Optical scanning device with two-wavelength laser for HD and LD scanning
AssigneeKoninklijke Philips Electronics N.V.
InventorsPetrus Theodorus Jutte, Jacobus Maria Antonius Van Den Eerenbeemd
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Abstract
In an optical scanning device for scanning both a high-density, HD, record carrier (38) and a low-density, LD, record carrier (18), a two-wavelength diode laser (50) is used for generating the HD scanning beam and the LD scanning beam. By arranging a composite diffraction element (60) close to the diode laser (50), which element has a first diffraction structure (63), for combining the HD beam and the LD beam, and a second diffraction structure (64), which acts as a lens for either the LD beam or the HD beam only, a compact device is obtained, which is suitable for writing the LD information layer (40).
Claims12
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.
Dependencies are inferred from the claim text.