Google glass is dream project of Google and regarded as one of the first future tech one can use today, which was once only seen in sci-fi movies.
Practically, it’s a wearable head mounted display glasses which acts & display information like a smart phone but in a hands-free format and users’ eye as screen and can interact with the web via human voice.
Like a computer Google glass consist of – tiny CPU, Camera, a prism, microphone, speaker and a battery. The magic lies in prism which project a layer ahead of user over reality light by focusing the image directly over retina of user’s eye, this is called Virtual Retina Display (VRD) that draws a raster display (like a television) directly onto the retina of the eye.
The below interesting infographic via – Brille-Kaufen.org show the detail working of Google glass: