Patent ID: 7253376

Claim:
An optical apparatus for truncating a line image formed with coherent radiation, comprising an optical relay system having an aperture plane, a pupil plane, and an image plane, in that order, with the aperture plane conjugate to the image plane, the optical relay system disposed to receive an incident beam of coherent radiation at the aperture plane and to form from said beam of coherent radiation an untruncated line image having first and second ends, a length and a maximum intensity in said image plane, the optical relay system additionally having an apodizing pupil filter arranged at the pupil plane and a variable aperture arranged in the aperture plane and adapted to progressively truncate the incident radiation beam to progressively truncate the line image from the first and/or second end wherein the apodizing pupil filter acts to reduce diffraction of the beam from the variable aperture during truncation of the image so that the truncated image has a maximum intensity substantially equal to or less than the untruncated image maximum intensity.