Helmet Mounted Display for daytime missions should have large field of display, as well as undisturbed see-through vision. These requirements naturally lead to the use of the helmet visor as a display combiner. Previous projects were based upon non-spherical, mostly parabolic, tilted combiners. These optical projecting systems suffer from relatively large keystone distortion. This work presents a new optical concept for compensating the distortion, using a spherical surface as an optical combiner coupled to a complementary aberrative relay system.