TY - THES

T1 - The Vanishing Point and Camera Focal Length Auto-Calibration Technology Using the Virtual Shadows of a Walking People From Video

AU - 林, 于翔

PY - 2012/1/1

Y1 - 2012/1/1

N2 - The vanishing point in image is an important parameter for estimating the focal length. Moreover, the camera focal length is important information to revert the absolute depth information in image. Hence, if the optimized vanishing point can be confirmed, the absolute depth information in image can be generated easily. In this thesis, a new method to estimate an optimized focal length and vanishing point in image is proposed. In previous approach, the vanishing point estimation focuses on finding the parallel lines in image or the head-feet position of a people in different frames. In proposed approach, the set of virtual shadows of a walking people has been created. Moreover, the length increment of the set of virtual shadows will be computed after the coordinate transformation, an optimized vanishing point can be obtained quickly by using a special iteration method. First, the walking people will be tracked and the leg-crossing posture of this people will be filtered in each frame, by using background subtraction process. Moreover, the projection vector is proposed to create a set of virtual shadows, in order to transfer the head-feet coordinates of these virtual shadows to World Image Coordinate System (WICS). A special relationship between the set of virtual shadows and the vanishing point in image has been found, which is the standard deviation of the set of virtual shadows will decrease, when the transformation point close to the optimized vanishing point. By using this special relationship, a special algorithm can be developed to approach the optimized vanishing point. The algorithm base on a range of focal length in general camera, which can defined a special iterative area. In addition, the increment of length of virtual shadows can be observed in this iterative region, than the corresponding vanishing point can be obtained. To sum up the conclusion, the Bisection iteration method and Sequential iteration method can be combined together to approach an optimized vanishing point. The feature of proposed approach is that the focal length information can be obtained use only one camera; additional calibration target won’t be needed. Moreover, the action trajectory of human is not limited. Besides, the low computational complexity features can be applying proposed approach to real-time surveillance systems.

AB - The vanishing point in image is an important parameter for estimating the focal length. Moreover, the camera focal length is important information to revert the absolute depth information in image. Hence, if the optimized vanishing point can be confirmed, the absolute depth information in image can be generated easily. In this thesis, a new method to estimate an optimized focal length and vanishing point in image is proposed. In previous approach, the vanishing point estimation focuses on finding the parallel lines in image or the head-feet position of a people in different frames. In proposed approach, the set of virtual shadows of a walking people has been created. Moreover, the length increment of the set of virtual shadows will be computed after the coordinate transformation, an optimized vanishing point can be obtained quickly by using a special iteration method. First, the walking people will be tracked and the leg-crossing posture of this people will be filtered in each frame, by using background subtraction process. Moreover, the projection vector is proposed to create a set of virtual shadows, in order to transfer the head-feet coordinates of these virtual shadows to World Image Coordinate System (WICS). A special relationship between the set of virtual shadows and the vanishing point in image has been found, which is the standard deviation of the set of virtual shadows will decrease, when the transformation point close to the optimized vanishing point. By using this special relationship, a special algorithm can be developed to approach the optimized vanishing point. The algorithm base on a range of focal length in general camera, which can defined a special iterative area. In addition, the increment of length of virtual shadows can be observed in this iterative region, than the corresponding vanishing point can be obtained. To sum up the conclusion, the Bisection iteration method and Sequential iteration method can be combined together to approach an optimized vanishing point. The feature of proposed approach is that the focal length information can be obtained use only one camera; additional calibration target won’t be needed. Moreover, the action trajectory of human is not limited. Besides, the low computational complexity features can be applying proposed approach to real-time surveillance systems.

KW - 消失點

KW - 攝影機焦距

KW - 座標轉換

KW - 虛擬投影

KW - 世界影像座標系統

KW - 迭代區間

KW - vanishing point

KW - camera focal length

KW - coordinate transformation

KW - virtual shadow

KW - World Image Coordinate System

KW - iterative area

U2 - 10.6342/NTU.2012.01293

DO - 10.6342/NTU.2012.01293

M3 - Master's Thesis

ER -