An optical system suitable for use in machining plastics sheet material using a laser, brings a beam radiant energy in to a line focus on the work piece. The work piece is moving, and the line focus is perpendicular to the direction of such movement. The focused beam is scanned across the work piece...http://www.google.com/patents/US4099830?utm_source=gb-gplus-sharePatent US4099830 - Optical systems including polygonal mirrors rotatable about two axes
