Patent ID: 8149678

Claim:
An optical pickup including a semiconductor laser source, an objective lens for converging laser beam fluxes emitted from said semiconductor laser source to a predetermined recording layer provided inside an optical information recording medium, and an optical detector for independently receiving main luminous fluxes and sub-luminous fluxes reflected from said recording layer and detecting a predetermined signal, and a diffraction grating is interposed in an optical path between said objective lens and said optical detector, said diffraction grating comprising: a plurality of continuous grooves arranged periodically in a predetermined cycle and in a predetermined groove depth, wherein a grating surface of said diffraction grating is divided into a plurality of fine regions having a predetermined shape and said continuous grooves inside each of said fine regions is formed in such a fashion that a phase thereof is deviated by a predetermined quantity or unintentionally among adjacent ones of said fine regions; and wherein each of said fine regions is a rectangular region having a predetermined width and is arranged in such a fashion that a longitudinal direction of each of said rectangular fine regions is substantially parallel to each other.