Large depth-of-view portable three-dimensional laser scanner and its segmental calibration for robot vision

A portable 3D laser scanning system has been designed and built for robot vision. By tilting the charge coupled device (CCD) plane of portable 3D scanning system according to the Scheimpflug condition, the depth-of-view is successfully extended from less than 40 to 100 mm. Based on the tilted camera model, the traditional two-step camera calibration method is modified by introducing the angle factor. Meanwhile, a novel segmental calibration approach, i.e., dividing the whole work range into two parts and calibrating, respectively, with corresponding system parameters, is proposed to effectively improve the measurement accuracy of the large depth-of-view 3D laser scanner. In the process of 3D reconstruction, different calibration parameters are used to transform the 2D coordinates into 3D coordinates according to the different positions of the image in the CCD plane, and the measurement accuracy of 60 mu m is obtained experimentally. Finally, the experiment of scanning a lamina by the large depth-of-view portable 3D laser scanner used by an industrial robot IRB 4400 is also employed to demonstrate the effectiveness and high measurement accuracy of our scanning system. (C) 2007 Elsevier Ltd. All rights reserved.

高精度GPS,三维激光扫描和测针板三种测量技术监测沟蚀过程的对比研究

采用连续模拟降雨试验,对坡沟系统概化模型进行坡面沟蚀发育过程模拟,再现坡面片蚀—细沟侵蚀—切沟侵蚀演变过程。结合3种测量技术从测量精度、测量人员要求、数据处理、数据通用性、配套软件使用、前期投入、测量条件等几个方面入手,对比分析高精度GPS(Trimble 5700)、三维激光扫描仪(Leica HDS 3000)和测针板的3种测量方法的优缺点,同时对3种测量方法在沟蚀过程监测和侵蚀量估算方面进行对比研究。结果表明,激光扫描仪能很好地监测沟蚀演变过程,且对侵蚀量估算精度较高,误差仅为4.5%。高精度GPS也能很好地监测沟蚀演变过程,对侵蚀量估算精度误差为7.38%。测针板法不能很好的反映沟蚀演变过程,但是对于侵蚀量的估算可以满足日常要求,误差为-12.78%。

激光微地貌扫描仪的开发研制及在坡面侵蚀研究应用初步

利用光线的反射与聚焦成象原理 ,将地表高程转换成不同物象点位置的电信号 ,再经计算机处理成数字高程模型 ,即形成用于获取地表糙度数字高程模型的激光微地貌扫描仪。实验测量得到 :在相同初始条件下 ,不同坡度土槽放水和降雨实验后地表形态的数字地形模型。通过对侵蚀地表形态的分析 ,得出坡度对坡面侵蚀及沟蚀影响的某些初步规律。

一种使用GPS、罗盘和激光测距仪测定南极冰川运动的方法

南极冰川运动,是研究南极冰雪物质平衡、环境变化等的重要因素,对其的监测具有重大意义。本文提出了一种配合使用GPS、罗盘和激光测距仪实现测定冰川运动的方法。该方法在完成标定和在冰川上放置标志杆后,无需靠近冰川,只根据远处工作站的GPS、罗盘读数和激光测距仪的测量值就能给出标志杆的GPS数值,从而监测冰川的运动。

Distortion of beam shape by a rotating double-prism wide-angle laser beam scanner

We describe the rigorous results of a wide-angle laser beam scanner, obtained with the help of the vector refraction theory. Using the rigorous results, the distortion of the beam shape is discussed. The distortion to the beam varies with the different relative angles of double prisms. The scanner expands the beam in some directions while it contracts the beam in other directions. According to the conservation of energy, the distribution of the laser intensity is changed as well. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

The effect of the rotating double-prism wide-angle laser beam scanner on the beam shape

In this paper, we describe a wide-angle laser beam scanner and the rigorous result of the wide-angle laser beam scanner was obtained with the help of the vector refraction theory. Using the rigorous results, the distortion of the beam shape was discussed. The distortion of the beam shape is varying with the different relative angles of the double prisms. According to the conservation of the energy, the distribution of the laser intensity is changed too. (c) 2005 Elsevier GmbH. All rights reserved.

Distortion of beam shape by a rotating double-prism wide-angle laser beam scanner

We describe the rigorous results of a wide-angle laser beam scanner, obtained with the help of the vector refraction theory. Using the rigorous results, the distortion of the beam shape is discussed. The distortion to the beam varies with the different relative angles of double prisms. The scanner expands the beam in some directions while it contracts the beam in other directions. According to the conservation of energy, the distribution of the laser intensity is changed as well. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

Research on a scanner for tilting orthogonal double prisms

The original scanner for tilting orthogonal double prisms is studied to test the tracking performance in intersatellite laser communications. With a reduction ratio of more than 100 times from the change rate of the angle of beam deviation to that of the tilting angle of each prism, the theoretical analysis performed, as well as the verification experiment, indicates that the scanner can meet the requirements of the scanning accuracy superior to 0.5 mu rad with the scanning range greater than 500 mu rad and can facilitate the mechanical structure design. (c) 2006 Optical Society of America.

Capillary array electrophoresis with confocal fluorescence rotary scanner

A capillary array electrophoresis system with rotary corifocal fluorescence scanner was reported. High speed direct current rotary motor combined with a rotary encoder and the reflection mirror has been designed to direct exactly the excitation laser beam. to the array of capillaries, which are symmetrically distributed around the motor. The rotary encoder is introduced to accurately orient the position of each capillary and its output signal triggers the data acquiring system to record. the fluorescence signal corresponding to each capillary. Separations of several amino acids are demonstrated by eight-channel capillary array electrophoresis built by ourselves.

Numerical Analysis of a Dual Polarization Mode-Locked Laser with a Quarter Wave Plate

Dynamical behaviors and frequency characteristics of an active mode-locked laser with a quarter wave plate (QWP) are numerically studied by using a set pf vectorial laser equation. Like a polarization self-modulated laser, a frequency shift of half the cavity mode spacing exists between the eigen-modes in the two neutral axes of QWP. Within the active medium, the symmetric gain and cavity structure maintain the pulse's circular polarization with left-hand and right-hand in turn for each round trip. Once the left-hand or right-hand circularly polarized pulse passes through QWP, its polarization is linear and the polarized direction is in one of the directions of i45o with respect to the neutral axes of QWP. The output components in the directions of i45" from the mirror close to QWP are all linearly polarized with a period of twice the round-trip time.

Polarization Self-Modulation Phenomenon in a Free Oscillated Nd: YAG Laser

Polarization self-modulation effect in a free oscillated Nd:YAG laser is investigated after a quarter wave plate is introduced independently in the two positions of the cavity. As described in the previous experiments, the intensity components in the orthogonal directions are modulated with a period of the round-trip time or twice. Different pulse shapes reveal that the seed field from the spontaneous emission is not uniform and seems to be stochastic for each pulse.

Surface amorphous and crystalline microstructure by alloying zirconium using Nd : YAG pulsed laser

A novel composite coating was synthesized by laser alloying of zirconium nanoparticles on an austenite stainless steel surface using a pulsed Nd:YAG laser. The coating contained duplex microstructures comprising an amorphous phase and an austenitic matrix. A discontinuous zirconium-containing region formed at a depth of 16 mum below the surface. The amorphous phase was present in the zirconium-rich region, with the composition of zirconium ranging from 7.8 to 14.5 at. pet. The formation of the amorphous phase was attributed to the zirconium addition. The hardness, corrosion, and wear-corrosion resistance of the irradiated coating were evidently enhanced compared to those of the stainless steel.

Application of enthalpy method for moving boundary problem in laser surface melting

A numerical analysis was carried out to study the moving boundary problem in the physical process of pulsed Nd-YAG laser surface melting prior to vaporization. The enthalpy method was applied to solve this two-phase axisymmetrical melting problem Computational results of temperature fields were obtained, which provide useful information to practical laser treatment processing. The validity of enthalpy method in solving such problems is presented.

Microstructure and wear resistance of in situ TiCp composite coating by laser cladding

A new in situ method was realized by one step laser cladding to produce Ni-base alloy composite coating reinforced by in situ reacted and gradiently distributed TiCp particles. The submicron TiCp particles were formed and uniformly distributed because of the in situ reaction and trapping effect under the rapid solidification condition. And, TiCp particles were of gradient distribution on a macro scale and their volume fraction increased from 1.86% at the layer/substrate interface to a maximum 38.4% at the surface of the layer. Furthermore, the in situ generated TiCp/gamma-Ni interfaces were free from deleterious surface reactions. Additionally, the clad coating also revealed a high microhardness of gradient variation with the layer depth and the superior abrasive wear resistance.