Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
2002-05-22
2004-09-28
Korzuch, William (Department: 2653)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C369S283000, C369S288000, C369S112240, C428S064100, C428S690000
Reexamination Certificate
active
06798732
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a near-field optical storage medium and an optical data storage system having a focusing optical system, and more particularly, to an optical storage medium which is used together with an optical pickup having a near-field focusing optical system such as a solid immersion optical system or a solid immersion lens, and a near-field optical data storage system for performing writing and/or reading of information with respect to the optical storage medium.
2. Description of the Related Art
In an optical data storage system, an optical pickup having a solid immersion optical system or solid immersion lens performs writing and/or reading of information with respect to the optical data storage medium, using a near-field formed between the solid immersion optical system or solid immersion lens and the optical data storage medium.
FIGS. 1 and 2
show an existing optical disc used as an optical data storage medium, in which
FIG. 1
shows that an existing optical disc is used together with the optical data storage system having a catadioptric solid immersion optical system, and
FIG. 2
shows that an existing optical disc is used together with an optical data storage system having a refractive type solid immersion lens.
In
FIG. 1
, a light beam
1
emitted from a light transmission and reception portion
10
is reflected by a reflective mirror
12
and incident to a catadioptric solid immersion optical system
14
. A slider
16
supporting the solid immersion optical system
14
aerodynamically raises the solid immersion optical system
14
aerodynamically through an air bearing generated by a relative movement between an optical storage medium
18
such as an optical disc and the slider
16
. As a result, an air gap is formed between the solid immersion optical system
14
and a protective layer
183
of the optical storage medium
18
. An interval of the air gap, that is, a distance between the opposing surfaces of the solid immersion optical system
14
and the optical storage medium
18
, is maintained for example within one wavelength of light used. It is preferable that it is maintained much smaller than one wavelength of the used light. The catadioptric solid immersion optical system
14
refracts and reflects the light beam
1
incident from the reflective mirror
12
, and forms a beam spot focused on its surface opposing the optical storage medium
18
. The beam spot forms a near field in the air gap between the solid immersion optical system
14
and the surface of the optical storage medium
18
.
The optical data storage system shown in
FIG. 2
includes a focusing objective lens
24
and a refractive solid immersion lens
26
, instead of the catadioptric solid immersion optical system
14
shown in
FIG. 1. A
light transmission and reception portion
20
emits a light beam
1
having an optimized diameter for the objective lens
24
. A reflective mirror
22
reflects the light beam
1
emitted from the light transmission and reception portion
20
toward the objective lens
24
. The objective lens
24
focuses the light beam
1
incident from the reflective mirror
22
on the solid immersion lens
26
. The beam spot focused on the solid immersion lens
26
forms a near field between a surface of the solid immersion lens
26
opposing the optical storage medium
18
and a protective layer
183
in the optical storage medium
18
. The objective lens
24
and the solid immersion lens
26
are supported by a slider
28
. Like the slider
16
shown in
FIG. 1
, the slider
28
aerodynamically raises the solid immersion lens
26
and forms an air gap having an interval within one wavelength of light used between the solid immersion lens
26
and the optical storage medium
18
.
In the optical data storage system shown in
FIG. 1
or
2
, a beam spot is formed in a near field generating portion being a predetermined position on the surface of the solid immersion optical system
14
or the solid immersion lens
26
which opposes the optical storage medium
18
. In general, the system shown in
FIG. 1
or
2
uses a fine beam spot corresponding to a numerical aperture (NA) of at least one for writing or reading information with respect to the optical storage medium
18
. In the case that the used light has a wavelength &lgr; of 650 nm, a light beam which forms a beam spot on the near field generating portion passes an air gap of an interval of approximately 110 nm and a protective layer
183
of 70-90 nm thick, and is transferred to a recording layer of the optical storage medium
18
. The recording layer is disposed between the protective layer
183
and a substrate
181
of the optical storage medium
18
. The light beam reflected from the recording layer transmits through the protective layer
183
and the air gap and is transferred to the solid immersion optical system
14
or the solid immersion lens
26
.
Generally, according to the refraction and total reflection laws, the light contributed to a large numerical aperture is totally reflected from the emergence surface of the solid immersion optical system
14
or the solid immersion lens
26
, that is, the near field generating portion being an optical transmitting surface adjacent to the optical storage medium
18
. Therefore, in the case that the interval of the air gap is larger than the wavelength &lgr; of the Lised light, the optical storage medium
18
is positioned in the portion beyond the near field. Thus, the light contributed to the large numerical aperture does not contribute to formation of the beam spot on the optical storage medium
18
. In other words, the numerical aperture of the light beam contributed to the formation of the beam spot on the optical storage medium
18
becomes smaller than “1”, while passing through the air gap. As a result, a spot size of the light beam focused on the optical storage medium
18
with the light traveling through the air gap having an interval larger than the wavelength of the used light, becomes larger than a size of the beam spot formed on the near field generating portion of the solid immersion optical system
14
or the solid immersion lens
26
. However, in the case that an interval of the air gap is sufficiently smaller than one wavelength of the used light, preferably &lgr;/4, the spot size of the light beam incident to the optical storage medium
18
is close to the size of the beam spot formed in the near field generating portion. Therefore, under this condition, the optical data storage system shown in
FIG. 1
or
2
can write or read information at high density with respect to the recording layer of the optical storage medium
18
, using the solid immersion optical system
14
or the solid immersion lens
26
.
FIG. 3
shows the near field generating portion between the surface of the solid immersion optical system
14
or the solid immersion lens
26
and the protective layer
183
of the optical storage medium
18
. The interval SRD from the surface of the solid immersion optical system
14
or the solid immersion lens
26
opposing the optical storage medium
18
to the protective layer
183
, more accurately, to the recording layer, becomes smaller than one wavelength of the used light, and the recording layer in the optical storage medium
18
is positioned within the distance providing a near field effect.
An example of an existing optical disc is disclosed in U.S. Pat. No. 5,470,627. In the case that the above existing optical disc is for example a magnetooptical disc, the disc includes a reflective layer, a first dielectric layer, a recording layer, and a second dielectric layer which are disposed on a conventional substrate in sequence. The reflective layer is made of metal such as an aluminum alloy having a 500-1000 Å thickness. The first dielectric layer is made of aluminum nitride or silicon nitride having a 150-400 Å thickness. The recording layer is made of rare-earth transition-metal alloy such as TbFeCo having a 150-500 Å thickness. Finally, th
Cho Kun-Ho
Hwang In-Oh
Jung Seung-Tae
Kim Yoon-Gi
Lee Chul-Woo
Chu Kim-Kwok
Korzuch William
Samsung Electronics Co,. Ltd.
Staas & Halsey , LLP
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