An optical system for forming a final image of a non-circular light source on a workpiece with a desired non-circular cross-section and desired size B includes a plurality of spaced lenses. The plurality of lenses are arranged with spaced upstream and downstream lenses which are configured to transmit the beam emitted by the light source. The optical system is configured with an F-theta lens spaced downstream from the downstream lens and converging the beam incident thereon so that the beam has a final waist. The F-theta and downstream lenses are spaced apart so that F ⁢ ⁢ 4 Fth = A B , wherein F4 a positive focal length of the downstream lens, Fth is the negative focus of the F-theta lens, B is the desired size of the final image, and A is a size of a preliminary noncircular image of the source different from the desired size B.