A helmet mounted display system comprising: a transparent visor; and an optical system which directs rays of light from a display produced by a display source onto a spherical region of the visor to provide by reflection at the visor, at a helmet wearer's eye position, a collimated virtual image of the...http://www.google.de/patents/US5543968?utm_source=gb-gplus-sharePatent US5543968 - Helmet mounted display systems
