These items are sometimes called "Message Wands", but it seems that
each manufacturer uses a different name for their product.
These devices have a row of light emitting diodes that are repeatedly
switched on and off in a pattern, so quickly that our eyes can't see
the individual flashes, but if we move our head (or move the wand) we
will see bright spots in the correct places to form an image in our
The result is surprisingly effective because of our persistence of
vision: we see the image of a light for a time after the light has
been switched off (or moved to a different part of the overall image),
and our mind combines all the different flashes of light to perceive a
You could make one of these yourself using a digital logic circuit to
drive a row of light emitting diodes. Here are instructions to build a
motor-driven rotating message wand (although you could just leave out
the motor and move your head instead):
"3D Scanning LED Display"
The above page also has a simple animation that shows the principle of operation.
It would probably be cheaper to buy a mass-produced message wand than
to build your own. I found several that can be ordered from Think
1. The Wavy Wand ($30) can display messages and pre-loaded images, or
you can connect it to a computer with a USB cable and download your
own images. You can view the images by waving the wand, or by keeping
the wand still and moving your head or eyes.
2. The Light Talk 2 ($40) works like the Wavy Wand but includes a
scanner so that you can easily load your own designs into the wand.
3. The Spacewriter ($25) also works like the Wavy Wand but is a much
more compact message wand:
4. The XP3 ($50) is a message wand that forms part of a clock, and can
display either the time or a message.
I trust this provides the information that you are seeking.