Counterfeit document makers will soon have their work cut out for them, if one of Europe's most elite technical schools has anything to say about it. Researchers at École Polytechnique Fédérale de Lausanne (EPFL), a university in Switzerland, have discovered a way to print hidden images within a primary image.
Much like the holographic cards you used to play with as a kid, this new printing process hides an image that can only be seen when the original image is turned. To see the second photo that's hidden within the first, you just have to turn the photo 90 degrees.
The process currently only works with inkjet printers, and can only print on thin metal sheets. To create the hidden image, the printer sprays dots into predetermined patterns that make the image visible when light hits it a certain way. The process is called halftoning.
Right now, the new printing technique is only being used for testing. But researchers hope this could be a new breakthrough for combating counterfeit documents, since without the right equipment and materials, this technique would be extremely difficult to duplicate.