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.