US3775570A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magneto-optic detection system with noise cancellation
Assignee: California Institute of Technology
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Filing: 1972-02-25
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Granted: 1973-11-27
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Expires: 1992-02-25
Abstract
Abstract In a magneto-optic readout system, a polarized beam of light from a laser is subjected to the magneto-optic effect of a magnetic record medium, and then passed through an analyzer which resolves the beam into two orthogonal vector components so oriented that the two components are of equal amplitude when the angle of rotation due to the magneto-optic effect is zero. Separate photodetectors produce two output signals which are proportional to the amplitudes of the vector components. The two output signals are combined in a differential amplifier through separate logarithmic transfer circuits to produce an output signal proportional to the ratio of the two original detector signals.
Inventors
- 👤 G Lewicki
- 👤 J Guisinger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 09:23
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10532; G11B11/10502; G11B11/10515; G11B11/10541; G11B11/10543
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
278 words
A magneto-optic detection system for quantitatively determining the magnetic state of a record medium capable of assuming a stable magnetic state comprised of: means for producing a polarized beam of light, means for direcTing said polarized beam onto said medium to subject said polarized beam to the magneto-optic effect of said medium, whereby the direction of polarization of said beam is rotated by the magnetic field of said medium in that area onto which said beam is directed, to produce a rotated beam, said rotation being in a direction corresponding to the polarity of the magnetic state of said medium in said area, and the amount of rotation being proportional to the magnitude of the magnetic field in said area of said medium, means for effectively resolving said rotated beam into two orthogonal vector components, said resolving means being oriented to resolve said polarized beam into equal components when said polarized beam is not rotated by said medium, whereby components of said rotated beam are functions of the sine and cosine of the angle of rotation of said beam produced by said magneto-optic effect, separate photodetection means for detecting the amplitude of said two components of light and producing two component signals proportional to the amplitudes of said two components, means responsive to one of said component signals for obtaining a first signal proportional to the logarithm of the amplitude thereof, means responsive to the other of said component signals for obtaining a second signal proportional to the logarithm of the amplitude thereof, and means for differentially combining said first and second signals to obtain an output signal proportional to the difference between said first and second signals.
Claim 2
Dependent Claim
278 words
A magneto-optic detection system for quantitatively determining the magnetic state of a record medium capable of assuming a stable magnetic state comprised of: means for producing a polarized beam of light, means for direcTing said polarized beam onto said medium to subject said polarized beam to the magneto-optic effect of said medium, whereby the direction of polarization of said beam is rotated by the magnetic field of said medium in that area onto which said beam is directed, to produce a rotated beam, said rotation being in a direction corresponding to the polarity of the magnetic state of said medium in said area, and the amount of rotation being proportional to the magnitude of the magnetic field in said area of said medium, means for effectively resolving said rotated beam into two orthogonal vector components, said resolving means being oriented to resolve said polarized beam into equal components when said polarized beam is not rotated by said medium, whereby components of said rotated beam are functions of the sine and cosine of the angle of rotation of said beam produced by said magneto-optic effect, separate photodetection means for detecting the amplitude of said two components of light and producing two component signals proportional to the amplitudes of said two components, means responsive to one of said component signals for obtaining a first signal proportional to the logarithm of the amplitude thereof, means responsive to the other of said component signals for obtaining a second signal proportional to the logarithm of the amplitude thereof, and means for differentially combining said first and second signals to obtain an output signal proportional to the difference between said first and second signals.
Claim 3
Dependent Claim
27 words
A magneto-optic detection system as defined in claim 1 wherein said means for producing a polarized beam of light is comprised of a laser and a polarizer.
Claim 4
Dependent Claim
28 words
A magneto-optic detection system as defined in claim 2 wherein said differentially combining means is comprised of means for amplifying the difference between said first and second signals.
Claim 5
Dependent Claim
278 words
A Faraday magneto-optic detection system for quantitatively determining the magnetic state of thin film magnetic record medium capable of assuming any magnetic state between two extremes of opposite polarities comprised of: means for producing a beam of polarized light, means for transmitting said beam of polarized light through said record medium, whereby the direction of polarization of said beam is rotated by the magnetic field of said record medium in that area of said record medium through which the beam is being transmitted to produce a rotation beam, the sense of rotation corresponding to the polarity of the magnetic state of said record medium in said area, and the amount of rotation being proportional to the magnitude of the magnetic field in said area, means for effectively resolving said rotated beam into two orthogonal vecotr components, said means being oriented to resolve said polarized beam into equal components when said polarized beam is not rotated by said medium, whereby components of said rotated beam are functions of the sine and cosine of the angle of rotation of said beam produced by said magneto-optic effect, separate photodetection means for detecting the amplitude of said two components of light and producing two component signals proportional to the amplitudes of said two components, means responsive to one of said component signals for obtaining a first signal proportional to the logarithm of the amplitude thereof, means responsive to the other of said component signals for obtaining a second signal proportional to the logarithm of the amplitude thereof, and means for differentially combining said first and second signals to obtain an output signal proportional to the difference between said first and second signals.
Claim 6
Dependent Claim
278 words
A Faraday magneto-optic detection system for quantitatively determining the magnetic state of thin film magnetic record medium capable of assuming any magnetic state between two extremes of opposite polarities comprised of: means for producing a beam of polarized light, means for transmitting said beam of polarized light through said record medium, whereby the direction of polarization of said beam is rotated by the magnetic field of said record medium in that area of said record medium through which the beam is being transmitted to produce a rotation beam, the sense of rotation corresponding to the polarity of the magnetic state of said record medium in said area, and the amount of rotation being proportional to the magnitude of the magnetic field in said area, means for effectively resolving said rotated beam into two orthogonal vecotr components, said means being oriented to resolve said polarized beam into equal components when said polarized beam is not rotated by said medium, whereby components of said rotated beam are functions of the sine and cosine of the angle of rotation of said beam produced by said magneto-optic effect, separate photodetection means for detecting the amplitude of said two components of light and producing two component signals proportional to the amplitudes of said two components, means responsive to one of said component signals for obtaining a first signal proportional to the logarithm of the amplitude thereof, means responsive to the other of said component signals for obtaining a second signal proportional to the logarithm of the amplitude thereof, and means for differentially combining said first and second signals to obtain an output signal proportional to the difference between said first and second signals.
Claim 7
Dependent Claim
27 words
A magneto-optic detection system as defined in claim 4 wherein said means for producing a polarized beam of light is comprised of a laser and a polarizer.
Claim 8
Dependent Claim
28 words
A magneto-optic detection system as defined in claim 5 wherein said differentially combining means is comprised of means for amplifying the difference bEtween said first and second signals.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-11-26 | 1977-05-28 | 1977-11-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-11-26 | 1981-05-28 | 1981-11-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-11-26 | 1985-05-28 | 1985-11-27 | $7700.00 | Window Closed / Lapsed |