A Tri-Window Intraoral Scanner (Tri-IOS): design and evaluation

Objective.The scanning process of mono-window intraoral scanner (Mono-IOS) is often cumbersome, and the impression accuracy is insufficient for edentulous arches implant rehabilitation. To address these limitations, this paper proposes the design and evaluation of a novel tri-window IOS (Tri-IOS), which is capable of simultaneously capturing occlusal, buccal, and lingual data.Approach.Tri-IOS features a U-shaped configuration of three plane mirrors in its scanning head, creating three virtual cameras. The relative poses of the three virtual cameras are calibrated using a sphere-based fitting method. The system integrates three-directional point cloud inputs per frame by relative poses, followed by iterative closest point algorithm for precise tracking and reconstruction. The system's effectiveness is validated on constructed dataset, and a prototype is built to conduct calibration and imaging experiments.Main Results.The design achieves a scanner head size under 2.5 times the thickest molar width, with synchronized three-directional data acquisition. Results on the constructed datasets showed that the tri-window design reduced impression time to one-third of the mono-window setup. And compared to mono-window, tri-window design enhanced both local detail and overall shape fidelity of the reconstruction results and significantly improved accuracy in edentulous arch implant impressions.Significance.The Tri-IOS demonstrates significant advantages in both impression acquisition speed and accuracy. Furthermore, its mirror-based design exhibits strong potential for miniaturization and productization. It is of significant importance for improving the performance of IOS and advancing product realization.