Building a Rear Projection Touchscreen

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The biggest challenge in building a rear projection touchscreen has been finding a material that provides enough clarity for the projection, while having enough stretch for the Kinect camera to sense a change in depth.

I bought a couple samples of spandex blends and stretched them over a wooden frame to test the quality of a rear-projection. In the end, I went with the Matte Lycra (20% spandex, 80% polyester) because it supported a clearer projection. The fabric has a slight off-white tinge to it, but when stretched tight enough it isn’t noticeable.

matte lycra

To start, I built a wooden frame to support the screen. The Kinect camera has a 640×480 resolution, so I maintained this ratio and built the screen to be 4 feet wide by 3 feet tall. To ensure the structure was sturdy, I used 4 angle plate corner braces.

Frame

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Corner braces, and a long screw holding the beams together

I managed to build a fairly strong structure, painted it grey so it had a finished look that didn’t stand out, and used a staple gun to tightly secure the fabric to the frame.

To create the ‘touchscreen’ portion of this project, I used a Kinect camera and projector. The projector is used to display the image on the screen (projecting from behind), while the Kinect camera senses if anyone has poked it. Because the Kinect camera can sense objects in 3D space, it easily detects a change in depth on the screen.

I positioned the Kinect directly behind the screen, exactly far enough away that the entire image it captures directly aligns with the dimension of the screen. Next I positioned the projector so that it projects the image upwards onto the screen, exactly matching the area captured by the kinect camera. If the projection doesn’t perfectly align with the captured area of the kinect, the precision of the touchscreen will be affected.

Rear-projection touchscreen setup, with the Kinect camera directly behind the screen while the projector projects upwards.
Rear projection touchscreen once setup

I used this rear projection touchscreen to display Tweelo, my thesis project at Emily Carr University of Art and Design.


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