GB1223173A - Improvements in or relating to head-up displays - Google Patents

Abstract

1,223,173. Head-up display apparatus. PILKINGTON PERKIN-ELMER Ltd. June 20, 1969 [June 29, 1968], No.31226/68. Heading G2J. A head-up display apparatus comprises a source 5 of light information signals, means 7 to collimate light therefrom to travel in the opposite direction to light 1 from a distant scene, and at least one retroreflector 10 adapted to reflect light from the collimated beam to travel along a path parallel to its original path but in the opposite direction so as to superimpose an image of the light information signals on the field of view of an observer 4. As shown, signals displayed on a C.R.T. 5 are collimated by means 7 which comprises an apertured concave spherical mirror 8 and a convex spherical mirror 9 such that collimated light may pass either side of the observer's head to be reflected by a pair of retro-reflectors 10 into the observer's eyes. The retro-reflectors 10 which may be mounted on a spectacle frame have two of the three mutually perpendicular faces fully reflecting and the third face partially reflecting and are so positioned that the light 1 entering through an aircraft windscreen 2 may pass through the partially reflecting face into the observer's eyes. In a second embodiment two C.R.T. 11, 12 having appropriate collimating means are provided. Lens systems may replace mirrors 8, 9 and the reflecting surfaces of the retro-reflectors 10 may be provided with filters such as di or tri-chroic coatings.