Towards a Compact Vision-based Auto-Focusing System for Endoscopic Laser Surgery

Abstract

Endoscopic laser tools have been recently proposed in order to overcome the limitations of state-of-the-art laser tools, by integrating fiber-coupled lasers into flexible endoscopic systems. One of the main challenges in designing such endoscopic tools consists in the focusing of the laser, that requires to be frequently adjusted reducing the reliability of the system and increasing surgeons’ mental workload. To avoid these problems, compact auto-focusing tools have been recently developed, taking advantage of MEMS varifocal mirrors (VM) to allow integration with endoscopic tools. In this paper, we integrate such VM-based tool with a distance sensing algorithm based on 3D surface reconstruction to achieve a complete autofocusing system. We evaluate the performance of the proposed integrated system by ablating lines on plaster block targets at variable distance and comparing the obtained ablation depth and width with that of a fixed focus system. Preliminary results show that the proposed system is able to keep the laser in focus resulting in uniform ablation lines for distance ranges from 14mm to 22mm.