3D displays which use glasses have not gained wide acceptance. Autostereo displays provide 3D perception without the need for special glasses or other head gear. Three basic technologies exist to make autostereo displays: spatial multiplex, multiprojector and time-sequential. These can be used to make two types of useful device: two-view, headtracked displays; and multi-view displays. The former tend to be single-viewer systems while the latter can support multiple viewers. The latter tend to require more processing power because they have more views than the former. Both types will find uses in their own niches. An autostereoscopic display provides the viewer with a three-dimensional image without the need for special glasses.
3D displays which require the viewer to wear special glasses are reasonably well known. These displays present two different images in the same plane. The glasses select which of the two images is visible to each of the viewer’s eyes. Technologies for this include standard colour display combined with coloured glasses (anaglyph method); two standard displays made coplanar by an half-silvered mirror, combined with polarised glasses; and a double frame rate display combined with shuttered glasses. Such displays have not gained wide acceptance, partly owing to the need to wear glasses. Autostereo displays provide 3D perception without glasses and should, therefore, prove more commercially viable. Multi-view and head-tracked autostereoscopic displays offer the viewer three dimensional realism lacking in conventional two-dimensional or stereoscopic displays. They combine the effects of both stereo parallax and movement parallax producing a perceived effect similar to that of a white light hologram. The observer sees a different image of the scene with each eye and different images again whenever he moves his head. He is able to view a potentially infinite number of different images of the scene. Thus both stereo and horizontal movement parallax cues can be provided with a small number of views. The finite number of views required in allows the replacement of the scene by a three dimensional display that outputs a different image to each window.