Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1999-12-03
2003-04-08
Tran, Thang V. (Department: 2653)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S112250
Reexamination Certificate
active
06545969
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to substrate processing and optical heads for optical storage.
In an optical storage system, an optical head is used to read data from or write data to an optical recording medium. Hence, an optical head is a critical component. See, U.S. patent application Ser. No. 08/641,513 filed on May 9, 1996 (to be issued), Ser. No. 08/657,145 filed on Jun. 3, 1996,and Ser. No. 08/846,916 filed on Apr. 29, 1997. Such an optical head may be used in a near-field optical configuration by at least coupling radiation energy via evanescent fields to achieve a high areal density.
An optical head may be formed by using a composite design that has different components. In general, different components may use different materials. One embodiment of this type of composite optical head
100
is shown in
FIG. 1. A
substrate
102
has a through hole
104
for placing a lens
110
that has a spherical surface
112
and an opposing flat surface
114
for coupling radiation energy. Bond joints
106
are used to fix the sides of the lens
110
to the sidewalls of the hole
104
. An objective lens
120
is attached to the substrate
102
by, for example, bond joints
108
over the hole
104
. Hence, lenses
110
and
120
are fixed relative to each other to define an optical path that is clear of joint bonds
106
or
108
. The lens
120
receives a substantially collimated beam and focuses the beam to the lens
110
. The lens
110
then couples optical energy of the beam to and from an optical storage medium
118
located on an optical storage medium holder, e.g.a disc platter.
The lens
110
may be a solid immersion lens formed of a higher index material. The lens
110
may be a semispherical lens where the apex of the spherical surface
112
is spaced from the flat surface
114
by one radius of the curvature. Alternatively, the spacing between surfaces
112
and
144
can be greater than the radius to form a super hemispherical lens. The flat bottom surface
114
may be coplanar with an air-bearing surface
116
. The air-bearing surface
116
is preferably implemented at the base of the optical head
100
to maintain a desired focus without conventional servo optics for focusing. The flat bottom surface
114
of the lens
110
and the air-bearing surface
116
are designed to ride at a predetermined height above the optical storage medium
118
by the air bearing caused by the motion of the head
100
relative to the medium
118
, while rotating at a specific speed.
The above composite optical head
100
requires discrete bonding. Different components are bonded to the substrate
102
. Such construction can suffer certain drawbacks, such as limited sphere quality of the lens
110
due to roll lapping capability and stresses present in the bond joints
106
and
104
. The surface shape of the lens
120
is also limited to the spherical shape only. Furthermore, alignment precision is limited by the assembly precision.
SUMMARY OF THE INVENTION
The inventors recognized the above limitations and designed a monolithic construction of the optical head. The substrate and certain optical components are formed from a monolithic piece of a substantially optically transparent material.
The optical head for an optical disk drive includes a monolithic substrate formed of an optically transparent material. The substrate has a first side and a second flat side opposing the first side. The first side includes a central region that has a curved surface to produce a lensing effect, and a peripheral region. The second flat side has a central portion opposing the curved surface to couple radiation from and to the curved surface through the substrate. The second flat side also has a peripheral portion opposing the peripheral region of the first side.
A contour of the curved surface and spacing between an apex of the curved surface and the second flat side are selected to produce optical numerical apertures at the second side greater than unity. The peripheral portion of the second flat side and the peripheral region of the first side are sufficiently large to allow the flat surface to produce an air-bearing force to suspend the substrate above a rotating disk at a predetermined speed.
A method of manufacturing a lens array having multiple monolithic optical heads is also disclosed. The method includes providing a transparent wafer substrate having multiple dice, positioning a cutting tool above a particular die on the substrate, and rotating the tool at relatively high speed. The tool is then plunged into the substrate and the force is controlled to produce a desired shape for a lens. The cutting tool is repositioned above a next die on the substrate and the above steps are repeated if necessary.
REFERENCES:
patent: 5150338 (1992-09-01), Birecki et al.
patent: 5615203 (1997-03-01), Fukakusa
patent: 5881042 (1999-03-01), Knight
patent: 6243350 (2001-06-01), Knight et al.
patent: 6324149 (2001-11-01), Mifune et al.
patent: 0951015 (1999-10-01), None
patent: WO 97/39445 (1997-10-01), None
patent: WO97/41556 (1997-11-01), None
patent: WO99/16063 (1999-04-01), None
Berg John
Buswell David
Ritter John
Terastor Corporation
Tran Thang V.
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