A device to compensate for asymmetrical aberrations in a beam of light includes at least one dual compensator positioned on the beam path. Structurally, the dual compensator includes two juxtaposed plates, each having a same pattern presented thereon. The patterns, however, are rotated through an angle α relative to each other. Together, the plates of the dual compensator can then be rotated on the beam path through an angle β to compensate for asymmetrical aberrations in the light beam. Dual compensators, having appropriate patterns, can be collectively used to compensate for astigmatism, coma and trefoil.
