Swipe to unlock could be a thing of the past for next-gen iOS devices. Like current Galaxy Nexus users, iOS users could soon be using facial recognition technology to lock or unlock their iDevices.

As described in a recently discovered patent, Apple's method would sense when a user is approaching the device – for example, if it's seated in a dock, and the user walks toward it. The device would then use its image processor to execute facial recognition to unlock the device, all with low battery penalties. If the device is used for business applications, higher security levels could even be set.

Apple's method would use a "weighted difference" map instead of a computationally "expensive" method called correlation mapping, according to Patently Apple, which first reported on the patent.

Here's a few ways it could work:

The device's front-facing camera would capture an image of the user. Rather than analyzing the entire face, the face-detection system would look at just "high information portion" areas like the eyes, nose, and mouth. These areas would be matched with a reference image.

The two images could also be normalized, a process that adjusts the pixel values in a photo. The two normalized images could be subtracted, and a score (called a weight) would be assigned to how closely they match. The high information areas (like the eyes) would be assigned a heavy weight, for example, and a lower weight would be given to less relevant, identifiable parts of the face.

And because you'd be holding your iDevice at a certain distance from your face, the system could also assume the "approximate location and orientation of face features" in order to avoid computational overhead. This is shorthand for, "Your processor won't have to work as hard, and you'll save battery life as a result."

Apple would not be the first to implement facial recognition in its mobile devices. Google already has it in place in its Ice Cream Sandwich Android OS, which has a face-recognition unlock feature. Unfortunately, some pseudo-hackers found that face unlock can be fooled by holding up a picture of the phone's owner.

Apple's also no stranger to facial recognition technology. It reportedly purchased the company Polar Rose, which developed an augmented reality app that could identify a person based on a photo, in September 2010. What's more, a patent application filed in 2010 describes ways to identify a device's rightful owner based on his or her visage or heartbeat. This one had many critics crying foul.

This most recent Apple patent application describes technology that would work even if an iPhone, iPad or MacBook were switched off. When it senses someone approaching, it would transition to a different state to acknowledge and then identify the potential owner's presence. The facial recognition system could also be used to recognize a group of people, useful if a device is used by a team in the workplace.

What about the gaming Apple's technology, the same way Ice Cream Sandwich face unlock can be gamed? Well, Apple's patent would use a technique called orange-distance filtering to determine "attentiveness." If the orange skin tone portions of the image aren't detected a certain way, the system would know it's looking at a photo and not a real person. Unfortunately, I'm not sure if this means it would work against someone wearing a "Mission Impossible"-style full face mask.

This patent application was filed in Q2 of 2010.