Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
2001-03-08
2004-09-21
Patel, Gautam R. (Department: 2655)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C369S047340, C369S281000, C369S286000, C710S043000, C360S072200
Reexamination Certificate
active
06795389
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a recording medium having a multilayer structure in which optically recordable and reproducible information layers are laminated, and to a recording/reproducing method and a manufacturing method for the same.
BACKGROUND ART
Conventionally, optical disks or optical cards are known as optical information recording media on which information can be recorded or reproduced optically. These recording media use a semiconductor laser as a light source, and a great deal of information can be recorded or reproduced by irradiating the recording media with light that is finely focused by a lens.
At present, there is much research on the above recording media to improve their recording capacities. For example, a recording medium having a multilayer structure, where recording capacity is doubled by laminating information layers for recording or reproducing information signals, has been proposed (U.S. Pat. No. 5,726,969). Under such circumstances, read-only DVD-ROM disks including two information layers have been put into practical use.
On the other hand, optical disks that can be recorded in the user's environment have been achieved using a phase changeable material, a magneto-optical recording material, a dye material, or the like. There are two systems for recording signals on such optical disks: a sector-structure system and a continuous recording system. The former is used mainly to record data information, while the latter is used to record sound information, such as CD-Rs.
In the optical disks having a sector structure, an area for managing information to be recorded and a data area on which information signals are recorded by users are separated. However, when the recording system of a sector structure is applied to a multilayer recording medium, reproduced signals are distorted because of the recorded state of adjacent layers.
FIG. 9
shows a cross section of a conventional two-layer disk and an example of reproduced signals from an information layer. In the two-layer disk shown in FIG.
9
(
a
), a first information layer
2
and a second information layer
4
are formed on a substrate
1
, and a separating layer
3
is provided between the two information layers. On top of that, a protective substrate
5
is formed.
The first information layer
2
has a sector structure including a data area
8
for recording information signals and a sector address
9
spaced at predetermined intervals along the length of the data area. The sector address
9
is used for management information for recording/reproducing information signals. Similarly, the second information layer
4
also includes a data area
12
and a sector address
13
.
In FIG.
9
(
a
), the first information layer
2
is not recorded, whereas signals are recorded on the second information layer
4
.
FIG.
9
(
b
) shows reproduced signals from the second information layer
4
. In this case, since transmissivity of the first information layer
2
is unchanged, constant signals in accordance with a pattern recorded on the second information layer
4
can be reproduced.
On the other hand, in FIG.
9
(
c
), the first information layer
2
is recorded; FIG.
9
(
d
) shows reproduced signals in such a case. Here, the first information layer
2
has the characteristic in which its transmissivity is increased by recording information. As shown in FIG.
9
(
d
), the reproduced signals from the second information layer
4
have a waveform whose amplitude is increased in the area corresponding to the recording area of the first information layer
2
.
As described above, in an optical disk having a sector structure, signals are recorded only on the data area, not on the sector address. Therefore, when information signals are reproduced, the amplitude of reproduced signals and the signal level fluctuate significantly depending on the recorded state of the opposite layer. In particular, when the reproduced signals from the second information layer are demodulated, reproduction errors are caused in the area corresponding to the boundary between the address portion and the data area of the first information layer, so that the recorded information cannot be demodulated correctly.
Similarly, in recording, the amount of light that reaches the second information layer varies depending on the recorded state of the first information layer, so that information does not recorded correctly.
DISCLOSURE OF INVENTION
The present invention is intended to solve the conventional problems described above and has an object of providing an optical information recording medium that can prevent the effect of the recorded state of other information layers and can be reproduced stably regardless of the level fluctuation of reproduced signals, a method for recording/reproducing signals on/from the optical information recording medium, and a method for manufacturing the same.
In order to achieve the above object, a first optical information recording medium of the present invention includes a substrate and at least two information layers formed on the substrate. The information layer is formed of a thin film that shows a change that is optically detectable by irradiation of light beams. A separating layer that is transparent to a wavelength of the light beams is formed between the information layers. Each information layer has a sector structure including a sector address and a data area that are divided in the circumferential direction. The positions of the sector addresses of the respective information layers coincide in the circumferential direction. The optical information recording medium described above can prevent errors during reproduction caused by the effect of other information layers, even in the case of an information recording medium of multilayer recording type with a sector structure, and thus stabilizing its recoding characteristics.
The first optical information recording medium includes a first substrate and a second substrate having a sector structure including a sector address and a data area that are divided in the circumferential direction. A first information layer is formed on the first substrate, and a second information layer opposed to the first information layer is formed on the second substrate. It is preferable that the position of the sector address of the first substrate and the position of the sector address of the second substrate coincide in the circumferential direction. The optical information recording medium described above can prevent errors during reproduction caused by the effect of other information layers, even in the case of an information recording medium of multilayer recording type with a sector structure, and thus stabilize its recording characteristics.
Furthermore, it is preferable that the amount of dislocation between the sector addresses of the respective information layers in the circumferential direction be smaller than the sum of the length of the gap between the sector address and the data area and the length of a guard data in the data area. The amount of dislocation within the above range can ensure the amplitude of reproduced signals of the data signals in the data area.
It is preferable that each information layer further includes a management area, and that a sector position identifier for identifying the position of a sector is located in the area other than the data area, the sector address, and the management area of each information layer so as to have a certain relationship to the sector address of each information layer in the circumferential direction. The optical information recording medium described above can facilitate adjusting the position of each information layer.
It is preferable that the sector position identifier is arranged in proximity to the management area at the inner circumferential region thereof, and that the shape of the sector position identifier formed on the information layer closest to the substrate is different from the shape of the sector position identifier formed on the other information layers. The optical informat
Nagata Ken'ichi
Nishiuchi Ken'ichi
Matsushita Electric - Industrial Co., Ltd.
Mechant & Gould P.C.
Patel Gautam R.
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