By Mark Ward
Technology correspondent, BBC News website, San Diego
Shadows are being used by Japanese researchers as an non-intrusive way for friends to stay in touch.
The lamp projects the outline shadow of friends
Called Teleshadow the system pipes video of what people are doing at home via the net to their friends' houses.
But instead of showing images in full motion and colour, Teleshadow turns them into shadow outlines projected on the inside of a small decorative lamp.
Creator Shunpei Yasuda said the shadow presence system aims to fill the gap between live video and static images.
Mr Yasuda, a post-graduate student in Media Design at Japan's Keio University, said the inspiration for the system came from Japanese history.
For many years, he said, Japanese homes have had Shoji or paper walls that divide some rooms. The thin walls preserve some privacy but the shadows cast on the paper as people move about also act as a reminder of that person's presence.
In a similar way Teleshadow preserves privacy while reinforcing presence between rooms that are far apart rather than next door.
Also, said Mr Yasuda, the lamp, or andon, that act as the projector is based on a well-known Japanese design.
"As this is a new media that fits our daily life, it was important to make it as a piece of furniture," said Mr Yasuda.
In the base of the lamp is a projector that takes input from the video camera that users of the Teleshadow system have in their homes. Software processing reduces the video input to an outline so it appears as a shadow when projected on the inside walls of the andon lamp.
The square lamp can show the shadow antics of up to four friends. The lamp knows which shadows to show as the Teleshadow project uses smart cards to identify users that those taking part swap with each other.
Slotting the smart card in the base of the lamp starts it displaying that person's shadow.
The prototypes built by Mr Yasuda and his fellow researchers used touch screens for the faces of the andon lamp making it possible to set up a voice call to that person by touching their shadow.
Unlike a live video stream, the Teleshadow system preserves privacy by hiding details of what someone is doing, said Mr Yasuda.
Sometimes, said Mr Yasuda, video gives away information that people would rather was kept private. Teleshadow, he said, helped to bridge the gap between total information of video and old information in a single photograph.
The research was shown off at the Siggraph computer graphics convention being held in San Diego, US from 5-9 August.