基于时间参考点的差动式线阵CCD位移传感器

为了将线阵CCD应用于实际工程的大尺寸位移测量,利用线阵CCD像元空间与输出时间的对应关系,提出了一种差动式测量的线阵CCD位移传感器测量系统。分析了线阵CCD位移测量存在的问题,结合线阵CCD中像元空间与驱动脉冲之间的对应关系,提出一种以时间为参考点的差动式测量方法。该方法用两个空间上对齐、时间上错开半个积分周期的线阵CCD检测透光挡板上等间距分布的透光光线的位置变化;通过计算两个CCD上输出光信号的时间差,用匀速扫描测量原理实现对空间位移的测量。用雷尼绍激光干涉仪对所研制的线阵CCD位移传感器进行了校准,结果显示：在有效测量范围（600.05 mm）内,经过修正后的测量误差可控制在±2 μm以内,验证了用差动法实现线阵CCD大尺寸精密位移测量的可行性。     

Study of magneto-optic element as a displacement sensor

Displacement sensors are important components in many instrumentation systems, but the existing electrical based systems suffer from electromagnetic interference, noise, low response, etc. In the present paper, a magneto-optic element like Terbium Doped Glass (TDG) has been experimentally studied in double pass mode for its use as a displacement sensor. A high sensitive linear (with in ±0.54%) microdisplacement sensor with improved performance over an appreciable range of 10 mm with a resolution of 5 μm is achieved. The theoretical analysis and experimental results are reported in the paper. The experimental data have been found to be in good agreement with the theoretical study.     

Towards a model for the number of airborne particles generated from a sliding contact

Recently, much attention has been given to the influence of airborne particles in the atmosphere on human health. Sliding contacts are a significant source of airborne particles in urban environments. Airborne particles may be generated by disc brakes and wheel-rail contacts. This paper presents a new model for determining the number of airborne particles generated by a sliding contact. Previously presented data from a pin-on-disc tribometer equipped with airborne particle counting instrumentation was used to verify the model. The derived particle rate is proportional to the load for the ball bearing steel material evaluated. Furthermore, the model incorporates three particle regimes with distinct number peaks; one with ultra fine particles with a peak around 0.08 μm, one with fine particles with a peak around 0.35 μm and one with coarse particles with a peak around 2 μm, that can be used to rank the number of generated particles from different material combinations and contact conditions.     

Multi-beam laser probe for measuring position and orientation of freeform surface

This study develops a novel optical non-contact probe that measures the position and orientation (normal vector) of a freeform surface. The probe system comprises a five-laser-beam projector and a charge-coupled device (CCD) camera. The probe is integrated on a three-axis platform. Five designed laser beams project onto a measuring surface, where five light spots are observed. The CCD captures the image of this surface and processes it. The 3D coordinates of the five light spots can be then computed. The normal direction at the central spot on the measuring surface is determined from two crossed curves through the coordinates of these five light spots. Two crossed curves are constructed using the Bezier method. The normal vector is the cross-product of two tangent vectors to the two crossed curves at central spot. A scheme for calibrating and making measurements using this five-laser-beam probe is proposed and verified experimentally. Experimental results demonstrate that this five-laser-beam probe system can measure the position and orientation of a freeform surface. The range of depths that can be measured using this probe is 2.4 mm and the range of angles is 40°. The positional measuring accuracy of the complete system is approximately 30 μm while the orientational accuracy is 1.8°.     

Basic investigation of noncontact transportation system for large TFT-LCD glass sheet used in CCD inspection section

Recently, thin film transistor liquid crystal displays (TFT-LCDs) have been successfully applied to desktop personal computer (PC) monitors and televisions. Higher resolution and larger mother glass sheets have been required for television displays in particular to reduce costs and improve production efficiencies. To handle the increasing resolution and mother glass size, high-speed inspection processes for detecting defects in TFT arrays using charge coupled device (CCD) cameras are becoming very important. Therefore, a noncontact transportation technique for the high-speed inspection section is necessary, to avoid damage to the glass sheet during the inspection process. In addition, high-speed CCD cameras with high resolution, large magnification and shallow focus depth are usually used in the inspection process. Accordingly, it was reported that fluctuations of less than 20 μm in the floating gap of the LCD glass sheet were required. We have used a 240 mm square LCD glass sheet as the first step of this study and an air-pad system using porous metal was investigated to support the glass sheet. The influence on the flatness of design parameters such as the nonuniformity of the permeability of the porous air pads and the appropriate combination of supply and exhaust pressures were investigated numerically for a glass sheet that was quiescently supported by the proposed air-pad system. Moreover, the numerical results are compared with experimental results to verify the validity of the numerical predictions. We found that the flatness of the glass sheet of less than 15 μm could be achieved experimentally with a floating gap of around 30 μm by using the proposed air-pad system.     

Detective quantum efficiency of electron area detectors in electron microscopy

Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology. We present MTF and DQE measurements for four types of detector: Kodak SO-163 film, TVIPS 224 charge coupled device (CCD) detector, the Medipix2 hybrid pixel detector, and an experimental direct electron monolithic active pixel sensor (MAPS) detector. Film and CCD performance was measured at 120 and 300 keV, while results are presented for the Medipix2 at 120 keV and for the MAPS detector at 300 keV. In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated. We also show that part of the response of the emulsion in film comes from light generated in the plastic support. Computer simulations of film and the MAPS detector have been carried out and show good agreement with experiment. The agreement enables us to conclude that the DQE of a backthinned direct electron MAPS detector is likely to be equal to, or better than, that of film at 300 keV.     

基于机器视觉的光学元件表面洁净度检测仪研制

针对SG-III精密光学元件表面洁净度检测特点,提出了基于机器视觉的检测方案。设计了三维电控平台和夹持架,选用步进电机和光栅尺实现闭环高精度控制,采用线阵CCD作为图像采集设备,选用卤素灯作为光源,利用图像处理技术得到污染物的特征参数。对340mm*340mm的光学元件测试表明,检测仪能在11分钟内完成单面扫描和分析,识别15μm以上的污染物,大大提高了检测效率。该技术可应用于多种精密表面检测项目。     

PIV measurements of two phase velocity fields in aeolian sediment transport using fluorescent tracer particles

This paper presents a method to simultaneously determine the velocity fields of both phases in aeolian sediment transport by means of PIV with fluorescent tracer particles. The fluorescent particles were atomized micron-sized droplets of rhodamine B solution. Specific optical filters were employed to ensure that the fluorescent tracer particles and the sand particles were respectively imaged on two CCD (charge-coupled device) cameras during measurement. A cross-correlation algorithm and image processing were used to obtain vector plots. The experimental results show that the distributions of the averaged velocity u of the wind-sand flow in both phases were concave downward curves on a semilogarithmic figure. The upper parts of the profiles of both phases fitted well with a logarithmic distribution. When sand particle sizes were smaller than or equal to 160 μm, the averaged velocity u of both phases decreased with increasing particle size. The difference between the horizontal velocities (i.e. relative velocity u_r) in both phases of the sand phase increased with increasing particle size and height. In the region where h/δ < 0.25, the momentum transfer between both phases was the most intense, and the effect of the air viscosity on the sand motion played an important role in the transfer. In the region where h/δ > 0.85, the horizontal velocity hysteresis between both phases in each group of samples tended to be constant. For a sand particle diameter of 80-200 μm, Re_r changed linearly with the square root of d_m at the top of the saltation layer.     

星载多光谱CCD相机研究

研制的星载多光谱 CCD相机采用线阵 CCD推扫方式成像 ,具有蓝、绿、红、近红外、全色五个成像谱段 ,在轨工作时地面像元分辨率为 2 0米 ,覆盖宽度 113公里。相机光学系统采用单镜头焦面分色结构实现多光谱成像 ,每个谱段的探测器阵列由 3片 2 0 4 8元 CCD光学拼接而成 ,以实现地面宽覆盖成像。多片 CCD信号采用串行读出方式 ,使焦面 15片 CCD形成两路视频信号输出给数据传输系统。测试结果显示 ,相机各谱段 MTF典型值为 0 .2 5 ,满足使用要求。     

多光谱 CCD 相机几何标定技术研究

多光谱CCD相机的技术特点是利用不同遥感谱段获得同一目标图像,通过不同谱段图像的组合,获取地物目标的物理特性。为了使多光谱CCD相机同时还具备测绘功能,能对获取的地物目标进行精确定位,发射前需要在实验室对多光谱CCD相机的几何参数进行精确标定。多光谱CCD相机几何标定是相机研制过程中的关键环节,是确定相机在惯性坐标系中姿态的必不可少的关键技术。本文着重介绍了多光谱CCD相机几何标定设备、标定方法和标定精度。多次标定结果表明：主距的标定精度优于10μm （1σ）,主点的标定精度优于2.1μm （1σ）,畸变的标定精度优于1.5μm （1σ）,满足多光谱CCD相机几何标定精度的要求。     

Multiple scattering effects of MeV electrons in very thick amorphous specimens

Multiple scattering has an important influence on the analysis of microns-thick specimens with MeV electrons. In this paper, we report on effects of multiple scattering of MeV electrons on electron transmission and imaging of tilted and thick amorphous film specimens by experiment and theoretical analysis. Electron transmission for microns-thick epoxy-resin and SiO₂ specimens calculated by the multiple elastic-scattering theory is in good agreement with measurements in the ultrahigh voltage electron microscope (ultra-HVEM) at Osaka University. Electron transmission and electron energy are then presented in an approximate power law. The bright-field ultra-HVEM images of gold particles on the top or bottom surfaces of 5 and 15 μm thick specimens further illustrate the effect of multiple scattering on image quality. The observed top‐bottom effect for the very thick specimens appears to be mainly caused by multiple elastic scattering. With increase in the accelerating voltage from 1 to 2 MV, image blurring, contrast, the signal-to-noise ratio, and the top‐bottom effect are improved because of reduction in the influence of multiple scattering. However, the effect of specimen thickness on image blurring is shown to be stronger than that of accelerating voltage. At the 2 MV accelerating voltage, the 100 nm gold particle can be imaged with less blurring of ∼4 nm when located at the bottom surface of a 15 μm thick epoxy-resin specimen.     

Miniature low-power IR monitor for methane detection

A portable methane gas monitor based on an infrared spectrum absorption principle has been developed using a dual-channel and dual-wavelength pyroelectric infrared detector, active filters around the overtone absorption lines of methane at 3.31 μm, reference filters around the non-absorption lines of methane at 3.93 μm, mid-IR LEDs, a miniature gold-filled cell structure, temperature sensors for gas concentration calibration and compensation, an electrical modulation source, and a highly integrated intelligent controller. A detailed investigation has been carried out to design a low-cost portable IR optical sensor for methane detection that can operate in harsh environments with temperature variations between −10 °C and 40 °C. The infrared detection optics principle used in developing this system is mainly analyzed. A prototype based on this design showed an accuracy of ±0.05%, which meets the technology requirements of lower-power consumption, reduced volume, and wide measurement range.     

光学系统弥散斑参数的测试

采用CCD显微成像系统对光学系统弥散斑参数进行定量测量,并设计了弥散斑参数的评价算法。首先,给出了弥散斑参数的定义,分析了弥散斑所形成的能量等高线构成的闭合的连通区域,对占总能量80%的区域计算其弥散斑直径。然后,对该区域的边界点进行椭圆拟合,得到弥散斑圆度。提出的方法通过对光学系统在像平面所成的星点像的能量分布的分析,在弥散斑圆度测试中引入了椭圆拟合,减少了CCD噪声和测试环境中的杂光等随机因素对测试结果的影响,提高了测试结果的置信度。实验结果显示:弥散斑直径测试重复性为0.18μm,弥散斑圆度测试重复性为1.65%。提出的方法实现了弥散斑参数的定量测试,满足航天项目中光学系统成像质量控制要求。     

自动阿贝折射仪的研究

提出了基于光的全反射原理,利用单色发光二极管作为光源和线阵CCD作为传感器,结合计算机图像处理技术,实现了WYA-Z自动阿贝折射仪的设计。并简要介绍了仪器的工作原理、光路系统、仪器组成、关键技术、设计要求及实验验证。实验结果表明:仪器的折射率测量范围:1.3000～1.7000,精度n_D:±0.0002,重复性n_D:±0.0001。该仪器不仅能自动测量液体的折射率,还能自动测量液体的浓度,因此具有广阔的市场前景。     

Application of the central composite design in optimization of machining parameters in drilling hybrid metal matrix composites

In this study, the application of response surface methodology (RSM) and central composite design (CCD) for modeling, optimization, and an analysis of the influences of dominant machining parameters on thrust force, surface roughness and burr height in the drilling of hybrid metal matrix composites produced through stir casting route. Experiments are carried out using Al 356-aluminum alloy reinforced with silicon carbide of size 25 μm and Mica of size 45 μm. Drilling test is carried out using carbide drill of 6 mm diameter. The design of experiment concept has been used to optimize the experimental conditions. The experimental data are collected based on a three-factor-three-level full central composite design. The multiple regression analysis using RSM is used to establish the input–output relationships of the process. The mathematical models are developed and tested for adequacy using analysis of variance and other adequacy measures using the developed models. The main and interaction effect of the input variables on the predicted responses are investigated. The predicted values and measured values are fairly close, which indicate that the developed models can be effectively used to predict the responses in the drilling of hybrid metal matrix composites. The optimized drilling process parameters have been obtained by numerical optimization using RSM by ensuring the minimum thrust force of 84 N, surface roughness of 1.67 μm, and the burr height of 0.16 mm. After the drilling experiments, a scanning electron microscope (SEM) is used to investigate the machined surface and tool wear.     

Developing a Confocal Acoustic Holography Microscope for non-invasive 3D temperature and composition measurements

A Confocal Acoustic Holography Microscope (CAHM) has been designed, simulated and partially verified experimentally to take holograms for non-invasive, three-dimensional measurements of a specimen's refractive indices from one view point. The designed and simulated prototype CAHM used a frequency of 2.25 MHz and measured sound speed changes of 16 m/s, temperature changes of 5 °C and had a spatial resolution of 660 μm. With future improvements utilizing the latest technologies such as two-dimensional array detectors, Micro-Electro-Mechanical Systems (MEMS), and acoustic lenses, resolutions of 1 m/s, 0.5 °C, and 150 μm are expected. The CAHM is expected to have many useful applications, including non-invasive mass and heat transfer measurements in fluids and materials and as a medical diagnostic tool to non-intrusively visualize compositions and temperatures within the human body.     

Characterization of a direct detection device imaging camera for transmission electron microscopy

The complete characterization of a novel direct detection device (DDD) camera for transmission electron microscopy is reported, for the first time at primary electron energies of 120 and 200 keV. Unlike a standard charge coupled device (CCD) camera, this device does not require a scintillator. The DDD transfers signal up to 65 lines/mm providing the basis for a high-performance platform for a new generation of wide field-of-view high-resolution cameras. An image of a thin section of virus particles is presented to illustrate the substantially improved performance of this sensor over current indirectly coupled CCD cameras.     

一种高分辨率的光纤定位单元定位精度的测量装置

目前对光纤定位单元定位精度的检测所使用的测量手段是摄影测量,由于被测光纤的孔径非常小,使得这种测量方法的分辨率不高。该文提出了一种新的测量方法,检测装置由显微镜、CCD相机、二维精密移动平台组成。被测光纤通过显微镜放大成像于CCD中,通过对CCD所拍摄照片的实时处理,建立位置反馈机制,实时操控二维精密移动平台追随光纤运动,光纤在运动中始终成像于CCD视场中心,通过读取移动平台坐标的变化来表征光纤移动的位置变化。实验结果表明,该套测量系统的分辨率达到了0．1μm,重复定位精度1．5μm,实现了高精度的检测要求。     

基于线阵CCD的空间目标外姿态测量系统

设计了9路线阵CCD相机组合的空间目标外姿态测量系统,它克服了采用面阵图像传感器用于姿态测量时存在的速度和精度的矛盾。该系统分别实时重构放置于被测物体上的点合作目标在世界坐标系下的三维坐标,经空间解算,确定被测物体的姿态角。着眼于合作目标和相机光学系统的相对位置及呼应,解决了多相机与多点合作目标一一对应时的目标干扰问题;设计了新的光学系统构架,提高了精度,节省了空间;实现了多相机测量系统的局部标定和全局标定。测试结果表明,该姿态测量系统可以实现对被测对象高精度、实时的测量,且具有合作目标简单,价格低廉等优点。     

Metrological evaluation of Microsoft Kinect and Asus Xtion sensors

In recent months Kinect and Xtion sensors appear massively at the entertainment market. In parallel, many developers show engineering applications of the system related with their 3D imaging possibilities. In this work a metrological geometric verification of the systems is performed using a standard artifact which consists of five delrin spheres and seven aluminum cubes. Accuracy and precision tests show non-dependence with the type of sensor (two Kinect and one Xtion are used for the experiment) or with the incident angle between the standard artifact and the sensor (45°, 90° and 135°). Precision decreases with range according to a second order polynomial equation. Ranges larger than 7 m cannot provide any measurement. Accuracy data change from 5 mm to −15 mm for 1 m range and from 5 mm to −25 mm for 2 m range. Precision data change from 1 mm to 6 mm for 1 m range and from 4 mm to 14 mm for 2 m range.