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AssigneeU.S. Philips Corporation
InventorsMaarten R. de Haan, Klaas Compaan, Leopold H. Hissel
Estimating the term…
Disclosed is a record carrier for storage of digital data which is provided with a first periodic track variation having a period corresponding to a frequency at which the power spectrum of the digital signals is at a zero level. The first track variation produces a corresponding modulation of the radiation when scanned by a beam so that a clock signal can be derived from the detected radiation for synchronizing readout or recording of the data. The record carrier is further provided with a second periodic track variation in a direction transverse to the track direction having a period of the same order of magnitude, and preferably equal to the period of the first periodic track modulation. The second track variation produces a corresponding modulation of the beam which is detected and is used to generate to a tracking signal, the clock signal being used as phase reference signal for demodulation of the tracking signal. If the periods of the two track variations are equal, low-pass filtering automatically yields the tracking signal.
A record carrier for storing a digitally coded signal having a fixed bit frequency and a power spectrum with a substantially zero level at a predetermined frequency, said record carrier comprising a substrate provided with at least one information section for storing the digitally coded signal in a form detectable by a beam of radiation and at least one elongated servo track having a first periodic variation of a first period corresponding to said predetermined frequency and a configuration such that when scanned by a beam of radiation, the radiation is modulated by said first periodic variation to produce a first modulation component of a frequency corresponding to said first period for generating a clock signal for synchronizing read out or recording of the digitally coded signal, said servo track further having a second periodic variation in a direction transverse to the longitudinal direction of said servo track of a second period which is at least of the same order of magnitude as said first period, said second variation being configured to produce a second modulation component in the radiation of a frequency corresponding to said second period for generating a tracking signal for guiding a radiation beam used for readout or recording of the digitally coded signal.
A record carrier for storing a digitally coded signal having a fixed bit frequency and a power spectrum with a substantially zero level at a predetermined frequency, which signal is recorded on and/or reproduced from the record carrier by a beam of radiation, said record carrier comprising a disc-shaped substrate provided with at least one generally circular track extending about the center of said substrate and having an information section for storing the digitally coded signal, at least a portion of said track having a first periodic variation of a first period corresponding to said predetermined frequency and a configuration such that when scanned by the beam, the radiation is modulated by said first periodic variation to produce a first modulation component of a frequency corresponding to said first period for generating a clock signal for synchronization of the recording or reproduction of the digitally coded signal on or from, respectively, said information section, said track portion further having a second periodic variation in a radial direction of a second period which is at least of the same order of magnitude as said first period, said second variation being configured to produce a second modulation component in the radiation of a frequency corresponding to said second period for generating a radial tracking signal for guiding the beam during recording or reproduction of the digitally coded signal.
An apparatus for forming an optically detectable track in an optical record carrier blank provided with a radiation sensitive layer for storing a digitally coded signal having a fixed bit frequency and a power spectrum with a substantially zero level at a predetermined frequency, said apparatus comprising means for producing a beam of radiation, means for focusing said beam to a spot on said layer, means for producing relative movement between said spot and said blank so that said spot inscribes an elongated track in said layer, first means for modulating said beam so as to produce a first, optically detectable, periodic variation in the track of a period corresponding to said predetermined frequency, and second means for modulating said beam so as to produce a second, optically detectable, periodic variation in the track in a direction transverse to the longitudinal direction of said track of a period at least of the same order of magnitude as the period of said first variation.
An apparatus for recording a digitally coded signal having a fixed bit frequency and a power spectrum with a substantially zero level at a predetermined frequency on a record carrier provided with a radiation sensitive layer and at least one elongated track, said track having a first periodic variation of a period corresponding to said predetermined frequency and a second periodic variation in a direction transverse to the longitudinal direction thereof with a period of at least the same order of magnitude as the period of said first variation, said apparatus comprising means for producing a beam of radiation, means for focusing said beam to a spot on said record carrier, means for producing relative movement between said record carrier and said spot so that said spot scans said track and is modulated by said periodic variations thereof, means for modulating a write beam of radiation in accordance with the digitally coded signal to be recorded on said radiation sensitive layer, means for detecting radiation which is modulated by said variations and is reflected or transmitted by the record carrier, said detecting means producing an electrical signal representative of the modulation of the detected radiation, first means for deriving from said electrical signal a first signal of a first frequency corresponding to the period of said first track variation at a predetermined scanning speed so as to obtain a clock signal which is applied to said modulating means for synchronizing the recording of said digital signal, second means for deriving from said electrical signal a second signal of a second frequency corresponding to the period of said second periodic variation at said predetermined speed, third means for deriving from said first and second signals a tracking signal indicative of the displacement of said spot from the center of said track, and means responsive to said tracking signal for maintaining said spot centered on said track.
An apparatus for recording a digitally coded signal having a fixed bit frequency and a power spectrum with a substantially zero level at a predetermined frequency on a record carrier provided with a radiation sensitive layer and at least one elongated track, said track having a first periodic variation of a period corresponding to said predetermined frequency and a second periodic variation in a direction transverse to the longitudinal direction thereof, with a period equal to the period of said first variation, said first and second variations having a fixed phase relationship with each other, said apparatus comprising means for producing a beam of radiation, means for focusing said beam to a spot on said record carrier, means for producing relative movement between said record carrier and said spot so that said spot scans said track and is modulated by said periodic variations thereof, means for modulating a write beam of radiation in accordance with the digitally coded signal to be recorded on said radiation sensitive layer, means for detecting radiation which is modulated by said variations and is reflected or transmitted by the record carrier, said detecting means producing an electrical signal representative of the modulation of the detected radiation, means for deriving from said electrical signal a first signal of a first frequency corresponding to the period of said first track variations at a predetermined scanning speed so as to obtain a clock signal which is applied to said modulating means for synchronizing the recording of said digital signal, and a low pass filter for filtering said electrical signal in order to obtain a tracking signal indicative of the displacement of said spot from the center of said track, and means responsive to said tracking signal for maintaining said spot centered on said track.
An apparatus for reading a record carrier containing digitally coded information recorded thereon in a first, elongated track portion, said digitally coded information having a fixed bit frequency and a power spectrum with a substantially zero level at a predetermined frequency, said record carrier having at least one elongated servo track portion which is generally parallel to said first track portion, said servo track portion having a first periodic variation of a period corresponding to said predetermined frequency and a second periodic variation in a direction transverse to the longitudinal direction thereof with a period of at least the same order of magnitude as the period of said first variation, said apparatus comprising means for producing a beam of radiation, means for focusing said beam to a spot on said record carrier, means for producing relative movement between said record carrier and said spot so that said spot scans said first and said servo track portions and is modulated thereby, means for detecting modulated radiation coming from the record carrier, said detecting means producing an electrical signal representative of the modulation of the detected radiation, first means for deriving, from said electrical signal, a first signal representative of the recorded, digitally coded information, second means for deriving from said electrical signal a second signal of a first frequency corresponding to the period of said first track variation at a predetermined scanning speed so as to obtain a clock signal which is applied to said first deriving means for synchronizing the read out of said digitally coded information, third means for deriving, from said electrical signal, a third signal of a second frequency corresponding to the period of said second periodic variation at said predetermined speed, fourth means for deriving from said second and third signals a tracking signal indicative of the displacement of said spot from the center of the track portion being scanned, and means responsive to said tracking signal for maintaining said spot centered on the track portion being scanned.
An apparatus for reading a record carrier containing digitally coded information recorded thereon in a first, elongated track portion, said digitally coded information having a fixed bit frequency and a power spectrum with a substantially zero level at a predetermined frequency, said record carrier having at least one elongated servo track portion which is generally parallel to said first track portion, said servo track portion having a first periodic variation of a period corresponding to said predetermined frequency and a second periodic variation in a direction transverse to the longitudinal direction thereof with a period equal to the period of said first variation, said first and second variations having a fixed phase relationship with each other, said apparatus comprising means for producing a beam of radiation, means for focusing said beam to a spot on said record carrier, means for producing relative movement between said record carrier and said spot so that said spot scans said first and said servo track portions and is modulated thereby, means for detecting modulated radiation coming from the record carrier, said detecting means producing an electrical signal representative of the modulation of the detected radiation, first means for deriving from said electrical signal a first signal representative of the recorded, digitally coded information, second means for deriving from said electrical signal a second signal of a first frequency corresponding to the period of said first track variations at a predetermined scanning speed so as to obtain a clock signal which is applied to said first deriving means for synchronizing the read out of said digitally coded information, and a low pass filter for filtering said electrical signal in order to obtain a tracking signal indicative of the displacement of said spot from the center of the track portion being scanned, and means responsive to said tracking signal for maintaining said spot centered on the track portion being scanned.
Dependencies are inferred from the claim text.