TweakTown has a bit more information about how it works:
Anshel Sag of Moor Insights & Strategy provided us with the above images, explaining: "This headset is an NVIDIA headset developed as a research project in conjunction with Stanford University project called the "Lightfield Stereoscope" which allows you to essentially view light field images in the headset and focus on virtually any point in the headset with your own eyes. This headset is clearly important enough to NVIDIA to show off at an event like VRLA and could be used for viewing things like Lytro's Lightfield photos that Lytro created with their light field cameras. This headset can also be used in VR to allow the entire scene to be rendered once and to let your eyes decide where to focus making the VR experience more realistic".
A user goes eyes-on with our Light Field Display prototype at @vrlosangeles. #VRLA pic.twitter.com/fbt4LWbw37
— NVIDIA GeForce (@NVIDIAGeForce) 24 januari 2016