US4858212A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Recording method on magnetooptical disc with laser magnetic field
Assignee: Sharp Corp
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Filing: 1988-07-20
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Granted: 1989-08-15
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Expires: 2008-07-20
Abstract
Abstract A magnetooptical disc is initialized by reversing the direction of magnetization at fixed intervals and the direction of external magnetic field applied to it is reversed for each overwrite recording by exposure to laser light.
Inventors
- 👤 Akira Takahashi
- 👤 Yoshiteru Murakami
- 👤 Michinobu Mieda
- 👤 Tomoyuki Miyake
- 👤 Kenji Ohta
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 13:54
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10502; G11B11/10517; G11B11/10519; G11B11/10515
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
130 words
A method of recording data sequentially on a magnetooptical disc by exposing said disc to laser light and applying an external magnetic field thereto, said disc having sequentially numbered bits, said method comprising the steps of initializing said disc by establishing an initial disc condition wherein the direction of magnetization in said disc is reversed from one to the next of said sequentially numbered bits, reversing the direction of said external magnetic field whenever a new data is recorded on said disc, and using a single laser beam to alternately record a data on odd-numbered ones of said bits while erasing data recorded on even-numbered ones of said bits and to record another data at even-numbered ones of said bits while erasing data recorded on odd-numbered ones of said bits.
Claim 2
Independent Claim
130 words
A method of recording data sequentially on a magnetooptical disc by exposing said disc to laser light and applying an external magnetic field thereto, said disc having sequentially numbered bits, said method comprising the steps of initializing said disc by establishing an initial disc condition wherein the direction of magnetization in said disc is reversed from one to the next of said sequentially numbered bits, reversing the direction of said external magnetic field whenever a new data is recorded on said disc, and using a single laser beam to alternately record a data on odd-numbered ones of said bits while erasing data recorded on even-numbered ones of said bits and to record another data at even-numbered ones of said bits while erasing data recorded on odd-numbered ones of said bits.
Claim 3
Dependent Claim
43 words
The method of claim 1 wherein said laser beam is a pulse with power on at those of said sequentially numbered bits where numeral 0 is to be written and off at those of said bits where numeral 1 is to be written.
References Cited (Backward Citations)
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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) | 1992-08-14 | 1993-02-13 | 1993-08-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-08-14 | 1997-02-13 | 1997-08-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-08-14 | 2001-02-13 | 2001-08-15 | $7700.00 | Window Closed / Lapsed |