Multichannel digital phase sensitive detection using a field programmable gate array development platform

This paper describes the development and performance of digital phase sensitive detectors (PSDs) based on a field programmable gate array (FPGA) logic device. A FPGA development system combined with a custom analog data acquisition board provides a powerful platform for the development of digital signal processing systems. Conventional performance metrics for digital PSDs are determined by the analog front-end devices and do not represent improvements to the PSD itself. FPGAs offer a scalable platform on which digital PSDs can be implemented with enhanced capabilities including simultaneous demodulation of multiple independent analog signals at multiple frequencies with arbitrary demodulation functions. Circuits for providing dynamic frequency tracking and ultrafine (<0.001 degrees ) phase resolution are presented.     

FPGA在吊丝微重力系统控制器中的应用

为达到吊丝微重力系统的性能要求,该文基于Xilinx公司Virtex系列芯片,采用VHDL硬件描述语言实现了遗传算法,并将其用于PID参数的优化.该方法集成了软件算法和硬件电路的优势,相比基于PC的遗传算法,在提高系统反应速度,抑制超调方面有所改善.     

Design of a field programmable gate array based test launch and control system for hybrid vehicle

In order to satisfy the throttling and multiple restart characteristics of the hybrid rocket engine and guarantee the controllability and security of hybrid rocket, the test launch and control system for hybrid vehicle needs to achieve ground power control, serial communication with the flight control computer and the telemetry system, onboard thermal battery activation, battery voltage acquisition, power conversion, pressure monitoring, valve control, booster ignition, power-off and remote pressure relief in emergency. Considering the complexity of the test launch and control system for hybrid system and the advantages of Field Programmable Gate Array (FPGA), such as, a large number of I/O ports, ability to efficiently implement large-scale systems and programmability, a FPGA based test launch and control system for a type of hybrid vehicle was designed. Many conducted ground and flight experiments have proved that the system has superior performance in integration, universalization, miniaturization, automation and can perfectly meet the needs of the hybrid vehicle.     

基于FPGA的微光图像伪彩色处理系统的实现

本文研究伪彩色增强算法,并设计实现了基于FPGA的图像伪彩色增强处理系统,这个系统适用于实现多种伪彩色算法或其它各种增强算法硬件电路,本文主要采用了密度分层算法,根据不同灰度的级别来化分各个颜色带,电路成功的实现了各种场合图像伪彩色图像增强。     

Design of a field programmable gate array-based platform for real-time de-noising of optical imaging signals using wavelet transforms

In this study, the design of a low-cost, field programmable gate array (FPGA)-based digital hardware platform that implements wavelet transform algorithms for real-time signal de-noising of optical imaging signals is presented. The proposed digital hardware de-noising platform can achieve a throughput of 25 Msamples per second, with a latency from input to output of 1.5 μs. The system fits on a 10K20, one of the smaller field programmable gate arrays from the Altera Flex 10K family, and represents a low-cost approach to signal de-noising. Preliminary experimental results clearly indicate the potential of the presented FPGA-based digital platform for real-time de-noising of signals utilized for the detection and imaging of surface defects and discontinuities.     

New field programmable gate array-based image-oriented acquisition and real-time processing applied to plasma facing component thermal monitoring

During operation of present fusion devices, the plasma facing components (PFCs) are exposed to high heat fluxes. Understanding and preventing overheating of these components during long pulse discharges is a crucial safety issue for future devices like ITER. Infrared digital cameras interfaced with complex optical systems have become a routine diagnostic to measure surface temperatures in many magnetic fusion devices. Due to the complexity of the observed scenes and the large amount of data produced, the use of high computational performance hardware for real-time image processing is then mandatory to avoid PFC damages. At Tore Supra, we have recently made a major upgrade of our real-time infrared image acquisition and processing board by the use of a new field programmable gate array (FPGA) optimized for image processing. This paper describes the new possibilities offered by this board in terms of image calibration and image interpretation (abnormal thermal events detection) compared to the previous system.     

A compact digital time differential perturbed angular correlation-spectrometer using field programmable gate arrays and various timestamp algorithms

A user-friendly fully digital time differential perturbed angular correlation (TDPAC)-spectrometer with six detectors and fast digitizers using field programmable gate arrays (FPGA) is described and performance data are given. The new spectrometer has an online data analysis feature, a compact size, and a time resolution such as conventional analog spectrometers. Its calculation intensive part was implemented inside the digitizer. This gives the possibility to change parameters (energy windows, constant fraction trigger delay) and see their influence immediately in the γ-γ correlation diagrams. Tests were performed which showed that the time resolution using a (60)Co source with energy window set at 1.17 MeV and 1.33 MeV is 265 ps with LaBr(3)(Ce) scintillators and 254 ps with BaF(2) scintillators. A true constant fraction algorithm turned out to be slightly better than the constant fraction of amplitude method. The spectrometer performance was tested with a TDPAC measurement using a (44)Ti in rutile source and a positron lifetime measurement using (22)Na. The maximum possible data rate of the spectrometer is 1.1 × 10(6) γ quanta per detector and second.     

An optical sectioning programmable array microscope implemented with a digital micromirror device

The defining feature of a programmable array microscope (PAM) is the presence of a spatial light modulator in the image plane. A spatial light modulator used singly or as a matched pair for both illumination and detection can be used to generate an optical section. Under most conditions, the basic optical properties of an optically sectioning PAM are similar to those of rotating Nipkow discs. The method of pattern generation, however, is fundamentally different and allows arbitrary illumination patterns to be generated under programmable control, and sectioning strategies to be changed rapidly in response to specific experimental conditions. We report the features of a PAM incorporating a digital micromirror device, including the axial sectioning response to fluorescent thin films and the imaging of biological specimens. Three axial sectioning strategies were compared: line scans, dot lattice scans and pseudo-random sequence scans. The three strategies varied widely in light throughput, sectioning strength and robustness when used on real biological samples. The axial response to thin fluorescent films demonstrated a consistent decrease in the full width at half maximum (FWHM), accompanied by an increase in offset, as the unit cells defining the patterns grew smaller. Experimental axial response curves represent the sum of the response from a given point of illumination and cross-talk from neighbouring points. Cross-talk is minimized in the plane of best focus and when measured together with the single point response produces a decrease in FWHM. In patterns having constant throughput, there appears to be tradeoff between the FWHM and the size of the offset. The PAM was compared to a confocal laser scanning microscope using biological samples. The PAM demonstrated higher signal levels and dynamic range despite a shorter acquisition time. It also revealed more structures in x - z sections and less intensity drop-off with scanning depth.     

Three-dimensional spectral imaging by Hadamard transform spectroscopy in a programmable array microscope

We report the acquisition and deconvolution of three-dimensional spectrally resolved images in a programmable array microscope implementing a Hadamard transform fluorescence spectroscopy system with adjustable spectral resolution. A stack of 16 two-dimensional spectral images was collected at 400 nm intervals along the optical axis. The specimen consisted of a polytene chromosome spread from Drosophila melanogaster doubly labelled for the Polyhomeotic protein by indirect immunofluorescence labelling with Alexa594 and for DNA with YOYO-1. The resulting four-dimensional data set consisted of the xyz spatial dimensions (898 × 255 × 16) with a 26-point spectrum at each spatial location. The total exposure time to the sample was 34 min. The system requires the acquisition of multiple images, and thus works best with fluorophores that are resistant to photobleaching. Image deconvolution reduced the amount of out-of-focus blur by up to a factor of 8, resulting in a dramatic improvement in the visualization of the chromosome backbone and localization of the specific Polyhomeotic domains.     

Note: design of a novel rotating magnetic field device

A novel device to produce a rotating magnetic field was designed, constructed, and tested. The system consists of a Helmholtz coil pair which is mechanically coupled to a dc electric motor whose angular velocity is controlled. The coil pair generates a uniform magnetic field; the whole system is rotated maintaining the coils energized using brushes. The magnetic field strength is uniform (≈5.8 mT) for a workspace of about 100 mm along the rotation axis. The system remains free of undesirable high amplitude mechanical vibrations for rotation frequencies below 10 Hz. We verified the performance of the apparatus by conducting experiments with magnetic swimmers.     

Note: an underwater multi-channel plasma array for water sterilization

A simple yet effective method to generate multi-channel plasma array in water is presented in this paper. Thin circular metal disks sandwiched between dielectric layers were used, allowing the production of large-volume underwater plasma array with higher stability. The system can be further scaled up by stacking multiple metal disks, making it suitable for large-scale industrial water treatment. Generation of UV and reactive species was identified by optical emission spectroscopy. Sterilization experiments were performed. Results show that the device was effective in deactivating E. coli in water over a wide range of initial concentrations ranging from 10(4) to 10(8) CFU/ml.     

Note: Detection of a single cobalt microparticle with a microfabricated atomic magnetometer

We present magnetic detection of a single, 2 μm diameter cobalt microparticle using an atomic magnetometer based on a microfabricated vapor cell. These results represent an improvement by a factor of 10(5) in terms of the detected magnetic moment over previous work using atomic magnetometers to detect magnetic microparticles. The improved sensitivity is due largely to the use of small vapor cells. In an optimized setup, we predict detection limits of 0.17 μm(3).     

Note: Controllable positioning of a single particle in between nanogap electrodes

We have developed a relatively simple procedure capable to position a single nanoparticle in between nanogap electrodes for nanoelectronic applications. The well-defined particle positioning was achieved via pinning the edge of a dispersion droplet over the nanogap. Pinning time, substrate temperature, and its displacement velocity are excellent control parameters.     

Note: Design and construction of a simple and reliable printed circuit board-substrate Bradbury-Nielsen gate for ion mobility spectrometry

A less laborious, structure-simple, and performance-reliable printed circuit board (PCB) based Bradbury-Nielsen gate for high-resolution ion mobility spectrometry was introduced and investigated. The gate substrate was manufactured using a PCB etching process with small holes (Φ 0.1 mm) drilled along the gold-plated copper lines. Two interdigitated sets of rigid stainless steel spring wire (Φ 0.1 mm) that stands high temperature and guarantees performance stability were threaded through the holes. Our homebuilt ion mobility spectrometer mounted with the gate gave results of about 40 for resolution while keeping a signal intensity of over 0.5 nano-amperes.     

Fluorescence recovery after photobleaching and photoconversion in multiple arbitrary regions of interest using a programmable array microscope

Photomanipulation (photobleaching, photoactivation, or photoconversion) is an essential tool in fluorescence microscopy. Fluorescence recovery after photobleaching (FRAP) is commonly used for the determination of lateral diffusion constants of membrane proteins, and can be conveniently implemented in confocal laser scanning microscopy (CLSM). Such determinations provide important information on molecular dynamics in live cells. However, the CLSM platform is inherently limited for FRAP because of its inflexible raster (spot) scanning format. We have implemented FRAP and photoactivation protocols using structured illumination and detection in a programmable array microscope (PAM). The patterns are arbitrary in number and shape, dynamic and adjustable to and by the sample characteristics. We have used multispot PAM–FRAP to measure the lateral diffusion of the erbB3 (HER3) receptor tyrosine kinase labeled by fusion with mCitrine on untreated cells and after treatment with reagents that perturb the cytoskeleton or plasma membrane or activate coexpressed erbB1 (HER1, the EGF receptor EGFR). We also show the versatility of the PAM for photoactivation in arbitrary regions of interest, in cells expressing erbB3 fused with the photoconvertible fluorescent protein dronpa. dronpa. Microsc. Res. Tech., 2009. © 2009 Wiley-Liss, Inc.     

A dual path programmable array microscope (PAM): simultaneous acquisition of conjugate and non-conjugate images

A programmable array microscope (PAM) incorporates a spatial light modulator (SLM) placed in the primary image plane of a widefield microscope, where it is used to define patterns of illumination and/or detection. We describe the characteristics of a special type of PAM collecting two images simultaneously. The conjugate image (I_c) is formed by light originating from the object plane and returning along the optical path of the illumination light. The non‐conjugate image (I_nc) receives light from only those regions of the SLM that are not used for illuminating the sample. The dual‐signal PAM provides much more time‐efficient excitation than the confocal laser scanning microscope (CLSM) and greater utilization of the available emission light. It has superior noise characteristics in comparison to single‐sided instruments. The axial responses of the system under a variety of conditions were measured and the behaviour of the novel I_nc image characterized. As in systems in which only I_c images are collected (Nipkow‐disc microscopes, and previously characterized PAMs), the axial response to thin fluorescent films showed a sharpening of the axial response as the unit cell of the repetitive patterns decreased in size. The dual‐signal PAM can be adapted to a wide range of data analysis and collection strategies. We investigated systematically the effects of patterns and unit cell dimensions on the axial response. Sufficiently sparse patterns lead to an I_c image formed by the superposition of the many parallel beams, each of which is equivalent to the single scanning spot of a CLSM. The sectioning capabilities of the system, as given by its axial responses, were similar for a given scan pattern and for processed pseudorandom sequence (PRS) scans with the same size of the unit cell. For the PRS scans, optical sectioning was achieved by a subtraction of an I_nc image or, alternatively, a scaled widefield image from the I_c image. Based on the comparative noise levels of the two methods, the non‐conjugate subtraction was significantly superior. A point spread function for I_c and I_nc was simulated and properties of the optical transfer functions (OTFs) were compared. Simulations of the OTF in non‐conjugate imaging did not suffer from the missing cone problem, enabling a high quality deconvolution of the non‐conjugate side alone. We also investigated the properties of images obtained by subjecting the I_c and I_nc data to a combined maximum likelihood deconvolution.     

Note: A time-resolved Kerr rotation system with a rotatable in-plane magnetic field

A time-resolved Kerr rotation system with a rotatable in-plane magnetic field has been constructed to study anisotropic spin relaxation of electrons in semiconductors. A permanent magnet magic ring is placed on top of a motor-driven rotation stage (RS) to create the rotatable in-plane magnetic field. The RS is placed on a second translation stage to vary the local magnetic field around a sample. The in-plane magnetic field in such a system varies from 0.05 to 0.95 T, with full-round 360° rotatablity, thus offering a convenient and low-cost way to study the anisotropy of spin dynamics in semiconductors. Its performance was demonstrated via measurement of the anisotropy of the spin dephasing time (SDT) of electrons in a two-dimensional electron system embedded in a GaAs/Al(0.35)Ga(0.65)As heterostructure. The SDT with B∥[110] was observed to be 10% larger than that with B∥[110], consistent with the results of others, which was measured via rotating sample.     

Measuring chloride in serum using single programmable system on chip (PSoC)

PSoC devices are dynamically reconfigurable, versatile programming, low-power consumption and multiple interfacing, which motivates the design of portable and inexpensive instruments. The chloride analyzer is built around a cypress CY8C27443 PSoC with its analog and digital blocks, which is typically an embedded system, and it is configured for the measurement of chloride in serum. The principle of chloride measurement is based on colorimetry with LED as illuminating source and photodiode GASPG1104 as a light sensor. The run to run precision of the implemented system is determined by analysing human control serum Accutrol™ Normal (Sigma) and the chloride concentration is found to be 104 ± 4 mmol/l (mean ± SD, n = 5), which is close to the certified value. This system has been used successfully for the routine assay of bio-medical samples, with the results in good agreement with values obtained by the commercial clinical analyzer at 95% of confidence level.     

Note: Laser ablation technique for electrically contacting a buried implant layer in single crystal diamond

The creation of thin, buried, and electrically conducting layers within an otherwise insulating diamond by annealed ion implantation damage is well known. Establishing facile electrical contact to the shallow buried layer has been an unmet challenge. We demonstrate a new method, based on laser micro-machining (laser ablation), to make reliable electrical contact to a buried implant layer in diamond. Comparison is made to focused ion beam milling.     

Note: binding energy scale calibration of electron spectrometers for photoelectron spectroscopy using a single sample

The feasibility of calibrating the binding energy scale for photoelectron spectroscopy using a single sample without sputter cleaning was investigated. By measuring the Fermi level of a Au film with both monochromatic Al Kα (hν = 1486.7 eV) and He Iα (hν = 21.22 eV), the binding energy scale was simply and accurately calibrated. This method is found to yield binding energy values for the Cu 2p(3/2), Ag 3d(5/2), and Au 4f(7/2) peaks that agree with the standard tabulated values defined in International Organization for Standardization 15472 to within ±0.02 eV.