Abstract: A common lens HMD is shown and described. The use of a common lens in a biocular or binocular helmet mounted display (HMD) system provides a means to manipulate light rays from an image(s) which are traveling from two or more separate upstream optics trains to the helmet visor and onward to each eye, with fields of view which overlap at the midpoint of the visor. The common lens changes the optical paths of each individual ray going to a single eye, and changes the corresponding ray traveling to the other eye in a mirrored fashion (i.e. with the opposite component in the Left/Right direction).