• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.17-23
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• 2003

To show a retina shape and thickness on the computer monitor, a laser has been used in Scanning Laser Ophthalmoscope(SLO) equipment using the travelling difference. This method requires exact synchronous control of laser travelling in optic system to show a clear 3-dimensional image of retina. To obtain this image, this exact synchronism is very important for making the perfect plane scanning. In this study, a synchronous control of the galvanometer to make 3-dimensional retina image is presented. For the more, a very simple mathematical model of the galvanometer is approved by experimental result.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.102-110
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• 2006

We discuss two possibilities of using femtosecond pulse lasers as a new interferometric light source for enhanced precision surface-profile metrology. First, a train of ultra-fast laser pulses yields repeated low temporal coherence, which allows unequal-path scanning interferometry, which is not feasible with white light. Second, the high spatial coherence of femtosecond pulse lasers enables large-sized optics to be tested in nonsymmetric configurations with relatively small-sized reference surfaces. These two advantages are verified experimentally using Fizeau and Twyman-Green type scanning interferometers.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.204-207
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• 2005

We discuss two possibilities of using femtosecond pulse lasers as a new interferometric light source fer enhanced precision surface profile metrology. First, a train of ultra-fast laser pulses yields repeated low temporal coherence, which allows performing unequal-path scanning interferometry that is not feasible with white light. Second, high spatial coherence of femtosecond pulse lasers enables to test large size optics in non-symmetric configurations with relatively small size reference surfaces. These two advantages are verified experimentally using Fizeau and Twyman-Green type scanning interferometers.

• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.246-249
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• 2000

An Fe$_{49}$ Co$_{49}$ V$_2$alloy is annealed in thermal annealing furnace at 50$0^{\circ}C$, 75$0^{\circ}C$, 80$0^{\circ}C$, and 90$0^{\circ}C$. Annealed samples were cooled in air. The magnetostriction is measured by using a Michelson laser interferometer. Receiving the feedback signal of interference, a mirror attached to piezoelectric transducer (PZT) maintains the optical path length (OPL) between two arms of laser interferometer relatively constant. The feedback voltage is calibrated to the OPL variation. A magnetostriction of 2$\times$10$^{-6}$ at H = 60 Oe increases up to 33.68$\times$10$^{-6}$ at an annealing temperature of 90$0^{\circ}C$, suggesting that the magnetostrictive characteristics are improved by the microstructural modification.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.7
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• pp.701-706
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• 2015

In this study, experimental and computer simulation results are compared and analyzed. Three-dimensional (3D) fabricated matrices from an MJM 3D printer were joined with poly-acetate thermoplastic polymers using a diode laser. A power range of 5-7 W was used to irradiate the boundary of two polymers. The heated polymers flowed into the matrices of the 3D fabricated structure, and reliable mechanical joining was achieved. Computer simulation showed the temperature distribution in the polymers, and flow direction was estimated based on the flux and temperature information. It was found that the more than the minimum energy threshold was required to effectively join the polymers and that two scans at low-speed were more effective than four scans at high speed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.106-110
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• 1992

컴퓨터에 의한 입체 형상 이용 기술의 발달로 3차원 CAD 데이타 형상의 제품을 2차원 형상의 층으로 연속적으로 적층 하는 입체인쇄(Stereolithography)기술개발이 활발하게 이뤄지고 있어 부품설계와 생산에 혁신을 예고하고 있으며, 이 같은 입체 인쇄 기술 중에서 특히, 특정 주파수의 빛에 의하여 경화되는 광 경화성수지(Photopolymer)에 레이저(Laser)를 주사하면 표면의 미소경화부만 경화되는 성질을 이용하여 소재를 경화시키는 광 조형법리 각광을 받고 있다. 본 논문에서는 광조형법에 의한 모델성형시 레이저빔의 조사에 의하여 야기되는 광경화성 수지의 상변화에 의한 성형물의 수축 및 뒤틀림에 대한 연구를 수행하였다

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.5
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• pp.418-426
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• 2003

To show a retina shape and thickness on the computer monitor, a laser has been used in Scanning Laser Ophthalmoscope(SLO) equipment using the traveling difference. This method requires exact synchronous control of laser traveling in optic system to show a clear 3-dimensional image of retina To obtain this image, this exact synchronism is very important for making the perfect plane scanning. In this study, a high speed and synchronous control of the galvanometer to make 3-dimensional retina image is presented. For the more, deadbeat load torque observer is added to the PI controller for compensation of the position error arisen in the high speed control. As a result, the proposed control system has a robust and precise response against the load torque variation appeared in high speed control. A stability and usefulness are verified by the computer simulation and the experiment.

• Laser Solutions
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• v.18 no.4
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• pp.6-11
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• 2015

Specially designed and 3D printed samples were prepared and joined by a diode laser source. To increase the strength of joining and reliability of samples, the surface was patterned by using a 3D printer. The joining surface was prepared as hemispherical shape with no-patterns, 0.5mm pitch, 0.75mm pitch and 1mm pitch. The optical properties of samples were measured by using an integrated sphere where classical Kubelka-Munk theory and modified Richard-Mudgetts theory for the analysis applied. Scanning speed was set at 500mm/min and laser power was varied between 9 and 10watts for the preliminary joining characteristic analysis.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.3
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• pp.7-13
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• 2007

In the optical module for optical communications, the flip chip bonding is used fer the precise alignment of the optical fiber and optical device. In flip chip bonding, the optical device is aligned and welded while observing the alignment mark of substrate and chip by using flip chip bonder in order to bond the optical device at the exact position. In this research, optical passive alignment method of photodiode(PD) flip chip bonding is suggested for low cost optical subassembly. By using the visible He-Ne laser (633nm wavelength), photodiode is easily aligned with emitting spot on the optical fiber with the help of stereoscopic alignment system. We compensated wavelength dependent deviation about 4m to find out real alignment position of 1550nm input laser by ray tracing. The maximum optical coupling efficiency between the optical fiber and photodiode was about 23.3%.

• Korean Journal of Optics and Photonics
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• v.29 no.1
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• pp.1-6
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• 2018

In this study, ray-tracing software was used to calculate the optical path length of an optical system. Using the optical path length, the optical phase, group delay (GD), group delay dispersion (GDD), and third-order dispersion (TOD) of the optical system were obtained. Pulse compressors using a prism pair or grating pair were designed to compensate the GDD of a real optical system for a femtosecond fiber laser. Also, a pulse stretcher using a grating pair with lenses or mirrors was designed. The results of this study can be used to calculate the dispersion of an optical system and optimize the performance of an ultrashort pulse laser optical system.