In this paper, we present a new technology to perform multi Tangible User Interface (TUI) tracking on standard LCdisplays. A lot of existing technologies for tangible user interface tracking use back-or front-projection setups, but they suffer from poor image quality, shadow casting, nonergonomic interaction, and/or large installations. Thus, we introduce a principle that allows using the InfrActables' technology [3] on a large LC-display. It combines simultaneous multiuser input on a display with the advantages of a large flat screen. We use infrared photodiodes (IR-LEDs) mounted behind the display's LCmatrix to track infrared diodes in front of the screen. After initial tests concerning the infrared transparency and sensor characteristics, we developed a proof of concept consisting of 384 sensors, which are addressed through a modular master-slave circuit. Using several interaction devices, multiuser interaction is possible.

Abstract. In this paper, we present a new technology to track multiple active Tangible User Interfaces (TUI) on a projection table. We use a commercial high speed infrared tracking camera with modified firmware. With a special tracking method, we reach update rates of up to 250 Hz with low latencies. At this tracking rate, we are able to track the position, state and the orientation of more than 10 active TUIs on the table. For this, we use specified bit codes which are transmitted by the devices. We developed dedicated hardware (SyncUnit) and software to keep the devices and the high speed camera synchronized. The system of camera, SyncUnit, and devices is fully hardware controlled and delivers event coded tracking data for further usage in interactive applications.

Abstract. In this paper, we present TNT (Touch 'n' Tangibles) -a new combination of several existing hardware technologies, which are integrated into an LC-display. TNT enables users to interact using finger touch and tangible user interfaces at the same time on an active flat panel screen, while maintaining precise identification of all interactive objects and fingers. TNT can accurately distinguish between touch and Tangible User Interfaces input by assigning different time slots to each interactive object using the same sensing technology for both methods. TNT's tracking is not affected by objects on the screen other than fingers and active Tangibles User Interfaces, which makes it ideal for use in brainstorming applications.