Notes about illusion

May 12, 2010 permalink

Potemkin Army

The Discover blog reports on a Potemkin army:

Russian balloon maker Rusbal is working on an order from the country’s defense ministry to supply full-scale inflatable military models. The realistic-looking hardware is used in battlefield positions and to protect Russian strategic installations from surveillance satellites, distracting snoops and protecting real combat units from strikes. They can look like real vehicles in the radar, thermal, and near infra-red bands, so they’d even look right through night-vision goggles.

And now from Shakespeare’s Macbeth (Act V Scene IV — you know, the cool part where the incoming army disguises itself as the Birnam forest):

    Let every soldier hew him down a bough
    And bear’t before him: thereby shall we shadow
    The numbers of our host and make discovery
    Err in report of us.

Nothing much new, then. Simple visual misdirection is the magician’s greatest asset.

See also:

  • Edison’s Warriors, a great article in Cabinet about the U.S. 3132nd Signal Service Company in WWII, a sonic deception team that created strategic disruption using wire and tape recordings with acoustical engineering help from Bell Labs
  • Operation Bertram
  • The Ghost Army

August 23, 2009 permalink

Touchable Holography

“Touchable Holography”, a hardware demo by researchers from the University of Tokyo at this year’s SIGGRAPH conference. This mostly builds on the work they presented last year involving their “Airborne Ultrasound Tactile Display” (PDF), a device that shoots out directional ultrasound to simulate haptic pressure, like the impact rain has when it hits your skin. I don’t think this current display counts as holography exactly (the image is made with a refracting mirror, just like Sega’s 1991 arcade game Time Traveler!), but being able to reinforce the illusion with the sensation of touch is a cool idea. Hopefully they can expand it to use more than one of their ultrasound boards so they can simulate a feeling that’s more than one-dimensional. Also good to see that researchers are using the inexpensive, off-the-shelf Wiimotes for projects like this.

(Via Make)

August 8, 2009 permalink

Transformation optics as misdirection

From Nature, Optics: All Smoke and Metamaterials (subscription might be required, actual research publication available from the American Physical Society):

Seeing is believing — a naive assumption in the case of an illusion device proposed by Lai and colleagues at the Hong Kong University of Science and Technology, and described1 in Physical Review Letters. The new device has the power to ‘act at a distance’ and therefore covertly alter an object’s appearance such that it has no apparent physical connection to the light scattered by the object — although this becomes increasingly difficult to achieve the farther the illusion device is from the object. Lai and colleagues1 outline a mathematical formalism proving that it is theoretically possible to grab the rays of light emitted by a given object and to reconstruct them so that they seem to come from a completely different object.

Using metamaterials with refractive indexes less than zero to disguise the origin or content of reflected light. Not sure that I entirely understand this idea, but it’s sort of like the fabled “cloaking device”, except that instead of rendering an object invisible it actually renders it as a different object. Things will be weird fifty years from now.