Object recognition in a multitouch environment by combining Diffuse Illumination and Frustrated Total Internal Reflection - Björn Breitmeyer
- © Björn Breitmeyer
Multitouch has become popular in the last years,
as the production of such systems
has become a lot cheaper through optical techniques. All of these techniques
rely on invisible light (mostly infrared) reflections imaged by a camera. One of the more popular techniques is based on the Frustrated Total Internal Reflection (FTIR) effect, it relies on the change of the refraction angle issued through pressure on the display. Another technique is based on Diffuse Illumination (DI) and relies on direct reflections. DI allows us to track and recognize passive markers made of reflective materials. Those can be mounted on any object of the appropriate size. To distinguish markers from each other they can contain unique patterns to uniquely identify the marker and hence the object, such markers are called fiducials. Since our tracking software takes reference frames to remove ambient light, we can easily detect active markers as the they are the only source of light. Through different geometric forms of active markers an object can be identified. Such a geometric form can also originate through pressure of an object in an FTIR setup. The main goal is to combine these methods to create an object recognition that is solid
and fast enough to provide a smooth detection.To achieve this goal the minimum recognizable size of a fiducial has to be detected. The Question is what forms are best for fast and error prone fiducial recognition, a fast algorithm for the fiducial detection and how can a developer combine these techniques in order to get additional information? For example using an FTIR pressure pattern(or an active marker pattern) for detection of a display, like Stefan Elstner  did in his Diploma Thesis and have more than one display which can be distinguished by their fiducial.
Our table has to be refactored to support a fast switching between DI, FTIR and reference frames. After that the question is when do we need which frame?