Algorithm 1: Eye Gaze Based 3D Triangulation Method.

Visual Servoing based Eye Gazing: Gaze the 3D point $\mathit{P}$ at the principal point in the left and right cameras simultaneously through visual servoing based eye gazing. In each loop of the visual servoing: Calculate the joint velocity commands of the robotic bionic eyes using Equations (12) and (13) according to pixel deviation in the left eye and right eye, respectively. Send the joint velocity commands to the robotic bionic eyes and get the feedback of joint angles. 3D Triangulation by Calculation of Intersection Point: Calibrate the head-eye parameters ${}^6{\mathit{T}}_{Cl}$ and ${}^9{\mathit{T}}_{Cr}$ using method in [40]. If visual servoing based eye gazing is successful: Calculate the transformation matrices ${}^N{\mathit{T}}_6$ and ${}^N{\mathit{T}}_9$ using the forward kinematics with joint position feedback. Obtain the optical axes of the left and right cameras using Equations (14) and (16). Calculate the 3D coordinates of $\mathit{P}$ using Equations (22)–(24).