This is nice. But at the same time, I wonder why we still cannot make light-field displays, i.e., displays where not only the emission of light is controlled, but also the direction. This seems like a more generic approach to the problem.
Raskar's group at MIT (and others) have made light field displays. They're expensive. Abstract:
> For about a century, researchers and experimentalists have strived to bring glasses-free 3D experiences to the big screen. Much progress has been made and light field projection systems are now commercially available. Unfortunately, available display systems usually employ dozens of devices making such setups costly, energy inefficient, and bulky. We present a compressive approach to light field synthesis with projection devices. For this purpose, we propose a novel, passive screen design that is inspired by angle-expanding Keplerian telescopes. Combined with high-speed light field projection and nonnegative light field factorization, we demonstrate that compressive light field projection is possible with a single device. We build a prototype light field projector and angle-expanding screen from scratch, evaluate the system in simulation, present a variety of results, and demonstrate that the projector can alternatively achieve super-resolved and high dynamic range 2D image display when used with a conventional screen.
The second technique that they present here is the generation of true holograms (we have to use "true" nowadays, with all the products falsely marketed as holograms on the market). This technique is equivalent, or arguably superior to controlling the direction of emitted light as in a light field display. It seems they do this by projecting the interference pattern on a flat surface.
The wavefront generated by a true hologram contains not only arbitrary directional information, but also complete "positional" data, ie. changing with distance from the screen. The main thing that's prevented us from making true holographic screens is the massive resolution that they require (relative to displayed wavelengths), and it seems that the resolution they've achieved here is enough to create simple low-resolution holograms, though I don't see anything preventing the exact same technology from creating larger, more detailed holograms.
