Powell lenses are laser line generator lens that can fan out collimated beams in one dimension. They have the shape of a prism with a rounded roof, and are often used to transform a narrow laser beam into a uniformly illuminating line. While a cylindrical lens produces a poorly illuminated line with fading edges and a hot spot at the center, the straight lines produced by Powell lenses have an even distribution of energy and an even distribution of light along the line.