A recently discovered patent submitted by Apple details a method of unlocking an iDevice via face-recognition a'la Galaxy Nexus...kind of risky based on the privacy concerns surrounding using a photo to unlock the phone.

As described in the above image discovered by PatentlyApple.com, the device would sense a user approaching and wake from sleep to activate its image processor.  At this point, facial recognition software can be executed to match the user's face and unlock the device.  Business users can set even higher levels of security.

The problems with face-recognition technology fall into two camps: you could either make a system that uses an inexorably large amount of computational effort to work making for a big drain on battery life, or the system's camera could take an image of resolution that's low enough to be tricked by a photo on a mobile phone display.

What Apple look to be doing to avoid these holes is a complex set of processes.  Firstly, the face is photographed and places called "high information portion" areas such as the nose, eyes and mouth are matched with a reference image.  These two images will then be normalised and given a score (called a weight in the patent) to determine how close of a match they are.  Higher weights will be given to the "high information portion" areas, and the less significant parts will be given lower weights in determining matches.

This would make for a much more precise face analysis, and since it's all processed at that initial stage it means for less of a drain on battery when out and about.

But what about the photo-unlock controversy that's been surrounding the Galaxy Nexus?  This is dodged by a pretty nifty system called orange-distance filtering, which will detect the skin colour and tone.  If the key portions of the image have a different skin tone, then the system will recognise that it's looking at a photo, not the real thing.

This may not have solved the problems surrounding a 'Face-off' style situation; but it's definitely going in a good direction, if this technology makes it into Apple devices.

Source: Patently Apple