A detection
system is described (100) for detecting
luminescence sites on a substrate (6). The detection
system (100) typically comprises an
irradiation unit (102) for generating at least one excitation
irradiation beam for exciting
luminescence sites on the substrate (6). The at least one excitation
irradiation beam may be a plurality of excitation irradiation beams. The detection
system (100) also comprises a first optical element, e.g. refractive element (25), adapted for receiving at least two irradiation beams of different wavelengths or
wavelength ranges, the at least two irradiation beams being excitation irradiation beam(s) to be focused on a substrate and / or
luminescence irradiation beam(s) to be collected from the excited luminescence sites on the substrate (6). The detection system (100) also comprises an optical compensator for adjusting at least one of the at least two irradiation beams of different wavelengths or
wavelength ranges so as to reduce or compensate for optical aberrations. The present invention also relates to a corresponding method for detecting, a
phase plate and a method for designing such a
phase plate.