RICHTUNGSBESTIMMENDER SENSOR MIT BESTIMMUNG DES EMPFANGSIGNALVERHAELTNISSES

An improved apparatus is disclosed for reliably and unambiguously sensing the angle of arrival of an electromagnetic radiation beam by a remote source. A sensor assembly (2) receives, through an optical window (22), the incident beam which is directed toward first and second detectors (10, 12) by a gradient beam splitter (24). The beam splitter (24) has a gradient of reference and transmittance deposited along one surface which is correlate to the angle of arrival of the radiation. The first detector (10) and second detector (12) receive a portion of the incident beam energy by reflection and transmission respectively from the beam splitter (24). The ratio of a difference to a sum of the detector responses to the received energy is thereby also correlated with the angle of arrival. Atmospheric scintillation, which causes shifting concentrations of energy in clusters or ''scintels'' within the beam, is compensated by the action of gradient opaque stripes of the beam splitter (24) which divide the beam by a constant factor irrespective of the energy distribution. Thus when the ratio of difference of sum of the response to the divided beam by the first and second detector (10, 12) is taken, the correlation with angle of arrival is not affected by the shifting energy.