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Optical Camouflage
Mike Siekkinen writes "This optical camouflage project is pretty interesting. It contains three videos demonstrating it in action. Basically they overlay a video projection of what the background behind the object to be camouflaged looks like. So if you were standing in front of a book shelf an image of the portion of the bookshelf you are blocking would be projected on to you. The results are probably better than you would expect."
A number of posters on those site feel it's no big deal, a guy holding things in front of a projector... That's what I thought at first. But what I can't figure out is why doesn't the image show on the guys hands and face. You'd think at least some light would be reflected off of his hands.
I dunno, the half-way mirror thing kind of limits this application. Not to mention the parralax problems you'll get with an audience that is spread out.
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I will admit that this works better than I expected from the video clips. But I think it's barely halfway towards the goal of personal optical camouflage. From what they describe, it requires an external display source, and applies a bluescreen style approach.
What they need to do is figure out a way to create a piece of clothing which *is* the display, and not merely a reflector or a bluescreen like what they have now. Maybe take this foldable display technology I've read about (mainly geared towards disposable displays), and attach it to fabric. Then make a uniform out of it. Then, you can determine the image behind the person and display it on the uniform.
They're already halfway there, since they can determine what's behind the person and display it on a special colored material. Now all they need is a fabric that can display images, and then they can transmit the background onto the uniform.
Then we're talking about optical camouflage.
Two giant problems jump right out at me.
One: depth perception. Because we're watching movies of the demonstration instead of seeing it in person, it looks fairly good. But if you saw this technique in person, with binocular vision, you would be able to tell without any difficulty what you were seeing. If the background is sufficiently cluttered-- like a jungle backdrop-- and if the camouflaged thing is stationary, it might be good enough to fool a passing glance. But then again, so is your average ghilie suit.
Two: parallax. (This has been mentioned upthread already.) The demonstrations are all shot with a stationary camera. If the camera were to move, the illusion would be ruined. I'd imagine from looking at the illustrations that the geometry of the projector, reflector, mirror, and observer are all pretty critical. If the observer takes a step in any direction, the illusion will be broken.
All in all, I can't see how this could ever be practical. The most important flaw is that it's not even remotely adaptive. You have to have a perfect still photograph of your background to project against the mirror. If a bird flies behind the camouflaged object or person, the game is up.
Neat trick, but not very impressive.
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Since this scheme is only good for hiding from one watcher at a time, and only from a one-eyed watcher when close, it seems that a simpler method will work.
Hold a rear-projection screen in front of you as a shield. It will have a pole coming toward you, that is long enough so the end of it is behind you when you hold the shield. On this end is a camera looking at the scene behind you.
Now it works without half-silvered mirrors, it is portable (you carry it around), and it works even if the background is moving.
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