US4639907A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magneto-optical apparatus
Assignee: Sony Corp
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Filing: 1984-09-05
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Granted: 1987-01-27
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Expires: 2004-09-05
Abstract
Abstract A magneto-optical apparatus records, reads and erases information by radiating a laser beam on a magneto-optical medium which uses an amorphous material for a recording layer and which is subjected to information writing and erasure, wherein a predetermined DC signal is added to a focus error signal in the erasure mode, and the laser beam irradiates the magneto-optical medium in a defocused state.
Inventors
- 👤 Yoshio Aoki
- 👤 Yoshihiro Tsukamura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 05:53
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10532; G11B11/10534; G11B11/10536; G11B7/00; G11B7/08; G11B7/085
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
167 words
A magneto-optical recording apparatus for use with a magneto-optical medium having a first amorphous layer recording layer comprising, a laser source producing a laser beam, means for projecting said laser beam onto said magneto-optical layer and a reflected laser beam produced thereby, an objective lens through which said laser beam and said reflected laser beam pass, means for generating a focus error signal, a focusing coil mounted so as to move said objective lens normal to said magneto-optical medium in response to said focus error signal so that said laser beam is focused on said first layer of said magneto-optical medium during the recording mode of operation; a D.C. signal source, and adding means for adding said D.C. signal to said focus error signal during the erasing mode of operation so that the beam of said laser source is focused on a plane in front of said first layer of said magneto-optical medium and intelligence recorded on said first layer of said magneto-optical medium will be erased.
Claim 2
Dependent Claim
167 words
A magneto-optical recording apparatus for use with a magneto-optical medium having a first amorphous layer recording layer comprising, a laser source producing a laser beam, means for projecting said laser beam onto said magneto-optical layer and a reflected laser beam produced thereby, an objective lens through which said laser beam and said reflected laser beam pass, means for generating a focus error signal, a focusing coil mounted so as to move said objective lens normal to said magneto-optical medium in response to said focus error signal so that said laser beam is focused on said first layer of said magneto-optical medium during the recording mode of operation; a D.C. signal source, and adding means for adding said D.C. signal to said focus error signal during the erasing mode of operation so that the beam of said laser source is focused on a plane in front of said first layer of said magneto-optical medium and intelligence recorded on said first layer of said magneto-optical medium will be erased.
Claim 3
Dependent Claim
53 words
A magneto-optical recording apparatus according to claim 1 wherein a second amorphous material layer is formed on said magneto-optical medium and said beam of said laser is focused on a plane which is between said objective lens and said first amorphous layer during the erasing mode when said first amorphous layer is erased.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-01-26 | 1990-07-28 | 1991-01-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-01-26 | 1994-07-28 | 1995-01-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-01-26 | 1998-07-28 | 1999-01-27 | $7700.00 | Window Closed / Lapsed |