Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1999-09-22
2001-10-02
Hudspeth, David (Department: 2651)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S044230, C369S044140
Reexamination Certificate
active
06298026
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to magneto-optical head apparatuses recording/reproducing a signal to/from a magneto-optical recording medium using a laser beam and magnetic field. The present invention more particularly relates to a magneto-optical head apparatus capable of alleviating the problem of tilt when tilt is caused to the magneto-optical recording medium.
2. Description of the Background Art
A magneto-optical recording medium is known as a rewritable recording medium with a large recording capacity and high reliability, and has come into practical use as a computer memory or the like. Recently, a magneto-optical recording medium having a recording capacity of 6.0 Gbytes has been developed as an AS-MO (Advanced Storage Magneto Optical disk) standard, and will soon be come into practical use. Reproduction of a signal from such magneto-optical recording medium with high recording density is performed as follows. A magnetic domain of a recording layer of the magneto-optical recording medium is transferred to a reproduction layer, and a detection window is formed in the reproduction layer such that only the transferred magnetic domain is detected. Thus, the transferred magnetic domain is detected from the detection window. This method is called MSR Magnetically induced Super Resolution).
Another technology has also been developed in which an alternating magnetic field is applied in reproducing a signal from a magneto-optical recording medium, and a magnetic domain of a recording layer is transferred and enlarged to a reproduction layer by a laser beam and the alternating field. This is called a magnetic domain expansion readout technology. A magneto-optical recording medium capable of recording and/or reproducing a signal of 14 Gbytes has been proposed with use of this technology.
A magneto-optical head in which an evanescent light is used for recording/reproducing a signal to/from a magneto-optical recording medium with high density is disclosed in
NIEKKEI ELECTRONICS ASIA
, August 1997, pp.46-51. The evanescent light is produced as follows. Referring to
FIG. 1A
, a laser beam is collected by an objective lens
120
, directed to an SIL (Solid Immersion Lens)
121
onto a point
123
at an end face of SIL
121
, and then emitted from point
123
. As the laser beam must be collectively directed to point
123
to produce the evanescent light, objective lens
120
and SIL
121
are integrally supported by a base
122
. To direct the evanescent light to an optical disk, a distance between SIL
121
and the optical disk must not exceed 200 nm. Thus, a flying head has been proposed which allows SIL
121
to fly as the optical disk rotates at a prescribed rate.
However, use of the flying head is associated with the following problem. More specifically, if tilt is caused to the optical disk, SIL
121
also tilts with the optical disk, as shown in FIG.
1
B. As a result, objective lens
120
that is supported integrally with SIL
121
also tilts. Then, an optical axis of the laser beam directed to objective lens
120
is considerably displaced from that of objective lens
120
, thereby causing a focal point at point
124
rather than at proper point
123
.
As described above, the use of the proposed flying head does not enable accurate recording or reproduction of the signal since the laser beam is not collected at the proper point when there is a problem of tilt.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a magneto-optical head apparatus capable of accurately recording or reproducing a signal even when tilt is caused to an optical disk by alleviating the problem of the tilt.
The magneto-optical head according to the present invention includes a solid immersion lens, objective lens and optical member. The solid immersion lens has an end face opposite to a magneto-optical recording medium. The objective lens is provided on the side of a hemispherical surface of the solid immersion lens, and has the same optical axis as the solid immersion lens and a focal point positioned on the end face of the solid immersion lens. The optical member is provided on the opposite side of the solid immersion lens of the objective lens.
Thus, even when tilt is caused to the magneto-optical recording medium and the solid immersion lens and objective lens are also tilted, the optical member can refract the laser beam in a direction in which the optical axis of the laser beam comes closer to that of the objective lens, depending on the amount of the tilt. Therefore, the problem of the tilt is alleviated.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5729393 (1998-03-01), Lee et al.
patent: 5883872 (1999-03-01), Kino
patent: 5917788 (1999-06-01), Mowry
patent: 5963532 (1999-10-01), Hajjar
patent: 6104687 (2000-08-01), Lee et al.
patent: 10-162443 (1998-06-01), None
US HDD Makers Turn to 10-Gbit/InCh2Near Field Record; Nikkei Electronics Asia, Aug. 1997, pp. 46-51.
Mitani Kenichiro
Suzuki Yoshihisa
Tanaka Sayoko
Armstrong Westerman Hattori McLeland & Naughton LLP
Chu Kim-Kwok
Hudspeth David
Sanyo Electric Co,. Ltd.
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