You could soon watch
3D videos on your smartphone without any special eyewear, thanks to scientists who have developed a way to make displays for small screen devices that offer both 2D and 3D imaging.
For eyewear-free displays, the only action is behind the screen where the image's pixels and optics are layered together to produce the stereoscopic effect.
The two primary ways of producing these optically illusive effects are by using either an array of micro-lenses, called lenticular lenses, or an array of micro-filters, called parallax barriers, in front of the image to make its appearance depend on the angle at which it is being seen.
The simplest example of this effect is found on a movie poster whose image appears to change as you walk by.
Two or more images are interlaced and printed behind a plastic layer with grooves matching the interlaced pattern.
The grooves act as distinct, interlaced arrays of lenses or filters, unveiling one image as you approach the poster and another as you depart.
In the case of 2D/3D convertible screens, these layers are active, meaning they can be switched on or off.
