微光探测装置自成暗室设计开发

针对现有微光检测系统体积大、避光效果差等不足,对微光探测装置进行全新设计。采用反应杯与光探测头自成暗室,减少暗室进出机构,提高避光效果;采用斩波法扣除本底计数,从而消除背景光引起的测量误差。性能测试结果显示:该微光探测装置的光子本底计数小于等于200光子/s,测光上限平均值达到1.1×107光子/s,变异系数(CV)小于等于3%,达到目前现有的微光检测系统的技术指标要求,可用于化学发光免疫分析仪等需要进行微光信号检测的精密仪器开发,对基于微光探测技术的仪器行业的发展具有重要意义。     

微脉冲激光雷达中的光子计数死区时间瞬态效应

建立了光子计数器的模型,对光子计数器的死区时间效应进行了理论分析和实际测量,并提出了校正光子计数效应对微脉冲雷达信号影响的方法。利用马尔科夫链对微脉冲雷达的探测过程进行理论分析,并利用MATLAB对死区时间对光子计数产生的影响进行了计算和分析,描述了计数死区对探测结果产生的瞬态形态变化。在此基础上,搭建了微脉冲激光雷达光子计数的测量平台,实验验证了死区时间对于光子计数采集的影响。最后,测量了不同光强下死区时间对探测结果的抑制情况,给出了微脉冲激光雷达信号的校正方法。基于提出的方法对真实微脉冲激光雷达信号进行了校正实验。实验结果表明:在峰值功率为100mW的405nm激光照射下,光子计数在采集频率100 MHz时的散射光计数效应减少了50%。文中的方法较好地解释了小尺寸目标的探测信号形态,实现了对光子计数探测结果的校正。     

用于真空紫外波段内弱光光谱测量的光子计数器

本文介绍了用于真空紫外波段内弱光光谱测量的光子计数系统,概述了它的设计原则,给出了有关指标的定量关系和实用线路。该系统具有从150A到1300A的波长覆盖范围和大于10⁶的动态范围,可用来测量小到10^-18W的弱光辐射。在真空紫外区已用该系统测量到了小于10个计数/s的弱光谱线。     

Experimental setup for low-energy laser-based angle resolved photoemission spectroscopy

A laser-based angle resolved photoemission (ARPES) system utilizing 6 eV photons from the fourth harmonic of a mode-locked Ti:sapphire oscillator is described. This light source greatly increases the momentum resolution and photoelectron count rate, while reducing extrinsic background and surface sensitivity relative to higher energy light sources. In this review, the optical system is described, and special experimental considerations for low-energy ARPES are discussed. The calibration of the hemispherical electron analyzer for good low-energy angle-mode performance is also described. Finally, data from the heavily studied high T(c) superconductor Bi(2)Sr(2)CaCu(2)O(8+delta) (Bi2212) is compared to the results from higher photon energies.     

压缩传感用于极弱光计数成像

为解决灵敏度达到单光子水平的面阵探测器件其单位像素上灵敏度有限和测量数多等问题,研制了具有极高灵敏度的成像系统来实现欠采样的极弱光成像探测。该成像系统基于光子计数成像技术和压缩感知理论,利用数字微镜器件(DMD)完成随机空间光调制,通过单光子点探测器收集光子,以计数形式记录下光强值。然后,利用算法重建出极弱光照明下的图像。文中设计了相关实验,研究了测量数、光强极弱程度和测量时间对成像质量的影响。最后,引入了图像质量评价标准和系统信噪比,分析对比了实验数据。结果表明,当测量数高于信号总维度的19.5%时,系统能完美成像,信噪比可低至2.843 8dB,DMD单位像素上的平均光子数可低于1.106count/s,成像的关键在于信号的波动大于噪声的波动。该成像系统基本满足了极弱光成像探测在光强、灵敏度和采样数等方面的要求。     

A microprocessor-controlled photon counter for pulsed optically detected magnetic resonance

In pulsed optically detected magnetic resonance (ODMR) spectroscopy, a lock-in amplifier is used to monitor the signal which is phase-matched to the duty cycle of an applied sequence of pulses. However, since the desired signals reside atop a much larger amplitude-modulated signal, lock-in amplification methods are difficult to use. Commerically available photon counters are of limited use, because the pulsed ODMR method requires sequential counting over several time intervals, often with minimum time delay between the intervals. The multiaccumulator photon counter described here is capable of such sequential counting over as many as four intervals. The microprocessor which controls the counter algebraically manipulates the photon counts during each of the duty cycles. The result is an inexpensive yet versatile photon counter which is suited for pulsed ODMR and other applications in which sequential counting is necessary.     

Using simultaneous three colour X-ray mapping and digital-scan-stop for rapid elemental characterization of coal combustion by-products

A system is described for rapid, simultaneous three colour elemental mapping with a scanning electron microscope (SEM) and an energy dispersive X-ray analyser. The technique, which uses a SEM scanning at TV rate, minimizes the disadvantages of long scan times such as inefficient use of linear amplifier and observable dead-time shadowing. The system also employs a digital scan-stop assembly utilizing a light pen to rapidly and reproducibly direct the beam to an object of choice for spot-mode analysis. Application of the system to analysis of fine particulates with emphasis on fly ash derived from coal-fired electric power plants is discussed. Chemical heterogeneity of fine particles in standard reference material fly ash and in phagocytized fly ash within pulmonary macrophages is demonstrated. This system combines the morphologic capability of the SEM with X-ray multielement mapping to provide a needed tool for particulate source identification.     

Total quality control for automotive raw foundry brake disks

In this paper, a solution for the automatic raw foundry brake disk dimensional characterisation and visual inspection for the automotive industry is presented. Three different computer vision techniques are used: a calibrated 3D structured-light vision technique, for dimensional characterisation and inspection; a 3D uncalibrated structured-light vision technique for local fault detection; and a common 2D-vision technique for a further local fault recognition. A new and fully automated 3D-calibration procedure for piece dimensional characterisation is also described. The whole system is an accurately synchronised blending of mechanics, automation, computer vision and robotics. Results from industrial implementation are presented.     

Comparison of photon transport efficiency in simple scintillation electron detector configurations for scanning electron microscope

The purpose of this paper is to find some general rules for the design of robust scintillation electron detectors for a scanning electron microscope (SEM) that possesses an efficient light-guiding (LG) system. The paper offers some general instructions on how to avoid the improper design of highly inefficient LG configurations of the detectors. Attention was paid to the relevant optical properties of the scintillator, light guide, and other components used in the LG part of the scintillation detector. Utilizing the optical properties of the detector components, 3D Monte Carlo (MC) simulations of photon transport efficiency in the simple scintillation detector configurations were performed using the computer application called SCIUNI to assess shapes and dimensions of the LG part of the detector. The results of the simulation of both base-guided signal (BGS) configurations for SE detection and edge-guided signal (EGS) configurations for BSE detection are presented. It is demonstrated that the BGS configuration with a matted disc scintillator exit side connected to the cylindrical light guide without optical cement is almost always a sufficiently efficient system with a mean LG efficiency of about 20%. It is simulated that poorly designed EGS strip configurations have an extremely low mean LG efficiency of only 0.01%, which can significantly reduce detector performance. On the other hand, no simple nonoptimized EGS configuration with a light guide widening to a circular or square profile, with a polished cemented scintillator and with an indispensable hole in it has a mean LG efficiency lower than 6.5%.     

Correlation of two‐photon in vivo imaging and FIB/SEM microscopy

Advances in the understanding of brain functions are closely linked to the technical developments in microscopy. In this study, we describe a correlative microscopy technique that offers a possibility of combining two‐photon in vivo imaging with focus ion beam/scanning electron microscope (FIB/SEM) techniques. Long‐term two‐photon in vivo imaging allows the visualization of functional interactions within the brain of a living organism over the time, and therefore, is emerging as a new tool for studying the dynamics of neurodegenerative diseases, such as Alzheimer's disease. However, light microscopy has important limitations in revealing alterations occurring at the synaptic level and when this is required, electron microscopy is mandatory. FIB/SEM microscopy is a novel tool for three‐dimensional high‐resolution reconstructions, since it acquires automated serial images at ultrastructural level. Using FIB/SEM imaging, we observed, at 10 nm isotropic resolution, the same dendrites that were imaged in vivo over 9 days. Thus, we analyzed their ultrastructure and monitored the dynamics of the neuropil around them. We found that stable spines (present during the 9 days of imaging) formed typical asymmetric contacts with axons, whereas transient spines (present only during one day of imaging) did not form a synaptic contact. Our data suggest that the morphological classification that was assigned to a dendritic spine according to the in vivo images did not fit with its ultrastructural morphology. The correlative technique described herein is likely to open opportunities for unravelling the earlier unrecognized complexity of the nervous system.     

反射光纸张边缘检测系统设计

设计并分析了一种新型的印后纸张在线光电计数器系统的组成和原理。系统采用反射式双探测器比较探测电路;为提高系统对环境光的抗干扰能力,对光源进行方波调制,配合相关检测解调光电信号,从而检测出印后纸张的折叠边沿,达到纸张计数目的。相比于目前的透射式光电计数器,现提出的反射式光电计数器在印后加工中有很高的应用价值。     

基于PSoC的智能吸尘机器人控制系统的设计

主要研究了基于PSoC片上系统的智能吸尘机器人控制系统的设计，详细论述了控制系统的组成，推导了机器人的运动控制方程，设计了传感器检测电路。该控制系统灵活运用PSoC片上系统内部集成的PWM模块、计数模块和定时模块等来完成机器人的运动控制，通过运用红外传感电路和机械结构相结合的方法来检测外部环境信息。     

A high speed photon counter system for microwave mercury ion frequency standard

This report describes a high speed photon counter system for microwave mercury ion frequency standard based on a field programmable gate array (FPGA). A high speed comparator is chosen to convert analog signal to digital pulse. A circuit with low-voltage differential signaling (LVDS) receiver in FPGA is used to capture the rising edges of the pulses. In our experiment, the clock of the Altera FPGA EP4CE10E22C8N is 80 MHz which is easy for logic design, and the de-serialization factor of the LVDS receiver is 8, the measured minimum pulse width that can be correctly captured is about 1.67 ns. As a compact and low-cost module, the photon counter system is used for the microwave mercury ion frequency standard.     

Extended algorithm for simulation of light transport in single crystal scintillation detectors for S(T)EM

The new extended Monte Carlo (MC) simulation method for photon transport in S(T)EM back scattered electron (BSE) scintillation detection systems of various shapes is presented in this paper. The method makes use of the random generation of photon emission from a scintillator luminescent centre and describes the trajectory of photons and the efficiency of their transport toward the photocathode of the photomultiplier tube. The paper explains a new algorithm for determining the position of interaction of the photon with the surface of the single crystal scintillator or of the light guide with nearly arbitrary shapes. Some examples of the utilization of the simulation method are also included, and conclusions for very simple edge-guided signal (EGS) scintillation detection systems made. The computer optimized design of the BSE scintillation detector for the S 4000 Hitachi SEM was chosen to demonstrate the capability of this MC simulation method.     

用单光子计数法测量稀土荧光材料的激发光谱

单光子计数法是弱光测量领域中的一种新技术,在生物、化学和医学等领域中具有十分重要的作用。本文介绍了新设计的稀土荧光材料激发光谱测量系统,从信号电平指出了普通模拟测量方法所存在的问题。详细讨论了设计的单光子计数测量系统。通过几个样品的测量结果表明,单光子计数法是荧光光谱等极微弱光测量中十分有效的手段     

MRT Letter: Two‐photon excitation‐based 2pi Light‐sheet system for nano‐lithography

We propose two‐photon excitation‐based light‐sheet technique for nano‐lithography. The system consists of 2 ‐configured cylindrical lens system with a common geometrical focus. Upon superposition, the phase‐matched counter‐propagating light‐sheets result in the generation of identical and equi spaced nano‐bump pattern. Study shows a feature size of as small as few tens of nanometers with a inter‐bump distance of few hundred nanometers. This technique overcomes some of the limitations of existing nano‐lithography techniques, thereby, may pave the way for mass‐production of nano‐structures. Potential applications can also be found in optical microscopy, plasmonics, and nano‐electronics. Microsc. Res. Tech. 78:1–7, 2015. © 2014 Wiley Periodicals, Inc.     

Studying the rate of data transfer through an optical communication channel with a detector based on a photon counter

The rate of data transfer through an optical communication channel with a photon counter based on an avalanche photodiode being used as a detector in this channel is studied. The rate of data transfer through the optical channel is found as a function of the reverse bias voltage of the photodiode, the optical signal power, and the threshold level of detection.     

Velocity sensing interferometer (VISAR) modification

The VISAR (velocity interferometer system for any reflector) has become a common tool used in experiments where high surface velocities must be measured. A modification that uses previously wasted interferometer light to more than double output signals and to cancel noise is described. Laser power is used more efficiently, VISAR performance in the presence of intense target self-light is improved, and only two data signals are required instead of the usual three or four. Effects of changing light intensity and fringe visibility are eliminated using a novel detection system with a simplified solution for velocity.     

Real-time data acquisition incorporating high-speed software correlator for single-molecule spectroscopy

Single-molecule spectroscopy and detection are powerful techniques for the study of single fluorescent particles and their interaction with their environment. We present a low-cost system for simultaneous real-time acquisition, storage of inter-photon arrival times and the calculation and display of the fluorescence time trace, autocorrelation function and distribution of delays histogram for single-molecule experiments. From a hardware perspective, in addition to a multi-core computer, only a standard low-cost counting board is required as processing is software-based. Software is written in a parallel programming environment with time crucial operations coded in ANSI-C. Crucial to system performance is a simple and efficient real-time autocorrelation algorithm (acf) optimized for the count rates (approximately 10⁴ cps) encountered in single-molecule experiments. The algorithm's time complexity is independent of temporal resolution, which is maintained at all time delays. The system and algorithm's performance was validated by duplicating the signal from the photon detector and sending it to both the ordinary counter board and a commercial correlator simultaneously. The data acquisition system's robustness under typical single-molecule experimental conditions was tested by observing the diffusion of Rhodamine 6G molecules in deionized water.     

Two‐photon microscopy of deep intravital tissues and its merits in clinical research

Multiphoton excitation laser scanning microscopy, relying on the simultaneous absorption of two or more photons by a molecule, is one of the most exciting recent developments in biomedical imaging. Thanks to its superior imaging capability of deeper tissue penetration and efficient light detection, this system becomes more and more an inspiring tool for intravital bulk tissue imaging. Two‐photon excitation microscopy including 2‐photon fluorescence and second harmonic generated signal microscopy is the most common multiphoton microscopic application. In the present review we take diverse ocular tissues as intravital samples to demonstrate the advantages of this approach. Experiments with registration of intracellular 2‐photon fluorescence and extracellular collagen second harmonic generated signal microscopy in native ocular tissues are focused. Data show that the in‐tandem combination of 2‐photon fluorescence and second harmonic generated signal microscopy as two‐modality microscopy allows for in situ co‐localization imaging of various microstructural components in the whole‐mount deep intravital tissues. New applications and recent developments of this high technology in clinical studies such as 2‐photon‐controlled drug release, in vivo drug screening and administration in skin and kidney, as well as its uses in tumourous tissues such as melanoma and glioma, in diseased lung, brain and heart are additionally reviewed. Intrinsic emission two‐modal 2‐photon microscopy/tomography, acting as an efficient and sensitive non‐injurious imaging approach featured by high contrast and subcellular spatial resolution, has been proved to be a promising tool for intravital deep tissue imaging and clinical studies. Given the level of its performance, we believe that the non‐linear optical imaging technique has tremendous potentials to find more applications in biomedical fundamental and clinical research in the near future.