How to: Make your own Magic Eye picture
Stereograms, or Magic Eye pictures are sometimes tricky to view until you get the knack, but they are really simple to produce using a flatbed scanner.
Flatbed scanners have a light source that goes right across the whole width of the window, but the actual image is picked up through a tiny lens in the centre of the scanning head. This means that if you scan a single 3D object twice, once from the left, and once from the right of the glass plate, you end up with the same image, but taken from 2 slightly different angles.
Save both images, align them a couple of inches apart on your computer monitor, (or paste them side by side in a document for printing) and defocus your eyes. Hey Presto! a three dimensional image appears to float somewhere in mid-air between you and your screen or page.
Try it, it couldn't be simpler :)
Here's one I made earlier - see wertperch.co.uk/gallery Page 15