Broadcasting hidden messages to cameraphones using IR light

I recently came across an interesting feature of cameraphones, which I think is ripe for taking advantage of.

This is a picture of a TV remote taken with the camera on my smartphone. You will notice the purple flare from the infrared (IR) LED on the front of the remote, as I press the power button.

image showing infrared light, taken with a cameraphone

That flare is not visible to the naked eye, and is a result of most smartphones not having an infrared filter between the lense and the CCD (charge coupled device- the “film”). Most digital cameras, and some really high end smartphones (notably the recent iPhones) do have a filter, so they won’t see the purple light. Why not try it yourself?

How can this be taken advantage of?

Imagine a series of these IR LEDs arranged to spell a message (or perhaps even a whole scrolling LED display of IR LEDs?). This could be mounted somewhere inconspicuous, but also somewhere where people use cameraphones. Anyone photographing the sign would get the secret message…

Some example uses might include:

  • Messages on the stage at a concert for all the fans recording it or photographing it on their smartphones.
  • Display on the front of a fancy dress costume on a night out (for instance, I’ve noticed that people wearing MorphSuits tend to get photographed a lot by complete strangers!)
  • Shining through a photographable poster. The sort of thing I am thinking of is the modern equivalent of the seaside “head through a hole” photo opportunity – a poster that encourages you to take a picture of it, by either being well designed (so passers by want to pose with it) or via an incentive (send us your photo of one of our posters to enter our contest).
  • as a hidden message on a sign that also features a QR code (which encourages looking at it with a cameraphone).

I am sure there are many other ways it could be applied. If you like, or use, this idea – let me know in the comments! If you REALLY like this idea and want to give me some money for it…!

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