Dynamic information storage or retrieval – Control of storage or retrieval operation by a control...
Reexamination Certificate
2000-11-07
2004-11-16
Hindi, Nabil (Department: 2655)
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
C369S275300, C369S047270
Reexamination Certificate
active
06819640
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disc-shaped record medium preferable as a writable optical disc such as a write once optical disc (CD-R), a rewritable optical disc (CD-RW), and a mini disc (MD), a method for manufacturing the same, and an apparatus for manufacturing the same.
Specifically, in the present invention, a simulation is conducted at the time of writing pre-format addresses in an original disc for the disc-shaped record medium. In the simulation, in order that the crosstalk caused by the coexistence of an arbitrary pre-format address with the other pre-format address adjacent to the arbitrary pre-format address in the inner and outer peripheral direction at the reading point of the arbitrary pre-format address, specific dummy information for timing adjustment is inserted beforehand between the pre-format address in the target frame and the pre-format address in the other frame next to the target frame. Based on the result of the simulation, the pregrooves and the lands are defined on the original disc. In thus-formed original disc, there is no problem in preventing crosstalk between adjacent pregrooves. By use of the original disc, it is possible to manufacture a writable optical disc having high storage density.
2. Description of the Related Art
In recent years, as information media for editing and recording audio information in such a manner as to suit the preferences of listeners, writable optical discs such as write once optical discs (CD-R) and rewritable optical discs (CD-RW) standardized in ISO/IEC13490-1 are increasingly used. In each of these optical discs
10
, as shown in
FIG. 1A
, grooves
1
for guiding a light beam (hereinafter, referred to as pregrooves) are formed, and a positioning method referred to as a tracking servo is employed. The tracking servo is a mechanism where pits and projections constituting lands
2
formed on both sides of each pregroove
1
are detected to decide the position of an optical pickup, so that the desired pre-format address is accurately irradiated with a laser beam.
Sloped surfaces of the land, which coincide to side surfaces of the pregroove
1
, is formed with a slight wobble in the form of sine wave in-phase with each other as shown in FIG.
1
B. The wobble signal indicating the wobble component has been subjected to FM modulation. In the wobble signal, time axis information indicating the position on the optical disc
10
, and a recommended value of the power of the laser beam optimum for recording, etc. are encoded.
The time axis information is referred to as ATIP (absolute time in pregroove) information, and is written as an absolute time in the signal recording region (i.e. a program region) of the optical disc
10
along a direction from the starting point at its inner peripheral side toward its outer peripheral side. The ATIP information is written in the processing of the CD-R and CD-RW. The ATIP information is written in the optical disc
10
such as CD-R and CD-RW in a modulation mode referred to as bi-phase modulation mode. In this mode, a baseband modulation is conducted where, depending on whether the waveform of the last pulse signal constituting the error correction information of the immediately preceding pre-format address ends at a high level or low level, the pre-format address in the next frame is connected without being inverted, or the pre-format address is inverted and connected.
The ATIP information is written, for example, in the side surfaces Us, Ut of the pregroove
1
between two lands
2
a
,
2
b
shown in FIG.
1
B. That is, the ATIP information is written in the side surface Us of the land
2
a
located at the inner peripheral side of the pregroove
1
in which data is recorded, and in the side surface Ut of the land
2
b
located at the outer peripheral side of the pregroove
1
in such a manner that the ATIP information written in the side surface Us is synchronous to the ATIP information written in the side surface Ut.
Therefore, the ATIP information can be read as a wobble signal by detecting the wobble formed in the land
2
b
located at the outer peripheral side by the preceding side spot
3
. The preceding side spot
3
is a light beam preceding a main spot
4
which is a light beam for recording information. The circle broken double lines in
FIG. 1B
show spot diameters of the light beam irradiated to the optical disc having a standard density. The broken circle line in
FIG. 1B
shows a spot diameter of a light beam for an optical disc with a standard density. The circle broken double lines shows a light beam of which irradiation diameter is relatively enlarged as the pregrooves are formed so as to be closer to each other in proportional to the increase in a storage density of the disc-shaped record medium
10
. This problem arises because there is a limitation on enlarging the spot diameters of the light beam.
A wobble formed in the land
2
a
located at the inner peripheral side is detected as a wobble signal by the posterior side spot
5
. The wobble signal is produced in such a manner that its center frequency becomes 22.05 kHz for example, when the optical disc
10
is rotated at a standard velocity (CLV) of a compact disc (CD). One sector of the ATIP information is constituted in such a manner as to coincide to one data sector after the signal is recorded. Therefore, at the time of recording information, the pre-groove
1
is irradiated with a light beam with a predetermined intensity and information is written therein while the sector of the ATIP information is synchronous with the data sector.
In the bi-phase modulation mode according to a conventional example, when the error correction information for the bi-phase signal of the immediately preceding pre-format address ends at high level, a baseband modulation is conducted in such a manner that the bi-phase signal of the pre-format address having synchronous information starting at low level is connected. Contrary to this, when the error correction information for the bi-phase signal of the immediately preceding pre-format address ends at low level, a baseband modulation is conducted in such a manner that the bi-phase signal of the pre-format address having synchronous information starting at high level is connected.
If pre-format addresses are written in the bi-phase modulation mode as it is without conducting any processing in the recent situation where the lands
2
a
,
2
b
are arranged at narrower pitches P in accordance with the increase in the storage density of the optical disc
10
(hereinafter, referred to as a disc-shaped record medium in some cases), the light beam of which irradiation diameter is relatively enlarged as the pregrooves are formed so as to be closer to each other is applied across the adjacent pregrooves (see FIG.
1
B). In this case, there arises much fear that crosstalk is generated. The crosstalk causes phase modulation to create jitter.
As a result, when the bi-phase signal constituting the target pre-format address at the reading point is superimposed on the bi-phase signal of the other pre-format address adjacent to the target pre-format address, there is a large difference in phases therebetween. Larger jitter is created as the period of high level is shorter.
SUMMARY OF THE INVENTION
The present invention has been conducted to solve the above-described problems of the prior arts, and the objective thereof is to provide a disc-shaped record medium usable for producing a writable optical disc which has high storage density and is capable of preventing crosstalk generated in adjacent pregrooves, a method manufacturing the same, and an apparatus for manufacturing the same.
The above-described problems can be solved by a disc-shaped record medium in which pre-format addresses are written along its grooves for guiding a light beam. In the disc-shaped record medium, in order that the crosstalk caused by the coexistence of an arbitrary pre-format address with the other pre-format address adjacent to the arbitrary pre-format address in t
Hindi Nabil
Sony Corporation
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