The prototype digital glasses, unveiled on the company's Google+ social network on Wednesday, are still being tweaked and tested, and are not available in stores yet.

"We're sharing this information now because we want to start a conversation and learn from your valuable input," Google wrote in a post on a Google+ page devoted to Project Glass.

The spectacles are being developed by Google, the secretive group working on advanced research projects such as self-driving cars.

The Google+ page featured a 2-1/2 minute video, shot from the perspective of someone wearing the glasses. The wearer goes about his day walking through New York City while speaking commands to the glasses to do things such as take a photo and post it to Google+, get block-by-block directions and weather conditions and get a pop-up alert when a friend is nearby.

The Google posting is intended to show "what this technology could look like," the company said. Mock-up images of the glasses on the Google+ page depict a stamp-sized digital display that seems attached to a pair of glasses and sits at the top corner of one of the lenses.

The post asks people to submit their suggestions for what they would like to see in the glasses.

Google, the world's No. 1 search engine, is famous for letting its employees work on ambitious projects that don't always have a direct relation to its business.

Those projects have not always sat well with investors, who worry about Google's spending on projects with uncertain returns.

Google Chief Executive Larry Page has cut down on many of the projects and products underway at the company since taking the reins a year ago. But he has defended Google's commitment to working on "speculative" projects that could one day turn into "billion-dollar businesses," though he has stressed the company isn't "betting the farm" on such efforts.

The glasses could provide a way for Google to more closely entwine its advertising-supported online services, including Web searches, maps and email, into people's daily lives.

The glasses also could help Google match some of the buzz that rival Apple Inc has generated with its latest iPhone and the built-in Siri digital assistant, which takes spoken commands to do such tasks as schedule calendar appointments and get weather forecasts.

A Google insider said it is unclear when the glasses might be commercially available, but noted that the philosophy of Google group is to develop technologies that can be used in a relatively short period of time, rather than dreaming up creations that won't be possible for 10 or more years.

The glasses, under development for two years, will be tested in public by members of the Google team, according to the Google insider.

Shares of Google, which reports its first quarter financial results next week, fell about 1.2 per cent to close at $635.15 on Wednesday amid a broad market sell-off.