The Secretary of State for Defence in Her Britannic Majesty's Government

Derek L Barter

John R Banbury

An optical system for a head-up display for example for producing a collimated image of a crt display on the external view of an aircraft pilot includes an optical relay unit including two elements (11,12) to produce a double fold in its optical axis to reduce the physical size of the relay unit. One of the two units (11), preferably of a diffractive type, is adapted to transmit light of the display color at a first angle of incidence and to reflect such light at a second angle of incidence. By use of a diffractive element having a narrow band reflectance, the system is extended to include embodiments for combining the display of two different color displays and a full color version using three crts is described.

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Aldershot, United Kingdom

Derek L Barter