Abstract: A head mounted display is disclosed that utilizes a single video display screen to transport images to both eyes. Multiple reflections are created by illuminating the display screen form a plurality of directions, or by illuminating the display screen with light beams of differing polarizations. The reflections of the display screen are focused in order to reduce the splitting volume and then redirected by a plurality of reflective surfaces located near the focal point of the display images. Different images may be sent to each eye of a user by interlacing multiple data streams for the display and linking each data stream with a specific illumination direction, or specific polarization.

Abstract: An instrument for measuring positions and displacements of portions of a human body, comprising a base plate and a belt or suction cup for detachably securing the base plate to a portion of a human body. A bifurcated holder is mounted on the base plate for rotation about a first axis, the bifurcated holder having a pair of arms, and a housing is pivotally carried between these arms for swinging movement about a second axis perpendicular to the first axis. A dip circle and a north-south-seeking compass are carried by this housing, the dip circle and compass being mounted on the housing for pivotal movement about a common third axis perpendicular to the second axis. The base plate has a scale thereon, and there is an indicator on the holder for indicating on the scale the degree of rotation of the holder relative to the base plate.