| abstract |
An optical element for an optical pickup device includes a first optical surface including a superimposed diffractive structure including a plurality of circular bands each formed concentrically about an optical axis and cascaded into a plurality of steps, and concentrically about an optical axis. And a second optical surface that includes a diffractive structure that is formed and includes a plurality of circular bands each of which is divided by a step so as to generate diffracted light rays of a diffraction order whose absolute value is not less than one for the luminous flux.n n n n Optical pickup device, optical element, optical axis, circular band, superimposed diffractive structure, optical surface, absolute value |