• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2003년도 추계종합학술대회
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• pp.868-871
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• 2003

본 논문은 Laser의 특성인 단색성(monochromaticity), 지향성(directivity), 간섭성(interference), 에너지 집중도 및 고휘도(brightness), 위상의 균일성(응집도, coherence) 등을 이용한 여러 응용 중에서 거리측정에 관한 것이며, Laser를 이용한 거리측정은 빛의 파장, 빛의 진직성, 삼각측량, 변조 빛의 파장에 의한 방법 등이 있다. 본 논문에서는 기존의 삼각측량법을 개선한 삼각측량법으로 일정한 거리에 위치한 두 개의 Laser를 CPU가 0-90$^{\circ}$ 까지 Laser 각도를 움직여 측정 대상 물체에 비춰지는 상을 가지고 거리를 측정한다. Laser의 정확한 각도제어, 빠른 거리 계산, 필요에 따라 이미지 처리까지 필요함으로 Intel사의 고성능 마이크로 프로세서인 SrongArm (SA1110)을 기반으로 한 하드웨어를 구상하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.129-132
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• 1996

Surface modification like cone formation on Pulsed laser deposition (PLD) occurs in YBCO target surface irradiated by laser beam. Cone formation results in a reduction of deposition rate, so that it is significant obstacles to an efficient deposition process. With the change of various conditions such as the number of laser shot, target density, direction of incoming laser beam, we have systematically analyzed the modification of target surface. Because cones formed by beam-target interactions grow in direction of incoming laser beam, we have used the method of rotating the target position by 180$^{\circ}$ with the same number and position of laser shot. Experimental results of losing the directionality and changing the shape of cones formed on laser irradiated YBCO target surface is obtained by the SEM image. Also, we have observed that the size of cones formed on target by pulsed laser became larger with increasing the number of laser shots.

• 소성∙가공
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• 제18권3호
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• pp.262-267
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• 2009

Selective laser sintering is a kind of rapid prototyping process whereby a three-dimensional part is built layer wise by laser scanning the powder. This process is highly influenced by powder and laser parameters such as laser power, scan rate, fill spacing and layer thickness. Therefore a study on fabricating Fe-Ni-Cr powder by selective laser sintering has been performed. In this study, fabrication was performed by experimental facilities consisting of a 200W fiber laser which can be focused to 0.08mm and atmospheric chamber which can control atmospheric pressure with argon. With power increase or energy density decrease, line width was decreased and line surface quality was improved with energy density increase. Surface quality of quadrangle structure was improved with fill spacing optimization.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.667-668
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• 2006

Usually nanosecond pulsing laser ablation of metal is under thermal effect. Many studies of the theoretical analysis and modeling to predict a result of laser ablation of metal are suggested on the basis of the photothermal mechanism. In this paper, we investigate the etching depth and laser fluence of laser ablation of copper films. We proposed the simplified SSB Model(Srinivasan-Smrtic-Babudp model) to study the photothermal effect of nanosecond pulsing laser ablation of copper thin metal. The experimental results were obtained by using the 355nm DPSS $Nd:YVO_4$ laser.

• 한국레이저가공학회지
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• 제2권2호
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• pp.8-17
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• 1999

This study includes a basic feature of laser surface alloying for enhancing the surface properties of materials. Effects of laser processing parameters such as beam power, beam size, scanning speed on the shape and composition of alloyed layer was simulated in case of moving beam conditions (2-dimensional numerical methods). Simulated results were compared with experiments, in which the plasma coating of 80% Ni ＋ 20% Cr deposited on the SS41 substrate was remelted with CO2 laser with Gaussian energy distribution. Simulation and experiments revealed that the shape (dimension)and composition of laser alloyed layer were strongly dependent upon the process parameters, especially interaction time (travel speed) as compared to beam diameter, beam power and absorptivity. The shape and composition of alloyed layervaried more or less exponentially with parameters.

• 한국레이저가공학회지
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• 제12권4호
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• pp.17-25
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• 2009

The surface cleaning method based on the laser-induced breakdown (LIB) of gas and subsequent plasma and shock wave generation can remove small particles from solid surfaces. In the laser shock cleaning (LSC) process, a high-power laser pulse induces optical breakdown of the ambient gas above the solid surface covered with contaminant particles. The subsequently created shock wave followed by a high-speed flow stream detaches the particles. In this work, a novel surface cleaning process using laser-induced breakdown of liquid is introduced and demonstrated. LIB of a micro liquid jet increases the shock wave intensity and thus removes smaller particle than the conventional LSC method. Experiments demonstrate that the cleaning force and cleaning efficiency are also increased significantly by this method.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1991년도 춘계학술대회 논문집
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• pp.321-327
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• 1991

High power laser beams are used in a wide variety of materials processing applications such as cutting, welding, drilling and surface treatment. The CO$\sub$2/ laser is increasingly used in laser beam welding because of the highly potential advantages. High power laser welding is a high energy density, no filler metals and low heat input process to join metals. As the comparison with the conventiona welding, precision work and good fit-up to join the metals are required and maintenance is expensive at present. The principal variables of laser beam welding are the laser beam power, travel speed and bean spot size. The penetration depth during laser beam welding is directly related to the power density of the laser beam. Generally, for a constant beam size, the penetration depth increases with increasing laser beam power.

• 한국정밀공학회지
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• 제24권4호
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• pp.147-152
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• 2007

UV laser ablation of polyimide is a combination of photochemical and photothermal mechanism. Photochemical mechanism is that molecular bonds are broken by photon energy and photothermal is evaporation and melt expulsion. When the laser processing, the etching depth needs to be calculated for prediction of processing result. In this paper, in order to predict the laser etching depth of polyimide by UV laser with the wavelength of 355nm, the theoretical model which includes both the photothermal and the photochemical effect was introduced. The model parameters were obtained by comparing with experimental results. The 3rd harmonic $Nd:YVO_4$ laser system was used in the experiment. From these experimental and theoretical results, the laser ablation of a polyimide was verified to achieve the highest quality microstructure.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2009년도 춘계학술발표회 논문집
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• pp.65-73
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• 2009

The terrestrial laser scanner measures the signal delay time of electronic circuit in EDM(Electronic Distance Measurement) Module for distance measurement. To measure signal delay time precisely, transmitting laser beam of terrestrial laser scanner is divided optically. Therefore, 10% of the laser beam power is entered into the electronic circuit and the others go out through lens. But, measure of delay time is severe in the laser scanner system that the laser beam power is changed dynamically by reflectance of a object, because characters like gain of electronic circuit involving APD(Avalanche Photo Diode) and so on are changed by incident laser beam. Therefore, we adapt ND(Neutral Density) filter that has grid pattern to the laser scanner system to keep constant the incident laser beam power. In this paper, we propose the simulation program for efficient design of ND filter pattern. Finally, to affirm simulation program, we conduct the experimental test of simulated ND filter that has linearly transmittance change, and we consider the experiment result.

• 한국세라믹학회지
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• 제36권4호
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• pp.417-424
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• 1999

Laser lapping of diamond films is performed with focused beam of copper vapor laser. Both spherical and rod-shape laser beam are used. Diamond surface is scanned at various scan speeds(0,125, 0.5, 0.75 mm/sec) and baem shifts (5, 10, 20, 40, 100$\mu\textrm{m}$) At 0.125 mm/sec 10$\mu\textrm{m}$ scan condition the level difference of di-amond surface of about 700$\mu\textrm{m}$ over 20 mm is reduced to 200$\mu\textrm{m}$ In addition surface roughness is also im-proved from 3.53$\mu\textrm{m}$ to 2.47$\mu\textrm{m}$ at 5$\mu\textrm{m}$ beam shift. But at higher beam shift than 10$\mu\textrm{m}$ laser scan makes the surface rougher which is considered to be due to the non uniform spatial distribution of laser en-ergy. It is concluded that homogenized laser beam with high average power is needed for large area laser lapping of diamond films at appreciable rates.