Regardless of market potential, there are several optical engineering challenges that need to be overcome before displays in eyeglasses become pervasive. From an optical engineering point of view, the design space is large enough and designers have to make choices. A good example of such a choice is choosing just the right field of view while maintaining high image quality and a large exit pupil. Exit pupil of an optical system is analogous to the windows at your home, the larger the windows, the easier it is to see the outside world. It has been challenging to design and fabricate a large field of view and a large exit pupil for an eyeglass based display.
writes "We have all seen science fiction ideals of computer displays concealed in eyeglasses. One of the earlier spectacle-based designs was created by David Bettinger and disclosed in US Patent 4,806,011. Advances in fabrication technologies are now allowing complicated surface profiles to be manufactured. Exploitation of a complicated surface profile leads to low element count designs. Researchers at the University of Central Florida, CREOL/College of Optics & Photonics have designed and fabricated a computer monitor in eyeglasses that uses sophisticated surface profiles to achieve a compact design. The current specifications include an 8mm exit pupil, 20-degree field of view, 15mm eye clearance, and a resolution of 1.5 arcminutes. Follow the link for two pictures of this latest prototype."
Read on for some of the challenges in designing a workable eyeglasses-based display.