Understanding Powell Lenses

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.

This even distribution is caused, surprisingly enough, by the rounded roof that characterizes the Powell lens. This two dimensional aspheric curve introduces a large spherical aberration into the system, and this spherical aberration is involved decreasing the light in the central area while increasing the light intensity at the edge. Thus instead of the non uniform Gaussian laser beam that would be produced by cylindrical lenses a uniform straight line is generated. Although there are other ways to perform uniform laser illumination, Powell lenses are by far the most powerful and flexible way to achieve this.