Figure 4.

Error analysis of eyeball center estimation. (a) Error zone illustration. The distance between eyeball center and calibration tools are assumed as constant values. The r-axis refers to the line connecting $\mathit{E}$ to the midpoint of ${\mathit{P}}_{12}{\mathit{P}}_{22}$. (b) The relationship between $S$ and $R_1$, $R_2$ when $\theta =90°$,$\mathsf{\Delta }d=10 \mathrm{mm}$. Note that the white region in the heat maps means the error is larger than $1000{ \mathrm{mm}}^2$, and we do not show the detail for better observation.