Device for optically scanning a recording medium by focusing the best focus or the paraxial focus to the information layer
AssigneeU.S. Philips Corporation
InventorsJosephus J. M. Braat, Igolt P. D. Ubbens, James H. Coombs, Jacob Sonneveld, Jacobus P. C. Kroon, Petrus T. Jutte
Life of this patent
Estimating the term…
Abstract
An optical scanning device can scan two types of record carriers each having a transparent layer with a different thickness, in which a radiation beam scans an information layer of the record carrier through the transparent layer. When scanning a first type of record carrier the best focus of a scanning radiation beam is positioned on the information layer and when scanning a second type of record carrier the paraxial focus of the radiation beam is positioned on the information layer.
Claims21
Optical scanning device for scanning a first type of record carrier having a first information layer and a first transparent layer of a first thickness and for scanning 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, comprising a radiation source for generating a radiation beam and an objective lens designed for converging the radiation beam to a focus, said focus comprising a best focus and a paraxial focus, characterized in that the device comprises means for positioning the best focus of the radiation beam substantially on the first information layer and the paraxial focus of said radiation beam substantially on the second information layer.
Method for optically scanning a first type of record carrier having a first information layer and a first transparent layer of a first thickness and 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, comprising the step of converging a radiation beam by means of an objective lens through the first transparent layer to a best focus substantially on the first information layer when scanning a record carrier of the first type, and the step of converging the radiation beam by means of the objective lens through the second transparent layer to a paraxial focus substantially on the second information layer when scanning a record carrier of the second type.
Dependencies are inferred from the claim text.