A Review and Analysis of Eye-Gaze Estimation Systems, Algorithms and Performance Evaluation Methods in Consumer Platforms <s> A. 2D regression based methods <s> This paper addresses the accuracy problem of an eye gaze tracking system. We first analyze the technical barrier for a gaze tracking system to achieve a desired accuracy, and then propose a subpixel tracking method to break this barrier. We present new algorithms for detecting the inner eye corner and the center of an iris at subpixel accuracy, and we apply these new methods in developing a real-time gaze tracking system. Experimental results indicate that the new methods achieve an average accuracy within 1.4/spl deg/ using normal eye image resolutions. <s> BIB001 </s> A Review and Analysis of Eye-Gaze Estimation Systems, Algorithms and Performance Evaluation Methods in Consumer Platforms <s> A. 2D regression based methods <s> We describe a system designed to monitor the gaze of a user working naturally at a computer workstation. The system consists of three cameras situated between the keyboard and the monitor. Free head movements are allowed within a three-dimensional volume approximately 40 centimeters in diameter. Two fixed, wide-field "face" cameras equipped with active-illumination systems enable rapid localization of the subject's pupils. A third steerable "eye" camera has a relatively narrow field of view, and acquires the images of the eyes which are used for gaze estimation. Unlike previous approaches which construct an explicit three-dimensional representation of the subject's head and eye, we derive mappings for steering control and gaze estimation using a procedure we call implicit calibration. Implicit calibration is performed by collecting a "training set" of parameters and associated measurements, and solving for a set of coefficients relating the measurements back to the parameters of interest. Preliminary data on three subjects indicate an median gaze estimation error of ap-proximately 0.8 degree. <s> BIB002 </s> A Review and Analysis of Eye-Gaze Estimation Systems, Algorithms and Performance Evaluation Methods in Consumer Platforms <s> A. 2D regression based methods <s> Of gaze tracking techniques, video-oculography (VOG) is one of the most attractive because of its versatility and simplicity. VOG systems based on general purpose mapping methods use simple polynomial expressions to estimate a user's point of regard. Although the behaviour of such systems is generally acceptable, a detailed study of the calibration process is needed to facilitate progress in improving accuracy and tolerance to user head movement. To date, there has been no thorough comparative study of how mapping equations affect final system response. After developing a taxonomic classification of calibration functions, we examine over 400,000 models and evaluate the validity of several conventional assumptions. The rigorous experimental procedure employed enabled us to optimize the calibration process for a real VOG gaze tracking system and, thereby, halve the calibration time without detrimental effect on accuracy or tolerance to head movement. <s> BIB003 </s> A Review and Analysis of Eye-Gaze Estimation Systems, Algorithms and Performance Evaluation Methods in Consumer Platforms <s> A. 2D regression based methods <s> In a video-based eye tracker, the normalized pupil-glint vector changes as the eyes move. Using an appropriate model, the pupil-glint vector can be mapped to gaze coordinates. Using a simple hardware configuration with one camera and one infrared source, several mapping functions – some from literature and some derived here – were compared with one another with respect to the accuracy that could be achieved. The study served to confirm the results of a previous study with another data set and to expand on the possibilities that are considered from the previous study. The data of various participants was examined for trends which led to derivation of a mapping model that proved to be more accurate than all but one model from literature. It was also shown that the best calibration configuration for this hardware setup is one that contains fourteen targets while taking about 20 seconds for the procedure to be completed. <s> BIB004 </s> A Review and Analysis of Eye-Gaze Estimation Systems, Algorithms and Performance Evaluation Methods in Consumer Platforms <s> A. 2D regression based methods <s> Consumers nowadays demand for more convenient human-device interaction (HDI) in every device they use. As a part of the HDI technologies, remote eye gaze tracking (REGT) is getting more attentions. Among state-of-the-art REGT methods, the ones which utilize four infrared (IR) lights have better accuracy and robustness to head movements. In this paper, a novel glint estimation method is proposed, which enables four-glint-based REGT methods to operate with only two IR light sources. Given two glints obtained from IR light sources attached on the upper or lower corners of the screen, the proposed method estimates the other two virtual glints based on mathematical and geometric principles. Then, the point of gaze (POG) can be estimated using a mapping function established between the four glints and the screen through a user calibration process. Experimental results show that the REGT system using the proposed glint estimation method can achieve highly competitive performance compared with the ones which use four IR light sources.1 <s> BIB005 </s> A Review and Analysis of Eye-Gaze Estimation Systems, Algorithms and Performance Evaluation Methods in Consumer Platforms <s> A. 2D regression based methods <s> The paper proposes a modified pupil center corneal reflection(PCCR) hardware method to improve the system accuracy. The modified PCCR eye gaze tracking system, a new version of the PCCR eye gaze tracking system supplemented by the relation between IR LED position and the distance from the eye gaze tracking system to the monitor screen, improves the tracking accuracy within one degree. The system also suggests a circuit that can do power control adaptively between the minimum and maximum power. It is confirmed that the system performs well both for indoors and outdoors in spite of the reduced calculation. Besides, very convenient mouse functions are proposed so that can be used on PC with the eye gaze tracking functions. The user group confirmed their performances that result in high level of satisfaction with excellent tracking function. Above all, the paper suggests the adaptive exposure control algorithm for the proposed system which is robust against light. The adaptive exposure control algorithm presents excellent performance over the existing system for both indoors and outdoors even when the calculation is down to one fifth. <s> BIB006 </s> A Review and Analysis of Eye-Gaze Estimation Systems, Algorithms and Performance Evaluation Methods in Consumer Platforms <s> A. 2D regression based methods <s> Gaze estimation methods play an important role in a gaze tracking system. A novel 2D gaze estimation method based on the pupil-glint vector is proposed in this paper. First, the circular ring rays location (CRRL) method and Gaussian fitting are utilized for pupil and glint detection, respectively. Then the pupil-glint vector is calculated through subtraction of pupil and glint center fitting. Second, a mapping function is established according to the corresponding relationship between pupil-glint vectors and actual gaze calibration points. In order to solve the mapping function, an improved artificial neural network (DLSR-ANN) based on direct least squares regression is proposed. When the mapping function is determined, gaze estimation can be actualized through calculating gaze point coordinates. Finally, error compensation is implemented to further enhance accuracy of gaze estimation. The proposed method can achieve a corresponding accuracy of 1.29°, 0.89°, 0.52°, and 0.39° when a model with four, six, nine, or 16 calibration markers is utilized for calibration, respectively. Considering error compensation, gaze estimation accuracy can reach 0.36°. The experimental results show that gaze estimation accuracy of the proposed method in this paper is better than that of linear regression (direct least squares regression) and nonlinear regression (generic artificial neural network). The proposed method contributes to enhancing the total accuracy of a gaze tracking system. <s> BIB007
In regression based methods, the vector between pupil center and corneal glint is mapped to corresponding gaze coordinates on the frontal screen using a polynomial transformation function. This mapping function can be stated as: f: (X e , Y e ) → (X s , Y s ) where X e ,Y e & X s ,Y s are equipment and screen coordinates respectively. The relation can be presented as described in BIB004 and  : Where n represents polynomial order, a i & b i are the coefficients. The polynomial is optimized through calibration in which a user is asked to gaze at certain fixed points on the frontal screen. The order and coefficients are then chosen to minimize mean squared difference (ε) between the estimated and actual screen coordinates (with known camera coordinates of user gaze), which is stated as: Where a and b are the coefficient vectors and M is the transformation matrix given by: Where M is the transformation matrix, m the number of coefficients and L the number of calibration points  .The coefficients can be obtained by inverting the matrix M as BIB002 : Cherif et al.  used a 5x5 point calibration routine and 2 higher order polynomial transformations while Villanueva BIB003 BIB001 which presents a very high resolution gaze estimation method resistant to head pose without requiring geometrical models. In BIB007 an improved three layer artificial neural network is used to estimate the mapping function between gaze coordinates and the pupil-glint vector. This method is shown to achieve better accuracy than simple regression based methods. A new approach involving only 2 light sources instead of four is implemented in BIB005 where two IR LED induced glints are real and the other two are virtual ones computed mathematically. This is done to make the algorithm more suitable for consumer applications and simplify hardware. The PoG is then estimated using mapping function to relate the four glint locations and screen through a calibration process. A modified PCCR method is implemented in BIB006 to have improved tracking accuracy and suitable for indoor and outdoor use. In this, adaptive exposure control is proposed since the IR LED brightness variations within a PCCR based setup affects pupil detection and gaze tracking to a large extent. 