Abstract: A lens has an incidence axis, and comprises a lens element. The lens element comprises at least two sub-lenses. The sub-lenses are non-rotationally symmetric structures. Each of the sub-lenses comprises an effective light transmission portion. Any two effective light transmission portions of the lens element are rotationally symmetric relative to the incidence axis. The effective light transmission portions of the lens element allow an incident light beam to pass therethrough so as to present mutually separate formed images at an image side of the lens. The number of formed images is equal to the number of sub-lenses of the lens element.