About XRCE
The idea for using cameras and projectors together to form an interactive desk-top system was first proposed by Pierre Wellner. He began his PhD work by considering the potential benefits of using video in the office environment. This quickly led to the conclusion that the desk-top was the most important focus of office work and that there was great potential for any system that eased the transition between paper and electronic information (Wellner 1993). The idea was tested in a project that used video scanning to translate selected foreign words from paper documents lying face-up on the desk (Newman and Wellner 1992).

Figure a): A projected desk-top user interface:An early prototype of the DigitalDesk and

Figure b) PaperPaint: one of the first applications written for the DigitalDesk.

An early version of the DigitalDesk (Figure 1a) was used for the implementation of a novel freehand drawing package called PaperPaint (Figure 1b). To get PaperPaint to work, some rudimentary thresholding techniques were developed for converting grayscale video images to black-and-white. Software was also developed for converting between the coordinate systems of the camera, the pointing device and the projection display. As an alternative to traditional pointing devices Weller originally envisioned the use of a finger, or two fingers for certain tasks (Wellner 1993). However a tablet and stylus has thus far proved more practical.


The EuroCODE project (1992-95) was an Esprit-funded collaboration between a number of partners including: in Denmark, the University of Aarhus, Jutland Telephone and the Great Belt bridge construction company; in the UK, RXRC and ICL; and a number of more loosely connected partners elsewhere in Europe. The most important of XRCE's EuroCODE deliverables was Ariel, a version of the DigitalDesk tailored to the annotation of engineering drawings. Ariel’s basic function was to display annotations, using a video projector. These annotations could include text, graphics, voice notes and video clips. No video scanning capability was included in Ariel.


Reactions to the DigitalDesk were sufficiently positive to justify developing its constituent technologies. The current prototype of this system is called LightWorks. It has incorporated a series of improvements to image processing which now enable it to produce good fax-quality images of half an A4 sheet (Taylor et al 1996). It also uses a novel barcode scheme for calibrating the relationship between the camera and the desk. The physical arrangement of LightWorks is shown in Figure 2.

Figure 2: LightWorks


Capturing images of paper documents is a common aspect of general office work. However, present-day scanning interfaces are inconvenient for the "casual scanning" of pages and parts of pages, as they usually require the user to move the document from the place of reading.

CamWorks is a system using over-the-desk video capture, designed to facilitate casual scanning while avoiding the expense and complexity incurred by our previous prototypes. The video image is displayed in a window on the PC's monitor along with feedback (e.g. for text selection).

CamWorks was first prototyped in 1995 and since then has been the main platform for our research.

Figure 3(a): Camworks in use

Figure 3(b): the CamWorks window

The current version of CamWorks employs two cameras. The two images are stitched together by software and are presented in a single window. With the application of image processing techniques developed by the CMS group, images produced are of sufficient quality and resolution to apply OCR successfully.

The user can apply one of three image transformations when copying: grayscale (a photograph), black-and-white or text (OCR by TextBridge). In each case the result is copied into the PC's clipboard, from which it can be pasted into another application. Alternatively the result can be printed or written to a file.