级联光栅硅胶封装的脉象传感器研究

提出了一种基于级联光栅的脉象波传感器。相同参数的两个光纤光栅组成级联光栅并植入硅胶腕带中,其中一个光栅作为传感光栅被用于感知脉搏信号,另一个光栅作为匹配光栅被用于解调。由于两个光栅参数完全相同,其反射峰重叠,传感器反射光谱表现为单个反射峰。脉搏搏动产生的应变变化对传感光栅进行调制,导致传感光栅反射峰的中心波长产生偏移,进而导致传感器反射光的强度变化。通过对反射光的强度进行监测,即实现了脉象信息的测量和提取。实验中分别测试了健康男性青年和老年受试者,以及同一个健康男性受试者上午8时和下午8时的脉象信息。结果显示,传感器可有效提取不同受试者的脉象特征点,测试结果符合中医脉象理论。当环境温度变化时,级联光栅中两个光栅的反射峰以相同速率向同一方向偏移,传感器反射光谱的强度不变,因此该传感器不受环境温度影响。此外,该传感器具有结构简单、解调方便、成本较低等优点,在脉象测试中具有一定的应用潜力。     

Micropower Pulse Frequency Modulator for Use in an Optically Isolated Catheter System

A micropower pulse frequency modulator (PFM) has been developed for implementing an opticaily isolated system capable of making sensor voltage measurements. The PFM circuit is powered with an array of solar cells which converts light energy into electrical energy. An input port receives the sensor voltage. The PFM signal generated by the circuit drives an infrared emitting diode which provides the frequency-modulated output signal. The PFM circuit can accept sensor output voltages in the range ±500 mV and has a minimum bandwidth of 500Hz.     

分布式光纤传感双通道调制光源设计与测试

为了满足布里渊光时域分析(BOTDA)光纤传感系统需要频差为布里渊频移的两种激光输出光源的需求,采用布里渊环形腔频移和电光调制的方法设计了双通道光源系统。根据光源的脉冲宽度、重复频率、扫频量等参量,对双通道调制光谱输出进行了仿真,并采用现场可编程门阵列配合直接数字式频率合成器技术的方案建立了系统实验装置,实现了脉冲探测光和扫频抽运光两种激光输出。脉冲探测光输出最小脉宽达10ns,扫频抽运光输出扫频范围达0MHz~90MHz,扫描频率步进值为30Hz,时间步进为1.6s。结果表明,该光源技术参量满足BOTDA系统的要求,不需引入高频微波信号源等高速器件,信号采集模块可采用100MHz以下光电探测器件实现,降低了系统成本。     

基于场效应管的光电式电流传感器

提出一种新型光电式电流传感器。利用电流取样电阻将被测电流转换为电压,并利用场效应管(FET)的转移特性和发光二极管(LED)将被测电流信号转换为光强度信号,再将光信号由塑料光纤(POF)传输到光电探测器(PD),可以实现直流电流(DC)、方波脉冲电流(PC)以及工频交流电流(AC)的光学传感。综合利用FET的转移特性和PD的开路电压,并合理选择FET的静态工作点,可以实现DC的线性传感。在0.03～17.00A范围内,DC测量的非线性误差低于0.44%;方波脉冲电流响应的延迟时间约为160ns。本文提出的传感器具有响应速度快、结构简单、成本低和可实现绝缘测量等优点。     

机载脉冲式激光测距机接收电路的设计

采用硅雪崩管作为光电传感器,将光背景噪声或被测目标漫反射激光转变为微弱电压脉冲,经过两级低噪声可变增益放大器AD603放大后,信号变为幅度较大的电压脉冲,由可编程逻辑器件处理器在单位时间内收集脉冲个数,通过D/A转换电路驱动高压模块改变APD的偏压,最终设计出机载脉冲式激光测距机灵敏度高的闭环负反馈微弱激光接收电路     

Noninvasive pulse oximetry utilizing skin reflectancephotoplethysmography

The major concern in developing a sensor for reflectance pulse oximetry is the ability to measure large and stable photoplethysmograms from light which is backscattered from the skin. Utilizing a prototype optical reflectance sensor, locally heating the skin is shown to increase the pulsatile component of the reflected photoplethysmograms. Additional improvements to signal-to-noise ratio were achieved by increasing the active area of the photodetector and optimizing the separation distance between the light source and photodetector. The results from a series of in vivo studies to evaluate a prototype skin-reflectance pulse oximeter in humans are presented     

532nm激光距离选通成像系统

实现了一套基于532 nm波长的距离选通成像系统,并选择了几种典型环境进行了相应的原理验证实验。采用532 nm的全固态调Q脉冲激光器作为主动照明激光,激光单脉冲能量可以在35~100 mJ之间调节,系统接收望远镜口径为200 mm。采用PIN探测器获得激光脉冲发射时间,并控制目标成像的曝光时刻。成像探测器采用ICCD(intensified CCD),最小曝光时间为2 ns。通过实验对比说明该系统能够在小雨天或者有烟雾的情况下正常工作,但是获得图像的信噪比会有所下降,同时能够在强光背景干扰的环境下获得目标的图像信息。该套系统的原理验证性实验能够为距离选通成像技术的进一步发展提供重要参考。     

光时域反射光纤光栅传感系统中双激光器的驱动设计

为了扩大应变测量的范围,提出了使用两个分布反馈式(DFB)激光器作为光时域反射光纤光栅(OTDR-FBG)传感系统的光源的方法,并设计了相应的纳秒脉冲驱动电路和温控电路,得到两个激光器的驱动脉冲宽度分别为3.10 ns和3.18 ns,脉冲幅值分别为4.40 V和4.08 V,温度控制电路精度达到±0.04 ℃。经测试得到的纳秒脉冲和温控精度满足OTDR-FBG传感系统的要求。     

Pulse radiation from an insulated antenna: an analog of Cherenkovradiation from a moving charged particle

Cherenkov radiation arises when a charged particle moves with a constant velocity that is greater than the speed of light in the surrounding medium. This radiation has distinctive characteristics. Near the charge, the electric field is most intense along a conical surface with apex at the charge-the Mach cone. In the far field, the radiation occurs predominantly in one direction-at the Cherenkov angle. An insulated antenna consists of a metallic cylindrical conductor covered by a concentric sheath of dielectric. In use, this antenna is embedded in a medium whose permittivity is often much greater than the permittivity of the insulation. When the antenna is excited by a pulse of voltage, a pulse of charge appears to travel along its length. The apparent velocity of this charge is close to the speed of light in the insulation, which, because of the difference in the permittivities, is greater than the speed of light in the surrounding medium. Thus, the radiation from the pulse excited, insulated antenna should be analogous to Cherenkov radiation from the moving charged particle. In this paper, the pulse-excited, traveling-wave insulated linear antenna is accurately analyzed using the finite-difference time-domain (FDTD) method. Results are obtained for the charge on the conductor, the near field, and the far field. These results show the striking similarity of the radiation from this antenna to Cherenkov radiation from the moving charge     

A CMOS 3-D Imager Based on Single Photon Avalanche Diode

A 64-pixel linear array aimed at 3-D vision applications is implemented in a high-voltage 0.8 mum CMOS technology. The detection of the incident light signals is performed using photodiodes biased above breakdown voltage so that an extremely high sensitivity can be achieved exploiting the intrinsic multiplication effect of the avalanche phenomenon. Each 38times180-mum² pixel includes, besides the single photon avalanche diode, a dedicated read-out circuit for the arrival-time estimation of incident light pulses. To increase the distance measurement resolution a multiple pulse measurement is used, extracting the mean value of the light pulse arrival-time directly in each pixel; this innovative approach dramatically reduces the dead-time of the pixel read-out, allowing a high frame rate imaging to be achieved. The sensor array provides a range map from 2 m to 5 m with a precision better than plusmn0.75% without any external averaging operation. Moreover, with the same chip, we have explored for the first time the implementation of an indirect time-of-flight measurement by operating the proposed active pixel in the photon counting mode     

Novel solid-state imaging devices with inherent MNOS memory gate

A novel solid-state imaging device with an inherent MNOS memory gate is proposed and writing and reading characteristics are discussed. To improve the writing of the low light inputs, a bias charge in addition to the signal charge is transferred into the MNOS memory Capacitor from a photodiode. Both enhanced writing and a Wide dynamic range are obtained under the following optimum bias condition: a preset photodiode voltage of 5 V, a memory pulse voltage of 35 V amplitude, and a 1-10 µs duration. Moreover, it was found that the stored charge signal could be nondestructively read from drain output under bias light, provided the drain voltage VDwas biased higher than the Surface potenteal φMGin the depletion layer below the memory gate. If VD< φMG, however, incoming light signals are detected regardless of shifts in the flat-band voltage optically induced during the Writing process. Finally, the reproduced images of readout and incoming light signals are demonstrated using a 5 × 5 2-D array.     

A vision sensor with on-pixel ADC and in-built light adaptation mechanism

In this paper we propose an on-pixel Analogue-to-Digital Converter (ADC) based on pulse frequency modulation (PFM) scheme. This PFM based converter presents a viable solution for pixel-level based ADC. It uses a simple and robust circuit that can be implemented in a compact area resulting in a 23% fill-factor for a digital vision sensor in 0.25 μm CMOS technology. An in-built light adaptation mechanism has also been implemented which allows the sensor to better adapt to low-light intensity or to adjust the sensor saturation level. As a consequence, the proposed sensor features a programmable dynamic range. Image lag is eliminated since a reset of the photodetector is performed after the conversion period. A prototype comprising a 32×32 pixel array has been implemented in CMOS 0.25 μm technology. Each pixel occupies an area of 45×45 μm² with an average power consumption of 85 μW per pixel.     

A 360 000-pixel charge-coupled color-image sensor for imaging photographic negative

A 360 000-pixel color-image sensor for imaging photographic negatives is described. The charge-coupled image sensor consists of a 740 (H) × 242 (V) × 2 image area and dual horizontal output registers. The design, spectral response, charge capacity, noise, and image quality of the sensor are discussed. The sensor achieves a charge capacity of 1 × 10⁶electrons per pixel and a noise of 200 rms electrons per pixel, for a dynamic range of 70 dB. Color sensitivity is obtained by an organic color-filter array fabricated on the sensor.     

井下热示踪流量测量电路研究与设计

本文介绍一种基于在线加热方式无可动部件的井下热示踪相关流量测量电路。测量装置由热源发生器、温度传感器阵列以及测量与控制电路构成。热源发生器通过电容在极短时间的充放电来加热流体,当被加热的流体经过传感器阵列时,由于温差传感器阵列产生信号突变,测出脉冲信号的渡越时间以及传感器阵列的物理距离就可以测出油水两相流的流量,经实验验证,效果良好。     

Transient response times of a-Si : H p-i-n color detector

Transients and relevant response times of a-Si : H p-i-n photodetector under various illuminations (in the visible range) and bias voltage conditions were studied. The model/method for possible color detection using on and off transient response times is proposed. Depending on illumination and bias pulse types, one or two processes are found to be involved in the conduction mechanism, including transition and trapping of both charge carrier types. Characteristic photocurrent transients and response times under modulated monochromatic and chromatic visible light illumination enable color recognition. The peculiar behavior of the blue light transients has been also plausibly explained by means of the proposed model.     

The low light level potential of a CCD imaging array

Some limitations to the operation of a CCD TV camera sensor at low light levels are discussed. Transfer inefficiency with small charge packets is analyzed theoretically, and the prediction made that with good processing this should not be a serious problem. The principal limitation is seen to be the output amplifier, and a new low-noise output detector, the "floating surface detector," is described in detail. At -50°C it yields a noise equivalent signal of 16 electrons and a dynamic range of 85 dB over a 1-MHz video bandwidth.     

Transient high level majority and minority carrier photocurrents in p-type silicon Schottky barrier diodes—II: Comparison with computer calculations

Computer calculations of majority and minority carrier transient current pulses in a totally depleted silicon diode are compared with experimental current pulse shapes obtained by light pulse excitation of the diode. Numerical solution of the transport equations permitted the roles of the field dependence of the carrier mobility and of the excitation depth of the exciting light pulse to be investigated. Improved agreement of the computer solution as compared to previously made analytical calculations, particularly under conditions of high electric field or high space charge, is found.     

A 2 million pixel FIT-CCD image sensor for HDTV camera systems

A 1-in optical format frame-interline-transfer charge-coupled-device (FIT-CCD) image sensor with 2 million pixels and an aspect ratio of 16(H):9(V) has been developed for HDTV cameras. The effective number of pixels is 1920(H)×1036(V). In order to decrease the smear level, achieve uniform charge handling capability for the vertical CCD, and eliminate defects that appear as vertical stripes in the image of the device, aluminum wire was put onto the vertical transfer gate to decrease the resistance in the transfer gate and a dual-channel two-phase CCD was utilized for the horizontal shift register operated by a 37.125-MHz clock. As a result, this image sensor has a dynamic range of 72 dB and a sensitivity of 75 nA/lx for light with a color temperature of 2856 K. Smear is reduced to -100 dB by using the FIT-CCD image sensor structure. The horizontal limit is 1000 TV lines. In addition, image lag is negligibly small and below the sensitivity of the measurement instrument     

Simulation and measurement of multiplication in thin-filmelectroluminescent devices with doped probe layers

When a single voltage pulse is applied to an electroluminescent (EL) device after previous illumination, the current through the phosphor layer will normally not be homogeneous, but increase from the cathodic side-where the electrons tunnel from-to the anodic side, due to multiplication. The positive charges that remain after the multiplication process cause a positive space charge that has been observed in various experiments and influences the efficiency. In this paper a simple numerical model is proposed for the calculation of charge transfer and light emission, in the case that multiplication takes place during a voltage pulse after previous illumination     

Design and implementation of a non-mechanical scanning F-P type laser warning method

In the laser warning system, a non-mechanical scanning Fabry-Perot (F-P) type laser warning method and its crucial component-laser incident sensor design method are brought out, and the F-P etalon with the interferometric filter combination is adopted. For the incident laser pulse with a certain wavelength, the transmittance difference of the interferometric filters is independent with polarization of incident light, and descends almost linearly as the incident angle gets wider. A laser incident angle sensor experimental platform is built up, and the experiment is carried out with a given laser range finder. As the results indicate, when the incident angle is less than 5°, the transmittance difference measured by the laser angle sensor is significantly lower, and the deviation is more than 10%. While the incident angle is greater than 10°, the deviation is reduced significantly.