A plano-concave cylindrical lens has the curvature of a concave lens in the vertical direction and has no curvature in the horizontal direction. Used to amplify light in one direction, such as changing a laser beam into a line source or a sheet beam, or changing the height of the image without changing the width of the image. Combined with plano-convex cylindrical lens, the elliptical beam used for semiconductor laser is shaped into a circle.