Technologies for Interactive Paper

Digital Pen

There are numerous research projects and commercial products related to interactive paper and while they tend to vary widely in terms of their goals and technologies, most are based on some means of detecting user actions on paper documents and linking them to actions in the digital world. If paper documents are to be interactive independent of their physical position or attachment to a special device, then the mechanism for detecting user actions on paper must rely on some sort of encoding of information on the paper itself. One approach is to print some sort of link identifier on the paper. For example, barcodes or special icons could be used to encode unique identifiers that are mapped to digital media files or web pages to be displayed. Another approach is to encode position information across pages which can be used to track pen position. The advantage of this approach is that is can be used to capture writing as well as for interaction. Further, since links are based on relative position within a document rather than simple identifiers, it is possible to find all the elements within a document that link to a specific target.

Anoto paper

One of our Industry project partners Anoto developed a technology to track the movement of a pen on paper to enable the capture of handwriting. A special digital pen has a camera situated alongside the writing stylus to capture images of an almost invisible pattern of infra-red absorbing dots printed on paper, as indicated in the figure.The pattern of dots encodes (x,y) positions in a vast virtual document space. Camera images are recorded and processed in real-time giving up to 100 (x,y) positions per second. Several pages of handwriting can be captured and stored within the pen before being transmitted to a PC. While data transmission on demand is sufficient for writing capture, immediate transfer of position data is required if the digital pen is to be used as an interaction device. Using special prototype pens from Anoto, we are able to switch the pen to streaming mode and use it for both real-time interaction and writing capture.

Other project partners are investigating alternative technologies to yield a low-cost solution for interaction only. Within the previous European project Paper++, a grid of almost invisible barcodes printed in conductive ink was used to encode position information on paper and a prototype reader was developed to read position information by measuring the inductivity during a swiping action. Other solutions are being investigated in the European project PaperWorks which started in 2005.