F-35 notwithstanding, the head-up display (HUD) remains a fundamental part of almost every modern military aviation program.

But traditional HUD design incorporates a number of heavy, degradable and maintenance-intensive components.

BAE's Electronic Systems division claims that its new DLE (Digital Light Engine) technology can solve these problems for both new-build aircraft and extant fleets.
“DLE is just a digital way of generating the image source rather than doing it through a cathode ray tube [CRT],” explains Chris Colston, business development director for BAE's advanced displays at Rochester.

“There are many issues with CRTs. They degrade through life so their intensity and brightness tails off and you need to be able to adjust and cater for that. The older they get the higher you have to power them. The DLE solution effectively removes the CRT, which increases display resolution. It gives a display that is consistent and doesn't degrade with time.”

The solution removes the CRT, its power supply, and some of the optics, so it is considerably lighter and, Colston says, cheaper. Ballast would need to be added in a retrofit, but the design would replace the legacy CRT HUD without the need for cockpit redesign or re-cabling.

The technology also underpins a new BAE HUD product called LightHUD, which uses waveguide optical technology instead of conventional optics. A waveguide is effectively two pieces of glass sandwiching a diffraction grating. “Every time light hits the grating some of it escapes,” Colston says, “and if you can manage the physics of that you can create an image.”

By generating the HUD imagery in the waveguide rather than through an optical system, further expensive and heavy elements can be taken out of the HUD. This frees up space in the cockpit, enabling a high-performance HUD to be more easily integrated with the sort of wide-area display and multi-function flat-screen systems that are becoming the norm in next-generation cockpits.

When waveguide technology is combined with the DLE, Colston says the system offers “a ten-fold improvement in reliability and a 50% reduction in repair costs” over a conventional CRT-based HUD.