Correction, reading further I see that the linked paper describes using a gyroscopic sensor to dynamically vary the viewpoint as the user rotates the device, but it remains true that the conic apparatus can display an image to be viewed comfortably from any angle.
Based on these considerations I propose an additional enhancement. Using the well understood technology of privacy filters for laptops, it could be possible to effectively occlude views based on orientation, allowing for the display of several views of a scene simultaneously, with the one visible depending on the user's orientation with the device.
> using a gyroscopic sensor to dynamically vary the viewpoint as the user rotates the device
Yes, this is what occurred to me when watching the video. It must know if it being rotated. For the tiger to be seen on the side of the cone you are viewing, it needs to be rendered on the display somewhere between the "nickel" and the viewer.
Someone viewing from the opposite side of the cone would not see the reflection that you are seeing — no tiger on their side of the cone. (Now, in that specific case, two viewers 180 degrees apart, you could in fact render two tigers on opposite sides of the code so both viewers see a tiger.)
No true stereo at all though with the cone. Left and right eye will see the same tiger. Only a sort of "perceived" stereo if you rotate the device.
I recall there was one gimmick where a camera processes the position of the pupils of an observer and changes a display based on the position of the pupils relative to the display.
It is not strictly stereoscopic, but there's an uncanny 3D effect where foreground and background move relative to each other when the observer shifts position. Sort of like paper-cutouts.
Based on these considerations I propose an additional enhancement. Using the well understood technology of privacy filters for laptops, it could be possible to effectively occlude views based on orientation, allowing for the display of several views of a scene simultaneously, with the one visible depending on the user's orientation with the device.