1. A method for imaging two target structures in two parallel layers, respectively, of a sample, the method enabling determination of a registration between the two target structures along two mutually perpendicular axes of the layer, the method comprising: (a) illuminating the sample with incident radiation to produce a radiation response of the sample to said incident radiation; (b) collecting the radiation response by an objective lens arrangement; (c) splitting the collected radiation response into two spatially separated radiation components and directing the split radiation components towards at least one imaging plane along different optical channels characterized by optical paths of different lengths, respectively; (d) detecting said two split radiation components in said at least one imaging plane, thereby concurrently acquiring two image parts, each containing images of the two target structures, and enabling determination of the relative distance between the two target structures.