Abstract: Several virtually punctiform, sequentially excited sources of luminous radiation on a pilot's helmet facilitate continuous determination of the pilot's line of sight with the aid of a linear array of photoelectric cells illuminated via a pair of mutually parallel cylindrical lenses perpendicular to the array. The light path through one of these lenses includes a beam rotator in the form of two juxtaposed prisms which turns one of two sheets of light rays from an excited source, lying originally in two mutually orthogonal planes, through 90.degree. into a plane including the axis of one of the lenses so as to intersect the array in one point while the other sheet of light rays retains its orientation in passing through the axis of the other lens to intersect the array in another point.

Abstract: A sensor system for determining the spatial location of radiation relative to the sensor including three unit sensors each having a cylindrical optical lens and a linear array of photosensitive elements positioned in the focal plane at a fixed angle with respect to the longitudinal axis of the lens. Each lens determines substantially a plane of radiation passing through the source. The unit sensors are arranged to define three separate planes having the radiation source being detected as common point. The detected signals are processed to identify respectively the serial position of the elements activated by the focused radiation. Ancillary calculating means calculates the location of the source from the serial position information. By detecting a plurality of sources coupled to a movable body, the present invention enables the user to continuously determine the direction of a fixed axis of the movable body.