Simulation study of energy resolution with changing pixel size for radon monitor based on Topmetal-Ⅱ^- TPC

In this paper, we study how pixel size influences energy resolution for a proposed pixelated detector—a high sensitivity, low cost, and real-time radon monitor based on a Topmetal-Ⅱ^- time projection chamber(TPC). This monitor was designed to improve spatial resolution for detecting radon alpha particles using Topmetal-Ⅱ^- sensors assembled by a 0.35 lm CMOS integrated circuit process.Owing to concerns that small pixel size might have the side effect of worsening energy resolution due to lower signalto-noise ratio, a Geant4-based simulation was used to investigate the dependence of energy resolution on pixel sizes ranging from 60 to 600 lm. A non-monotonic trend in this region shows the combined effect of pixel size and threshold on pixels, analyzed by introducing an empirical expression. Pixel noise contributes 50 keV full-width at half-maximum energy resolution for 400 lm pixel size at 1–4σ threshold that is comparable to the energy resolution caused by energy fluctuations in the TPC ionization process( ~20 keV). The total energy resolution after combining both factors is estimated to be 54 keV for a pixel size of 400 lm at 1–4σ threshold. The analysis presented in this paper would help choosing suitable pixel size for future pixelated detectors.

Fast Approaches for Sub-pixel Precision Variable Block Size Motion Estimation

The new features of H. 264 video coding standard make the motion estimation module much more time consuming than before. Especially, the motion search is required for each of the 4 modes for inter prediction. In order to reduce the computational complexity, we analyze the statistics of results of motion estimation, such as the continuity of best modes of blocks in successive frames and the chance to give up a sub-partition mode （smaller than 16 × 16） after integer-pixel motion estimation, from which we suggest to make mode prediction based on the motion information of the previous frame and skip sub-pixel motion estimation in subpartition mode selectively. According to the experimental result, the proposed algorithm can save 75 % of the computational time with a slight degradation （0.03 dB） on PSNR compared with the pseudocode of fast search motion estimation in JM12.2.

Development of small pixel HgCdTe infrared detectors

After approximately half a century of development, HgCdTe infrared detectors have become the first choice for high performance infrared detectors, which are widely used in various industry sectors, including military tracking, military reconnaissance, infrared guidance, infrared warning, weather forecasting, and resource detection. Further development in infrared applications requires future HgCdTe infrared detectors to exhibit features such as larger focal plane array format and thus higher imaging resolution. An effective approach to develop HgCdTe infrared detectors with a larger array format size is to develop the small pixel technology. In this article, we present a review on the developmental history and current status of small pixel technology for HgCdTe infrared detectors, as well as the main challenges and potential solutions in developing this technology. It is predicted that the pixel size of long-wave HgCdTe infrared detectors can be reduced to5 μm, while that of mid-wave HgCdTe infrared detectors can be reduced to 3 μm. Although significant progress has been made in this area, the development of small pixel technology for HgCdTe infrared detectors still faces significant challenges such as flip-chip bonding, interconnection, and charge processing capacity of readout circuits. Various approaches have been proposed to address these challenges, including three-dimensional stacking integration and readout circuits based on microelectromechanical systems.

Decoding brain responses to pixelized images in the primary visual cortex: implications for visual cortical prostheses

Visual cortical prostheses have the potential to restore partial vision. Still limited by the low-resolution visual percepts provided by visual cortical prostheses, implant wearers can currently only ＂see＂ pixelized images, and how to obtain the specific brain responses to different pixelized images in the primary visual cortex（the implant area） is still unknown. We conducted a functional magnetic resonance imaging experiment on normal human participants to investigate the brain activation patterns in response to 18 different pixelized images. There were 100 voxels in the brain activation pattern that were selected from the primary visual cortex, and voxel size was 4 mm × 4 mm × 4 mm. Multi-voxel pattern analysis was used to test if these 18 different brain activation patterns were specific. We chose a Linear Support Vector Machine（LSVM） as the classifier in this study. The results showed that the classification accuracies of different brain activation patterns were significantly above chance level, which suggests that the classifier can successfully distinguish the brain activation patterns. Our results suggest that the specific brain activation patterns to different pixelized images can be obtained in the primary visual cortex using a 4 mm × 4 mm × 4 mm voxel size and a 100-voxel pattern.

基于机器视觉的木窗双端铣削加工尺寸测量方法

木窗是一种以木材或木质复合材料为主要构件的门窗产品,具有良好的生态性能和美观效果,适用于多种建筑形式和风格,其中木窗尺寸是衡量木窗加工是否合格的重要指标。对于传统木窗双端铣削加工中人工测量尺寸方式存在的精度低、效率低等问题,提出一种基于机器视觉的木窗双端铣削加工尺寸测量方法,以期提高尺寸测量精度及加工效率。该方法针对木窗厚度引起的透视效应,提出一种物平面提升法,以消除透视投影带来的误差。首先对木窗图像采取灰度化、平滑去噪、图像增强及轮廓分割等举措,完成图像预处理,提取出木窗内外轮廓区域。对轮廓区域应用Canny算子获取木窗像素级轮廓。通过优化的Zernike矩亚像素边缘提取算法对木窗像素级边缘进行更精确的定位,得到亚像素级轮廓坐标。通过最小二乘法联合RANSAC算法对亚像素轮廓坐标进行拟合,得到拟合轮廓及角点坐标,并使用透视矫正模型计算出木窗尺寸。实验利用3种厚度规格相同但尺寸不同的松木材质矩形木窗,分别测量其内框和外框的边框尺寸及对角线尺寸,并与对应的实际物理尺寸对比,验证了所提木窗尺寸测量方法的检测精度。研究结果表明,所提方法与实际物理尺寸值相比,其绝对误差范围在±0.12 mm之内,相对误差在±0.1%之内,且效率及精度高,可以满足对木窗的在线尺寸检测。

基于视觉原理的链轮尺寸测量方法研究

针对现有的链轮端面几何参数测量方法存在效率及测量精度低等问题,提出一种基于视觉原理的链轮端面几何参数测量方法。首先,利用Zernike矩的亚像素边缘检测提取链轮内外轮廓,对内轮廓采用Hough变换获得中心点坐标与中心孔半径;其次,在外轮廓作一辅助圆,通过像素点序列计数算法得到齿数;然后,根据链轮齿廓的形状特征,提出一种改进的局部半径域算法提取每段齿廓的齿顶、齿根点,再通过最小二乘法拟合像素点得到齿顶圆、齿根圆直径;最后,采用最小二乘法拟合链轮键槽边缘直线得到键槽尺寸。对2种不同规格的链轮分别进行10次重复性测量。实验结果表明,链轮端面几何参数的测量误差均小于40μm,相对误差均在0.4%之内,能满足高精度的自动测量需求。

电线电缆绝缘横截面积测算方法研究

为了分析评估标准中规定的检测线缆绝缘橫截面积的方法的准确性,提出了一种采用像素面积插值法测量绝缘横截面积的方法。通过对标准中的方法和像素面积法得到的数据进行比对分析,分别给出了实心导体、软导体2种不同类型的导体挤出后形成的横截面积的测量差异,并分析了差异形成的原因。像素面积法能够更加方便、快捷、高效地检测线缆厚度、截面积,切实提高线缆的绝缘尺寸、橫截面积测量的准确性和测量过程的自动化率,具有一定的实用价值。

精密器件尺寸的图像测量算法设计与实现

为了实现精密器件的无接触精密快速测量,本文提出了一种利用精密器件图像对进行尺寸测量的方法。根据不同的参照物的比例关系及采用不同倍率的图像预处理测量算法,实现两点的距离、测量斜率、角度、半径、曲线弧度的测量。实验的结果表明,本文提出的图像测量算法具有灵活性高、测量结果准确的优点。

CCD图像传感器发展与应用

主要介绍了线阵CCD、面阵CCD、帧转移CCD、ITO-CCD和电子倍增CCD等图像传感器的发展现状。以CMOS器件作为比较,探讨和研究CCD图像传感器的应用领域以及未来发展趋势。

机载海洋改进型Dyson高光谱成像仪的研制

针对海洋环境、海洋水色等领域的发展需要,设计了一种适于机载的宽视场、大相对孔径的改进型Dyson光谱成像系统。根据海洋环境污染的光学特性,利用不同目标反照率值估算目标信号的信噪比,将高光谱成像仪的工作波段扩宽至紫外波段;使用大像元尺寸的探测器、大相对孔径的成像系统来满足对海洋目标弱信号的识别,同时通过降低积分时间来避免近海岸沙滩信号过强引起的探测器饱和。该光谱仪的工作波段为0.32~1.05μm、相对孔径为f/1.8、像元尺寸为24μm×24μm,通过加入弯月形的矫正镜避免了狭缝、探测器、滤光片和单透镜相互之间产生干涉。设计结果表明,整个光学系统各波长的传递函数均大于0.83,谱线弯曲和谱带弯曲均小于像元尺寸的4%。所设计成像光谱仪系统适用于海洋环境污染,尤其是海洋溢油污染的监测。

IC晶片关键尺寸标定的新方法研究

提出了一种基于标准件法的二次标定法,实现了对微距尺寸的高速高精度测量。该方法经过实验测量数据的分析对比,表明比标准件法测量精度有明显提高,满足了IC晶片线宽测量的精度要求。

亚像素数字散斑相关测量中计算窗口的选择

提出了一种亚像素数字散斑相关测量计算窗口的选择方法。采用模拟散斑图像,利用亚像素数字散斑相关测量中的相关系数插值法、拟合法及梯度算法原理,研究了计算窗口大小对这三种计算方法的测量精度和计算效率的影响,得出了不同亚像素精度要求下,可选择的计算方法及其最佳计算窗口。研究结果表明,测量精度越高,所需的计算窗口越大,选择合适的计算窗口可以提高测量精度和效率。

一种线阵CCD融合光栅尺的高精度尺寸测量新方法研究

为了解决数字图像亚像素级高精度尺寸检测问题,采用了基于人工神经网络的线阵相机镜头畸变矫正方法,比传统的多项式拟合法矫正精度高且操作简便;提出了将光栅尺融入线阵相机扫描机构的新方法,利用高精度光栅尺测位移信号触发线阵CCD图像采集动作,精确获取线阵相机扫描目标的亚像素级图像。实验证明,新的测量技术可在对运动系统要求不高的情况下获取高精度图像,图像检测精度可以达到1μm。

CCD像元尺寸对移相干涉术相位测量精度的影响

针对移相干涉术中CCD探测器采集高密度干涉条纹的过程,对影响相位测量精度的主要因素进行了理论分析和仿真研究.结果表明,随着CCD像元尺寸及随机噪声标准差的增大,CCD探测得到的时域光强信号信噪比降低,引入的相位测量误差也增大.当信噪比约高于24时,相位测量精度可优于π/50rad,折合成光程差即优于λ/100,为后续研究扩展移相干涉术的测量范围提供了理论上的定量依据.

一种轴类零件边缘精确定位方法

针对目前的边缘检测算法存在定位精度低、处理速度慢、抗噪性能差等缺陷,提出了一种轴类零件尺寸检测的图像边缘高精度定位方法。该方法采用改进的自适应中值滤波算法、改进的Kirsch算子和在图像边缘灰度梯度方向上进行二次函数逼近高斯曲线拟合方法,实现了图像边缘亚像素高精度定位,提高了尺寸检测精度。通过对气门尺寸的计算机视觉检测实际应用,证明提出的算法精确且稳定,满足高精度视觉检测要求。

像元尺寸对空间光学探测系统性能的影响

针对空间光学探测系统的组成和特点,采用调制传递函数(MTF)作为系统性能指标,通过建立光学系统、探测器系统、离焦和像移调制传递函数模型,仿真分析了像元尺寸对系统成像性能的影响。结果表明,随着像元尺寸减小,探测器系统MTF值增大,光学系统、离焦、像移等的MTF值都变小,从而为像元尺寸的确定提供了参考依据。

改进的自适应中值滤波算法及其应用

针对自适应中值滤波在窗口迭代过程中存在像素点重复参与运算导致算法复杂度较高的问题,提出了一种改进的中值滤波算法.首先依据有效像素点与窗口中心点间的坐标距离来快速确定最佳滤波窗口尺寸,避免了窗口迭代造成的像素点重复排序;之后对窗口内的有效像素点进行取中值操作,有效削弱了噪声点的干扰,进一步提升了图像滤波的质量.经实验验证,与自适应中值滤波算法比较,复杂度显著降低,峰值信噪比(peak signal to noise ratio,PSNR)值平均提高10 d B左右.和同类文献比较在算法复杂度和图像降噪效果间做出了一个较佳的权衡.最后将该算法应用于Kinect深度图降噪上获得了不错的效果.

基于轨迹图像喷嘴液滴粒径和速度测量系统构建

为了对烟草制丝线增湿、加料与加香工序中双介质喷嘴的雾化状态进行表征,研究了基于粒子轨迹图像的喷嘴雾化图像测量方法,开发了双介质喷嘴雾化液滴粒径和速度测试平台。结果表明:①采用矩阵亚像素的图像处理方法,解决了蒸汽引射液体雾化时,蒸汽介质光强烈散射而影响液滴图像提取的问题;②利用开发的图像自动采集计算软件,对图像逐帧连续采集和个数统计可知,当雾滴群中液滴的样本个数大于5000时,液滴的粒径和速度均呈正态分布;③基于粒子轨迹图像液滴粒径和速度分布测试方法可实现对蒸汽、压缩空气引射料液时喷嘴雾化特征的表征,满足工业对双介质喷嘴的点检、选型以及工况参数优化的要求。

CCD光斑质心算法的误差分析

文章建立了CCD噪声和像元尺寸对质心算法影响的误差模型。模型表明,当CCD上光斑的束腰ω<0.1个像元时,质心算法的误差大于0.28个像元;当束腰ω>0.5个像元时,像元尺寸对灰度质心算法的影响可忽略不计,影响质心算法的主要因素是CCD随机噪声误差。在ω>0.5个像元的前提下,光斑尺寸越小,质心算法的精度越高。实验与理论分析结果一致,证明了该误差模型的正确性。

基于遗传算法的Canny边缘检测算子在配药机器人中的应用

为了尽可能降低噪声的影响和保留图像的边缘信息,以确保配药机器人的机械手能快速准确地抓取药瓶完成整个配药过程,结合了遗传算法和Canny边缘检测算子的优点,首先采用半像素插值的方法将3×3模板扩展成5×5模板,再利用图像梯度方差作为判据对图像进行四叉树分块,然后对每个子块采用二次寻优遗传算法再反复迭代求出最佳阈值,最后利用该阈值来对边缘进行提取。实验结果表明:与传统的算法相比,该算法的检测效果更好,能有效地减少假边缘点出现的概率,保证了机械手的抓取动作顺利进行。