US 5,708,648 AGranted

Optical head apparatus including light focusing and refocusing lens systems

AssigneeNEC Corporation

InventorAkitomo Ohba

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Abstract

An optical head apparatus includes a light source, an objective lens, a beam splitter, a refocusing lens, a pinhole, and a photodetector. The objective lens and the beam splitter focus light emitted from the light source on an information recording medium. The objective lens, the beam splitter, and the refocusing lens refocus light reflected by the information recording medium and have a light-receiving numerical aperture which is larger than a light-focusing numerical aperture of the objective lens. The pinhole extracts only a central portion of light focused by the objective lens, the beam splitter, and the refocusing lens. The photodetector receives and detects light extracted by the pinhole.

Claims10

Dependent claims

An optical head apparatus comprising:

a light source,
a focusing lens system for focusing light emitted from said light source on an information recording medium,
a refocusing lens system for refocusing light reflected by the information recording medium, said refocusing lens system having a light-receiving numerical aperture which is larger than a light-focusing numerical aperture of said focusing lens system,
light-extracting means for extracting only a central portion of light focused by said refocusing lens system, and
photodetecting means for receiving and detecting light extracted by said light-extracting means,
said optical head apparatus further comprising aperture limiting means for shielding a peripheral portion of light that has passed through said light-extracting means and been diffracted and scattered, so that said photodetecting means receives and detects light that has passed through said aperture limiting means.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/651,300Filed 22 May 1996
Priority: JP 7-13397931 May 1995
Granted: 13 Jan 1998
Term ends: Not estimatedThe source records don’t support an estimate.

Classification3 codes

G11B 7/1372
Means for guiding the beam from the source to the record carrier or from the record carrier to the detector: lenses
G11B 7/1381
Means for guiding the beam from the source to the record carrier or from the record carrier to the detector: non-lens elements for altering the…
G11B
Information storage based on relative movement between record carrier and transducer

Family

No related US applications are recorded in the indexed filing history.

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