Wang Xi, Holmqvist Kenneth, Alexa Marc
TU Berlin, Germany.
Regensburg University, Germany.
J Eye Mov Res. 2019 Sep 9;12(4). doi: 10.16910/jemr.12.4.2.
The point of interest in three-dimensional space in eye tracking is often computed based on intersecting the lines of sight with geometry, or finding the point closest to the two lines of sight. We first start by theoretical analysis with synthetic simulations. We show that the mean point of vergence is generally biased for centrally symmetric errors and that the bias depends on the horizontal vs. vertical noise distribution of the tracked eye positions. Our analysis continues with an evaluation on real experimental data. The estimated mean vergence points seem to contain different errors among individuals but they generally show the same bias towards the observer. And it tends to be larger with an increased viewing distance. We also provided a recipe to minimize the bias, which applies to general computations of gaze estimation under projection. These findings not only have implications for choosing the calibration method in eye tracking experiments and interpreting the observed eye movements data; but also suggest to us that we shall consider the mathematical models of calibration as part of the experiment.
眼动追踪中三维空间的兴趣点通常是通过视线与几何图形相交，或者找到最接近两条视线的点来计算的。我们首先从理论分析和综合模拟开始。我们表明，对于中心对称误差，平均辐合点通常存在偏差，并且该偏差取决于所跟踪眼睛位置的水平与垂直噪声分布。我们的分析接着对实际实验数据进行评估。估计的平均辐合点在个体之间似乎包含不同的误差，但它们通常对观察者表现出相同的偏差。并且随着观察距离的增加，偏差往往会更大。我们还提供了一种将偏差最小化的方法，该方法适用于投影下注视估计的一般计算。这些发现不仅对眼动追踪实验中校准方法的选择和观察到的眼动数据的解释有影响；还向我们表明，我们应将校准的数学模型视为实验的一部分。
