Patent ID: 7872957

Claim:
An optical pickup comprising: a light source; a light focus device that focuses an outgoing beam emitted from the light source on a target recording layer of an optical recording medium; a diffraction element provided between the light focus device and the light source that diffracts the outgoing beam emitted from the light source into three light beams; an optical split element provided between the light focus device and the light source that splits a return light beam from the optical recording medium via the light focus device; a ¼ wavelength board provided between the light focus device and the optical split element that imparts an optical phase difference of ¼ wavelength to the outgoing light beam; a light reception device that receives the return light beam split at the optical split element at a receiving position; and a correction element provided between the light reception device and the light focus device that reduces an amount of an interfering light beam received at the reception device caused by an adjacent recording layer adjacent to the target recording layer, wherein the correction element is divided into multiple areas in a surface vertical to an optical axis, wherein each area of the multiple areas has a sub-wavelength convexo-concave structure having a pitch equal to or shorter than a wavelength of the outgoing light beam and the sub-wavelength convexo-concave structures of the multiple areas adjacent to each other have groove directions perpendicular to each other, and wherein filling factors of adjacent areas of the multiple areas are determined to substantially equalize effective refractive indices with regard to the polarization direction of the outgoing beam emitted from the light source and impart a phase difference of π with regard to a polarization direction perpendicular to the polarization direction of the outgoing beam emitted from the light source.