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A supplementary video of a publication about Touch Sensing based on FTIR in the Presence of Ambient Light in 2008 created at the TU Berlin, Computer Graphics Department.

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A low-cost multi touch table based on FTIR technology. The display and interaction area is approximately of the size of A0 (1.3m diagonal). The robustness of touch detection is enhanced by synchronizing IR illumination with the camera to allow measuring of ambient light.

Origin

The project took place in winter 2007/2008 at the TU-Berlin, Department of Computer Graphics. The team consisted of 11 students who worked on it for approximately 6 months: Björn Bollensdorff, Ingo Breßler, Stefan Elstner, Nino Kettlitz, Norbert Lindow, Robert Lubkoll, Ronald Richter, Claudia Stripf, Sebastian Szczepanski, Karl Wessel and Carsten Zander.

Description

The project covered the construction of a multi touch table from scratch. In each project phase, small groups of students worked on different areas, in general: hardware and frame construction, camera and image acquisition, rear-projection and materials, IR-illumination and electronics.

  • 1st project phase
    • in-depth research for appropriate materials
    • optimal hardware design with constraints in size, costs and usability
  • 2nd project phase
    • construction of a frame from wood, installation of mirror, camera and projector
    • development of video and image processing software for robust touch detection at 60fps
  • 3rd project phase
    • development of a software interface for easy application prototyping and testing
    • developing applications (4 person Pong clone, sound synthesiser, hyperbolic viewer, etc.)

Since then, the device received further improvements by following projects and groups. For the current state, please visit the official project page.

Contributions

As part of the projection group during the first project phase I researched appropriate rear-projection screens which perform well on top of a silicon layer and being touched permanently. Additionally, I experimented with mirrors and the ghosting effect, as well as deriving a first surface mirror from a regular mirror by removing the back protection layer (which doesn’t work well with common chemicals available in Germany).

In the last project phases I joined the software team for developing a touch detection framework for server/client environment with various testing utilities. Within the core library I worked mostly on background subtraction, synchronization and a stable blob detection algorithm based on the OpenCV library. There is source code documentation of the framework called Touching from late spring 2008 available.

Together with Claudia Stripf, we created a Trautonium simulator software based on this multi touch table. Please see its description on her website for details. There is also source code documentation of this client application called mtSoundz from late spring 2008.

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