Patent ID: 8755259

Claim:
An optical element having at least one surface divided into a plurality of regions, the optical element comprising: a first region configured to converge light with a wavelength λ 1 onto a storage surface of a first optical disc and converge light with a wavelength λ 2 onto a storage surface of a second optical disc; and a second region formed around the outer circumference of the first region and configured to converge light with the wavelength λ 1 onto the storage surface of the first optical disc, wherein the second region has a concave-convex structure concentrically formed on an aspheric surface and having a cross section being a saw teeth shape, the concave-convex structure is formed by a plurality of different saw teeth shapes, the plurality of different saw teeth shapes respectively give different phase differences corresponding to substantially integer multiples of the wavelength λ 1 , for light with the wavelength λ 1 , the concave-convex structure includes a first saw teeth shape that gives a first optical path difference, for light with the wavelength λ 1 passing through the second region, a second saw teeth shape that gives a second optical path difference, for light with the wavelength λ 1 passing through the second region, and a third saw teeth shape that gives a third optical path difference, for light with the wavelength λ 1 passing through the second region, and in at least a part of the concave-convex structure, at least the second saw teeth shape or the third saw teeth shape is present between the first saw teeth shapes, at least the first saw teeth shape or the third saw teeth shape is present between the second saw teeth shapes, and at least the first saw teeth shape or the second saw teeth shape is present between the third saw teeth shapes.