Today i received a master-thesis from a friend who graduated two days ago.
Here is a summary:
“Abstract
Even though multi-touch screens based on frustrated total internal reflection
(FTIR) principle have gained significant popularity over the last years their
overall performance is often limited by design. In particular, we identified robustness
towards ambient light, high-speed tracking and precise calibration as key
issues in many systems. In this thesis we propose a set of software and hardware
extensions for a custom-built FTIR screen that improve on these aspects by reducing
the impact of ambient light, optimizing tracking performance and performing
an automated calibration at high precision. Comparisons with existing approaches
reveal great optimization potential: Our system performs well under intense and
rapidly changing lighting conditions, its tracking runtime is up to 30x faster than
Touchlib and calibration achieves sub-pixel resolution. The results are general
enough to apply equally well to other camera-based technologies and might influence
the next generation of multitouch processing software.
Despite its research history, only in recent years with the introduction of the
FTIR1 approach the number of researchers and enthusiasts realizing the potential
of the technology grew significantly. Several companies [Mic07, Per07, IB07]
have also developed products based on FTIR or closely related technologies. Even
a small selection of libraries and SDKs dedicated to multitouch-specific processing
tasks are openly available and the acceptance of the technology is increasing.
Still, the used software and hardware components are in a very early stage.
Over the course of a year we have seen many different system configurations, but
were mostly disappointed of the overall performance. First, either tracking accuracy
or latency or both altogether were not satisfying enough to use the touch
screen as a primary human computer interface (HCI). Second, the lack of robustness
towards ambient light limit their applicability. Third, systems exhibit errorprone
calibration methods based on tedious manual procedures. We identified
these three aspects as key issues that deserve a more thorough discussion.
This thesis aims to present ideas from established research areas, translate
them to this domain and discuss how they apply and perform.”
Basically we connected the cameras with LED frame...simple explanation 
cheerz
goat