The popularity of 3-D cinema is skyrocketing and 3-D-capable TV sets are heading for our living rooms, but almost every 3-D ready technology still requires that you don a set of special glasses. Microsoft has developed lens which could help change all that. With the ability to keep track of the position of viewers and send separate images directly to each eye, the new prototype display eliminates the need for 3-D glasses.

Many tech companies are surfing the 3-D trend and researching better ways to deliver stereoscopic imagery without the need for users to wear glasses. Sharp, for instance, has been researching the field since 2002 and Nintendo (with the new 3DS) and Fujifilm (with its Fujifilm FinePix Real 3D W1 display) have entered the realm of glasses-free 3D.

However innovative, one limitation of Sharp's (and other companies') approach is that the user needs to stand in a precise spot with respect to the screen in order to experience stereoscopic vision. Microsoft's Applied Research Group, however, goes a step further: the system uses a camera to track each viewer's movements and then sends the light in the appropriate direction, directly to their eyes, even allowing two separate users to experience 3-D vision simultaneously.

The key to Microsoft's experimental system is a peculiar lens that projects the light toward a viewer by switching on and off light-emitting diodes placed along its bottom edge. Thanks to an optical trick, light enters through the bottom edge of the lens and then refracts within the lens itself to reach the desired angle, after which it's finally sent to the viewer. This method also means that unlike traditional projectors, the structure — including the lens itself — is thin and could be embedded into a standard LCD display without too much hassle.

The number of viewers that the system can track simultaneously is limited by the screen's refresh rate: so, while a standard 240Hz LCD can keep track of two users (four 60Hz channels, one for each eye) a faster refresh rate would allow for even more users to share the same 3-D experience at the same time. Another limitation is the small viewing angle — currently at just 20 degrees, although the researchers hope to increase this figure to 40 degrees by tweaking the design of the lens.

Microsoft is also looking at other possible uses for the 3-D lens. Once integrated into a laptop, one application could be to allow only one user at a time to view the monitor, blocking off prying eyes and ensuring privacy in public places. The user would then be able to switch back to a standard "public view mode" in which light is scattered in all directions in order to share the display with more people.