• Title, Summary, Keyword: 포커스

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A Large-Scale Conference Service by Distributed Focus Control Method (분산 포커스 제어 방식에 의한 대규모 컨퍼런스 서비스)

  • Jang, Choonseo
    • The Journal of the Korea Contents Association
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    • v.14 no.7
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    • pp.10-17
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    • 2014
  • The focus maintains and manages conference session in the conference service. Load of focus increases by the number of participants and it becomes the major reason that limits the extendability of the large-scale conference service. In this paper, a new distributed focus control method has been proposed to solve this problem. Load of focus has been distributed to several conference nodes to implement large-scale conference service in this architecture. Conference nodes which have focus function subscribe to conference server's conference information database, and focus hae been allocated dynamically to process participants needs according to total numbers of the conference participants. For this purpose a new conference control event package for focus load control has been suggested. Furthermore the exchange procedure of SIP messages between focuses and participants also been suggested. The performance of the proposed system has been evaluated by simulation.

A Method of Efficient SIP Messages Processing for Conference Focus (컨퍼런스 포커스를 위한 효율적인 SIP 메시지 처리 방법)

  • Jo, Hyun-Gyu;Lee, Ky-Soo;Jang, Choon-Seo
    • Journal of the Korea Society of Computer and Information
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    • v.12 no.6
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    • pp.187-192
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    • 2007
  • Conference focus maintains and manages SIP(Session Initiation Protocol) signal connections with total conference participants, and it plays core functions of conference server. When the number of conference participants increases, conference focus restricts scalability of conference as increasing quantify of messages for processing. In this paper, to solve this problem. we propose a user system(conference information agent), which receives conference information from the conference focus and transfers them to the participants it manages. And we design and implement the total system including conference focus. When the conference information agent subscribe to the conference focus, it shows its possession of agent capability and capacity by using SIP SUBSCRIBE message. The conference focus informs to the other party by SIP response message that it was chosen as a conference information agent, and after that the conference focus sends all conference notification messages to it. So load of the conference focus can be reduced by this method. Finally, we have analyzed the performance of our system by experiments.

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Analysis of focus error signals on land/groove recordable optical disks (랜드/그루브 기록 광디스크에 대한 포커스 에러 신호 분석)

  • 이용재;박병호;신현국
    • Korean Journal of Optics and Photonics
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    • v.8 no.1
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    • pp.73-79
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    • 1997
  • We analyzed the variation of the focus error signal with the effect of land and groove, wavefront error, and optical system parameter variation for the knife-edge and astigmatism methods on the Land/Groove recordable optical disc, using a numerical simulation method. We verified causes of the zero-cross-shift that took place by the effect of land and groove by analyzing the diffraction beam including defocus wavefront errors. We also found that the sensitivty of the focus error signal was reduced by the effect of land and groove in the astigmatism method, as in the analysis of the focus error signal with the each order of the diffraction beam.

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Design of 3-Axis Focus Mechanism Using Piezoelectric Actuators for a Small Satellite Camera (소형 위성 카메라의 압전작동기 타입 3-축 포커스 메커니즘 설계)

  • Hong, Dae Gi;Hwang, Jai Hyuk
    • Journal of Aerospace System Engineering
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    • v.12 no.3
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    • pp.9-17
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    • 2018
  • For Earth observation, a small satellite camera has relatively weak structural stability compared to medium-sized satellite, resulting in misalignment of optical components due to severe launching and space environments. These alignment errors can deteriorate the optical performance of satellite cameras. In this study, we proposed a 3-axis focus mechanism to compensate misalignment in a small satellite camera. This mechanism consists of three piezo-electric actuators to perform x-axis and y-axis tilt with de-space compensation. Design requirements for the focus mechanism were derived from the design of the Schmidt-Cassegrain target optical system. To compensate the misalignment of the secondary mirror (M2), the focus mechanism was installed just behind the M2 to control the 3-axis movement of M2. In this case, flexure design with Box-Behnken test plan was used to minimize optical degradation due to wave front error. The wave front error was analyzed using ANSYS. The fabricated focus mechanism demonstrated excellent servo performance in experiments with PID servo control.

Depth-Map Generation using Fusion of Foreground Depth Map and Background Depth Map (전경 깊이 지도와 배경 깊이 지도의 결합을 이용한 깊이 지도 생성)

  • Kim, Jin-Hyun;Baek, Yeul-Min;Kim, Whoi-Yul
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • pp.275-278
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    • 2012
  • 본 논문에서 2D-3D 자동 영상 변환을 위하여 2D 상으로부터 깊이 지도(depth map)을 생성하는 방법을 제안한다. 제안하는 방법은 보다 정확한 깊이 지도 생성을 위해 영상의 전경 깊이 지도(foreground depth map)와 배경 깊이 지도(background depth map)를 각각 생성 한 후 결합함으로써 보다 정확한 깊이 지도를 생성한다. 먼저, 전경 깊이 지도를 생성하기 위해서 라플라시안 피라미드(laplacian pyramid)를 이용하여 포커스/디포커스 깊이 지도(focus/defocus depth map)를 생성한다. 그리고 블록정합(block matching)을 통해 획득한 움직임 시차(motion parallax)를 이용하여 움직임 시차 깊이 지도를 생성한다. 포커스/디포커스 깊이 지도는 평탄영역(homogeneous region)에서 깊이 정보를 추출하지 못하고, 움직임 시차 깊이 지도는 움직임 시차가 발생하지 않는 영상에서 깊이 정보를 추출하지 못한다. 이들 깊이 지도를 결합함으로써 각 깊이 지도가 가지는 문제점을 해결하였다. 선형 원근감(linear perspective)와 선 추적(line tracing) 방법을 적용하여 배경깊이 지도를 생성한다. 이렇게 생성된 전경 깊이 지도와 배경 깊이 지도를 결합하여 보다 정확한 깊이 지도를 생성한다. 실험 결과, 제안하는 방법은 기존의 방법들에 비해 더 정확한 깊이 지도를 생성하는 것을 확인할 수 있었다.

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