How to show a hologram in free space?

One of the questions in holoferencing is how to show a hologram in free space. Awareness of a person in our proximity is caused by a stimulus of our senses. The five senses we use are hearing, seeing, feeling, smelling an tasting. For holoferencing it would be fine if we could make hearing and seeing work. But lets focus on seeing in this post.

Seeing an object in free space is basically caused by reflection of light on a surface entering our eyes. So the question could be how we can imitate the reflection of light in a free space? Can we emulate the reflection of light of a specific color in free space, with only air in it. This could be by making something reflect the available light or be a source of light as if it was reflected by a colored surface. We will need to think 'out of  the box' on this challenge.

What if we could manipulate air in a way that would make it reflect light? Or how can we make two or three different sources (of a kind) causing light at the intersection point of those three sources? Or can we fill the room with (harmless) matter that would react on the intersection of some kind of waves with the radiation of light?

If this is possible we can eliminate the need for screens and 3D glasses to have this holograms of other people moving around the room and we ourselves being able to move around the hologram without interrupting its presence.

Is there any research going on with respect to this subject?