A head- or face-mounted display apparatus which enables observation at a field angle of 40.degree. or more and provides an image which is flat and clear as far as the peripheries thereof. The display apparatus has a two-dimensional image display element (1), a relay optical system (2 and 3) for projecting...http://www.google.com/patents/US5436765?utm_source=gb-gplus-sharePatent US5436765 - Visual display apparatus
