Design of F - Theta Lens Used in Laser Marking Machine

The lens, whose image height is proportional to its field view angle through introducing reasonable barrel distortion so as to scan or mark linearly is called F-theta lens. Design of F-theta lens is introduced in the paper. The design idea and method are illustrated in detail through the analysis of two systems with working area of 200×200mm and 500×500mm. They’re simple and compact. Both of them are composed of only three spherical lenses with two kinds of common optical glasses. Their tube length (from the front surface of the first lens to the back surface of the last one) is far less than 100mm. Remarkably, such simple lenses are able to obtain diffraction-limited focusing performances and low distortions less than 0.5 percent relative to F-Theta linear relation.