The optical pick-up apparatus

PROBLEM TO BE SOLVED: To avoid an increase in spherical aberration involved in a tracking operation by dispensing with a finite optical system. SOLUTION: Parallel luminous fluxes of optical beams A, B and C for a next generation DVD, DVD and CD are limited to luminous flux diameters a, b and c (a>b >c) corresponding to NA of each type by a luminous flux limiting element, wherein B is within the range of diameters b and c, and d (=0.85×c) to e (d>e>0), C is limited to the range of diameters c and d, and ≤e, and the parallel luminous fluxes are focused onto a corresponding optical recording medium signal plane by a common objective lens through a phase correcting element 13B. The objective lens is optimized so as to minimize wave front aberration of A on the signal plane of the next generation DVD. The phase correcting element 13B has phase correction areas Z1 to Z4 of a false kinoform-shaped diffraction optical structure of a staircase structure, spherical aberration correction is applied to B at Z1 and Z3, and spherical aberration correction is applied to C at Z2 and Z4. A optimizes the height of level difference of Z1 to Z4 to make the entire range of the luminous flux diameter (a) transmit while a parallel luminous flux state as it is. COPYRIGHT: (C)2007,JPO&INPIT