An optically thin sample of a sample material is analyzed by propagating probe electromagnetic radiation from a beam source along a plurality of different ray paths, directing each ray so that each ray path intersects upon the sample at a plurality of different locations where the rays interact with the sample material to cause a modification of the ray. The rays received at each of a plurality of detection spatial region are measured separately and the measurements analyzed to provide information about at least one property of the sample material at each interaction location. An analysis is carried out to trace the path of probe radiation from a location at the probe beam source to the detection spatial region on the detection surface so as to identify the interaction locations so as to provide information about the presence of target material at each interaction location.