A head mounted display with a first display element (104, 106) and a second display element (104, 106) comprising a system for detecting angular displacement of the first display element relative to a reference position on a head mounted display device for displaying virtual images to the first display element and the second display element with binocular disparity, the system comprising: an alignment detection assembly, comprising: a group of light sources (130, 140) for emitting light, a direction of light emitted from at least one light source in the group of light sources changing upon an angular displacement of the first display element and the direction of light emitted from the at least one light source changing upon a linear displacement of the first display element, and wherein the group of light sources comprise a first group of light sources affixed to the first display element, the alignment detection assembly further comprising a second group of light sources, for emitting light, affixed to the second display element, a direction of light emitted from at least one light source in the second group of light sources changing upon an angular displacement of the second display element and the direction of light emitted from the at least one light source in the second group of light sources changing upon a linear displacement of the second display element, the group of light sources being arranged to collimate light from the at least one light source in the first group of light sources affixed to the first display element; and collimate light from the at least one light source in the second group of light sources affixed to the second display element; a camera for receiving light from two or more light sources in the group of light sources, the camera comprising: a collimated lens for receiving the light from the two or more light sources, and an image plane of a photo detector for receiving light through the collimated lens placed at the focal length of the collimated lens, the camera registering an angular displacement of the first display element while being insensitive to a linear displacement of the display element; and a processing unit in communication with the alignment detection assembly and receiving feedback from the camera, the processing unit determining the angular displacement of the first display element from the feedback and the processing unit adjusting a display of the virtual images to the first display element to correct a change in the binocular disparity due to the angular displacement of the first display element; an alignment detection assembly, comprising: a group of light sources (130, 140) for emitting light, a direction of light emitted from at least one light source in the group of light sources changing upon an angular displacement of the first display element and the direction of light emitted from the at least one light source changing upon a linear displacement of the first display element, and wherein the group of light sources comprise a first group of light sources affixed to the first display element, the alignment detection assembly further comprising a second group of light sources, for emitting light, affixed to the second display element, a direction of light emitted from at least one light source in the second group of light sources changing upon an angular displacement of the second display element and the direction of light emitted from the at least one light source in the second group of light sources changing upon a linear displacement of the second display element, the group of light sources being arranged to collimate light from the at least one light source in the first group of light sources affixed to the first display element; and collimate light from the at least one light source in the second group of light sources affixed to the second display element; a camera for receiving light from two or more light sources in the group of light sources, the camera comprising: a collimated lens for receiving the light from the two or more light sources, and an image plane of a photo detector for receiving light through the collimated lens placed at the focal length of the collimated lens, the camera registering an angular displacement of the first display element while being insensitive to a linear displacement of the display element; and a collimated lens for receiving the light from the two or more light sources, and an image plane of a photo detector for receiving light through the collimated lens placed at the focal length of the collimated lens, the camera registering an angular displacement of the first display element while being insensitive to a linear displacement of the display element; and a processing unit in communication with the alignment detection assembly and receiving feedback from the camera, the processing unit determining the angular displacement of the first display element from the feedback and the processing unit adjusting a display of the virtual images to the first display element to correct a change in the binocular disparity due to the angular displacement of the first display element;