In a system for continuously exposing desired patterns and their backgrounds on the surface of a target, a first electron beam emitted from a first electron gun is converged by condenser lenses and an objective lens to be focused on the surface of the target. A second electron beam emitted from a second...http://www.google.co.uk/patents/US4868395?utm_source=gb-gplus-sharePatent US4868395 - Electron beam lithography system for delineating a desired pattern on a target by means of electron beams
