Optical arrangements for head-up displays and night vision goggles

Claim 1

An optical arrangement for a helmet mounted head-up display or night vision goggle comprising: an optical projector operable so as to form at a predetermined image plane a real image of optical data (F) to be displayed, and below said projector a body of light refractive material (55, 59) which serves as an eyepiece (21a, b) for viewing of the image by an observer, said body having a first external input surface (59) in generally parallel relationship with said image plane, a flat external output surface (63), a second external input surface (67) parallel to said output surface, and between said output surface and said second input surface an internal partially light transmissive, partially light reflective surface (54) whereby the observer is presented with a view of a scene forward of the observer through the eyepiece on which is superimposed a view of said image characterised in that said output surface (63) is inclined with respect to the first input surface (59) and said internal surface (54) is concavely curved towards said output surface such that light rays emanating from said image and entering said body (55, 57) at said first input surface (59) are refracted at said first input surface, totally internally reflected at said output surface, reflected at said internal surface (54) and finally transmitted through said output surface for viewing by the observer.