Patent ID: 7009928

Claim:
An optical scanning device for scanning, in a first mode of operation, a first type of record carrier having a first information layer and a first transparent layer of a first thickness and for scanning, in a second mode of operation, a second type of record carrier having a second information layer and a second transparent layer of a second thickness different from the first thickness, which device comprises a two-wavelength diode laser for generating a first, HD (high density scanning), radiation beam in the first mode and a second, LD (low density scanning), radiation beam in the second mode, an objective system designed for operation at a first set of conjugates to focus the HD beam on the first information layer in the first mode and for operation at a second, different, set of conjugates to focus the LD beam on the second information layer in the second mode, and a first diffraction element arranged in the radiation path between the two-wavelength diode laser and the objective system, characterized in that a second diffraction element is arranged in the radiation path between the two-wavelength diode laser and the objective system, which element has a lens function for either the LD beam or the HD beam only.