Patent ID: 8565059

Claim:
An optical pickup device comprising: a laser diode configured to emit a laser beam; an objective lens configured to collect the light beam emitted from the laser diode and configured to irradiate a multilayer optical disc with the collected light beam; a diffraction element configured to diverge the light beam reflected from the multilayer optical disc into diverging light beams, the diffraction element having: a first divided area, a second divided area, and a third divided area, that are mutually exclusive, wherein the first divided area is located along a straight line passing through an approximate center of the diffraction element and extending in a direction generally parallel to a track of the multilayer optical disc, wherein the second divided area is located along a straight line passing through the approximate center of the diffraction element and extending in a direction generally perpendicular to the track of the multilayer optical disc, and wherein the third divided area includes a center of the diffraction element; and a detector having a plurality of detection portions configured to receive the diverging light beams caused by the diffraction element, the detection portions allocated to a first group and a second group, wherein the first group, of at least four detection portions, is configured to detect a 0th-order diffracted light from the first divided area, the second divided area, and the third divided area, and wherein the second group, of at least two detection portions, is configured to detect the light beam diffracted at the first divided area into first diffraction order (±1st-order) light, or higher diffraction order light, and is aligned in a direction generally perpendicular to the track of the multilayer optical disc.