U.S. patent application number 08/992653 was filed with the patent office on 2002-06-06 for optical disk having clamp portion higher than substrate.
Invention is credited to YAMAZAKI, KENJI.
Application Number | 20020067689 08/992653 |
Document ID | / |
Family ID | 18381183 |
Filed Date | 2002-06-06 |
United States Patent
Application |
20020067689 |
Kind Code |
A1 |
YAMAZAKI, KENJI |
June 6, 2002 |
OPTICAL DISK HAVING CLAMP PORTION HIGHER THAN SUBSTRATE
Abstract
A magneto-optical disc is prepared so as to have substrates made
from polycarbonate, on which recording layers are formed so as to
serve as signal recording medium sections facing to each other via
a spacer. The magneto-optical disc is also provided with a clamp
portion formed in such a way that when the magneto-optical disc is
mounted on an optical disc recording and/or reproduction apparatus
having an objective lens with a focal distance L.sub.0, the
recording layer is positioned at a distance L.sub.1 which is equal
to a focal distance of the objective lens obtained in the substrate
via reflection.
Inventors: |
YAMAZAKI, KENJI; (KANAGAWA,
JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND
MAIER & NEUSTADT P C
1755 JEFFERSON DAVIS HIGHWAY
FOURTH FLOOR
ARLINGTON
VA
22202
US
|
Family ID: |
18381183 |
Appl. No.: |
08/992653 |
Filed: |
December 17, 1997 |
Current U.S.
Class: |
369/282 ;
G9B/11.048; G9B/23.005; G9B/7.139 |
Current CPC
Class: |
G11B 7/24 20130101; G11B
23/0035 20130101; G11B 11/10584 20130101 |
Class at
Publication: |
369/282 |
International
Class: |
G11B 007/24 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 25, 1996 |
JP |
P08346106 |
Claims
What is claimed is:
1. An optical disc onto/from which a data is written or read out by
a laser beam applied via an objective lens provided in an optical
disc recording and/or reproduction apparatus, said optical disc
comprising: a transparent substrate; a recording layer formed on
said transparent substrate; and a clamp portion provided at a
center portion of said transparent substrate; said clamp portion
and said transparent substrate having surfaces different in height
so that said recording layer plane is positioned in the vicinity of
focus position of said objective lens which is at a neutral
position.
2. An optical disc as claimed in claim 1, said disc is a
double-sided disc having two of said transparent substrates and two
of said recording layers facing to each other sandwiched by said
two transparent substrates.
3. An optical disc as claimed in claim 2, said double-sided disc
having a clamp portion with thickness identical to a normalized
optical disc thickness.
4. An optical disc having a higher recording density than a
normalized optical disc, said optical disk comprising: a
transparent substrate having a smaller thickness than said
normalized optical disc; a recording layer formed on said
transparent substrate; and a clamp portion which has a thickness
identical to that of said normalized optical disc and is rotatably
supported by a damper provided in an optical disc recording and/or
reproduction apparatus.
5. An optical disc as claimed in claim 4, wherein a distance
between a surface of said clamp portion and said recording layer is
defined so that a focus point is positioned on said recording layer
when said clamp portion is supported by said damper provided in
said optical disc recording and/or reproduction apparatus.
6. An optical disc as claimed in claim 4, said optical disc further
comprising a spacer portion having a thickness defined so that said
clamp portion has a thickness identical to that of said normalized
optical disc.
7. An optical disc as claimed in claim 6, wherein said recording
layer is formed at approximately 0.6 mm from the surface of said
transparent substrate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an optical disc such as an
optical disc and a magneto-optical disc onto/from which a data is
written or read out by an optical disc recording/reproduction
apparatus.
[0003] 2. Description of the Prior Art
[0004] An optical disc including a magneto-optical disc has been
suggested for saving a data of audio, video, or computer. This
optical disc, for example, has a recording section on a transparent
substrate and a data is recorded on this recording section.
[0005] For example, as shown in FIG. 1, a magneto-optical disc
having a signal recording plane only on one side is formed from a
disc-shaped transparent resin such as polycarbonate including: a
substrate 102 having a thickness of, for example, about 1.2 mm; a
recording layer 103 formed on the substrate 102; and a protection
layer 104 formed on the recording layer 103. This magneto-optical
disc 101 is an optical disk normalized by the International
Standard Organization (ISO) such as ISO/IEC 10089 and 13549 and
enables data writing by forming the recording layer 103 from a
magnetized film. The magneto-optical disc 101 has a clamp portion
105 at the center portion.
[0006] Moreover, an optical disc recording and/or reproduction
apparatus which enables to write or read a data onto/from the
magneto-optical disc 101 includes: a clamp 106 for holding a hub
(not depicted) provided in the clamp portion 105 of the
magneto-optical disc 101 mounted and for rotating the
magneto-optical disc 101; and an objective lens 107 for focusing a
laser beam emitted from a light source (not depicted) on the
recording layer 103. The objective lens 107 and the clamp 106 are
arranged at positions matching the configuration of the
magneto-optical disc mounted on the optical disc recording and/or
reproduction apparatus.
[0007] For example, the objective lens 107 is supported in such a
manner that it can move within a predetermined stroke for focus
servo. The objective lens 107 is positioned at a neutral position
(position X.sub.1 in FIG. 1) of the focus servo for the
magneto-optical disc 101.
[0008] The optical disc recording and/or reproduction apparatus
having such configuration writes or reads out a onto/from the
magneto-optical disc 101.
[0009] Here, the magneto-optical disc can increase a data recording
density by decreasing the thickness of the substrate as shown in
FIG. 2. It should be noted that FIG. 1 and FIG. 2 show a
single-sided type magneto-optical disc, but a so-called
double-sided magneto-optical disc is said to be able to further
increase a data recording density.
[0010] It has bee desired to provide an optical disc recording
and/or reproduction apparatus capable of recording or reproducing a
data onto/from both of the magneto-optical disc 101 having a
conventional substrate thickness of about 1.2 mm and a
magneto-optical disc 109 which is said to enable a higher recording
density by reducing a substrate thickness. That is, an apparatus
compatible for both of the discs is desired.
[0011] In this case, it is considered to design the compatible
optical disc recording and/or reproducing apparatus so as to match
with, for example, the conventional magneto-optical disc 101. For
example, if the objective lens 107 is subjected to a focus servo
when a magneto-optical disc is mounted, a data can be recording or
reproduced onto/from both of the magneto-optical discs 101 and
109.
[0012] However, if it is impossible to obtain a stroke (a distance
between X.sub.1 and X.sub.2 in FIG. 2) required for carrying out a
focus servo to the magneto-optical disc 109, the optical disc
recording and/or reproduction apparatus cannot carry out
focusing.
[0013] Furthermore, if focus is obtained at a shift limit position
of the objective lens 107 during a focus servo, focus
characteristic is deteriorated because the objective lens 107 is
not positioned at a neutral position for carrying out an
appropriate focusing.
[0014] Moreover, in order to provide a greater shift stroke for the
objective lens 107, the optical disc recording and/or reproduction
apparatus should have an additional function.
SUMMARY OF THE INVENTION
[0015] It is therefore an object of the present invention to
provide an optical disc onto which focus can be obtained with the
same objective lens even if the substrate thickness varies.
[0016] The optical disc according to the present inveniton
includes: a transparent substrate; a recording layer formed on the
transparent substrate; and a clamp portion provided at a center
portion of the transparent substrate; the clamp portion and the
transparent substrate having surfaces different in height so that
the recording layer plane is positioned in the vicinity of focus
position of the objective lens which is at a neutral position.
[0017] According to another aspect of the inveniton, the optical
disc has a higher recording density than a normalized optical disc,
and includes: a transparent substrate having a smaller thickness
than the normalized optical disc; a recording layer formed on the
transparent substrate; and a clamp portion which has a thickness
identical to that of the normalized optical disc and is rotatably
suported by a clamper provided in an optical disc recording and/or
reproduction apparatus.
[0018] The optical disc having the aforementioned configuration
enables to minimize the stroke of the objective lens provided in
the optical disc recording and/or reproduction apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 shows configuration of a conventional magneto-optical
disc.
[0020] FIG. 2 shows configuration a conventional magneto-optical
disc which requires shifting of a lens.
[0021] FIG. 3 is a cross-sectional view showing a disc rotation
drive block for rotating the aforementioned magneto-optical
disc.
[0022] FIG. 4 is a plan view of a magneto-optical disc according to
the present invention.
[0023] FIG. 5 shows configuration of the aforementioned
magneto-optical disc.
[0024] FIG. 6 shows configuration of an essential portion of the
aforementioned magneto-optical disc.
[0025] FIG. 7 shows configuration of a magneto-optical disc
according to another embodiment of the present invention.
[0026] FIG. 8 is a perspective view showing the aforementioned
magneto-optical disc contained in a disc cartridge.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] Description will now be directed to preferred embodiments of
the present invention with reference to the attached drawings.
[0028] That is, explanation will be given on a magneto-optical disc
onto/from which a data can be written or read out by applying a
laser beam through an objective lens provided in an optical disc
recording and/or reproduction apparatus.
[0029] Here, the optical disc recording and/or reproduction
apparatus is a so-called compatible optical disc recording/or
reproduction apparatus capable of writing and reading out a data
onto/from magneto-optical discs having different substrate
thicknesses, for example, a magneto-optical disc having a substrate
thickness of about 0.6 mm and a magneto-optical disc having a
substrate thickness of about 1.2 mm.
[0030] The aforementioned optical disc recording and/or
reproduction apparatus includes: a rotation drive block to be
matched with a clamp portion formed at the rotation center of the
magneto-optical disc, so as to rotate the magneto-optical disc; and
an objective lens for focusing a laser beam on a signal recording
plane of the magneto-optical disc.
[0031] The aforementioned objective lens and the clamp are arranged
in an optical disc recording and/or reproduction apparatus so as to
match with the conventional magneto-optical disc having a substrate
thickness of about 1.2 mm. More specifically, the objective lens is
positioned at a neutral position, i.e., at an intermediate position
of focus servo carried out for the magneto-optical disc having the
substrate thickness of about 1.2 mm.
[0032] The disc rotation drive block serves to rotate the
aforementioned magneto-optical discs and as shown in FIG. 3,
includes: a damper 41 formed so as to match with a hub provided on
the magneto-optical disc which will be detailed later; a spindle
shaft 42 which thrusts through and supports the damper 41; and a
spindle motor for rotating this spindle shaft 42. The damper is
formed approximately into a cylindrical shape having one end open
and has a magnet 44 formed into a ring shape at the bottom of the
damper 41. This disc rotation drive block 40 is arranged in the
optical disc recording and/or reproduction apparatus in such a
manner that the damper 41 is properly matched with the normalized
magneto-optical disc having the substrate thickness of 1.2 mm.
[0033] Hereinafter, explanation will given on a so-called
double-sided magneto-optical disk having a signal recording plane
on both sides, whereas the magneto-optical disk having the
substrate thickness of 1.2 mm will be referred to as the other type
of magneto-optical disc.
[0034] FIG. 4 is a plan view showing the aforementioned
magneto-optical disc having a substrate thickness of 0.6 mm. As
shown in FIG. 4, the magneto-optical disc has a disc shape
consisting of a recording area where a data signal is recorded; a
control track 3 positioned at the inner circumference of this
recording area for containing data such as sector length and
modulation method; and a control track 4 positioned at the inner
circumference of the recording area 2 and a control track 5
positioned at the outer circumference of the recording area 2 for
containing a data such as recording and erase conditions.
[0035] As shown in FIG. 5, the magneto-optical disc 1 having the
aforementioned control tracks 3, 4, and 5, and the recording area 2
consists of a first signal recording medium section 13 including a
substrate 11 and a recording layer 12 formed on the substrate 11
and a second signal recording medium section 14 consisting of a
substrate 11 and a recording layer 12 formed on the substrate 11.
The first signal recording medium section 13 and the second signal
recording medium section 14 are arranged with their recording
layers facing to each other, while sandwiching a spacer 15. Thus,
the magneto-optical disc 1 has a signal recording plane on both
sides.
[0036] The aforementioned substrate 11 is made from a transparent
resin material such as polycarbonate having a thickness of 0.6
mm.
[0037] The aforementioned recording layer 12 is made from a
magnetized film enabling a data write. For example, when a data is
recorded, a laser having a power adjusted for a data write is
applied from the optical disc recording and/or reproduction
apparatus and the magnetization direction is changed by the
magnetic head, thus writing a data on the recording layer 12.
[0038] The aforementioned spacer 15 is made from, for example, a
transparent resin material such as polycarbonate in the same way as
the substrate 11.
[0039] The magneto-optical disc 1 has the aforementioned clamp
portion 16 formed at the center portion. This clamp portion 16 has
an upper surface 16a formed higher than a substrate surface 11a so
that the recording layer 12 is positioned at the neutral position
when focused by the objective lens. Hereinafter, detailed
explanation will given on a forming position of this substrate
surface 11a.
[0040] As shown in FIG. 6, when the magneto-optical disc 1 is
mounted on the optical disc recording and/or reproduction
apparatus, the objective lens 51 has a natural focal distance
L.sub.0 which is changed to a distance L.sub.1 because an incident
light from the substrate surface 11a is reflected. That is, the
focal distance is changed so that the incident light is focused on
the recording layer 12 at approximately 0.6 mm from the substrate
surface 11a. In other words, the magneto-optical disc 1 is held by
the damper 41 so that the substrate surface 11a is located at a
proper position for the neutral position of the objective lens 51,
thus enabling focus on the recording layer 12. Here, the damper 41,
as has been described above, is arranged so that the clamp portion
of the aforementioned the other type of magneto-optical disc can be
properly mounted. However, the magneto-optical disc 1 is sure to be
mounted on this damper 41 by the clamp portion surface 16a
positioned at a protruding position from the substrate surface
11a.
[0041] The magneto-optical disc 1 has such a clamp portion surface
16a formed on both sides of the disc. Moreover, the magneto-optical
disc 1 adjusts a distance between the two clamp portion surfaces
16a and 16a by the thickness of the spacer 15 formed to
approximately 2.4 mm so that the distance will be identical to the
thickness of the other type of magneto-optical disc 26 which will
be detailed below.
[0042] FIG. 7 shows configuration of the other type of
magneto-optical disc having a normalized substrate thickness of 1.2
mm with a recording plane on both sides. This magneto-optical disc
includes two signal recording medium sections 24 and 25, each
consisting of a substrate 21; a recording layer 22 formed on the
substrate 21; and a protection layer 23 formed on the recording
layer 22.
[0043] As shown in FIG. 7, the aforementioned damper 41 and the
objective lens 51 are arranged to match with the other type of the
magneto-optical disc 26 so that a clamp portion 27 has a clamp
portion surface 27a forms a single plane with a substrate surface
27a without any step.
[0044] That is, the damper 41 and the objective lens 51 are
arranged in such a manner that when the other type of
magneto-optical disc 26 is mounted on the damper 41, the objective
lens 51 has a natural focal distance L.sub.0 which is changed by
reflection in the substrate 21 to a focal distance L.sub.2,
enabling to focus on the recording layer 22.
[0045] It should be noted that the other type of the
magneto-optical disc has a clamp portion surface 27a on its both
sides. Moreover, the other type of magneto-optical disc is formed
so as to have the clamp portion with a thickness of approximately
2.4 mm which is also the distance between the two substrate
surfaces 21a and 21a.
[0046] Thus, the magneto-optical disc 1 and the other type of
magneto-optical disc 26 can be focused by the objective lens 51
having an identical neutral position.
[0047] Moreover, each of the magneto-optical discs 1 and 26 is
provided with a hub which is coaxial with the clamp portion. For
example, as shown in FIG. 4 and FIG. 5, the hub is formed
approximately into a cylindrical form so that the damper 41 of the
disc rotation drive block 40 can be attached and removed to/from
the hub. That is, the hub 31 has an outer diameter which is
slightly smaller than the inner diameter of the damper 41.
Moreover, the hub 31 is provided with a magnetic metal member 32
formed into a rig shape and attached at the both ends of the hub
31. The hub 31 is also has a through hole 31a into which the
spindle shaft 42 of the disc rotation drive block 40 is
inserted.
[0048] Each of the aforementioned magneto-optical discs 1 and 26 is
surely held by the disc rotation drive block 40 via the hub formed
as described above.
[0049] Each of the magneto-optical discs 1 and 26 having the above
described configurations is rotatably contained in a disc cartridge
34 having a cartridge body 33 formed approximately into a thin
square type box. This disc cartridge 34 has: a magnetic head
advance opening 35 allowing a magnetic head of the optical disc
recording and/or reproduction apparatus to access the recording
area 2 of the magneto-optical disc contained in the cartridge body
33; a disc rotation drive block advance opening 36 allowing the
damper 41 of the disc rotation drive block 40 be mounted on the hub
31 of the magneto-optical disc 1, 26; a shutter 37 which is
slidably supported on the cartridge body 33 for covering the
magnetic head advance opening 35 and the disc rotation drive block
advance opening 36; identifier holes 38a and 38b for identifying
information of the signal recording medium sections of the
magneto-optical disc 1, 26; and a positioning hole 39 for
positioning the cartridge when inserted into the optical disc
recording and/or reproduction apparatus.
[0050] The disc cartridge 34 also serves to prevent adhesion of
dusts to the signal recording medium sections of the
magneto-optical disc 1 and 26 when contained in the disc cartridge
34. When the disc cartridge is mounted on the optical disc
recording and/or reproduction apparatus (not depicted) for
recording or reproduction, the magneto-optical disc 1 or the other
type of magneto-optical disc 26 is mounted on the disc rotation
drive block 40 as described above.
[0051] For example, when a data is to be written onto the
magneto-optical disc 1, focusing can be carried out with the
objective lens 51 whose neutral position is almost identical to the
case when the other type of magneto-optical disc 26 is mounted.
[0052] That is, the optical disc recording and/or reproduction
apparatus can obtain a sufficient stroke for focus servo from the
neutral position of the objective lens, enabling to prevent
deterioration of the focus servo characteristic.
[0053] Thus, the magneto-optical disc 1 having the clamp portion 16
can be arranged in the optical disc recording and/or reproduction
apparatus having the objective lens 51 with its focus position
adjusted for the other type of magneto-optical disc 26, without
changing the focus servo stroke. Consequently, the optical disc
recording and/or reproduction apparatus need not provide a
particular function for coping with the magneto-optical discs
having different substrate thicknesses, thus enabling to suppress
increase of the apparatus size as well as production costs.
[0054] Moreover, as focusing can be carried out at the same
position without moving the objective lens 51 according to the type
of the magneto-optical disc, this brings about a great advantage
for an optical disc recording and/or reproduction apparatus which,
for example, reads a signal recording plane of a magneto-optical
disc mounted so as to identify the type of the magneto-optical
disc.
[0055] It should be noted that the clamp portion surface 16a of the
magneto-optical disc 1 can also be formed as indented from the
surface 11a of the substrate 11. For example, this can be applied
when the magneto-optical disc 1 has a substrate thickness greater
than that of the other type of the magneto-optical disc 26.
[0056] Moreover, the magneto-optical disc 1 may have the clamp
portion 16 having the protruding portion 16b made from another
material, for example, a material having a mechanically superior
strength. In such a case, the magneto-optical disc 1 can increase
the strength against shock applied when mounting and removing the
damper 41.
[0057] Furthermore, the magneto-optical disc 1 is not limited to
the aforementioned double-sided disc but can also be applied to a
so-called single-sided disc having a signal recording plane on one
side.
[0058] The magneto-optical disc according to the present invention
has a clamp portion surface and a transparent substrate surface
which are different in height so that the recording layer plane is
at a focus position of the objective lens at a neutral position.
This enables to carry out focus servo at the same position without
changing the position of the objective lens according to
magneto-optical discs having different substrate thicknesses.
Consequently, the optical disc recording and/or reproduction
apparatus need not have a particular function for focusing on the
aforementioned magneto-optical disc.
* * * * *