US3739394A
Expired / Lapsed
US
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Method and apparatus for storing information in a magneto-optical memory
Assignee: Siemens AG
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Filing: 1971-08-26
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Granted: 1973-06-12
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Expires: 1991-08-26
Abstract
Abstract The present invention is directed to a method and apparatus for recording information in a magneto-optical memory and for retrieving the information therefrom. The method comprises preparing a storage medium of the memory by applying a magnetic field of one polarity to the storage medium, heating the storage medium to a temperature above the Curie temperature to enable the induced magnetism therein to be in a direction according to the polarity of the magnetic field and maintaining the magnetic field as the storage medium cools below the Curie temperature. To record information on the medium, discrete portions of the medium have the direction of magnetism switched which is accomplished by applying a second magnetic field of a different polarity and selectively heating the discrete portions above the Curie temperature to enable switching of the direction of magnetism in the heated portions of the storage medium. To retrieve information from the memory, the medium is scanned with a linearly polarized light beam whose polarization is changed by the switched direction of magnetism which changes in polarization are converted by an analyzer to an intensity modulated light beam detected by a light detecting device which converts the signal into electrical signals. To prepare the storage medium for recording and to record, a laser is utilized to heat the medium above the Curie temperature and during recording the beam is intensity modulated in accordance to the information to be recorded and scanned on the medium in a line by line manner.
Inventors
- 👤 M Becker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 23:01
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10532; G11B11/10534; G11B11/10536; G11B11/10582
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
280 words
A method of recording information in a magneto-optical memory having a storage medium with a residual magnetism whose direction of magnetism depends upon the polarity of a magnetic field application to the medium as the medium is heated to a temperature above the Curie temperature of the medium and cooled therebelow, said storage medium having a bright-dark raster disposed on a surface thereof, the method comprising: preparing the storage medium for recording by applying a magnetic field of one polarity thereto and heating the storage medium while subject to the magnetic field to a temperature above the Curie temperature by the application of a light beam to impose the direction of magnetism to the storage medium in accordance to the polarity of the magnetic field; and then recording information on the storage medium by switching the direction of magnetism in discrete portions of the medium in accordance with the information to be recorded the step of recording comprising: applying a magnetic field of a second polarity different to said one polarity, providing a light beam and separating the light beam into two portions, and applying one portion of the light beam to the storage medium with a line by line scan and the other portion of the light beam on the raster to determine the portion of the line by line scan, while said medium is subject to said magnetic field of said second polarity, said one portion of the light beam being modulated in intensity in accordance with the information to be recorded to selectively heat the discrete portions of the storage medium above the Curie temperature to enable switching of the direction of magnetism of said discrete portion.
Claim 2
Independent Claim
280 words
A method of recording information in a magneto-optical memory having a storage medium with a residual magnetism whose direction of magnetism depends upon the polarity of a magnetic field application to the medium as the medium is heated to a temperature above the Curie temperature of the medium and cooled therebelow, said storage medium having a bright-dark raster disposed on a surface thereof, the method comprising: preparing the storage medium for recording by applying a magnetic field of one polarity thereto and heating the storage medium while subject to the magnetic field to a temperature above the Curie temperature by the application of a light beam to impose the direction of magnetism to the storage medium in accordance to the polarity of the magnetic field; and then recording information on the storage medium by switching the direction of magnetism in discrete portions of the medium in accordance with the information to be recorded the step of recording comprising: applying a magnetic field of a second polarity different to said one polarity, providing a light beam and separating the light beam into two portions, and applying one portion of the light beam to the storage medium with a line by line scan and the other portion of the light beam on the raster to determine the portion of the line by line scan, while said medium is subject to said magnetic field of said second polarity, said one portion of the light beam being modulated in intensity in accordance with the information to be recorded to selectively heat the discrete portions of the storage medium above the Curie temperature to enable switching of the direction of magnetism of said discrete portion.
Claim 3
Dependent Claim
16 words
A method according to claim 1, wherein the modulation light beam is a pulse code modulation.
Claim 4
Dependent Claim
56 words
A method according to claim 1, wherein the step of preparing is applied to a line on the storage medium followed by the step of recording on the prepared line to minimize time loss for repoling the polarity of the field applied to the storage medium between the step of preparing and the step of recording.
Claim 5
Independent Claim
237 words
An apparatus for recording information in a magneto-optical memory having a storage medium with a residual magnetism whose direction of magnetism depends upon the polarity of a magnetic field applied to the medium as the storage medium is heated to a temperature above the Curie temperature of the medium and cooled therebelow, said storage means having a bright-dark raster provided on a surface thereof, said apparatus comprising: a laser for the production of a light beam; means comprising a modulator and a polarizer for intensity modulating the light beam in accordance for the information to be recorded; scanning means for moving the light beam relative to the storage medium in a vertical and horizontal direction to produce a line by line scanning of the storage medium; means for focusing the light beam onto the storage medium; means for applying a magnetic field of a desired polarity to the storage medium; and control means for controlling the scanning means and the modulator of the modulating means said control means including a motion pickup means for providing the respective beam position on the storage means, said motion pickup means including a partially-permeable mirror arranged in the path of the light beam prior to the polarizer for reflecting a portion of the light beam therefrom and directing the portion onto the raster of the storage medium and a light detector arranged to receive the light modulated by the bright-dark raster.
Claim 6
Independent Claim
237 words
An apparatus for recording information in a magneto-optical memory having a storage medium with a residual magnetism whose direction of magnetism depends upon the polarity of a magnetic field applied to the medium as the storage medium is heated to a temperature above the Curie temperature of the medium and cooled therebelow, said storage means having a bright-dark raster provided on a surface thereof, said apparatus comprising: a laser for the production of a light beam; means comprising a modulator and a polarizer for intensity modulating the light beam in accordance for the information to be recorded; scanning means for moving the light beam relative to the storage medium in a vertical and horizontal direction to produce a line by line scanning of the storage medium; means for focusing the light beam onto the storage medium; means for applying a magnetic field of a desired polarity to the storage medium; and control means for controlling the scanning means and the modulator of the modulating means said control means including a motion pickup means for providing the respective beam position on the storage means, said motion pickup means including a partially-permeable mirror arranged in the path of the light beam prior to the polarizer for reflecting a portion of the light beam therefrom and directing the portion onto the raster of the storage medium and a light detector arranged to receive the light modulated by the bright-dark raster.
Claim 7
Dependent Claim
30 words
An apparatus according to claim 4 characterized in the scanning means includes a continuously rotating polygon mirror for deflecting the light beam across the storage medium in a horizontal direction.
Claim 8
Dependent Claim
16 words
An apparatus according to claim 4, wherein the bright-dark raster is etched onto the storage medium.
Claim 9
Dependent Claim
56 words
An apparatus according to claim 4 which further includes means for reading information recorded on a storage medium comprising an analyzer and a light detector, said analyzer converting rotational changes in the polarized light beam imparted by the information recorded on the storage medium into a light intensity modulation which is detected by the light detector.
Claim 10
Dependent Claim
12 words
An apparatus according to claim 4, wherein the storage medium is interchangeable.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-06-11 | 1976-12-11 | 1977-06-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-06-11 | 1980-12-11 | 1981-06-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-06-11 | 1984-12-11 | 1985-06-12 | $7700.00 | Window Closed / Lapsed |