Diffraction grating, optical pick-up, error signal detection device, and error signal detection method

摘要

An optical pick-up generates a 0-th order diffraction light and 1st order diffraction lights by a diffraction grating and irradiates the same to an optical disc. The 1st order diffraction lights have phase distributions equivalent to a wavefront aberration of the optical disc when there is a tilt in the optical disc. Distances between the center of the main optical spot and centers of sub optical spots in a disc radial direction on a recording surface are whole multiples of a track pitch. The generation circuit generates a main push-pull signal corresponding to the 0-th order diffraction light and first and second sub push-pull signals corresponding to the 1st order diffraction lights and generates tracking error signals TE as differential push-pull signals obtained by subtracting a sum signal of the first and second sub push-pull signals from the main push-pull signal