Cloak of Invisibility Coming Soon?

Chris writes "The idea of an "invisibility cloak" has made the leap from science fiction books to an international patent application. The "three dimensional cloaking process and apparatus" for concealing objects and people (WO 02/067196) employs photodetectors on the rear surface which are used to record the intensity and color of a source of illumination behind the object. Light emitters on the front surface then generate light beams that exactly mimic the same measured intensity, color and trajectory. The result is that an observer looking at the front of the object appears to see straight through it."

Comments

Jack London's "The Shadow and the Flash"

[dpbsmith]

...is an amusing century-old story about competitive brothers who devise two different methods of achieving invisibility. It's online here.

In his fictional story, both methods have problems. The problems are more than fictional, since one of the methods relies on the nonsense supposition that since black is the absence of light, the only reason you can see something that's black is that the black isn't PERFECTLY black, and that if you could achieve perfect blackness you could achieve invisibility.

However, the method described in the parent article here is equally flawed, since it would work only for an observer placed in a specific view location. One wonders how the equipment is supposed to locate the observer; if there are several observers, how does it decide which of them should be prevented from seeing the object?

The method bears a close resemblance to Hollywood special effects processes (glass shots, matte shots, etc.) Special effects processes are notorious for having visible edge effects if not done carefully, and I'm sure this would be true of the proposed method as well.

In "The Shadow and the Flash," one invisibility cloak could be detected by a sensation of darkness and depression whenever the concealed individual was nearby; the other suffered from occasional rainbow flashes due to mismatches in the index of refraction. I'm sure that the proposed method would have similar problems.