Optical pick-up apparatus and objective lens for the optical pick-up apparatus
AssigneeKonica Corporation
InventorKatsuya Sakamoto
Life of this patent
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Abstract
An optical pick-up apparatus has a first light source, a second light source, and an optical system including an objective lens. An optical functional surface of the objective lens is divided into at least first and second concentric optical functional regions. The second functional region is provided with a diffractive structure to correct a spherical aberration of a converged light spot on an information recording plane to be regulated in a range where reproduction and/or recording information for a first optical information recording medium can be conducted when the refractive index of the optical element and the wavelength of the first light source vary due to a change of the working temperature of the optical system.
Claims10
An optical pick-up apparatus for conducting recording and/or reproduction information for a plurality of optical information recording mediums having respective protective base boards different in thickness, comprising:
- a first light source having a wavelength of λ1 for conducting reproduction and/or recording information for a first optical information recording medium including a protective substrate having a thickness t1;
- a second light source having a wavelength of λ2 (λ1<λ2) for conducting reproduction and/or recording information for a second optical information recording medium including a protective substrate having a thickness t2 (t1<t2);
- an optical system to focus a light flux from the first and second light sources on an information recording surface through an optical element including an objective lens,
- wherein an optical functional surface of the objective lens is divided into at least two concentric optical functional regions having a center on an optical axis so that a light flux having passed through a first region including the optical axis is used for recording and/or reproduction information for both of the first and second optical information recording mediums, and a light flux having passed through a second region positioned around the first region is used mainly for recording and/or reproduction information for the first optical information recording medium, and
- wherein the second region is provided with a diffractive structure to correct a spherical aberration of a converged light spot on an information recording plane to be regulated in a range where reproduction and/or recording information for the first optical information recording medium can be conducted when the refractive index of the optical element and the wavelength of the first light source vary due to a change of the working temperature of the optical system.
An objective lens for use in an optical pick-up apparatus for conducting recording and/or reproduction information for a plurality of optical information recording mediums having respective protective base boards different in thickness, wherein the optical pick-up apparatus is provided with a first light source having a wavelength of λ1 for conducting reproduction and/or recording information for a first optical information recording medium including a protective substrate having a thickness t1;
- a second light source having a wavelength of λ2 (λ1<λ2) for conducting reproduction and/or recording information for a second optical information recording medium including a protective substrate having a thickness t2 (t1<t2);
- and an optical system to focus a light flux from the first and second light sources on an information recording surface through an optical element including an objective lens, the objective lens comprising:
- an optical functional surface divided into at least two concentric optical functional regions having a center on an optical axis so that a light flux having passed through a first region including the optical axis is used for recording and/or reproduction information for both of the first and second optical information recording mediums, and a light flux having passed through a second region positioned around the first region is used mainly for recording and/or reproduction information for the first optical information recording medium, and
- a diffractive structure provided on the second region and to correct a spherical aberration of a converged light spot on an information recording plane to be regulated in a range where reproduction and/or recording information for the first optical information recording medium can be conducted when the refractive index of the optical element and the wavelength of the first light source vary due to a change of the working temperature of the optical system.
Dependencies are inferred from the claim text.