It is now at least 50 years that scientists have some tools to create a 3D image on an object (holography goes back to the invention of the laser, although the principles goes further back to the electronic microscopy) but so far we haven't found a perfect solution. Even the modern 3D screens are poor substitute of real 3D objects (as an example as you move in front of the screen you are not seeing different parts of an object as you would do when looking at a real one). 3D television screens, as a matter of fact, have not been successful in the market in spite of the marketeers push in the last 4 years.
Now comes the news of an invention from the University of Vienna: a brand new approach to let you see a 3D image were each object is in a 3D space and you can look at it from different angles as you move in different positions with respect to the screen.
The image is no longer displayed on a screen, rather it is painted on your retina, actually two slightly different images are being painted, one for each eye, so that the brain gets a 3D image.
The idea is to have a laser sending modulated light pulses that are directed through a moving micro mirror to exactly meet a point on your retina. The principle is easy to understand although the technicalities are quite complex. The system cannot actually see all the pair of eyes that should be receiving the image (the system is being designed also to provide 3D images to people standing in an open space, like a square or a street). Hence the system is designed assuming that the images will be viewed within a certain distance range (which is actually a sound assumption if you are targeting people looking at the signs in Times square, since the relative distance of two person on the pavement from the image that will appear floating in the middle of the square is not that different).
Because of the way it is designed it becomes possible to display different objects and images to people in different places of the open space. A first result is that depending on which part of a square you are you will see the objects displayed form different point of view (e.g. from the front if you are standing on the left side of the square and from the bottom if you are standing in the right side of the square and any angles in between...). A second result is that you ca display completely different images depending on the direction you are looking from. A customer entering a shop will see some products being sold, one getting out may see complementary products that can be found in a nearby shop!
So far this is just a research result, a proof of concept. It will take quite some time, I feel before we will enjoy it. For the time being we will continue to say that 3D display is still falling short of promises!