@TechReport{	  it:2007-034,
  author	= {Stefan Seipel and Lars Winkler Pettersson},
  title		= {{P}ixel{A}ctive{S}urface: A Tabletop Rear-Projection
		  Display for Collaboration with Pixel-Accurate Interaction},
  institution	= {Department of Information Technology, Uppsala University},
  department	= {Division of Human-Computer Interaction},
  year		= {2007},
  number	= {2007-034},
  month		= dec,
  note		= {Extended abstract appeared in ACM Conference on Supporting
		  Group Work (GROUP'07).},
  abstract	= {The use of table-top displays as working environment
		  provides a very natural way to present and interact with
		  information. In particular when several users intend an
		  unhindered face-to-face dialogue, horizontal displays have
		  been introduced as efficient tools for collaborative work
		  in shared physical spaces. Many of the hardware systems
		  presented so far are composed of several independent and
		  technically often clumsy components for the display and for
		  tracking of users' head positions or gestures,
		  respectively. This hampers, in practice, easy operation and
		  a more widespread use of table-top displays in real working
		  environments. In this paper, we present our technical
		  solution for a fully integrated, small sized table-top
		  visualization environment that provides head position
		  tracking for two collaborating users, stereoscopic
		  projection and high resolution multi-point screen
		  interaction. Our solution is intended as a self-contained
		  out-of-the-box system that is affordable and easy to use.
		  The real novelty with our technique presented in this paper
		  is, however, that we succeeded in combining high resolution
		  and multi-point pen-based interaction technology based on
		  optical pattern recognition with a rear-projection screen,
		  which opens up for a wider field of applications not only
		  limited to tabletop display environments.}
}