US 5,400,306 AGranted

Differential detection assembly for data retrieval from a data storage disk

AssigneeHewlett-Packard Company

InventorBernard W. Bell, Jr.

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Abstract

An optical assembly for detecting a light beam returning from an optical storage media and generating a signal representative of the information stored on the storage media wherein the optical assembly includes a first photodetector that is positioned in the path of the returning light beam at a predetermined angle, so that p polarized light contained in the light beam will be absorbed by the first photodetector and s polarized light will be reflected and redirected toward a second photodetector, which is positioned in the path of the redirected s polarized light and perpendicular to the path of the s polarized light, such that substantially all of the s polarized light is absorbed by the second photodetector and the photocurrents produced by the two photodetectors are differenced to produce a signal representative of the information stored on the storage disk.

Claims19

Dependent claims

An optical assembly for detecting a light beam returning from an optical storage media and generating a signal representative of the information contained therein, comprising:

a first detector means for detecting a first polarization state of said returning light beam, said first detector means being optically coupled to said returning light beam such that said returning light beam impinges a surface of said first detector means at a predetermined angle of incidence, such that light of said first polarization state of said light beam is substantially absorbed by said first detector means and light of a second polarization is substantially reflected by said surface of said first detector means, said first detector means producing a photocurrent having a magnitude proportional to the light absorbed by the first detector means;
a second detector means for detecting a second polarization state of said light beam, said second polarization state being orthogonal to said first polarization state, said second detector means being optically coupled to said first detector means, wherein said first detector means and said second detector means are not coplanar, wherein light of said second polarization state that is reflected by said surface of said first detector means directly impinges a surface of said second detector means and is substantially absorbed by said second detector means, said second detector means producing a photocurrent having a magnitude proportional to the light absorbed by said second detector means.

A method for differentially detecting data stored on a magneto-optical media, wherein a beam of light is focused onto said media at desired points, comprising the steps of:

(a) receiving light reflected from said media at said desired points, wherein said light includes polarized components contained in first and second planes;
and
(b) detecting data represented by said reflected light, said detection comprising the steps of receiving light of a first polarized state and reflecting light of a second polarized state from said reflected light with a first detector means and converting the received light of said first polarized state into a first electronic signal and directly receiving the light of said second polarized state reflected by said first detector means with a second detector means and converting said light of said second polarized state into a second electronic signal, wherein said first detector means and said second detector means are not coplanar, wherein said first detector means is positioned at an approximately 70 degree angle of incidence to the light reflected from said media, wherein said second detector means is positioned approximately perpendicular to the path of the light reflected from said first detector means.

Dependencies are inferred from the claim text.