• Laser Solutions
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• v.14 no.3
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• pp.7-11
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• 2011

As an active emission display using emissive polymer has had much attention recently, needs for a selective patterning of emissive layer for those displays have been increased abruptly. Therefore, the various laser sources in terms of its wavelength has been used for laser direct patterning. In this work, the feasibility of those processes is examined using numerical analysis and the experimental investigation. A sample has multi-layered structure, emissive polymer on aluminum which is deposited on a glass substrate. Key factors for optimizing the laser patterning of the emissive polymer are considered into the control of ablation products, large-sized particle, and the choice of the appropriate wavelength for minimizing the heat affected zone and the remnant layer.

• Current Optics and Photonics
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• v.7 no.6
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• pp.701-707
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• 2023

In laser imaging, accurate extraction of the laser's center is essential. Several methods exist to extract the laser's center in an image, such as the geometric mean, the parabolic curve fitting, and the Gaussian curve fitting, etc. The Gaussian curve fitting is the most suitable because it is based on the physical properties of the laser. The width of the Gaussian laser beam depends on the distance from the laser source to the target object. It is assumed in general that the distance remains constant at a laser spot resulting in a symmetric Gaussian model for the laser image. However, on a curved surface of the object, the distance is not constant; The laser beam is narrower on the side closer to the focal point of the laser light and wider on the side closer to the laser source, which causes the distribution of the laser beam to skew. This study presents a modified Gaussian model in the laser imaging to incorporate the slant angle of a curved object. The proposed method is verified with simulation and experiments.

• Laser Solutions
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• v.3 no.1
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• pp.2-11
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• 2000

Laser cleaning has begun to attract a considerable amount of interest recently as a new cleaning technique among scientists and engineers. The unique characteristics of laser cleaning are currently finding successful applications in industry, in medicine as well as in the world of art conservation. This paper takes an overview of the laser cleaning technique itself including basic principles and characteristics, and provides an account of current trends especially with regard to practical applications. Experience with its successful applications in various fields shows that laser cleaning may be about to emerge as a real alternative to conventional cleaning methods.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.29-29
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• 2009

On this research, laser welding technology for manufacturing automobile body is studied. Laser welding technology is one of the important technologies used in the manufacturing of lighter, safer automotive bodies at a high level of productivity; the leading automotive manufacturers have replaced spot welding with laser welding in the process of car body assembly. Korean auto manufacturers are developing and applying the laser welding technology using a high output power Nd:YAG laser and a 6-axes industrial robot. On the other hand, the robot-based remote laser welding system was equipped with a long focal laser scanner system in robotic end effect. Laser system, robot system, and scanner system are used for realizing the high speed laser welding system. The remote laser welding system and industrial robotic system are used to consist of robot-based remote laser welding system. The robot-based remote laser welding system is flexible and able to improve laser welding speed compared with traditional welding as spot welding and laser welding. The robot-based remote laser systems used in this study were Trumpf's 4kW Nd:YAG laser (HL4006D) and IPG's 1.6kW Fiber laser (YLR-1600), while the robot systems were of ABB's IRB6400R (payload:120kg) and Hyundai Heavy Industry's HX130-02 (payload:130kg). In addition, a study of quality evaluation and monitoring technology for the remote laser welding was conducted. The welding joints of steel plate and steel plate coated with zinc were butt and lapped joints. The quality testing of the laser welding was conducted by observing the shape of the beads on the plate and the cross-section of the welded parts, analyzing the results of mechanical tension test, and monitoring the plasma intensity and temperature by using UV and IR detectors. Over the past years, Trumf's 4kW Nd:YAG laser and ABB's IRB6400R robot system was used. Nowadays, the new laser source, robot and laser scanner system are used to increase the processing speed and to improve the efficiency of processes. This paper proposes the robot-based remote laser welding system as a means of resolving the limited welding speed and accuracy of conventional laser welding systems.

• Journal of Acupuncture Research
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• v.26 no.6
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• pp.21-30
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• 2009

Objectives : Being introduced in the 1980s, laser acupuncture studies have been steadily carried on such as its thermal effects on human body. However, the mechanisms of effect are not yet clearly explained. Generally, laser acupuncture could be favorable for pediatric patients or people under special conditions (hemophilia, needle-phobia, pathogen-carriers, etc.) because of lower risk of infection, bleeding, pain or fainting. But there are still problems for using laser acupuncture equivalently as the traditional metal needle. The goal of this study is to review the fundamentals, history and present trend of laser acupuncture study, and to suggest how to develop laser acupuncture as an oriental medical device. Method : We performed literature search using PubMed(http://www.ncbi.nlm.nih.gov/pubmed) and Scopus(http://www.scopus.com). Search conditions are laser acupuncture, laser needle, LLLT(as title or abstract) or Litscher G(as author). Main target studies are physical fundamentals, clinical trials, physiological results and device proposals. Results : Many research have shown the similarities of laser acupuncture and traditional metal acupuncture and have reported clinical and physiological effects of laser acupuncture. But, still laser acupuncture is not widely used in Korea due to high-cost of equipments and the lack of clear understanding of laser devices. Additionally, there are still challenges in standardization and device development. Conclusions : Frequencies, laser modes, waveguides, adaptor types, polarization and signal modulations are suggested as future study subjects on laser acupuncture. More various studies and efforts for device development have to be performed to provide oriental medical doctors with evidence based confidence about usage of laser acupuncture.

• Journal of the Optical Society of Korea
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• v.7 no.3
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• pp.150-155
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• 2003

Femtosecond laser ablation mechanism was systematically investigated on sodalime glass in ambient conditions. The ablation crater diameter was measured for varying numbers of laser pulses as for varying well as the laser fluence. The analysis of the results with a one dimensional spatial Gaussian fluence distribution reveals that the inherent ablation mechanism has been altered from a multi-photon process to a single photon excitation due to defect sites that have been accumulated by successive laser pulses. Furthermore, the transition between the two regimes was found to be a function of both the laser fluence and the number of laser shots.

• Journal of Welding and Joining
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• v.9 no.1
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• pp.32-39
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• 1991

A 200W pulsed Nd: YAG laser for fine welding was developed. The important laser parameters such as laser peak power, average power, pulse width, and pulse energy for welding were studied. In order to obtain the sufficient laser power density for welding, thermal lensing effects were analyzed and a laser resonator with laser beam divergence was designed. The power supply unit was designed to support up to 7kW input. The pulse control unit was developed using a GTO thyristor and could control over 100kW input power to obtain 3.5kW peak power laser. Also due to the GTO thyristor the pulse width could be varied continuously from 0.1 to 20 msec and maximum repetition rate was as high as 300pps.

• Laser Solutions
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• v.10 no.1
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• pp.29-34
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• 2007

We propose a novel application of laser engraving to patterning of light guide panel (LGP) for backlight. The feasibility of three-dimensional engraved pattern in the LGP was verified by measuring brightness and uniformity. To improve the overall uniformity, we have modified proposed patterns and found improved design for patterns. The tailoring of pattern by using laser engraving method could endow the controllability of uniformity. The proposed LGPs are more efficient in both average brightness and uniformity of illumination than the conventional LGPs which have surface pattern on the panel.

• Laser Solutions
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• v.5 no.3
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• pp.15-20
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• 2002

The principal obstacle to selection of a laser processing method in production is its relatively high equipment cost and the natural unwillingness of production supervision to try something new until it is thoroughly proven. The major objective of this work is focused on the combined features of gas tungsten arc and a low-power cold laser beam. In this work, the laser beam from a 7 watts carbon monoxide laser was combined with electrical discharges from a short-pulsed capacitive discharge GTA welding power supply. When the low power CO laser beam passes through a special composition shielding gas, the CO molecules in the gas absorbs the radiation, and ionizes through a process blown as non-equilibrium, vibration-vibration pumping. The resulting laser-induced plasma(LIP) was positioned between various configurations of electrodes. The high-voltage impulse applied to the electrodes forced rapid electrical breakdown between the electrodes. Electrical discharges between tungsten electrodes and aluminum sheet specimens followed the ionized path provided by LIP. The result was well-focused melted spots.

• Journal of the Optical Society of Korea
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• v.13 no.3
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• pp.321-329
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• 2009

Following their applications in cardiology, ophthalmology and dentistry among others, the advent of lasers in dermatology and urology had become the success story of the past decade. Laser-assisted treatments in dermatology and urology are mainly based on the laser-induced tissue injury/coagulation and/or ablation, depending upon the desirable clinical endpoint. In this review, we discussed the underlying mechanisms of the laser induced tissue ablation. In any medical laser application, the controlled thermal injury and coagulation, and the extent of ablation, if required, are critical. The laser thermal mechanism of injury is intricately related to the selective absorption of light and its exposure duration, similarly to the laser induced ablation. The laser ablation mechanisms were categorized into four different categories (the photo-thermally induced ablation, the photo-mechanically induced ablation, the plasma induced ablation and the photoablation) and their fundamentals are herein described. The brief history of laser treatment modality in dermatology and urology are summarized.