Source: http://gizmodo.com/5561095/microsoft-creating-3d-effect-by-shooting-images-straight-into-your-eye
Microsoft's Applied Sciences Group is creating 3D by using a camera to track viewers' eyes and a new special lens. That lens is shaped like a wedge, with 11mm thickness at the top vs 6mm at the bottom. Apparently, the wedge lens can steer light straight into a viewers eye by switching light-emitting diodes along its bottom edge on and off. Basically, by controlling the light, it can display different images on the screen and direct where each image goes.
The limit of their prototype is that currently, only 2 people can watch 3D at one time (one image per eye) or 4 people can watch a 2D video (one image per person). I say no worries Microsoft, it's not like I was going to host a huge 3D kegger given how expensive those damned 3D Glasses cost. [Technology Review]