Students at the University of Rochester have developed a clever optical system which allows for limited invisibility thanks to a bit of optic
Almost all invisibility technologies work by taking light and passing it around the object as if it were never there. The problem is, a lot of these methods are very expensive and not very practical — and don’t even work if you change your perspective from a head on view.
[Joseph Choi] figured out you can do the same thing with four standard achromatic lenses with two different focal lengths. The basic concept is each lens causes the light to converge to a tiny point in between itself and the next lens — at which point it begins to diverge again, filling the following lens. This means the cloaked area is effectively doughnut shaped around the tightest focal point — if you block the center point of the lens, it won’t work. But everything around the center point of the lens? Effectively invisible. Take a look at the following setup using lasers to show the various focal points and “invisibility zones”.
Continue reading “Invisibility Achieved with a Few Clever Focal Points”
It was supposed to be a routine mission for U.S. Air Force Lt. Col. Darrell P. Zelko, a veteran pilot of the 1991 Gulf War. The weather over the capital city of Serbia was stormy on the night of March 27th, 1999, and only a few NATO planes were in the sky to enforce Operation Allied Force. Zelco was to drop 2 laser guided munitions and get back to his base in Italy.
There was no way for him to know that at exactly 8:15pm local time, a young Colonel of the Army of Yugoslavia had done what was thought to be impossible. His men had seen Zelco’s unseeable F117 Stealth Fighter.
Seconds later, a barrage of Soviet 60’s era S-125 surface-to-air missiles were screaming toward him at three times the speed of sound. One hit. Colonel Zelco was forced to eject while his advanced stealth aircraft fell to the ground in a ball of fire. It was the first and only time an F117 had been shot down. He would be rescued a few hours later.
How did they do it? How could a relatively unsophisticated army using outdated soviet technology take down one of the most advanced war planes in the world? A plane that was supposed be invisible to enemy radar? As you can imagine, there are several theories. We’re going deep with the “what-ifs” on this one so join us after the break as we break down and explore them in detail.
Continue reading “Ask Hackaday: How Did They Shoot Down a Stealth Aircraft?”
Once again it’s time for you, the sharp-eyed readers of Hack a Day, to decide whether the following video demonstrates technology at its finest, or if it is complete hogwash. This edition of Real or Fake? is brought to us by Hack a Day reader [Wizzard] who sent us a link to “The Invisible Camera“
Watch the video embedded below to see the unveiling of this camera as well as a discussion of its new, revolutionary technology by its creator – photographer Chris Marquardt. The camera is composed of a simple, non-moving lens mounted in a completely transparent box made of specially polarized glass. This glass is supposed to align the ambient lighting, which amplifies the energy coming through the lens, in order to expose the special film they created for the camera.
The film was developed using standard film “combined with innovations in chemistry” to produce ultra-low sensitivity image media, which the creators are calling “Directionally Desensitized” film. This film can be handled in full light, as it is only sensitive to the high-energy light directed on its surface by the aforementioned lens. It is claimed that due to this special film, the camera goes beyond the Megapixel, past the Gigapixel, and captures images in Terapixels.
Now, call us skeptical, but isn’t it a bit early for April Fools jokes? We just can’t imagine any scenario where holding a piece of film in the sun as shown in the video would not cause it to be exposed in at least some areas due to the massive amounts of reflected light in the environment.
What’s your take?
Continue reading “Terapixel images and see-through cameras: Real or Fake?”