Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
1999-03-15
2001-09-25
Dinh, Tan (Department: 2651)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C428S064400
Reexamination Certificate
active
06295270
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of record carriers with a recording layer having substantially parallel tracks for recording information in a pattern of optically detectable marks. The tracks are provided with wobbled grooves and predetermined positions along the tracks, on which positions information is stored in the form of pits. The invention also relates to a method for scanning such a record carrier and for an apparatus carrying out the method.
BACKGROUND OF THE INVENTION
When writing user information on a record carrier using a scanning radiation spot, it is in general desirable to know the position of the radiation spot on the record carrier. Since user information is not available on a virgin recordable record carrier, the position may be determined by reading position information stored in an embossed wobbled grooves or embossed pits of the record carrier.
In general, a track is a line on the record carrier to be followed by a scanning device and has a length of the order of a characteristic dimension of the record carrier. A track on a rectangular record carrier has a length substantially equal to the length or width of the record carrier. A track on a disc-shaped record carrier is a 360° turn of a continuous spiral line or a circular line on the disc.
A track may be a groove and/or a land portion between grooves. A groove is a trench-like feature in a land portion of the recording layer, the bottom of the trench being nearer to or further away from the light-incident side of the record carrier. User information may be recorded on the lands or in the grooves. The pits may be located on the lands or in the grooves.
A record carrier according to the preamble is known from European patent application no. 0 800 165, which discloses an optical record carrier having a groove radially wobbled at a constant frequency without phase jumps and pits formed at predetermined positions between turns of the wobbled groove. The pits are at positions where the wobble has a minimum or maximum deviation as measured from the centre of the pits. The inventors recognized that a of known record carriers is that the reliability of the detection of the pits reduces when user information is recorded in the tracks.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a record carrier having a pit-groove structure which can be detected more reliably.
In accordance with the invention, in the record carrier as described in the opening paragraph, the phase of the wobble at the predetermined positions is adapted to the presence of a pit at such a predetermined position. The wobble of the groove can enhance the signal obtained from the pits when scanning the record carrier. According to the invention, the phase of the wobble at a certain position along the track must be adapted to the presence or absence of a pit at such a position. The detection margin of the pits can be substantially increased when the phase has a first value at a predetermined position where there is a pit and a second, different value at a predetermined position where there is no pit. The increased detection margin allows a reduction of the size of the pits, thereby reducing crosstalk from the pits on the signal representing user information recorded in the tracks.
Preferably, the wobble has a minimum value, as measured from the centre line connecting the pits along a track, at a predetermined position with pit and a maximum value at a predetermined position without pit. When the pits are located on a land portion between two neighbouring grooves, the two grooves are preferably in anti-phase. When the pits are depressions in the land and the grooves are trench-like, the predetermined positions with pits are preferably located at positions where the land has a minimum width and the predetermined positions without pits are preferably located at positions where the land has a maximum width.
The predetermined positions may be arranged at equidistant positions along a track. They may also be grouped in series and the wobble in between subsequent series of predetermined positions in the track direction represents preferably, information. When the information in the wobble is encoded by phase-shift keying, the same phase variation of the wobble may be used for parts of the groove at the position of the predetermined positions and for parts of the groove in between the series of predetermined positions.
The predetermined positions are preferably, grouped in doublets of two neighbouring predetermined positions, and only one pit is present in each doublet. A single logical value may be assigned to a doublet, e.g. a pit followed by a non-pit is a ‘1’ and a non-pit followed by a pit is a ‘0’. When the presence of a pit at both positions in a doublet is determined, the detection margin between a ‘1’ and a ‘0’ is increased compared to a detection at a single position.
In a record carrier wherein land portions are arranged between neighbouring grooves, the land portions are preferably, alternatingly provided with pits and without pits. When scanning a groove, there are pits on only one side of the groove, thereby reducing cross talk between neighbouring tracks.
An apparatus according to the invention, scans an optical record carrier having substantially parallel tracks for recording user information in a pattern of optically detectable marks. The tracks are provided with wobbled grooves and predetermined positions along the tracks, on which information is stored in the form of pits. The apparatus includes an optical system for scanning tracks by a radiation beam, a detector for detecting a radiation beam coming from the record carrier, and a first signal processor for deriving information represented by the pits from an output signal of the detector. The apparatus is provided with a second signal processor for deriving information represented by the wobble from an output signal of the detector, and a selector for forming an information signal from an information output signal of the first signal processor and an information output signal of the second signal processor.
A method according to the invention scans an optical record carrier having substantially parallel tracks for recording user information in a pattern of optically detectable marks. The tracks are provided with wobbled grooves and predetermined positions along the tracks, on which information is stored in the form of pits. During scanning an information signal is derived from one of the pits, the wobble, and the pits and the wobble, depending on selection criteria.
The objects, advantages and features of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings, in which;
REFERENCES:
patent: 5270998 (1993-12-01), Uchiumi
patent: 6075761 (2000-06-01), Akiyama et al.
patent: 0 347 858 A2 (1989-12-01), None
patent: 0 800 165 A1 (1997-08-01), None
Drenten Ronald R.
Spruit Johannes H. M.
Van Den Enden Gijsbert J.
Van Vlerken Johannes J. L. M.
Belk Michael E.
Dinh Tan
U.S. Philips Corporation
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