Is there such a thing as too big a cellphone display?  Obviously yes, otherwise it might be too massive for your pocket; thing is, users are getting all too accustomed to the luxury of browsing the full internet on their iPhone, and soon you know they're going to be clamouring for more.  Perhaps that's why Apple has developed a new type of head-mounted display: maybe as an upcoming iPhone with augmented reality, maybe a new display peripheral for a MacBook.  Or maybe, as is most likely I think, just because it's a cool thing to develop.

The patent describes a system of two miniature display sources (LCD or OLED), one for each eye, which allow for a broader field of view.  Being separate, they would also allow for individual adjustment for a user's face.  Apple also suggests a slight offset could be introduced for creating stereoscope-like 3D.

"[T]he invention provides methods and apparatus for providing a wider field of view and creating a more natural viewing situation for a user of a head mounted display, which results in improved comfort and usability for head mounted displays" Apple patent

Developed by John Tang, of Apple's Industrial Design Group, although the patent describes some vague usage scenarios it's primarily dealing with the technical aspect of creating large view-through near-to-eye displays.  It's also possible that Apple have a heads-up video display in mind.  A 16:9 widescreen aspect ratio is mentioned, as is movie data played from a portable device.