Google has been granted a patent for a technology that would enable it to charge advertisers on a "pay per gaze" basis.
The application, filed with the United States Patent and Trademark Office, describes a Google Glass-like eye-tracking technology capable of measuring the "success" of advertising.
The head-mounted equipment would work by recording how long a person looks at an advert, as well as their response to it.
According to the search giant's patent submission, advertising charges would be "dependent upon whether the user looked directly at a given advertisement item, viewed the given advertisement item for one or more specified durations, and/or the inferred emotional state of the user while viewing a particular advertisement."
To work out how often an ad is viewed, the device would incorporate pupil-tracking technologies and, to figure out a user's response to an ad, it would analyse pupil dilation.
The technology's impressive capabilities would not be restricted to digital advertisements, either.
"Pay per gaze advertising need not be limited to online advertisements, but rather can be extended to conventional advertisement media including billboards, magazines, newspapers, and other forms of conventional print media."
Google, which has often been criticised for issues of privacy, especially within the realm of Glass, has made it clear that users can opt out of the tracking system, and that all data collected through it will be made anonymous.
Google applied for the patent back in May 2011.