| Gaze tracking is a hot research topic in the fields of multi-media and man-machine interaction. With this technology, the gaze direction or gaze point can be obtained by capturing the motion trail of human eyes. It has a bright future in the fields of computer control, for the characteristics of immediacy, flexibility and naturality.Although the application of gaze tracking technology has tempting prospects and great successes have been achieved in the last few years, the gaze tracking technology can not be widely used in the actual production for the immaturity of various techniques, characters of eye movement itself and the high cost. Some problems have to be solved: improving the accuracy and robustness of the system, improving the degree of freedom, reducing the limitation of users and the complexity of calibration, reducing the complexity of algorithm, and reducing the cost of the system.For the problems above, a head free gaze tracking system based on near infrared lights is taken as the research platform in our paper. Novel ideas and algorithms are proposed for the techniques of image processing, estimation algorithm of gaze points, system calibration and so on. A gaze tracking system with high accuracy, high degree of freedom and low cost is realized with our algorithm. The main creative researches in our paper are shown as following:1. A difference-based gaze tracking pre-processing scheme is proposed. In the proposed scheme, the gray difference between the face, pupils and reflecting points on the cornea is utilized to detect the eyes. At the same time the reflective optical effects caused by glasses or accessories are removed according to the size, geometric structure and spatial location of pupil and reflecting points by the image processing methods of corrosion expansion, bridge and selection. With this algorithm, the accuracy and robustness of gaze tracking system can be improved.2. The technique of super-resolution is applied in the system. For the local region of the image captured, such as the rough pupil region, the pupil region image with high resolution can be obtained through super-resolution. So the eye characteristic parameters can be obtained more accurately, and the gaze points estimation results can also be improved.3. A novel gaze estimation scheme based on similarity between spatial triangles with two lights is proposed. The gaze points are estimated with the proportion calculations of two similar triangles on image plane and monitor plane respectively. One of the two triangles takes the pupil center of the human eye and the two reflecting points on the cornea in the face image as its three apexes and the other is formed by the two infrared light sources and the gaze point on the computer monitor. This similar triangle-based method can realize the approximate POG estimation in the condition of head free with low complexity.4. The errors caused by the POG estimation scheme above are analyzed in3D space. The analysis results show that the errors have regional characteristic. It provides the theoretical basis for the system calibration and improvement of the accuracy.5. A novel two-stage calibration method is proposed. Compared with the normal calibration method, the calibrating points are used in twice and the monitor screen is divided into five regions for the errors have the regional characteristic. Different POG on the screen are calibrated with different calibrating points in corresponding regions. It makes sure that the scheme having high accuracy in the condition of free head movement.6. Based on the principle of the error generation, more accurate compensation is brought to the gaze estimation results. It improves the accuracy and the degree of freedom further.7. Some creative applications of gaze tracking techniques are proposed. It promotes the application of the gaze tracking techniques to be more extensive... |
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