Helmet supported optical systems

Claim 1

A helmet supported optical system which provides an eye of a wearer (11 or 49) of a helmet (7 or 35) with a direct view of the scene forward of the wearer (11 or 49) on which is superimposed collimated optical imagery, said system comprising: an eyepiece (1 or 47a, 47b) comprising a body of light refractive material, supported with resepct to the helmet (7 or 35) in front of a position (9 or 33a, 33b) for said eye defined with respect to helmet axes, having: a light input face (15); a boundary surface (17) opposite said input face (15); substantially flat and parallel fore (18) and aft (19) faces; and, internally of said body bridging the space between said input face (15) and said boundary surface (17), an aerially extensive region (21 or 46a, 46b) concavely curved towards said aft face (19) and possessing both light reflective and light transmissive properties; and means (5 or 37a, 37b, 39a, 39b, 41a, 41b, 43a, 43b) supported with respect to the helmet (7 or 35) operable to develop a bright data representation at a plane (31 or 44a, 44b) substantially congruent with the principal focal plane of said aerially extensive region (21 or 46a, 46b) and defined with respect to said input face (15) of the eyepiece (1 or 47a, 47b) such that light from said bright data representation developed at said plane (31 or 44a, 44b) entering said eyepiece (1 or 47a, 47b) at said input face (15) is: internally reflected forwardly toward said aerially extensive region (21 or 46a, 46b); partially reflected by said aerially extensive region (21 or 46a, 46b) rearwardly towards said aft face (19); and transmitted through said aft face (19) to the said position (9 or 33a, 33b) for said eye, characterised in that, between said means (5 or 37a, 37b, 39a, 39b, 41a, 41b, 43a, 43b) operable to develop said bright data representation and said input face (15) of the eyepiece (1 or 47a, 47b), there is a second body (3 or 45a, 45b) of light refractive material having: a first face (25) by way of which light from said bright data representation can enter said second body (3 or 45a, 45b); a second face (27) having a mirror coating; and a third face (29) confronting said input face (15) of the eyepiece (1 or 47a, 47b), the conformation of said second body (3 or 45a, 45b) of light refractive material being such that rays from said bright data representation entering said second body (3 or 45a, 45b) at said first face (25) are: reflected at the mirror coating on said second face (27) back to the said first face (25) such that they are incident on said first face (25) at angles greater than the critical angle of said second body (3 or 45a, 45b) to air; are totally internally reflected at said first face (25) to said third face (29); and transmitted through said third face (29) to said input face (15) of the eyepiece (1 or 47a, 47b).

Claim 6

A system according to any one of the preceding claims wherein said second (27) and third (29) faces are inclined at acute angles (ϑ₁, ϑ₂) to said first face (25).