Objective lens for optical disk system and optical head using the same
April 26, 2009. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesSingle optical lens with large aperture and large field Large-aperture single lens with aspherical surfaces Lens system for optical recording type disks Lens system for optical disks Objective lens system for optical reading device Aspherical single lens Single optical lense with diffraction limit converging capability and wide field angle Patent #: 4842388 InventorsAssigneeApplicationNo. 343256 filed on 04/26/1989US Classes:359/708Including a nonspherical surfaceExaminersPrimary: Dzierzynski, Paul M.Attorney, Agent or FirmForeign Patent References
International ClassG02B 013/18AbstractA lens controls the chromatic aberration of an objective lens for practical use in an optical disk system. The lens has first and second aspherical surfaces each providing a positive refractive power for focusing a light through a transparent plate and satisfies a condition: ##EQU1## where fL =focal length of the lens, dc =thickness of the transparent plate, nc =refractive index of the transparent plate, λ=center wavelength of the light, NA=numerical apperture of the lens, νL =local dispersion of the lens, and νc =local dispersion of the transparent plate. The local dispersion of each element is expressed by: ##EQU2## where n80 is refractive index at a center wavelength λ nm, nλ +5 a refractive index at λ+5 nm, and nλ -5 a refractive index at λ-5 nm. | |
