Abstract: The length of an endoscope carried by a robotic arm is determined using computer vision. The endoscope is inserted through a trocar into a body cavity and mounted to a manipulator arm. The position of a fulcrum for movement of the endoscope at the trocar site is determined using input from a force/torque sensor. While images are captured using the endoscope, the manipulator arm withdraws the distal end of the endoscope intro the trocar. Image processing is used to determine when the distal end of the trocar becomes visible in the captured images. The position of the endoscope at the point where the trocar becomes visible is recorded, and the length of the endoscope is determined based on the recorded position.