kHz Frame Rate Research Articles

Fourier domain optical coherence tomography using optical demultiplexers imaging at 60,000,000 lines/s

We describe high-speed Fourier domain optical coherence tomography (OCT) using optical demultiplexers (ODs) for spectral dispersion. The OD enables separation of a narrow spectral band of 14 GHz (0.11 nm) from a broadband incident light at 256 different frequencies in 25.0 GHz intervals centered at 192.2 THz (1559.8 nm). OCT imaging of 60,000,000 axial scans per second was achieved through parallel signal acquisition using 256 balanced photoreceivers to simultaneously detect all the output signals from the ODs in a Fourier domain OCT system. OCT imaging at a 16 kHz frame rate, 1100 A-lines per frame, 3 mm depth range, and 23 microm resolution was demonstrated using a resonant scanner for lateral scanning.

High-speed wave-mixing laser Doppler imaging in vivo

An interferometric method for parallel optical spectroscopy in the kilohertz range is reported, as well as its experimental validation in the context of high-speed laser Doppler imaging in vivo. The interferometric approach enables imaging in the low light conditions of a 2 kHz frame rate recording with a complementary metal-oxide semiconductor camera. Observation of mice craniums with near-infrared (lambda=785 nm) laser light in reflection configuration is reported. Doppler spectral images allegedly sensitive to blood flow are sequentially measured at several optical frequency detunings, to shift the spectral range of analysis in the radio-frequency spectrum.

Process Development and Control of Laser Drilled and Shaped Holes in Turbine Components

Cooling holes (100 holes/cm2, diameter 0.2 0.6 mm, inclination angle up to 60°) are drilled by pulsed laser radiation (Nd:YAG, 1064 nm, 0.1 1 ms) in X5CrNi18 10 and CMSX-4 multi layer systems with BC (MCrAlY bond coating) and TBC (ZrO2 thermal barrier coating). There are two different options to drill and shape the holes: The first layout is a one-step procedure with a simultaneous five-axis trepanning movement of the laser beam. The second layout is a two-step procedure with percussion drilling or trepanning a through hole and structuring a fan by short pulse ablation in the second step. The thermal radiation from the drilling process is detected by an in-situ CPC (coaxial process control) during percussion drilling using high speed photography (50 kHz frame rate) in order to determine the break through and prevent back wall damages by drilling hollow structures, e.g. turbine blades.

Laboratory and in-beam tests of a novel real-time beam monitor for hadrontherapy

Real time monitoring of hadrontherapy beam intensity and profile is a critical issue for the optimization of dose delivery to carcinogenic tissue, patient safety and operation of the accelerator complex. For this purpose an innovative beam monitor, secondary electron emission for low interception monitoring (SLIM) is being developed in the framework of the EC-funded silicon ultra-fast cameras for electrons and gamma sources in medical application (SUCIMA) project. The detector system is based on the secondary emission of electrons by a nonperturbative, sub-micron thick Al foil placed directly in the extracted beam path. The secondary electrons, accelerated by an electrostatic focusing system, are detected by a monolithic silicon position-sensitive sensor, which provides the beam intensity and its position with a precision of 1 mm at a 10 kHz frame rate. The results of the laboratory tests of the first system prototype with thermoionic electrons emitted from a hot Tungsten wire are presented together with the measurements performed on a low intensity hadron beam at the Cyclotron of the Joint Research Centre in Ispra.

Optically sensitive Medipix2 detector for adaptive optics wavefront sensing

A new hybrid optical detector is described that has many of the attributes desired for the next generation adaptive optics (AO) wavefront sensors. The detector consists of a proximity focused microchannel plate (MCP) read out by multi-pixel application specific integrated circuit (ASIC) chips developed at CERN (“Medipix2”) with individual pixels that amplify, discriminate and count input events. The detector has 256×256 pixels, zero readout noise (photon counting), can be read out at 1 kHz frame rates and is abutable on 3 sides. The Medipix2 readout chips can be electronically shuttered down to a temporal window of a few microseconds with an accuracy of 10 ns. When used in a Shack–Hartmann style wavefront sensor, a detector with 4 Medipix chips should be able to centroid approximately 5000 spots using 7×7 pixel sub-apertures resulting in very linear, off-null error correction terms. The quantum efficiency depends on the optical photocathode chosen for the bandpass of interest.

Optical observations of acoustical radiation force effects on individual air bubbles

Previous studies dealing with contrast agent microbubbles have demonstrated that ultrasound (US) can significantly influence the movement of microbubbles. In this paper, we investigated the influence of the acoustic radiation force on individual air bubbles using high-speed photography. We emphasize the effects of the US parameters (pulse length, acoustic pressure) on different bubble patterns and their consequences on the translational motion of the bubbles. A stream of uniform air bubbles with diameter ranging from 35 microm to 79 microm was generated and insonified with a single US pulse emitted at a frequency of 130 kHz. The bubble sizes have been chosen to be above, below, and at resonance. The peak acoustic pressures used in these experiments ranged from 40 kPa to 120 kPa. The axial displacements of the bubbles produced by the action of the US pulse were optically recorded using a high-speed camera at 1 kHz frame rate. The experimental results were compared to a simplified force balance theoretical model, including the action of the primary radiation force and the fluid drag force. Although the model is quite simple and does not take into account phenomena like bubble shape oscillations and added mass, the experimental findings agree with the predictions. The measured axial displacement increases quasilinearly with the burst length and the transmitted acoustic pressure. The axial displacement varies with the size and the density of the air bubbles, reaching a maximum at the resonance size of 48 microm. The predicted displacement values differ by 15% from the measured data, except for resonant bubbles for which the displacement was overestimated by about 40%. This study demonstrates that even a single US pulse produces radiation forces that are strong enough to affect the bubble position.

New results on DEPFET pixel detectors for radiation imaging and high energy particle detection

DEPFET pixel detectors are unique devices in terms of energy and spatial resolution because very low noise operation can be obtained (ENC=2.2e/sup -/ at room temperature) by implementing the amplifying transistor in the pixel cell itself. Full DEPFET pixel matrices have been built and operated for autoradiographical imaging with imaging resolutions of 4.3/spl plusmn/0.8 /spl mu/m at 22 keV. For applications in low energy X-ray astronomy the high energy resolution of DEPFET detectors is attractive. For particle physics, DEPFET pixels are interesting as low mass detectors with high spatial resolution. For a linear collider detector the readout must be very fast. New readout chips have been designed and produced for the development of a DEPFET module for a pixel detector at the proposed TESLA collider, containing 520/spl times/4000 pixels, with 50 MHz line rate and 25 kHz frame rate. The circuitry contains current memory cells and current hit scanners for fast pedestal subtraction and sparsified readout. The imaging performance of DEPFET devices as well as present achievements toward a DEPFET vertex detector for a linear collider are presented.

Two-Dimensional Silicon/Ferroelectric Liquid Crystal Spatial Light Modulators

AbstractSpatial light modulator (SLM) technology based on commodity silicon fabrication processes and employing a thin, ferroelectric liquid crystal light modulating layer at the chip's surface, has advanced to the point of producing high-performance, practically useful devices. Electrically addressed display devices with 256 × 256 resolution, 100: 1 contrast, and 10 kHz frame rate, as well as optically addressed, “smart” SLMs that perform spatio-temporal filtering on images, have resulted in the course of the author's involvement with Displaytech, Inc.The silicon technology infrastructure is a juggernaut that produces regular and significant advances in capability. An optoelectronics technology based on foundry silicon can exploit these advances directly and realize rapid improvements. The gains in the density, speed, and optical performance of the Si/FLC devices presented here, illustrate this perspective.The favorable speed-power performance of these devices is due to an excellent match in the “terminal characteristics” of FLC materials with those of fine-line MOSFETs. The impact of these characteristics on overall device performance is discussed in some depth.