VARIABLE ANNULAR ILLUMINATOR FOR PHOTOLITHOGRAPHIC PROJECTION IMAGER

摘要

The illumination of a photolithographic projection imager (10) is given a variable annular intensity profile by using diverging and counter diverging elements (35, 36) that are movable relative to each other in the illumination path. An upstream element (35) diverges the illumination into an annular configuration, the radius of which is set by the distance downstream to the counter diverging element (36). Convex and concave conical surfaces on the movable elements can accomplish this.