Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
1999-07-13
2002-12-10
Neyzari, Ali (Department: 2653)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C369S053110, C369S053200
Reexamination Certificate
active
06493312
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to an optical information medium, on which can be recorded information which is optically reproducible, and in particular relates to an optical information medium having a sector information detector means suitable for a high density recording medium on which the information can be recorded and reproduced with a short wavelength of from 630 nm to 670 nm.
2. Description of Related Art
With the recent advances in development and application of a short wavelength laser, standardization has proceeded on a standard for DVDs (Digital Versatile Discs) which enables recording and reproducing at a high density, as well as the practical application thereof. On the DVD is provided a data area at least on one surface thereof, in which pits are formed as a means for recorded information, and a reflection layer made of metal film is formed on the data area.
For the DVDs mentioned above, a different standard for high density is determined, compared to the standard for the optical information medium being most general or popular now, such as a CD (Compact Disc). For example, with the optical pickup, it is determined to use a short wavelength of from 630 nm to 670 nm, and to use an objective lens of a high numeral aperture, such as of 0.6 in NA, etc. Accompanying this, for dealing with a tilt of the disc, the thickness thereof is determined to be 0.6 mm, about half (½) of that of the CD. However, for maintaining compatibility or interchangability in sizes between the CD having thickness of 1.2 mm, the disc of the DVDs have such a structure that two pieces of discs are filled up and pasted together. According to the DVD standard, it is standardized that one piece of the disc has a recording capacity of 4.7 GB at the maximum, in average thereof, i.e., video and audio information for a maximum 133 minutes long.
In the standardization process of the DVD standard, in the similar manner of the relationship between the CD-ROM and CD-R or CD-RW, at the beginning were assumed or expected to be standardized both an optical information medium for use or reproduction exclusively (for read-only) and an optical information medium which is recordable. However, the standardization at the beginning was made only on a DVD Video for video and on a DVD for reproduction only, such as a DVD-ROM which is targeted for recording computer data, but the standardization on the recordable DVD was postponed.
Heretofore, on the recordable CD, such as the CD-R, an address information called “ATIP (Absolute Time in Pregroove)” is obtained through FM modulation of wobbles of a tracking guide which is formed in spiral and groove-like shapes. In contrast to this, on the recordable DVD, such as the DVD-R, in place of the ATIP, sector information, including the address information indicative of the position on the optical information medium, can be obtained through land pre pits which are provided in advance on land portions defined between the tracking guides together with the wobbles.
Such land pre pits, which are applied into the high density recording medium as mentioned above, are readout by means of an optical pickup together with the pits of the recorded signals, however, since the optical pickup is guided along the tracking guide by a tracking servo system under a normal condition, the land pre pits and the pits formed on the groove for recording data signals are separately readout by discriminating them to each other. However, depending upon the shape of the land pre pits, there is a possibility that the land pre pits are erroneously readout by being mistaken for the pits for recording of the data signals.
Then, it comes to be a cause of occurring errors in the readout of the data signals. In contrast to this, there is also a possibility that the land pre pits cannot be readout correctly depending upon the shape of the land pre pits, then it causes generation of errors in the sector information including the address and so on, thereby making the reproduction operation unstable.
SUMMARY OF THE INVENTION
Accordingly, an object is, in accordance with the present invention, for solving the drawback(s) mentioned above, i.e., the problem in the readout of the land pre pits for picking up the sector information on the optical information medium corresponding to the high density recording mentioned above, to provide an optical information medium, with which the data signals and the sector information can be readout with discrimination between them correctly, by removing the errors in the readout of the land pre pits indicative of the sector information and of the pits indicative of the data signals on the tracking guide when reading the high density signals optically.
For achieving the object mentioned above, according to the present invention, an optically clear difference is given between the land pre pits
6
indicative of the sector information provided on the land
8
and the pits indicative of the data signals provided on the tracking guide
3
, thereby preventing the erroneous reading of mixing them up with each other. In more detail, the difference is in the lengths of the pits, and in the optical path length of a reproducing light beam incident upon from the optical pickup.
Namely, according to the present invention, there is provided an optical information medium, comprising:
a transparent substrate
1
for a reproducing laser beam to penetrate therethrough;
a recording layer
12
formed on said transparent substrate; and
a reflective layer
13
for reflecting the reproducing laser beam thereupon, thereby enabling the recording of the optically readable signals by means of a recording laser beam incident upon said transparent substrate
1
. This optical information medium has a spiral-like tracking guide
3
on a side surface of said transparent substrate
1
, on which said recording layer
12
is formed, and on lands
8
defined between the spiral-like tracking guide
3
are formed land pre pits
6
indicative of the sector information, including the address and so on, wherein the length of the land pre pits
6
is selected to be different from the lengths of the data pits.
On such an optical information medium, in which the length of the land pre pits
6
is different from that of the data pits, the signal obtained from the data pits formed on the tracking guide
3
can be discriminated from the signals obtained from the land pre pits
6
, with ease. With this, there is no chance to readout the pits for recording the data signals, erroneously, in place of the pits for recording the sector information, thereby enabling the reduction of the reading errors of the data signals as well as the reading errors of the sector information.
For example, in the DVDs, the data pits lengths were from approximately 0.4 &mgr;m to approximately 1.9 &mgr;m. Accordingly, the length of the land pre pits
6
is selected to be shorter than 0.4 &mgr;m, or alternatively to be the length exceeding 1.9 &mgr;m. However, it is unrealistic to make the length of the land pre pits exceed 1.9 &mgr;m, therefore it is preferable to select it to be shorter than 0.4 &mgr;m.
In this instance, it is preferable to shorten the length of the land pre pits
6
as much as possible up to the length of the minimum data pit. However, if the length of the land pre pits
6
is too small in length, it becomes difficult to readout the sector information from the land pre pits
6
. On the other hand, when the length of the land pre pits
6
becomes near the length of the minimum data pits, discrimination cannot be performed easily between the land pre pits
6
and the data pits by the pit length. Then, the length of the land pre pits
6
is selected to be from 50% to 83% of the length of the minimum data pit. For example, the length of the minimum data pits is 3 times as long as a channel clock in the DVD, therefore, the length of the land pre pits
6
is selected to be from 1.5 to 2.5 times the length of the channel clock.
Further, in the optical information medium according to
Fujii Toru
Hamada Emiko
Negishi Ryou
Tajima Toshiaki
Flynn ,Thiel, Boutell & Tanis, P.C.
Neyzari Ali
Taiyo Yuden Co. Ltd.
LandOfFree
Optical information medium does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical information medium, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical information medium will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2955779