You can find a brief research paper on HUDs from the University of Massachussets at Amhert here: Personal Head Up Display, by Ivan Bercovich, RaduAndrei Ivan, Jeffery Little and Felipe VillasBoas.
Reportedly, the new lens from Innovega allows the eye to do what it can´t naturally do, which is focus on an image that´s projected directly onto the lens of eyewear that the user is weating — a difficult task in itself — while also not impairing the ability to focus on objects farther away.
Projections onto eyewear has been in development for some time, but the eye´s natural limits in terms of focus have stymied the development of practical augmented reality, in which information about one´s environment is super’imposed over one´s natural view of the environment itself.
Embedded below is a video featuring Randall Sprague of Innovega explaining the project.
Another approach is being taken by Google with its Google Glasses (video below), but experts have told Wired magazine that Google may have trouble delivering on its promised technology.