• Title, Summary, Keyword: Laser scanning

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The Scanning Laser Source Technique for Detection of Surface-Breaking and Subsurface Defect

  • Sohn, Young-Hoon;Krishnaswamy, Sridhar
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.3
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    • pp.246-254
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    • 2007
  • The scanning laser source (SLS) technique is a promising new laser ultrasonic tool for the detection of small surface-breaking defects. The SLS approach is based on monitoring the changes in laser-generated ultrasound as a laser source is scanned over a defect. Changes in amplitude and frequency content are observed for ultrasound generated by the laser over uniform and defective areas. The SLS technique uses a point or a short line-focused high-power laser beam which is swept across the test specimen surface and passes over surface-breaking or subsurface flaws. The ultrasonic signal that arrives at the Rayleigh wave speed is monitored as the SLS is scanned. It is found that the amplitude and frequency of the measured ultrasonic signal have specific variations when the laser source approaches, passes over and moves behind the defect. In this paper, the setup for SLS experiments with full B-scan capability is described and SLS signatures from small surface-breaking and subsurface flaws are discussed using a point or short line focused laser source.

Evaluation of Geometric Error Sources for Terrestrial Laser Scanner

  • Lee, Ji Sang;Hong, Seung Hwan;Park, Il Suk;Cho, Hyoung Sig;Sohn, Hong Gyoo
    • Journal of Korean Society for Geospatial Information System
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    • v.24 no.2
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    • pp.79-87
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    • 2016
  • As 3D geospatial information is demanded, terrestrial laser scanners which can obtain 3D model of objects have been applied in various fields such as Building Information Modeling (BIM), structural analysis, and disaster management. To acquire precise data, performance evaluation of a terrestrial laser scanner must be conducted. While existing 3D surveying equipment like a total station has a standard method for performance evaluation, a terrestrial laser scanner evaluation technique for users is not established. This paper categorizes and analyzes error sources which generally occur in terrestrial laser scanning. In addition to the prior researches about categorizing error sources of terrestrial Laser scanning, this paper evaluates the error sources by the actual field tests for the smooth in-situ applications.The error factors in terrestrial laser scanning are categorized into interior error caused by mechanical errors in a terrestrial laser scanner and exterior errors affected by scanning geometry and target property. Each error sources were evaluated by simulation and actual experiments. The 3D coordinates of observed target can be distortedby the biases in distance and rotation measurement in scanning system. In particular, the exterior factors caused significant geometric errors in observed point cloud. The noise points can be generated by steep incidence angle, mixed-pixel and crosstalk. In using terrestrial laser scanner, elaborate scanning plan and proper post processing are required to obtain valid and accurate 3D spatial information.

Automation of laser scanning and registration of measured data using a 3-axis motorized stage (3축 전동테이블을 이용한 레이저 스캐너의 측정 및 레지스트레이션 자동화)

  • Son, Seok-Bae;Kim, Seung-Man;Lee, Kwan-Heng
    • Proceedings of the KSME Conference
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    • pp.134-139
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    • 2001
  • Laser scanners are widely used for reverse engineering and inspection of freeform parts in industry such as motors, electronic products, dies and molds. Due to the lack of measuring software and positioning device, the laser scanning processes have been erroneous and inconsistent. In order to automate measuring processes, an automated scan plan generation software and a proprietary hardware are developed. In this paper, an automated laser scanning system using a 3-axis motorized stage is proposed. In the scan planning step, scan directions, paths, and the number of scans are generated considering optical and mechanical parameters. In the scanning step, the generated scan plan is downloaded into the laser scanner and the motorized stage and the points on the surface are captured automatically. Finally, the point data set is analyzed to evaluate the performance of the system.

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Analysis of the Local Properties in GdBCO and YBCO Coated Conductors using Low-temperature Scanning Laser and Hall Probe Microscopy (저온 주사 레이저 및 홀소자 현미경을 이용한 GdBCO와 YBCO 초전도 선재의 국소적 특성 분석)

  • Park, S.K.;Ri, H.C.
    • Progress in Superconductivity
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    • v.13 no.3
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    • pp.169-177
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    • 2012
  • Distribution of the local properties in GdBCO and YBCO coated conductors was investigated using Low-temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). We prepared GdBCO and YBCO coated conductors to study the spatial distribution of the current density in a single bridge. Inhomogeneity of the ${T_c}^{max}$ in the bridge was analyzed from experimental results of Scanning Laser Microscopy (SLM) near the superconducting transition. The local transport and screening current in the bridge were also investigated using Scanning Hall Probe Microscopy (SHPM). A series of line scans of SLM of the GdBCO and YBCO sample showed that lines with more inhomogeneous distributions of ${\delta}V$ had more inhomogeneous distributions of ${T_c}^{max}$. The defect of the superconducting layer of the GdBCO sample caused by damage to the substrate affected the current flow. And we could analyze the redistribution of the current density using SLM and SHPM.

Development of Multi-Laser Vision System For 3D Surface Scanning (3 차원 곡면 데이터 획득을 위한 멀티 레이져 비젼 시스템 개발)

  • Lee, J.H.;Kwon, K.Y.;Lee, H.C.;Doe, Y.C.;Choi, D.J.;Park, J.H.;Kim, D.K.;Park, Y.J.
    • Proceedings of the KSME Conference
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    • pp.768-772
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    • 2008
  • Various scanning systems have been studied in many industrial areas to acquire a range data or to reconstruct an explicit 3D model. Currently optical technology has been used widely by virtue of noncontactness and high-accuracy. In this paper, we describe a 3D laser scanning system developped to reconstruct the 3D surface of a large-scale object such as a curved-plate of ship-hull. Our scanning system comprises of 4ch-parallel laser vision modules using a triangulation technique. For multi laser vision, calibration method based on least square technique is applied. In global scanning, an effective method without solving difficulty of matching problem among the scanning results of each camera is presented. Also minimal image processing algorithm and robot-based calibration technique are applied. A prototype had been implemented for testing.

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3D Scanning Embedded System Design (3D 스캐닝 임베디드 시스템 설계)

  • Hong, Seonhack;Cho, Kyungsoon
    • Journal of the Korea Society of Digital Industry and Information Management
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    • v.13 no.4
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    • pp.49-56
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    • 2017
  • It is the approach of embedded system design that finds 3D scanning technology to analyze a real object or environment to collect data on its shape and appearance. 3D laser scanning developed during the last half of 20th century in an attempt to accurately recreate the surfaces of various objects. 1960s, early scanners used lights, cameras, and projectors to carry out the scanning in the lacks of performance which encountered many difficulties with shiny, mirroring, or transparent objects. The 3D scanning technology has leveled-up with helpful of embedded software platform research and design. In this paper, First we designed the hardware of laser/camera setup and turntable moving part which is the base of object. Second, we introduced the process of scanning 3D data with software and analyzed the resulting scanned image on the web server. Last, we made the 3D scanning embedded device with 3D printing model and experimented the 3D scanning performance with Raspberry Pi.

Laser Processing for Manufacturing Styrofoam Pattern (주물용 스티로폼 목형 제작을 위한 레이저 가공 공정 개발)

  • 강경호;김재도
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.1085-1088
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    • 2001
  • The process of styrofoam pattern that has been used for material of press die pattern depends chiefly on handwork. Laser manufacturing system developed to increase precision and efficiency of process that is also able to convert the design easily. Applying the RP(rapid prototyping) concept reversely, the unnecessary part of section is vapored away by heat source of laser beam after converting 3-D CAD model into cross-sectional shape information. Laser beam is line-scanned in plane specimens to measure the depth and width of cut, surface roughness, cross-sectional shape as converting laser power, scanning speed, cutting gas pressure. With these basic data, plane surface, inclined surface, hole, outer contour trimming process is experimented and optimum condition are obtained. In plane and inclined surface experiments, 15W laser power and 50mm/s scanning speed make superior processing property and 30W, 10mm/s make processing efficiency increase in trimming process. With these results, simple patterns were manufactured and the possibility of applying laser manufacturing system to styrofoam pattern was convinced.

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Building Extraction and 3D Modeling from Airborne Laser Scanning Data

  • Lee, Jeong-Ho;Han, Soo-Hee;Byun, Young-Gi;Yu, Ki-Yun;Kim, Yong-Il
    • Korean Journal of Remote Sensing
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    • v.23 no.5
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    • pp.447-453
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    • 2007
  • The demand for more accurate and realistic 3D urban models has been increasing more and more. Many studies have been conducted to extract 3D features from remote sensing data such as satellite images, aerial photos, and airborne laser scanning data. In this paper a technique is presented to extract and reconstruct 3D buildings in urban areas using airborne laser scanning data. Firstly all points in a building were divided into some groups by height difference. From segmented laser scanning data of irregularly distributed points we generalized and regularized building boundaries which better approximate the real boundaries. Then the roof points which are subject to the same groups were classified using pre-defined models by least squares fitting. Finally all parameters of the roof surfaces were determined and 3D building models were constructed. Some buildings with complex shapes were selected to test our presented algorithms. The results showed that proposed approach has good potential for reconstructing complex buildings in detail using only airborne laser scanning data.

3D BUILDING RECONSTRUCTION FROM AIRBORNE LASER SCANNING DATA

  • Lee, Jeong-Ho;Han, Soo-Hee;Yu, Ki-Yun;Kim, Yong-Il
    • Proceedings of the KSRS Conference
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    • pp.587-590
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    • 2007
  • The demand for more accurate and realistic 3D urban models has been increasing more and more. Many studies have been conducted to extract 3D features from remote sensing data such as satellite images, aerial photos, and airborne laser scanning data. In this paper a technique is presented to extract and reconstruct 3D buildings in urban areas using airborne laser scanning data. Firstly all points in a building were divided into some groups by height difference. From segmented laser scanning data of irregularly distributed points we generalized and regularized building boundaries which better approximate the real boundaries. Then the roof points which are subject to the same groups were classified using pre-defined models by least squares fitting. Finally all parameters of the roof surfaces were determined and 3D building models were constructed. Some buildings with complex shapes were selected to test our presented algorithms. The results showed that proposed approach has good potential for reconstructing complex buildings in detail using only airborne laser scanning data.

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Low-Complexity Handheld 3-D Scanner Using a Laser Pointer (단일 레이저 포인터를 이용한 저복잡도 휴대형 3D 스캐너)

  • Lee, Kyungme;Lee, Yeonkyung;Park, Doyoung;Yoo, Hoon
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.64 no.3
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    • pp.458-464
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    • 2015
  • This paper proposes a portable 3-D scanning technique using a laser pointer. 3-D scanning is a process that acquires surface information from an 3-D object. There have been many studies on 3-D scanning. The methods of 3-D scanning are summarized into some methods based on multiple cameras, line lasers, and light pattern recognition. However, those methods has major disadvantages of their high cost and big size for portable appliances such as smartphones and digital cameras. In this paper, a 3-D scanning system using a low-cost and small-sized laser pointer are introduced to solve the problems. To do so, we propose a 3-D localization technique for a laser point. The proposed method consists of two main parts; one is a fast recognition of input images to obtain 2-D information of a point laser and the other is calibration based on the least-squares technique to calculate the 3-D information overall. To verified our method, we carry out experiments. It is proved that the proposed method provides 3-D surface information although the system is constructed by extremely low-cost parts such a chip laser pointer, compared to existing methods. Also, the method can be implemented in small-size; thus, it is enough to use in mobile devices such as smartphones.