Patent ID: 8472301
Filing Date: 2013-06-25
Classification: G02B,G11B

Abstract:
1. An optical pickup device comprising: a first light source emitting a first light flux with a wavelength λ1 (375 nm≦λ1≦435 nm), a second light flux emitting a second light flux with a wavelength λ2 (λ1<λ2), and an objective optical element, a collimation lens, wherein the optical pickup device records and/or produces information by converging the first light flux onto an information recording surface of a first optical disc comprising a protective layer with a thickness t1 and converging the second light flux onto an information recording surface of a second optical disc comprising a protective layer with a thickness t2 (t1<t2) using the objective optical element, the objective optical element is a single lens and comprises a central area including an optical axis and a peripheral area arranged around the central area, a central-area diffractive structure is arranged in the central area, the first light flux which has passed through the central area is converged on the information recording surface of the first optical disc so that information can be recorded and/or reproduced, the second light flux which has passed through the central area is converged on the information recording surface of the second optical disc so that information can be recorded and/or reproduced, the first light flux which has passed through the peripheral area is converged on the information recording surface of the first optical disc so that information can be recorded and/or reproduced, the second light flux which has passed through the peripheral area is not converged on the information recording surface of the second optical disc so that information can be recorded and/or reproduced, the objective optical element satisfies the following expressions, where SA3(λ11), SA5(λ11), SA3(λ12), and SA5(λ12) are third-order spherical aberrations in units of λ rms and fifth-order spherical aberrations in units of λ rms obtained when light fluxes with two different wavelengths λ11 and λ12 which are within the range of the wavelength λ1 and satisfy λ11<λ12 and λ12−λ11=5 nm enter the objective optical element and wavefront aberrations are measured, and the collimation lens is a single lens, the first optical disc is an optical disc comprising a plurality of information recording surfaces, the collimation lens moves in the direction of the optical axis so that the spherical aberrations corresponding to wavelength fluctuation of first light source and the spherical aberrations corresponding to wavelength fluctuation and the spherical aberrations corresponding to recording and/or reproducing an optical disc comprising a plurality of information recording surfaces are corrected: where ΔSA3=|SA3(Δ12)−SA3(Δ11)| and