This is an astonishing technology demonstration: A camera tracking a bouncing ball in real time, keeping it in the centre of the video image

Tracking moving objects automatically has up until now involved moving the camera. That's obvious, really.

But it wasn't obvious at all to a team of Japenese engineers who have done it a different way, with unbelievably good results. They're system can accurately track a bouncing ball, for example, keeping it in the centre of the picture.

They do it by moving a pair of mirrors, one for vertical movement and the other for horizontal tracking. Beause the mirrors have a much smaller intertia than an entire camera, they can not only track objects incredibly fast, but are able to use virtually any camera - including very high-quality ones, to ensure a good picture.

Projection

And the technique is reversable too.

By putting a projector in place of the camera, they can display moving images on moving objects. We're struggling to think of practical applications for this but it doesn't stop it being a remarkable technology demontstration.

Of course, there's more to it than a pair of mirrors. There's some pretty clever software and image analysis going on here too.

Thanks to our VFX correspondent HaZ for spotting this.