DIFFRACTION GRATING, OPTICAL PICKUP USING THE SAME, AND OPTICAL INFORMATION PLAYBACK DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an optical pickup or an optical information playback device having practically satisfactory tracking control performance as a super-multiple optical pickup using an in-line type DPP system while securing a dynamic range equal to or more than conventional one in a DPP signal amplitude to the change of a track pitch.

SOLUTION: A diffraction grating dividing a luminous flux emitted from a laser light source into three luminous fluxes is divided into four regions as shown in the figure and a grating groove periodically disposed in each region is disposed so that phase relation of the disposition of the grating grooves periodically disposed in each region is made to be a prescribed phase relation between each region.

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