EP0243656A2
Expired / Lapsed
EP
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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: 1987-03-20
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Granted: —
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Expires: 2007-03-20
Abstract
Abstract Old data is erased and new data is written during a single rotation of the media (10) in a data storage system which includes a resonant coil (14) for producing a high frequency alternating magnetic field interacting with laser pulses (16) 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 Gerhard Gerber
- 👤 Daniel Ruger
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 16:51
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: 25
Claim 1
Independent Claim
79 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 alternating magnetic polarity near the track; and second means, coupled to the first means, for selectively heating successively overlapping magnetically polarised 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
79 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 alternating magnetic polarity near the track; and second means, coupled to the first means, for selectively heating successively overlapping magnetically polarised 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
34 words
Apparatus as in claim 1, wherein the magnetic polarity of the magnetic field alternates at frequency f B ; and the second means may be activated at a frequency of approximately 2f B .
Claim 4
Dependent Claim
23 words
Apparatus as in claim 2, wherein the second means may be activated at least once during each period of the alternating magnetic field.
Claim 5
Dependent Claim
53 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 6
Dependent Claim
16 words
Apparatus as in claim 4, wherein the maximum distance between successive domains is less than 2r.
Claim 7
Dependent Claim
16 words
Apparatus as in claim 5, wherein the distance between successive domains is approximately equal to r.
Claim 8
Dependent Claim
16 words
Apparatus as in claim 6, 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 9, 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 10, 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
72 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 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 15
Independent Claim
72 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 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 16
Dependent Claim
50 words
A 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
A method as in claim 14, 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
A method as in claim 14 further including the steps of: forming successively overlapping, substantially circular domains; and moving the track with respect to the first and second means 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
A 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
A method as in claim 17, 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
A method as in claim 18, 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
31 words
A method as in claim 13 further including the step of forming a series of selectably variable-length substantially continuous, elongated, magnetically polarized domains for encoding data in pulse width modulation codes.
Claim 23
Dependent Claim
32 words
A method as in claim 20 further including the step of encoding data represented by said elongated domains which is substantially unaffected by variation in the size of said successively overlapping domains.
Claim 24
Dependent Claim
46 words
a method as in claim 21 further including the steps of: forming successively overlapping, substantially circular domains; forming elongated magnetically polarized domains, the length of which along the track being substantially unaffected by variation in the diameter of each of said successively overlapping, substantially circular domains.
Claim 25
Dependent Claim
40 words
A method as in claim 20 further including the steps of: encoding data in pulse width modulation code which is run length limited; and further constraining said code so that the number of consecutive zeroes in said code is even.
References Cited (Backward Citations)
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