Patent EA-002489-B1 (EA)
Title: Record carrier and apparatus for scanning the record carrier
Inventor: VAN VLERKEN JOHANNES J L M
IPC: G11B27/19
Filed: 2000-01-11
Abstract: 1. Record carrier comprising a servo track (4) indicating an information track (9) intended for recording information blocks represented by marks having lengths expressed in channel bits, which servo track (4) has a periodic variation of a physical parameter which periodic variation is modulated for encoding record carrier information, characterized in that said modulation is a bi-phase modulation in which a data bit of the record carrier information is encoded by a first predetermined number of variations of a first phase followed by the same number of variations of a second phase inverse to the first phase. 2. Record carrier as claimed in claim 1, wherein the servo track is subdivided in relatively small parts having said bi-phase modulation and relatively large parts having not modulated periodic variations. 3. Record carrier as claimed in claim 2, wherein the small parts comprise a sync part and a data part, the sync part comprising at least one variation of a phase inverse to the phase of the not modulated periodic variations. 4. Record carrier as claimed in claim 3, wherein a word sync data part comprises a second predetermined number of periodic variations of the phase of the not modulated periodic variations and a word sync part comprises the same number of periodic variations of a phase inverse to the phase of the not modulated periodic variations for indicating a record carrier information word. 5. Record carrier as claimed in claim 1, wherein said first predetermined number of variations of a first phase is 2. 6. Record carrier as claimed in claim 2, wherein the small parts have 8 periodic variations and the large parts have 85 periodic variations. 7. Record carrier as claimed in claim 1, wherein the length of one periodic variation corresponds to a third predetermined number of channel bits. 8. Record carrier as claimed in claim 7, wherein the third predetermined number is 32. 9. Recording and/or playback device comprising means for writing and/or reading information blocks represented by marks having lengths expressed in channel bits in an information track (9) on a record carrier that comprises a servo track (4) indicating the information track (9), which device comprises means for scanning the servo track (4) and retrieving record carrier information encoded in a modulation of a periodic variation of a physical parameter of the servo track, characterized in that the device comprises bi-phase demodulation means for retrieving data bits of the record carrier information from a first predetermined number of variations of a first phase followed by the same number of variations of a second phase inverse to the first phase. 10. Device as claimed in claim 9, wherein the bi-phase demodulation means are arranged for synchronizing to a sync part comprising at least one variation of a phase inverse to the phase of the not modulated periodic variations, the servo track being subdivided in relatively small parts having said bi-phase modulation and sync part, and relatively large parts having said not modulated periodic variations. 11. Device as claimed in claim 10, wherein the device comprises address detection means for detecting an address of a part of the track from a number of the data bits from a record carrier information word, a word sync data part comprising a second predetermined number of periodic variations of the phase of the not modulated periodic variations and the sync part comprising the same number of periodic variations of a phase inverse to the phase of the not modulated periodic variations for indicating the record carrier information word. 12. Device as claimed in claim 9, wherein the device comprises recording positioning means for positioning an information block to be recorded based on the physical location of one of the periodic variations corresponding to an address of said information block by calculating said physical location from the length of one periodic variation corresponding to a third predetermined number of channel bits. 13. Method of manufacturing a record carrier, in which the record carrier is provided with a servo track (4) indicating an information track (9) intended for recording information blocks represented by marks having lengths expressed in channel bits, which servo track (4) is provided with a periodic variation of a physical parameter which periodic variation is modulated for encoding record carrier information, characterized in that a data bit of the record carrier information is encoded by a first predetermined number of variations of a first phase followed by the same number of variations of a second phase inverse to the first phase.