• Title/Summary/Keyword: Galvano scanner

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A Study of Roughness Measurement of Rock Discontinuities Using a Confocal Laser Scanning Microscope (콘포컬 레이저 현미경을 이용한 불연속면의 거칠기 측정 연구)

  • Byung Gon Chae;Jae Yong Song;Gyo Cheol Jeong
    • The Journal of Engineering Geology
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    • v.12 no.4
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    • pp.405-419
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    • 2002
  • Fracture roughness of rock specimens is observed by a new confocal laser scanning microscope (CLSM; Olympus OLS1100). The wave length of laser is 488 nm, and the laser scanning is managed by a light polarization method using two galvano-meter scanner mirrors. The function of laser reflection auto-focusing enables us to measure line data fast and precisely. The system improves resolution in the light axis (namely z) direction because of the confocal optics. Using the CLSM, it is Possible to measure a specimen of the size up to $10{\;}{\times}{\;}10{\;}cm$ which is fixed on a specially designed stage. A sampling is managed in a spacing $2.5{\;}\mu\textrm{m}$ along x and y directions. The highest measurement resolution of z direction is $10{\;}\mu\textrm{m}$, which is more accurate than other methods. Core specimens of coarse and fine grained granite are provided. Fractures are artificially maneuvered by a Brazilian test method. Measurements are performed along three scan lines on each fracture surface. The measured data are represented as 2-D and 3-D digital images showing detailed features of roughness. Line profiles of the coarse granites represent more frequent change of undulation than those of the fine granite. Spectral analyses by the fast Fourier transform (FFT) are performed to characterize the roughness data quantitatively and to identify influential frequency of roughness. The FFT results suggest that a specimen loaded by large and low frequency energy tends to have high values of undulation change and large wave length of fracture roughness.

Basic Experimental Investigations to UV Laser Micro-Machining of Nano-Porous Alumina Ceramic Material (나노 다공 구조를 가진 알루미나 재료의 UV 레이저 미세가공에 관한 실험적 기초 연구)

  • Shin, Bo-Sung;Lee, Jung-Han
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.11 no.1
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    • pp.62-67
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    • 2012
  • Recently UV laser is widely used to process micro parts using various materials such as polymers, metals and ceramics because it has a very high intensity at the focused spot area. It is generally known that there are still some difficulties for alumina($Al_2O_3$) ceramics to directly make micro patterns like holes and lines on the surface of working material using 355nm UV laser because the alumina has a very low absorption coefficient at that wavelength. But nowadays new alumna with nano-porous holes is developed and applied to advanced micro functional parts of IT, BT and BT industries. In this paper, we are going to show the mechanism of photo-thermal ablation for nano-porous ceramics. Inside hole there is a lot of multiple reflections along the depth of hole. Experimentally we can find the micro hole drilling and micro grooving on the surface of nano-porous alumina.

High-speed angular-scan pulse-echo ultrasonic propagation imager for in situ non-destructive evaluation

  • Abbas, Syed H.;Lee, Jung-Ryul
    • Smart Structures and Systems
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    • v.22 no.2
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    • pp.223-230
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    • 2018
  • This study examines a non-contact laser scanning-based ultrasound system, called an angular scan pulse-echo ultrasonic propagation imager (A-PE-UPI), that uses coincided laser beams for ultrasonic sensing and generation. A laser Doppler vibrometer is used for sensing, while a diode pumped solid state (DPSS) Q-switched laser is used for generation of thermoelastic waves. A high-speed raster scanning of up to 10-kHz is achieved using a galvano-motorized mirror scanner that allows for coincided sensing and for the generation beam to perform two-dimensional scanning without causing any harm to the surface under inspection. This process allows for the visualization of longitudinal wave propagation through-the-thickness. A pulse-echo ultrasonic wave propagation imaging algorithm (PE-UWPI) is used for on-the-fly damage visualization of the structure. The presented system is very effective for high-speed, localized, non-contact, and non-destructive inspection of aerospace structures. The system is tested on an aluminum honeycomb sandwich with disbonds and a carbon fiber-reinforced plastic (CFRP) honeycomb sandwich with a layer overlap. Inspection is performed at a 10-kHz scanning speed that takes 16 seconds to scan a $100{\times}100mm^2$ area with a scan interval of 0.25 mm. Finally, a comparison is presented between angular-scanning and a linear-scanning-based pulse-echo UPI system. The results show that the proposed system can successfully visualize defects in the inspected specimens.

Continuous Scanning Method for Improvement of Precision and Fabrication Efficiency of Two-Photon Stereolithography (연속적 스캐닝 방법을 이용한 이광자 광중합 공정의 제작 속도 및 정밀도 개선에 관한 연구)

  • Lim, Tae-Woo;Son, Yong;Yang, Dong-Yol;Kong, Hong-Jin;Lee, Kwang-Sup;Park, Sang-Hu
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.5
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    • pp.396-401
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    • 2008
  • Minimization of processing time in two-photon stereolithography (TPS) has been one of important issues. Generally, a voxel scanning method (VSM) has been used in TPS because the method is very profitable for the stable fabrication irrespective of jittering and response time of scanning equipments such as a stage and a galvano-scanner. However, supplementary processing time due to the on/off control of a shutter for the generation of each voxel is required inevitably in VSM; by this reason, much processing time takes to fabricate largescale micropatterns and three-dimensional patterns. In this work, a continuous scanning method (CSM), generating patterns by movement of beam focus with a constant speed, is proposed for the improvements of scanning speed and precision in TPS. Some line patterns are fabricated by each scanning method to demonstrate the usefulness of CSM with viewpoints of scanning speed and precision.

A Study on the Fabrication of Laser-Induced Graphene Humidity Sensor for Mounting on a Disposable Mask (일회용 마스크에 장착을 위한 레이저 기반 그래핀 습도센서 제작에 관한 연구)

  • Lee, Jun-Uk;Shin, Yun-Ji;Yang, Hye-Jeong;Shin, Bo-Sung
    • Journal of the Korean Society of Industry Convergence
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    • v.23 no.4_2
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    • pp.693-699
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    • 2020
  • 355nm UV pulse laser is irradiated on the surface of polyimide (PI) by LDW (Laser Direct Writing) method to produce a high sensitivity flexible humidity sensor using a simple one-step process. The LDW method continuously investigates 2-D CAD data using a galvano scanner and an F-lens. This method is non-contact, so it minimizes physical strain on the PI. Laser-induced graphene (LIG) produced by lasers has a high surface area due to its high flexibility and numerous pores and oxidizers compared to conductors. For this reason, it is highly useful as a flexible humidity sensor. The humidity sensor produced in this study was attached to the inside of a mask filter, which has become a hot topic recently, and its applicability was confirmed.The measurement of humidity measured the sensitivity, reactivity, stability and recovery behavior of the sensor by measuring changes in capacitance and resistance.