OPTICAL PICKUP DEVICE USING HOLOGRAM PATTERN AND HOLOGRAM PATTERN GENERATING METHOD

摘要

Astigmatism and coma are suppressed in an optical pickup device of the type that light from a single real laser light source (11) is diffracted and divided by a hologram module (13) into a plurality of light spots which are focussed upon a plurality of tracks of an optical disk to read data on the tracks at the same time. A non-diffraction hologram pattern (14) and diffraction hologram patterns (15a, 15b, 15c) of the hologram module (13) are determined so that light diffracted by the hologram module is given inverse aberration of that to be caused by optical elements in an optical path from the real laser light source (11) to the optical disk. Another hologram pattern (14) provides a uniform intensity of a light spot formed of a laser light by an optical element.