EP0321027A2
Expired / Lapsed
EP
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Method of recording information on a record carrier of the thermomagnetic tye, and device for carrying out the method
Assignee: Koninklijke Philips NV
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Filing: 1988-12-08
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Granted: —
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Expires: 2008-12-08
Abstract
Abstract When information is recorded on a record carrier (1) of the thermomagnetic type, the thermomagnetic recording layer (4) is scanned by means of a magnetic field generated by a magnetic-field modulator (7). The magnetic field is modulated depending on an information signal (Vi). Moreover, the scanned portion of the record carrier (1) is at the same time locally heated by radiation pulses (10) generated by an optical scanning device (5). By means of radiation pulses (10) the record carrier is heated above a write temperature (Ts), above which temperature the magnetisation of the record carrier assumes the direction dictated by the magnetic field. A synchronising circuit (9) generates the control signal (Vm) for modulating the magnetic field and the control signal (Vr) for generating the radiation pulses, in such a way that at the end of the radiation pulses the field strength is sufficiently high for the heated area of the record carrier to be magnetised in the direction dictated by the magnetic field.
Inventors
- 👤 Johannes Hendrikus Maria Spruit
- 👤 Hendricus Franciscus Joannes Jacobus Van Tongeren
- 👤 Piet Frans Bongers
- 👤 Bernardus Antonius Johannus Jacobs
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 15:02
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10502; G11B11/1053; G11B11/10504; G11B11/1051; G11B11/10513; G11B13/00; G11B13/04; G11B13/045
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
171 words
A method of recording information on a record carrier having a recording layer of a thermomagnetic type, a pattern of magnetic domains having a first and second direction of magnetisation being formed in the recording layer by scanning the recording layer with a magnetic field which is modulated depending on an information signal and being at the same time, by applying radiation, heating the recording layer locally in the area being scanned to a temperature above a write temperature, above which temperature the magnetisation of the recording layer assumes a direction dictated by the magnetic field, characterized in that the radiation is applied as radiation pulses, a minimum time interval being maintained between the instants at which the direction of the magnetic field is reversed and the instants at which the radiation pulses terminate, in such a way that at the end of the radiation pulse the magnetic field is sufficiently strong for the portion heated above the write temperature to be magnetised in the direction dictated by the magnetic field.
Claim 2
Independent Claim
171 words
A method of recording information on a record carrier having a recording layer of a thermomagnetic type, a pattern of magnetic domains having a first and second direction of magnetisation being formed in the recording layer by scanning the recording layer with a magnetic field which is modulated depending on an information signal and being at the same time, by applying radiation, heating the recording layer locally in the area being scanned to a temperature above a write temperature, above which temperature the magnetisation of the recording layer assumes a direction dictated by the magnetic field, characterized in that the radiation is applied as radiation pulses, a minimum time interval being maintained between the instants at which the direction of the magnetic field is reversed and the instants at which the radiation pulses terminate, in such a way that at the end of the radiation pulse the magnetic field is sufficiently strong for the portion heated above the write temperature to be magnetised in the direction dictated by the magnetic field.
Claim 3
Dependent Claim
25 words
A method as claimed in Claim 1, characterized in that the duration of the radiation pulses is short relative to the period the radiation pulses.
Claim 4
Dependent Claim
46 words
A method as claimed in Claim 1 or 2, characterized in that the information signal is a digital signal of a specific bit rate, the frequency of the radiation pulses being equal to n times the bit rate, n being greater than or equal to 1.
Claim 5
Dependent Claim
13 words
A method as claimed in Claim 3, characterized in that n is 1.
Claim 6
Independent Claim
40 words
A method as claimed in any one of the preceding Claims, characterized in that the instant at which the direction of the magnetic field is reversed is situated substantially halfway between the instants at which two successive radiation pulses end.
Claim 7
Dependent Claim
129 words
A magneto-optical recording device for carrying out the method as claimed in any one of the preceding Claims, which recording device comprises a magnetic-field modulator for scanning the recording layer of the record carrier with a magnetic field which is modulated depending on an information signal, an optical system for applying, by means of a radiation beam, radiation energy to that portion of the recording layer which is scanned by the magnetic-field modulator in order to locally heat the scanned portion, characterized in that the recording device comprises means for modulating the radiation-beam intensity so as to generate radiation pulses, and synchronising means for maintaining a specific minimum time interval between the instants of reversal of the direction of the magnetic field and the ends of the radiation pulses.
Claim 8
Dependent Claim
30 words
A recording device as claimed in Claim 6, characterized in that the synchronising means comprises means for maintaining a specific phase relationship between the magnetic-field modulation and the radiation-beam modulation.
Claim 9
Dependent Claim
40 words
A recording device as claimed in Claim 6 or 7, characterized in that the recording device is adapted to generate radiation pulses of a duration which is short relative to the length of the time intervals between the radiation pulses.
Claim 10
Dependent Claim
56 words
A recording device as claimed in Claim 6, 7 or 8, characterized in that the information signal is a digital signal of a specific bit rate, the synchronising means being adapted to generate a periodic signal of a frequency equal to n times the bit rate, n being an integer greater than or equal to 1.
Claim 11
Dependent Claim
14 words
A recording device as claimed in Claim 8, characterized in that n is 1.
Claim 12
Dependent Claim
57 words
A recording device as claimed in Claim 7, 8, 9 or 10, characterized in that the synchronising means comprise a phase detector for determining the phase difference and means for adapting the periodic signal depending on the phase difference thus detected in such a way that the phase difference is maintained substantially equal to a specified value.
Claim 13
Dependent Claim
62 words
A recording device as claimed in any one of the Claims 6 to 11, characterized in that the synchronising means are adapted to maintain such a time interval between the ends of the radiation pulses and the instants at which the magnetic-field direction is reversed that the instants of reversal are situated substantially halfway between the ends of two successive radiation pulses.
References Cited (Backward Citations)
No citation records indexed.
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