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

Practicality?

[nuggz]

There are many angles crossing an object, although this may work for simple front to back (as the article states)
I don't think it is that workable for all directions, or even more then a few.

Re:Practicality?

[lars_stefan_axelsson]

I don't think it is that workable for all directions, or even more then a few.

Well, that depends on what you mean by workable.

Just getting the hue and intensity right (and being able to vary those) will go a very long way. It's not for nothing that English fishermen weren't allowed to paint their hulls white in days of yore, or that Mountbatten had his fleet painted pink. (The sky is brigther than the ocean at dusk/night and hence a light hull blends in. And pink works better agains the redder skies of asian waters).

The US Army even conducted trials with lamps on tanks to make them harder to spot as silouettes against the sky on a ridge line for example.

Now, the light trick is unworkable for other reasons (you have to be quick on the switch) should you drive in front of a dark object. So if this process could be automated there's much to be gained.

Now, of course if your main objection that this is far from a cloak of invisibility, that's for certain. But it could be quite useful camouflage.

And kids remember the old adage "A running soldier in a camoflague uniform, looks just like a running soldier in a camoflague uniform." Camouflage is still very much a stationary art. I doubt that tricks like these would change that much.

Better applications

[Twylite]

The article very definately uses the words "detect" (light behind) and "generate" (image in front). This implies it is not some passthrough technology (fiber, etc), but an electronic record and recreation.

If this "clock" could live up to its claims, there are three (possibly more) far more interesting applications that must be considered:

• Holographic photography: the photoreceptors on the back can apparently sense the intensity, colour and trajectory. They can also do this without a lens. Impressive.
• Holographic projection / 3D TV: the light emitters on the front can recreate the image behind the object. In order to do this with enough accuracy to clock an object, they have to recreate the trajectory of the light; failing this they have a 2D image which will be noticable as soon as the viewer moves.
• Realistic looking TV: apart from the 2D/3D problem, TV just doesn't look real because it is poor at depecting matt textures. A glowing, glossy area within your field of vision would certainly attract your attention, even if it fitted into the background.

Given that researchers would be coining it from more down-to-earth inventions like these, I can't really see that the technology - as described - exists or is being developed.

Perfect bad patent

[RichMan]

This is a pretty near perfect example of a bad patent.
1) the idea is pretty obvious (as well as many references in common SF literature)
2) the actual implementation with current tech will be pretty miserable. Put big bright light behind object, make object shine big bright light at viewer. Viewer is blinded by both and as object is indistinquishable the technique is easily demonstrated to the patent requirement level.
3) it serves as a patent stake. Further research into a better/improved technology will have to deal with this patent.

This is a near perfect bad patent that grants the patent holder a big stake in the ground for actually showing very little. And any future work that will actually improve the technique is going to have to deal with the patent.

Still More Limitations

[swb]

It also doesn't do much for your heat signiture. Since so much military surveillance is done with IR, you'd think that the extra heat generated by the thing being cloacked and the cloaking mechanism that it'd glow like a light bulb under IR.