3. How The Fly Works, Continued

Let's look at some specific aspects of Anoto technology starting at the bottom of the diagram. That's the special Anoto designed paper that is used for pattern recognition. The paper is imprinted with what is called "the Anoto pattern." You can see a bit of the pattern in the circular area at the top of the diagram.

This is very important to understand. The Anoto pattern is not just one page in area. If the full pattern was printed out on paper, you would have 9.9508E+14 pieces of 8.5" x 11" (216mm x 297mm) paper. If spread out one page thick this paper would cover 23.2 million miles2 (60 million km2), about the size of Europe and Asia combined.

The Anoto pattern is so large that Anoto can assign different parts of the pattern to different pen-based computer manufacturers. So, for example, Leapfrog's Fly Paper does not work with Logitech's io2 Digital Writing System and vice versa.

More importantly, the Anoto pattern assures that the pattern on each piece of paper in a tablet or in a ream of paper is unique. The software associates specific user actions and programmatic responses with specific patterns. The specific piece of paper a pattern appears on is irrelevant. As an application is built or run, the patterns on each piece of paper become part of the program and its data.

The patterns also allow a pen computer to recognize characters and other drawn objects. The circular area in the modified Anoto diagram also shows how objects drawn with the pen interrupt the pattern, helping the pen computer sense and interpret what is written.

As with any computer, the processor controls the running of applications. The device at the base of the pen labeled "camera" ("sensor" would be a better word) records the patterns and ink interruptions and sends these on to the processor for interpretation.

Now let's focus on the ink cartridge and force sensor. The replaceable ink cartridge is used for recording information on the Anoto paper. The force sensor tells the processor that the pen is being used for some purpose: writing, drawing or tapping. Applications include printed or user drawn buttons and even words that can be tapped or in some cases hovered over to tell the Fly to initiate some code.