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 and each having a same pattern presented thereon. The patterns, however and are rotated through an angle relative to each other. Together and the plates of the dual compensator can then be rotated ON the beam path through an angle to compensate for asymmetrical aberrations in the light beam. Dual compensators, having appropriate patterns, can be collectively used to compensate for astigmatism and coma and trefoil.
