CAMBRIDGE, MA -- Scientists at the Massachusetts Institute of Technology's famed Media Lab have developed a prototype video projection system for three-dimensional images that can be viewed without glasses.
The developers, working in the Media Lab's Camera Culture group, have been at work for three years on the "multiperspective" video display. The new projector is an outgrowth of this that they believe can provide a more economical and practical alternative to holography as the solution to the shortcomings of conventional stereoscopic projection.
The system consists of a rear-projection screen with two lenticular panels, of different focal lengths, spaced so that each pair of tiny lenses embossed on the panel widens the viewing angle by acting as a little backward telescope.
The projector behind it is fitted with two liquid-crystal modulators mounted between the light source and the lens. The first modulator displays patterns of light and dark that cause it to act as a bank of slightly angled light emitters; light passing through it reaches the second modulator only at certain angles. Those patterns are controlled by software written by the researchers to take full advantage of today's graphics processing units designed to handle the high refresh rate demanded by high-speed, high-resolution videogames.
In conjunction with the screen, the modulators not only deliver a slightly different view to the observer's left and right eyes, but enhance the illusion of depth by disclosing new perspectives as the observer changes position (thus "multiperspective"). Eight different angles are presented for each frame of video projected. As a bonus, the system is said to improve the black level and enhance the resolution of the image.
Both the screen and the elements in the light path are passive, without moving parts, and the demonstration projection system was assembled from off-the-shelf components. The developers wrote the software that produces the patterns displayed on the modulators by conceiving and applying a technique for calculating how much information can be preserved between viewing angles, to minimize the amount rewritten for each frame.
The system will be on display during this year's SIGgraph conference in Vancouver. This is the 41st annual International Conference on Computer Graphics and Interactive Techniques organized by the Association for Computing Machinery. Exhibits at the conference are open now (Aug. 12-14).