Kinds Of Pixels Research Articles

Investigation of random telegraph signal in CMOS image sensors irradiated by protons.

ABSTRACT CMOS image sensors were irradiated by protons of 50 and 70 MeV and the dark current random telegraph signal (RTS) is investigated. After exposure to the protons, the experimental results provide new evidence that confirms the existence of a correlation between radiation-induced hot pixels and RTS pixels. Moreover, the evolutions of the percentage of hot pixels showing RTS behavior at distinct conditions are presented, suggesting the different dependence of two kinds of pixels on operation conditions. The results of the isochronal annealing experiment demonstrate that the defects responsible for RTS behavior are the cluster defects able to enhance thermal generation through Shockley-Read-Hall (SRH) mechanism.

An Adaptive Offset Tracking Method with SAR Images for Landslide Displacement Monitoring

With the development of high-resolution Synthetic Aperture Radar (SAR) systems, researchers are increasingly paying attention to the application of SAR offset tracking methods in ground deformation estimation. The traditional normalized cross correlation (NCC) tracking method is based on regular matching windows. For areas with different moving characteristics, especially the landslide boundary areas, the NCC method will produce incorrect results. This is because in landslide boundary areas, the pixels of the regular matching window include two or more types of moving characteristics: some pixels with large displacement, and others with small or no displacement. These two kinds of pixels are uncorrelated, which result in inaccurate estimations. This paper proposes a new offset tracking method with SAR images based on the adaptive matching window to improve the accuracy of landslide displacement estimation. The proposed method generates an adaptive matching window that only contains pixels with similar moving characteristics. Three SAR images acquired by the Jet Propulsion Laboratory’s Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) system are selected to estimate the surface deformation of the Slumgullion landslide located in the southwestern Colorado, USA. The results show that the proposed method has higher accuracy than the traditional NCC method, especially in landslide boundary areas. Furthermore, it can obtain more detailed displacement information in landslide boundary areas.

Adaptive method for the detection of infrared small target

Background suppression is an important problem in infrared small target detection. The two-dimensional least mean square (TDLMS) filter is a widely used method, but its performance will decline when targets are embedded in a complex cluttered background. To fill the gap, variable step-size TDLMS, the neighborhood analysis technique, and the edge-directional TDLMS filter are developed but still cannot achieve a satisfying performance. Here, an adaptive method for background suppression is proposed. According to different characteristics of the pixels in homogeneous/target regions and inhomogeneous regions, two basic filters are first designed. Then a fuzzy edge estimation factor is introduced to combine them into a uniform framework, in which the two basic filters can be switched automatically to fit different kinds of pixels. Finally, a new mechanism to update and propagate the coefficients of the prediction window is constructed. It makes sure that the adaptive method works smoothly and reveals a potential to be implemented in parallel. The experimental results demonstrate that the proposed method achieves significant improvement in background suppression and detection performance.

Effect of Pixel Shape on Fluid Motion in an Electrofluidic Display

High-efficiency control of the motion of the oil film plays a critical role in optimizing electrofluidic display (EFD) technology. In this paper we focus on studying the effect of different pixel shapes on kinetics of electrofluidic. Four different kinds of pixels including square pixel, rectangle pixel, trapezoid pixel, and triangle pixel were designed and discussed. The electro-optic characteristics and the switching dynamics of four electrofluidic pixel arrays were studied respectively. The results indicate that the reduction of the inscribed circle of pixel grid leads to an increase in the threshold voltage. When the geometry of pixels is asymmetric, the oil film prefers to move towards the small angle which can obtain uniform motion of the oil. Moreover, it also affects the speed of the moving oil/water interface to some extent. In all the geometry design of the pixel provides useful directions for improving the electrofluidic display technology.

A dynamic range extension scheme applied to a TDI CMOS image sensor

A dynamic range extension scheme applied to a time delay integration (TDI) CMOS image sensor (CIS) is presented. Two types of pixels with higher and lower conversion gain are adopted in the pixel array, which are suitable for capturing images in low and high illumination respectively. By fusing the two kinds of pixels' output signals in the process of TDI accumulation, a high dynamic range image can be achieved. Compared with the traditional multiple integration technique, no photoelectrons generated during the exposure time are discarded by the reset operation, and thus a higher level of signal-to-noise ratio (SNR) can be retained. A prototype chip with an 8 × 8 pixel array is implemented in a 0.18 μm CIS process, and the pixel size is 15 × 15 μm2. Test results show that a 76 dB dynamic range can be achieved in 8-stage TDI mode, when the SNR boost can reach 7.26 dB at 90.8 lux.

Entropic image thresholding based on GLGM histogram

We propose GLGM (gray-level & gradient-magnitude) histogram as a novel image histogram for thresholding. GLGM histogram explicitly captures the gray level occurrence probability and spatial distribution property simultaneously. Different from previous histograms that also consider the spatial information, GLGM histogram employs the Fibonacci quantized gradient magnitude to characterize spatial information effectively. In this paper, it is applied to entropic image thresholding. For threshold selection, we define a new spatial property weighting function to depict the roles played by different kinds of pixels. The experiments demonstrate the effectiveness and robustness of our thresholding approach, containing wide range comparisons with the well established thresholding methods.

Sunyaev–Zel’dovich effect or not? Detecting the main foreground effect of most galaxy clusters

Abstract Galaxy clusters are the most massive objects in the Universe and comprise a high-temperature intracluster medium of about 107 K, believed to offer a main foreground effect for cosmic microwave background (CMB) data in the form of the thermal Sunyaev–Zel’dovich (SZ) effect. This assumption has been confirmed by SZ signal detection in hundreds of clusters but, in comparison with the huge numbers of clusters within optically selected samples from Sloan Digital Sky Survey (SDSS) data, this only accounts for a few per cent of clusters. Here we introduce a model-independent new method to confirm the assumption that most galaxy clusters can offer the thermal SZ signal as their main foreground effect. For the Wilkinson Microwave Anisotropy Probe (WMAP) seven-year data (and a given galaxy cluster sample), we introduced a parameter d1 as the nearest-neighbour cluster angular distance of each pixel, then we classified data pixels as ‘to be’ (d1 → 0 case) or ‘not to be’ (d1 large enough) affected by the sample clusters. By comparing the statistical results of these two kinds of pixels, we can see how the sample clusters affect the CMB data directly. We find that the Planck Early Sunyaev–Zel’dovich (ESZ) sample and X-ray samples (∼102 clusters) can lead to obvious temperature depression in the WMAP seven-year data, which confirms the SZ effect prediction. However, each optically selected sample (>104 clusters) shows an opposite result: the mean temperature rises to about 10 μK. This unexpected qualitative scenario implies that the main foreground effect of most clusters is not always the expected SZ effect. This may be the reason why the SZ signal detection result is lower than expected from the model.

Image denoising using 2-D FIR filters designed with DEPSO

Digital images are often corrupted by additive noises during transmission. Thus, how to alleviate noise as much as possible has received concerns for decades. In this paper, we present a simple denoising method based on two dimensional (2-D) finite impulse response (FIR) filtering, where by differential evolution particle swarm optimization (DEPSO) algorithm, five two dimensional finite impulse response filters are designed to filter different kinds of pixels. Comprised by differential evolution algorithm and particle swarm optimization algorithm, differential evolution particle swarm optimization algorithm is effective and robust, which helps to yield better denoise performance. And computer simulation demonstrates that the proposed method is superior to the conventional lowpass filtering method, as well as the modern bilateral filtering and stochastic denoising method.

A half wave retarder made of bilayer subwavelength metallic apertures

We demonstrate a half wave plate whose principle of operation is based on the strong evanescent field coupling between two metal layers with arrays of subwavelength slits. The device is divided into two kinds of pixels in which the slits are oriented in orthogonal directions. By tuning the phase delay of the transmitted light through the lateral displacement between the top and bottom layers, the polarization of linearly polarized light at 1.55 μm can be rotated by up to 90°. The polarization extinction ratio of the transmitted light exceeds 22 dB.

A New Spatiotemporal CMOS Imager With Analog Accumulation Capability for Nanosecond Low-Power Pulse Detections

High-speed cameras use the interesting performances of CMOS imagers that offer advantages in on-chip functionalities, system power reduction, cost, and miniaturization. The FAst MOS Imager (FAMOSI) project consists in reproducing the streak camera functionality with a CMOS imager. In this paper, a new imager called FAMOSI 2, which implements an electronic shutter and analog accumulation capabilities inside the pixel, is presented. With this kind of pixel and the new architecture for controlling the integration, FAMOSI 2 can work in repetitive mode for low light power and in single shot mode for higher light power. This repetitive mode utilizes an analog accumulation to improve the sensitivity of the system with a standard n-well/p <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sub </sub> photodiode. The characterization has been realized in single shot mode to optimize the accumulation mode. The prototype has been fabricated in the Austriamicrosystems 0.35-mum CMOS process. The chip is composed of 64 columns times 64 rows of pixels. The pixels have a size of 20 mum times 20 mum and a fill factor of 47%