Method for controlling track jump in optical recording medium

Details Method for controlling track jump in optical recording medium Method for controlling track jump in optical recording medium

2000-07-21

2001-11-06

Edun, Muhammad (Department: 2651)

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

C369S044260

Reexamination Certificate

active

06314066

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rewritable optical recording medium, and more particularly, to a method for controlling track jump in an optical recording medium having land and groove tracks with depths different from each other in a direction of a beam.
2. Background of the Related Art
In general, an optical recording medium system, i.e., an optical disk recording/reproducing device is a device for reading a data recorded on an optical disk, such as CD (Compact Disk) or DVD(Digital Versatile Disc), or writing the data on the optical disk. Of the rewritable optical disk in the optical disk, there are CD-RW(Rewritable Compact Disc), and Rewritable Digital Versatile Discs(DVD—RW, DVD-RAM, DVD+RW). Particularly, the DVD-RAM has signal tracks of lands and grooves, to write or read data to/from tracks, not only of lands or grooves, but also tracks both of lands and grooves.
FIG. 1
illustrates a block diagram of a related art recording/reproducing device such a DVD-RAM, wherein, under the control of the servo controller
113
, an optical pickup
102
directs a beam focused by an objective lens onto the signal track of the optical disk
101
, or directs a beam, reflected at a signal recording surface and focused again by the objective lens, toward an optical detector for detecting a focus error signal and a tracking error signal. The optical detector has a plurality of optical detecting elements each for forwarding an electric signal proportional to an optical quantity of light incident thereto to a RF and servo error generator
103
. As shown in
FIG. 2
, if the optical detector has a particular number of divisions, i.e., four divisions in a signal track direction and in a radial direction of the optical disk
101
, four optical detecting elements PDA, PDB, PDC, and PDD, the optical detector forwards electrical signals ‘a’, ‘b’, ‘c’, and ‘d’ proportional to quantities of lights obtained at respective optical detecting elements PDA, PDB, PDC, and PDD to the RF and servo error generator
103
. The RF and servo error generator
103
combines the electrical signals ‘a’, ‘b’, ‘c’, and ‘d’, to produce a RF signal (or a read channel
1
signal) required for data reproduction, a read channel
2
signal required for servo control, and a focus error signal. The RF signal can be obtained by (a+b+c+d) of the electrical signals from the optical detector, the read channel
2
signal can be obtained by (a+d)−(b+c) of the electrical signals from the optical detector, and the tracking error TE signal can be obtained by processing the read channel
2
signal. If the optical detector has two division in the track direction, the RF signal (=I
1
+I
2
) and the read channel
2
signal (=I
1
-I
2
) can be detected from balances of quantities of lights. That is, ‘a’+‘d’ in
FIG. 2
corresponds to I
1
, and ‘b’+‘c’ corresponds to I
2
. In this instance, in a case of a rewritable disk
101
, it is impossible to control and write on the disk because the disk has no information. For this, by forming disk tracks on the lands and the grooves, writing information along the tracks, and writing control information on sector addresses, random accesses, and rotation control separately, the tracking control can be made even for an empty disk having no information signal recorded thereon. The control information may be written by pre-formatting a header region at beginning of every sector. In a case of the DVD-RAM, the head region pre-formatted at beginning of every sector is provided with four header fields(a header
1
field~header
4
field) again. The header
1
, and
2
fields and the header
3
and
4
fields are formed to alternate with reference to a track center, one example of which is illustrated in
FIG. 3
wherein a configuration of a header field for the first sector of one track is shown.
However, the header configuration affects generation of servo error signals, such as the tracking error signal, focus error signal actually. That is, the servo error signal read from the header region is distorted by the header configuration, control of which is difficult. Therefore, in the case of the DVD-RAM, in order to generate the servo signal and to make a stable control of it, the servo is controlled by holding respective error signals, for example, the tracking error TE signal and the focus error FE signal for reducing an influence from the header. That is, a focus sample & hold part
104
samples and holds the focus error FE signal and the tracking error TE signal at positions right forward of the header region. This is because, though the focus servo and the tracking servo operations are carried out even in the header, the servo operations are carried out, not by the tracking error signal and the focus error signal detected in the header region, but by the tracking error signal and the focus error signal held at the positions right forward of the header region. In this instance, the header region may be detected by different methods including known arts.
In the meantime, the tracking error signal on the land is an inversion of the tracking error signal in the groove. That is, since the tracking error signal detected from the land has a phase inverted from a phase of the tracking error signal detected from the groove, the phases of the tracking error signals both from the land and the groove should be made the same for making regular tracking on the land and groove. And, there is a difference of DC offsets the land and the groove basically have (i.e., a difference of amounts in terms of signals coming from a depth difference of the land and the groove). That is, even if the focusing and the tracking are right on the land track, if the focusing and the tracking are applied to the groove track as they are, a defocusing and a detracking may occur, and, opposite to this, even if the focusing and the tracking are right in the groove track, if the focusing and the tracking are applied to the land track as they are, the defocusing and the detracking may occur due to a difference of depth between the land and the groove. Therefore, an additional circuit for this is required, such as a focus groove offset part
105
, a focus land offset part
106
, a tacking groove offset part
109
, and a tracking land offset part
110
. The focus groove offset part
105
and the focus land offset part
106
adjust focus error offsets of the groove/land respectively for carrying out a regular focus servo. And, the tacking groove offset part
109
, the tracking land offset part
110
, and the invertor
111
adjust tracking errors for the groove/land respectively and inverts the tracking error signal detected from the land for carrying out regular tracking servo.
In this instance, L/G selecting part
107
or
112
selects the focus error signal and the inverted tracking error signal having offsets adjusted respectively to be consistent to the land at the land offset part
106
or
110
in response to an L/G switching signal L/Gsw, i.e., if the present signal track represents the land, or, the L/G selecting part
107
or
112
selects the focus error signal and the tracking error signal having offsets adjusted respectively to be consistent to the groove at the groove offset part
105
or
109
in response to an L/G switching signal L/Gsw, i.e., if the present signal track represents the groove, and forwards the selected focus error signal and the tracking error signal to the servo controller
113
. Accordingly, the servo controller
113
conducts the focus servo and the tracking servo either by using the focus error signal and the tracking error signal having offsets adjusted respectively to be consistent with the land through an F/T(Focus/Track) servo driver
114
, or by using the focus error signal and the tracking error signal having offsets adjusted respectively to be consistent with the groove through an F/T(Focus/Track) servo driver
114
, in response to the L/G switching signal L/Gsw. The L/G denotes a switch

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