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Abstract

The present invention relates to a method to measure the angle of incidence for radiation and a detector to carry out the method. The background for the invention is that in certain electromagnetic radiation, for example laser light of different wavelengths from UV to IR, there occurs an irregularity, speckledness, that is among other things caused by turbulence in the atmosphere. This phenomenon gives rise to problems during the registration of a single or a few short pulses of radiation. The probability of detection can decrease considerably at the same time as difficulties to reliably determine the angle to the source of radiation with high resolution can arise. This problem is solved by the invention by placing at least two detectors (a,b,c,d) so far apart that they receive an irradiance that is essentially un-correlated in the case of speckled radiation and that the detectors are made of two detector elements (1,2) that are mounted so close to each other that both detector elements receive essentially the same irradiance and in such a direction that the normals of respective detector element form a known angle (.beta.) with each other. One then calculates the angle of incidence (.alpha. ) by means of the signals (S.sub.1,S.sub.2) from the detector elements (1,2), that depend on the shape of the sensitivity beams, and said angle (.beta.) between the detector elements.

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First Claim