement was ±2.0°C for measurements of uniform temperature fields in the range 40–250°C. Single-shot wall temperature measurements were demonstrated for combustion by flames in an engine cylinder. This enabled inhomogeneous temperature distributions in the engine with or without flames to be visualized. Even under motoring conditions, there was a large temperature gradient across the side window at the highest position of the piston. The side window temperature decreased near the intake valve. The intake gas flow had a cooling effect and the intake pressure affected the temperature distribution. The engine speed and the coolant temperature increased the magnitude of temperature but they did not affect the overall temperature distribution, i.e. the spatial distribution and the spatial gradient of the temperature. The instantaneous temperature of the top of the piston was visualized in the transient process after firing had commenced.

Simultaneous measurement of dissolved oxygen concentration and velocity field in microfluidics using oxygen-sensitive particles

This paper reports a technique for measuring the velocity and dissolved oxygen concentration (DOC) fields simultaneously in a micro-scale water flow using oxygen-sensitive particles (OSP) and a conventional microparticle image velocimetry method. The OSP were fabricated using a dispersion polymerization method by synthesizing platinum (II) octaethyporphyrin (PtOEP) with polystyrene, and used as tracer particles and oxygen sensors. An ultraviolet light-emitting diode with a wavelength of 385 nm was used as the excitation light source, and phosphorescence images of OSP were captured on a CMOS high-speed camera. The interrogation window concept was used to measure the DOC in water from the dispersed phosphorescence intensity distribution of OSP. The Stern–Volmer equations in the interrogation windows were obtained from in situ calibration. Water containing OSP with DOC values of 0 and 100 % were injected into a Y-shaped microchannel using a double loading syringe pump. The velocity and DOC field over the entire channel area were quantified.

Análise da oscilação da poça de solda em P-GMAW por meio de processamento de imagens obtidas por perfilografia

Este artigo apresenta uma metodologia de estudo da oscilação da poça de solda que permite obter as frequências de oscilação da poça tanto por sinais de tensão quanto por análise das imagens. O intenso brilho do arco é reduzido utilizando-se a técnica de perfilografia, e as imagens são obtidas a 1000 fotos por segundo por uma câmera CMOS de alta velocidade. A geometria da poça é visualizada em perfil e são obtidos espectros de frequência por transformada rápida de Fourier por meio de processamento das imagens em MATLAB. O processo de soldagem experimentado foi o GMAW pulsado com e sem a chamada "corrente de destacamento". Os resultados mostram que é possível medir a oscilação da poça por esta metodologia e até mesmo pode ser mais confiável a quantificação da oscilação pelas imagens do que pela a análise do sinal de tensão.

Instantaneous phosphor thermometry applicable to walls exposed to flames

It is important to be able to measure the temperature distribution of walls that are exposed to high temperatures, such as fire walls and internal combustion engines, in order to improve their performance. However, only a few studies have quantitatively visualized the two-dimensional temperature distribution of walls exposed to flames. Phosphor thermometry is a key approach to measuring the temperature distributions of walls, since phosphorescence lifetimes and spectra vary over a wide temperature range.In this study, the luminescence properties of the phosphor, Y2O2S:EuSm, were investigated. Although the temperature sensitivity of its spectral shape was only 0.008%/°C in the range 50–210°C, that of its luminescence lifetime was 0.78%/°C. Lifetime-based phosphor thermometry was performed using a simple experimental setup consisting of a non-intensified high-speed CMOS camera, a pulsed UV laser, and a phosphor coated with a thin metal film. It was found that the excitation power had little effect on the phosphor lifetime and that the metal film did not affect the phosphorescence lifetime. The temperature measurement uncertainty was determined to be ±4.4°C from measurements of uniform temperature fields. Instantaneous wall temperature measurements were demonstrated during flame combustion in a rapid compression expansion machine. The measured temperatures agreed with those measured by a thin thermocouple. The proposed system is capable of measuring the instantaneous wall temperature even in a combustion chamber.

Coherent beam combination of adaptive fiber laser array with tilt-tip and phase-locking control

We present an experimental study on tilt-tip (TT) and phase-locking (PL) control in a coherent beam combination (CBC) system of adaptive fiber laser array. The TT control is performed using the adaptive fiber-optics collimator (AFOC), and the PL control is realized by the phase modulator (PM). Cascaded and simultaneous controls of TT and PL using stochastic parallel gradient descent (SPGD) algorithm are investigated in this paper. Two-fiber-laser-, four-fiber-laser-, and six-fiber-laser-arrays are employed to study the TT and PL control. In the cascaded control system, only one high-speed CMOS camera is used to collect beam data and a computer is used as the controller. In a simultaneous control system one high-speed CMOS camera and one photonic detector (PD) are employed, and a computer and a control circuit based on field programmable gate array (FPGA) are used as the controllers. Experimental results reveal that both cascaded and simultaneous controls of TT using AFOC and PL using PM in fiber laser array are feasible and effective. Cascaded control is more effective in static control situation and simultaneous control can be applied to the dynamic control system directly The control signals of simultaneous PL and TT disturb each other obviously and TT and PL control may compete with each other, so the control effect is limited.

1206 スプラッシュエロージョンに関する研究(OS12 生物・生体に関する流れ,OS12 生物・生体に関する流れ)

The objective of this study is to understand the process of splash erosion due to impacting of raindrop onto soil. This is investigated experimentally using a high speed CMOS camera. To understand the phenomena qualitatively, the soil model was developed. The model simulates the fine sand where the diameter of soil particle is 0.1mm. A dent was formed by the impact of droplet on the soil. The droplet deformed with the impacting, and formed the film-flow. The suspension of soil particle was caused with the shear force due to the film-flow. The suspended particle was not entrained into film-flow. The suspended particle was initially settled beside the film-flow. Thus, the suspended particle was not wet.

High Speed Magnetic Tweezers at 100KHz with Superluminescent Diode Illumination

Magnetic tweezers apply force to single DNA molecules to measure changes in DNA length as a function of time. The technique is ideally suited to explore the dynamics of biophysical processes such as DNA unzipping by helicase motor proteins due to the constant force applied to the DNA. However, instrumental improvements are needed to resolve the length and time scales of single enzymatic steps. Here, we introduce a superluminescent diode as the illumination source and a high-speed CMOS camera as the optical detector to achieve magnetic tweezing of DNA at a bandwidth of 100 kHz. We show how GPU-accelerated video processing can be used to determine three-dimensional particle positions from a series of video frames with a spatial resolution below 1 Angstrom. We demonstrate the quantitative capabilities of this instrument by measuring the drag coefficient of a magnetic bead and the stiffness of a tethered DNA molecule at a corner-frequency of 1 kHz, and by measuring DNA hairpin dynamics that were previously characterized in optical tweezer experiments.

Multiple CMOS Intersection Measuring System Modeling and Analysis

Multiple high speed CMOS cameras composing intersection system to splice large effect field of view(EFV). The key problem of system is how to locate multiple CMOS cameras in suitable position. Effect field of view was determined according to size, quantity and dispersion area of objects, so to determine camera position located on below, both sides and ahead to moving targets. This paper analyzes effect splicing field of view, operating range etc through establishing mathematical model and MATLAB simulation. Location method of system has advantage of flexibility splicing, convenient adjustment, high reliability and high performance-price ratio.

Frequency Identification of Vibration Signals Using Video Camera Image Data

This study showed that an image data acquisition system connecting a high-speed camera or webcam to a notebook or personal computer (PC) can precisely capture most dominant modes of vibration signal, but may involve the non-physical modes induced by the insufficient frame rates. Using a simple model, frequencies of these modes are properly predicted and excluded. Two experimental designs, which involve using an LED light source and a vibration exciter, are proposed to demonstrate the performance. First, the original gray-level resolution of a video camera from, for instance, 0 to 256 levels, was enhanced by summing gray-level data of all pixels in a small region around the point of interest. The image signal was further enhanced by attaching a white paper sheet marked with a black line on the surface of the vibration system in operation to increase the gray-level resolution. Experimental results showed that the Prosilica CV640C CMOS high-speed camera has the critical frequency of inducing the false mode at 60 Hz, whereas that of the webcam is 7.8 Hz. Several factors were proven to have the effect of partially suppressing the non-physical modes, but they cannot eliminate them completely. Two examples, the prominent vibration modes of which are less than the associated critical frequencies, are examined to demonstrate the performances of the proposed systems. In general, the experimental data show that the non-contact type image data acquisition systems are potential tools for collecting the low-frequency vibration signal of a system.

Velocity measurement accuracy in optical microhemodynamics: experiment and simulation

Micro particle image velocimetry (µPIV) is a common method to assess flow behavior in blood microvessels in vitro as well as in vivo. The use of red blood cells (RBCs) as tracer particles, as generally considered in vivo, creates a large depth of correlation (DOC), even as large as the vessel itself, which decreases the accuracy of the method. The limitations of µPIV for blood flow measurements based on RBC tracking still have to be evaluated. In this study, in vitro and in silico models were used to understand the effect of the DOC on blood flow measurements using µPIV RBC tracer particles. We therefore employed a µPIV technique to assess blood flow in a 15 µm radius glass tube with a high-speed CMOS camera. The tube was perfused with a sample of 40% hematocrit blood. The flow measured by a cross-correlating speckle tracking technique was compared to the flow rate of the pump. In addition, a three-dimensional mechanical RBC-flow model was used to simulate optical moving speckle at 20% and 40% hematocrits, in 15 and 20 µm radius circular tubes, at different focus planes, flow rates and for various velocity profile shapes. The velocity profiles extracted from the simulated pictures were compared with good agreement with the corresponding velocity profiles implemented in the mechanical model. The flow rates from both the in vitro flow phantom and the mathematical model were accurately measured with less than 10% errors. Simulation results demonstrated that the hematocrit (paired t tests, p = 0.5) and the tube radius (p = 0.1) do not influence the precision of the measured flow rate, whereas the shape of the velocity profile (p < 0.001) and the location of the focus plane (p < 0.001) do, as indicated by measured errors ranging from 3% to 97%. In conclusion, the use of RBCs as tracer particles makes a large DOC and affects the image processing required to estimate the flow velocities. We found that the current µPIV method is acceptable to estimate the flow rate on the condition that the measurement takes place at the equatorial plane of the vessel. Otherwise, it is not an appropriate method to estimate the shape of the velocity profile.

Multi-point, high-speed passive ion velocity distribution diagnostic on the Pegasus Toroidal Experiment

A passive ion temperature polychromator has been deployed on Pegasus to study power balance and non-thermal ion distributions that arise during point source helicity injection. Spectra are recorded from a 1 m F/8.6 Czerny-Turner polychromator whose output is recorded by an intensified high-speed camera. The use of high orders allows for a dispersion of 0.02 Å/mm in 4th order and a bandpass of 0.14 Å (~13 km/s) at 3131 Å in 4th order with 100 μm entrance slit. The instrument temperature of the spectrometer is 15 eV. Light from the output of an image intensifier in the spectrometer focal plane is coupled to a high-speed CMOS camera. The system can accommodate up to 20 spatial points recorded at 0.5 ms time resolution. During helicity injection, stochastic magnetic fields keep T(e) low (100 eV) and thus low ionization impurities penetrate to the core. Under these conditions, high core ion temperatures are measured (T(i) ≈ 1.2 keV, T(e) ≈ 0.1 keV) using spectral lines from carbon III, nitrogen III, and boron IV.

Investigation of the Performance of Spectral Domain Optical Doppler Tomography with High-speed Line Scanning CMOS Camera and Its Application to the Blood Flow Measurement in a Micro-tube

In this study, the feasibility of spectral domain optical Doppler tomography for measuring blood flow characteristics in a micro-tube was demonstrated through several experiments. The use of an SD-ODT system in blood flow measurement can provide high resolution images (5 microns resolution). We prepared three capillary tubes to reveal the effect of different concentrations of hematocrit ratio (HR). One tube serves as the control. The two other tubes contained different concentrations of HR (5%, 25%). Three different capillary tube inlet flow velocities were tested in the present study. The Reynolds number (Re) which is based on the capillary tube inner diameter ranges from Re=6 to 48. We calculated a Doppler shift of the power spectrum of the temporal interference fringes with Kasai autocorrelation function to achieve the velocity profile of the flow. As a result, SD-ODT systems could not detect the cell depletion layer in the present study due to the limitation of spatial resolution. Nevertheless, these systems were proven to be capable of observing the RBCs of blood.

Diameter-speed relation of sprite streamers

Propagation and splitting of sprite streamers has been observed at high temporal and spatial resolution using two intensified high-speed CMOS cameras recording at 10 000 and 16 000 frames per second. Concurrent video recordings from a remote site provided data for triangulation allowing us to determine accurate altitude scales for the sprites. Diameters and speeds of the sprite streamers were measured from the high-speed images, and the diameters were scaled to the reduced diameters based on the triangulated locations. The sprite streamers with larger reduced diameter move faster than those with smaller diameter; the relation between the reduced diameter and speed is roughly linear. The reduced diameters at ≈65–70 km altitude are larger than streamer diameters measured at ground pressure in laboratory discharges indicating a deviation from the similarity law possibly due to the effects of the photoionization and an expansion of the streamer head along its propagation over a long distance. The reduced diameter and speed of the sprite streamers agree well with the diameter–velocity relation proposed by Naidis (2009 Phys. Rev. E 79 057401), and the peak electric field of the sprite streamers is estimated to be approximately 3–5 times the breakdown threshold field.

마이크로 레이저 형광 여기법을 이용한 미세채널 내부에서의 산소 확산에 대한 정량적 가시화

In the present study, oxygen transfer process across gas-liquid interface in a Y-shape micro- channel is quantitatively visualized using the micro laser induced fluorescence (µ-LIF) technique. Dif- fusion coefficient of Oxygen (DL) is estimated based on the experimental results and compared to its the- oretical value. Tris ruthenium (II) chloride hexahydrate was used as the oxygen quenchable fluorescent dye. A light-emitting diode (LED) with wavelength of 450 nm was used as the light source and phos- phorescence images of fluorescent dye were captured by a CMOS high speed camera installed on the microscope system. Water having dissolved oxygen (DO) value of 0% and pure oxygen gas were injected into the Y-shaped microchannel by using a double loading syringe pump. In-situ pixel-by-pixel calibration was carried out to obtain Stern-Volmer plots over whole flow field. Instantaneous DO concentration fields were successfully mapped according to Stern-Volmer plots and DL was calculated as 2.0675×10 -9 m 2 /s.

Time-resolved scanning stereo PIV measurement of three-dimensional velocity field of highly buoyant jet

The time-resolved scanning stereo PIV system, which consists of a CW Nd:YAG laser, two high-speed CMOS cameras, a Galvano mirror and a pulse controller, is developed for time-sequential three-dimensional velocity field measurement of liquid flow. This experimental technique is validated by the measurement of a laminar non-buoyant jet, and is applied to the 3D velocity measurement of a highly buoyant jet at Froude number 0.3 and Reynolds number 200, which satisfy the inflow condition due to the unstable density gradient. The measurement of statistical properties of velocity field shows the growth of turbulence intensities near the nozzle exit, which indicates the presence of inflow motion near the nozzle exit due to the unstable density gradient. The vorticity contours about the horizontal axis shows the presence of counter-rotating vortices on both sides of the jet centerline, while the vorticity contour about the vertical axis indicates the presence of spiral growth of a pair of vortices along the jet centerline. The growth of the spiral structure along the jet centerline is recognized in the iso-vorticity contours obtained from the time-resolved measurement of 3D velocity field.