Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Control of information signal processing channel
Reexamination Certificate
2000-03-29
2003-04-29
Tran, Thang V. (Department: 2653)
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Control of information signal processing channel
C369S124140, C369S059210
Reexamination Certificate
active
06556523
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a wobble-signal detecting device for detecting a wobble signal from a recording medium having a recordable information recording track which, or recordable information recording tracks, each of which wobbles at a predetermined frequency (this means that a track formed on the disc wobbles in such a manner that, when the rotation of the disc is ideally controlled, the wobbles occur for a pickup at the predetermined frequency, here and hereinafter) and pre-pits formed at predetermined intervals in areas between the information recording tracks, and, to an information recording apparatus such as a DVD-R drive, a recordable-optical-disc recording and reproducing apparatus or the like using the above-mentioned wobble-signal detecting device.
2. Description of the Related Art
In the related art, there is an optical recording medium having a wobbling groove and pits formed in areas between the grooves at predetermined intervals and a recording and reproducing apparatus for the optical recording medium (for example, see Japanese Laid-Open Patent Application No. 9-326138). In such an apparatus, it is possible to obtain address information and disc rotation control information precisely even with a narrow track pitch, and high-density recording is enabled.
Further, there is a recording-clock-signal generating device for a recording apparatus which records data based on a recording clock signal phase-locked to a wobble signal on an optical disc having a data recording track which wobbles in accordance with a wobble signal having a predetermined frequency component and pre-pits having a predetermined phase relationship with the wobble signal (for example, see Japanese Laid-Open Patent Application No. 10-293926).
In such an apparatus, the phase of the recording clock signal is adjusted using a phase adjusting signal generated as a result of the phase of the extracted wobble signal and the phase of the pre-pit detection signal being compared with one another, and it is possible to generate the recording clock signal precisely in synchronization with the disc rotation even when influence of cross talk due to the wobble signal of an adjacent groove track exists.
On a recordable optical disc, address information and a synchronization signal for rotation control and recording position control are previously recorded as a pre-format.
As one of the methods for recording such preformat information, there is a method in which, for example, a so-called CD-R has a groove (data recording track) wobbling at a predetermined frequency and address information is recorded as a result of the wobbles being frequency-modulated.
In order to extract the wobble signal, a socalled push-pull signal is caused to pass through a band pass filter (referred to as simply ‘BPS’, hereinafter), the central frequency of which is the above-mentioned predetermined frequency, and rotation control is performed so that the frequency of the thus-extracted wobble signal becomes the predetermined frequency.
As is well known, the push-pull signal is the difference (differential signal) between the outputs of two divisions of a light-receiving device, which two divisions are obtained as a result of the light-receiving device being divided by a line parallel to the direction of the tangent of the track at a target position, and receiving the light reflected by the disc.
Further, the wobble signal is used as a reference signal for generating the recording clock signal, and, thereby, it is possible to record data in synchronization with the rotation of the disc.
Japanese Laid-Open Patent Application No. 9-326138 proposes an optical disc having a wobbling groove and pits formed in areas (lands) between the grooves at predetermined intervals, and it is possible to precisely obtain address information and disc rotation control information even with a narrow track pitch.
This method is different from another method in which address information is arranged at the start of a sector. That is, in this method, no address pits exist in the groove which is the data recording track. As a result, high-density recording is enabled, recorded information is not divided by the address information, and superior interchangeability with a reproduction-only disc is provided.
Such an apparatus uses a method in which the wobble signal and pit signal are read out simultaneously using one beam spot using the push-pull method, and, similar to the case of CD-R, the wobble signal is extracted through BPF, is used for disc rotation control, and, also, is used as a reference signal for generating the recording clock signal. A DVD-R studied recently has a form similar to the above-described optical disc.
For example, for DVD-R, the track pitch is narrowed for performing high-density recording. Thereby, so-called cross talk from a groove adjacent to a groove on which an optical beam is incident cannot be ignored.
When cross talk from adjacent inner and outer grooves exists, the wobble signal is interfered with by wobble components of the adjacent grooves, and, as a result, fluctuates in the amplitude and/or phase thereof. In particular, when phase fluctuation occurs, it is not possible to generate the recording clock signal precisely in synchronization with rotation of the disc.
In order to solve this problem, a device such as that disclosed in Japanese Laid-Open Patent Application No. 10-293926 is proposed.
This is a recording-clock-signal generating device for a recording apparatus which records data based on the recording clock signal which is phase-locked to the wobble signal on an optical disc having the data recording track which wobbles in accordance with the wobble signal having the predetermined frequency component and pre-pits having the predetermined phase relationship with the wobble signal. In this device, the phase of the recording clock signal is adjusted using the phase adjusting signal generated as a result of the phase of the extracted wobble signal and the phase of the pre-pit detection signal being compared with one another.
Thereby, it is possible to generate the recording clock signal precisely in synchronization with the disc rotation even when influence of cross talk due to the wobble signal of an adjacent groove track exists.
Thus, the wobble signal is important for disc rotation control and generation of the recording clock signal, and, in particular, detection of the wobble signal having few jitters (phase fluctuation) is indispensable for providing with high accuracy the recording clock signal in synchronization with disc rotation.
However, there is a cause for fluctuations in the amplitude and/or phase of the wobble signal other than the influence of cross talk due to the wobble signal of an adjacent groove track.
That is, the push-pull signal detected by the push-pull method from a recording medium having a wobbling groove and pits formed in lands at predetermined intervals includes the wobble component and pre-pit components, as shown in FIG.
1
A. Then, when the wobble signal is extracted from this push-pull signal through a BPF, the central frequency of which is the wobble frequency, the signal including not only the wobble component but also the wobble-frequency component of the pre-pit components is extracted. This wobble-frequency component of the pre-pit components becomes the cause for fluctuations in the amplitude and/or phase of the wobble signal.
Normally, as shown in
FIG. 1A
, the pre-pit-signal components are larger than the wobble component, so the wobble-frequency component of the pre-pit components becomes larger as the amplitude of the pre-pit components becomes larger, and, thereby, the influence thereof to the wobble signal (wobble component+wobble-frequency component of the pre-pit components) cannot be ignored.
For example, for the DVD-R, pre-pits are formed in a land adjacent to and the outer side of a groove, and, in a land adjacent to and on the inner side, pre-pits for the immediately inner groove are formed.
The
Dickstein , Shapiro, Morin & Oshinsky, LLP
Le Kimlien
Ricoh & Company, Ltd.
Tran Thang V.
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