以消失點及其他形狀特徵作物體定位之研究及其在電腦視覺上之應用

Abstract

電腦視覺向來被視為是具有高度潛力來模擬人類視覺感官的研究領域。在此領域中，物體定位是一重要的課題，也就是如何透過物體上的一組特徵，來決定相機與物體之間的相對位置。而在多種特徵中，消失點因具備良好的特性而常被運用。 本論文宗旨在於針對物體定位的問題提出新特徵，同時以消失點為主要特徵，輔以其他形狀特徵，提出了四種基於電腦視覺技術作物體定位的方法，分別應用於三度空間滑鼠之設計、直昇機場定位、室內自動車定位以及室外自動車定位。 本論文首先提出一個關於拋物線的消失點的新理論，對其存在性及六種性質都有所探討；一般傳統所用特徵不外乎點、線、或直線的消失點，本論文提出的新特徵理論具有擴增特徵群，以及增加電腦視覺技術處理各式環境能力的特殊意義。 目前虛擬環境的應用與日俱增，各式三度空間輸入裝置在其中佔有舉足輕重的地位，本論文針對此類需求，提出一種新的輸入方式：由內視外三度空間滑鼠。現今所研究的電腦視覺式三度空間滑鼠，都是由外在的攝影機觀察分析手部運作，本滑鼠的設計理念恰好相反，由手握小型攝影機觀察外部標記，並將整個系統降為攝影機校正的問題。 航空飛行員的負擔十分沉重，自動化或輔助飛行無疑是一大福音，本論文針對此類問題，提出一個以電腦視覺作直昇機場定位的方法。現存以電腦視覺作飛行自動化的研究，皆侷限於以運動分析來探討一連串影像的技巧，本論文指出一種利用單張影像計算作飛行輔助的可能，其要點在於分析標準直昇機場在直昇機落地點所畫之標記影像。 運用現有環境所含資訊來作自動車導航是一理想的導航模式；在室內環境中，天花板具有不易被遮蔽及簡單形式的優點，本論文提出的第三種方法，主要用意在於利用天花板上的直線當導航資訊，以其消失點和其斜率的變化作室內自動車的定位。此外，鑒於前一種方法是針對直線行進時的定位，本論文另提出一種車輛轉彎時的定位方法，其主要用意在於將彎路視為拋物線，並讓車輛順著彎道行進做彎路航行。 最後，本論文所提的各個方法均具有公式解，且都已由實驗證明其正確性及可行性。

The field of computer vision in which visual sensors such as cameras are utilized is highly recognized as having great potential to simulate human eyes. In the field of computer vision, one of the most important problems is object location estimation which means to determine the relative position and orientation between a camera and a set of features such as points detected on an object. Among various kinds of features, the vanishing point is a desired one due to its good properties. In this study, one purpose is to extend the family of features by proving a new theorem about the vanishing point of a parabola. Another purpose is to design some new approaches, using vanishing points and other shape features, to solve the problem of object location estimation for various computer vision applications. Four approaches have been proposed, which deal with the following applications: design of three-dimensional mice, location estimation of helicopter landing sites, and localization of autonomous vehicles. In the following, for the derived theorem and each of the proposed approaches, the employed methodology, the experimental results, and some concluding remarks are described. The vanishing point of a parabola is a new shape feature found in this study. In the new theorem about the vanishing point of a parabola, six properties of this new shape feature are proved. Traditionally utilized features include points, lines, vanishing points of lines, and so on. The discovery of the vanishing point of a parabola broadens the family of features and promotes the ability of utilizing various kinds of environmental information for computer vision applications. More and more three-dimensional input devices are required for human-computer interaction in the world of virtual reality. In this study, an inside-out vision-based three-dimensional mouse is proposed. The basic way to manipulate this type of device is to hold a camera to view a square mark in front of it. This is a new idea since all other vision-based three-dimensional mice are outside-in. Automatic landing systems can alleviate heavy burdens on aircraft pilots. In this study, a new approach is proposed to estimate the location of a helicopter landing site. All other existing vision-based methods for aircraft landing are based on motion analysis of a sequence of images. The proposed method instead achieves aircraft location estimation by using monocular images. The principle is to utilize information contained in an international identification mark on the helicopter landing site. One desirable way for vehicle navigation is to utilize information existing in environments. Among various kinds of indoor information sources, ceilings have the good properties of being less occluded and having uniform patterns. The third approach proposed in this study achieves vehicle localization by utilizing ceiling information. The location and the lateral position of the vehicle are derived by using the parallel lines on the ceiling. Finally, while the former method is for indoor vehicle navigation following a straight line, it is also desired to conduct vehicle localization in an outdoor road turning session. And this goal is achieved by the fourth proposed approach. The idea is to view a curve as a parabola and to let the vehicle follow the curve in the turning process. Experiments have also been conducted to prove the correctness of the derived theorem and the feasibility of all the proposed approaches.