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Technical Information

Catalogue No: C0375
Category: Head-Mounted Equipment [HMD/NVG/Glasses]
Object Type: Module/Sub-Assembly/Component
Object Name: Eyepiece
Part No: None
Serial No: None
Manufacturer: Unknown
Division: Unknown
Year of Manufacture: Unknown
Width (mm):
Height (mm):
Depth (mm):
Weight (g):
Location: Rack RAA15 (HMDs) [Mezzanine Store]



This is an early prismatic eyepiece design probably from around the 1980’s. It was steadily refined to provide an ejection-safe Night Vision Goggle integrated within a specially designed helmet and also for the early Helmet Mounted Displays. The use of a prism allows a straight through view from the eye to the outside world but also allows an image from a CRT to be accurately superimposed over the outside world at the same focus such that the pilot sees both images as one. This system was used on the I-NIGHTS HMD for the US Navy. These early prisms were quite heavy, being solid glass, and gave a very forward centre-of-gravity.

INVS was the top of a range of helmet systems called Knighthelm™ which started with a simple monocular sight through to the full INVS. Another version in the family was called I-Nights.

I-Nights is an  Integrated Night Vision HMD providing sensor imagery and integrated night vision at night with flight and targeting symbology available both day and night. The binocular prismatic optical system provides a 40degree Field of View from a CRT and/or a NVG. The information (symbology and raster video) is projected onto a clear combiners placed in front of each of the pilot’s eyes. The system incorporates a one piece module for both day and night missions which clips on to an inner helmet shell such that the inner is form fitted to the pilot but the complex outer is interchangeable. The HMD operates with a pulsed DC Magnetic Tracker system.

The HMD was first flight tested used for PAH-1/AVT trials in Germany with the German Army Air Corps and also on the Integrated Night Vision Helmet (INVH) programme with the US Navy when comprehensive flight qualification testing was carried out in 1989 and 1990.The HMD was cleared for rotary wing and jet flight test (450 knot) and used with head-steered FLIRs. Other testing was carried out on  the F-16 (AFTI), German Airforce Tornado,  C-130 and a number of helicopters such as the BO-105,  Lynx, Gazelle, BK-117. A proposal was submitted to McDonnel Douglas in 1990 by the Company for the F/A-18 but was not successful.

An advanced version of the I-Night HMD was produced for USAF flight trials on the AFTI F-16.  This  system flew out of Edwards AFB and followed on from Falcon Eye using a dual FLIR sensor to provide both pilotage and targeting FLIR display to the pilot on his HMD. This was the first use of picture in picture to display pilotage FLIR over the full HMD field of view, with an inset pop up picture of the targeting FLIR imagery. Although the I-Nights did not progress beyond a trials programme this solution laid the foundation for BAE Systems future integrated HMD development.

Click to enlarge