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

摘要

ABSTRACT OF THE DISCLOSUREAn optical diffraction grating element comprisingdiffraction gratings having a configuration in whichgrooves and flat lands each positioned between theadjacent grooves are successively alternately formed,wherein the diffraction gratings have the same groovedepth, groove width and groove tilt angle in order toobtain a constant 0th-order diffraction efficiency andfirst-order diffraction efficiency in the opticaldiffraction grating element while the pitches of thediffraction gratings are made different by setting adifferent land width for each diffraction grating.An optical pick-up device comprising an opticalsystem including a light source and an optical diffractiongrating element and a light receiving element, wherein theoptical diffraction grating element guides the 0th-orderdiffracted lights of a light beam emitted from the lightsource onto a recording medium and guides the first-orderdiffracted lights of a reflected light from the recordingmedium onto the light receiving element to produce aplurality of focused fight spots having the same lightamount.An optical scan device comprising a light source andan optical diffraction grating element movable relativelyto the light source, which is designed to substantiallylinearly scan a recording medium in a predetermineddirection with a uniform light amount of a light beamemitted from the light source as the optical diffractiongrating element moves relatively to the light source.