OPTICAL DIFFRACTION GRATING ELEMENT, AND OPTICAL PICK-UP DEVICE AND OPTICAL SCAN DEVICE THAT RESPECTIVELY COMPRISE OPTICAL DIFFRACTION GRATING ELEMENT

摘要

An optical diffraction grating element comprising diffraction gratings having a configuration in which grooves and flat lands each positioned between the adjacent grooves are successively alternately formed, wherein the diffraction gratings have the same groove depth, groove width and groove tilt angle in order to obtain a constant 0th-order diffraction efficiency and first-order diffraction efficiency in the optical diffraction grating element while the pitches of the diffraction gratings are made different by setting a different land width for each diffraction grating. An optical pick-up device comprising an optical system including a light source and an optical diffraction grating element and a light receiving element, wherein the optical diffraction grating element guides the 0th-order diffracted lights of a light beam emitted from the light source onto a recording medium and guides the first-order diffracted lights of a reflected light from the recording medium onto the light receiving element to produce a plurality of focused fight spots having the same light amount. An optical scan device comprising a light source and an optical diffraction grating element movable relatively to the light source, which is designed to substantially linearly scan a recording medium in a predetermined direction with a uniform light amount of a light beam emitted from the light source as the optical diffraction grating element moves relatively to the light source.