Patent ID: 7599128

Claim:
An imaging lens comprising a liquid crystal lens and a refractive lens laminated together; the refractive lens being a refractive lens having a positive refractive power; the liquid crystal lens comprising: a pair of transparent substrates disposed so as to be opposed to each other, a Fresnel diffraction lens surface and a transparent electrode formed on one of the opposed two surfaces of the pair of transparent substrates, a transparent electrode formed on the other one of the opposed two surfaces of the pair of transparent substrates, and a liquid crystal layer filling the concave/convex portion and sandwiched between the transparent substrates; the Fresnel diffraction lens surface having a saw-tooth-shaped cross section and consisting of concentrically arranged annular concave/convex portions; wherein the liquid crystal lens is configured so that the alignment state of the liquid crystal layer is changeable by applying a voltage to the liquid crystal layer by supplying a power from an external power source to the transparent electrode; wherein the imaging lens is configured so that its focal length is changeable by changing the applied voltage to the liquid crystal lens, wherein the liquid crystal lens is a laminated liquid crystal lens comprising first and second liquid crystal lenses; and each of the first and second liquid crystal lenses are configured so that its refractive power for linearly polarized light of predetermined polarization direction is changeable by changing alignment state of liquid crystal layer by applying a voltage to the liquid crystal layer by supplying a power to the transparent electrodes from an external power source respectively; wherein the laminated liquid crystal lens comprises the first liquid crystal lens and the second liquid crystal lens laminated so that their predetermined polarization directions are perpendicular to each other, and wherein the phase functions of the respective Fresnel diffraction lens surfaces of the respective liquid crystal lenses constituting the laminated liquid crystal lens, are different from each other.