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EFA Diffractive Combiner Glass

Technical Information

Catalogue No: C1444
Category: Head-Up Display [HUD]
Object Type: Module/Sub-Assembly/Component
Object Name: EFA Diffractive Combiner Glass
Part No: 057930
Serial No: CA758X
Manufacturer: Thales Optronics
Platform(s): Typhoon (Eurofighter/EFA)
Year of Manufacture: 2012
Dimensions: Width (mm): 290
Height (mm): 230
Depth (mm): 220
Weight (g): 3,618
Location: Rack RAA13 (HUD DU Parts) [Mezzanine Store]



This is a ‘holographic’ Combiner Glass returned as scrap with damage.
The Part No. is taken from the 'Rejected Material' Tag. The Part No. may be a Thales code. The Scrap Tag shows an LRU Part No. as 79-180-05-07B which is presumed to be the unit that the glass was removed from.

79-115-xx-xxx denotes a Development EF2000 HUD
79-116-xx xxx denotes a Development EF2000 HUD Repeater
79-180-xx-xxx denotes a Production EF2000 HUD
79-181-xx-xxx denotes a Production EF2000 HUD Repeater

The Typhoon HUD has a single element combiner using new computer generated holographic techniques to take out the distortion. The Combiner assembly features a single element comprising two glass plates bonded to produce a flat parallel sided assembly. A complex reflective holographic optical element (HOE) is recorded on photosensitised gelatine on the spherical interface sandwiched in the assembly which acts as the collimating Combiner. The construction optics to manufacture the HOE incorporate a CGH that generates a phase shape that could not be done using conventional lenses.

The combiner is also flat which minimises real world distortion and provides a total field of view (TFoV) of 30deg x 25deg with an instantaneous field of view (IFOV) of 30deg x 20deg.

This design is capable of cursive, raster and hybrid operation with a sunlight readable raster display. The minimal support structure gives a remarkably clear out-of-cockpit view optimal for air-to-air combat. The two seat variant has a similar HUD in the rear seat which can display video from the forward HUD camera. This design represents probably the `ultimate HUD' in service to date in a combat aircraft. The key feature is integrity such that the pilot no longer needs to monitor the HUD against other instruments thus reducing workload compared to Tornado for example.

In 1990 the Company was awarded a £54million contract in which the Airborne Display Division lead a consortium with Teldix GmbH of Germany, Selenia of Italy, and CESELSA of Spain,  to develop the EFA Pilot’s Head Up Display.

During 1986 the Company research team (FARL) were beginning to make significant achievements on the use of Computer Generated Holograms (CGH) for HUD optics. A theoretical design showed the feasibility of a design with a 35deg off-axis angle being capable of installation in the F-16 envelope. Additional benefits were Combiner transmission of 80% and optical system end to end transmission of 40% compared to 20% on the conventional F-16C/D desin resulting in a much brighter display. This work involved collaboration between FARL, ADD and the Hirst Research Centre at Wembley and Marconi Research Centre at Great Baddow who provided the CGH and Hologram manufacturing facilities respectively. By 1989 this design was targeted at the proposals for EFA (European Fighter Aircraft ultimately to be the Typhoon) and also for the ATF (Advanced Tactical Fighter ultimately to be the F-22). ADD had begun the fabrication of a demonstrator which was completed by the end of 1991. This demonstrator consisted of a complex optical system containing tilted and de-centered lenses, aspheric components and a single holographic Combiner designed with the aid of CGH. The ‘double bounce fold ‘ arrangement was novel and was patented.


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