The images you see above were created by a Japanese Institute which utilizes dot-array placement in empty space. In order to make this possible, however, a very high quality laser is necessary which is why this product is not mainstream.
The technicalities on how this works is beyond what many people would understand, and because of a lack of being able to paraphrase the process here is the essentials on how it works:
The emission time of the laser pulse light is approximately a nanosecond (10-9 sec). The device uses one pulse for each dot. The human eye will recognize the after-image effect of plasma emission from displays up to 100 dot/sec. By synchronizing these pulses and controlling them with software, the device can draw any 3D objects in air.
News Source: PhysOrg.com
I think they’re saying it works like persistence of vision (an illusion of a projection, because it’s moving and refreshing so fast it looks like a constant image).
Good call, that is definitely a good way to put it. Thanks for the clarification.
-Ryan