Diffraction grating having multiple gratings with different cycles for generating multiple beams and optical pickup using such diffraction grating

摘要

A diffraction grating for generating a plurality of beams includes a plurality of gratings. The plurality of gratings are formed to have an axis of symmetry perpendicular to the direction in which a beam is divided on a surface of diffraction grating and include at least two gratings having different fundamental cycles. The plurality of gratings are formed such that they have an axis of symmetry perpendicular to the direction in which a beam is divided on a surface of the diffraction grating, for generating a plurality of beams. The fundamental cycle increases as a function of the distance from the axis of symmetry, and therefore aberration in the periphery of scattering light may be reduced.