The present invention provides a method for measuring lens aberration of light on a wafer. The method includes printing a pattern on the wafer by projecting the pattern through a lens in a plurality of pitches and directions; measuring a plurality of critical dimension (CD) differences between two locations...http://www.google.ca/patents/US6459480?utm_source=gb-gplus-sharePatent US6459480 - Measurement method of Zernike coma aberration coefficient
