Department of Computer Science and Technology

Technical reports

Interacting with paper on the DigitalDesk

Pierre David Wellner

March 1994, 96 pages

This technical report is based on a dissertation submitted October 1993 by the author for the degree of Doctor of Philosophy to the University of Cambridge, Clare Hall.

DOI: 10.48456/tr-330


In the 1970’s Xerox PARC developed the “desktop metaphor,” which made computers easy to use by making them look and act like ordinary desks and paper. This led visionaries to predict the “paperless office” would dominate within a few years, but the trouble with this prediction is that people like paper too much. It is portable, tactile, universally accepted, and easier to read than a screen. Today, we continue to use paper, and computers produce more of it than they replace.

Instead of trying to use computers to replace paper, the DigitalDesk takes the opposite approach. It keeps the paper, but uses computers to make it more powerful. It provides a Computer Augmented Environment for paper.

The DigitalDesk is built around an ordinary physical desk and can be used as such, but it has extra capabilities. A video camera is mounted above the desk, pointing down at the work surface. This camera’s output is fed through a system that can detect where the user is pointing, and it can read documents that are placed on the desk. A computer-driven electronic projector is also mounted above the desk, allowing the system to project electronic objects onto the work surface and onto real paper documents — something that can’t be done with flat display panels or rear-projection. The system is called DigitalDesk because it allows pointing with the fingers.

Several applications have been prototyped on the DigitalDesk. The first was a calculator where a sheet of paper such as an annual report can be placed on the desk allowing the user to point at numbers with a finger or pen. The camera reads the numbers off the paper, recognizes them, and enters them into the display for further calculations. Another is a translation system which allows users to point at unfamiliar French words to get their English definitions projected down next to the paper. A third is a paper-based paint program (PaperPaint) that allows users to sketch on paper using traditional tools, but also be able to select and paste these sketches with the camera and projector to create merged paper and electronic documents. A fourth application is the DoubleDigitalDesk, which allows remote colleagues to “share” their desks, look at each other’s paper documents and sketch on them remotely.

This dissertation introduces the concept of Computer Augmented Environments, describes the DigitalDesk and applications for it, and discusses some of the key implementation issues that need to be addressed to make this system work. It describes a toolkit for building DigitalDesk applications, and it concludes with some more ideas for future work.

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BibTeX record

  author =	 {Wellner, Pierre David},
  title = 	 {{Interacting with paper on the DigitalDesk}},
  year = 	 1994,
  month = 	 mar,
  url = 	 {},
  institution =  {University of Cambridge, Computer Laboratory},
  doi = 	 {10.48456/tr-330},
  number = 	 {UCAM-CL-TR-330}