Abstract

This study investigates the influence of the eye-camera location associated with the accuracy and precision of interpolation-based eye-tracking methods. Several factors can negatively influence gaze estimation methods when building a commercial or off-the-shelf eye tracker device, including the eye-camera location in uncalibrated setups. Our experiments show that the eye-camera location combined with the non-coplanarity of the eye plane deforms the eye feature distribution when the eye-camera is far from the eye’s optical axis. This paper proposes geometric transformation methods to reshape the eye feature distribution based on the virtual alignment of the eye-camera in the center of the eye’s optical axis. The data analysis uses eye-tracking data from a simulated environment and an experiment with 83 volunteer participants (55 males and 28 females). We evaluate the improvements achieved with the proposed methods using Gaussian analysis, which defines a range for high-accuracy gaze estimation between and . Compared to traditional polynomial-based and homography-based gaze estimation methods, the proposed methods increase the number of gaze estimations in the high-accuracy range.

Highlights

  • Researchers and companies constantly aim to improve eye trackers’ accuracy and precision

  • This section proposes two distinct methods, i.e., eye-camera location compensation and eye feature distribution undistortion. The former focuses on figure out how the gaze estimation accuracy changes according to the eye-camera location; the latter underlines the problems relate to the non-coplanarity eye plane in interpolation-based methods

  • The evaluation considers the gaze error offset in degrees between the actual viewed targets’ coordinates and the gaze estimations

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Summary

Introduction

Researchers and companies constantly aim to improve eye trackers’ accuracy and precision. Accuracy is the average difference between the gaze estimation and the actual stimuli position. Precision is the eye-tracking method’s reliability to reproduce the same gaze estimation in successive samples. This work refers to the mapping from gaze estimation onto ground truth as gaze error in pixels or visual angle degrees. Some gaze estimation methods can achieve high-accuracy when the gaze error is 0.5◦. High-accuracy gaze estimation is essential to describe the actual user’s Point-ofRegard (PoR) truthfully. Some applications with minimal stimulus require very accurate gaze estimation, such as reading analysis, attention maps, human–computer interaction, among others, and small uncertainties could be very critical to such studies

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