Dynamic information storage or retrieval – Binary pulse train information signal – Binary signal level detecting using a reference signal
Reexamination Certificate
2000-05-25
2003-09-02
Edun, Muhammad (Department: 2655)
Dynamic information storage or retrieval
Binary pulse train information signal
Binary signal level detecting using a reference signal
C369S174000, C369S059100
Reexamination Certificate
active
06614740
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical recording medium, and more particularly, to device and method for detecting a non-writable region of an optical recording medium.
2. Background of the Related Art
In general, in optical recording media which permit repeated rewriting without restriction, such as optical disks, there are Rewritable Compact Disc(CD-RW), Rewritable Digital Versatile Disc(DVD-RW, DVD-RAM, DVD+RW), and the like. The rewritable optical recording medium, particularly, the DVD-RAM is provided with a signal track having a land and a groove, and information is recorded on the land and the groove for increasing a recording density, respectively. And, for this, an optical pickup is provided with a writing/reading laser beam with a short wavelength, and an objective lens provided for collecting lights has a great numerical aperture for making the writing/reading laser beam smaller.
FIG. 1
illustrates a block diagram of a related art rewritable optical disk recording/reproducing device. The optical disk
101
has a land and a groove, for recording data on, and reading data from both of them.
An optical pickup
102
causes a beam collected by an objective lens to be focused onto a signal track of the optical disk
101
under the control of a servo controller
107
, and directs a beam, reflected at a signal recording surface and collected by the objective lens, to an optical detector for detecting a focus error signal and a tracking error signal. The optical detector has a plurality of optical detecting elements, for providing an electrical signal proportional to an amount of light obtained from each optical element to a RF and servo error generator
105
. As shown in
FIG. 2
, if the optical detector is divided into a specific number, i.e. four, in a signal track direction and a radial direction to have four optical detecting elements PDA, PDB, PDC, and PDD, the optical detector provides electrical signals a, b, c, d each proportional to an amount of light obtained in respective optical detecting elements PDA, PDB, PDC, and PDD to the RF and servo error generator
105
. Then, the RF and servo error generator
105
combines the electrical signals a, b, c, and d to produce a read channel
1
signal required for data reading, a read channel
2
signal required for servo control, and a focus error signal FE, and the like. The read channel
1
signal is obtained by a+b+c+d, the read channel
2
signal is obtained by (a+b)−(c+d), and the tracking error signal TE is obtained by processing the read channel
2
signal. If it is a case when the optical detector is divided into two in the track direction, from a light amount balance of the two photodiodes I
1
and I
2
, the read channel
1
signal(=I
1
+I
2
), and the read channel
2
signal(=I
1
−I
2
) is detected. That is, the (a+d) in
FIG. 2
corresponds to
11
, and the (b+c) in
FIG. 2
corresponds to I
2
. The read channel
1
signal is provided to a data decoder
106
for reading, servo error signals, such as FE and TE, are provided to the servo controller
107
, and a control signal for data writing is provided to an encoder
103
. The encoder
103
encodes a data to be written into a writing pulse of a format required by the optical disk
101
and provides to an LD driver
104
, and the LD driver
104
drives an LD in the optical pickup
102
in a power corresponding to the writing pulse, thereby writing the data on the optical disk
101
. And, in reading the data written on the optical disk
101
, the data decoder
106
restores an original form of the data from the read channel
1
signal detected form the RF and servo error generator
105
. And, the servo controller
107
processes a focus error signal FE to provide a driving signal for focusing control to a focus servo driver
108
, and processes a tracking error TE signal, to provide a driving signal for tracking control to a tracking servo driver
109
. In this instance, the focus servo driver
108
drives the focus actuator in the optical pickup
102
to move the optical pickup
102
in up and down direction to follow the up and down movement of the optical disk
101
as the optical disk
101
is rotated. That is, the focus actuator for driving the objective lens, which collects lights, in a focusing axis maintains a distance between the objective lens and the optical disk
101
in response to a focus control signal. And, the tracking servo driver
109
drives a tracking actuator in the optical pickup
102
, to shift the objective lens in the optical pickup
102
in a radial direction, for correcting a position of beam to follow the track.
In the meantime, in a case of the rewritable disk
101
, as there is no information recorded on an initial disk, controlling and writing the disk is not possible. For this, disk tracks are provided to the land and the groove, information is written along the tracks, and control information for sector addresses, random access, rotation control and the like is written on the disk separately, to make tracking control available even for an empty disk having no information signal written thereon. The control information may be written in a header region by preformatting a header region at beginning of every sector. The header region pre-formatted at beginning of each sector is, in turn, provided with four header fields(header
1
field~header
4
field). And, the header
1
and
2
fields and the header
3
and
4
fields are arranged to alternate the other with reference to the track center.
FIG. 3
illustrates one example, wherein a header field structure for a first sector on one track is shown. However, the foregoing header structure has a bad influence in producing the servo error signal, such as a tracking error signal, and a focus error signal, actually. That is, the servo error signal read from the header region is distorted depending on a header structure, and is difficult to control. Therefore, in a case of DVD-RAM, in for generating, and making a stable control of a servo error, the servo error signal is held in controlling a servo in the header region for reducing an influence from the header. To do this, a method for identifying a header region is required, for which the read channel
2
signal is used in the related art.
That is,
FIG. 4
illustrates a related art block diagram for detecting a header region, including an LPF(Low Pass Filter)
201
for receiving the read channel
2
signal and making low pass filtering, a first comparator
202
for providing an IP
1
signal if the low pass filtered read channel
2
signal is higher than a preset slice level, a second comparator
203
for providing an IP
2
signal if the low pass filtered read channel
2
signal is lower than the preset slice level, and a signal generator
204
for generating a header mask signal which represents a header region by using the IP
1
and IP
2
signal from the first and second comparators
202
and
203
.
In the foregoing
FIG. 4
, the LPF
201
receives the read channel
2
signal from the RF and servo error generator
105
, subjects to low pass filtering to produce a tracking error signal TE, and provides to the first and second comparators
202
and
203
. As the header region, i.e., the header
1
,
2
fields and the header
3
,
4
fields are alternates with reference to a track center, the read channel
2
signal detected at the header
1
,
2
fields and the header
3
,
4
fields have phases(i.e., slopes) opposite to each other as shown in FIG.
5
A. If such a read channel
2
signal in the header region passes through the LPF
201
, the read channel
2
signal becomes a tracking error signal TE from which a noise is removed, as shown in FIG.
5
. In this instance, as shown in
FIG. 5C
, if the tracking error signal TE provided to a plus terminal is higher than a slice level provided to a minus terminal, the first comparator
202
provides an IP
1
signal, and, as shown in
FIG. 5D
, if the tracking erro
Kim Eung Soo
Park Sang On
Park You Jae
Edun Muhammad
LG Electronics Inc.
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