Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
1999-12-30
2001-09-25
Neyzari, Ali (Department: 2651)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C369S275300
Reexamination Certificate
active
06295271
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical recording medium to and from which information is recorded and reproduced by the use of light, a method for manufacturing the optical recording medium, and an optical information recording and reproducing device used with respect to the optical recording medium.
BACKGROUND OF THE INVENTION
A rapid technological innovation has recently been achieved as to the optical recording medium to and from which signals are recorded and reproduced by the use of light. Numerous attempts have been made particularly to increase recording capacity, working out various element technologies for this purpose.
Among such technologies there are those relating to a disk-shape medium to which information is recorded, that is, a so-called optical disk. The optical disk usually has a configuration wherein a recording medium layer is provided on a substrate having tracks thereon. In this case, by making a light spot trace the tracks, the light spot is caused to accurately follow lines of fine recording marks.
In the case of the optical disk, when tracks are formed on the substrate, address information of the tracks are also marked on the tracks at the same time. Specifically, pits indicating track numbers, sector numbers, etc., are formed on the tracks or between the tracks, and by reading them the address information can be obtained.
In another method for marking address information, wobbled grooves are used. To be more specific, as shown in
FIG. 13
, both side walls of a groove
101
provided on an optical disk (they are also side walls of adjacent lands
102
) are wobbled in a direction orthogonal to a longitudinal direction of the track (the method using such grooves is hereinafter referred to as both-side-wobble method). A wobble frequency obtained therefrom is modulated by a certain method, and address information is allocated to it. In this case, by setting the wobble frequency higher than frequencies to which the light spot is capable of following, the light spot does not follow the wobble frequency during tracking and wobble frequency components are always added to a tracking signal. Therefore, by detecting the wobble frequency components, the address information can be obtained. Incidentally, as a method for increasing the capacity of the optical disk, a land/groove recording method has been proposed. Conventionally signals are recorded on either the grooves or the lands between the grooves, but in contrast, the above method is for recording information on both the grooves and lands. In this case, it is impossible to accurately record address information to lands
102
wobbled in a manner as shown in
FIG. 13
, since a width of the land
102
varies with wobbles of the two adjacent grooves
101
.
As a method to solve this problem, a method using grooves one of whose side walls is wobbled, that is, a single-side-wobble method, is disclosed by the Japanese Publication for Laid-open Patent Application No.5-314538/1993 (Tokukaihei No.5-314538). The method is applied to an optical disk having grooves
111
and lands
112
thereon wherein only one side wall of each groove
111
is wobbled, as shown in
FIG. 14
, so that address information is recorded, using a wobble frequency obtained from the wobble.
However, in the case of the both-side-wobble method and the single-side-wobble method both, every groove (or land) has a wobbled side wall, that is, a portion being tracked always has a wobbled side wall. Therefore, a reproduction signal of information includes wobble frequency components since mixture of wobble frequency components occurs when information signals are recorded or reproduced. As a result, signal quality deteriorates.
Besides, due to the above-mentioned signal mixture, it is necessary to set the wobble frequency in a frequency band different from the frequency band for the information signal, and hence the wobble frequency is set much lower than the frequency of the information signal. Therefore, the spatial wavelength of the wobble frequency becomes long, and accordingly each domain has to be long so as to express each piece of address information. As a result, making divisions between addresses clear and precise is failed.
This does not signifies much in the case of signals to be continuously transmitted, such as video signals or sound signals. However, in the case where an optical disk is used as a memory of a computing device wherein signal transmission is frequently carried out, signals are grouped into blocks when transmitted, and it is necessary to arrange data by a so-called sector method. In this case, the above matter becomes a serious problem.
Besides, since the width of the grooves or the lands varies in some areas, there arise a problem that the beam spot may have an offset, and besides, a problem that the offset is difficult to correct.
There are more methods for providing address information in the case where the land/groove recording method is used. For example, an exclusive address method and a common address method are reported by “Nikkei Electronics” (Nov. 6, 1995, p. 168).
The former is a method whereby at every sector in both the lands and grooves, a pre-pit is provided exclusively for the sector. However, since it is necessary that the pit width is sufficiently narrower than the track width, the pre-pits cannot be formed by the use of a light beam used for forming the tracks. Thus, this method has a defect of making it difficult to manufacture optical disks.
By the latter, that is, the common address method, as shown in
FIG. 15
, pit series
123
are provided on borders between grooves
121
and lands
122
so that each pair of adjacent groove
121
and land
122
share pit series
123
. In this case, a light spot
124
always tracks off the center of pit series
123
when reproducing the pit, during both the tracking operations with respect to the grooves
121
and lands
122
. Therefore, there arises a problem that the signal quality is low.
Further, when the light spot
124
passes the pit series
123
, the light spot
124
does not tracks on a center line of the pit series
123
, thereby causing a great off-set to be added to the tracking signal. Since the pits are intermittently provided, the tracking signal obtained from the pits is also intermittent, but it comes to a great off-set on the average.
A tracking servo system usually does not respond to the tracking signal itself obtained from the individual pit since the pit frequency is sufficiently higher than a frequency band of the tracking servo system. However, since the pit region is considerably long in the present case, the tracking signal is averaged through out the pit region, thereby becoming a signal having a great off-set, to which the servo system responds. As a result, a signal having great spikes is generated when the light spot passes through the pit region. An actuator of the tracking servo system responds to the signal having spikes in the case where the pit region is considerably long, thereby causing a problem of transient response, which reversely affects the signal recording and reproduction.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an optical recording medium which has the following properties when the land/groove recording method is applied: (1) mixing of wobble frequency components in the information signals does not occur; (2) the sector method is applicable thereto without difficulties; and (3) information signals of high quality is reproduced. It is also the object of the present invention to provide a method for manufacturing the optical recording medium and to provide an optical information recording and reproducing device for the use with respect to the optical recording medium.
To achieve the above object, an optical recording medium of the present invention, which has a plurality of lands and grooves between the lands, each of the lands and the grooves serving as a track on which a light beam is projected for recording, reproducing, and erasing information, is characterized
Hirokane Junji
Iketani Naoyasu
Inui Tetsuya
Mieda Michinobu
Murakami Yoshiteru
Conlin David G.
Daley, Jr. William J.
Dike, Bronstein, Roberts and Cushman, Intelletual Property Group
Neyzari Ali
Sharp Kabushiki Kaisha
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