SOI digital pixel sensor based on charge pumping

In this paper, a digital pixel sensor in silicon on insulator (SOI) is presented. The active part is a partially depleted SOI phototransistor. The technique elaborated in Harik et al. (2008) [1] was designed and implemented. Moreover, we took advantage of some of the characteristics of the floating body SOI MOSFET to implement a first order delta sigma modulator in each pixel. Measured data show that the pixel has a sensitivity of 3 mW/m² and a resolution of about 7 bits. This pixel can be operated in two modes: weak inversion (I_dc=1.2 μA) and moderate inversion (I_dc=15 μA).     

A novel adaptive logarithmic digital pixel sensor

A major problem associated with complementary metal-oxide-semiconductor and charge couple device imagers is their limited dynamic range (DR), typically 60-70 dB. This falls far short of covering the wide illumination ranges found in natural scenes (typically 120-140 dB). Biological retinas are known to feature adaptive, logarithmic-type responses enabling them to cover a very wide DR, without compromising the resolution. This letter presents a novel way to realize such an adaptive logarithmic response by combining a digital time domain vision sensor and a simple adaptive digital quantizer. This letter presents the theory and experimental results for an adaptive logarithmic response sensor featuring over 100-dB DR.     

CMOS数字像素传感器噪声研究

在研究CMOS数字像素传感器(DPS)噪声特性的基础上,利用脉冲宽度调制(PWM)原理建立了关于PWM DPS完善的系统噪声数学模型。相比于传统CMOS图像传感器噪声研究,该模型考虑了系统中各像素单元积分时间不同和像素级模数转换的特点,推导出总噪声表达式。研究表明,低照度时噪声由暗电流散粒噪声主导,光强大时主要来源为光电二极管散粒噪声。模型中光电二极管散粒噪声与光照无关、暗电流散粒噪声与光照有关。研究结果表明针对PWM DPS系统,适当增大节点电容和比较器参考电压、改善比较器失配可有效降低噪声。     

Noise in a CMOS digital pixel sensor

Based on the study of noise performance in CMOS digital pixel sensor(DPS),a mathematical model of noise is established with the pulse-width-modulation(PWM) principle.Compared with traditional CMOS image sensors,the integration time is different and A/D conversion is implemented in each PWM DPS pixel.Then,the quantitative calculating formula of system noise is derived.It is found that dark current shot noise is the dominant noise source in low light region while photodiode shot noise becomes significantly important in the bright region. In this model,photodiode shot noise does not vary with luminance,but dark current shot noise does.According to increasing photodiode capacitance and the comparator’s reference voltage or optimizing the mismatch in the comparator,the total noise can be reduced.These results serve as a guideline for the design of PWM DPS.     

A digital pixel image sensor for real-time readout

An experimental digital image sensor that converts analog video signals into 8-bit digital signals for each unit pixel, and reads out the signals at an operating clock of standard TV has been developed. Each pixel is equipped with a photodiode, a 1-bit analog-to-digital converter (1-bit ADC), an 8-bit pulse counter, and a signal processing circuit. The sensor system displays a two-dimensional (2-D) image in real time. The 1-bit ADC has a dynamic range of 110 dB at an operating voltage of 1.3 V. “Knee” characteristics and the results of an investigation into random noise sources in the circuit are also described     

A 10000 frames/s CMOS digital pixel sensor

A 352×288 pixel CMOS image sensor chip with per-pixel single-slope ADC and dynamic memory in a standard digital 0.18-μm CMOS process is described. The chip performs "snapshot" image acquisition, parallel 8-bit A/D conversion, and digital readout at continuous rate of 10000 frames/s or 1 Gpixels/s with power consumption of 50 mW. Each pixel consists of a photogate circuit, a three-stage comparator, and an 8-bit 3T dynamic memory comprising a total of 37 transistors in 9.4×9.4 μm with a fill factor of 15%. The photogate quantum efficiency is 13.6%, and the sensor conversion gain is 13.1 μV/e^-. At 1000 frames/s, measured integral nonlinearity is 0.22% over a 1-V range, rms temporal noise with digital CDS is 0.15%, and rms FPN with digital CDS is 0.027%. When operated at low frame rates, on-chip power management circuits permit complete powerdown between each frame conversion and readout. The digitized pixel data is read out over a 64-bit (8-pixel) wide bus operating at 167 MHz, i.e., over 1.33 GB/s. The chip is suitable for general high-speed imaging applications as well as for the implementation of several still and standard video rate applications that benefit from high-speed capture, such as dynamic range enhancement, motion estimation and compensation, and image stabilization     

GaN基紫外数字像素光电传感器设计与实现

介绍了一种为了获得高速高性能的GaN基紫外数字像素光电传感器的设计和实现。该传感器每个像素单元面积为50 μm×50 μm,包含一个UV光电探测器,一个1位比较器和一个3 T的存储单元,能同时完成对所有像素的A/D转换。像素内比较器电路中引入了一个自动复位电路用以实现数字相关双采样功能,并可以增加峰值信噪比以及动态范围。电路采用CSMC DPTM 0.5 μm CMOS工艺流片实现,初步的功能实验结果验证这一数字传感器能正常工作。     

A digital pixel sensor array with programmable dynamic range

This paper presents a digital pixel sensor (DPS) array employing a time domain analogue-to-digital conversion (ADC) technique featuring adaptive dynamic range and programmable pixel response. The digital pixel comprises a photodiode, a voltage comparator, and an 8-bit static memory. The conversion characteristics of the ADC are determined by an array-based digital control circuit, which linearizes the pixel response, and sets the conversion range. The ADC response is adapted to different lighting conditions by setting a single clock frequency. Dynamic range compression was also experimentally demonstrated. This clearly shows the potential of the proposed technique in overcoming the limited dynamic range typically imposed by the number of bits in a DPS. A 64 /spl times/ 64 pixel array prototype was manufactured in a 0.35-/spl mu/m, five-metal, single poly, CMOS process. Measurement results indicate a 100 dB dynamic range, a 41-s mean dark time and an average current of 1.6 /spl mu/A per DPS.     

一种适用于异步无线传感器网络的机会路由机制

无线传感器网络通常使用低占空比的异步睡眠调度来降低节点能耗。由于发送节点在接收节点醒来后才能向其发送数据,这将引入额外的等待时延。在最近的一些任播路由机制中,发送节点动态地选择最先醒来的候选节点转发数据,以最小化等待时延。但是,由于从最先醒来的候选节点到基站的时延可能并不低,任播路由机制并不一定能最小化端到端总时延。为此,提出了一种适用于异步无线传感器网络的机会路由机制,将路由决策建模为强马尔科夫过程,并根据最优停止理论推导出该过程一种简化的停止规则。仿真结果表明,节点到基站的最大端到端时延仅为基于地理位置的机会路由的68.5%。     

Identification and replacement of defective pixel based on Matlab for IR sensor

Infrared focal plane arrays (IRFPAs) usually contain many defective pixels.These defective pixels have to be corrected because those can significantly impair the performance of infrared image of IRFPAs...     

基于AD8205型高端电流传感器的 PWM电流控制器

高精度大电流控制器有着广泛的应用,但在高共模电压情况下输出电流的检测电路比较复杂.AD8205型高端电流传感器可以简化检测电路,采用AD8205和UC3842电流型PWM控制电路实现PWM可调电流源,电路结构简单可靠,输出电流精度高.     

Harmonic imbalance in asynchronous PWM schemes

The harmonic content (both integral and nonintegral) of an asynchronous three-phase PWM (pulse width modulated) scheme is analyzed. It is shown that in a three-phase inverter with asynchronous modulation the nonintegral line currents produced form unbalanced sets. The percentage imbalance for a particular order is a function of the harmonic order only. No attempt has been made here to analyze the effect of harmonic imbalance in a load such as an induction motor. However, for practical frequency ratios the absolute amplitude of the current imbalance is small due to the small amplitude of the nonintegral components. More significant changes occur in the balanced integral orders due to small changes in frequency ratio     

A wide dynamic range CMOS PFM digital pixel sensor with in-pixel variable voltage reference

This paper proposes a new pulse-frequency-modulation (PFM) digital pixel sensor (DPS) with a variable reference voltage. An in-pixel variable reference voltage generator is employed to ramp the reference voltage of the comparator locally such that the comparison of photo diode current and the reference voltage can take place earlier. This expands the dynamic range of the pixel sensor when the level of illumination is low. The complexity of routing of the proposed pixel sensor are comparable to that of digital pixel sensor with a constant reference voltage. The additional hardware cost of the proposed digital pixel sensor is only a capacitor and two static inverters, resulting in a fill factor that is comparable to those of digital pixel sensors with a constant global reference voltage. Factors that are critically to the performance of the proposed pixel sensor are examined in detail. The proposed digital pixel sensor has been designed in TSMC-0.18 μm 1.8 V CMOS technology and analyzed using Spectre with BSIM3V3 device models. Simulation results demonstrate that the proposed PFM digital pixel has a dynamic range of 120 dB when the integration time is set to 60 μs, approximately 40 dB more than the corresponding PFM digital pixel sensor with a constant reference voltage. The fill factor of the proposed pixel sensor is 20%, comparable to that of pixel sensors with a constant reference voltage.     

A new CMOS multimode digital pixel sensor dedicated to an implantable visual cortical stimulator

We describe in this paper a new CMOS multimode image pixel sensor (MIPS) dedicated to an implantable visual cortical stimulator. Each 16 μm × 16 μm pixel area contains a photodiode, with a fill factor of 22%, a comparator used to convert the pixel level from analog to digital (A/D) values and an 8-bit DRAM, resulting in a total of 44 transistors per pixel. The A/D conversions use one common digital to analog converter to deliver the voltage reference needed to determine the pixel voltage. Three selectable operation modes are combined in the proposed MIPS: A high dynamic range logarithmic mode, a linear integration mode, and a novel differential mode between two consecutive images. This last mode that allows 3D information is required for a visual cortical stimulator. A test chip has been fabricated in CMOS 0.18 μm technology and tested to validate the full operation of the different proposed modes. Mohamad Sawan received the B.Sc. degree in electrical engineering from Université Laval, Canada in 1984, the M.Sc. and Ph.D. degrees, both in electrical engineering, from Université de Sherbrooke, Canada, in 1986 and 1990 respectively, and postdoctorate training from McGill University, Canada in 1991. He joined Ecole Polytechnique de Montréal in 1991 where he is currently a Professor in Microelectronics. His scientific interests are the design and test of mixed-signal (analog, digital and RF) circuits and systems, the digital and analog signal processing, the modeling, design, integration, assembly and validation of advanced wirelessly powered and controlled monitoring and measurement techniques. These topics are oriented toward the biomedical implantable devices and telecommunications applications. Dr. Sawan is a holder of a Canadian Research Chair in Smart Medical Devices. He is leading the Microelectronics Strategic Alliance of Quebec (Regroupement stratégique en microélectronique du Québec – ReSMiQ). He is founder of the Eastern Canadian IEEE-Solid State Circuits Society Chapter, the International IEEE-NEWCAS conference, and Polystim neurotechnologies laboratory at the Ecole Polytechnique de Montreal. He is cofounder of the International Functional Electrical Stimulation Society (IFESS), and the IEEE International Conference on Electronics, Circuits and Systems (ICECS). Dr. Sawan is involved in the committees of many national and international conferences and other scientific events. He published more than 350 papers in peer reviewed journals and conference proceedings and is awarded 6 patents. He is editor of the Springer Mixed-signal Letters, Distinguished Lecturer for the IEEE CAS Society, President of the biomedical circuits and systems (BioCAS) technical committee of the IEEE CAS Society, and he is representative of IEEE-CAS in the International Biotechnology council. He received the Barbara Turnbull 2003 award for spinal cord research, the Medal of Merit from Lebanon, and the Bombardier Medal from the French Association for the advancement of sciences. Dr. Sawan is Fellow of the Canadian Academy of Engineering, and Fellow of the IEEE. Annie Trépanier received her Bachelor of Engineering Degree in Electrical Engineering in 2002 and her Master of Applied Sciences Degree in Microelectronics in 2005 from the Ecole Polytechnique de Montreal as a member of the Cortivision team in the Polystim Neurotechnologies Laboratory. She held a summer job at Nortel Networks and trained at Mindready. She is currently employed at Matrox, Montreal. Jean-Luc Trépanier received his Bachelor of Engineering Degree in Electrical Engineering in 2000 and his Master of Applied Sciences Degree in Microelectronics in 2003 from the Ecole Polytechnique de Montreal where he was a member of the Cortivision team in the Polystim Neurotechnologies Laboratory. He started his first company, Olyxia inc., where he developed the soon to be released Cute Spider VoIP Network. He is also the founder and CEO of Nexyrius inc. which develops a new generation of embedded systems. Yves Audet received his M.Sc. degree from a joint program between the University of Sherbrooke, QC, Canada and Université Joseph Fourier in Grenoble, France. He completed his Ph.D. at Simon Fraser University, BC, Canada. He has been working for three years in Research and Development with Mitel Corporation before being hired as assistant professor at école Polytechnique of Montreal, QC, Canada, in 2001. His research interests are CMOS sensor arrays and mixed signal circuits. Roula Ghannoum received her Bachelor of Engineering Degree in Computer and Communications Engineering from the Lebanese American University, Byblos—Lebanon, in July 2005. She is currently pursuing her Master of Applied Sciences in Microelectronics at the Ecole Polytechnique de Montreal as a member of the Cortivision team in the Polystim Neurotechnologies Laboratory working on image sensors as part of a global project that aims at restoring sight to the visually incapacitated.     

CMOS active pixel image sensor

A new CMOS active pixel image sensor is reported. The sensor uses a 2.0 μm double-poly, double-metal foundry CMOS process and is realized as a 128×128 array of 40 μm×40 μm pixels. The sensor features TTL compatible voltages, low noise and large dynamic range, and will be useful in machine vision and smart sensor applications     

Low-power spiking chemical pixel sensor

An ISFET-based integrate and fire neuron, forming the front-end of a chemical pixel sensor, is introduced. With the sense data being encoded in the spike domain, i.e. asynchronous/continuous time and discrete value, it is directly compatible with asynchronous communication hardware, e.g. address event representation. The circuit is shown to be tunable to yield a linear relation with both pH and actual hydrogen ion concentration, with a peak power consumption of 35 muW. Furthermore, its compact pixel footprint of under 6500 mum², makes it ideal for use in arrayed architectures with application in biochemical imaging     

基于MC74型电路的无线数字温度传感器

MC74型串行数字温度传感器具有价格低、精度高、串行线性输出等优点.介绍该电路的主要工作特性及工作原理,给出利用MC74设计的无线数字温度传感器电路的原理及部分程序代码.     

Threshold voltage shift compensated active pixel sensor array for digital X-ray imaging in a-Si technology

A new active pixel sensor for X-ray digital imaging using amorphous silicon thin-film transistors (a-Si TFTs) is proposed. Simulation results show that this new APS structure is fully capable of compensating for variations in threshold voltage (V/sub T/) of a-Si TFTs under prolonged gate voltage stress.     

PWM数字可调均匀光源的设计

发光二极管(Light Emitting Diode,LED)作为一种场致发光光源,已经获得广泛的应用,但在影像测量中的下照明领域还处于起步和探索阶段。影像测量中,光照不均匀或者光强不适,都会影响所拍摄图像的质量。为获得高质量的图像,设计一种基于PWM数字可调的均匀光源系统,用于下照明的影像测量。系统通过正交实验法获得环形的LED阵列、灯的倾角、LED灯的数量、LED的环形直径等,搭建光源系统,使得LED环形阵列在视场2cm内获得均匀的光强,结合LED发光特性设计PWM脉冲发生电路,通过上位机的软件让均匀光源强度256级可调,适合各种不同的场合,增强实用性。实验数据表明,利用光学显微影像测量系统,在最小放大倍率0.7倍以及最大放大倍率4.5倍两种极端情况下,检测4个级别的光强均匀性都超过了83%。该系统完全能够在影像测量中达到要求。     

一种基于图像融合的数字水印方案

数字水印是一种新型的多媒体信息版权保护技术，它是在多媒体信息中嵌入标志版权信息的不可感知且难以去除的水印信息，通过检测水印信息来进行版权保护及盗版跟踪，从而有效地弥补了数字加密技术的不足之处。提出了一种具有良好鲁棒性的数字水印方案。由于该方案利用人眼视觉系统把数字水印嵌入到图像的视觉重要区域中，对水印的破坏将会非常困难。