Wynne-Dyson projection lens with reduced susceptibility to UV damage

A Wynne-Dyson projection lens having object and image planes and an image field, and that has reduced susceptibility to compaction from ultraviolet radiation, the lens comprising along an optical axis:

• a concave mirror having a concave surface;
• a positive lens group spaced apart from the concave surface of the concave mirror;
• first and second prisms made of either fused silica or BSM51Y and disposed adjacent the positive lens group opposite the concave mirror and on respective sides of the optical axis, with the first and second prisms having respective surfaces that reside adjacent the object and image planes;
• wherein the positive lens group includes:
• a first lens element L1 made of S-FPL51Y, S-FSL5Y or fused silica;
• a second lens element L2 made of BSM51Y or BAL15Y;
• and a third lens element L3 made of S-FPL51Y, S-FSL5Y or fused silica;
• and
• wherein the projection lens has:
• a numerical aperture NA in the range from 0.16 to 0.2;
• a substantially unit magnification;
• doubly telecentricity;
• and a Strehl ratio of >0.95 over the image field for a spectral bandwidth that includes ghi radiation.

A Wynne-Dyson projection lens having object and image planes and an image field, and that has reduced susceptibility to compaction from ultraviolet radiation, the lens comprising along an optical axis:

• a concave mirror having a concave surface;
• a positive lens group spaced apart from the concave surface of the concave mirror;
• first and second prisms made of either fused silica or BSM51Y and disposed adjacent the positive lens group opposite the concave mirror and on respective sides of the optical axis, with the first and second prisms having respective surfaces that reside adjacent the object and image planes;
• first and second lens elements that define a cemented doublet, wherein the first lens element has a planar surface in contact with the prisms and that is made of either S-FPL51Y or S-FSL5Y, and wherein the second lens element is made of either BAL15Y or BSM51Y;
• a third lens element spaced apart from the second lens element and made of either S-FSL5Y or S-FPL51Y;
• and
• wherein the projection lens has:
• a numerical aperture NA of 0.16;
• the image field is 40×20 mm;
• a substantially unit magnification;
• doubly telecentricity;
• and a Strehl ratio of >0.95 over the image field for a spectral bandwidth that includes ghi radiation.