Research On The Hawkeye System's Key Technology

Hawkeye replay is a computer system used in cricket,tennis and other sports that can track the path of the ball,record the actual path of the graphic,display the recorded images and predict the future path of the ball.In some sports,such as tennis,Hawkeye system has become part of the referee process,and also a major part of the audience's watching focus.However,the technology of Hawkeye system has been kept secret,and has long been the focus of the research.The main content of this paper is to research the technologies involved in the Hawkeye instant replay system of the tennis game.With the analysis of Hawkeye system,it can be divided into three parts including multi-camera calibration,tennis testing and landing position judgment,and the three-dimensional reconstruction.In our work,we construct the test sites and collect the calibration images and the Hawkeye playback videos.First,we conduct multi-camera calibration.As the camera's height,angle,etc.are fixed when we built the Hawkeye system,we only need once system calibration.As we all know,tennis court is relatively large,and the scale is fixed.The site also has a lot of lines.To fully utilize these properties,the paper chooses Tsai two-step calibration method to calibrate three cameras in our system.Secondly,we detect the tennis and judge its landing position for the video needed by the Hawkeye playback system.Due to the tennis tournament,in addition to tennis as well as athletes and spectators,which have brought great difficulty to the detection of tennis,so the paper combines tennis shape and color,choosing an improved inter-frame difference algorithm based on the shape and area's color to achieve the tennis detection and tracking the tennis'centroid coordinate.According to change of the motion trajectory slope of the tennis before and after its landing,this paper judge the tennis landing position through multi-frame's slope.Finally,we conduct a three-dimensional reconstruction.In accordance with the principle of least squares calculating the object space coordinates,and combing with the calibration parameters of the two cameras and tennis landing coordinates,we estimate the world coordinates,and restore it to the simulation scene using opengl.Meanwhile,we zoom and display the process of tennis before and after landing to achieve Hawkeye playback.In this paper,under VC++6.0 and OpenCV platforms,we develop the Hawkeye system utilizing the proposed method.The experimental results indicate that each part of our method has good performance,and to a certain extent,can assist the penalty judgment about whether tennis is out.