Measuring the Latency of an Augmented Reality System for Robot-assisted Minimally Invasive Surgery

Minimal latency is important for augmented reality systems and teleoperation interfaces as even small increases in latency can affect user performance. Previously, we have developed an augmented reality system that can overlay stereoscopic video streams with computer graphics in order to improve visual communication in training for robot-assisted minimally invasive surgery with da Vinci surgical systems. To make sure that our augmented reality system provides the best possible user experience, we investigated the video latency of the da Vinci surgical system and how the components of our system affect the overall latency. To measure the photon-to-photon latency, we used a microcontroller to determine the time between the activation of a lightemitting diode in front of the endoscopic camera and the corresponding increase in intensity of the surgeon’s display as measured by a phototransistor. The latency of the da Vinci S surgical system was on average 62 ms. None of the components of our overlay system (separately or combined) significantly affected the latency. However, the latency of the assistant’s monitor increased by 14 ms. Passing the video streams through CPU or GPU memory increased the latency to 147 ms and 256 ms, respectively.