US4872078A
Expired / Lapsed
US
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Method and apparatus for encoding and direct overwriting of magneto-optic data
Assignee: International Business Machines Corp
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Filing: 1987-12-09
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Granted: 1989-10-03
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Expires: 2007-12-09
Abstract
Abstract Direct overwrite of data on magneto-optic medium is described. Old data is erased and new data is written during a single rotation of the media in a data storage system which includes a resonant coil for producing a high frequency alternating magnetic field interacting with laser pulses having a duration equal to a small fraction of the period of the magnetic field. Variable-length magnetic domains are formed by overlapping circular magnetic domains to provide pulse width modulation (PWM) encoding of data.
Inventors
- 👤 Ulrich G. Gerber
- 👤 Daniel Rugar
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 19:46
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10502; G11B11/10504; G11B11/1051; G11B11/10513; G11B11/10517; G11B11/10519; G11B11/10521; G11B11/10528; G11B11/10532; G11B11/10534; G11B11/10536
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
81 words
Apparatus for direct overwriting of encoded data along a track in a magneto-optic recording medium, said apparatus comprising: first means for producing a magnetic field having a continually alternating magnetic polarity near the track; and second means, coupled to the first means, for selectively heating successively overlapping magnetically polarized domains representing encoded data along the track when the instantaneous polarity of the magnetic field at said domains corresponds to the polarity of the code for the data to be recorded thereat.
Claim 2
Dependent Claim
81 words
Apparatus for direct overwriting of encoded data along a track in a magneto-optic recording medium, said apparatus comprising: first means for producing a magnetic field having a continually alternating magnetic polarity near the track; and second means, coupled to the first means, for selectively heating successively overlapping magnetically polarized domains representing encoded data along the track when the instantaneous polarity of the magnetic field at said domains corresponds to the polarity of the code for the data to be recorded thereat.
Claim 3
Dependent Claim
33 words
Apparatus as in claim 1, wherein: the magnetic polarity of the magnetic field alternates at frequency f B ; and the second means is activated at a frequency of approximately 2f B .
Claim 4
Dependent Claim
22 words
Apparatus as in claim 1, wherein the second means is activated at least once during each period of the alternating magnetic field.
Claim 5
Dependent Claim
19 words
Apparatus as in claim 1, wherein the maximum distance between successive domains of radius r is less than 2r.
Claim 6
Dependent Claim
51 words
Apparatus as in claim 2, wherein: each of said successively overlapping domains are substantially circular; and the relative velocity, v, of the track with respect to the first and second means is given approximately by the relation v≦rf B , where r is the radius of one of said overlapping domains.
Claim 7
Dependent Claim
16 words
Apparatus as in claim 4, wherein the distance between successive domains is approximately equal to r.
Claim 8
Dependent Claim
16 words
Apparatus as in claim 4, wherein the distance between successive domains is approximately equal to 0.5r.
Claim 9
Dependent Claim
25 words
Apparatus as in claim 1, wherein: the first means includes a resonant coil; and the second means includes a selectively controllable source of laser light.
Claim 10
Dependent Claim
30 words
Apparatus as in claim 1, wherein said successively overlapping domains form a series of selectively variable-length, substantially continuous, elongated magnetically polarized domains for encoding data in pulse width modulation codes.
Claim 11
Dependent Claim
27 words
Apparatus as in claim 1, wherein the encoded data represented by said elongated domains is substantially unaffected by variation in the size of said successively overlapping domains.
Claim 12
Dependent Claim
44 words
Apparatus as in claim 1, wherein: each of said successively overlapping domains are substantially circular; and the length of said elongated magnetically polarized domains along the track is substantially unaffected by variation in the diameter of each of said successively overlapping substantially circular domains.
Claim 13
Dependent Claim
26 words
Apparatus as in claim 9, wherein: the pulse width modulation code is run length limited; and the number of consecutive zeroes in said code is even.
Claim 14
Independent Claim
93 words
A method for direct overwriting of encoded data along a track in a magneto-optic recording medium, said method comprising the steps of: providing a magnetic field having alternating magnetic polarity near the track; and selectively heating successively overlapping magnetically polarized domains along the track when the instantaneous polarity of the magnetic field at said domains corresponds to the polarity of the code for the data to be recorded thereat for forming a series of selectably variable-length substantially continuous, elongated, magnetically polarized domains representing data encoded on the track in pulse width modulation codes.
Claim 15
Independent Claim
93 words
A method for direct overwriting of encoded data along a track in a magneto-optic recording medium, said method comprising the steps of: providing a magnetic field having alternating magnetic polarity near the track; and selectively heating successively overlapping magnetically polarized domains along the track when the instantaneous polarity of the magnetic field at said domains corresponds to the polarity of the code for the data to be recorded thereat for forming a series of selectably variable-length substantially continuous, elongated, magnetically polarized domains representing data encoded on the track in pulse width modulation codes.
Claim 16
Dependent Claim
50 words
The method as in claim 13, wherein: the step of providing magnetic field includes the step of alternating the polarity of the magnetic field at frequency f B ; and the step of selectively heating includes the step of selectively heating domains at a frequency of approximately 2f B .
Claim 17
Dependent Claim
30 words
The method as in claim 13, wherein the step of selectively heating includes the step of selectively heating domains at least once during each period of the alternating magnetic field.
Claim 18
Dependent Claim
54 words
The method as in claim 14, further including the steps of: successively overlapping substantially circular domains to form said elongated domains; and moving the track with respect to the magnetic field at a relative velocity, v, given approximately by the relation v≦rf B , where r is the radius of one of said domains.
Claim 19
Dependent Claim
28 words
The method as in claim 16, wherein the step of forming successive domains includes the step of forming successive domains having a distance apart of less than 2r.
Claim 20
Dependent Claim
27 words
The method as in claim 16, wherein the step of forming successive domains includes the step of forming successive domains having a distance apart of approximately r.
Claim 21
Dependent Claim
27 words
The method as in claim 16, wherein the step of forming successive domains includes the step of forming successive domains having a distance apart of approximately 0.5r.
Claim 22
Dependent Claim
28 words
The method as in claim 13, wherein the encoded data represented by said elongated domains is substantially unaffected by variation in the size of said successively overlapping domains.
Claim 23
Dependent Claim
45 words
The method as in claim 13, further including the step of: successively overlapping substantially circular domains to form said elongated domains, the length of which along the track is substantially unaffected by variation in the diameter of each of said successively overlapping, substantially circular domains.
Claim 24
Dependent Claim
34 words
The method as in claim 13, herein the data encoded in pulse width modulation code is run length limited and is constrained so that the number of consecutive zeroes in said code is even.
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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) | 1992-10-02 | 1993-04-03 | 1993-10-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-10-02 | 1997-04-03 | 1997-10-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-10-02 | 2001-04-03 | 2001-10-03 | $7700.00 | Window Closed / Lapsed |