Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/49011
標題: 建立具有幾何修正能力之二維投影機陣列系統
Construction of 2d Projector Array System with Geometric Correction
作者: 許舜斌
關鍵字: 投影機陣列
電信工程
影像柔邊
影像縫合
幾何修正
技術發展
摘要: Recently there has been a great interest in the study of projectors and its applications. Theseresearch efforts are in response to the tremendous and sometimes special requests in thedisplay of data/information. For example, the pop music concert might need a very fancy anddynamic lighting system. The facility provides not only the colorful lights that change withthe music tempo, but also some lighting animation or even 3D images. The requests could besatisfactorily met by the use of projectors as long as the lighting information ispre-programmed before the light is projected. Other possible applications include the widefield-of-view that creates the virtual reality or the visually high- fidelity scenes. Applicationsin these directions often need an array of projectors to create a spectacular viewing effect, andthus raise some technical issues: how to calibrate the array of projectors, and/or modify theimage to be projected such that the results still look visually comfortable? Since thecalibrations of projectors involve the collaboration with the manufacturers, our studies focuson the method to pre-process the images. In this project we propose to construct atwo-dimensional projector array system that is able to project images or video on a non-planarscreen. The two-dimensional array prototype in our research includes a two-by-two projectormatrix. We expect the design to be easily extendible to other types of arrays such astwo-by-three or three-by-three, etc. Due to the differences in the positions and photometricparameters between projectors, the installation of the projector system can be verytime-consuming. Our first goal is to make the system user-friendly. To achieve this, wepropose to project a test pattern onto a test screen and use the projection as a feedback to thesystem via a web camera. This feedback provides the tilting, aligning and photometricinformation for each projector in the array, and automates the identification of the maximuminterior rectangle (MIR) with the default aspect ratio (4:3 or 16:9) from the union ofprojections by all the projectors. Moreover, the polygons with overlapping projections fromdifferent projectors will also be detected from the feedback and a two-dimensional edgeblending algorithm for non-orthogonal edges will be implemented. The second goal for theprojector array system is the geometric correction. We intend to equip the system with theprocessing module to compensate the projection distortion due to the curvature of the screen.The models of the curved screens under consideration include both parametric andnonparametric ones. For the parametric model we study the case that the curvature of thescreen surface is approximated by the quadratic curve such as the parabola, ellipse, orhyperbola. With known parameters like the distance between the projector and the screen, theaxis length, etc., the geometric correction would be implemented accordingly. For thenonparametric model, implementation of geometric correction is initiated by a test patternprojection. The pattern is an image of a grid net and each side of the net hole is modeled by aBzier curve. All net holes in the original test pattern are rectangular but some might becomedistorted after projected onto the curved screen. By modifying the control points of the Bziercurves to rectify all the distorted net holes the geometric correction can be completed.
近年來隨著文化創意結合多媒體應用的蓬勃發展,使得與資訊顯示相關的設備產業吸引不少關注。大量的資源投入面板與投影機的研究,希望能開發出更清晰,更具娛樂效果的顯示科技,以帶給觀眾一流的視覺享受。其中,因投影機的成像大小不受機體本身的尺寸限制,若結合電腦控制以及後製的特效影片,往往能造成令人驚嘆的視覺效果,如環場影像、3D 影像和虛擬實境等等。這些視覺特效常常是由一個投影機陣列系統,將影像投射到一個曲面螢幕所完成。然而,因系統造價昂貴,且系統參數設定自動化程度有限,須由專業人員維護,使得類似系統的應用只侷限在大型的活動空間如大型展場、戲院或露天音樂會場等。最近,微型投影機的發明使得上述特殊視覺效果的個人化變的可能,而投影機陣列的應用也可因此進入個人遊戲(game)的領域。有鑑於此,我們希望透過此計畫,探討相關的影像處理技術,建置一個中小型,中低成本,適合個人維護的投影機陣列系統。本計畫擬建立一個二維投影機陣列系統,由四台投影機 (2 乘2) 組成,並可在曲面螢幕上投射出正常影像。其中牽涉到幾個核心技術,包括影像柔邊,影像縫合,幾何修正等等。由於四台投影機擺放的位置不同,投影亮度也不同,在建置系統時如何讓最終成像盡量方正,並使亮度盡量匹配,將是第一個挑戰。我們預計藉由一台網路相機來進行自動校正的工作。4 台投影機擺放完成後,投影一個測試畫面至一個平面螢幕,相機將畫面傳回電腦分析,找出四台投影機協力投影所形成的聯集區域,再找出此區域內最大4:3 或16:9 的矩形,此矩形即為最終成像範圍。此時,電腦也記錄了重疊投影的區塊,這些資訊將用來做為影像柔邊的依據。由於這些區塊是來自不同投影機的重疊投影形成的任意多邊形,使得柔邊的複雜度大為提升,而這也是本計畫第二個挑戰。完成投影機陣列系統的建置後,便是做幾何修正。我們考慮的方式有兩種,第一種假設曲面螢幕的曲率是二次曲線,我們可參考拋物線、雙曲線和橢圓的公式,測量必要的參數(如投影機至螢幕的距離、各種軸長等),依相似三角形原理求出個別曲線所需的修正量。這種方式可快速完成幾何修正,但是不適合曲率是二次曲線以外的螢幕曲面。第二種方式則不假設曲面的曲率,先由Bézier 曲線畫出網格影像,這個影像含有,例如,400 乘300個網格,每個網格都是正方形且網格的邊都有Bézier 曲線的控制點,我們將這個影像投影至螢幕曲面上,藉由調整Bézier 曲線的控制點把任何因曲面造成的變形修正回來,即可完成幾何修正。這種方式可以修正極大範圍的曲率種類,但是相對的需花較多時間才能完成修正。最後要強調的是,所有的核心演算法都會以平價硬體執行的可能性為考量,希望藉由本計畫的執行,促成平價全硬體投影機陣列系統的誕生。
URI: http://hdl.handle.net/11455/49011
其他識別: NSC100-2221-E005-071
文章連結: http://grbsearch.stpi.narl.org.tw/GRB/result.jsp?id=2321950&plan_no=NSC100-2221-E005-071&plan_year=100&projkey=PB10007-0693&target=plan&highStr=*&check=0&pnchDesc=%E5%BB%BA%E7%AB%8B%E5%85%B7%E6%9C%89%E5%B9%BE%E4%BD%95%E4%BF%AE%E6%AD%A3%E8%83%BD%E5%8A%9B%E4%B9%8B%E4%BA%8C%E7%B6%AD%E6%8A%95%E5%BD%B1%E6%A9%9F%E9%99%A3%E5%88%97%E7%B3%BB%E7%B5%B1
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