成像法测量脉冲激光远场能量密度的模型及不确定度分析

 设计了基于漫反射成像法测量脉冲激光远场能量分布的方案,在相机标定的基础上建立了CCD图像灰度值与漫反射板上脉冲激光能量密度对应关系的数学模型,该模型考虑了漫反射板的漫反射率和CCD像元响应度的空间不一致性,并对不同测量位置的离轴角的影响进行了修正。分析表明:CCD灰度值、镜头透过率、漫反射率和CCD响应度的不确定度传播系数为1,镜头光圈数的不确定度传播系数为2,镜头焦距的不确定传播系数随离轴角增大而增大,成像中心像素坐标的不确定度传播系数在图像顶点处最大。针对相机标定实验中发现的利用Tsai单视角共面点标定相机得到的镜头焦距与实际存在较大偏差问题,指出对于定焦镜头,应该采用其它离线方法进行准确标定;对于变焦镜头,可采用单视角非共面点或多视角共面点进行在线标定。     

利用激光三角测距法提高三维面型检测精度的方法

本文首先介绍了根据激光三角测距原理并采用片光照明、面阵ＣＣＤ接收的三维面形检测原理，其优点在于物面相对于测量头仅需一个方向移动即可完成二维扫描，使测量系统结构简单、便于控制。其次分析了影响其测量精度的几个主要因素，即散斑噪声、接收器件本身的分辨率、投影片光束的宽度与稳定性。散斑噪声造成了投影光斑的抖动，ＣＣＤ的分辨率限制了测量系统的分辨率，而片光束的质量影响着ＣＣＤ光敏面上像斑的准确定位。针对其各自的特点给出了相应的解决途径。     

Dazzling effect of repetitive short pulse laser on TDI CCD camera

A dazzling experiment was performed on a 64-stage TDI CCD camera using a 20 Hz repetition frequency picoseconds pulse laser, during which we found a new dazzling effect in which the fringes appeared in the video of the camera beside the saturation spot induced by the laser. We considered it to be the scattered light of the repetition frequency laser pulse to have induced the phenomenon. Width and visibility of the fringes recorded the information of the scattered light, such as repetitive frequency, pulse width and intensity distribution. With the assumption that the laser pulse width is less than one stage integral time of TDI CCD, width expressions for the fringes and space between the fringes were given using the repetitive frequency of laser pulse, row output frequency and integral stage number of the TDI CCD camera.     

激光片光三维传感中降低散斑影响的新方法

提出一种激光片光三维传感中降低散斑影响的新方法,片光面内扫描合成孔径法。通过向被测物体表面投射面内扫描的片状激光束,产生空间变化的动态散斑光场,这样的光场在成像透镜光瞳平面上的移动,其时间平均效果等效于利用了一个大的“合成孔径”,降低了散斑的影响,明显地提高了测量精度。文中给出了合成孔径的理论分析和三维面形测量的实验结果。     

Line-laser-based yarn shadow sensing break sensor

In this paper, a line-laser-based yarn break sensor is proposed. In the proposed sensor, yarns are illuminated by a line laser placed on one side of the yarn plane. A screen is placed on the other side and the image formed on the screen is detected by a camera. The total number of yarns is compared with the total number of shadows formed by the yarns or the total number of light spots formed due to the distances between yarns. If the total number of yarns to be detected is greater than the total number of shadows or light spots formed due to the distances between the yarns, the sensor warns of breaking. In the proposed method, evaluation is made using only light spots or shadows formed by the yarns. Consequently, the yarn type, structure, color, or dimensions do not affect the results.Design principles of the line-laser-based yarn break sensor, which consists of a screen and a Charged Coupled Device (CCD) camera, are presented. The screen displays the shadows formed by the yarns and the light spots formed due to the distances between them. The CCD camera detects the image on the screen. Formation of the shadows by the yarns is explained and an analytical formula that expresses the dimensions of the shadows is obtained. The detection area of the sensor is expressed relative to the total number of yarns, yarn thickness, and distances between the yarns. Line laser radiation angle and light spot intensity equations are obtained relative to the width of the detection area and the height of the line laser placement. The screen length is obtained relative to the number of yarns and the placement of the laser, the yarn plane, and the screen.Different placement situations of the line laser (transmitter), the screen, and the CCD camera (receiver) relative to the yarn plane are discussed. An experimental setup is developed to test the system. The image formed on the screen is studied.     

Line laser-based break sensor that detects light spots on yarns

In this paper, current yarn break sensor systems are investigated and a line laser-based yarn break sensor is proposed. In this proposed sensor system, yarns aligned in the same plane are illuminated with a line light and the light spots on the yarns are detected with a CCD camera, total yarn number is compared with the number of the light spots formed by the line laser on yarns. If the number of the yarns used is greater than the number of the light spots, sensor warns the breaking.Design principles of the line laser-based yarn break sensor are presented. Detection area of the sensor related to the yarn number, yarn thickness and the distances between the yarns is obtained. Equations for calculating the line laser radiation angle and the light spot intensity related to the detection area width and the line laser placement height are obtained.Different placement situations of line laser (transmitter) and the CCD camera (receiver) related to the yarn plane are explained. An experimental setup is developed to test the system and the image of the light spots formed on yarns is obtained. Block diagram of the sensor is given and the operation principle is explained.     

利用线阵CCD自动测量航空相机镜头的焦距

提出了一种以线阵CCD固态传感器取代读数显微镜的航空相机镜头焦距测量系统。论述了系统的工作原理、软件和硬件的设计及系统的测量误差。结果表明 ,利用线阵固态图像传感器取代读数显微镜 ,把特定物体经透镜成像的大小转换为电信号的脉宽 ,并利用计算机技术自动处理测量数据 ,从根本上克服了用读数显微镜进行测量的缺陷 ,实现了航空相机镜头焦距的实时精确地在线测量     

正交狭缝扫描式激光光束质量测量方法研究

传统激光光束质量测量方法在CCD相机靶面前激光光路上加装可调衰减模块,对激光光束进行衰减。但该方法受限于CCD相机像元尺寸限制,难以进行高精度测量。为此该文提出了一种滚轮狭缝式激光光束质量评价方法,在测量时采用狭缝滚轮上的扫描狭缝直接扫描被测激光光束,使用InGaAs探测器配合聚焦透镜进行测量。经过与电机同轴的高精度增量式编码器确保采集位置与采集数据同步,扫描频率根据被测激光脉冲频率和光斑的直径范围可进行调整,该方法对光斑空间采样分辨率优于1 μm。实验结果表明,采用该方法测得的激光M2因子数值与被测激光器提供数值一致,测量不确定度小于10%。     

激光远场焦斑测试技术的实验研究

 实验研究了激光远场焦斑能量分布测试的三种方法（长焦距透镜法、列阵相机法、Rattle Pair法），对三种测试方法得到的实验数据进行了比对，系统地分析了每种方法的优缺点。结果表明,采用长焦距透镜与一对微楔角劈板组合测试激光远场焦斑的方法更具优势，可减少测试系统引入的像差，并使图像处理过程得到简化。     

Compact three-dimensional camera for robot and vehicle guidance

A very compact 3-D range sensor for robot and vehicle guidance is described. A dual aperture mask in a camera lens is used to transform a small commercially available CCD video camera into a ranging sensor. An active system using a projected laser beam provides a 360° range map which can be used to plan trajectories, either for robots or autonomous vehicles. Good quality panoramic intensity and 3-D images were obtained. Accuracy, speed of acquisition, and cost are discussed. Experimental results are presented.     

CCD强光串扰效应的串扰线缺口现象及其机制

在激光辐照行间转移CCD相机的实验中发现了关于CCD串扰效应的一个新现象,即在串扰线上出现缺口,该缺口紧邻主光斑上侧且随光强增大而减小。基于行间转移面阵CCD的构造和工作过程,利用CCD串扰效应的一种新机制对现象作出了合理的解释。串扰线的形成依赖于在垂直转移动作过程中CCD信号积分势阱中的载流子向垂直转移CCD寄存器中的溢出。串扰线上缺口的出现则是由于CCD的信号积分势阱被读出转移动作清空后再次填满需要经过一定时间,该时间内无信号电荷溢出至转移沟道;读出转移清空存储势阱的时刻是构成主光斑的主体信号电荷按正常时序进入垂直转移CCD寄存器的时刻,故缺口紧邻主光斑的上侧;光强越大,光电子再次填满存储势阱乃至溢出形成串扰线所需要的时间越短,则缺口越小。     

Enlarging lens design with f-Θ lens for real time laser lithography inspections

An enlarging lens, composed of a charge-coupled-device (CCD) lens and an f-Θ lens, has been designed for real time laser lithography visual inspection purposes. The object of this design is to enlarge the image of the working specimens in real time, which used to be done by an independent magnifying system after the lithography process. F-Θ lens has both roles in this design, being a laser lithography lens and a specimen imaging lens. A beam splitter has been inserted between the f-Θ lens and the CCD lens, which divides the UV laser beam and the visible beam to form a coaxial system. This design also reaches the image requirements in both wavelength bands, that the value of MTF is nearly diffraction-limit in UV wavelength and greater than 0.45 at 40 c/mm in visible wavelength.     

Laser ray-tracing method for optical testing

We have developed a novel laser ray-tracing method to measure aberrations in optical systems. It consists of delivering narrow laser pencils (by a laser scanner), recording the spots that are formed on the image plane (with a CCD camera), and computing the position of each centroid. This approach could be considered an experimental (approximate) implementation of standard numerical ray tracing. Several tests and experiments, including a direct comparison with a Hartmann-Shack wave-front sensor, provided highly satisfactory results that confirmed the validity of the method and revealed potential advantages.     

基于折线采样的高分辨率成像系统设计

针对现有的提高线阵电荷耦合器件(CCD)成像系统的图像空间分辨率的方法存在的不足,提出了一种新的采样模式,并设计了一种高分辨率成像系统。该系统利用两个相同的线阵CCD相机进行特定的空间排列,即使得相机1和相机2的CCD阵列都倾斜θ来进行扫描取像,并利用图像校正和像素插值等图像重建方法,得到高分辨率的图像。实验结果表明,倾斜角取60°的情况下,相对于单个线阵相机在θ=0°的正常采样模式下得到的采样图像,图像的空间分辨率提高了1倍,且保持了成像的视野不变。本系统工程上实现简单,十分经济且便于维护,仅利用现有的成像装置即可获取更高分辨率的图像。     

光子计数成像技术及其应用

介绍光子计数实时图像采集实验系统，其中的高亮度增益的光子成像头通过超强光力中继透与高帧频电荷耦合器摄像机耦合；分析和介绍了单光子成像模式下系统工作的受限条件和多光子工作模式下系统的主要综合性能指标－读出噪声的测定方法。文中给出在自适应光学弱光波前传感中的应用，光子噪声分布规律以及光的波粒二象性实验验证等例子。     

数码相机图像传感器技术

介绍了数码相机中图像传感器的关键技术和相关的新技术。目前广泛被使用的图像传感器是CCD、SuperCCD和CMOSImageSensor(互补性氧化金属半导体图像传感器)。在分析和介绍图像传感器的结构、读出方式、彩色滤光阵列(CFA)等技术内容的基础上,对数码相机设计采用的图像传感器在关键技术指标进行了综合对比。     

高速线扫描共焦检眼镜

高速线扫描共焦检眼镜使用线光束照明眼底视网膜,同时利用线阵CCD对视网膜平面的单次散射线光束探测成像。系统光学放大率为7倍,横向分辨率小于10μm,对于58kHz线频的1024pixel×512pixel成像模式,成像帧频高达110frame/s。该系统实现了高分辨率、高帧频模拟人眼实验图像的获取。     

基于衍射光栅的CCD相机标定方法

提出一种基于1维线衍射光栅的CCD相机光电响应特性标定方法,该方法利用衍射光栅对入射光束的分束特性,在远场焦平面内形成一系列衍射子光斑,采取有效的方法对多组衍射子光斑峰值测量数据进行融合,得到测量灰度值及通过理论计算得到的理论灰度值,拟合两组数据从而完成对CCD光电响应特性的标定.根据实验室现有的激光源与聚焦光学系统的...     

神龙一号参数测量用高速两分幅相机

采用长焦距镜头的后工作空间全口径分光原理,利用门控型像增强器、CCD相机、基于大规模可编程集成电路的高速快门控制触发系统等部件,研制了具有较高时间分辨能力和高灵敏度的两分幅高速相机,并在此基础上建立了束参数的高速测量系统。两分幅相机的最高快门速度约3 ns,幅间间隔时间则具有以0.5 ns的步进进行调节的能力;快门时间及幅间间隔时间可以分别独立调节,最大可到1 s;同时具有较好的线性度和空间响应的均匀性,等效背景噪声低到约5 electronspixel-1s-1,并且分幅相机灵敏度调节范围大。该系统一次可以拍摄两幅图像,图像阵列可达到1 0241 024,满足神龙一号的各种测量要求。     

Vibration analysis by laser speckle correlation

Time-averaged laser speckle correlation is used for flexural vibration-studies. The proposed method employs a diverging laser beam to illuminate the test object and records the object image at a defocused plane with a CCD camera. The speckle correlation coefficient is a function of the out-of-plane tilt of the object. The time-averaged speckle pattern recorded with the object vibrating at a natural mode is subtracted from the one recorded in a static condition. The anti-nodes of the vibrating object can then be identified easily on the subtracted image. A brief analysis of the technique and some experimental results on a cantilever beam and a vibrating plate are presented.