Patent ID: 7817524

Claim:
An optical head device for performing at least one of recording and reproducing of information for a plurality of types of optical recording mediums, comprising: a light source for emitting light; an objective lens for focusing the light onto an optical recording medium; and a diffraction element disposed between the light source and the objective lens, the diffraction element having a plurality of diffracting planes, wherein the light source emits a plurality of kinds of light having mutually different wavelengths, positions for emitting the plurality of kinds of light from the light source are mutually deviated, the plurality of kinds of light includes first light and second light, the plurality of diffracting planes includes first and second diffracting planes, a distance between a center of the first light and a pattern center of the first diffracting plane is shorter than a distance between a center of the second light and the pattern center of the first diffracting plane, a distance between the center of the second light and a pattern center of the second diffracting plane is shorter than a distance between the center of the first light and the pattern center of the second diffracting plane, a ratio of diffraction for diffracting the first light by the first diffracting plane is higher than a ratio of diffraction for diffracting the first light by the second diffracting plane, and a ratio of diffraction for diffracting the second light by the second diffracting plane is higher than a ratio of diffraction for diffracting the second light by the first diffracting plane.