Short‐wavelength annular‐field optical system for imaging tenth‐micron features

We have found that the 1:1 Offner annular‐field system can provide high‐resolution imaging in the extreme ultraviolet (XUV) when used at numerical apertures (NA’s) around 0.1. For example, when illuminated with radiation at wavelengths shorter than 15 nm, a 0.0835‐NA system with a 233.6‐mm‐diam primary mirror should be able to image 0.1‐μm lines and spaces in a 100‐micron‐wide, 50‐mm‐radius ring‐shaped field at high contrast.