an apparatus for measuring and evaluating a subject &# 39 ; s visual field includes a projector for presenting a target image , consisting of a spot of light , at a series of selected locations within the subject &# 39 ; s visual field . a mirror is mounted for movement about a pair of axes and is rotated to a desired attitude by step motors which control the position of the mirror about the respective axes . a light beam is directed toward the mirror and is reflected in a direction dependent on the attitude of the mirror as controlled by the step motors .