Sergey Brin, Google's co-founder, in a Twitter picture posted Jan 20, 2013. @Noazark/Twitter

We told you you might start hearing or seeing a bit more of Google's Project Glass in the next month.

A fan of the glasses said he spotted Google co-founder Sergey Brin riding the New York City subway this weekend wearing the futuristic glasses, which are promised to overlay digital information on the physical world.

Brin, who runs "Google X" projects, was wearing - or presumably testing - the glasses, which are billed as searching the Internet and showing you anything you need, right in front of your eyes, from maps of where you are to the weather forecast if you look up. You can connect the glasses to a phone via Bluetooth and use the phone's 3G or 4G connection. There's also a camera on the front that can take photos of whatever you are seeing; you can share the photos instantly.

Noah Zerkin, a self-proclaimed "wearable computing and augmented reality enthusiast," said he was the first to spot Brin.

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"Yeeeah… I just had a brief conversation with the most powerful man in the world. On the downtown 3 train. Nice guy," Zerkin tweeted with a photo of Brin in the glasses.

Brin last publicly showed off the glasses in June at Google's I/O conference. He presided at the Moscone Center in San Francisco as sky divers, who were also wearing the glasses, jumped out of a plane above and streamed live video from their glasses right to a screen on stage at the conference.

At the end of the month Google will hold an event for software developers. The developers' version of the glasses, which cost $1,500, are expected to be available to software makers later this year.