OPTICAL HEAD DEVICE

摘要

PURPOSE: To provide an optical head device capable of performing the recording and the reproducing of optical disks having different thichnesses of substrates. CONSTITUTION: A hologram lens 107 is designed so that the transmission light 61a (the zero-order diffracted light) also has a sufficient strength. An objective lens 4 is designed so that the converged spot of a diffraction limit can be formed on a thin optical disk having the thickness (t2) of the substrate 37 when a light beam 61 transmitted through the hologram 107 by being not diffracted is made incident on the objective lens. Moreover, the +1st-order diffracted light 64 diffracted with the hologram lens 107 is converged on an information medium 5 by the objective lens 4 and is applied with an aberration compensation so as to be converged to the diffraction limit through the substrate 37 having a thickness (t1).