• Title, Summary, Keyword: Laser scanning

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Multiple crack evaluation on concrete using a line laser thermography scanning system

  • Jang, Keunyoung;An, Yun-Kyu
    • Smart Structures and Systems
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    • v.22 no.2
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    • pp.201-207
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    • 2018
  • This paper proposes a line laser thermography scanning (LLTS) system for multiple crack evaluation on a concrete structure, as the core technology for unmanned aerial vehicle-mounted crack inspection. The LLTS system consists of a line shape continuous-wave laser source, an infrared (IR) camera, a control computer and a scanning jig. The line laser generates thermal waves on a target concrete structure, and the IR camera simultaneously measures the corresponding thermal responses. By spatially scanning the LLTS system along a target concrete structure, multiple cracks even in a large scale concrete structure can be effectively visualized and evaluated. Since raw IR data obtained by scanning the LLTS system, however, includes timely- and spatially-varying IR images due to the limited field of view (FOV) of the LLTS system, a novel time-spatial-integrated (TSI) coordinate transform algorithm is developed for precise crack evaluation in a static condition. The proposed system has the following technical advantages: (1) the thermal wave propagation is effectively induced on a concrete structure with low thermal conductivity of approximately 0.8 W/m K; (2) the limited FOV issues can be solved by the TSI coordinate transform; and (3) multiple cracks are able to be visualized and evaluated by normalizing the responses based on phase mapping and spatial derivative processes. The proposed LLTS system is experimentally validated using a concrete specimen with various cracks. The experimental results reveal that the LLTS system successfully visualizes and evaluates multiple cracks without false alarms.

Optical system design for laser scanning unit (Laser Scanning Unit용 광학계 설계)

  • 임천석
    • Korean Journal of Optics and Photonics
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    • v.10 no.1
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    • pp.15-20
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    • 1999
  • Laser Scanning Unit (LSU), which is one of the core parts of laser printer, consists of LD Module, cylinder lens, polygon mirror and f$\theta$ lens. After making an initial design on each part, we optimized the one which satisfies the user specification. The optimized optical system has diffraction limited performance for the slit size of 2.7 mm$\times$1.6 mm, f$\theta$ characteristics less than 0.3% and field curvature less 1.2 mm. We also calcurate tolerance of each part based on RSS(Root Sum Square) method to manufacture LSU for mass production.

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Optical Design of a Laser Scanning System Stable Against Wavelength and Temperature Variations (파장과 온도변화에 안정한 레이저 주사광학계 설계)

  • Kim, Da Ae;Lee, Jong-Ung
    • Korean Journal of Optics and Photonics
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    • v.27 no.1
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    • pp.32-40
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    • 2016
  • The characteristics of an optical system vary depending on wavelength and ambient temperature. Based on the thin-lens approximation, we investigate the conditions for stabilizing an optical system against wavelength and temperature variations at the same time. The conditions are applied to designing a laser scanning system consisting of two lenses. The change in the effective focal length of the scanning system against wavelength and temperature variations is very small, as expected.

A Study on the Curvature Correction in Laser Scanner (레이저 주사 장치의 곡률 보정에 관한 연구)

  • Yun, N.I.;Kim, N.;Park, H.K.
    • Proceedings of the Korean Institute of Communication Sciences Conference
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    • pp.194-197
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    • 1986
  • In this paper, for the curvature correction on the scanning plane in laser scanning system, aberration correction method using holographic optical element is suggested. Holoens is selected as a type of holographic zone plate which has aberration correction property. And hologram recording condition is analyzed to find fo property. This hololens is implemented by computer-generated hologram technique. Laser scanning system is organized using desinged hololens and scanning properties of this system are investigated. Using this method optical system structure in laser scanning system can be simplified satisfying both scan linearity and field flatness.

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Laser Scanning Instrumentation Technique for Movement of Excavation (Laser Scanning을 활용한 지반굴착 및 주변 구조물 거동관측)

  • Cho, Seong-Ha;You, Kwang-Ho
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.165-173
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    • 2005
  • Generally, the instrumentation scheme for urban excavation projects consist of a series of tools such as inclinometer piezometer, loadcell, tiltmeter etc. Because almost every equipments are placed along several typical lines, it is impossible to evaluate the whole behavior of structures and adjacent buildings simultaneously. With laser scanning technique developed for surveying, all visible structures are scanned in the form of 3D digital data in a time schedule as planned. It can be analysed effectively the movements for all area affected by excavation even the spots in where no instrumentation tools. Although there are some parts to be refined such as scanning error, proper analysing software, it gives many advantages for realistic instrumentation works in the near future.

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Effect of Laser Scanning Speed on the Laser Direct Patterning of T-shaped Indium Tin Oxide (ITO) Electrode for High Luminous AC Plasma Display Panels (고효율 플라즈마 디스플레이 패널을 위한 T-형 ITO 전극의 레이저 직접 패터닝시 레이저 스캔 속도의 영향)

  • Li, Zhao-Hui;Cho, Eou-Sik;Kwon, Sang-Jik
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.2
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    • pp.133-136
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    • 2010
  • Laser direct patterning is one of new methods which are able to replace a conventional photolithography. In order reduce the fabrication cost and to improve the luminous efficiency of AC plasma display panels (PDPs), in this experiment, a Q-switched Nd:$YVO_4$ laser was used to fabricate T-shaped indium tin oxide (ITO) display electrodes. For the laser beam scanning speed from 100 mm/sec to 800 mm/sec, T-shaped ITO patterns were clearly obtained and investigated. The experimental results showed that the optimized T-shaped ITO electrode was obtained when the lasers scanning speed was 300 mm/s.

A Study on the Shape Correction of Stamped Parts by the Irradiation of Laser (레이저를 이용한 스탬핑 제품의 스프링백 형상교정에 관한 연구)

  • Shim, H.B.;Kim, D.W.
    • Transactions of Materials Processing
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    • v.18 no.7
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    • pp.519-530
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    • 2009
  • The study is concerned with shape correction of stamped product using the laser irradiation. As a fundamental study, laser irradiation process has been analyzed through the thermo-mechanical FE analysis. For the purpose of validation, laser scanning experiment has been carried out also. Since the deformation mechanism involved in the laser scanning is extremely complicated due to the highly temperature dependent material properties, the determination of laser scanning pattern is not easy for the application of real stamped parts. A simplified method for the application of springback correction has been suggested with the thermo-mechanical FE analysis.

Laser-induced Thermochemical Wet Etching of Titanium for Fabrication of Microstructures (레이저 유도 열화학 습식에칭을 이용한 티타늄 미세구조물 제조)

  • 신용산;손승우;정성호
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.4
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    • pp.32-38
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    • 2004
  • Laser-induced thermochemical wet etching of titanium in phosphoric acid has been investigated to examine the feasibility of this method fur fabrication of microstructures. Cutting, drilling, and milling of titanium foil were carried out while examining the influence of process parameters on etch width, etch depth, and edge straightness. Laser power, scanning speed of workpiece, and etchant concentration were chosen as major process parameters influencing on temperature distribution and reaction rate. Etch width increased almost linearly with laser power showing little dependence on scanning speed while etch depth showed wide variation with both laser power and scanning speed. A well-defined etch profile with good surface quality was obtained at high concentration condition. Fabrication of a hole, micro cantilever beam, and rectangular slot with dimension of tess than 100${\mu}{\textrm}{m}$ has been demonstrated.

3D Extraction Method Using a Low Cost Line Laser (라인레이저를 이용한 3D 모델 추출 방법)

  • Yun, Chun Ho;Kim, Tae Gi;Cho, Yong Wook;Nam, Gi Won;Yim, Choong Hyuk
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.26 no.1
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    • pp.108-113
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    • 2017
  • In this paper, we proposed a three-dimensional(3D) scanning system based on laser vision technique for 3D model reconstruction. The proposed scanning system consists of line laser, camera, and turntable. We implemented the 3D scanning system using low quality elements. Although these are low quality elements, we reduced the 3D data reconstruction errors greatly using two methods. First, we developed a maximum brightness detection algorithm. This algorithm extracts the maximum brightness of the line laser to obtain the shape of the object. Second, we designed a new laser control device. This device helps to adjust the relative position of the turntable and line laser. These two methods greatly reduce the measuring noise. As a result, point cloud data can be obtained without complicated calculations.