Patent ID: 7428039

Claim:
Apparatus for illuminating a mask with a beam of radiation from a laser, comprising: a plurality of optical elements located on a longitudinal axis and arranged to project the laser-radiation beam onto the mask to illuminate the mask, the configuration and arrangement of the optical elements being selected such that the intensity of radiation in the laser-radiation beam on the mask is nearly uniform in a transverse axis of the beam, wherein the plurality of optical elements includes a first plurality of optical elements for projecting the laser-radiation beam onto the mask and at least two arrays of cylindrical microlenses for changing the distribution of radiation in the laser-radiation beam before the laser-radiation beam is projected such that the intensity of light across the mask has the nearly uniform distribution in the transverse axis of the beam, wherein the cylindrical microlenses in each of the arrays are aligned parallel to each other and parallel to the transverse axis; and at least one stop located between the microlenses and extending partially into the laser-radiation beam in a direction perpendicular to the transverse axis for optimizing the uniformity of radiation in the laser-radiation beam on the mask in the transverse axis, said at least one stop having a width less than the width of the beam at the location of the stop.