Patent ID: 7911926

Claim:
An optical disc drive for reading and/or writing data from/on an optical disc, the drive comprising: a light source for emitting a light beam; an objective lens for converging the light beam, the lens having an aperture radius r 0 ; an optical branching element for dividing the light beam that has been reflected from the optical disc into multiple branched light beams; a photodetector, on which at least some of the branched light beams are incident and which generates signals representing the intensities of the respective incident branched light beams; and opaque portions for cutting off the light beam partially, wherein if xy coordinates are defined on a virtual plane, which intersects with the center axis of the objective lens at right angles, such that an x-axis is parallel to a radial direction of the optical disc and that a y-axis crosses the x-axis at right angles, the opaque portions prevent the light beam from passing through areas of the virtual plane that are defined by coordinates (x, y) satisfying |x|>a, |y |>b and a 2 +b 2 <r 0 2 (where a and b are positive real numbers).