Apple has applied for a patent of a device that combines a high-resolution digital display with portable head gear. Apple may be eyeing its own "portable heads-up display" that could give Google Glass devices some competition.

According to a filing published by the U.S. Patent and Trade Office yesterday, Apple's patent application refers to a technology that increases the resolution on a display without increasing the number of pixels or "a method of increasing resolution through mechanical actuation." Such technology could be used in a portable heads-up display, Apple explained, where limiting the number of pixels is especially useful.

"In particular, a portable heads-up display may be size and weight constrained such that addition of physical pixels may not be practical," Apple wrote in the filing. "Conventionally, fewer physical pixels may mean lower cost to manufacture, lower weight, smaller size, but also lower resolution."

Apple had earlier applied for another patent dubbed "Peripheral treatment for head-mounted displays." In this one, Apple specifically refers to the invention of a "head-mounted display apparatus" which would project an image viewable by the user.