An optical system includes a pair of adjacent cylindrical lenses and a target positioned in a round-spot plane following the pair of cylindrical lenses. At least one of the cylindrical lenses is rotatable about the optical axis, relative to the other cylindrical lens. A collimated light beam is incident on the pair of cylindrical lenses. Rotating the cylindrical lenses relative to each other allows changing the size of a round spot (or symmetrically scaling an image) at a given target location. Additional optical elements, for example a spherical lens, may be placed after the pair of cylindrical lenses. In various embodiments, the pair of cylindrical lenses may include two positive lenses, or a positive and a negative lens.