3D hologram display

They are almost never true holograms in the physical sense. In the trade, the name covers several techniques that create the spatial impression in different ways.

Three designs are common. In an LED fan, a blade fitted with light-emitting diodes spins so fast that the eye sees a still image. With a reflection on angled glass or film, an image from a hidden screen appears as a figure in the room. There are also screens that use lenses or several image layers to create real depth without glasses. Such devices are used in shop windows, at trade fairs and in exhibitions, where they are meant to catch the eye.

The effect only works with suitable content: the subject needs a black background, because black remains invisible with these techniques. The impression depends heavily on the viewing angle and the ambient light. Rotating devices must hang out of people's reach or sit behind a protective cover. Operators should try the device at the planned location before commissioning content.