The Pen in the Digital Age

Put a pen in a little child's hand and you'll never doubt the essential naturalness of handwriting and drawing. Nevertheless, the dominance of personal computers has made keyboard users out of all of us, adapting to limitations to benefit from advantages. We live in the twin worlds of the pen and the keyboard, but there is still a divide between them.

Now this is changing. Tablet computers, which capture writing and sketching on their displays, are increasingly prevalent, pushed vigorously by some of the world's largest companies. Digital pens, which write on paper and simultaneously capture what they write, are also on the market.

The world of the pen and the world of the keyboard are converging.

Digital Ink

When handwriting or sketching is captured by one of these devices, it becomes digital ink, a data type that can be processed electronically or sent through a digital network.

Digital ink is not merely a graphic facsimile of writing or drawing. Instead, it is a record of the trace that preserves stroke order, direction, and other parameters as a function of time. The rich information contained in digital ink facilitates many desirable functions, including handwriting recognition and biometric authentication.

Digital ink is a description of how the strokes were produced, so it can be displayed or printed at any size without loss of fidelity. It can also be smoothed intelligently and edited in a structured fashion.

It can also be compressed significantly for efficient storage and communication.

Two Forms of Capture

Digital ink can be captured relatively or absolutely. A relative-capture device is like a mouse, navigating within a shifting coordinate system erratically related to its earlier path, and not with respect to the invariant writing surface, e.g. a sheet of paper or a flat-panel display. Because of this, capturing ink relatively fails to preserve the relationship of the ink and the writing surface. This makes it impossible to maintain an accurate and consistent relationship between the strokes and their original context, for example the blanks of a fill-in form.

Captured absolutely, digital ink is far more useful, because it maintains a reference to the writing surface. Thus, an accurate relationship between the digital ink and the original writing context is preserved. Using the example above, entries on a filled-in form can be tied directly to the appropriate field via position alone.

NaviScribe

Make a dot on a piece of paper and measure its distance from the paper's edges. You have just done something that no ink capture device on the market today can do: you have used the paper's natural features to determine an absolute position on the sheet. This, in a nutshell, is how NaviScribe works.

Up to now, all absolute ink capture devices have been dependent on external instruments or artificial markings. Instrumentation methods include triangulating rangefinders and rectangular sensor arrays. A different approach uses an "address carpet." This is a dense numerical encoding of coordinates printed throughout a sheet of paper. When a special pen is in contact with the pre-printed paper, it can read its physical position from the code under its tip.

ESPi's NaviScribe technology is different. NaviScribe uses only natural features of the writing surface itself, e.g. the edges of a sheet of paper or a flat-panel display. A NaviScribe system, therefore, may be fully independent of its environment, consisting of nothing more than the NaviScribe-enabled pen or stylus itself.