About holography
How they do it
How it works

     About holography

     A hologram is :
     a flat sheet that reveals a 3-dimensional image when it is lit by direct light (from a spotlight, the sun,
     a candle, a flashlight, or a laser).

     A hologram is NOT :
     a 3-dimensional image appearing out of nowhere like you see in Star Trek and such. These are all
     "special effects". In Reality you will always need a holographic plate behind, in front or around the
     image that you see.

     A hologram is NOT :
     a trick with mirrors and lenses, although you do need them to manipulate the laser-light that records
     the hologram. It is possible to produce 3-dimensional images using hollow mirrors, like the famous
     Mirage-bowl, but this has nothing to do with holography.

     A hologram is NOT :
     something you can break into little pieces so that each piece contains the same information as the
     whole thing. This is a common misconception. If you break a hologram which contains an image of,
     let's say, a bicycle some distance behind the plate, you can still see the bicycle in each piece.
HOWEVER, each piece shows the bicycle from ONLY ONE direction !
     By breaking the plate, unlike a photo, the image has not been broken. Instead, the viewing angle of
     the image has been drastically reduced for each shard, which therefore contains a lot less information
     than the whole hologram did. Also, the information is different on every piece, because it shows the
     recorded image from a different angle.