The third dimension. Has a certain ring to it, doesn't it? Creating images and viewing them in 3D is still a challenge, but this hasn't stopped video enthusiasts from punching out some corners of the envelope.

Most of us who can hear and see well, take binaural (stereo) sound and binocular vision for granted. Sophisticated devices to replicate the former experience have been around for 40 years or more and today we can enjoy the delights of Compact Discs in the home at little cost and even less fuss.

Just sit back, fire up the hifi and listen; no need to sit in the 'sweet spot' of the room (unless you're a fanatic) and no pressing need for headphones.

But binocular vision, viewing images in stereo, enjoying the third dimension - that's a tougher call. And this is the odd thing: image capture by means of the photographic process has been around for 176 years now, while sound recording has been with us only 125 years since Edison began to market his phonograph.

Furthermore, it was only about 25 years after Niepce took the world's first photographic image that stereo cameras became practical devices and people of the Victorian era could sit back and enjoy images of their world in simulated depth, thanks to the Wheatstone hand-held viewer.