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How Invisibility Cloaks Work

Optical Camouflage: The Complete Invisibility System
One way to make a person appear transparent
One way to make a person appear transparent

Now let's put all of these components together to see how the invisibility cloak appears to make a person transparent. The diagram below shows the typical arrangement of all the various devices and pieces of equipment.

Once a person puts on the cloak made with the retro-reflective material, here's the sequence of events:

  1. A digital video camera captures the scene behind the person wearing the cloak.
  2. The computer processes the captured image and makes the calculations necessary to adjust the still image or video so it will look realistic when it is projected.
  3. The projector receives the enhanced image from the computer and shines the image through a pinhole-sized opening onto the combiner.
  4. The silvered half of the mirror, which is completely reflective, bounces the projected image toward the person wearing the cloak.
  5. The cloak acts like a movie screen, reflecting light directly back to the source, which in this case is the mirror.
  6. Light rays bouncing off the cloak pass through the transparent part of the mirror and fall on the user's eyes. Remember that the light rays bouncing off the cloak contain the image of the scene that exists behind the person wearing the cloak.

The person wearing the cloak appears invisible because the background scene is being displayed onto the retro-reflective material. At the same time, light rays from the rest of the world are allowed to reach the user's eye, making it seem as if an invisible person exists in an otherwise normal-looking world.