The User doesn't look through the display. The headset uses a magnifying Free-Form Prism, also invented by eMagin, that projects the image onto a Waveguide that BAE most likely developed as seen in the SA Photonics link below. Mantech also cooperated with and funded eMagin's development of the WUXGA display used in the SA-83-s and is used with all SAP's Militarized HMDs. These are State-of-the-Art .For obvious reasons over 12 iterations they have left folks guessing as the device's configuration which why it's Form-Factor is such a mystery. Not such a mystery if you familiarize yourself with this company.

https://www.saphotonics.com/vision-products/augmented-reality/sa-83-s/#overview4cd6-9bfc

https://www.army.mil/article/243150/army_sets_sights_on_advanced_manufacturing_of_eyepieces

https://www.emagin.com/images/products/svga/datasheets/1000874_Rev_A_WFO5_Prism_Optic_Specs.pdf

SA Photonics also cooperated with the development of the F-35 Helmet and the JHMCS used by Fighter Squadrons.