Camera Calibration Based On Vanishing Points Of Multi-image

Among the information obtained from outside environment, 80% comes from human visual perception. The information is delivered from eyes to human brain, then is analyzed and recognized by human brain in according with his or her knowledge and experience. With the emergence and envelopment of the Digital Technology, Computer Vision, taking the place of Humans' cerebra and eyes, can realize the simple function of environment recognition and understanding. The aim of computer vision research is to make the computer possess the capability of obtaining 3D environment knowledge from 2D image. This capability refers to not only the objects' geometrical information perception which includes the information of shape, position, pose and motion etc., but also information describing, storing, recognizing and understanding. Sensor calibration is one of the key techniques in three-dimension environment recognition from two-dimension images. Recently, with the rapid development of digital technique, the continuous descending price of hardware device and the promotional performance of computer, digital camera gains prevalence in practical application. Many systems and software of computer vision utilizes digital camera as their main sensor for data acquirement. Subsequently digital camera calibration gradually becomes the hotspot in the research fields of computer vision and photogrammetry.Many experts and researchers in the fields of computer vision and photogrammetry have already proposed various methods about camera calibration. However, none of them can achieve extensive application. For different purpose and distinct application we have to adopt different calibrating methods.This paper begins from the calibration method based on vanishing points. Firstly several types of traditional calibrating methods and self-calibration methods are investigated, and then the existing drawbacks of corresponding calibration methods are addressed. Aiming at these problems, the new calibrating methods are proposed in this paper, which need no control points and can obtain higher precision based on vanishing points of multi-view. These calibrating methods can be easily operated. When these camera-calibrating methods are applied in three-dimension reconstruction of regular buildings, it can also realize on-line camera calibration.Following aspects about these methods are introduced and focused on in this paper including: (1) line detection and vanishing points calculation; (2) camera calibration based on vanishing points of multi-view; (3) camera calibration based on point-line combination. (4) Camera calibration based on multi-planar grid. 1) Line detection and vanishing points calculation.Vanishing point is the intersection of the lines in image, which are parallel lines before projecting into one image. As the most important factor in the proposed calibration methods, vanishing point are addressed through the whole paper. Generally vanishing points locate at the outside of image frame, even extend into the infinite. Therefore, it is crucial for camera calibration to determine the optimal location of vanishing points. Because vanishing points locate at the intersection of lines, in this paper the technique of Self-adaption Least Square Line Modulate Matching is proposed for extracting line information from images with high accuracy. Because of the existence of image noise, the image lines in parallel usually don't intersect into one point in practical. Therefore based on image line observation, the adjustment model of correlation between line and vanishing point is constructed to determine the location of vanishing point from the viewpoint of photogrammetry. This method needn't project lines to sphere coordinates, also needn't analyze statistic property of lines. When a big amount of redundant lines exist, this method can calculate the optimal location of vanishing points rapidly and accurately.2) Camera calibration based on vanishing points of multi-view.The single-view calibrating method of vanishing points is illustrated in this paper. Based on error analysis, in according with geometry property, line observation is directly related with camera orientation, through adjustment of multi images, a novel calibrating method of vanishing points based on multi-view can be recommended. At the same time, non-linear radial distortion model and geometry constraints are also introduced to this calibrating model for accuracy improvement.3) Camera calibration based on point-line combination.After analyzing the problems of camera calibrating with long lens, and aiming at the camera calibration with long lens and narrow view angle, one calibrating method based on point-line combination is addressed.4) Camera calibration based on multi-planar grid.In according with the geometry property of vanishing points, it can be seen that only two vanishing points cannot be used to calibrate camera. However, based on the constraints between vanishing point and vanishing line, camera calibration can be easily conducted.