IMPROVED OPTICAL COMPACT DISC, OR CD

Abstract: The invention concerns an improved optical compact disc, or CD, on which the data, with a binary digital format, are physically memorised as pits and lands of the disc surface along a spiral-shaped track running all along the surface of the disc, said track being scanned, during the data reading phase by a reading optical apparatus, by the reading optical apparatus with a constant linear velocity (CLV), the CD being characterised in that it provides at least a first portion of the track that is scanned, during the data reading phase, with a CLV included between 0.1 m/s and 1.2 m/s, preferably included between 0,9 m/s and 1.2 m/s, and/or at least a second portion of the track wherein the consecutive involutions of the spiral are separated by a constant track pitch included between 1.3 and 1.6 mu m, preferably of 1.4 mu m.

Description: IMPROVED OPTICAL COMPACT DISC, OR CD The present invention relates to an improved optical compact disc, or CD. More particularly, the invention relates to a CD, suitable to be read and/or written by suitable electronic apparatuses, for the memorisation of data, allowing a higher memory capacity and increasing the difficulties of copying the memory contents on other writable or rewritable CD, by unauthorised users. It is well known how the use of optical supports for the memorisation 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 really very much used by the industries for musical, video and photos productions, as well as in the software field. CD, having a circular shape with an axial hole, are read and/or written by specific apparatuses, provided with CD rotation mechanism interacting with said axial hole, and with laser optical devices, The housings of said apparatuses within which CD are introduced, have a circular shape and dimensions corresponding to those of the CD to be housed. Particularly, within said housings, a plurality of concentric seats can be provided, corresponding to the standard dimensions of the various kind of CD. The data, with a binary digital format, are physically memorised on the CD 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, that is different whether it comes from a pit or a land. The physical features of the present CD are standard, according to international rules defined on 1982, and that is substantially the same. Particularly, said 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 memorised 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 μm. Furthermore, the international standard sets that all the CD 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 said nine sections, with the relevant name and the radial distance from the centre of the disc to the beginning of the section: Said organisation 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 unauthorised user to make a copy of an audio CD or of a CD-ROM. Therefore, the object of the present invention is that of providing in a simple and reliable way, a CD having a higher memory capacity and that cannot be copied on the present once writable CD (CD-R or CD- WORM or re-writable CD (CD-RW). It -is therefore specific object of the present invention an improved optical compact disc, or CD, on which the data, with a binary digital format, are physically memorised as pits and lands of the disc surface along a spiral-shaped track running all along the surface of the disc, said track being scanned, during the data reading phase by a reading optical apparatus, by the reading optical apparatus with a constant linear velocity (CLV), the CD being characterised in that it provides at least a first portion of the track that is scanned, during the data reading phase, with a CLV included between 0.1 m/s and 1.2 m/s, preferably included between 0,9 m/s and 1.2 m/s, and/or at least a second portion of the track wherein the consecutive involutions of the spiral are separated by a constant track pitch included between 1.3 and 1.6 μm, preferably of 1.4 μm. Always according to the invention, said first portion of the track can be the whole the track. Still according to the invention, said second portion of the track can be the whole track. Furthermore, according to the invention, said at least first portion of the track and said at least one 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 having a radial distance from the centre of the disc of 18000 μm, 18700 μm, 21700 μm, 22500 μm and 23400 μm. Preferably, according to the invention, the optical compact disc, or CD, is an only readable CD, or CD-ROM. The present invention will be now described, for illustrative but not limitative purposes, according to one preferred embodiment. As already said, the reading optical apparatuses detect by a photo-detector the amount of light reflected by the disc surface, that is different according to if it comes from a pit or from a land. CD according to the invention provides that the reading mode is not modified, but that the track is scanned, at least in a portion of the same, by a constant linear velocity, or CLV, having a value lower than the standard value, and that pits/lands have a consequently reduced length. In this way, the amount of light reflected detected by the photo-detector for each pit/land is not modified and the amount of information memorised on the disc is higher than for a CD according to the international standard. The preferred embodiment of the CD according to the invention provides that in the track portions with a lower reading velocity, CLV is included between o.9 and 1.2 m/s and that pits/lands have a length consequently reduced with respect to the international standard. Supposing to adopt a uniform CLV all along the CD track of 0.9 m/s, a memory capacity increase of 25% is obtained with respect to a CD according to the standard with a CLV of 1.2 m/s. Other embodiments can provide that CLV is included also between 0.1 and 0.9 m/s. The CD according to the invention further provides that the involutions of the spiral-shaped track are, at least in a portion of the same, closer each other with respect to what provided by the international standard. Particularly, the invention provides that the track pitch in the portion with closer involutions is included between 1.3 and 1.6 μm. The preferred embodiment provides that the track pitch is of 1.4 μm. Supposing to adopt a uniform track pitch all along the CD track of 1.4 m/s, an increase of the memory capacity of 12.5% is obtained with respect to a CD according to the standard with track pitch of 1.6 μm. Writable or re-writable CD (CD-R or CD-WORM and CD-RW) have physical limitations as to the minimum length of pits/lands and the minimum track pitch obtainable on their surface. Therefore, their memory capacity cannot be higher than a maximum value that is lower than the value of the CD according to the invention that therefore cannot be copied. Other embodiments of the CD according to the invention can also provide that the radial distance of the fourth section of the track, called Lead In, is of 22500 μm, and that the radial distance of the fifth section of the track, called Program Area, is of 23400 μm, with a consequent increase of 1 mm of the Program Area, wherein the significative data are memorised. Further embodiments, in particular for the CD-ROM, provide only the presence of the first five sections, (Continuos Track Inside, Master ID number, Test Signal Inside, Lead In, Program Area) set by the international standard, thus obtaining a further extension of the fifth section. The modification of the length of pits/lands, of the track pitch distance and of the number of section along the track occurs on the mould used during the mass-production of the CD according to the invention, without any modification of the apparatuses and of the existing manufacturing modes. The CD according to the invention is readable by the existing optical reading apparatuses, but, as already said, cannot be integrally copied on the present writable or re-writable CD. The present invention has been described for illustrative but not limitative purposes, according to its preferred embodiments, but it is to be understood that modifications and/or changes can be introduced by those skilled in the art without departing from the relevant scope as defined in the enclosed claims.

Claims: CLAIMS 1. Improved optical compact disc, or CD, on which the data, with a binary digital format, are physically memorised as pits and lands of the disc surface along a spiral-shaped track running al) along the surface of the disc, said track being scanned, during the data reading phase by a reading optical apparatus, by the reading optical apparatus with a constant linear velocity (CLV), the CD being characterised in that it provides at least a first portion of the track that is scanned, during the data reading phase, with a CLV included between 0.1 m/s and 1.2 m/s, preferably included between 0,9 m/s and 1.2 m/s, and/or at least a second portion of the track wherein the consecutive involutions of the spiral are separated by a constant track pitch included between 1.3 and 1.6 μm, preferably of 1.4 μm. 2. Improved optical compact disc, or CD, according to claim 1, characterised in that said first portion of the track is the whole track. 3. Improved optical compact disc, or CD, according to claim 1 , characterised in that it said second portion of the track is the whole track. 4. Improved optical compact disc, or CD, according to one of the preceding claims, characterised in that said at least first portion of the track and said at least one second portion of the track are at least partially overlapped. 5. Improved optical compact disc, or CD, according to one of the preceding claims, characterised in that said at least one first portion of the track is scanned, during the data reading phase, with a CLV included between 0.9 m/s and 1.2 m/s. 6. Improved optical compact disc, or CD, according to one of the preceding claims, characterised in that said at least one second portion of the track has a constant track pitch of 1.4 μm. 7. Improved optical compact disc, or CD, according to one of the preceding claims, characterised in that the spiral-shaped track comprises at least five sections, the beginning of the first five sections having a radial distance from the centre of the disc of 18000 μm, 18700 μ , 21700 μm, 22500 μm and 23400 μm. 8. Improved optical compact disc, or CD, according to claim 7, characterised in that the spiral-shaped track comprises five sections. 9. Improved optical compact disc, or CD, according to one of the preceding claims, characterised in that the optical compact disc, or CD, is a only readable CD, or CD-ROM. 10. Improved optical compact disc, or CD, according to each one of the preceding claims, substantially as illustrated and described.

Inventors: JARACH ANDREA, JARACH, ANDREA
Applicants: ATOP INNOVATION S P A, JARACH ANDREA, ATOP INNOVATION S.P.A., JARACH, ANDREA
Application year: 2000
Main classification: G11B7
IPC codes: G11B7