Head-up displays

Claim 1

Head-up display apparatus for displaying visual information to an observer in a vehicle, for example an aircraft, the observer having a field of view of the outside scene from which the observer receives light travelling in a predetermined direction relative to the vehicle, the apparatus comprising a source of light information signals, means to produce a collimated light beam carrying said light information signals travelling in a direction opposite to said predetermined direction, said source of light information signals and said means to produce a collimated light beam being mounted on the vehicle whereby said opposite direction is fixed with respect to the vehicle and the observer may move relative to said fixed opposite direction of the light information signals, and at least one cube corner reflector mounted on the observer''s head for movement with the observer''s head relative to said fixed opposite direction of the light information signals, the cube corner reflector being partially transparent and having three mutually perpendicular reflecting faces disposed to receive said collimated light beam and by reflection of said collimated light beam from each of said three mutually perpendicular reflecting faces to subject said collimated light beam to a sideways shift and to return said collimated light beam along a path parallel to its original path and in the opposite direction thereto, thereby superimposing an image of the light information signals carried in said collimated light beam on the field of view of the observer.