Camera pixel for coherent detection of modulated light

A CMOS pixel with local processing suitable for use in a modulated light camera is described. The pixel was designed to detect sinusoidally modulated light within the frequency range of 500 kHz-25 MHz. It consists of a photodiode, a transimpedance amplifier, a mixer and an active 150 Hz bandpass filter. It is a prototype design capable of further size reduction suitable for tiling into an array for imaging purposes. This allows the modulated light component of a frequency far in excess of the frame rate to be detected at the pixel level.     

Quad-phase synchronous light detection with 64 X 64 CMOS modulated light camera

A scalable 64times64 array of feedback buffered photodiodes with column level demodulation circuitry has been fabricated in a 0.35 mum CMOS process. The camera provides two-dimensional phase-sensitive imaging on a line-scan basis using 64 independent quad-phase demodulation channels. Using four phases suppresses even harmonics, enabling the array to be used for heterodyne demodulation.     

利用机器视觉的检测液晶屏幕坏点分析

本文针对液晶屏幕像素坏点检测当中出现的问题,根据机器视觉原理,利用HALCON以及VS2010作为开发平台,设计了液晶屏幕像素坏点自动检测系统.     

Photoresponse analysis and pixel shape optimization for CMOS active pixel sensors

In this work, a semi-analytical model, based on a thorough analysis of experimental data, is developed for photoresponse estimation of a photodiode-based CMOS active pixel sensor (APS). The model covers the substrate diffusion effect together with the influence of the photodiode active-area geometrical shape and size. It describes the pixel response dependence on integration photocarriers and conversion gain and demonstrates that the tradeoff between these two conflicting factors gives an optimum geometry enabling extraction of maximum photoresponse. The parameter dependence on the process and design data and the degree of accuracy for the photoresponse modeling are discussed. Comparison of the derived expression with the measurement results obtained from a 256/spl times/256 CMOS APS image sensor fabricated via HP in a standard 0.5-/spl mu/m CMOS process exhibits excellent agreement. The simplicity and the accuracy of the model make it a suitable candidate for implementation in photoresponse simulation of CMOS photodiode arrays.     

Chromatic dispersion induced distortion of modulated monochromatic light employing direct detection

The spectrum of an intensity modulated (IM) and a combined intensity-frequency modulated (IM-FM) monochromatic light source has been generated. The amplitudes of the modulated carrier and the first three pairs of sidebands are plotted showing the influence of IM on an FM signal. The effects of first order chromatic dispersion on the baseband amplitude response and harmonic distortion are determined. The manner in which modulation type and depth, modulating frequency, wavelength, and fiber length alter harmonic distortion is presented. Numerical examples giving the amplitude response of a single-mode fiber system as well as the magnitude of the second- and third-harmonic distortion caused by chromatic dispersion are presented. Based on this material, the limits placed on analog transmission due to chromatic dispersion may be assessed.     

基于调制光源的八通道光电脉搏波检测系统

为了获取多波长的指端光电脉搏波信号来进行脉搏波特征分析,利用STM32F103ZE嵌入式平台设计了基于八波长激光调制光源的脉搏波检测系统.系统光源是由STM32控制的八波长激光组成的调制光源,再由光电二极管构成光电转换电路将光信号转换为易处理的电信号.系统结合巴特沃斯高通滤波电路与切比雪夫低通滤波电路的滤波特性设计了由...     

Dual-phase synchronous light detection with 64/spl times/64 CMOS modulated light camera

A scalable sensor for wide field detection (imaging) of low contrast amplitude-modulated light has been fabricated in a standard CMOS process. The sensor has a randomly addressable array of 64/spl times/64 feedback buffered photodiodes. Any row of the photodiode array can be connected to 64 independent dual-phase lock-in detection channels allowing two-dimensional phase sensitive imaging without mechanical scanning.     

Performance of a finite capacity asynchronous multiplexer with modulated input

In this paper, a finite capacity multiplexer in ATM environments with modulated deterministic input sources is investigated. We consider three cases of input traffic: (1) a fixed number of deterministic cell-generating sources, (2) a fixed number of sources where each source is modulated by an ON-OFF process, and (3) a variable number of ON-OFF sources, modulated by a call arrival process in conjunction with a connection admission control scheme. The main performance measures in this study are the cell and call blocking probabilities. For case (1), we give a tight upper bound for the transient phase of the state process to reach stationary conditions. The state probabilities and the corresponding cell blocking probability are determined by means of an exact analysis. For cases (2) and (3), where we deal with more complex input traffic, the compound state process and the overall cell blocking probability are analyzed using a quasi-stationary approximation technique. This approximation is validated by means of simulations. The analysis presented is shown to be able to give reasonably accurate approximate results for ATM-multiplexer performance for cases in which conventional simulation and analytic methods already approach computing time and complexity boundaries.     

一种HEVC整像素运动估计优化算法

对HEVC整像素运动估计算法进行优化,目的是在保持编码视频压缩后码流率和解码视频图像质量基本不变的同时,降低编码耗时。首先,统计了不同视频序列的进行帧间预测时整像素运动估计的搜索步长的分布。进而根据统计结果,改进了不同搜索步长下的分支搜索模板。同时调整了整像素运动估计的提前终止条件。最终比较了测试视频序列优化前后编码输出的YUV分量、码流和耗时。实验结果表明,对于class E(1 920×1 080)视频序列,在编码后视频质量的客观值(YUV分量)最多下降0.182 2 d B,比特率最多上升0.40%,耗时最少下降1.25%。     

Coded asynchronous CDMA and its efficient detection

In this paper, receiver design and performance analysis for coded asynchronous code-division multiple access (CDMA) systems is considered. The receiver front-end consists of the near-far resistant multiuser detector known as the projection receiver (PR). The PR performs multiple-access interference resolution and is followed by error-control decoding. The output of the projection receiver yields the appropriate metric (i.e., soft information) for decoding of the coded sequences. An expression for the metric is derived that allows the use of a standard sequence decoder (e.g., Viterbi algorithm, M-algorithm) for the error-control code. It is then shown that the metric computer has an elegant adaptive implementation based on an extension of the familiar recursive least squares (RLS) algorithm. The adaptive PR operates on a single sample per chip and achieves a performance virtually identical to the algebraic PR, but with significantly less complexity. The receiver performance is studied for CDMA systems with fixed and random spreading sequences, and theoretical performance degradations with regard to the single-user bound are derived. The near-far resistance of the PR is also proven, and demonstrated by simulation     

红外线阵探测器盲元定位与补偿

为减少红外线列探测器的条纹噪声与非均匀性噪声受环境温度和探测器工作时间的影响,提出了一种处理盲元的综合算法.首先依据探测器最终数据输出来检测盲元通道;然后依据通道位置与数量调整偏移量值,并根据探测器的阵列结构特点,对4806个像元完成精确的盲元定位;最后完成对含有盲元通道的非均匀校正.以FPGA处理模块为核心,完成了红外探测器实时采集与处理.图像校正效果良好,具有良好的实时性和可移植性.     

红外探测器盲元检测及评价

盲元严重影响红外制导武器的成像质量和系统性能。针对目前滤波类检测算法无法准确检测连续盲元的问题,本文对基于场景的时域平均野值提取的盲元检测算法进行了改进,对滤波窗口下的盲元分布形式进行了讨论,对连续盲元提出基于时域平均和空域均值野值提取的盲元检测算法,实现了盲元位置的确定。通过仿真实验对比发现,本文检测算法对连续盲元具有更低的误检率和漏检率;然后本文提出一种红外探测器盲元的测试评价方法,通过对样本图像进行分析计算,根据罗曼诺夫斯基准则的思想确定评价参数与评价法则,作为判断红外制导武器成像探测器能否正常工作的依据。测试方法简便快捷,有较高的准确度。     

一种提高红外焦平面阵列盲元检测精度的方法

针对红外成像系统在条纹噪声和非均匀性噪声干扰下盲元检测精度差的问题,提出了一种将小波滤波和“3σ”原则相结合的盲元检测新方法。首先用小波变换对含有条纹噪声和非均匀性噪声的图像进行预处理,再用“3σ”原则对其进行盲元检测。仿真结果表明该方法消除了噪声对盲元检测的影响,有效地解决了“3σ”原则检测精度低的问题。     

引导滤波与像素重分布的低照图像增强

针对现有的图像增强方法存在欠增强、过增强以及对比度低等缺陷,提出了一种引导滤波与像素重分布的低照图像增强算法。方法充分利用引导滤波的边缘保持特性,用引导滤波对光照图像进行估计,然后对光照图像的像素进行相对均匀重分布,全面提升光照图像的亮度与对比度。最后将像素重分布增强处理后的光照图像和反射图像作反Retinex变换,得到最后的增强图像。实验结果证明,相对现有的图像增强方法,本文方法具有更优的图像增强效果,图像对比度与纹理结构更清晰。     

基于小波变换与像素灰度值变化的点目标探测

当成像系统与反舰导弹的运动方向在同一条直线上时,无法采用基于运动轨迹分析的时间滤波算法。针对这一问题,提出了一种基于小波变换的空间滤波与基于像素灰度值变化检测的时间滤波混合算法进行点目标探测。试验用的图像采用实际的背景图像与模拟的点目标信号相结合。试验表明该算法具有良好的探测精度和灵敏度以及低虚警率。     

像素binning技术在高速弱点目标探测中的应用研究

弱点目标探测系统要求系统具备高的探测灵敏度和高空间分辨率,实现弱点目标的稳定探测、目标的精准定位以及多目标伴飞时的精细分辨。光电跟瞄系统一般分为目标捕获和目标跟踪两个阶段。在目标捕获阶段,由于速度估计偏差,目标高速飞行的同时,若采用长积分时间进行探测,易出现目标能量跨像元的现象,难以实现目标探测信噪比的提升。为了解决目标高速运动导致的探测灵敏度降低的问题,本文提出了一种基于滑窗像素binning的高速弱点目标探测跟踪技术。像素binning模式提高了初始捕获阶段的探测灵敏度和探测稳定性,当跟瞄系统完成目标的稳定跟踪时,可以采用长积分时间和高分辨率模式完成目标的高灵敏度和高分辨率探测。本文对像素binning模式的信噪比增强效果进行了分析。分析表明,像素binning模式有利于提高高速弱点目标探测的信噪比和探测稳定性。     

基于边缘检测和像素分类的可逆数据隐藏

为了提高嵌入算法的整体性能,提出一种基于边缘检测和像素分类的灰度图像可逆数据隐藏算法。算法按嵌入容量优先原则自适应地选择最佳阈值提取图像边缘,并根据边缘信息和指定的图像质量控制因子将像素分为平滑、弱边缘和强边缘像素3类。对平滑像素,通过增加嵌入强度的方法提高嵌入容量,预测误差直方图平移2位;对弱边缘像素,像素值最大修改量为1,从而保证图像含密质量;强边缘像素的像素值保持不变,进一步提高含密图像质量。实验结果表明,本文算法在保证图像质量的同时有效提高嵌入容量,算法的整体性能优于其它同类算法。     

Multiuser detection of asynchronous CDMA with frequency offset

This article presents a near-far resistant detection scheme for asynchronous code-division multiple access with frequency offset. Based on a one-shot technique and Taylor expansion, a zeroth-order and a first-order one-shot linear decorrelating detector (LDD) are proposed. The zeroth-order LDD has simple architecture but suffers performance degradation for large frequency offset. The first-order one-shot LDD, with increased complexity, has very good near-far resistant property even for large frequency offset. Two versions of the first-order one-shot LDD are investigated according to different Taylor expansion approaches. The feasibility of the proposed detectors is demonstrated by computer simulations     

红外线列探测器盲元检测和补偿算法研究

为提高红外线列探测器盲元检测精度,针对红外线列探测器的响应特点,设计了适用于本系统的盲元检测和补偿方案,根据本系统红外线列探测器的特点,提出了一种在无标定光照情况下的盲元检测方法,通过仿真认证,设计方案具有很高的盲元检测精度,能较理想地对盲元进行补偿.