ZnSe Plano-Convex cylindrical focusing lens (LZCY) & Plano-Concave cylindrical focusing lens (LZCY). Cylindrical focusing lenses are either round or rectangular objects with cylindrically shaped surfaces. They differ from spherical lenses in that they focus a beam on a focal line rather than a focal point. Its applications include laser scanners, laser diode systems, spectrophotometers, projectors and optical data storage and retrieval systems.