<human>: What is the difference between a spherical, cylindrical and an ellipsoid lens?
<bot>: Spherical Lens: A spherical lens is one that has a curved surface. It can focus light in all directions equally. Cylindrical Lens: A cylindrical lens is one that has a curved surface along its length. It can only focus light in one direction. Ellipsoidal Lens: An ellipsoidal lens is one with two curved surfaces. It can focus light in two different directions.