Optical compact disc with an increased memory capacity

Details Optical compact disc with an increased memory capacity Optical compact disc with an increased memory capacity

2000-07-13

2003-05-27

Neyzari, Ali (Department: 2655)

Dynamic information storage or retrieval

Storage medium structure

Optical track structure

C369S053200, C369S044260

Reexamination Certificate

active

06570838

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an improved optical compact disc (CD). More particularly, the present invention relates to a CD that can be read and/or written by suitable electronic apparatuses to memorize data, that allows a higher memory capacity, and that increases the difficulties in copying the memory contents onto other writable or re-writable CD by unauthorized users.
BACKGROUND OF THE INVENTION
It is well known how the use of optical supports for the memorization of data is extremely diffused. Particularly, for exemplificative but not limitative purposes, audio digital (DA) or only readable (CD-ROM) or only once writable (CD-R OR CD-WORM) or re-writable (CD-RW) compact discs (CD) are widely used in musical, video, and photo industries as well as in software field.
Compact discs typically have a circular shape with an axial hole. They can be read and/or written by specific apparatus that have a CD rotation mechanism interacting with the axial hole and with laser optical devices. The housings of the apparatus within which CDs are introduced typically have a circular shape and are dimensioned corresponding to the CDs to be housed. Particularly, within the housings, a plurality of concentric seats can be provided, corresponding to the standard dimensions of the various kinds of CDs.
Data, with a binary digital format, are physically memorized on CDs as pits and lands on the surface of the disc along a spiral-shaped track running all along the surface of the same disc. Reading optical apparatuses generate a laser beam that is focused on the track and reveal by a photo-detector the amount of light reflected by the surface of the disc. The amount of light reflected varies depending on whether it comes from a pit or a land.
The physical features of all conventional CDs are substantially the same and formed according to international standard defined on 1982. Particularly, the standard has been defined in function of specific writing and reading modes of the optical apparatuses interacting with the CD.
The spiral-shaped track of the memorized data on a CDROM is scanned by the optical reading apparatus with a constant linear scanning velocity (CLV), the value of which is defined by the standard as included in the range between 1.2 and 1.4 m/s.
The international standard also defines the distance between two contiguous involutions of the spiral-shaped track, also known as “track pitch”, that must be of 1.6 &mgr;m.
Furthermore, the international standard sets that all the CDs provide the presence of nine sections of the track, each of them containing specific information, identified as nine areas having a circular crown on the optically active surface of the disc. The following table lists the nine sections, with the relevant name and the radial distance from the center of the disc to the beginning of the section:
Section
Radial Distance (&mgr;m)
Continuous Track Inside
18000
Master ID Number
18700
Test Signal Inside
21700
Lead In
23500
Program Area
24400
First Lead Out
56700
Development Band
58000
Test Signal Outside
59000
Continuous Track Outside
59600
The organization of the disc track maintains the initially planned division for the audio digital CD.
However, the physical features of CD set by the international standard has some drawbacks. First of all, memory capacity is limited by the high values of CLV and by the track pitch. Further, outer sections of the track starting from the First Lead Out are not used by CD-ROM, thus obtaining a further reduction of the real memory capacity with respect to the potential one.
Finally, since the standard is rigidly fixed for any kind of CD, using a once writable CD (CD-R or CD-WORM) or a re-writable CD (CD-RW), it is easy also for an unauthorized user to make a copy of an audio CD or of a CD-ROM.
SUMMARY OF THE INVENTION
Therefore, the object of the present invention is to provide a simple and reliable CD that has a higher memory capacity and that can not be copied on the conventional once writable CD (CD-R or CD-WORM) or re-writable CD (CD-RW).
It is therefore another object of the present invention to provide an improved optical CD, on which the data, with a binary digital format, are physically memorized as pits and lands of the disc surface along a spiral-shaped track running all along the surface of the disc. The track is scanned, during the data reading phase, by a reading optical apparatus with a constant linear velocity (CLV). The CD can comprise at least a first portion of the track that is scanned, during the data reading phase, with a CLV of between about 0.1 m/s and 1.2 m/s, preferably between about 0.9 m/s and 1.2 m/s. The CD can comprise at least a second portion of the track wherein the consecutive involutions of the spiral are separated by a constant track pitch of between about 1.3 &mgr;m and 1.6 &mgr;m, preferably of 1.4 &mgr;m.
Always according to the invention, the first portion of the track can be the whole the track.
Still according to the invention, the second portion of the track can be the whole track.
Furthermore, according to the invention, the first portion of the track and the second portion of the track can be at least partially overlapped.
Always according to the invention, the spiral-shaped track can comprise at least five sections, preferably five sections. The beginning of the first five sections can have a radial distance from the center of the disc of 18000 &mgr;m, 18700 &mgr;m, 21700 &mgr;m, 22500 &mgr;m and 23400 &mgr;m, respectively.
Preferably, according to the invention, the optical compact disc is an only readable CD, or a CD-ROM.


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patent: 0 978 830 (2000-02-01), None

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