Aus Hackerspace Ffm
A DIY hologram project based on AIRR ("Aerial Imaging by Retro‐Reflection") developed by Prof. Yamamoto. Using two optical component, if you count the observers eyes too it's one more :D This optical system refocuses the light-path in mid air, hence you get the impression of a floating image in mid air.
The half mirror is self made. The glas is cut from a photo picture frame, and a sun shield / privacy foil was applied.
The following animation shows, from the side, the light-path for the upper half of the half mirror. The blue lines are the retroreflectors, the green line is the half mirror.