Twitter user @aomesan147, a representative of the creators of Polid Screen technology, has been posting photos and videos of small holographic projections of Hatsune Miku on their screens.
Their official website gives instructions (in Japanese) on how to build your own basic Polid Screen, but the two-sided projections are a relatively new setup.
The projections are two-sided: they can be viewed from the front and back, as though you’re viewing Miku from two different angles.