High Quality Content by WIKIPEDIA articles! The Heliodisplay is a free-space display developed by IO2 Technology. A projector is focused onto layers of air and micro-spheres in mid-air, resulting in a two-dimensional display that appears to float. This is similar in principle to the cinematic technique of rear projection and can appear three-dimensional when using appropriate content. As dark areas of the image may appear invisible, the image may be more realistic than on a projection screen, although it is still not volumetric. Looking directly at the display, one would also be looking into the projector`s light source. The necessity of an oblique viewing angle (to avoid looking into the projector`s light source) may be a disadvantage.