Our multi-touch tabletop system TwinTable employs a rear-projected display with a diameter of approx. 46″. For the projection, we use an Acer H7350D DLP projector with FullHD resolution. In order to project the image correctly, we had to design a rear-projection mirror fixture system employing three mirrors.

These mirrors have different sizes (small, medium and large) and are mounted into mirror fixtures that were designed by my colleague Simon Lehmann at the Hochschule RheinMain. The small mirror is connected fixedly in combination with the projector to a steel base. The fixtures for the medium and large sized mirrors allow to adjust the mirror’s angle very precisely by rotating a (fine) threaded rod. The medium sized mirror is also fitted into another fixture made out of aluminum profiles in order to hold it in place upside down.

This picture shows the projection scheme with our three mirrors:
Twintable Projection Scheme

The fixtures were produced by the mechanical workshop of our university and turned out very well. However, one could argue that their design is a bit too robust and a bit too precise for their purpose. Well, maybe you can attribute this to the German engineering stereotype :)

Download the CAD files for the fixtures.

Check out the gallery below with our fixtures and don’t hesitate to ask if you have got any questions.

Published by Johannes Luderschmidt

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