Dr Adrian Dorrington, a scientist from the University of Waikato, explains the basic concept behind 3D television and film. One system requires the viewer to wear active glasses so that the right image is delivered to the right eye at the right time. Active glasses require a power source to operate the shutter system in the lenses.
DR ADRIAN DORRINGTON
The basic concept behind 3D television and film is delivering the two different images to the two different eyes. There’s a bunch of ways that this can be done, either with a passive system where you wear glasses and there are filters on the glasses, or with an autostereoscopic system where the display delivers two different images to a fairly narrow field of view, so you need to sit in the right place. But the most common – for example, if you go and buy a television these days – is an active system where the glasses you wear have shutters in them, and they ensure that the right image is delivered to the right eye at the right time.
Polarisation is the way in which the light is oscillating. Light’s an electromagnetic wave. It oscillates back and forth at a very high frequency, so if you arrange it so that it’s oscillating in one particular plane, then that’s a particular polarisation. If it’s oscillating at another plane, then that’s a different polarisation.
If you’re looking at a projected image, for example, like on a movie screen, the projector will use a white light bulb, but there might be two projectors sitting side by side, and they’ll have a standard bulb and then a polariser, so that selects only a particular polarisation coming from that light source, and then the other projector will have the same light source but the polariser will be rotated the other way so it selects only some of that light.
Passive glasses are just glasses with some type of filter. There might a colour filter, there might be a polarisation filter, but there’s no electronics or there’s no power required to use those glasses.
But active glasses require a power source, and they’re slightly bigger glasses and you need to recharge them. That’s the type of glasses that you’ll see with a modern 3D TV set, and they work instead of separating the images by colour or polarisation, they do it in time.
They actually have shutters in the lenses, which means that, at any given time, the shutter in one eye will be open while the other eye will be closed.
So the picture that is presented on the television is actually flashing back and forth between the image for the left eye and the image for the right eye, and the glasses open up the left eye when the left image is on the TV, and they’ll close, the TV will change to the right eye, and then that will open up.