Compact helmet mounted display

Claim 1

A display apparatus for use with headgear comprising, in combination: visor means adapted to attach to said headgear and having at least one concave semi-reflecting curved surface directed inwardly of the headgear and which, when the headgear is being worn, is at or is movable to a position at which it intercepts the forward line-of-sight of an eye of the wearer and is characterized in that the concave semi-reflecting surface is part of a paraboloid having an axis of rotation; an optical projector above the level of the wearer's eyes, by means of which luminous data is directed at said semi-reflecting surface for reflection thereby to the wearer's eye so that the wearer is presented with a virtual image of the luminous data within a predetermined field of view centered on the wearer's forward line-of-sight, said optical projector adapted to be attached to said headgear; parabolic mirror means interposed in the optical path from said optical projector to said semi-reflecting surface of said visor, whose shape, dimensions and position are such that rays from said optical projector are reflected in said parabolic mirror means; and fold mirror means, including first and second fold mirrors, said first fold mirror whose shape, dimension and position enable it to receive the rays from said parabolic mirror means and to direct the rays to said second fold mirror, said second fold mirror whose shape, dimension and position enable it to direct rays received from said first fold mirror to said semi-reflecting surface of said visor.