Apple has been granted a patent (number 10,203,489) for an “optical system for a head-mounted display.” One of several such patents, it doubtless involves the company’s “Apple Glasses” headset that’s expected to debut next year.
In the patent details, Apple notes that head-mounted displays such as virtual reality glasses use lenses to display images for a user. A microdisplay may create images for each of a user's eyes. A lens may be placed between each of the user's eyes and a portion of the microdisplay so that the user may view virtual reality content.
However, Apple says that if care isn’t taken, a head-mounted display may be cumbersome and tiring to wear. Optical systems for head-mounted displays may use arrangements of lenses that are bulky and heavy. Extended use of a head-mounted display with this type of optical system may be uncomfortable. Apple doesn’t want its “Apple Glasses”
Here’s Apple’s summary of the invention: “A head-mounted display may include a display system and an optical system in a housing. The display system may have a pixel array that produces light associated with images. The display system may also have a linear polarizer through which light from the pixel array passes and a quarter wave plate through which the light passes after passing through the quarter wave plate.
“The optical system may be a catadioptric optical system having one or more lens elements. The lens elements may include a plano-convex lens and a plano-concave lens. A partially reflective mirror may be formed on a convex surface of the plano-convex lens. A reflective polarizer may be formed on the planar surface of the plano-convex lens or the concave surface of the plano-concave lens. An additional quarter wave plate may be located between the reflective polarizer and the partially reflective mirror.”
Of course, Apple files for — and is granted — lots of patents by the U.S. Patent & Trademark Office. Many are for inventions that never see the light of day. However, you never can tell which ones will materialize in a real product.