• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.5
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• pp.227-234
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• 2018

Researches regarding measurement and control of the dynamic behavior of liquid such as sloshing have been actively on undertaken in various engineering fields. Liquid vibration is being measured in the study of tuned liquid dampers(TLDs), which attenuates wind motion of buildings even in building structures. To overcome the limitations of existing wave height measurement sensors, a method of measuring liquid vibration in a TLD using a laser Doppler vibrometer(LDV) and galvanometer scanner is proposed in this paper: the principle of measuring speed and displacement is discussed; a system of multi-point measurement with a single point of LDV according to the operating principles of the galvanometer scanner is established. 4-point liquid vibration on the TLD is measured, and the time domain data of each point is compared with the conventional video sensing data. It was confirmed that the waveform is transformed into the traveling wave and the standing wave. In addition, the data with measurement delay are cross-correlated to perform singular value decomposition. The natural frequencies and mode shapes are compared using theoretical and video sensing results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10B
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• pp.1117-1123
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• 2009

Head fixed type multi-focus display system using Galvano-scanner and DMD(Digital Micro-mirror Device), which is able to perfectly accommodate, can solve eye fatigue due to conflict between convergence eye movement and accommodation action in stereoscopic display. This system is able to accommodate through making convergence point about each view point and offering it in front of observer's pupil by using laser scanning method. In this paper, we analyzed laser scanning method of this multi-focus display system. And multi-focus display system based on this analysis was made, which showed that focus adjustment was possible through video camera. As a result, formation principle of view point of multi-focus system by laser scanning method was verified.

• Laser Solutions
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• v.16 no.1
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• pp.10-14
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• 2013

Remote laser beam welding (RLW) has the benefits of high speed and high quality welding, especially as applied to automotive industry. RLW is designed in a way that end effecter and head of scanner move simultaneously, and require the compensation for the motion of end effecter in order to weld proper position. In this paper, we show the algorithms of RLW that enable the end effecter to synchronize with scanner based on time. The proposed method consists of two algorithms. These algorithms make it possible for the moving end effecter to weld on desired place. The effectiveness of the algorithms is shown by experiments.

• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.145-148
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• 1986

To perform the marking on metal with high speed and non-contact using the laser beam of high energy, laser marking system is designed and fabricated applying the galvanometer scanner capable of high speed-precise beam positioning controlled by microprocessor. Laser is a Q-switched Nd:YAG producing multi-mode, wavelength, 1060nm. Optical system is composed of beam expander, scanning mirror and flat field lens. Consequently, the laser marking is satisfactorily achieved regardless of kinds of metal.

• 기계와재료
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• v.21 no.2
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• pp.146-155
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• 2009

본고에서는 레이저 가공의 시대적 요구사항인 고속화와 대면적화에 부응하기 위한 고속 레이저 가공 및 장비 핵심기술의 개발 동향을 분석하고자 한다. 여기서, 고속 레이저 가공기술은 갈바노 모터를 사용하는 고속 스캐너(scanner)와 정밀 스테이지를 연동하여 대면적 제품을 연속으로 가공하는 기술을 말하며 FPD 공정, 태양전지가공, 리모트용접 공정 등에 대표적으로 적용된다. 본고에서는 최근 한국기계연구원에서 개발하고 있는 고속 레이저 가공 및 장비 핵심기술 관련 연구개발 내용도 일부 소개하고자 한다.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.2
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• pp.25-28
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• 2010

The micro fabrication on the mold material using picosecond laser ablation processing has been studied. We used the two kind of system with picosecond laser. First one is two mirror type scanner and telecentric f-theta lens. Second one is X-Y stage and objective lens. By using these system, the $100{\mu}m$ size chess patterning and $2{\mu}m$ size patterning was fabricated. Especially $2{\mu}m$ size patterning on the mold material can be used as the decorative rainbow color logo for industrial field. In this paper, it is proved the picosecond laser is effective tool for the laser ablation processing.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.5
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• pp.70-75
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• 2010

In this paper, laser marking systems dedicated to cylinderical parts was developed. We first develop the marking device which consists of Nd-Yag laser, galvano scanner and additional rotational axis, then develop algorithm for supporting the digital image with bmp data format. Additional rotational axis is so attached as to rotate the cylinderical parts for marking its whole surface. The image is separated into line by line and the separated line image is sent to galvano scanner while rotating the additional axis simultaneously. CxImage library, famous open source code, is employed for the image processing. The developed method was tested with various images and shows that it reduces marking time significantly without reducing marking quality.

• 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.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.109-109
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• 2009

최근 유럽의 완성차 업체에서 조립라인에 적용을 시작하고 있는 레이저 원격 용접기술은 저항 점용접에서의 문제점들을 동시에 해결하고 작업 시간을 획기적으로 감소시켜 생산성을 향상시킬 수 있는 용접공정으로 떠오르고 있다. 레이저 원격 용접기술은 레이저 빔을 용접부의 원거리에서 조사하여 용접하는 기술로서 레이저의 초점거리와 갈바노미터의 고속 이송를 이용한 최첨단 용접공정이다. 높은 생산성을 유지 하기 위하여 정확한 용접 컨트롤이 필요하지만, 레이저 용접의 경우 용접시 안전 문제로 육안으로 관찰하기가 힘들다. 이러한 문제를 해결하기 위하여 모니터링이 필수적이다. 기존의 레이저 모니터링으로는 음향 센서를 이용하여 음향을 측정하는 방법이나 UV 센서, IR 센서 등의 빛을 이용한 방법이 많이 사용되어왔다. 하지만 이 방법들은 간접적인 방법들로 노이즈에 민감하고 또 설치가 까다로운 단점이 있었다. 본 연구에서는 CCD 카메라를 이용하여 시스템의 복잡함을 줄이고 더 정확하고 빠르게 용접 현상을 관찰하기 위하여 동축 모니터링 시스템을 이용하였으며, 이를 통해 Keyhole을 관찰하고 센서를 이용한 용접 변수(레이저 출력, 용접 속도 등)의 변화에 따른 용접 현상을 규명하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.346-351
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• 2018

Metal three-dimensional (3D) printing technologies are mainly classified as powder bed fusion (PBF) and direct energy deposition (DED) methods according to the method of application of a laser beam to metallic powder. The DED method can be used to fabricate fine and hard 3D metallic structures by applying a strong laser beam to a thin layer of metallic powder. The PBF method involves slicing 3D graphics to be a certain height, laminating metal powders, and making a 3D structure using a laser. While the DED method has advantages such as laser cladding and metallic welding, it causes problems with low density when 3D shapes are created. The PBF method was introduced to address the structural density issues in the DED method and makes it easier to produce relatively dense 3D structures. In this paper, thin lines were produced by using PBF 3D printers with stainless-steel powder of roughly $30{\mu}m$ in diameter with a galvano scanner and fiber-transferred Nd:YAG laser beam. Experiments were carried out to find the optimal conditions for the width of a line depending on the processing times, laser power, spot size, and scan speed. The optimal conditions were two scanning processes in one line structure with a laser power of 30 W, spot size of $28.7{\mu}m$, and scan speed of 200 mm/s. With these conditions, a minimum width of about $85.3{\mu}m$ was obtained.