Detecting and Tracking Multiple Users in the Proximity of Interactive Tabletops

Interactive tabletops allow various opportunities for collaborative work as multiple users may interact simultaneously with the same multimedia content. Despite the fact that the interaction is shared and work is carried out collaboratively by multiple users, it is not always clear who interacts and where as there is no way of knowing where users position themselves at the table. We describe in this paper a method for detecting and tracking multiple users around the physical table using a simple solution implemented with a few short-range distance optical sensors. We are thus able to properly address the following questions: How many users are there? Where are they located around the table? Has a new user approached the tabletop or has someone just left? Are two users close to each other? We believe that answering these questions provides new interaction opportunities enriching thus the overall tabletop experience. We discuss possible applications and describe several implementations