The table framework is constructed with some wooden bars and boards, some styrofoam to make the inside bright white and a pane of frosted acrylic glass. The whole table size is 80 cm (height) by 100 cm (width) by 70 cm (depth). Additionally there is some more space needed to install a beamer standing on an socket. The beamer is just fixed with some tape.

The projection of the beamer is reflected by a special mirror (i.e. the reflection occurs straight on the surface of the mirror, there is no extra glass layer above; this is important to avoid duplicated reflections). The rays of light meet the glass surface from underneath. Of course, most of the light is going through the glass, but there is also some light reflected by the lower side of the glass.

Infrared technique
Due to this reflection, it is necessary to use infrared light and an infrared filter, otherwise the camera would be irritated by the reflections of the beamer projection. The filter subtracts light of every wavelength except infrared light. Because of this there are six infrared spots pointing upwards to illuminate the fiducials from underneath. Thus the camera can see the markers while it is not disturbed by ambient light.

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