Optical Eyepiece assembly large

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Marconi Avionics Ltd began development of CRT based helmet displays in about 1979 and some of the first Helmet displays (HMD) designed for rotary wing application were delivered to DRA Farnborough in 1988.These early designs were produced by the Flight Automation Research Laboratory then at New Road in Chatham.
The design had an optical assembly with side mounted Cathode Ray Tubes projecting into an optical relay folding the image around to a prismatic eyepiece, diameter 17mm, which gave a 40 degree fully overlapped binocular field of view. This was a rather large assemble, quite heavy and with a resultant forward centre-of-gravity not ideal for an HMD. Further work extended the field of view to 55 degrees in each eyepiece which enabled a partially overlapped horizontal field > 70°
A full colour version with > 60° FOV per eye was produced for simulator trials with the ability to vary the binocular overlap
Some flight testing in a Lynx helicopter took place, in conjunction with a nose mounted gimballed FLIR platform
This unit is a prototype for HMD.