• Journal of the Semiconductor & Display Technology
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• v.16 no.4
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• pp.36-40
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• 2017

With an attempt to enhance the visibility of laser beam, we have investigated a black matrix with scattering particles by ray tracing simulations. As the scattering particle density is increased, the detected power by the receiver is increased, thereby enhancing the visibility. In reality, the visibility is reduced with increasing incident angle (away from the normal incidence) of laser beam, a phenomenon also observed by ray tracing simulations. It is due to the fact that the mean path is increased within a highly absorptive BM layer or a smaller number of rays hit the BM area when the incident angle is high. Embedding a number of scattering particles into BM may bring in crosstalk among pixels. However, it is negligible because scattered rays inside highly absorptive BM are re-scattered due to the high scattering particle density, decreasing the power of scattered rays into the active areas.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.5
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• pp.195-200
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• 2009

CRT-based RSA algorithm, which was implemented on smartcard, microcontroller and so on, leakages secret primes p and q by fault attacks using laser injection, EM radiation, ion beam injection, voltage glitch injection and so on. Among the many fault injection methods, voltage glitch can be injected to target device without any modification, so more practical. In this paper, we made an experiment on the fault injection attack using abnormal source voltage. As a result, CRT-RSA's secret prime p and q are disclosed by fault attack with voltage glitch injection which was introduced by several previous papers, and also succeed the fault attack with source voltage blocking for proper period.

• Journal of Powder Materials
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• v.29 no.4
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• pp.314-319
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• 2022

The effect of the laser beam diameter on the microstructure and hardness of 17-4 PH stainless steel manufactured via the directed energy deposition process is investigated. The pore size and area fraction are much lower using a laser beam diameter of 1.0 mm compared with those observed using a laser beam diameter of 1.8 mm. Additionally, using a relatively larger beam diameter results in pores in the form of incomplete melting. Martensite and retained austenite are observed under both conditions. A smaller width of the weld track and overlapping area are observed in the sample fabricated with a 1.0 mm beam diameter. This difference appears to be mainly caused by the energy density based on the variation in the beam diameter. The sample prepared with a beam diameter of 1.0 mm had a higher hardness near the substrate than that prepared with a 1.8 mm beam diameter, which may be influenced by the degree of melt mixing between the 17-4 PH metal powder and carbon steel substrate.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.5
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• pp.370-376
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• 2016

Corrosion on the surface of a structure can generate cracks or cause walls to thin. This can lead to fracturing, which can eventually lead to fatalities and property loss. In an effort to prevent this, laser imaging technology has been used over the last ten years to detect thin-plate structure, or relatively thin piping. The most common laser imaging was used to develop a new technology for inspecting and imaging a desired area in order to scan various structures for thin-plate structure and thin piping. However, this method builds images by measuring waves reflected from defects, and subsequently has a considerable time delay of a few milliseconds at each scanning point. In addition, the complexity of the system is high, due to additional required components, such as laser-focusing parts. This paper proposes a laser imaging method with an increased scanning speed, based on excitation and the measurement of standing waves in structures. The wavenumber of standing waves changes at sections with a geometrical discontinuity, such as thickness. Therefore, it is possible to detect defects in a structure by generating standing waves with a single frequency and scanning the waves at each point by with the laser scanning system. The proposed technique is demonstrated on a wall-thinned plate with a linear thickness variation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.105-112
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• 2018

This paper proposes a method for fabricating heatable glass using the conduction characteristics of metal thin films deposited on the surface of Low-e(Low emissivity) glass. The heating value of Low-e glass depends on the Joule heat caused by Low-e glass sheet resistance. Hence, its prediction and design are possible by measuring the sheet resistance of the material. In this study, silver electrodes were placed at 50 mm intervals on a soft Low-e glass sample with a low emissivity layer of 11 nm. This study measured the sheet resistance using a 4-point probe, predicted the power consumption and heating value of the Low-e glass, and confirmed the heating performance through fabrication and experience. There are two conventional methods for manufacturing heatable glass. One is a method of inserting nichrome heating wire into normal glass, and the other is a method of depositing a conductive transparent thin film on normal glass. The method of inserting nichrome heating wire is excellent in terms of the heating performance, but it damages the transparency of the glass. The method for depositing a conductive transparent thin film is good in terms of transparency, but its practicality is low because of its complicated process. This paper proposes a method for manufacturing heatable glass with the desired heating performance using Low-e glass, which is used mainly to improve the insulation performance of a building. That is by emitting a laser beam to the conductive metal film coated on the entire surface of the Low-e glass. The proposed method is superior in terms of transparency to the conventional method of inserting nichrome heating wire, and the manufacturing process is simpler than the method of depositing a conductive transparent thin film. In addition, the heat characteristics were compared according to the patterning of the surface thin film of the Low-e glass by an emitting laser and the laser output conditions suitable for Low-e glass.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.1
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• pp.1-11
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• 2005

Several Solid Freeform Fabrication Systems(SFFS) are commercialized in a few companies for rapid prototyping. However, they have many technical problems including the limitation of applicable materials. A new method of agile prototyping is required for the recent manufacturing environments of multi-item and small quantity production. The objectives of this paper include the development of a novel method of SFFS, the CAFL/sup VM/(Computer Aided Fabrication of Lamination for Various Material), and the manufacture of the various material samples for the certification of the proposed system and the creation of new application areas. For these objectives, the technologies for a highly accurate robot path control, the optimization of support structure, CAD modeling, adaptive slicing was implemented. However, there is an important problem with the conventional 2D lamination method. That is the inaccuracy of 3D model surface, which is caused by the stair-type surface generated in virtue of vertical 2D cutting. In this paper, We design the new control algorithm that guarantees the constant speed, precise positioning and tangential cutting on the 5DOF SFFS. We develop the tangential cutting algorithm to be controlled with constant speed and successfully implemented in the 5DOF CAFL/sup VM/ system developed in this paper. Finally, this paper confirms its high-performance through the experimental results from the application into CAFL/sup VM/ system.

• Korean Journal of Materials Research
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• v.8 no.10
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• pp.884-889
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• 1998

Amorphous silicon films of large area have been crystallized by a line shape excimer laser beam of one dimensional scanning with a gaussian profile in the scanning direction. In order to characterize the crystalline phase transition of thickness variables in excimer laser annealing(ELA), angle wrapping method was used. And also to characterize the residual stresses of crystalline phase transition in the case of angle wrapped-crystalline silicon on corning 7059 glass, polarized raman spectroscopies were measured at various laser energy density and substrate temperature. The residual stress varies from $9.0{\times}10^9$ to $9.9{\times}10^9$, and from $9.9{\times}10^9$ to $1.2{\times}10^10$dyne/${cm}^2$ of the substrate temperature at room temperature and varies from $8.1{\times}10^9$ to $9.0{\times}10^9$, and from $9.0{\times}10^9$ to $9.9{\times}10^9$dyne/${cm}^2$ of the substrate temperature at $400^{\circ}C$ as a function of direction from surface to substrate. According to the direction from the surface in liquid phase to the interface and from the interface to near the substrate in solid phase of recrystallized Si thin film, respectively. Thus, the stress is increased from(Liquid phase to solid phase) with phase transition.

• Radiation Oncology Journal
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• v.19 no.4
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• pp.301-305
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• 2001

Purpose : This study was peformed for the evaluation of the feasibility and toxicity of hypofractionated radiation therapy for early glottic cancer Methods and Materials : From February 1999 to February 2000, 20 patients with Histologically confirmed Stage I, II glottic cancer were enrolled into this study. There were 18 males and 2 females, the median age of the patients was 59 years. The distribution of stage distribution was as fellows; T1aN0-16 patients, T1bN0-1 patient, T2N0-3 patients. Eighteen patients underwent laryngomicroscopic biopsy only, and two patients underwent laser cordectomy. All patients received radical radiation therapy (2.5 Gy per fraction, 24 fractions, total 60 Gy). Median duration of treatment was 36 days (range $31\~45\;days$). Results : Radiation therapy were well tolerated. Most common acute reactions were odynophagia and hoarseness, and these reactions resolved after radiation therapy. There were one case of RTOG grade 3 odynophagia $(5\%)$, six cases of grade 3 hoarseness $(30\%)$. Response of radiation therapy was evaluated one month after completion of treatment. All patients revealed complete response. During follow up, total three cases of treatment failure were detected. two cases were local recurrence in 10 and 13 months of radiation therapy and one case was local recurrence and distant metastasis in 2 months of radiation therapy. Conclusion : This hypofractionated radiation therapy schedule was feasible and effective for control of early glottic cancer But longer follow up time would be required to assess the long-term disease control and the late complication by shortening radiation therapy duration.

• Korean Journal of Optics and Photonics
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• v.19 no.1
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• pp.20-24
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• 2008

A color filter was proposed and demonstrated by incorporating a subwavelength patterned 1-dimensional grating in poly silicon. It was produced by employing the laser interference lithography method, providing much wider effective area compared to the conventional e-beam lithography. A $SiO_2$ layer was introduced on top of the silicon grating layer as a mask for the etching of the silicon, facilitating the etching of the silicon layer. It was theoretically found that the selectivity of the filter was also improved thanks to the oxide layer. The parameters for the designed device include the grating pitch of 450 nm, the grating height of 100 nm and the oxide-layer height of 200 nm. As for the fabricated filter, the spectral pass band corresponded to the blue color centered at 470 nm and the peak transmission was about 40%. Within the effective area of $3{\times}3mm^2$, the variation in the relative transmission efficiency and in the center wavelength was less than 10% and 2 nm respectively. Finally, the influence of the angle of the incident beam upon the transfer characteristics of the device was investigated in terms of the rate of the relative transmission efficiency, which was found to be equivalent to 1.5%/degree.

• Korean Journal of Optics and Photonics
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• v.11 no.2
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• pp.73-79
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• 2000

We measure a beam diameter of scan and sub-scan direction of LSD (Laser Scanning Urnt) which uses $fheta$ lens produced by injecLion molding method as a scanning lens. While the measured beam diameter in scan direction, which is $62muextrm{m}$ to $68\mu\textrm{m}$, shows similar size comparing to the design beam diameter, the sub-scan beam diameter shows sIzable beam diameter deviation as much as 37 11m ranging from $78\mu\textrm{m}$ to $115\mu\textrm{m}$. Injection molding lens has the surface figure error due to the shrinkage III the cooling time and the internal distortion (birefringence) due to the uneven cooling conditIOn so that these bring about wavefront aberration (i.e., the enlargement of beam size), and are eventually expre~sed as the deterioration of the pdnting image. In this paper. we first measure and analyze beam diameter, birefringence (polanzation ratio), and asphedcal figure error of mIens in order to know the principle cause of the beam diameter deviation in sub-scan directIOn. And Lhen. through the analysis of a designed depth of focus and a calculated field curvature (imaging position of the optical axis directIon) using the above figure elTor data, we know Lhat the birefringence IS the main factor of sizable beam diameter deVIation in sub-scan direction. ction.