If light from the image source becomes misaligned with respect to the pupil, a physical positioning mechanism adjusts the relative positions of the image source and the beam combiner so that {HEAD ~ light} from {TAIL ~ the image source} is translated relative to the pupil, thereby realigning the display to the pupil 
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If light from the image source becomes misaligned with respect to the pupil , a physical positioning mechanism adjusts the relative positions of the image source and the beam combiner so that { HEAD ~ light } from { TAIL ~ the image source } is translated relative to the pupil , thereby realigning the display to the pupil
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