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Novel Camera Calibration Method Could Drive Safer Autonomous Vehicles

관리자 2020-02-13 Views 224

Autonomous or self-driving vehicles watch the roads before them using inbuilt cameras. Ensuring that accurate camera orientation is maintained during driving is, therefore, key to letting these vehicles out on roads. Taking us one step closer to realizing autonomous driving systems, scientists from Korea have developed a highly accurate and efficient camera orientation estimation method that will enable such vehicles to navigate safely across distances.

Since their invention, vehicles have constantly advanced. As vehicular technology progresses, it seems that the roads of the near future will be occupied by autonomous driving systems. To move forward on the path to this future, scientists have developed camera and image sensing technologies that will allow these vehicles to reliably sense and visualize the surrounding environment.


While developing this technology, scientists have faced various challenges. One of the most important challenges has been the maintenance of the orientation of inbuilt cameras during straightforward driving; autonomous vehicles navigate and gauge distances using inbuilt cameras that image the world which they’re moving through. But these cameras often get dislocated during dynamic driving. As Prof Joonki Paik from Chung-Ang University explains, “Camera calibration is of utmost importance for future vehicular systems, especially autonomous driving, because camera parameters, such as focal length, rotation angles, and translation vectors, are essential for analyzing the 3D information in the real world.”


Methods of estimating the orientation of cameras mounted in vehicles have been constantly developed and advanced over the years by several groups of researchers. These methods have included computational approaches such as the voting algorithm, use of the Gaussian sphere, and application of deep learning and machine learning, among other techniques. However, none of these methods are fast enough to perform this estimation accurately during real time driving in real world conditions.


To remedy the problem of speed of estimation, a team of scientists from Chung-Ang University, led by Prof Paik, combined some of these previously developed approaches and proposed a novel more accurate and efficient algorithm, or method. Their method, published in Optics Express, is designed for cameras with fixed focus placed at the front of the vehicle and for straightforward driving. It involves three steps. First, the image of the environment in front is captured by the camera, and parallel lines on the objects in the image are mapped along the three cartesian axes. These are then projected onto what is called the Gaussian sphere, and the plane normals to these parallel lines are extracted. Second, a technique called the Hough transform, which is a feature extraction technique, is applied to pinpoint “vanishing points” along the direction of driving (vanishing points are points at which parallel lines intersect in an image taken from a certain perspective, such as the sides of a railway track converging in the distance). Third, using a type of graph called the circular histogram, the vanishing points along the two remaining perpendicular cartesian planes are also identified.


Prof Paik’s team tested this method via an experiment on road under real driving conditions in a Manhattan world. They captured three driving environments in three videos and noted the accuracy and efficiency of the method for each. They found accurate and stable estimates in two cases. In case of the environment captured in one of the videos, the scientists witnessed poor performance of their method because there were many trees and bushes within the camera’s range of view.


But overall, the method performed well under realistic driving conditions. Dr Paik and team credit the high-speed estimation that their method can carry out to the fact that the 3D voting space is converted to a 2D plane at each step of the process.


What’s more, Prof Paik says that their method “can be immediately incorporated into automatic driver assistance systems (ADASs).” It could further be useful for a variety of alternative applications such as collision avoidance, parking assistance, and 3D map generation of the surrounding environment, thereby preventing accidents and promoting safer driving environments.


As far as advancement in research in the field is concerned, Dr Paik is hopeful about the potential of this method. “We are planning to extend this to smartphone applications like augmented reality and 3D reconstruction,” he says.


Title of original paper: Camera Orientation Estimation using Voting Approach on the Gaussian sphere for in-vehicle camera

DOI: 10.1364/OE.27.026600

Name of author: Dr Joonki Paik

Affiliation: Department of Imaging, Chung-Ang University, Seoul 06974, Republic of Korea

About Chung-Ang University


Chung-Ang University is a private comprehensive research university located in Seoul, South Korea. It was started as a kindergarten in 1918 and attained university status in 1953. It is fully accredited by the Ministry of Education of Korea. Chung-Ang University conducts research activities under the slogan of “Justice and Truth.” Its new vision for completing 100 years is “The Global Creative Leader.” Chung-Ang University offers undergraduate, postgraduate, and doctoral programs, which encompass a law school, management program, and medical school; it has 16 undergraduate and graduate schools each. Chung-Ang University’s culture and arts programs are considered the best in Korea.   



About Professor Joonki Paik from Chung-Ang University

Dr Joonki Paik is currently a Professor with the Department of Imaging, at the Graduate School of Advanced Imaging Science, Multimedia, and Film, at Chung-Ang University, Korea. His research interests lie in the fields of image enhancement and restoration, video analysis, object detection and tracking, 3D vision, media art, and computational photography. He has contributed to over 400 research publications and is the lead author of the present paper.

Media contactpaikj@cau.ac.kr