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.
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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.