打印机几何误差分析与测量

在利用打印的网格图形获取书籍扫描图像的畸变参数时,网格图形的误差将影响所确定的畸变参数的精度,从而影响书籍扫描图像的畸变校正精度.为评价其影响程度,对打印机的几何误差进行了测量与分析.提出了一种基于图像处理的像素间距误差测量方法.通过编程,按照MM_TEXT映射模式打印图形,可消除打印时的量化误差.利用扫描仪对打印图形进行测量,在消除了扫描仪本身误差的影响之后,得到了较高精度的测量结果.实验研究了打印机像素间距误差与打印位置的关系.     

一种OMR卡片信息的提取和识别方法

提出了一种基于图像投影的记分卡识别算法，与扫描装置配合可实现高效准确的卡片信息解读，不仅能达到无差错识别，而且容易实现。系统以扫描仪获取的图像为输入，通过横向和纵向投影实现定位和信息提取。通过搜索纵向投影最大标准差所对应的方向实现角度校正，克服了扫描误差引起图像偏斜的问题。     

扫描仪误差校正的应用研究

为了解决扫描仪图像畸变问题,提出用标定板对扫描仪进行误差标定的方法。该方法在对产生畸变误差的原因和特点进行分析的基础上,将从扫描仪获取的图像进行灰度变化和细化处理,通过MFC编程获取标定板上圆心的实际坐标并存储于结构体中,然后将其与标定板的理论圆心坐标进行对比分析,得到扫描仪误差的规律,最后根据误差分布规律,采用分段系数补偿的方法,对扫描图像进行标定。实验结果表明经过误差标定后能够较好地消除图像的畸变误差。     

书籍扫描图像几何畸变校正

提出一种图像扫描技术,解决书籍扫描时图像背景灰度不均匀、线性几何畸变、以及非线性几何畸变等问题。这个方法不依赖扫描仪的参数。通过对图像的预处理,选取适当的采样窗口,基于直方图背景分析导出背景灰度因子,校正背景灰度不均。提出了一种线性几何畸变校正算法,用横向数值校正算法解决了非线性畸变的问题。     

扫描仪误差分析

为了解决用扫描仪测量微生物抑菌圈直径时误差较大问题,对扫描仪误差进行了分析。扫描仪误差包括像素间距误差、像素间距横纵比误差及扫描起点误差等。提出用椭圆拟合法对扫描仪误差进行测量。通过V isual C++6.0编程,研究了扫描仪误差与扫描时间、扫描位置、扫描分辨力等因素的关系,发现了一些规律,为编程实现针对扫描条件的测量结果自动修正打下了基础。     

敦煌派出特种兵

清华紫光集团近期推出了一款针对高档商业办公市场的敦煌 D2000型专业扫描仪,无论对于银行、部队、证券、以及政府等办公服务,还是研究机构如医疗卫生、地理信息、航空航天、气象、冶金等各个领域,敦煌 D2000型扫描仪都可应用。作为面对高档商业应用的专业级扫描仪,敦煌 D2000型扫描仪具有1200×2400dpi 光学分辨率、9600dpi插值分辨率、42位的色彩深度、14位灰度级。敦煌 D2000扫描仪除了具有专业扫描仪应具备的基本技术指标之外,还采用了智能硬件去网技术、自动标准化色彩校正以及增强色彩还原性等多项技术,以确保扫描品质。D2000扫描仪实现了对扫描图像的精细加工处理,使扫描效果得到了进一步提高。其智能硬件去网技术则成功地解决了扫描图像可能     

扫描仪图像质量探秘

目前,彩色印前系统的蓬勃发展,带动了平台式扫描仪的广泛的应用,用户最关心的问题是:如何辨别同一档次、不同品牌的扫描仪图像质量相对的优劣呢? 检查扫描图像质量的方法 影响扫描图像质量的因素很多,诸如分辨率设置、色彩校正、图像增强、文件格式、文件储存、系统资源等,但检查图像的质量主要从     

在Delphi中利用“Kodak图像扫描控件“控制扫描仪

在编写图像处理程序时,有时需要加入图像扫描功能,通过控制扫描仪获得图像并对其进行进一步的处理。要实现这一功能其实并不困难,利用“Kodak图像扫描控件”就可以达到目的。本文通过一个简单的图像扫描处理程序,介绍在Delphi中利用图像扫描控件控制扫描仪的     

书籍图像背景灰度非线性畸变校正

提出一种图像扫描技术,解决书籍扫描时图像背景灰度不均匀,并呈现非线性畸变情况。这个方法不依赖扫描仪的参数。通过对图像的预处理,选取适当的采样窗口,用函数曲线逼近拟合背景灰度因子分布,来消除跳变误差,或重新定义背景灰度采样窗口和背景灰度估计。     

新品介绍

惠普公司于8月宣布推出HP ScanJet 610012专业系列扫描仪。这种平板式扫描仪具有领先的色彩与灰度级处理能力,该产品将于9月以后在中国上市。 ScanJet 6100C专业系列扫描仪采用惠普领先的智能扫描技术,图像扫描质量相当优秀。由于采用了35mmHP ScanJet幻灯片适配器以及业界领先的软件,HP ScanJet 6100C专业系列扫描仪使图像扫描又达到了一个新高度。 通过智能扫描技术,ScanJet 610012专业系列扫描仪能够更好地对光进行处理,能在不产生任何变形的情况下捕获高水平信息。这种智能扫描技术的另一大功能是使用扫描仪     

A two-step method for kinematic parameters calibration based on complete pose measurement—Verification on a heavy-duty robot

The poor pose accuracy of industrial robots restricts their further application in aviation manufacturing. Kinematic calibration based on position errors is a traditional method to improve robot accuracy. However, due to the difference between length errors and angle errors in the order of magnitude, it is difficult to accurately calibrate these geometric parameters together. In this paper, a two-step method for robot kinematic parameters calibration and a novel method for position and orientation measurement are proposed and combined to identify these two kinds of errors respectively. The redundant parameter errors that affect the identification are also analyzed and eliminated to further improve the accuracy of this two-step method. Taking the Levenberg-Marquardt algorithm as the underlying algorithm, simulation results indicate that the proposed two-step calibration method has faster iteration speed and higher identification accuracy than the traditional one. On this basis, the calibration and measurement methods proposed in this paper are verified on a heavy-duty robot used for fiber placement. Experimental results show that the mean absolute position error decreases from 0.9906 mm to 0.3703 mm after calibration by the proposed two-step calibration method with redundancy elimination. The absolute position accuracy has increased by 41.81% compared with the traditional method based on position errors only and 14.97% compared with the two-step calibration method without redundancy elimination. At the same time, the orientation errors after calibration are not more than 0.1485°, and the average of absolute errors is 0.0447.     

L型阵列通道不一致及阵元位置误差的联合校正方法

针对L型阵列中通道不一致和阵元位置误差同时存在的情况,利用辅助阵列和校正源,提出一种L型阵列通道不一致和阵元位置误差的解耦合估计方法.该方法计算量小,不需要误差参数的任何先验知识,且校正源的位置可以未知.理论分析和仿真结果表明,提出的方法能很好地解决L型阵列中通道不一致和阵元位置误差的联合校正问题,且两种误差的估计精度高.     

Sensitivity of near infrared total water vapour estimate to calibration errors

Analysis of satellite data to estimate the precipitable water (also called the columnar water vapour) amount often leads to systematic errors in deduced precipitable water (PW). The causes of systematic errors are likely to be instrumental calibration errors rather than variability of atmospheric parameters. We use the MODTRAN 4.0 radiative transfer code to model effects of various calibration errors on the Multi-spectral Thermal Imager (MTI) daytime total water vapour estimate. From the considered sources of calibration errors (spectral band centre error, spectral bandwidth error and radiometric calibration error) the radiometric calibration error has the largest influence on the accuracy of total water vapour estimate. When the radiometric calibration error between 1% and 5% is combined with the estimated spectral band centre error of 1 nm and the bandwidth error of 0.5 nm, the total systematic error of the columnar water vapour estimate is expected to be between 8% and 26%. The accuracy of the retrieved PW using the MTI imagery over the NASA Stennis site and Oklahoma DOE (Department of Energy) ARM (Atmospheric Radiation Measurement program) site is about 17%, well within the estimated range due to calibration errors. A similarity between the MTI and the MODIS (Moderate Resolution Imaging Spectral-Radiometer) bands used for water vapour estimate suggests that a similar error analysis may be valid for the MODIS sensor. However, the narrow band instruments (with bandwidth around 10 nm) are much more sensitive to the band centre calibration error.     

Kinematic Calibration of a Parallel Manipulator for a Semi-physical Simulation System

In the application of a semi-physical simulation system of a space docking mechanism, the simulation precision is determined by pose accuracy of the parallel manipulator. In order to improve pose accuracy, an effective kinematic calibration method is presented to enable the full set of kinematic parameter errors to be estimated by measuring the docking mechanism’s poses. A new calibration model that takes into account geometrical parameter errors and coordinates transformation errors is derived by using a differential geometry method. Based on the calibration model, an iterative least square algorithm is utilized to calculate the above errors. Simulation and experimental results show the calibration method can obviously improve pose accuracy.     

Analysis of unified error model and simulated parameters calibration for robotic machining based on Lie theory

In robotic machining process, the kinematic errors of serial structure and compliance errors caused by external cutter-workpiece interactions can result in considerable deviation of the desired trajectory. Therefore, this paper proposes an efficient calibration methodology by establishing a unified error model about kinematic errors and compliance errors based on Lie theory, which simultaneously calibrates the kinematic parameters and joint compliances of a serial machining robot. In this methodology, the propagation law of kinematic errors is investigated by analysis of the kinematic error model, and the corresponding equivalent kinematic error model is thus obtained, in which the joint offset errors are regarded as one source of twist (joint twist and reference configuration twist) errors. On this basis, with the segmentation and modelling of the joint compliance errors caused by the link self-weight and cutting payloads, the unified error model is developed by linear superposition of configuration errors of the robotic end-cutter, calculated from the kinematic errors and compliance errors respectively. Meanwhile, to improve the accuracy of parameters calibration, the observability index is adopted to optimize the calibration configurations so as to eliminate the twist error constraints. The calibrated kinematic parameters and joint compliances are obtained eventually, and used to compensate the kinematic and compliance errors of the serial machining robot. Finally, to validate the effectiveness of the proposed unified error model, simulation analysis is performed using a 6-DOF serial machining robot, namely KUKA KR500. The comparisons among calibrated parameters show that the unified error model is more computationally efficient with optimal calibration configurations, rendering it suitable for the calibration of kinematic parameters and joint compliances in actual machining applications.     

机器人逆标定方法研究

在分析传统机器人位姿标定方法的基础上，提出了一种新的机器人标定方法：基于神经网络的逆标定方法。这种标定方法把机器人实际位姿和相应的关节角误差分别作为前馈神经网络的输入和输出来训练网络，从而获得机器人任意位姿时的关节角误差值，通过修改关节值来提高机器人的位姿精度。这种标定方法把所有因素引起的误差均归结为关节角误差，无须求解机器人逆运动学方程，实现了误差的在线补偿。把标定结果与基于运动学模型的参数法的标定结果进行了比较分析。仿真和试验结果均证明了这种方法比传统方法标定效果更好，且更方便简单，避免了其他传统标定方法繁琐的建模及参数辨识过程。     

“数据手套”校准误差的分析与消除

随着虚拟现实技术VR（VirtualReality）的推广和应用，数据手套以其轻巧、方便、灵活和包络面大而成为VR的主要输入／输出工具，然而，由于结构上的原因，”手套校准”容易产生累积性误差。在极端情况下，累积性误差将直接影响应用的精度和效果。如何检测、消除累积性误差是设计数据手套的关键。本文以应用最广泛的数据手套为基础，从结构上分析了核准误差产生的原因，给出了手套校准算法和两种消除误差的实际方案。     

基于末端转角误差的并联机器人零点标定方法

针对一种4自由度高速并联机器人（Cross-IV机器人）的零点标定问题,提出了一种基于末端转角误差信息的快速零点标定方法．基于机器人的单支链闭环矢量方程,建立了零点误差全集与末端误差之间的映射模型．通过对误差传递矩阵的分解,在仅利用旋转编码器对末端转角误差进行测量的基础上,构建了该机器人的快速零点误差辨识模型．为进一步最大化测量效率及提高辨识矩阵的鲁棒性,提出了一种优化的测量点选择方案．通过仿真详细验证了该零点标定方法的鲁棒性与准确性．基于激光跟踪仪的验证实验表明,经标定后机器人末端位置误差降低至1.312 mm,转角误差降低至0.202°,标定结果表明该零点标定方法简单、有效．     

Calibration of a TDR probe for low soil water content measurements

Time domain reflectometry (TDR) probes are increasingly used for field and laboratory estimation of soil water content. Usual calibration of TDR probes for the determination of soil water content uses two media: air for low and water for high values of dielectric permittivity, although the measured range of dielectric permittivity in soil is much smaller as compared to the range implied by the calibration media. The use of air for calibration of short TDR probes gives calibration errors due to overlapping incident and reflected pulses in the reflectogram, which result in their relative shift in time. This phenomenon, named the convolution effect, can be avoided by the application of selected calibration media. The presented approach minimizes of dielectric permittivity measurement errors by choosing the calibration media with dielectric permittivity values close to the limits of the measurement range and the possibility to use TDR probes of various lengths. The comparison of errors of TDR apparent dielectric permittivity measurement in three sandy soils, based on the probe calibrations in various media, is also presented.     

On the complexity of energy efficient pairwise calibration in embedded sensors

Technological advances in nanotechnology enabled the use of microelectromechanical systems (MEMS) in various application areas. With the integration of various sensor devices into MEMS, autonomously calibrating these sensors become a major research problem. When performing calibration on real-world embedded sensor network deployments, random errors due to internal and external factors alter the calibration parameters and eventually effect the calibration quality in a negative way. Therefore, during autonomous calibration, calibration paths which has low cost and low error values are preferable. To tackle the calibration problem on embedded wireless sensor networks, we present an energy efficient and minimum error calibration model, and also prove that due to random errors the problem turns into an NP-complete problem. To the best of our knowledge this is the first time a formal proof is presented on the complexity of an iterative calibration based problem when random errors are present in the measurements. We also conducted heuristic tests using genetic algorithm to solve the optimization version of the problem, on various graphs. The NP-completeness result also reveals that more research is needed to examine the complexity of calibration in a more general framework in real-world sensor network deployments.