F-4 PeriHUD Combiner Assembly

F4J Combiner Prism
Supplier Part No 012800
Buyers Part No 229-002643
Serial No ??-623

The optical system used beam splitting surfaces which allowed the pilot to "look around" the CRT. In 1975 Marconi Avionics manufactured a Staff Ellis design called the PeriHUD. It was so called because the optical system folded the CRT image, in the manner of a periscope, to both sides of the CRT where the image is combined with the outside world view. This allowed the pilot to effectively look around the CRT thus providing a very shallow glareshield mounted unit. A Field of View of 17° H x 17° V was achieved. The design can be installed aft up to the ejection line and because of its shallow depth can be placed on top of existing instrumentation. The HUD was test flown in an F-4J but never went into production.

This is the optical prism that formed the PeriHUD optical combiner.