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Last Updated: Tuesday, 19 February 2008, 15:48 GMT
Iris scans to protect your photos
Iris scanner being trialled by the former UK Home Secretary Charles Clarke
Iris recognition relies on the fact that no two eyes are identical
The increasing problem of digital photograph theft is being tackled by one Japanese camera company using iris recognition - the same technology used at airports to combat terrorism.

A patent for technology which will digitally "watermark" the image with the details of the iris of the photographer has been filed by camera giant Canon.

The system works by scanning the iris as the eye is put to the viewfinder when the shot is composed.

"It's really a combination of two pre-existing technologies," John Daugman, the original inventor of Iris Recognition, told BBC World Service's Digital Planet programme.

"Often in invention, the innovation is a combination of two older arts. So from what I've seen of the Canon patent, it doesn't actually propose any new method of iris recognition - it just says, rather vaguely, that the iris information of the photographer is embedded, whether it's a raw image or an encoded image."

Practical issues

Digital photographers keen to show off their skills have flocked to photo-sharing websites such as Flickr and Photobucket in recent years.

Although the sites make provision for the owner to set the copyright status associated with their images, there have still been cases where photos have been stolen - in some cases allowing the thief to sell the images to sites which pay to be able to use them commercially.

There's advantage in encoding just the mathematical description of the iris - a very short iris code - rather than the iris itself
John Daugman
This has led to camera companies looking at ways to encode the photographer's copyright into the image.

John Daugman said that the patent as filed does not specify whether the iris scan will be put into the photograph as a piece of code or as an image of the eye.

"There's a lot of practical issues there, because a raw image is several hundred thousand bytes normally - or even several million bytes - but the iris code itself is only 500 bytes," he said.

"So there's advantage in encoding just the mathematical description of the iris - a very short iris code - rather than the iris itself."

This is because they are intended to be unobtrusive and surreptitious.

Mr Daugman pointed out that using iris technology may not necessarily be "an unalloyed blessing," because cameras are not ususally built to capture infra-red images - which is how iris recognition works.

As a result, building it in would add significant cost.

"You've got to add another set of optics that's rather different to the set at the front of the camera, to acquire this image facing the other way, as it were," Mr Daugman said.

These problems were "not necessarily trivial," he said.

"But still, it's a promising idea," he added.

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