an optical pick - up apparatus has a first light source , a second light source , and an optical system including an objective lens . an optical functional surface of the objective lens is divided into at least first and second concentric optical functional regions . the second functional region is provided with a diffractive structure to correct a spherical aberration of a converged light spot on an information recording plane to be regulated in a range where reproduction and / or recording information for a first optical information recording medium can be conducted when the refractive index of the optical element and the wavelength of the first light source vary due to a change of the working temperature of the optical system .