This PDF file contains the front matter associated with SPIE Proceedings Volume 11051, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

The use of a Sanderson prism is an inexpensive way in which to undertake shearing interferometric studies. It consists of a thin plate of polycarbonate material which exhibits birefringent properties when stressed. It is placed in a rig under conditions of pure bending, and is positioned in a conventional schlieren visualization set up. This results in a series of coloured fringes in the image plane. If a flow of variable density is placed in the test section the light is deflected from one fringe to another. Images can be generated in both infinite and finite fringe modes. The current study examines the flow field generated by the deflection and rupture of thin elastic sheets attached to the exit of a shock tube, as a pressure relief device. This is similar to the use of a burst disk conventionally used as a safety device to prevent excessive pressure buildup in a vessel such as impact of a shock wave. The use of an elastic membrane rather than a metal plate is to establish the potential to reduce the magnitude of reflected waves back into the system. This paper concentrates on the complex external transient flow, in terms of the shock wave exiting profiles and flow evolution, the stretching and rupture of the membrane, and the final flow following rupture.

Cavitation bubbles, when correctly tuned, may provide interesting mechanical and chemical effects to their surroundings owing to their violent collapse. Such an event may produce high-speed liquid jetting, extreme heating, as well as pressures of thousands of atmospheres. These phenomena are responsible for the severe erosion harming hydraulic machinery, but they also present interesting traits to harness in cleaning, sonochemistry, biomedical applications, among others. Here, we present experimental observations on the high pressures produced by spherically collapsing cavitation bubbles. Filming at 10 million frames/s allows for the disclosure of details on the high pressures (kbar-level) in the liquid near the bubble in its final collapse stages that precede the shock wave emission, confirming the century-old prediction of Lord Rayleigh.

High-speed videogrammetry has gradually become the important measurement technique in civil engineering material testing and structure monitoring. This paper presents a robust videogrammetric approach to monitor and analyse the spatial deformations of structures in large-scale shaking table tests, which consists of three main parts as follows. (1) A videogrammetry system with multiple high-speed cameras is established to measure three-dimensional (3D) morphological changes of large structures. (2) An accurate target recognition algorithm is introduced into the measurement scheme, and then the target tracking and matching strategy is proposed in our scheme to calculate the sequential image coordinates of the target points in the high-speed image sequences. (3) The 3D coordinates of the target points can be obtained by the videogrammetric analysis algorithms, and the key structural deformation parameters can be further calculated through the spatiotemporal analysis of the sequential point coordinates. The shaking table test of largescale wooden pagoda as an empirical test is performed to demonstrate the feasibility and reliability of the whole highspeed videogrammetric technique. The experimental results show that the proposed approach can achieve sub-millimeter positioning accuracy of the artificial targets with comparison of high-accuracy total station. Moreover, the credibility of the measured displacement results is further verified by comparison with the results of the high-accuracy displacement sensor.

This paper investigates the application of CMOS-based ultra-high speed camera in characterising materials under dynamic tensile loading. A single Hopkinson bar test is used to induce an axial stress wave in the sample and a grid pattern is filmed during the test to obtain time-resolved full-field kinematic measurements. Then the acceleration fields are used to reconstruct the stress information and identify material response. Quasi-brittle materials (e.g. rocks and concrete) present a particular experimental challenge due to small deformation and low stress level at failure. The Shimadzu HPV-X2 acquisition system has been applied for such purpose and its performance was investigated by first performing a spalling test on an aluminium benchmark sample and then applied to testing ordinary concrete.

Light-in-flight recording by holography is a technique for recording a motion picture of light propagation. The technique uses an ultrashort pulsed laser to record a hologram. An ultrashort light pulse emitted from the laser is divided into two pulses. One pulse, called as the reference light pulse, is obliquely incident to the holographic plate. The other is incident to the diffuser. The light pulse from the diffuser is called as the object light pulse. The recordable time of the motion picture is limited by the lateral length of the plate. Then, we propose a technique for extending the recordable time. This technique uses double reference light pulses and dividing the plate longitudinally into two parts. Two motion pictures of the light propagation can be continuously recorded on the plate with a single-shot exposure, so that the recordable time of the motion picture can be extended. We succeeded in extending the recordable time up to twice using the proposed technique.

By using two high-speed cameras and a slightly extended visualization setup (typically based on a Toepler system) one can generate two simultaneous time-resolved records of the same flow, where these records can be obtained with different visualization methods, different spatial and different temporal resolutions. This allows one to generate visualizations that can complement each other in various ways and thus yield a considerably increased amount of information on the observed flow.

The fundamental shock wave interaction process of a wave diffraction at a sharp 90 degree corner was investigated by means of time-resolved Mach-Zehnder interferometry. The obtained results show that the process is macroscopically self-similar as has been assumed in the past but that some elements of the flow show non-selfsimilar behavior. The use of polychrome (white light) interferometry enables one to quantify the density distribution and by how much it is altered as a result of the non-self-similar behavior.

The dynamics of a converging conical shock wave were first considered theoretically as a mechanism for generating high pressures for the initiation of nuclear fusion. However, an anomaly was identified whereby the axial jet curved away from the system axis, seemingly related to occlusions of the shock tube upstream, during some experimental tests of these dynamics. This study confirms the effect of upstream occlusion on jet deflection though the mechanism is unclear as the jet may curve either toward or away from the upstream occlusion azimuth depending on the distance from the reflection point. The primary mechanisms suggested are either the wake of the upstream occlusion and the contingent momentum deficit, or else the effect of the occlusion on the shape of the conical shock wave at focus. Further numerical work is suggested as a means of resolving this.

Acoustically actuated microbubbles in microchannels can be used as a versatile tool to directly manipulate fluids and particles in Lab-on-a-Chip devices for the purpose of fast microfluidic mixing, as well as the sorting of particles or cells based on their size and other physical properties. Many experimental investigations use such bubbles in microfluidic devices. However, the physics causing the streaming field are not understood in its details yet. Existing theoretical models describe the correlation of oscillating interfaces and the streaming field that they generate. The models are either based on the oscillation of rigid objects or interfaces that oscillate with simple oscillation modes. In the experiments of this work, much more complex oscillation modes were observed for an acoustically actuated sessile and hemi-cylindrical bubble in a microchannel. The bubble is resonantly driven at a frequency of 20 kHz, and periodic shape oscillations are recorded using a stroboscopic technique. With this technique, an equivalent frame rate of more than one million frames per second can easily be achieved without using high-speed imaging equipment. In contrast to the bubble interface, the motion of the surrounding fluid is not periodic and a stroboscopic technique cannot be applied. Therefore, a 256×256 pixel, high-speed imaging system at 180.000 frames per second is used to resolve the flow field by particle tracking velocimetry. The results of this work could help to revise current models for the shape oscillation of microbubbles in order to get a deeper understanding of the underlying physics. This could help to improve microfluidic applications that use acoustically actuated microbubbles as a tool for the manipulation of flows and particles in Lab-on-a-chip-devices.

This paper presents advancement of ultra-high speed (UHS) global shutter CMOS image sensor technology exceeding 100M frames per second (fps). The development of key technologies toward the next generation UHS global shutter CMOS image sensor are overviewed, that includes high density analog memory integration, pixel-wise memory array architecture, and burst correlated double sampling (CDS) operation. By introducing the newly developed signal readout scheme with minimized pixel pulse transitions, a frame period of photo-electrons transit time is achieved. The fabricated chip prototyping a 3D stacked structure achieved 100Mfps with 80 record length and 125Mfps with 40 record length under room temperature without any cooling systems.

The Pressure-Sensitive-Paint (PSP) measurement technique is based on the dependence of the intensity or decay time of its luminescence on the pressure, brought about by oxygen quenching. PSP is usually exited by light of an appropriate wavelength (e.g. UV-light) and its pressure dependent luminescence decay time or lifetime is detected by a camera system (CCD or CMOS). Two basic types of lifetime measurement exist: the first type is a time-domain lifetime method. For this method a pulsed light is used to excite the paint and the pressure dependent time constant is determined from the decay curve of luminescence intensity. The second type is a frequency-domain fluorescence lifetime imaging (FLIM) where sinusoidal modulated light is used to excite the paint and the PSP luminescence is simultaneously detected to calculate its pressure dependent phase shift and amplitude ratio. Based on UV-LEDs a light source has been designed which provides high intensity stable and low distorted sine-modulated light of constant amplitude which is essential for the accuracy of the presented method. The new light source is used to investigate the influence of frequency on pressure sensitivity of a PSP sample to optimize the system for application in transonic wind tunnel tests.

Phase retrieval holography can suppress twin image problem of Gabor holography which causes blurred objects at a reconstructed focus position. We compared three-dimensional trajectories of spray droplets between conventional Gabor holography and developed phase retrieval holography under the high-speed imaging conditions to confirm the suppression of the twin image problem. Droplets sprayed from a nebulizer (Panasonic, EW-KA30- W) have an average diameter of 40.0 μm, mean velocity of 0.65 m/sec and Reynolds number of 0.2, respectively. Two holograms using phase retrieval holography were recorded two high-speed cameras (FASTCAM Mini UX100, Photron, frame rate: 4000 fps). It is found that phase retrieval holography has denser trajectories than Gabor holography because of suppressing the twin image problem. Additionally, number of the detected points of phase retrieval holography is almost 20 times higher than that of Gabor holography at each time step.

High intensity ultrafast near-IR laser induced filaments in air possess very precise characteristics. Each filament is controlled in spatial extent by the non-linear optical processes that are responsible for their formation. The spatial extent of the filament has a Townesian profile comprising a central high intensity region of ~ 400 μm full width, surrounded by a lower intensity peripheral field extending out several millimeters that maintains the long term propagation stability of the filament. The energy content within each filament is clamped by the threshold power needed for its establishment, for ~100 fs pulses this is ~3GW. Energy greater than this results in either the formation of additional filaments or is dispersed into the peripheral field and is diffracted out of the beam. Thus each filament carries a finite energy. Nonetheless, light filaments are an effective way of propagating over large distances extremely high power densities (< 10¹³ W/cm²), several orders of magnitude higher than the ablation threshold of nearly all materials. The level of ablation of solid surfaces is however limited by the maximum energy (few mJ) carried in each filament. In the present study we make detailed measurements of the ablation of GaAs, examining both the plasma interaction and the resulting material ablation. In addition we probe the use of additional nanosecond infrared laser light focused on the surface concurrently with the filament at intensities. We observe significantly increased filament initiated ablation when followed by lower intensity nanosecond radiation. Ultrafast radiometric studies of the plasma evolution provides new understandings of this augmented ablation process.

Mega-hertz (MHz) pulse repetition rates of intense x-ray flashes are characteristic to storage ring-based synchrotron light sources. When combined with an indirect x-ray image detection scheme composed of a fast-decay scintillator and an ultra high-speed CMOS camera, this allows multiple-frame tracking of transient processes in optically opaque objects. The temporal resolution of this so-called single-bunch imaging is ~100 ps, which is equivalent to the width of an electron bunch in the storage ring. A train of x-ray pulses can also be captured continuously (multiple-bunch imaging); the temporal resolution depends on the camera’s integration window and several hundred nanoseconds are frequently reached. At the European Synchrotron – ESRF, beamline ID19, single- and multiple-bunch x-ray imaging up to millions frames per second rates are now routinely performed within the user programme for various in situ materials characterization. In this presentation, we will describe our strategies to push the limits of time-resolved hard x-ray imaging at ESRF.

The linear-plasma flash X-ray generator consists of a high-voltage power supply, a 200-nF high-voltage condenser, a turbomolecular pump, a trigger-pulse generator, and a demountable flash X-ray tube. In the flash X-ray generator, the condenser is charged up to 50 kV by the power supply, and flash X-rays are then produced by the vacuum discharging. The X-ray tube is a demountable triode with a rod-shaped nickel (Ni) target, a zinc (Zn) reflector and a trigger electrode, and the turbomolecular pump evacuates air from the tube at a pressure of approximately 1 mPa. The Ni-target evaporation leads to the formation of weakly ionized linear plasma, consisting of Ni ions and electrons, around the target. In the plasma, K-series characteristic X-ray photons (K photons) are produced, and bremsstrahlung photons with energies beyond the Ni-K-edge energy are absorbed by the plasma and converted into Ni-K photons. Subsequently, Zn-K photons from the Zn reflector are absorbed by the linear Ni plasma and converted into Ni-K photons. Thus, intense Ni-K photons (rays) are irradiated from the plasma axial direction by K-ray amplification by spontaneous emission of radiation (KASER).

We have constructed a triple-energy (TE) X-ray photon counter with a room-temperature cadmium telluride (CdTe) detector and three sets of comparators and microcomputers to obtain three kinds of tomograms at three different X-ray energy ranges simultaneously. X-ray photons are detected using the CdTe detector, and the event pulses produced using amplifier module are sent to three comparators simultaneously to regulate three threshold energies of 15, 33 and 50 keV. Using this counter, the energy ranges are 15-33, 33-50 and 50-100 keV; the maximum energy corresponds to the tube voltage. The photon-energy resolution was 3.5% at 59.5 keV. We performed TE computed tomography (TE-CT) at a tube voltage of 100 kV. Using four lead pinholes, three tomograms were obtained simultaneously. Gadolinium-K-edge CT was carried out utilizing an energy range of 50-100 keV. At a tube voltage of 100 kV and a current of 1.60 mA, the count rate was 59 kilocounts per second (kcps).

We have constructed a dual-energy (DE) high-speed X-ray photon counter with a high-count-rate detector system and energy-range and -region selectors. The detector system consists of a cerium-doped yttrium aluminum perovskite [YAP(Ce)] crystal, a small photomultiplier tube (PMT), and an inverse amplifier for the PMT with a pulse-width extender. X-ray photons are detected using a YAP(Ce)-PMT detector, and the negative output pulses from the PMT are input to the inverse amplifier. The 400-ns-width amplifier-output pulses are sent to the pulse-width extender to measure the pulse height correctly. The event pulses from the extender are sent to the DE counter. In DE-CT, both the X-ray source and the detector module are fixed, and the object on the turntable oscillates on the translation stage. A line beam for DE-CT is formed using two lead (Pb) pinholes in front of the object. The scattering-photon count from the object is reduced using a Pb pinhole behind the object. To improve the spatial resolution, a 0.5-mm-diam Pb pinhole is attached to the YAP(Ce)- PMT detector. The tube voltage and the maximum current were 100 kV and 0.60 mA, respectively. The energy range and region for iodine- and gadolinium-K-edge CT are 35-60 and beyond 50 keV (50-100 keV), respectively. The maximum count rate of DE-CT was 80 kilocounts per second, and the exposure time for tomography was 19.6 min at a total rotation angle of 360°.

Many industrial and scientific applications, ranging from 3D imaging (such as LIDAR, surveillance, object tracking) to Time Correlated Single Photon Counting (TCSPC), require the ability to perform time-resolved detection of weak light signals, down to single-photon level. Single-Photon Avalanche Diodes are solid-state detectors capable of single-photon sensitivity in the visible and near-infrared wavelength regions and compatible with standard silicon processes. This demand driven the development of low cost, large size CMOS SPAD imagers. In this work we present the design and characterization of a time-gated 32x32 SPAD image sensor fabricated in a 0.16 μm BCD (Bipolar-CMOS-DMOS) technology. The sensor is based on an innovative 16x16 macropixel structure, each composed by four SPADs with independent sensing front-end and event counters, plus a shared Timeto- Digital Converter (TDC). This approach enables higher fill-factor (9.6% with a pixel pitch of 100 μm) by sharing the costly (in terms of area) TDC resource, as well as reduced power dissipation. The imager provides simultaneous photon-timing and photon-counting data and features a 12 bit, 75 ps bin width TDC, which can perform one conversion per each gate window, with up to 62 windows per data readout frame. Two main operation modes are available: a single-photon mode, where an arbitration circuit within the macropixel is used to share the TDC among the 4 SPADs, but with no loss of X-Y resolution (i.e. keeping information about the triggered SPAD); and a two-photon-coincidence mode, where the TDC performs a conversion only if two SPADs of the macropixel are triggered within a preset coincidence window. Lastly, the sensor features multiple readout modes, with varying amount of output data, in order to fit different end-user applications. The imager is capable of 100 kfps (frames per second) in full readout mode, and up to 400 kfps in a reduced data set mode.

In recent years, high-speed videogrammetry has been used to monitor the three-dimension behavior of large vibrating structures. Traditionally, this has been accomplished by transferring image sequences, captured by several cameras, to a central computer after each test has been conducted. Only then have the images been postprocessed and the required kinematic data extracted. This process is slow and inefficient because a large amount of data (image sequences) must be transferred to the host before the data analysis can begin. In order to address this problem, we have developed a novel system that adopts a distributed data processing strategy. The system which combining the processing power built into each of the individual cameras and the processing power of a central computer, uses a wired local area network. the communication between the nodes and the host is achieved using the TCP/IP protocol and a custom application layer. In this way, the processing power of the entire system is more fully utilized and the overall performance of the video processing system is improved. We describe how we have employed two cameras, operating simultaneously, to test the proposed concept. The experimental results from a series of tests showed that the average time required to perform the necessary image processing was reduced 58.7% by using the distributed processing system instead of a traditionally configured system.

A high-speed schlieren system in a Toepler-Z configuration is used for flow visualization for a transonic flow field around a supercritical airfoil. Schlieren pictures have been recorded mainly at a framerate of 16 kfps. From the set of images streak records can be generated. These streak records offer further possibilities of flow analysis like the determination of shock or pressure wave frequencies. The schlieren setup has been extended to a quantitative schlieren setup using a weak plano-convex lens in the setup as a “calibration lens”. This lens allows a quantitative relationship between the image pixel intensity and the refraction angle. The quantitative schlieren technique offers the possibility to determine the density gradient as well as the flow density far away from the airfoil.

In this paper, we report on the development and manufacture of a dual-slit electron-optical dissector based on the PIF-01 streak image tube with a picosecond time resolution operating in the crossed-sweep mode. The dissector is designed to work on synchrotron radiation sources and electron-positron colliders, when it is necessary to record simultaneously the temporal profiles of electron and positron bunches filling from two to several hundred neighboring separatrices of an accelerator ring. In order to obtain the crossed-sweep mode, high-frequency (HF) sinusoidal voltages with multiple frequencies are fed to two pairs of deflecting plates of the tube, located perpendicular to each other. This separation of pulses will allow separate acquisition of the bunch profiles from neighboring separatrices of an accelerator, which are superimposed on each other in the absence of the crossed sweep. During the tests of the device which have been conducted on a laser system, two trains of light pulses, ”shifted” in time with respect to each other, were recorded with a time resolution of 6 ± 0.5 ps. Improvement of a single slit dissector was also done using the MASIM software. As a result, the temporal resolution of the modernized dissector measured on a femtosecond Ti:sapphire laser was about 1.5 ps. The dissector was tested on the MLS (Berlin, Germany) accelerator. Using both the HAMAMATSU C10910 streak camera and the dissector, comparative measurements of the longitudinal bunch length were performed.

A simulation study was performed to confirm the technical feasibility of a magnetic lens consisting of a multi-hole permanent magnet to focus a two-dimensional electron beam array. The permanent magnetic lens has a simple structure, and its interference with the deflection electric field is low. In contrast to expectations, the magnetic field intensity is substantially flat in the central region of the multi-hole permanent magnet with a diameter of 6 mm. Only a slight nonuniformity is observed in the radial direction in this region. Although the outer edge of the magnet strongly distorts the intensity distribution in the peripheral region, the area of the influence is only 1 mm wide. The beam convergence rate in the uniform area is approximately 1/10 for a simple model, and 1/40 for an improved model. This technology is applicable to ultra-high-speed imaging with a temporal resolution of the order of picoseconds. The number of recorded signals is expected to be M2 with 1/M convergence with the deflection in two directions. Therefore, a speed-up of 1600 times is achievable.

For high-speed impact incidents associated with the generation of flashes, dust or smoke, optical imaging often is not feasible. In these cases, X-ray flash imaging is one of the established tools for the analysis. However, Xray flash imaging is often limited to few (usually max. 8) images from one or equally few directions. This severely limits the spatial resolution and capacity to derive 3D information about the observed process as well as temporal resolution to capture the dynamics of the process. Usually, several X-ray images are taken at one point in time from different perspectives to create a 3D-reconstruction from few projections (High-Speed X-ray Computed Tomography, HSCT), or taken at several points in time from the same perspective to allow the evaluation of the dynamics. For some applications, this is not sufficient. In this talk, we demonstrate how these limitations can be overcome, by presenting an exemplary approach to investigate impact processes with X-ray flash imaging. By the use of a priori information about the process, it is possible to gain the flight trajectory including dynamic information (velocity) for each observed fragment from one single experiment. This is possible by acquiring several X-ray flash images from different viewing directions at different points in time. By using a data fusion scoring algorithm, possible dynamic solutions for each fragment are found and can be evaluated to characterize the process. Using this method, fragments on the size of < 1 cm can be localized to trajectories with a statistical error of ± 5 mm and a statistical relative velocity error of < 5%. In an outlook, we evaluate how this approach can be transferred to other measurement methods.

Ultra-high speed photoelectric photographic system is one of the important methods to study the image parameters of ultrafast physical process. This paper proposes a method of combining multi-group prism optical splitter, super shutter selection image intensifier with adjustable delay and CCD picture acquisition. The proposed method solves the problem of the image cutting in the small aperture backlight illumination experiment using the pyramid-type photoelectric camera. Several ultra-high speed photographic systems are developed, which can be used for the shadow photography, and realize ultra high speed photoelectric photographic system with 43 mm-1 spatial resolution, 2x108 images/s speed, and the capability of capturing 8 images continuously (Fig. 1). In order to adapt to the strong electromagnetic interference test environment, the photographic system adopts all optical fiber communication, signal interpretation and locking, unit modularization and other technical schemes to avoid the loss of signal in the image transmission and the system mistriggering problems. The developed camera has good application to such dynamic experiments as plasma physics and the interaction between laser and substance, and satisfactory results have been achieved.

For several decades, ceramic materials have been widely used in bilayered protective configurations. However, the impact loading produces dynamic tensile stresses that spread out the ceramic tile leading to an intense fragmentation made of short oriented cracks. To improve the design of such configurations the fragmentation process needs to be better understood. The edge-on impact (EOI) testing method constitutes one of the most used experimental techniques to investigate the fragmentation process in brittle materials at high-strain-rates. A cylindrical projectile hits the edge of a target leading to a multiple fragmentation. In classical EOI experiments, an ultra-high-speed camera is used to visualize the fragmentation process on the lateral surface. However, the fragmentation pattern in the bulk of the target can only be analysed post-mortem. In the present work, in addition to this classical optical inspection method, EOI experiments have been conducted in the European Synchrotron Radiation Facility with the means of ultra-high-speed imaging, i. e., X-ray radioscopy using the 16-bunch operation mode. The target, 60 x 30 x 6 mm³, was placed in the intense X-ray beam (beam energy about 30 keV) providing an observation field of 12.8 mm in width and 8 mm in height, and impacted with a projectile velocity of 144 m/s. A Shimadzu HPV-X2 camera lens-coupled to a fast scintillator was used to visualise the fragmentation process through the thickness with an interframe time set to 1065 ns. This fragmentation pattern is compared to pictures of the lateral surface obtained with an ultra-high-speed camera or post-mortem analysis.

Ratio temperature method can avoid difficulties of correction of target emissivity in temperature measurement, which enables simultaneous measurement of temperature distribution of targets having different emissivity, for example, melting and solidifying process of metal. We have studied ratio temperature method using two wavelength images captured by either a color high-speed camera or a twoimage- sensor camera. The minimum temperature limit which can be measured with a color high-speed camera is about 900 degrees centigrade, because the camera can only capture visible wavelengths. The technique for measuring temperature distribution less than 900 degrees centigrade at high-speed using single sensor camera hasn't been established. In late years, a multi-spectrum camera become commercially available, with which multiple wavelengths images can be captured simultaneously by utilizing pixel-bypixel band pass filters. If we apply this technique to sensors with high-speed capability, and with near infrared wavelength bandpass filters, temperature measurement down to 500 degrees centigrade would be possible. In this study, we report the result of temperature distribution measurements by ratio temperature method using a commercially available multi-spectrum camera which captures four wavelengths images in near infrared.