Digital pens
by Chris Woodford. Last updated: August 24, 2011.
Has there ever been a more amazing invention than the pen—an incredibly convenient way of recording information that dates back thousands of years? The only trouble is, pens and paper are not very compatible with the digital technology that surrounds us in the modern world. It's all very well scribbling little notes to yourself as you sit on the train, but what if you need to put that information into your computer when you get home? Until recently, your only option would have been to read back your notes and type in the information (that is, write it out all over again)—but now there's a better solution: the digital pen. Digital pens look like fatter versions of ordinary pens. Packed with electronic circuits, optical devices, and Bluetooth® gizmos, they can record the things you write as you write them and transmit them automatically to your computer using wireless technology. Sounds amazing doesn't it, so how exactly does it all work?
Photo: A Nokia SU-27W digital pen. It's about four times fatter than a fountain pen, a little bit longer, but not all that much heavier.
The digital desktop
Chances are you already own something quite like a digital pen. If you have an optical mouse (one that works by shining light onto your desk instead of using a heavy, rolling, rubber ball), you're already using most of the technology that a digital pen uses. If you lift up an optical mouse, you'll see there are two optical components underneath: one that shines red light down onto your desk and another one that detects the light as it bounces back up again. The light is produced by a light-emitting diode (LED); right next to it, there's a photoelectric cell—a component that detects the reflected LED light and turns it back into an electrical signal. As you move your mouse around, the pattern of red light reflected off the desk changes from one moment to the next and the circuits inside the mouse use this to figure out exactly how you're moving your hand.
Now, clearly, you could write words with your optical mouse if you wanted to and they would appear on your computer screen—but they'd appear as big, fat, smudgy images not as clearly discernible words: your computer would have no idea what you'd actually written and it would be impossible to import your scribbles into a word-processor to edit them.
What's different about a digital pen?
If you look inside a digital pen, you'll find most of the same
components that are in an optical mouse. The difference is that they're
stacked vertically rather than horizontally: a digital pen is to an
optical mouse what a skyscraper is to a parking lot. Where an optical
mouse tracks your hand movements by reflecting light off your desktop,
a digital pen does the same thing much more precisely by following an
almost invisible grid of lines or pinpoints (depending on which system
you use) on special paper.
A mouse doesn't keep a track of what you do, but a digital pen does: it stores the grid coordinates of the points you move past and, in this way, captures what you write. So that you can see exactly what you're doing, a digital pen also has a conventional refill that leaves an ink trail, just like a normal pen. The ink trail is purely for your convenience: the computer doesn't "see" it or use it in any way. Every so often, you need to upload your writing to your computer. Some digital pens upload when you plug them into a computer with a USB cable, others upload through a docking station that also charges the battery in the pen, while the most sophisticated ones can also transmit words as you write them using a wireless technology such as infrared or Bluetooth
The really neat thing about a digital pen is what happens to the information it captures after it's sent to your computer. Digital pens come with a PC software package that imports the data the pen has stored and decodes it, turning your scribbled handwriting into editable text as good as you could have typed from the keyboard.
