A 128×128-pixel standard-CMOS image sensor with electronicshutter

A 128×128-pixel image sensor with a 20 s-10^-4 s electronic shutter has been integrated in a 1.2-μm digital CMOS technology. The pixel cell consists of four PMOS transistors and a photodiode with antiblooming suppression. Each pixel measures 24 μm by 24 μm and has a fill factor of 25%. Current is used to transfer pixel signals to the column readout amplifiers in order to minimize voltage swings on the highly capacitive column lines. Correlated double sampling is used to reduce intracolumn fixed pattern noise. The saturation voltage is 470 mV. The peak output signal to noise ratio is 45 dB, and the optical dynamic range is 56 dB. The frame transfer rate is 1.7 ms per frame     

A new current mode APS in 0.18 μm standard CMOS process for smart image sensors

In this paper we present a new current mode structure for active pixel sensor (APS) which is an essential part in fast parallel processing Smart CMOS Image Sensors such as wireless capsule endoscopy. Using two diodes (N+/P-Well and P-Well/Deep-N-Well) in parallel like a pinned photo-diode (PD) improves sensing of optical signal and thus leads to higher sensitivity than a conventional PD. Also integrated signal amplification inside the collection area of the pixel increases the sensitivity of the device due to the amplification in the pixel. The proposed structure with regards to using Deep-N-Well/P-Substrate junction as a guard ring, suppresses the pixel cross-talk highly. In pixel delta reset sampling helps to make feasible on-chip parallel processing. A test structure, consist of 8 × 8 pixels of the proposed current mode APS has been simulated by standard 0.18 μm RF-CMOS technology of TSMC with a 21 × 23 μm² pixel size. Fill factor of the pixel is 24 %.     

一种改进的基于ViBe的运动目标检测方法

ViBe运动检测算法消除鬼影的速度慢,并且在分类像素点的时候由于距离阂值固定导致检测结果的准确率下降.文章对ViBe算法存在的这两个问题做出改进.样本的选取范围由8邻域扩大到24邻域,避免选择重复的样本,加快鬼影的消除过程;在像素分类的时候根据背景动力学自适应地确定距离阈值,增强算法抗背景干扰的能力,并选用2组视频来验证改进后的算法.从检测结果可以看出,改进后的算法去除鬼影的速度更快,并且检测结果更加准确.     

A current mode active pixel with high sensitivity pinned PD in standard CMOS process for smart image sensors

In this paper we present a current mode structure for Active Pixel Sensor (APS) which is an essential part in fast Smart CMOS Image Sensors (SCIS). Using two diodes (N+/P-Well and P-Well/Deep-N-Well) in parallel like a Pinned Photo-Diode (PPD) improves sensing of optical signal and leads to higher sensitivity than a conventional Photo-Diode (PD). Also integrated signal amplification inside the collection area of the pixel increases the sensitivity of the device due to the amplification in the pixel. The proposed structure with regards to using Deep-N-Well/P-Substrate junction as a guard ring, suppresses the pixel Cross-Talk (CTK) highly. In pixel Delta Reset Sampling (DRS) architecture helps to make feasible on-chip parallel processing. A post layout simulation for test structure of the proposed current mode APS has been considered by standard 0.18 µm RF-CMOS technology of TSMC with a 10 µm×10 µm PD size. Fill factor of each pixel is 24%.     

A signal-processing CMOS image sensor using a simple analog operation

We have developed a high-density CMOS image sensor with a normal mode and three signal-processing function modes: wide dynamic-range mode, motion-detection mode, and edge-extraction mode. Small pixel size and real-time operation are achieved by using a four-transistor and one-capacitor pixel scheme and column-parallel on-chip analog operation. The chip includes 512 (H) /spl times/384 (V) effective pixels. Each pixel has a sufficient fill factor of 24% in an area of 9.3/spl times/9.3 /spl mu/m/sup 2/. The dynamic range at the wide dynamic-range mode is a maximum 97 dB against 51 dB at the normal-readout mode. The chip consumes 79 mW, and the gain-control amplifier and 8-b analog-to-digital converter operate at 46 frames/s using a 3.3-V single power supply.     

多孔同轴度检测系统的研制

提出了一个多孔同轴度检测系统,它以无衍射激光束作为检测基准。介绍了检测原理和检测系统特别是检测靶的结构。用640pixel×480pixel的摄像机(光靶分辨率为0.0504mm/pixel),在5、15和24m进行同轴度检测,获得的标准差在x方向上分别为0.0193、0.0262和0.0428mm,在y方向上分别为0.0147、0.0181和0.0250mm。     

High-sensitivity and no-crosstalk pixel technology for embeddedCMOS image sensor

A high-photosensitivity and no-crosstalk pixel technology has been developed for an embedded active-pixel CMOS image sensor, by using a 0.35-μm CMOS logic process. To increase the photosensitivity, we developed a deep p-well photodiode and an antireflective film, consisting of Si₃N₄ film, for the photodiode surface. To eliminate the high voltage required for the reset transistor in the pixel, we used a depletion-type transistor as the reset transistor. The reset transistor also operates as an overflow control gate, which enables antiblooming overflow when excess charge is generated in the photodiode by high-illumination conditions. To suppress pixel crosstalk caused by obliquely incident light, a double-metal photoshield was used, while crosstalk caused by electron diffusion in the substrate was suppressed by using the deep p-well photodiode. A 1/3-in 330-k-pixel active-pixel CMOS image sensor was fabricated using this technology. A sensitivity improvement of 110% for 550-nm incident light was obtained by using the deep p-well photodiode, while an improvement of 24% was obtained by using the antireflective film. The pixel crosstalk was suppressed to less than 1% throughout the range of visible light     

POLYNOMIAL MODEL BASED FAST FRACTIONAL PIXEL SEARCH ALGORITHM FOR H.264/AVC

This paper proposed a novel fast fractional pixel search algorithm based on polynomial model. With the analysis of distribution characteristics of motion compensation error surface inside tractional pixel searching window, the matching error is fitted with parabola along horizontal and vertical direction respectively. The proposcd searching strategy needs to check only 6 points rather than 16 or 24 points, which are used in the l lierarchical Fractional Pel Search algorithm （HFPS） for 1/4-pel and 1/8-pel Motion Estimation （ME）. The experimental results show that the proposed algorithm shows very good capability in keeping the rate distortion performance while reduces computation load to a large extent compared with HFPS algorithm.     

A new CMOS pixel structure for low-dark-current and large-array-size still imager applications

A pixel structure for still CMOS imager application called the pseudoactive pixel sensor (PAPS) is proposed and analyzed in this paper. It has the advantages of a low dark current, high signal-to-noise ratio, and a high fill factor over the conventional passive pixel sensor imager or active pixel sensor imager. The readout circuit called the zero-bias column buffer-direct-injection structure is also proposed to suppress both the dark current of the photodiode and the leakage current of row switches by keeping both biases of photodiode and the parasitic p-n junction in the column bus at or near zero voltage. The improved double delta sampling circuits are also used to suppress fixed pattern noise, clock feedthrough noise, and channel charge injection. An experimental chip of the proposed PAPS CMOS imager with the format of 352/spl times/288 (CIF) has been fabricated by using a 0.25-/spl mu/m single-poly-five-level-metal (1P5M) n-well CMOS process. The pixel size is 5.8 /spl mu/m/spl times/5.8 /spl mu/m. The pixel readout speed is from 100 kHz to 10 MHz, corresponding to the maximum frame rate above 30 frames/s. The proposed still CMOS imager has a fill factor of 58%, chip size of 3660 /spl mu/m/spl times/3500 /spl mu/m, and power dissipation of 24 mW under the power supply of 3.3 V. The experimental chip has successfully demonstrated the function of the proposed new PAPS structure. It can be applied in the design of large-array-size still CMOS imager systems with a low dark current and high resolution.     

A method of block truncation coding for color image compression

A basic color block truncation coding (CBTC) algorithm for color image compression is described. A modification of the algorithm that reduces truncation errors is also described. The block statistics related to CBTC methods are investigated. Some experimental results are given for a 256-×256-pixel color image with 24 b/pixel     

A novel fuzzy system for edge detection in noisy image using bacterial foraging

Bio-inspired edge detection using fuzzy logic has achieved great attention in the recent years. The bacterial foraging (BF) algorithm, introduced in Passino (IEEE Control Syst Mag 22(3):52–67, 2002) is one of the powerful bio-inspired optimization algorithms. It attempts to imitate a single bacterium or groups of E. Coli bacteria. In BF algorithm, a set of bacteria forages towards a nutrient rich medium to get more nutrients. A new edge detection technique is proposed to deal with the noisy image using fuzzy derivative and bacterial foraging algorithm. The bacteria detect edge pixels as well as noisy pixels in its path during the foraging. The new fuzzy inference rules are devised and the direction of movement of each bacterium is found using these rules. During the foraging if a bacterium encounters a noisy pixel, it first removes the noisy pixel using an adaptive fuzzy switching median filter in Toh and Isa (IEEE Signal Process Lett 17(3):281–284, 2010). If the bacterium does not encounter any noisy pixel then it searches only the edge pixel in the image and draws the edge map. This approach can detect the edges in an image in the presence of impulse noise up to 30%.     

基于相对比率的高帧频图像采集器设计与实现

为了在机器视觉应用中是实现高动态范围（high dynamic range,HDR）图像采集,提出了一种基于检测像素相对比率的新型图像采集系统。提出的图像采集器使用全差分电路检测信号比,由基于数字计数器的紧凑列并行读出电路捕捉像素的脉冲宽度调制输出。并设计了相应的光电流比检测像素方法,能独立地捕捉局部场景特征。实验结果显示提出的COMS图像传感器性能较好,当标称帧频为9600帧/秒时,提出的32×32像素阵列原型CMOS图像传感器消耗了4 mW的功率;当最大帧频为24000帧/秒时,此图像传感器消耗了6.8 mW的功率。     

像素位置偏差对质心定位精度的影响

为提高微型星敏感器的质心定位精度,提出了一种利用外差式激光干涉装置标定图像传感器像素位置偏差的方法,并就像素位置偏差对星点像质心定位精度的影响进行了仿真研究。在噪声忽略不计的情况下,当像素位置偏差服从（-0.02,0.02）上的均匀分布时,补偿系统误差能够使星点定位精度从0.008 pixel提高到0.002 pixel。而如果加入服从N（0,5.52）的高斯白噪声,当像素位置偏差服从（-0.02,0.02）上的均匀分布时,补偿像素位置偏差能使定位精度从0.020 pixel提高到0.018 pixel;当像素位置偏差服从（-0.04,0.04）上的均匀分布时,补偿像素位置偏差能使定位精度从0.026 pixel提高到0.018 pixel,提高了31%。这说明标定像素位置偏差对提升质心定位精度有显著作用,为发展高精度微型星敏感器提供了一种新的技术手段。     

DCT transform coding of stereo images for multimedia applications

One form of multimedia finding increasing utility in factory automation is stereo imaging. Its uses include remote operation, telepresence, and object positioning. Stereo imaging, with doubled frames, requires high data-rate collection and transmission. Image compression techniques can be utilized to reduce the transmission bandwidth and/or storage space requirements of the stereo pair. This paper develops image compression techniques specific to stereo imaging and compares the performance with nonstereo methods. Disparity compensated residual image coding exploits the redundancy between the two images in a stereo pair. Stereo residuals possess special features that can be exploited within a discrete cosine transform (DCT) image coding framework. Use of these features results in several decibels of performance enhancement across a range of scene types. This approach provides its best performance below 0.75 b/pixel bitrate for 8-b grayscale imagery and below 2 b/pixel for 24-b color imagery     

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 100 dB Dynamic-Range CMOS Vision Sensor With Programmable Image Processing and Global Feature Extraction

A 128 times 64 pixel programmable vision sensor performs real-time analog image processing over high dynamic range images is reported. The pixel-parallel single instruction multiple data (SIMD) architecture executes real-time spatio-temporal filtering with 2.8 GOPS/mm² and large flexibility in coefficient assignment. The sensor uses time-based and pulse-based operating modalities to execute spatio-temporal filtering on images with dynamic range up to about 100 dB. The in-pixel processing is based on two operations: the absolute value of voltage difference and accumulation of partial results. Feature extraction from the entire image is also possible without the need for image dispatching, thus optimizing both processing speed and video bandwidth. The 32.6 mum square pixel, with a fill-factor of 24%, consists of two analog memories and 28 transistors. The sensor, fabricated in 0.35 mum CMOS technology, gives a fixed pattern noise (FPN) of 0.8% and power consumption of 14 mW at 3.3 V     

一种基于时间Kalman估计器的红外小目标检测方法

目标在经过一个像素时,随着目标移动到该像素或离开该像素,该像素的灰度值会在出现一个冲击.据此提出了一种基于时间的Kalman单步估计器单像素处理算法,给出了Kalman估计器的递推方程.由前一时刻(前一帧)的估计结果和当前时刻的输入图像各点的灰度值,可以得到下一时刻(下一帧)图像各个像素点的背景估计,整个图像去除背景后就得到一幅包含目标的噪声图像,进而可以完成目标检测.采用红外图像序列进行了实验,实验结果验证了理论分析的正确性.最后得出了一些结论.     

Characterization of AMOLED pixel circuit without power line

We fabricated and evaluated the simple active matrix organic light emitting diode (AMOLED) pixel circuits without power line and proved that it is useful for the AMOLED display. Without power line in the pixel circuit we got higher-aperture ratio of emission area than the pixel with power line and the pixel with high aperture ratio can give a long life time due to lower current density of organic light emitting diode. However, the lack of power line requires the verification of the driving scheme of the pixel circuit. After fabrication of two types of AMOLED with and without power line in the pixel, we evaluated the pixel currents under various conditions. The operation of the pixel circuit without power line gave similar characteristics to that of the pixel circuit with power line. By the comparison, we verified that the pixel without power line is acceptable for the application to the AMOLED display combined with feedback compensation scheme for the uniform brightness.     

Sub-1-V Supply Self-Adaptive CMOS Image Sensor Cell With 86-dB Dynamic Range

This letter presents a high dynamic range CMOS active pixel structure operating at a sub-1-V supply voltage, which is implemented using a standard 0.18-mum CMOS logic process. In order to improve the output voltage swing range and associated pixel dynamic range at a low supply voltage, a pMOS reset structure is incorporated into the pixel structure along with a photogate pixel structure based on the self-adaptive photosensing operation. At a low supply voltage of 0.9 V, the new pixel provides an output voltage swing range of 0.41 V and a high dynamic range of 86 dB, which is the highest among the reported pixel structures up to date operating at sub-1-V     

气动光学效应像素偏移图像校正方法研究

针对气动光学效应引起的图像像素偏移问题,提出了一种基于特征点配准的校正方法,并建立了像素偏移的数学模型。由于高速流场引起的像素偏移具有很强的随机性和非线性等特点,该方法在根据序列多帧图像的像素点偏移变化的统计规律获取原图像的像素点初始位置的基础上,采取二阶非线性函数模型来拟合畸变图像的像素偏移量,从而实现对各帧畸变图像的像素偏移校正。在微机上进行了仿真校正实验,结果表明该方法有效。