• Laser Solutions
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• v.18 no.1
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• pp.1-6
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• 2015

High welding speed and narrow weld seam are favorable for welding of magnesium alloy. Magnesium alloy is recommended for the smart frame because it has several advantages such as low density, high thermal conductivity, EMI shielding capability and good cast ability. This study is for the assembly welding of the magnesium smart frame with high productivity, good performance and low cost. The window for battery on AZ91D frame produced by die-casting was prepared by CNC machining. Corresponding AZ31 blank of 0.2mm thickness was prepared by die-blanking cut. All system set was fixed at the stationary bed but the laser beam was manipulated by scanner up-to 1,000mm/s speed. The weld joint between AZ31 sheet and AZ91D frame was welded by fiber laser on 850~1,000W output power. The joint showed penetration enough but some humping bead. The distortion by the weld heat was almost free because of the quick dissipation of the heat by small beam size and fast welding. Consequently, the thinner magnesium foil was assembled successfully to the magnesium frame of mobile phone.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.735-737
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• 2016

In this paper, we conducted a test of the 3D printer injection method and LSU (Laser Scanning Unit) feature a fusion of the polygon mirror scanning system that is the core mechanism operation for 3D printers for office laser printers SLA system. These tests ensure that the laser was operating and control well was confirmed that a certain point is output to the X-axis by means of a laser module and a polygon mirror. And confirmed after the F-theta lens is incident on the fixed laser power of the beam, and correction according to the correction beam on the mirror reflection was confirmed jineunji the focus according to the Z-axis upper plate.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.12
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• pp.30-37
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• 1996

On-line process control equipment for CO$_{2}$ laser cutting is not available for industrial applications. The major part of the industrial laser cutting machines are adjusted off-line by highly educated engineers. The quality inspection of the sample is visual and referred to different quality scales. Due to the lack of automation the potential laser users hesitate to implement the cutting method. The first step toward an automation of the process is the development of a process monitoring system and the research is cincentrated on the area of on-line quality monitoring during CO$_{2}$ laser cutting. The method is based on the detection of the emitted light from the cutting front by photo diode. The developed monitoring system consists of the OP Amplifier, A/D convertor, power supply and PC. The signal from the photo diode has been undertaken from Fourier analysis and statistical analysis with real time. The photograph of striation pattern was taken by metallurgical microscope. As a result, it is possible to predict the striation pattern according to the beam traveling speed.

• Proceedings of the Optical Society of Korea Conference
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• 2001.08a
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• pp.160-161
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• 2001

A diode laser system has been developed for the refractory glaucoma therapy. The diode lasers have merits in clinical usage including reduction of beam dispersion, higher absorption such as in melanin pigment, and lower complication in treatment. We present the system specification of laser diodes in 810mm with 3W power, which is delivered into the optical fiber core of 600${\mu}{\textrm}{m}$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.756-760
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• 1997

In this research, the automatic level measurement system used in land leveling was developed. By using a laser transmitter and a receiver as measuring equipments, level was measured automatically. The driving part of this system was composed of stepping motor, timing belt and pulley. It drived the laser receiver to track laser beam generated form the laser transmitter. The level measuring experiments were performed about three level change shapes (step, random, sine). This system could measure step level change of which amplitude was 40mm in 0.5s, random level change within .+-. mm, maximum measurement error. In case of sine level change, experiment was executed with varying the spatial frequency of level change. As a result, this system was able to measure sine level change of which spatial frequency was 0.5m $^{-1}$ accurately.

• Korean Journal of Optics and Photonics
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• v.31 no.6
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• pp.247-258
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• 2020

In this paper, based on a stochastic parallel gradient descent (SPGD) algorithm we study phase control of a coherent-beam-combining system under turbulent atmospheric conditions. Based on the statistical theory of atmospheric turbulence, we carry out the analysis of the phase and wavefront distortion of a laser beam propagating through a turbulent atmospheric medium. We also conduct numerical simulations of a coherent-beam-combining system with 7- and 19-channel laser beams distorted by atmospheric turbulence. Through numerical simulations, we characterize the phase-control characteristics and efficiency of the coherent-beam-combining system under various degrees of atmospheric turbulence. It is verified that the SPGD algorithm is capable of realizing 7-channel coherent beam combining with a beam-combining efficiency of more than 90%, even under the turbulent atmospheric conditions up to cn2 of 10-13 m-2/3. In the case of 19-channel coherent beam combining, it is shown that the same turbulent atmospheric conditions result in a drastic reduction of the beam-combining efficiency down to 60%, due to the elevated impact of the corresponding refractive-index inhomogeneity. In addition, by putting together the number of iterations of the SPGD algorithm required for phase locking under atmospheric turbulence and the time intervals of atmospheric phenomena, which typically are of the order of ㎲, it is estimated that hundreds of MHz to a few GHz of computing bandwidth of SPGD-based phase control may be required for a coherent-beam-combining system to confront such turbulent atmospheric conditions. We expect the results of this paper to be useful for quantitatively analyzing and predicting the effects of atmospheric turbulence on the SPGD-based phase-control performance of a coherent-beam-combining system.

• Journal of the Optical Society of Korea
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• v.12 no.4
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• pp.298-302
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• 2008

We have developed a 270-W 15-kHz MOPA system based on side-pumped rod-type Nd:YAG gain modules. The master oscillator is a 3-W 15-kHz $TEM_{00}$ $Nd:YVO_4$ laser with a pulse duration of 30 ns. To preserve the high beam quality during the amplification, we use image relay and polarization rotation which can simultaneously compensate for thermal lensing and thermal birefringence generated in the rod-type gain modules. After the amplification to 270 W with six rod-type gain modules, the beam quality factor ($M^2$) of the amplified laser beam is 5-10, and the pulse duration is maintained at 30 ns.

• Laser Solutions
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• v.6 no.3
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• pp.19-28
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• 2003

The manufacturing process for the microfluidic device can include sequential steps such as master fabrication, electroforming, and injection molding. The laser ablation, using masks, has been applied to the fabrication of channels in microfluidic devices. In this research, an excimer laser was used to engrave microscopic channels on the surface of PET (polyethylene terephthalate), which shows a high absorption ratio for an excimer laser beam with a wavelength of 248 m. When 50-${\mu}{\textrm}{m}$-wide rectangular microscopic channels are ablated with a 500 ${\times}$ 500 ${\mu}{\textrm}{m}$ square mask at a magnification ratio of 1/10, ditch-shaped defects were found in both corners. The measurement of laser beam intensity showed that a coherent image in the PET target caused such defects. Analysis based on the Fourier diffraction theory enabled the prediction of the coherent shape at the image surface as well as the diffraction beam shape between the mask and the image surface. It also showed that the diameter of the aperture had a dominant effect. The application of aperture with a diameter of less than 3 mm helped to eliminate such defects in the ablated rectangular microscopic channels on PET without such ditch-shaped defects.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.4
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• pp.10-15
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• 2007

Taguchi methods have been used for a long time to improve the product quality and process performance of a manufacturing system, Few researchers have applied this methodology in laser beam cutting (LBC) of sheet metals and found the considerable improvement in cut qualities. In all experimental investigations of LBC so far, the objective was to optimize the single quality characteristic at a time. In this paper the simultaneous optimization of multiple quality characteristics such as Kerf width and material removal rate (MRR) during pulsed Nd:YAG LBC of thin sheet of magnetic material (high Silicon-steel) has been presented using Taguchi's quality loss function. The results show the considerable improvement in multiple S/N ratio as compared to initial cutting condition. Also, the comparison of results from single and multi-objective optimization have been presented and it was found that the loss in quality is always possible shifting from single quality to multiple quality optimization.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1571-1573
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• 1994

In order to substitute for the conventional measuring system which could bring about technical inconveiences, measuring techniques for the fast transient high voltage upto 100 kV and small signals less than 1 V are developed by use of Laser Source with Packets cell. for the former, capacitive voltage divider was specially designed for reducing the impulse voltage less than the half-wave voltage of pockets cell. For the tatter, interferometer type was employed as a mean to removing the fluctuation of Laser output intensity. And also the main beam through the Pockels cell and the reference beam from the Laser source are seperated before being detected respectively by photo diodes. And then, these two signals are amplified and compared for detecting only the small signals applied across the Pockels cell. Throughout this work, Laser-based measuring system is likely to enable us, at this moment, to detect correctly lightning impulse voltage upto 100 kV and the small signals less than 1 V upto the 2 MHz. Such a system could be employed as a possible diagnostic measuring system at the substation.