• Title/Summary/Keyword: Photodiode

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Thickness Optimization of TbFeCo Disks by Computer Simulation (컴퓨터 시뮬레이션에 의한 TbFeCo 광자기 디스크 두께 최적화)

  • 김진홍;권혁전;신성철
    • Journal of the Korean Magnetics Society
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    • v.4 no.3
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    • pp.249-255
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    • 1994
  • Magneto-optical disks with dielectric layers for optical tunning are useful for maximizing the SNR. We have developed a computer program based on characteristic matrix to investigate the best combination of the film thicknesses. We have optimized the thicknesses of the multilayers which were composed of TbFeCo, dielectric, and AI layers at the wavelengh of 830nm. The criterion for the optimization of the film thickness was to maximize the figure of merit with maintaining the low ellipticity and rmre than 10% reflectivity.

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Cantilever deflection measurement system for AFM with PSD (PSD를 이요한 AFM용 미세 탐촉자의 변위측정장치)

  • 김홍준;장경영
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.11a
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    • pp.31-35
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    • 2000
  • A cantilever deflection measurement system for AFM(atomic force microscope) was constructed by the laser deflection method using LEP type PSD. Design process including sensitivity analysis was presented and the performance of the system was demonstrated by several experiments using a sample specimen with 50nm-step on the surface. The measured displacement-amplification-factor showed good agreement with the expected one with about 8% deviation. The step height measurement data were compared to what were acquired by commercial AFM, and the result showed that there were about 5nm-deviation between the two data. These results satisfies our expectation in the stage of system design.

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Investigation of Curvature Effect on Planar InP/InGaAs Avalanche Photodiodes for Edge Breakdown Suppression (경계항복 억제를 위한 평판형 InP/InGaAs 애벌랜치 포토다이오드의 곡률 효과 분석)

  • 이봉용;정지훈;윤일구
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.07a
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    • pp.206-209
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    • 2002
  • With the progress of semiconductor processing technology, avalanohe photodiodes (APDs) based on InP/InGaAs are used for high-speed optical receiver modules. Planar-type APDs give higher reliability than mesa-type APDs. However, Planar-type APDs are struggled with a problem of intensed electric field at the junction curvature, which causes edge breakdown phenomena at the junction periphery. In this paper, we focused on studying the effects of junction curvature for APDs performances by different etching processes followed by single diffusion to from p-n junction. The performance of each process is characterized by observing electric field profiles and carrier generation rates. From the results, it can be understood to predict the optimum structure, which can minimize edge breakdown and improve the manufacturability.

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Electrical properties of AZO transparent conductive oxide with substrate bias and $H_2$ annealing (기판바이어스와 수소열처리에 의한 AZO 투명전도막의 전기적 특성)

  • Jeong, Yun-Hwan;An, Jeong-Geun;Choi, Dai-Seub;Park, Choon-Bae
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.11a
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    • pp.331-331
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    • 2008
  • Transparent conductive oxide (TCO) are necessary as front electrode or anti-reflecting coating for increasing efficiency of LED and Photodiode. In this paper, aluminum-doped Zinc oxide films(AZO) were prepared by RF magnetron sputtering on Si substrate at room temperature with application of substrate bias from -60 to 60 V. Then annealed at temperature of 200, 300 and $400^{\circ}C$ for 1hr in $H_2$ ambient. Structural and electrical property of AZO thin films were investigated.

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A study on the real time quality estimation in laser tailored blank welding (레이저 테일러드 브랭크 용접의 실시간 품질판단 및 통계프로그램에 관한 연구)

  • Park, Young-Whan;Rhee, Se-Hum;Park, Hyun-Sung
    • Proceedings of the KSME Conference
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    • 2001.11a
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    • pp.791-796
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    • 2001
  • Welding using lasers can be mass-produced in high speed. In the laser welding, performing real-time evaluation of the welding quality is very important in enhancing the efficiency of welding. In this study, the plasma and molten metal which are generated during laser welding were measured using the UV sensor and IR sensor. The results of laser welding were classified into five categories such as optimal heat input, little low heat input, low heat input, focus off, and nozzle change. Also, a system was formulated which uses the measured signals with a fuzzy pattern recognition method which is used to perform real-time evaluation of the welding quality and the defects which can occur in laser welding. Weld quality prediction program was developed using previous weld results and statistical program which could show the trend of weld quality and signal was developed.

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A Study of the Retina Image Controllability using a Sledge (망막 영상 조절 장치에 관한 연구)

  • 이숙희;이영춘;양연식
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.10a
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    • pp.273-276
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    • 1997
  • Seeing is an intelligent act. Retina is the most important part among the components of eye which is comprised of iris, pupil, lens, optic disk, and so forth. Because retina acts like a photo receiver to detect light from every object, if damaged, animals have a severe problem to live along with themselves and sometimes they lose their sight. In the ophthalmology, doctors use special instrument to see exact retina image of object and operate the surgery by rotating focus control knob. In this study, a basic test is done to achieve the auto focus control instrument. Specially made sledge and attenuator are installed on the optic bed to change the distance and laser power between the first reflective mirror and the second one. Control panel which is compiled by Visual C t t to control stepping motors ,laser power and photodiode are implemented with ADA-board.

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A Study on the Torsional Vibration Measurement of the Horizontal Shaft with Disks (단을 가진 수평축의 비틀림진동 측정에 관한 연구)

  • 박일수;안찬우;김중완
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.04a
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    • pp.3-8
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    • 1997
  • This parer was presented for the experimental results of torsional vibrations of the horizontal rotating shaft with three disks. The torsional vibrations meter used is a laser system for non-contact measurement of torsional angular vibration velocity and torsional angular vibration displacement. The distance between the disks war changed; the one that had 76mm of disk distance war called basic model, and another that had 106mm of disk distance wide model, and other that had 46mm of disk distance narrow model. In each model, outer diameter of disk was 40mm. And 45mm, or 50mm was also used to extend the effective range of frequencies. The angula vibration displacement and the angular vibration velocity in its torsional vibration were measured to obtain the stable and the unstable regions.

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Real-time Measurement and Compensation of Motion Errors Using Extended Twyman-Green Interferometry (확장 트와이만-그린 간섭계를 이용한 운동 오차의 실시간 측정 및 보상)

  • 오정석;배은덕;김승우
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.288-291
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    • 2003
  • This paper presents an extended Twyman-Green interferometry that enables simultaneous and real-time measurement of 5-DOF motion errors of the translational moving stage. This method uses a null balancing technique in which two plane mirrors are used as target mirrors to generate an interferometric fringe utilizing the optical principles of Twyman-Green interferometry. Fringe is detected by 2D photodiode array for high-speed measurement. Errors are then independently suppressed by activation of piezoelectric actuators through real-time feedback control while the machine axis is moving. Experimental results demonstrate that a machine axis can be controlled with motion errors about 10 nm in linear displacement, 0.15 arcsec in angular displacement

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A Study on the Monitoring of Laser Welding for S45C Steel Sheets Using Nd:YAG Laser with Continuous Waves (연속파형 Nd:YAG레이저를 이용한 S45C 강판의 레이저 용접 모니터링에 관한 연구)

  • Kim, Do-Hyoung;Shin, Ho-Jun;Yoo, Young-Tae
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.21 no.5
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    • pp.814-823
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    • 2012
  • Fluctuation of light intensity from the keyhole becomes more significant in full penetration welding than partial penetration welding, since the plasma produced in the keyhole can escape from the rear side of the keyhole. The plasma optical radiation emitted during Nd:YAG laser welding of S45C steel samples has been detected with a Photodiode and analyzed under different process conditions. As the results, the BOP was performed for welding, behavior of plasma, spatter or plume was monitored to determine the reference signal. Then, random combination was made for comparison with the reference signal, which aimed at verifying reliability of the welding monitoring system that this study intended to develop.

Monitoring of plasma and spatter with photodiode in $CO_2$ laser welding (고출력 $CO_2$ 레이저 용접시 포토 다이오드를 이용한 플라즈마와 스패터 모니터링)

  • 박현성;이세헌;정경훈;박인수
    • Laser Solutions
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    • v.2 no.1
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    • pp.30-37
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    • 1999
  • Laser-welded Tailored Blank is the hottest thing in many automobile companies. But they demand on weld quality, reproducibility, and formability. So it is the great problem of automation of laser welding process. Therefore, it is requested to construct on-line process monitoring system on high accuracy. The light which is emitted from plasma and spatter in laser welding was detected by photo-diodes. It was found that the light intensity depends on welding speed. laser power, and flow rate of assist gas. The relationship between the plasma and spatter and the weld quality can be used for on-line laser weld monitoring systems.

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