OPTICAL HEAD DEVICE

摘要

PROBLEM TO BE SOLVED: To obtain an optical head device capable of performing the recording and reproducing of disks whose substrate thicknesses are different stably. SOLUTION: In an optical head device, the transmissivity or the 0-order diffraction efficiency of the part spaced away from an optical axis is lowered by a correcting hologram 122 or a correcting filter with respect to the light beam to be radiated from a light source. A light beam whose light intensity is reduced at outer side is passed through a hologram lens 107 designed so that a transmission light (the 0-order diffracted light) has also a sufficient intensity. Then, a condensed spot having a diffraction limit is formed on optical disks whose substrate thicknesses are different by the combination of the hologram lens 107 and an objective lens 4.