• 대한기계학회논문집B
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• 제29권1호
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• pp.110-115
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• 2005

A novel technique for fine particle beam focusing under the atmospheric pressure is introduced using a radiation pressure assisted aerodynamic lens. To introduce the radiation pressure in the aerodynamic focusing system, a 25m plano-convex lens having 2.5mm hole at its center is used as an orifice. The particle beam width is measured for various laser power, particle size, and flow velocity. In addition, the effect of the laser characteristics on the beam focusing is evaluated comparing an optical tweezers type and pure gradient force type. For the pure aerodynamic focusing system, the particle beam width was decreased as increasing particle size and Reynolds number. Using the optical tweezers type, the particle beam width becomes smaller than that of the pure aerodynamic focusing system about $16\%,\;11.4\%\;and\;9.6\%$ for PSL particle size of $2.5{\mu}m,\;1.0{\mu}m,\;and\;0.5{\mu}m$, respectively. Particle beam width was minimized around the laser power of 0.2W. However, as increasing the laser power higher than 0.4W, the particle beam width was increased a little and it approached almost a constant value which is still smaller than that of the pure aerodynamic focusing system. For pure gradient force type, the reduction of the particle beam width was smaller than optical tweezers type but proportional to laser power. The radiation pressure effect on the particle beam width is intensified as Reynolds number decreases or particle size increases relatively.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1505-1509
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• 2004

A novel technique for fine particle beam focusing under the atmospheric pressure is introduced using a radiation pressure assisted aerodynamic lens. To introduce the radiation pressure in the aerodynamic focusing system, a 25 mm plano-convex lens having 2.5 mm hole at its center is used as an orifice. The particle beam width is measured for various laser power, particle size, and flow velocity. In addition, the effect of the laser characteristics on the beam focusing is evaluated comparing an Ar-Ion continuous wave laser and a pulsed Nd-YAG laser. For the pure aerodynamic focusing system, the particle beam width was decreased as increasing particle size and Reynolds number. For the particle diameter of 0.5 ${\mu}m$, the particle beam was broken due to the secondary flow at Reynolds number of 694. Using the Ar-Ion CW laser, the particle beam width becomes smaller than that of the pure aerodynamic focusing system about 16 %, 11.4 % and 9.6 % for PSL particle size of 2.5 ${\mu}m$, 1.0 ${\mu}m$, and 0.5 ${\mu}m$ respectively at the Reynolds number of 320. Particle beam width was minimized around the laser power of 0.2 W. However, as increasing the laser power higher than 0.4 W, the particle beam width was increased a little and it approached almost a constant value which is still smaller than that of the pure aerodynamic focusing system. The radiation pressure effect on the particle beam width is intensified as Reynolds number decreases or particle size increases relatively. On the other hand, using 30 Hz pulsed Nd-YAG laser, the effect of the radiation pressure on the particle beam width was not distinct unlike Ar-Ion CW laser.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.256.1-256.1
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• 2014

21세기 정보화 시대의 도래와 함께 반도체 및 디스플레이 분야는 고부가가치산업으로 급격히 성장하였고, 현재까지도 미래의 지속적인 시장 창출을 위하여 기술개발과 투자로 초미세화, 고효율, 대면적화에 대한 원천기술 확보가 중요시되고 있다. 반도체 및 디스플레이의 대면적화가 진행됨에 따라 플라즈마 공정장비의 대면적화도 활발히 기술개발이 진행되고 있으며, 대면적화에 있어 플라즈마의 공간균일도는 생산수율 및 공정균일화를 위해 기본적으로 평가되어야 하는 중요한 지표가 되었다. 하지만 종래의 진단법들은 대면적 플라즈마 진단에 매우 제한적이기 때문에 본 연구에서는 대면적 플라즈마의 공간균일도 평가를 위해 플라즈마의 방출광 측정을 기초로 하는 진단계를 개발하였다. 플라즈마 방출광을 이용한 진단은 플라즈마에 섭동을 주지 않고 전자온도의 변화 및 공간균일도를 평가할 수 있다. 이 진단법은 두 마주보는 한쪽 면이 평평한 볼록렌즈(plano-convex lens)로 이루어진 수광시스템과 역변환 알고리즘을 통해 선 적분된 방출광으로부터 플라즈마 방출광의 국지적 정보를 측정하는 것이다. 플라즈마와 같이 크기가 큰 광원의 경우 렌즈 광학계에서 필연적으로 수반되는 선적분된(chord-integrated) 방출광을 제거하기 위해 구조에 따른 시스템 함수를 이용한 푸리에 변환 알고리즘을 개발하였고, 이를 통해 렌즈 초점거리의 정확한 방출광 세기만 재구성하였다. 이러한 재구성 방법을 이용하여 렌즈의 거리를 움직이며 대면적 플라즈마의 방출광 분포측정을 수행하였고, 이에 대한 결과를 발표하고자 한다.

• Journal of Welding and Joining
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• 제16권2호
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• pp.100-110
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• 1998

In this paper, the laser weldability of thin gage steels for automobile application is discussed. Welding was carried out with a high power carbon dioxide laser system, and the laser energy was concentrated through a plano-convex lens. Test results showed that the joint gap in the butt welding proved to be one of the critical conditions for an acceptable weld. In the case where the ratio of the gap clearance to the material thickness was slightly bigger than optimal value, the weld strength was reduced showing weld metal fracture. It was possible to obtained a weld penetration ratio of 0.91 when the vertical offset ratio was controlled to be 0.4 or smaller. Results also demonstrated that the weld strength of the lap joint was influenced by travel speed. At the travel speeds lower than 37 mm/s, the weld strength indicated higher value than that of class A recommendation strength of a resistance spot weld based on the KS code. It was clear that the complicated effect of specimen alignment should be considered so as to make a sound weld with high integrity when the laser process was applied to the long weld line.

• 한국광학회지
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• 제9권2호
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• pp.51-58
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• 1998

엄밀한 기하광학적 광선추적을 이용하여, 2차원 TPHK가 푸리에변환 렌즈로 사용될 때, 표면양각형태에 따른 특성을 분석하였다. 2차원 TPHK(F/8, 초점거리 15 mm)의 기판두께가 0, 50$\mu\textrm{m}$인 두 경우에 있어서, 표면양각형태를 평면-볼록면에서 볼록면-평면까지 51단계로 나누어, 세가지 입사각($0^{\circ},{2.5}^{\circ},5^{\circ}$)에 대한 광선추적을 실시하였다. 광선추적의 결과로 얻은 rms 스폿크기, $f{\sin}{\theta}$위치에 대한 rms편차, 최고점위치, FWHM(full width at half maximum), 추적에서 제외된 광선수 등을 평가 기준으로 사용하였는데, 그 결과, 기판의 유무에 무관하게, 표면양각높이의 80%가 상면 쪽에 존재하는 양볼록 형태를 가지는 TPHK가 푸리에변환 렌즈로서 가장 우수한 것으로 나타났다.

• 한국정밀공학회지
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• 제26권1호
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• pp.71-81
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• 2009

Die steel for plastic molding were used as mold material of automobile parts and electronic component industry. The material of this paper has superior to mechanical properties, such as repair weldability, corrosion resistance and high temperature strength, required mold parts for semitransparent. Laser-induced surface hardening technology is widely adopted to improver fatigue life and wear resistance via localized hardening at the surface of mold parts. The objective of this research work is to investigate on the characteristics of surface hardening of the laser process parameters, such as beam travel speed, laser power and defocsued spot position, for the case of die steel for plastic molding. Lens for surface hardening of large area is plano-convex type with elliptical profile to maintain uniform laser irradiation. According to the experimental results, large size of hardened layer at the surface of die steel for plastic molding was achieved, and microstructure of this layer was lath martensite. Optimal surface status and mechanical property of hardened layer could be obtained at 1095Watt, $0.25{\sim}0.3m/min$, 0mm (focal length: 232mm) for laser power, beam travel speed, and focal position. Where, heat input was $0.793{\times}10^{3}J/cm^2$, and width of hardened layer was 27.58mm.

• 한국광학회지
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• 제13권6호
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• pp.548-553
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• 2002

유도 브릴루앙 산란 위상공액 거울(SBS-PCM)을 이용한 Nd:YAG 레이저 발진기를 구성하고 특성을 조사하였다. SBS-PCM은 SBS-cell과 렌즈계의 조합으로 구성되어 있다. Q-switcher를 사용하지 않은 경우, SBS-cell이 SBS-PCM으로 작용하지 않은 것을 확인하였고, Cr:YAG(T=50%) Q-switcher가 사용된 경우는 SBS-cell이 SBS-PCM으로 작용하였다. 이 경우 에너지 출력특성은 SBS-PCM의 유무에 관계엾이 차이가 없으나, 출력의 빔프로파일은 크게 향상되었다. 이를 설명하기 위해 초평면에서의 세기에 따른 반사율차이를 이용한 간단한 공간주파수 여과모형을 제시하고 시뮬레이션 하였다.