Abstract

A helmet-mounted display (HMD) provides the pilot with a dedicated visually coupled interface that offers increased vision as well as improved target acquisition and weapons delivery. The HMD presents the wearer with avionics symbology superimposed on sensor imagery or a natural scene. The flight scene may consist of a sunlit terrain or it may consist of the output of a night vision sensor or FLIR. Two recent conferences have examined the latest uses of HMD optical systems in tactical aircraft, rotocraft, simulators, and land vehicles.^1,2 Current HMD systems have advanced to the point where reducing the headborne weight and maintaining a reasonable center of gravity is technically difficult. Concentrating on the helmet optical system, it remains possible to achieve weight reductions through the use of optical glasses of lower density and by reducing the overall number of optical elements. For systems consisting of conventional optics, such modifications usually give rise to inferior system performance whether it be decreased field-of-view, reduced unvignetted exit pupil or increased chromatic aberration. We have investigated the use of combinations of refractive and surface-relief diffractive elements in the relay lens to provide increased wavefront and color correction.

© 1991 Optical Society of America