1. An apparatus for providing a person with an augmented reality responsive to a scene that the person views, the apparatus comprising: a photosensor that images light incident on the photosensor; a light projector; a controller that controls the projector to project light that generates an augmenting virtual image (AVI) that is not projected onto the scene and having markers corresponding to homologous features in the scene; optics that directs light from the scene and light projected by the projector to form a first combined image on the person's retina comprising an image of the scene overlaid by the AVI, and a second combined image comprising an image of the scene overlaid by the AVI on the photosensor; wherein the controller configures the AVI responsive to the second combined image so that the markers in the first combined image are substantially coincident with the corresponding homologous features of the scene comprised in the first combined image.