• Title/Summary/Keyword: Defocusing effect

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Improved 3D Resolution Analysis of N-Ocular Imaging Systems with the Defocusing Effect of an Imaging Lens

  • Lee, Min-Chul;Inoue, Kotaro;Cho, Myungjin
    • Journal of information and communication convergence engineering
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    • v.13 no.4
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    • pp.270-274
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    • 2015
  • In this paper, we propose an improved framework to analyze an N-ocular imaging system under fixed constrained resources such as the number of image sensors, the pixel size of image sensors, the distance between adjacent image sensors, the focal length of image sensors, and field of view of image sensors. This proposed framework takes into consideration, for the first time, the defocusing effect of the imaging lenses according to the object distance. Based on the proposed framework, the N-ocular imaging system such as integral imaging is analyzed in terms of depth resolution using two-point-source resolution analysis. By taking into consideration the defocusing effect of the imaging lenses using ray projection model, it is shown that an improved depth resolution can be obtained near the central depth plane as the number of cameras increases. To validate the proposed framework, Monte Carlo simulations are carried out and the results are analyzed.

Defocusing image generation corresponding to focusing plane by using spatial information of 3D objects (3차원 물체의 공간정보를 이용한 임의의 집속면에 대응하는 디포커싱 영상 구현)

  • Jang, Jae-Young;Kim, Young-Il;Shin, Donghak;Lee, Byung-Gook;Lee, Joon-Jae
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.17 no.4
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    • pp.981-988
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    • 2013
  • In this paper, we propose a method to generate defocusing images at the focusing plane using the 3D spatial information of object through pickup process of integral imaging technique. In the proposed method, the focusing and defocusing images are generated by the convolution operation between elemental images and ${\delta}$ function array. We observed the image difference by defocusing degree according to the distance of focusing plane. To show the feasibility of the proposed method, some preliminary experiments are carried out and the results are presented.

LASER WELDING OF TI-NI SHAPE MEMORY ALLOY WIRE

  • Kim, Young-Sik;Kim, Jong-Do
    • Proceedings of the KWS Conference
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    • 2002.10a
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    • pp.139-144
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    • 2002
  • Ti-50.9at%Ni wires were welded using pulsed YAG laser. The laser welded wires were tested for investigating the shape memo교 effect and the ability of super elasticity. The fatigue properties of the welded wires were investigated using the rotary bending fatigue tester specially designed for wires. Moreover, the effect of defocusing distance during laser welding on the static and fatigue properties was investigated. The shape memory effect and super elasticity of the laser welded wires were approximately identical with that of base metal at the test temperature below 353K. However, the welded wires were broken within elastic limit at the test temperature above 353k. Under the cyclic bending loading conditions, the welded wires could be useful only below the elastic limit, while the base metal had sufficient fatigue life even the stress induced M-phase region. The fatigue strength of the welded wires was about half of that of the base metal. The deterioration of the static and fatigue properties in the welded wires was proven to be from the large difference of the transformation behavior between the base metal and welded part that is caused by vaporization of Ni-content at the welded part during the welding process. The defocusing distance below 3mm acted more largely on lowering the strength of the welded wires than that of 6mm or 8mm.

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Wear Behavior of Laser Modified SM45C Steel (레이저 표면개질된 SM45C강의 마멸거동)

  • 배춘익;옥철호;박흥식;전태옥
    • Tribology and Lubricants
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    • v.16 no.1
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    • pp.15-21
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    • 2000
  • Radiation of Nd-YAG laser changes and refines the surface microstructure of steels, which gives rise to enhancement of hardness and resulting wear resistance. In the present work, the effect of processing parameters during the surface modification with laser on the wear behavior of the SM45C steel was studied by means of wear testing. The counter material was alumina ceramics. The microstructure observation revealed the dependence of molten depth and width on the defocusing distance. The laser modification of steel surface give rise to improved wear resistance in the testing speed range of either <0.2 m/s or >0.9 m/s Material transfer from steel was wear observated the surface of counter material when testing speed was lower than 0.7 m/s.

Three-dimensional vortex structure near a corner of a translating plate (병진운동하는 평판의 모서리에서의 3차원 와류 구조 가시화)

  • Kim, Daegyoum
    • Journal of the Korean Society of Visualization
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    • v.13 no.1
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    • pp.21-25
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    • 2015
  • Three-dimensional vortex structures in the corner region of translating normal plates are visualized experimentally with defocusing digital particle image velocimetry. Vortex formation processes for three plates with corner angle $60^{\circ}$, $90^{\circ}$, and $120^{\circ}$ are compared in order to study the effect of corner shape on vortex formation. In all cases, the self-induction of the starting vortex and its interaction with the potential flow induced by the moving plate cause the vortex to change its form dynamically after the plate starts to translate. While the vortex near a corner follows the plate in the low corner angle of $60^{\circ}$, the vortex separates early from the plate and its forward motion becomes slow in the high corner angle of $120^{\circ}$. It is also found that the starting vortex can transport inward at the corner, which depends on the corner angle.

Laser- Plume Effects on Radiation Energy Transfer in Materials Processing (레이저 가공시 에너지 전달과 Plume 효과)

  • Kang, Kae-Myung;Kim, Kwang-Ryul
    • Korean Journal of Materials Research
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    • v.12 no.1
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    • pp.27-35
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    • 2002
  • In laser materials processing, localized heating, melting and evaporation caused by focused laser radiation forms a vapor on the material surface. The plume is generally an unstable entity, fluctuating according to its own dynamics. The beam is refracted and absorbed as it traverses the plume, thus modifying its power density on the surface of the condensed phases. This modifies material evaporation and optical properties of the plume. A laser-produced plasma plume simulation is completed using axisymmetric, high-temperature gas dynamic model including the laser radiation power absorption, refraction, and reflection. The physical properties and velocity profiles are verified using the published experimental and numerical results. The simulation results provide the effect of plasma plume fluctuations on the laser power density and quantitative beam radius changes on the material surface. It is proved that beam absorption, reflection and defocusing effects through the plume are essential to obtain appropriate mathematical simulation results. It is also found that absorption of the beam in the plume has much less direct effect on the beam power density at the material surface than defocusing does and helium gas is more efficient in reducing the beam refraction and absorption effect compared to argon gas for common laser materials processing.

Fatigue Properties of Ti-Ni Shape Memory Alloy Wire Welded by Nd: YAG Laser

  • Kim, Y.S.;Kim, J.D.;Kil, B.L.
    • International Journal of Korean Welding Society
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    • v.3 no.1
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    • pp.39-44
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    • 2003
  • The welded specimens were made by butt welding of the 2 wires of 50mm length using the pulsed YAG laser. The laser welded wires were tested for investigating the shape memory effect and the ability of super elasticity. The fatigue properties of the welded wires were investigated using the rotary bending fatigue tester specially designed for wires. Moreover, the effect of defocusing distance during laser welding on the static and fatigue properties was Investigated. The shape memory effect and super elasticity of the laser welded wires were approximately identical with that of base metal at the test temperature below 353K. However, the welded wires were broken within elastic limit at the test temperature above 353k. Under the cyclic bending loading conditions, the welded wires could be useful only below the elastic limit, while the base metal had sufficient fatigue life even the stress induced M-phase region. The fatigue strength of the welded wires was about half of that of the base metal. The deterioration of the static and fatigue properties in the welded wires was proven to be from the large difference of the transformation behavior between the base metal and welded part that is caused by vaporization of Ni-content at the welded part during the welding process. The defocusing distance below 3mm acted more largely on lowering the strength of the welded wires than that of 6mm or 8mm.

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Model for the Inertial Focusing of Particles Using an Atmospheric Aerodynamic Lens (상압 공기역학적 렌즈의 입자 관성집속 모델)

  • Lee, Jin-Won;Lee, Min-Yeong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.3
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    • pp.315-321
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    • 2001
  • Aerodynamic lenses are widely used in generating particle beams of high density and small diameter, but analytical or modeling studies are limited only in the free molecular regime. In this study, it is shown that generating particle beam is also possible in atmospheric pressure range, and the mechanism of generating particle beam using an orifice is analysed into three different parts : fluid dynamic contraction, diffusional defocusing, and inertial focusing. In laminar flow conditions, the diffusional defocusing effect can be neglected, and the effects of inertial focusing can be expressed in terms of the orifice size and Stokes number. Numerical experiments are done for two different orifices, d/D=1/5 and 1/10 and particle diameter d(sub)p=1-10 ㎛. The results for two different orifices can be made into a single curve when a modified Stokes number is used. The inertial focusing effect diminishes when the modified Stokes number becomes smaller than 10(sup)-2.

Effects of storing defocused Fourier plane holograms in three-dimensional holographic disk memories (디스크형 3차원 홀로그래피 메모리에서 비초점 Fourier 면 홀로그램의 저장 효과)

  • 장주석;신동학
    • Korean Journal of Optics and Photonics
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    • v.12 no.1
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    • pp.61-66
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    • 2001
  • Defocused Fourier plane holograms are stored in disk-type holographic memories where thin recording media are used, the areal storage density per hologram and the intensity uniformity of the signal beam at the recording plane are studied. As the pixel pitch of the spatial light modulator that represents binary data increases, the storage density per hologram increases if exact Fourier holograms are stored. When defocused Fourier plane holograms are stored, however, we show that there exists an optimal pixel pitch that maximizes the area storage density per hologram in general, to increase the areal storage density per hologram, f/# of the Fourier transform lens that focuses the data image should be as small as possible. In this case, not only the intensity distribution at the recording plane but also the recording area becomes very sensitive to the degree of defocusing. Therefore, even if the exact Fourier plane holograms are stored, the defocusing effect owing to the medium thickness should be taken into account to achieve the maximal areal storage density per hologram.logram.

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Dark Spatial Soliton Generation in the Photorefractive Photovoltaic Material (광굴절 광기전력 매질에서 어두운 공간솔리톤 발생)

  • 전남희;전진호;이재형;장준성
    • Proceedings of the Optical Society of Korea Conference
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    • 2000.02a
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    • pp.312-313
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    • 2000
  • 공간솔리톤(spatial soliton)은 빔이 매질을 진행할 때 자기집속 효과(self-focusing effect) 와 자기확산 효과(self-defocusing effect)에 의해서 회절이 보상되어 형성된다. Kerr 매질에서는 굴절률의 변화가 빔의 세기에 비례하하므로 솔리톤을 발생시키기 위해서는 수 MW/$ extrm{cm}^2$ 이상인 빔의 세기가 요구된다. 광굴절 매질은 광굴절효과에 의해서 굴절률의 변화로 공간솔리톤을 발생시킨다. 비균일한 빔이 매질에 입사되면 전도대로 여기된 free carrier가 분포 차이에 의해서 확산이 일어나게 된다. 그리고 외부에서 걸어준 전기장 및 광기전력 효과로 인한 drift가 일어나게 되고 이것에 의해 생긴 공간 전하장(space charge field)에 의하여 굴절률의 변화가 생긴다. (중략)

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