立體攝影辨識物體景深的技術應用於戶外場景

Abstract

立體感知是由於人類雙眼視差所產生的兩張影像，合成後自然形成的感受。也因為如此，人才能識別物體的相對位置。 有關立體視覺的研究中，有些著眼於模擬兩眼取像的架構，分別由一或二台照相機，前後或同時取得一組視差影像；有些則是著重於視差影像相對位置的理論分析，有些是以視差影像為素材進行影像分析比對，分類等工作。 本研究，主要分為二部份：首先，是以一台照相機，在不同位置上各拍攝一次，取得一組視差影像，並對此組視差影像進行分析，求取照相機內部與外部的計算參數。其次，利用照相機的內外部參數，推估其他組視差影像中，各個不同物件的相對位置。 本研究，使用Casio Z4與Pentax S5i二種廠牌的數位照相機進行實驗，分別求得照相機的參數，得迴歸方程式，並以此參數進行物體景深推估。Casio照相機的迴歸方程式為 zd =24.028×b，焦距為24.028；Pentax照相機的迴歸方程式為 zd =25.637×b，焦距為25.637。其中：z: 標記物件與照相機的距離(單位為公尺)，d:兩張視差影像中，對應的標記物件間之間距(單位為像素)，b: 兩次拍攝相機的水平距離(單位為公分)。並在師大圖書館美術展場，分部校園進行取像，並分析各物件的景深。

Stereoscopic scene of the mankind is naturally caused by synthesizing two images produced by the parallax of the two eyes of human. Such being the case, mankind can distinguish the relative position of the objects. In the study of related stereovision, some persons aim at the framework of taking simulated images with two eyes using one or two cameras from front and back or simultaneously at the same time to obtain a pair of parallax mages; someone pay more attention to the theoretical analysis of the relative positions of the parallax images, and some others do the work of using parallax images as material to carry out the job of image classification, comparison and analysis. The study is mainly divided into two parts: Firstly, we used a camera to take a shot on each different position to obtain a set of parallax images and perform analysis on this set of parallax images, so as to get the calculation the intrinsic and extrinsic parameters of the camera and find the regression equation. Secondly, we use the equation to estimate the relative positions of each different object in the every set of parallax images. The study used two kinds of digital cameras, i.e. Casio Z4 and Pentax S5i to carry out the experiment to obtain individual camera’s parameter. We find the regression equation as follow, and we use it to estimate the object distance. For Casio, the regression equation is zd=24.028×b, and its focus is 24.028. For Pentax, the regression equation is zd=25.637×b, and its focus is 25.637. Of them: z: the distance between marker and camera (m), d: the disparity of the corresponding point (pixel), b: base line between two shots(cm). We took images at the Exhibition Center of Fine Arts of the Library of National Taiwan Normal University and the campus of its Branch School, and analyzed each object’s image depth.