1. A compact display device for transmitting an image to a user's eye, the display device comprising: a head-mountable support fixture comprising an elongated member having a first end and a second end; a projection system including a display operative to provide an image, the support fixture attached at the first end to the projection system; and an eyepiece assembly attached to the second end of the support fixture; wherein the support fixture maintains the projection system and the eyepiece assembly in alignment along an optical path through free space between the projection system and the eyepiece assembly, with the projection system disposed to transmit the image on the optical path and the eyepiece assembly disposed to receive the image from the projection system and to direct the image to the user's eye; and wherein the eyepiece assembly comprises a non-axial optical system including a modified Mangin mirror comprising a solid optical material having an external entrance and exit surface and an internal reflective surface, the material arranged and having an index of refraction selected so that light from the projection system incident on the external surface is refracted as the light propagates into the material and light within the material is reflected off the internal reflective surface and is refracted at the external surface as the light exits the material, whereby off-axis aberrations are reduced.