Patent ID: 7835250

Claim:
An optical pickup that focuses a light beam onto an optical recording medium having a spiral shaped recording track, and receives the light from that light beam that is reflected by the optical recording medium, comprising: a diffraction device for diffracting a light beam that is emitted from a light source and emitting a main beam and first and second sub beams; a focusing device for focusing the main beam and first and second sub beams onto the optical recording medium at positions that are shifted a specified amount in the tangential direction from the radial axis that passes through the center point of the recording track; a light receiving device for receiving the light from the main beam and first and second sub beams that is reflected from the optical recording medium, and outputting an optical signal that corresponds to each beam; an inter-beam distance adjustment device for controlling the diffraction device according to the tangent angle of the recording track near the positions where the main beam and first and second sub beams are focused, and changing the distance in the radial direction between the main beam and first and second sub beams on the optical recording medium; a push-pull signal generation device for generating push-pull signals that corresponding to the main beam and first and second sub beams based on the received optical signals that correspond to the main beam and first and second sub beams; wherein the inter-beam distance adjustment device changes the distance in the radial direction between the main beam and first and second beams on the optical recording medium to a distance so that the value of the difference between the push-pull signal that corresponds to the first sub beam and the push-pull signal that corresponds to the second sub beam becomes almost zero.