London: Google has filed a patent suggesting users pull a series of faces, like sticking out their tongue or wrinkling their nose, in place of a password to unlock their Android phones or tablets.
Google says requiring specific gestures could prevent the existing Face Unlock facility being fooled by photos, reports BBC News.
The document - which was filed in June 2012 but has only just been published - suggests the software could track a "facial landmark" to confirm a user not only looks like the device`s owner but also carries out the right action.
It says examples of the requests that might be made include, a frown, a tongue protrusion, an open-mouth smile, a forehead wrinkle, an eyebrow movement.
It says the check would work by comparing two images taken from a captured video stream of the user`s face to see if the difference between them showed the gesture had been made.
The filing also notes several ways the software might check that the device was being shown a real person`s face rather than doctored photographs.
These include studying other frames from the captured video stream to check that the person had made a sequence of movements to achieve the commanded gesture, and confirming all of the frames actually showed the person`s face.
In addition it says the software could monitor if there were changes in the angle of the person`s face to ensure the device was not being shown a still image with a fake gesture animated on top.
Such efforts might help address criticism that its current face detection software is insecure.